Chapter 5b – Clinical Anaesthesia Answers


Clinical Anaesthesia Answers

Chapter 5b Clinical Anaesthesia Answers

Question 1: FFFTF

Malignant hyperthermia (MH) is a rare autosomal dominant condition. If this patient’s biological father had MH his risk is likely to be 50%. The responsible gene mutation is on chromosome 19 in the majority of patients, resulting in three abnormal isoforms of the ryanodine receptors in muscle (plasma cholinesterase is coded for on chromosome 3). Up to 15 relevant mutations at chromosome 19 have been identified and point mutations may occur, resulting in cases with no relevant family history. The abnormality results in an abnormal ryanodine calcium channel in muscle that allows excessive calcium to move from the endoplasmic reticulum into the cytoplasm, with uncontrolled muscle contraction. Dantrolene is used to treat MH by uncoupling the excitation contraction process and blocking the ryanodine calcium channel. MH may develop after exposure to triggering agents, with some reports up to 12 hours post exposure, and can occur after previous uneventful general anaesthetics.

Question 2: TTFFT

In children a cuffed tube is not always used, in order to prevent tracheal stenosis; an uncuffed tube can provide a secure airway due to the anatomical variation in children. A method of detecting CO2 will confirm placement, but continuous capnography is not the only available method; in prehospital practice a colorimetric device is used.

Question 3: TFFFT

The Third National Audit Project of the Royal College of Anaesthetists (NAP3) investigated the major complications following central neuraxial block. Staphylococcus aureus was found to be the most common organism associated with epidural abscesses. The majority of complications following perioperative central neuraxial block (CNB) occurred with epidurals. Vertebral canal haematoma commonly presents with symptoms of leg weakness. In NAP3 weak legs were a universal symptom in cases of vertebral canal haematoma, but back pain was rare. The incidence of permanent injury after adult perioperative epidural was 8.2–17.4 per 100 000. The incidence of paraplegia and death following CNB was found to be 0.7–1.8 per 100 000.

Question 4: FTTFT

Cyanotic heart disease is a group of illnesses in which the deoxygenated blood travels to the systemic circulation without entering the pulmonary circulation (right to left shunt). In coarctation of the aorta there is no alteration of the normal flow but rather stenosis in the descending thoracic aorta. Tetralogy of Fallot is characterized by right ventricular outflow obstruction, VSD, aortic root over-riding a high VSD and RV hypertrophy. Thus the blood is shunted from the right ventricle to the aorta. After birth the pulmonary vascular resistance (PVR) drops below the SVR making any shunt through ASD or VSD almost always a left to right shunt. Only when complicated with severe pulmonary hypertension (Eisenmenger’s syndrome) does the reversal of shunt occur leading to cyanosis in conditions with isolated septal defects.

Question 5: TFFTT

One metabolic equivalent (MET) is equivalent to 3.5–1.min–1 oxygen consumption and represents the oxygen consumption of an adult at rest. Patients should be able to perform more than 4 METS to undertake major surgery, which correlates clinically to being able to climb at least one flight of stairs. MET values of activities range from 0.9 (sleeping) to 23 (running at 22.5 km.h–1).

Question 6: FFFFF

Myasthenic syndrome is a diagnosis related to myasthenia gravis (MG), also known as Eaton–Lambert syndrome. There are some important features of myasthenic syndrome distinguishing it from MG. There is decreased release of acetylcholine from the presynaptic nerve terminal, as opposed to IgG autoantibodies directed at the postsynaptic acetylcholine receptor seen in MG. Muscle weakness in myasthenic syndrome predominantly affects the proximal muscles, as opposed to the generalized pattern often with ocular and bulbar muscle involvement seen in MG. Weakness in MG is typically worse on exertion and improves with rest and the opposite pattern is true in myasthenic syndrome, with electromyography showing an increase in power on titanic stimulation. Patients with myasthenic syndrome show an increased sensitivity to both depolarizing and non-depolarizing muscle relaxants. In MG there is increased sensitivity to non-depolarizing muscle relaxants, but a relative resistance to suxamethonium, with up to twice the normal dose being required. Acetylcholinesterase inhibitors (such as neostigmine and more commonly pydridostigmine) are a mainstay in the pharmacological treatment of MG, but result only in slight improvement in muscle weakness in myasthenic syndrome. Other features of myasthenic syndrome not seen in MG include autonomic system disturbance and the depression or absence of tendon reflexes.

Question 7: TTTFF

Postherpetic neuralgia (PHN) is the term used to describe the painful aftermath of herpes zoster (HZ) infection, also known as shingles. The diagnosis is given to patients who still have pain three months or more following HZ. It is the reactivation of varicella zoster virus (VZV) that gives rise to HZ and it remains in a latent state in spinal and cranial sensory ganglia until reactivation. Although most people are immune due to childhood vaccination or exposure to wild-type virus, immunity may be decreased – by disease or immune suppression – and reactivation occur.

Risk factors include:

  • Older age (it is rare below 50 years)

  • Female sex

  • Acute pain and rash severity

  • Dermatomal pain before rash appears

Most patients experience a painful vesicular eruption in a single dermatome that settles within three months. However, approximately 20% will develop PHN. The pain is intense and described as burning, throbbing, stabbing or shooting. It can be continuous or intermittent, and patients often experience allodynia and hypersensitivity. The pain can be very debilitating and lead to depression and social isolation.

Question 8: TFFFF

Some measures that are part of good intensive care practice also apply to the management of the potential heart-beating donor, but there are additional measures shown to increase the viability and number of transplantable organs.

Endocrine dysfunction following brainstem death can contribute to organ failure and hence hormone replacement may help preserve homeostasis. The hormones commonly replaced are insulin, methylprednisolone and triiodothyronine. The rationale for using these hormones is: insulin for treating hyperglycaemia, methylprednisolone to counter the cytokine-driven inflammatory response and thyroid hormones to improve the function of transplanted hearts in the recipient.

Donor lungs are susceptible to fluid overload and so considerations may include the measurement of left-sided filling pressures and avoiding a CVP of >6 mmHg (without PEEP), which may worsen the alveolar–arterial oxygen gradient. The use of lung protective ventilation, including a positive end expiratory pressure of 5–10 cmH2O, can be effective in treating pulmonary oedema and preventing alveolar collapse.

Hypotension is initially managed with volume loading because potential donors often are often relatively vasodilated, but where vasopressor support is required vasopressin is the first-line agent. In septic patients doses of vasopressin >2.5 U.h−1 are associated with adverse outcomes, including cardiac arrest.

Question 9: FFTTF

The Rule of Nines is a quick method used to estimate medium to large-sized burns in adults (it is not accurate in children). The body is divided into areas of 9% TBSA (see Table 5.9.1).

Table 5.9.1

Head (front and back) = 9%
Anterior chest = 18%
Back = 18%
Each arm = 9%
Each leg = 18%
Perineum = 1%

For small burns (generally < 5% TBSA) the palmer surface method can be used.

In this method the surface of the patient’s palm, including the fingers, is estimated to be approximately 0.8–1% of TBSA and can be used to estimate the burn area.

Question 10: TFFTF

Bariatric surgery has been sanctioned by NICE as a recommended treatment for obesity, and has been shown to cause a maintainable reduction in weight of more than 50% in some cases. Laparoscopic techniques have a lower morbidity and mortality in the short term; this is thought to be due to differences in wound healing and postoperative pain causing problems with respiratory function. According to studies by Brodsky et al., raised BMI in isolation is not an indicator of difficult intubation, but raised BMI with other signs such as a Mallampati score of >3 is an indication of a potentially difficult airway. The incidence of OSA in obese patients is approximately 5%, but a history of daytime somnolence, apnoeic periods or snoring should be sought, as preoperative CPAP/BiPAP may be helpful. Due to excess limb weight and positioning, nerve injuries are more common in the obese. Suxamethonium dose should be based upon actual body weight due to increased plasma cholinesterase activity.

Question 11: TTTFF

RCOA guidelines require a number of features specific to paediatric day surgery. A PICU on site is not essential unless infants with chronic lung disease are undergoing surgery. Ex-premature neonates should not undergo day-case anaesthesia unless over 60 weeks post conception and medically fit. Play specialists are not obligatory, but suitable paediatric facilities must be available.

Question 12: FTFTT

There are several bedside tests that may predict difficult intubation:

  • The inability to protrude the mandibular incisors

  • A sternomental distance less than 12 cm

  • A thyromental distance less than 6 cm

  • Mallampati score 3 or 4

  • The presence of buck teeth

  • Limited ability to extend the neck

Previous radiotherapy to the head and neck can cause formation of fibrotic tissue and reduced mobility of tissues, causing difficulty at intubation. Previous tracheostomy formation or prolonged intubation may result in scarring and tracheal stenosis.

The presence of numerous congenital syndromes, including Pierre Robin, Treacher Collins and Goldenhar syndrome, plus mucopolysaccharide disorders such as Hurler’s and Hunter’s syndromes, are associated with difficult intubation. The presence of a high-arched palate is seen in Marfan’s and Down’s syndromes and may complicate intubation.

Question 13: TFFTF

Thoracic paravertebral blocks provide an ipsilateral somatic and sympathetic nerve block similar to a unilateral epidural block, especially useful for breast surgery, thoracotomy, in patients with rib fractures or open cholecystectomy. The thoracic paravertebral space is a wedge-shaped area that lies on either side of the vertebral column defined by:

  • Parietal pleura anterolaterally

  • The vertebral body, intervertebral disc and intervertebral foramen medially

  • The superior costotransverse ligament posteriorly

The space is continuous with the intercostal space laterally, epidural space medially and contralateral paravertebral space via the prevertebral fascia. As the nerves emerge from intervertebral foramina, they transverse through the paravertebral space where they may be blocked by local anaesthetics, thereby blocking dorsal and ventral rami and hence the sympathetic chain.

The block can be inserted with ultrasound guidance, but more commonly is performed using a landmark technique. C7 is the most prominent cervical spinous process, whilst the lower tip of the scapula lines up with T7.

Complications of paravertebral blocks include infection, haematoma, local anaesthetic toxicity, nerve injury and, rarely, total spinal anaesthesia and paravertebral muscle pain (resembling muscle spasm mainly in young muscular men, especially when larger gauge Tuohy needles are used).

Question 14: FFTTF

There is no good evidence to support one inotrope over another in cardiogenic shock. Dobutamine is used frequently, not only because of its positive inotropic effect, but also as a peripheral vasodilator, reducing the afterload against a failing heart. In this case the BP is significantly low and will be made worse by dobutamine. Adrenaline is a potent vasopressor through its action on the α1-receptor, which will support the SVR in this situation. In diastolic dysfunction the cardiac output is dependent on venous return and filling pressure, which will be reduced by dobutamine due to vasodilatation. IABP can be quite helpful in patients with ischaemic cardiogenic shock who are expected to be on multiple inotropes. It will improve the coronary perfusion during diastole and reduce the afterload during systole. Noradrenaline is not routinely used as a first-line agent in these cases. Raised lactate in this case is due to pump failure that is unlikely to be helped by noradrenaline. However, it can be added later on if the low BP proved to be resistant to either adrenaline or dopamine as a single agent.

Question 15: TFFTT

Acute fatty liver of pregnancy is a serious condition affecting approximately 5 in every 100 000 pregnancies and has a significant maternal mortality and morbidity. The maternal mortality rate is now in the region of 10–20%, having been over 85% when the disease was first identified. It often presents later in pregnancy (after 30 weeks). Common signs and symptoms include jaundice, abdominal pain, altered mental state, nausea and acute renal impairment. The features of pre-eclampsia are present in a significant proportion of patients and it can be difficult to differentiate clinically and biochemically from HELLP syndrome. There is a higher incidence of AFLP in first pregnancies, multiple pregnancies and when the fetus is male (3:1 M:F). Radiological appearances can be normal and liver biopsy remains the gold standard test; it is, however, often contraindicated due to an underlying coagulopathy. There are risks and benefits of both general and regional anaesthesia and both have been used safely, provided none of the usual contraindications are present.

Question 16: FFTTF

CPET is a very useful test in assessing patients for lung resection. It is not needed for all patients. In those patients with poor predicted lung function as well as unexplained poor functional capacity it is indicated. If the peak VO2 is above 20–1.min–1 they can usually have resection up to pneumonectomy . The ability to climb two flights correlates with a VO2 max of approximately 12–1.min–1. The anaerobic threshold is approximately 55% of VO2 max in untrained individuals but rises to >80% in trained athletes.

Question 17: FTTFT

Sickle cell disease is an inherited haemoglobinopathy resulting from a mutation on chromosome 11. The mutation causes a pathological amino-acid substitution of valine for glutamic acid on the β-globin chain of haemoglobin A. This substitution produces haemoglobin S, which is inherently unstable and can adopt the notorious ‘sickle’ appearance under certain conditions. The Sickledex® test is a sickle solubility test and is used in emergency situations as a rapid screening test. It detects haemoglobin S levels greater then 10%, but is unable to differentiate between homozygous (sickle cell disease) and heterozygous (sickle cell trait) conditions. Haemoglobin electrophoresis is the definite distinguishing test. Sickle cell trait has been shown in numerous studies to confer strong protection against Plasmodium falciparum malaria. The protective mechanisms are not fully understood. However, proposed mechanisms include a reduction in parasite growth and enhanced removal of parasitized cells through acquired or innate immune systems.

Question 18: FTFTT

The tongue is large and the larynx is situated more anteriorly and cephalad (C3–C4). The epiglottis is large and U-shaped. The cricoid cartilage is the narrowest part of the upper airway and a small decrease in diameter caused by oedema or stricture formation following prolonged tracheal intubation may lead to airway obstruction.

Tidal volume is fixed and ventilatory frequency needs to be increased to increase minute ventilation. Ventilation is mainly diaphragmatic and there are fewer type I muscle fibres, so infants fatigue earlier. FRC is less than the closing capacity owing to the low elastic recoil of the chest wall. This, along with the high metabolic requirement, predisposes them to hypoxia.

Question 19: FFTFF

Recognition of malignant hyperpyrexia (MH) is key: the AAGBI guidance from 2011 suggests unexplained increase in heart rate and end tidal CO2, alongside increased oxygen requirement, and possibly late-onset temperature rises, should prompt recognition of MH.

Volatile anaesthesia should be discontinued and anaesthesia maintained via intravenous agents. The patient should be ventilated with 100% oxygen via a clean circuit and preferably via a dedicated anaesthetic machine that has not been in contact with volatile anaesthetic agents. While hyperventilation may help control respiratory acidosis, it alone is not adequate management. Close liaison with the surgical team is vital – explain that there is an anaesthetic emergency and that completion of surgery should be expedited, or, if feasible, surgery abandoned. In this case, conversion to an open procedure may be warranted depending on surgical experience/expertise. The recommended bolus dose is now 2.5–1 of dantrolene with further 1–1 boluses up to 10–1 . Active cooling measures need to be taken, but using ice is likely to cause peripheral vasoconstriction that is counterproductive and should be avoided.

Question 20: TTFTT

Risk factors can be split into a number of categories:

  • Delayed gastric emptying (pain, trauma, opioids, alcohol)

  • Medical conditions (GORD, hiatus hernia, diabetic neuropathy, neurological/neuromuscular disease)

  • Acute illness (bowel obstruction/ileus, metabolic derangement, impaired consciousness)

Question 21: TFTFF

In 2015/16, 33% of renal transplants in the UK were from living donors. Under UK guidelines both a consultant surgeon and consultant anaesthetist should be present during the donor nephrectomy. As long as the renal function tests and urine production are normal, hypertension is not a contraindication to being a living donor. Diabetes mellitus is a contraindication to donating, but those with impaired glucose tolerance may be considered if fasting glucose is <7.0 mmol.l–1, oral glucose tolerance test is <7.8 mmol.l–1 and BMI is <30 with no family history of diabetes. As a nephrectomy is considered a clean procedure, routine antibiotic prophylaxis is not required. Unless there are specific patient concerns, routine use of invasive monitoring is not necessary.

Question 22: FTFTF

During intrauterine life, the passage of deoxygenated blood from the pulmonary artery through the ductus arteriosus (DA) into the aorta stimulates release of prostaglandin E2 (PG E2). This in turn helps to keep the DA patent. At birth, with the first breath, the flow reverses, with oxygenated blood passing from the aorta to the pulmonary artery due to changes in pressure in both circulations. This will lead to closure of the DA.

In conditions where the deoxygenated blood bypasses the pulmonary circulation, such as tetralogy of Fallot, transposition of the great arteries and pulmonary stenosis, keeping the DA patent is very useful to allow the blood flow to the pulmonary circulation to improve oxygenation.

Question 23: FTFTF

A 1% solution contains 10–1 of the substrate.

The safe dose of lignocaine is 3–1 plain and 7–1 with adrenaline.

The safe dose for bupivacaine/levobupivacaine is 2–1 (max of 150 mg) regardless of whether adrenaline is in the mixture.

Prilocaine is safe at 6–1 and 9–1 with adrenaline.

A 10 ml dose of prilocaine 2% contains 200 mg, which is within the safe dose for a 60 kg patient. However, it will be inappropriate for this operation as the spinal will be unnecessarily high and the duration of action will be very short for the procedure mentioned.

The use of adrenaline is contraindicated near end arteries, e.g. ring blocks or penile blocks.

Question 24: TTFTT

Intraoperative neurophysiological monitoring is commonly used to test the integrity of spinal cord functions in scoliosis surgery. Somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs) monitor the response of the spinal cord distally in response to a stimulus applied proximally. SSEPs are applied at a peripheral nerve and detected using epidural or scalp electrodes. MEPs are applied using scalp electrodes to the motor cortex and subsequently detected using epidural electrodes or compound muscle action potentials (CMAPs). To negate background noise, multiple signals applied over 2–3 minutes are averaged.

Neuromuscular blocking drugs prevent CMAPs, but may help reduce background noise when detecting SSEPs. SSEPs and MEPs are depressed by volatile agents, nitrous oxide and propofol, but opioids have little effect. To identify neurological injury, as opposed to drug-induced changes in SSEPs and MEPs, it is important to achieve steady state anaesthesia with minimal changes in the drugs administered after induction. Changes in physiological parameters such as reductions in blood pressure and temperature may also depress signals. If changes thought to be due to neurological injury are detected (reduced amplitude, increased latency or loss of waveform), a ‘wake-up test’ to clinically assess the integrity of the relevant pathways is necessary.

Question 25: FTTTF

Overall estimated incidence of awareness under general anaesthesia is 1:19 000. This varies in different settings: with neuromuscular blockade (NMB), the incidence increases to 1:8000 and without NMB it is 1:136 000. The main risk factors identified are:

  • Drug factors: neuromuscular blockade, thiopental, total intravenous anaesthesia techniques

  • Patient factors: female gender, age (younger adults, but not children), obesity, previous accidental awareness under general anaesthesia and possibly difficult airway management

  • Subspecialties: obstetric, cardiac, thoracic, neurosurgical

  • Organizational factors: emergencies, out of hours operating, junior anaesthetists

ASA grade, physical status, race and use of nitrous oxide are not risk factors for accidental awareness under general anaesthesia.

Question 26: FFFTF

Guillain–Barré syndrome (GBS) is an acute demyelinating polyneuropathy characterized by ascending motor weakness preferentially affecting the proximal skeletal muscles. GBS is often preceded by limb paraesthesia, back pain and in more than half of patients a bacterial or viral illness, commonly a gastrointestinal or respiratory tract infection. The commonest responsible pathogen is Campylobacter jejuni, but others that have been implicated include Epstein–Barr virus, Mycoplasma pneumoniae and cytomegalovirus.

Autonomic disturbance is common in GBS and this may manifest at any stage as arrhythmias, wide fluctuations in blood pressure and pulse, urinary retention, ileus and excessive sweating. A quarter of patients with GBS will require ventilatory support. A vital capacity of <20–1 is an indication for intubation and ventilation; other indications include maximal inspiratory pressure of <30 cmH2O, maximal expiratory pressure of <40 cmH2O or a decrease in any of these three parameters by >30%.

Treatment modalities include those that are supportive therapies, e.g. ventilatory support and physiotherapy, as well as specific therapies to reduce the inflammatory process, e.g. corticosteroids, intravenous immunoglobulin and plasmapheresis, which may reduce the severity and duration of the illness.

Question 27: FFFTF

The underlying pathophysiology in acromegaly is the hypersecretion of growth hormone from the anterior pituitary gland. Patients with acromegaly may present with a number of systemic manifestations that are of concern to anaesthetists, including changes to the airway, respiratory and cardiovascular systems, some of which are detailed here.

Macrognathia, macroglossia and excess soft tissue may make laryngoscopy and tracheal intubation more difficult. Soft tissue enlargement of the upper airway results in up to 70% of patients having significant obstructive sleep apnoea. Soft tissue overgrowth peripherally results in an increased risk of nerve entrapment syndromes necessitating meticulous attention to patient positioning.

Cardiovascular changes in acromegaly can include refractory hypertension with left ventricular hypertrophy, ischaemic heart disease, arrhythmias, heart block, cardiomyopathy, and biventricular dysfunction. The onset of acromegaly is typically insidious, with patients often presenting in middle age with advanced features.

The hypersecretion of other anterior pituitary hormones can occur alongside acromegaly or as part of other conditions, one of which is Cushing’s disease, attributed to the hypersecretion of ACTH from a pituitary corticotroph adenoma. Physical features associated specifically with Cushing’s disease include exophthalmos secondary to retro-orbital fat deposits, as well as cervical/supraclavicular fat pads making central venous cannulation more difficult.

Question 28: FTFFT

Myotonic dystrophy is an autosomal dominant disease and the most common of the dystonias, the others being myotonia congenita and paramyotonia. It has an incidence of approximately 1 in 20 000, typically presenting in the second or third decade of life with death occurring in the fifth or sixth decade.

Stimulation of skeletal muscle is followed by persistent contraction, disease progression is characterized by progressive muscle atrophy (skeletal, cardiac and smooth). The other important systemic manifestations include cardiorespiratory complications some of which are discussed here, but also CNS and endocrine dysfunction. Bulbar palsy increases the risk of aspiration, and respiratory deterioration can occur due to progressive depression of central respiratory drive, as well as weakness of the respiratory musculature. Cardiovascular complications include cardiomyopathy, atrioventricular block, arrhythmias and mitral valve prolapse (occurs in 20% of patients).

Factors in the conduct of anaesthesia can trigger persistent muscle contraction; potential triggers include the use of suxamethonium, reversal with neostigmine and hypothermia. Regional anaesthesia does not prevent muscle contraction, but local anaesthetic injected directly into muscles may help. Other strategies to avoid troublesome spasms that have been effective in some cases include the use of IV quinine and a slow bolus of IV phenytoin (3–5–1 ).

Question 29: FTFTF

Cerebral palsy (CP) is a group of neurological disorders characterized by varying degrees of motor, sensory and intellectual impairment. CP is the most common cause (60%) of motor impairment in childhood. Two-thirds of patients will have some degree of impaired intellectual and cognitive function. Up to 50% of patients have either focal or generalized forms of epilepsy. There is an increased risk of aspiration pneumonitis and consequently chronic lung scarring because of swallowing difficulties, oesophageal dysmotility, abnormal lower oesophageal sphincter tone and spinal deformity, which lead to gastro-oesophageal reflux. In the long term, truncal muscle spasticity can lead to scoliosis, restrictive lung defects, pulmonary hypertension, and ultimately cor pulmonale and respiratory failure. Succinylcholine is not contraindicated in patients with CP. Non-depolarizing neuromuscular blocking agents are less potent and have a shorter duration of action in patients with CP owing to the upregulation of ACh receptors. Many anaesthetists choose to perform a rapid sequence induction to secure the airway in patients with reflux, but there is no evidence to suggest that this is any safer than a gas induction with the patient inclined at a 20–30° head-up tilt. A gas induction is often the only option in the ‘veinless’ uncooperative patient.

Question 30: TFFTF

The dose requirement for induction agents is reduced in the elderly. A contracted blood volume coupled with reduced protein binding lead to a higher free-drug concentration. Prolongation of arm–brain circulation time dictates that induction agents should be administered more slowly. Failure to do this leads to inadvertent overdose, often with marked cardiorespiratory side effects. Virtually all opioids, IV agents and benzodiazepines exhibit an age-related increase in their elimination half-life, resulting in a prolonged duration of action. This is attributable to an increased volume of distribution for lipophilic drugs because of the increase in body lipid content in the elderly, and a reduction in organ-based elimination. The MAC value of all inhalational anaesthetic agents is reduced by 20–40% from young adult values. Although ageing is associated with a reduction in muscle mass, the development of extrajunctional cholinergic receptors offsets the reduction in the expected dosage of neuromuscular blocking agents required to produce acceptable intubating conditions. However, the time of onset and the duration of action are both prolonged because of a reduction in cardiac output and reduced metabolism. Ageing is associated with a reduction in the carotid baroreceptor response to a fall in blood pressure. Both IV and inhalational anaesthetic agents further impair this response, and also depress cardiac and vascular smooth muscle contractility. The choice of inhalational anaesthetic has no influence on the risk of POCD, but it has been suggested that propofol via TIVA may be associated with a lower incidence.

Question 31: TFTFT

It is important to select the appropriate probe for the particular scan required. Probes vary in their:

  • Operating frequency range – the higher the frequency, the better the discrimination of fine detail, but the lower the penetration

  • Physical size

  • Width of scanned tissue field – dependent on size of the probe

Linear probes have a flat face and give a parallel-sided scan field approximately 1 mm thick. They generally operate at frequencies between 5 and 18 MHz.

Hockey-stick probes are smaller and often used in paediatrics.

Curvilinear probes have a curved face giving a fan-shaped scan field. They operate at lower frequencies, typically 2–5 MHz.

Gain control adjusts brightness. More sophisticated machines employ time gain compensation.

Question 32: FTFFF

Migraine is more likely to affect females and commonly presents in the second or third decade. It is can occur with (30%) or without (70%) aura. It has a throbbing, pulsating quality and can be associated with nausea, vomiting, fatigue, confusion, photophobia and phonophobia. It is not commonly associated with focal neurological abnormality.

Acute treatment includes simple oral analgesics, plus antiemetics or rectal diclofenac. The triptans are also used in the acute management, whereas pizotifen is used in the prophylactic management of migraine. Generally, opioids are not considered useful for migraine.

In this case the patient is presenting with sudden onset headache with focal neurology and so neuroimaging should be considered, despite her history of migraine.

Question 33: TTTTT

Many different patient positions are utilized in neurosurgery, including all of those mentioned in the question. In the majority of patients, pressure- and positioning-related injuries are avoidable if due diligence is taken in patient positioning.

Damage to the common peroneal nerve (a branch of the sciatic nerve) can occur in the lateral position, resulting in foot drop. This nerve is particularly vulnerable because of its superficial course as it wraps laterally around the fibular head.

In the prone position the upper limbs are slightly flexed, then abducted and externally rotated; this should be done simultaneously in both arms. The brachial plexus is at risk in this position and particular care should be taken to ensure that chest supports do not impinge on the axilla.

Venous air embolism is a well-recognized complication of the sitting position, the pathophysiology of which relates to the potential for air entrainment into dural venous sinuses that are relatively non-collapsible.

The lateral position carries the highest risk of ocular complications in both the dependent and non-dependent eye, the most of common of which is corneal abrasion. A head ring or horseshoe headrest if malpositioned can result in direct pressure on the globe, causing ischaemic optic neuropathy.

Question 34: FTFTT

The Lund–Browder chart is an accurate tool commonly used to measure percentage burns in children and adults (Table 5.34.1). As opposed to the Rule of Nines, the Lund–Browder chart compensates for the changes in body proportions in the head, thighs and legs that occur with age, the head (front and back) making up 17% of total body surface area (TBSA) in a one-year-old child compared with only 7% in an adult. It has been noted that the Lund–Browder chart does not take into account obesity, breast size, pregnancy status and amputated body parts, all of which may affect the calculated body surface area.

Table 5.34.1 The Lund–Browder chart

Area Age 0 1 5 10 15 Adult
Half of head 9.5 8.5 6.5 5.5 4.5 3.5
Half of one thigh 2.75 3.25 4 4.5 4.5 4.75
Half of one lower leg 2.5 2.5 2.75 3 3.25 3.5

The neck (1%), perineum (1%), arms (10% each), torso (13% each side), buttocks (2.5% each) and feet (3.5% each) are the same %TBSA, regardless of age.

Question 35: FTTFF

Laparoscopy involves the insufflation of the peritoneum with CO2. This gas is chosen because it is more blood soluble than nitrogen, so it is less likely to cause air embolism, as it is rapidly absorbed if inadvertent intravascular injection takes place. The diaphragmatic irritation causes irritation of the phrenic nerve (roots C3–C5), which have a shoulder dermatomal distribution. Raised ICP (caused by either intracranial neoplasm, head trauma or hydrocephalus), hypovolaemia and severe valvular or ischaemic heart disease are all relative contraindications to laparoscopy. Insufflation pressures are typically up to 20 mmHg, as above this point the physiological responses to pneumoperitoneum can cause a severe fall in cardiac output leading to cardiac arrest. There are some reports of laparoscopy being combined with epidural or spinal anaesthesia, however a block to T4 is required and this does not obliterate the referred diaphragmatic pain.

Question 36: FTTTF

Metformin can be continued for surgery (except where contrast media are given in the context of low glomerular filtration rate). Morning doses of sulfonylureas should be omitted for both am and pm lists. GLP1 analogues and gliptins should be paused for the day of surgery.

Question 37: TTTFF

Tuberculous meningitis is associated with turbid or opalescent CSF, very high protein (>2 g.l–1), low glucose and lymphocytes. Mumps meningitis may be associated with low glucose in 20% of cases. Partially treated bacterial meningitis may be associated with lymphocytes rather that neutrophils, the more classic picture in bacterial infection. CSF glucose is two-thirds or higher of the serum level and CSF pressure is 6–15 cmH2O.

Question 38: FFTFT

It is important to ensure all patients are adequately starved prior to elective surgery to reduce the risk of aspiration. The Royal College of Nursing recommends the following as minimal intervals:

  • Water and other clear, non-carbonated drinks, including tea and coffee without milk – two hours

  • Breast milk – four hours

  • Food, drinks containing milk, carbonated drinks – six hours

In patients in whom you suspect gastric emptying may be abnormal, consideration should be given to performing a rapid sequence induction and securing the airway with an endotracheal tube.

Question 39: FFTFF

Bifascicular block is most commonly used to refer to the presence of a right bundle branch block co-existing with either an anterior or posterior fascicular block in the left bundle branch.

In isolated left anterior fascicular block the QRS width is normal: a maximum of 0.12 s. The only finding is that of left axis deviation. In left posterior fascicular block, right axis deviation is present without signs of right ventricular hypertrophy. Left anterior fascicular block is more common than posterior fascicular block; the fascicle has a dual blood supply.

The definition of trifascicular block is more contentious than that of bifascicular block. It is commonly taken to mean the presence of bifascicular block, that is right bundle branch block with co-existent left hemifascicular block, with co-existent first-degree atrioventricular block.

Question 40: FTFTF

In order to standardize the description of permanent pacing and defibrillation systems, a five-letter international classification system is accepted.The first three letters are always stated and describe the antibradycardia functions.The last two letters are additional functions and not always stated if absent.

For example, VVI00 describes a pacemaker that:

  • V: Paces the ventricle (the chamber paced; can be A – atrial, V – ventricle, D – dual, 0 – none)

  • V: Senses in the ventricle (the chamber sensed; can be A – atrial, V – ventricle, D – dual, 0 – none)

  • I: Is inhibited by sensed activity (the response to a sensed beat; can be 0 – none, T – triggered, I – inhibited, D – dual)

  • 0: Is not programmable (programmability; can be 0 – none, P – simple, M – multiprogrammability, C – communicating, R – rate responsiveness)

  • 0: Doesn’t have antitachycardia functions (antitachycardia function; can be 0 – none, D – dual, P – pace, S – shock)

Question 41: FTTTT

Amniotic fluid embolism (AFE) is a rare (1:50 000) disorder with a mortality of around 20–40%. It was once thought to have a mortality of around 80%, but better identification and management have reduced this to the current levels. It is thought to be an immune-mediated response rather than a direct embolic effect. There is no pathognomonic test and diagnosis is based on clinical signs. It can present atypically with symptoms ranging from a sense of feeling generally unwell to cardiac arrest; it is possible that it could present with an isolated coagulopathy. Management is predominantly supportive and the early involvement of critical care teams is essential to provide the best chance of survival and recovery.

Known risk factors include:

  • Maternal age >35

  • Induction of labour

  • Instrumental or operative delivery

  • Placental abnormalities

  • Pre-eclampsia/eclampsia

Question 42: FTFTF

For lobectomy, the calculation uses the number of bronchopulmonary segments removed compared with the total number, 19, in both lungs. Although previous guidelines used absolute values of FEV1, 1.5 litres for lobectomy and 2 litres for pneumonectomy, this may lead to false interpretations. For preoperative assessment these values (FEV1, DLCO) should always be expressed as a percentage of predicted volumes corrected for age, sex and height.

A ppoFEV1 <30% is not an absolute contraindication for lung resection. The patient can be offered lung resection if they accept the risk involved and potential impact on lifestyle, such as dyspnoea.

Question 43: FFFFF

Causes of a microcytic anaemia:

  • Iron deficiency

  • Thalassaemia

  • Sideroblastic anaemia

Question 44: TFTTF

Neonates are obligatory nose breathers and any obstruction causes difficulty in breathing. Tidal volume is the same as adults (7–10–1), respiratory rate is higher. Dead space is 50% of the tidal volume. Maintenance fluid is 100–1 per 24 h.

Question 45: FFFFF

Anaphylaxis is a type 1, IgE-mediated hypersensitivity reaction. Type 2 hypersensitivity reactions are cytotoxic immune-mediated reactions via IgG or IgM antibodies reacting to the presence of antigens. Type 3 immune-complex-mediated reactions involving antigen/antibody complexes cause activation of complement and neutrophils resulting in tissue damage – a more gradual process. Type 4 hypersensitivity reactions are delayed reactions resulting from antigen-specific T cells causing a macrophage-driven response. Anaphylaxis can occur in anyone, but atopic individuals are more prone. The commonest presentation, particularly under anaesthesia, is cardiovascular collapse and respiratory compromise secondary to bronchospasm. Rash is a non-specific sign and may be delayed, or difficult to ascertain under anaesthesia. Epipens deliver a dose a 0.3 ml of 1 in 1000 adrenaline. Current ALS guidelines recommend 0.5 ml 1 in 1000 adrenaline IM or in the case of adults 50 μg IV boluses if competent in the IV administration of adrenaline. As the quaternary ammonium group is commonly found in other drugs, food products and cosmetics, previous exposure to neuromuscular blockers is not necessary.

Question 46: TFTFT

The majority of complications are secondary to improper pressure point protection or prolonged positioning. Abdominal compartment syndrome has been described in patients who have had prone positioning; it is important to allow free movement of abdominal contents both to prevent this and allow for easier ventilation. Visual loss is as a result of external orbital pressure.

Question 47: FFFTF

In the UK, conscious sedation is defined as ‘a technique in which the use of a drug or drugs produces a state of depression of the central nervous system enabling treatment to be carried out, but during which verbal contact with the patient is maintained throughout the period of sedation’. The ASA classifies sedation into three levels:

  • Minimal sedation: drug-induced state where the patient responds normally to verbal commands. Cognitive function and physical co-ordination can be impaired, but airway reflexes, and ventilatory and cardiovascular functions, are maintained

  • Moderate sedation: patients respond purposefully to verbal stimuli, which may be accompanied with light tactile stimulation. This equates to conscious sedation

  • Deep sedation: patients respond only to repeated or painful stimulation; can be associated with significant ventilatory depression

Benzodiazepines can be up to eight times more potent when given after an opioid, therefore when they are to be used in combination, the opioid should be administered first and the benzodiazepine titrated carefully after the peak effect of the opioid is seen. The elimination half-life of midazolam is 1.5–3.5 hours. It is almost completely metabolized in the liver to hydroxylated derivatives that are conjugated to glucuronides, these are then excreted in the urine, thus renal impairment has little effect. The AAGBI recommends that continuous capnography should be used for all patients undergoing moderate or deep sedation, and should be available in areas where these patients are recovered. It is appropriate to deliver oxygen, usually via nasal cannula, to all sedated patients from the administration of the sedatives until they are ready for discharge from recovery.

Question 48: TTFFT

Factors influencing the development of respiratory distress syndrome:

  1. Protect:

    1. Cortisol

    2. β-adrenergic drugs

    3. Epidermal growth factor

    4. Thyroxine

    5. Prolactin

  1. Predispose:

    1. Prematurity

    2. Male gender

    3. Ethnicity (Caucasian)

    4. Genetic predisposition

    5. Insulin

    6. Hypoxia

    7. Hypothermia

    8. Acidosis

    9. Hypotension

Question 49: FTTTF

The ulnar nerve is a branch of the medial cord. The musculocutaneous nerve is a branch of the lateral cord.

Question 50: TFFFT

When oxygen demand exceeds supply, muscle cells begin generating ATP anaerobically. This process produces lactic acid, which is buffered by bicarbonate and results in an increase in CO2. The VO2 at the point this occurs is called the anaerobic threshold. Therefore the anaerobic threshold will not vary with patient motivation, but the peak VO2 will only reach as high as the effort the patient puts into the test. Anaerobic threshold only reduces slightly with increased age, but will be reduced in proportion to the degree of organ impairment. An anaerobic threshold of at least 11–1.min–1 is required to safely undertake significant surgery.

Question 51: TFTTT

Complex regional pain syndrome (CRPS) usually develops after trauma to a limb. The predominant symptom is pain, but it is also associated with sensory, autonomic, motor, skin and bone changes. For a diagnosis of CRPS to be made the patient must meet the Budapest Diagnostic Criteria (Table 5.51.1).

All the following statements must be met:

  • The patient has continuing pain that is disproportionate to the inciting event

  • The patient has at least one sign in two or more of the categories below

  • The patient reports at least one symptom in three or more of the categories below

  • No other diagnosis can better explain the signs and symptoms

Table 5.51.1 Budapest Diagnostic Criteria

Category Sign/symptom
1 ‘Sensory’ Allodynia (pain to light touch and/or temperature sensation and/or deep somatic pressure and/or joint movement) and/or hyperalgesia (to pinprick)
2 ‘Vasomotor’ Temperature asymmetry (>1 °C if counted as a sign) and/or skin colour changes and/or skin colour asymmetry
3 ‘Sudomotor/oedema’ Oedema and/or sweating changes and/or sweating asymmetry
4 ‘Motor/trophic’ Decreased range of motion and/or motor dysfunction (weakness, tremor, dystonia) and/or trophic changes (hair/nail/skin)

Hypoaesthesia is not part of the diagnostic criteria.

Question 52: FTTTT

Epilepsy is defined as two or more epileptic seizures with no immediately identifiable cause. The clinical manifestations of seizures are extremely variable and can range from behavioural disturbance to life-threatening and unremitting convulsions. Investigations to determine the cause for a patient presenting with seizures include electroencephalography (EEG) as well as imaging modalities including CT, MRI, SPECT and PET scans. Patients with established epilepsy show abnormal epileptiform activity in up to 50% of cases, but interestingly this is also apparent in 4% of patients without epilepsy.

It may be necessary to administer anticonvulsant drugs perioperativly, particularly if the risk of further seizures is high or the seizures are particularly poorly controlled. Of the commonly used drugs sodium valproate, phenytoin and levetiracetam are available in intravenous forms.

Status epilepticus (SE) is defined as continuous seizure activity lasting 30 minutes or intermittent seizures for this period without regaining consciousness. SE carries a mortality of 25% and has systemic complications that include respiratory failure, pulmonary oedema, disseminated intravascular coagulopathy, myocardial ischaemia, arrhythmias, cerebral hypoxia and central venous thrombosis (not an exhaustive list). The prompt management of SE is therefore crucial; lorazepam 0.1–1 is commonly recommended as a first-line agent.

Question 53: FFTTF

The National Network for Burn Care (NNBC) gives the following definitions:

• Burn centre – This level of in-patient burn care is for the highest level of injury complexity and offers a separately staffed, geographically discrete ward. The service is staffed to the highest level of critical care and has immediate operating theatre access.

• Burn unit – This level of in-patient care is for the moderate level of injury complexity and offers a separately staffed, discrete ward.

• Burn facility – This level of in-patient care equates to a standard plastic surgical ward for the care of non-complex burn injuries.

Question 54: FFTTT

Carcinoid tumours are neuroendocrine tumours that secrete a large amount of vasoactive peptides such as serotonin, dopamine, corticotrophin, histamine, substance P, neurotensins, kallikrein and prostaglandins. The clinical features of carcinoid crisis are due to the intravascular release of these hormones. If the primary tumour is found in the gut (as in 67.5% of cases), the vasoactive hormones are metabolized by the liver so rarely cause systemic effects. For this reason, frequent or severe attacks of flushing, hypotension and bronchospasm are thought to be due to hepatic metastases or non-GI tumours (e.g. bronchopulmonary). These hormones, when released into the venous system, cause right-sided (tricuspid and pulmonary) valvular lesions and fibrous thickening of the endocardium. Left-sided lesions are rare and usually signify right to left shunting or bronchial carcinoid. Cardiac complications are associated with an increase in perioperative complications. Tyrosine-containing foods may precipitate an attack due to tumour metabolism, as may histamine-releasing drugs such as atracurium and morphine. Noradrenaline has been shown to activate kallikrein in tumours and may lead to synthesis and release of bradykinin, resulting paradoxically in vasodilatation and worsening hypotension.

Question 55: TFTTT

NICE guidelines recommend ceftriaxone as first-line therapy (unless calcium-containing solutions are used, in which case cefotaxime should be used). Neuroimaging is indicated if there is suspicion of raised ICP, an alternative intracranial diagnosis is suspected, focal neurological signs are present or on expert recommendation. In the UK, suspected or proven meningitis is a notifiable disease. Young children may present subtle features suggesting raised ICP, as well as bradycardia, hypertension, reduced conscious level, unilateral pupillary dilatation, tense fontanelles, nausea and vomiting, and papilloedema. NICE recommend considering intubation if shock persists after more than 40–1.

Question 56: TTFFT

Wilson’s criteria comprise five components: obesity, restricted jaw movement, receding mandible, the presence of buckteeth and reduced neck movement. Each variable receives a score between zero and two. A total score greater than two is predictive of a difficult intubation. Previous difficult intubation and a reduced thyromental distance are predictive of difficult intubation, but do not form part of Wilson’s criteria.

Question 57: TTFTT

Ultrasound-guided regional blocks provide faster sensory onset and improved success rates when compared to landmark-based techniques. There is no current evidence to suggest that ultrasound use in regional anaesthesia reduces the incidence of neurological complications. However, there is a reduction in the incidence of vascular puncture and haematoma when undertaking regional anaesthesia using ultrasound guidance.

There is level 1a evidence to confirm that phrenic nerve blockade is almost always seen with higher-volume (20 ml or more) local anaesthetic use during brachial plexus block. Ultrasound guidance allows practitioners to use low volumes.

Question 58: FTTFF

The Goldman Cardiac Risk Index is a multifactorial index of cardiac risk in non-cardiac surgery (Table 5.58.1). It was developed in 1977 from retrospective data on 1001 patients undergoing non-cardiac surgery to identify patients at risk from major perioperative cardiovascular complications. The score is made up from nine independent risk factors, which have different weightings:

  1. 1. Third heart sound/elevated JVP – 11

  2. 2. MI in last six months – 10

  3. 3. Rhythm other than sinus – 7

  4. 4. Ventricular ectopics (>5 per minute) – 7

  5. 5. Age >70 – 5

  6. 6. Emergency operation – 4

  7. 7. Significant aortic stenosis – 3

  8. 8. Poor medical condition of patient or bedridden – 3

  9. 9. Abdominal or thoracic operations – 3

Table 5.58.1 The Goldman Cardiac Risk Index

Class Score Complication risk (%)
1 0–5 1
2 6–12 7
3 13–25 14
4 26–53 78

Overall the index has high specificity, but low sensitivity.

The index was revised in 1999 by Lee, known as the Revised Cardiac Risk Index, based on six independent variables (chronic kidney disease, ischaemic heart disease, heart failure, cerebrovascular disease, insulin-dependent diabetes, intraperitoneal/thoracic surgery). This has been further superseded by the American College of Surgeons Risk Calculator (2014).

Question 59: FFFTF

Adrenaline has both inotropic and chronotropic effects, resulting in an increased cardiac workload. This will eventually increase the oxygen consumption, resulting in lactic acidosis. Adrenaline also enhances hepatic gylcogenolysis and glycolysis whilst reducing pyruvate utilization, leading to lactic acid production. The increased heart rate in this scenario gives a clue that the patient may be helped by a reduction in the adrenaline infusion rate. Starting vasopressin or increasing the rate of noradrenaline will not add any benefit as both MAP and urine output are adequate. Dopamine will further increase the heart rate and oxygen consumption.

Question 60: FTTFT

Cardiac disease remains a significant cause of maternal morbidity and mortality. Predominant causes of cardiac death are sudden adult death syndrome, myocardial infarction, aortic dissection and cardiomyopathy. It is the greatest cause of indirect and overall maternal death. Infarction is the fourth biggest cause of death (behind the others listed above). Cardiomyopathy can be difficult to diagnose, as its symptoms may be seen normally in later pregnancy – shortness of breath, swelling, tachycardia and reduced exercise tolerance. Dilated cardiomyopathy has a significantly worse prognosis than hypertrophic due to the additional stress of pregnancy and labour producing a high risk of left ventricular decompensation. Peripartum cardiomyopathy can present late and should be considered in any patient with symptoms of cardiac failure up to six months post delivery. Aortic dissection is still a leading cause of death, with most of those occurring involving the ascending aorta. Dissection should be excluded in any patient with severe chest pain and investigation with CT, MRI or USS is appropriate.

Question 61: TFFTF

Thalassaemias have an autosomal recessive pattern of inheritance. Cooley’s anaemia is the homozygous, major clinical phenotype of β-thalassaemia. It results in a profound anaemia requiring multiple blood transfusions. Bart’s hydrops fetalis syndrome is the most severe form of α-thalassaemia, where there is no functional α-allele. This results in formation of haemoglobin-Bart’s (four γ-chains). Haemoglobin-Bart’s has a very high affinity for oxygen, resulting in very little tissue oxygen delivery. Bart’s hydrops fetalis syndrome usually results in intrauterine or early neonatal death, as well as serious maternal risks. A difficult laryngoscopy must be anticipated as a consequence of facial changes (for example, maxillary hypertrophy) from marrow hyperplasia. Haemolysis may be precipitated by oxidant drugs, including:

  • Penicillin

  • Prilocaine

  • Nitroprusside

  • Vitamin K

  • Aspirin

Question 62: TTFFF

Cyanotic heart disease is due to venous blood entering the systemic circulation, having bypassed the lung. The blood that is pumped out to the body is low in oxygen. Heart defects like tetralogy of Fallot, transposition of the great arteries, truncus arteriosus, Ebstein’s anomaly and coarctation of aorta can cause cyanosis. Tetralogy of Fallot is the most common congenital cyanotic heart disease. The classic form includes four defects, i.e. large VSD, pulmonary stenosis, right ventricular hypertrophy and an over-riding aorta.

Question 63: TTFTT

Malignant hyperpyrexia (MH) is a rare autosomal dominant condition. The incidence is approximated at 1:200000, resulting from abnormal ryanodine receptors. Release of calcium through faulty channels results in sustained muscle contraction. This results in muscle cell damage, with the release of potassium, myoglobin and creatinine kinase. These patients are therefore at significant risk of acute renal failure and may need renal replacement therapy. With increased metabolism, temperature and carbon dioxide production, it would seem logical to expect cutaneous vasodilatation. However, catecholamine surges result in vasoconstriction initially. Increased metabolic demands of muscle result in diversion of cardiac output from cutaneous vasculature beds to muscle mass. Disseminated intravascular coagulation is a recognized complication of malignant hyperpyrexia and there are case reports of compartment syndrome associated with confirmed cases of malignant hyperthermia.

Question 64: TTFTT

There tends to be some unintended movement of the COETT during change in position and this may lead to carinal stimulation or endobronchial intubation, which in turn can lead to atelectasis. Redistribution of blood within the lower limbs can lead to fluid overload in susceptible patients. Prolonged positioning is a risk factor for the development of VTE and compartment syndrome of the lower limbs; the sole use of foot stirrups versus combined calf and foot supports shows no difference in the risk. Alopecia can develop in any position with the potential for ischemia of the scalp. There is little risk of pressure on the orbit due to the position (although the risk of damage from the improper use of a facemask or lack of protective measures for the eye can be a cause of damage in any position).

Question 65: FTFFF

Low-frequency jet ventilation (LFJV) was first described in 1967 by Douglas Sanders. His technique allowed continuous patient ventilation alongside unrestricted surgical access to the airway via an open rigid bronchoscope. LFJV is delivered via a handheld device, such as a Sanders injector or a Manujet, through a short rigid narrow cannula. It can be used in conjunction with rigid bronchoscopes or laryngoscopes for short surgical procedures, and also has an important role in emergency airway management via a cricothyroidotomy cannula. LFJV uses a high-pressure oxygen source and the entrainment of air via the Venturi principle, so the delivered tidal volume is the sum of the injected and entrained volumes. A jet frequency of between 8 and 20 min–1 is normally appropriate; this allows time for both chest wall expansion and passive recoil. The upper airway must be patent to allow adequate exhalation of gases to prevent air-trapping and barotrauma. Capnography cannot easily be used, therefore the best way to assess adequacy of ventilation is to observe the chest wall for expansion and perform arterial blood gas analysis. When using LFJV for surgical procedures, inhalation agents cannot be delivered, hence anaesthesia is maintained with TIVA.

Question 66: TTTTT

Achondroplasia is associated with a large tongue and mandible, stenosis of the foramen magnum, limited neck extension and increased incidence of atlantoaxial instability. Hurler’s and Hunter’s syndromes are both hereditary, progressive mucopolysaccharidoses, characterized by progressive generalized infiltration and thickening of the soft tissues. They are associated with extremely difficult airways for a number of reasons: macroglossia, tonsillar and adenoidal hypertrophy, narrowing of the nasal passages, short immobile neck, TMJ involvement, cervical spine instability, and supraglottic and infraglottic soft tissue thickening. Beckwith–Wiedemann syndrome is the most common overgrowth syndrome in infancy, it describes the combination of macroglossia, macrosomia (birth weight and length greater than the 90th percentile), mid-line abdominal wall defects, ear creases or pits, and neonatal hypoglycaemia. Goldenhar syndrome (oculo-auriculo-vertebral dysplasia) is characterized by a wide range of congenital anomalies, including micrognathia, facial asymmetry and hypoplasia, vertebral anomalies causing limited neck movement and ear malformations with hearing loss. Other anomalies of the oral cavity sometimes seen include a high arch or cleft palate and abnormalities of the tongue.

Question 67: TTTFF

This preterm baby suffers from severe respiratory distress syndrome. The preterm labour is mostly due to infection, secondary to prolonged rupture of membranes. Hence antibiotics should be given in this case. Investigations that would help to confirm the diagnosis include a chest radiograph, which usually shows symmetrical reticulogranular shadowing and excludes pulmonary hypoplasia, and an echocardiogram is essential to determine if there is pulmonary hypertension leading to the higher FiO2 requirement. Pulmonary maturity can be assessed by measuring the lecithin-to-sphingomyelin ratio from baby’s pharynx or stomach. Increasing PEEP and the use of high-frequency oscillation are recognized measures to improve oxygenation rather than increasing FiO2 for longer periods, leading to oxygen toxicity. Surfactant therapy is usually used as prophylaxis to the preterm within the first hour of birth. This leads to significant reduction in pneumothorax, bronchopulmonary dysplasia and mortality.

Question 68: TFFFF

Packed red cells may be stored for up to 35 days with SAGM (saline adenine glucose mannitol). Platelets can be stored for up to five days at room temperature (20–24 °C) and up to seven days with bacterial screening. They must be continually agitated to prevent clumping. Storage is limited to five days due to the risk of bacterial contamination. Platelets are labelled with ABO and rhesus type. ABO compatibility is preferred, but in adults ABO-incompatible platelets can be used due to the small volume of plasma containing antibodies.

Cross-matching is not required because a platelet unit contains only 2–5 ml of red cells. This small red cell volume is capable of creating immunization of the Rh-D antigen and therefore Rh compatibility is required for all Rh-negative children and Rh-negative mothers of childbearing age to prevent the formation of anti-D antibodies.

Question 69: FFFTF

The aim of electroconvulsant therapy (ECT) is to produce a generalized seizure lasting between 15 and 120 seconds. First described in 1938, during the first three decades of its use anaesthesia was not employed, but now a general anaesthetic with paralysis is obligatory.

The cardiovascular response to ECT begins with an initial parasympathetic discharge that can result in bradycardia and hypotension. This is followed by a sympathetic response that can involve cardiac arrhythmias. Myocardial ischaemia is a risk due to a combination of increased myocardial oxygen consumption and reduced myocardial oxygen supply.

Common induction agents include propofol and etomidate. Propofol is associated with quicker emergence, whereas etomidate produces the longest seizure duration and may reduce the seizure threshold. Neuromuscular blocking agents reduce the risk of serious injury due to muscular convulsions. Suxamethonium is the most commonly used agent, usually at a dose of 0.5–1 . Larger doses are sometimes required, for example in cases of osteoporosis or severe cachexia.

Question 70: FFTFF

The patient is describing the typical symptoms of trigeminal neuralgia (TN). It is defined as a sudden, usually unilateral, brief stabbing recurrent pain in the distribution of one or more branches of the trigeminal nerve. TN is usually subdivided into idiopathic and secondary categories. Idiopathic TN has no obvious cause other than vascular compression. Secondary TN occurs as a result of a structural lesion such as multiple sclerosis.

The diagnosis of TN can often be made on the basis of the history alone. To image the trigeminal ganglion and surrounding vessels, MRI and angiography are employed.

The superior cerebellar artery is the more likely vessel to be compressing the trigeminal nerve. However, not all patients with idiopathic TN have obvious neurovascular contact, which has led to the development of other theories regarding its pathophysiology.

Carbamazepine is widely used in the management of TN and with some success. Gabapentin and the lidocaine plaster are also management options, but are not generally first line. Acyclovir is used in the management of acute herpes zoster.

Question 71: TFFFT

See explanation for Question 28.

Question 72: TFTTF

Myasthenia gravis (MG) is an autoimmune disease characterized by worsening muscle weakness. In its early stages the muscle weakness may affect the ocular muscles alone, but as the disease progresses the effects on skeletal muscle are more pronounced and eventually this may lead to respiratory failure. The pathophysiology is attributed to autoantibodies specific for the postjunctional acetylcholine receptor, reducing the number of functional receptors and preventing normal neuromuscular transmission. There are a number of markers of disease severity that are predictive of the need for postoperative ventilation and these include: duration >6 years, pyridostigmine dose >750–1, preoperative vital capacity of <2.9 l and co-existing chronic respiratory disease.

MG sufferers are very sensitive to the effect of non-depolarizing muscle relaxants (NDMRs) and so a tenth of the usual dose is recommended for intubation and subsequent maintenance doses. Myasthenic patients are, however, resistant to the effect of suxamethonium and so a slightly increased dose (1.5–1 ) is usually needed for rapid sequence induction. Reversal of NDMRs with a normal dose of neostigmine is possible, but its use carries the risk of precipitating a cholinergic crisis. The avoidance of NDMRs or the use of atracurium (spontaneously broken down) is therefore preferable to reversal using neostigmine.

Question 73: TTTTT

A number of different devices can be used to monitor intracranial pressure; examples include the extradural fibreoptic probe, subarachnoid screw and external ventricular drain. These devices measure intracranial pressure, but some can be used to calculate other indices, including compliance or pressure/volume index and to drain CSF. The intracranial pressure waveform is similar to the trace produced by an arterial line, since it corresponds to the pressure changes in large intracerebral vessels, as well as varying with respiration, reflecting changes in central venous pressure. The three main waveforms observed are as follows. ‘A’ waves are also known as plateau waves (amplitude 50–100 mmHg, lasting 5–20 min). These represent severely reduced compliance and are most commonly associated with tumours and cerebral vasodilatation. ‘B’ waves (amplitude <50 mmHg, occur with a frequency of one per minute) are associated with changes in respiration and are less useful clinically. A variation of ‘B’ waves known as ‘ramp’ waves is associated with hydrocephalus. ‘C’ waves (amplitude <20 mmHg, frequency of 4–8 per minute) are not useful clinically and relate to normal physiology: blood pressure and vasomotor tone. Parameters vary according to the pathology identified, but a sustained rise in intracranial pressure of >20 mmHg for 30 minutes usually warrants active management.

Question 74: TFTFT

The moorLD12-BI is a laser Doppler blood-flow imaging system used for the non-invasive mapping of blood flow in an area of skin that has been burnt. NICE guidance supports its use to guide treatment decisions for patients in whom there is uncertainty about the depth and healing potential of burn wounds that have been assessed by experienced healthcare clinicians. It uses a low-power laser beam that scans the burn area and using Doppler frequency shift calculations displays the blood flow as a colour coded blood-flow image and a colour video image of the burn wound. Healing potential results based on the blood-flow image are calculated and reported in three categories: less than 14 days, 14–21 days and more than 21 days. In burn wounds of intermediate (also known as indeterminate) depth the moorLD12-BI can be used to demonstrate which areas of any burn wound require surgical treatment and which do not, enabling decisions about surgery to be made earlier and for surgery to be avoided in some patients. It has been shown to have a higher accuracy than clinical assessment, with a variety of criteria, including the ability to predict wound healing in 14–21 days.

Question 75: FFTFT

Pulmonary hypertension (PH) is defined as a mean pulmonary arterial pressure over 25 mmHg at rest with a wedge pressure <12 mmHg; moderate PH is said to occur when the PA pressure is >35 mmHg. The key to safely anaesthetizing these patients is to maintain coronary perfusion pressure by ensuring a normal or near normal SVR, avoiding a loss of right ventricular preload, avoiding high PEEP, hypoxia, hypercarbia, acidosis, hypothermia and pain – all conditions which will increase pulmonary vascular resistance. Due to their inodilator properties, which may decrease SVR, milrinone and dobutamine are not recommended for use in PH. Central neuraxial anaesthesia can be safely used in PH, as long as attention is paid to minimizing the cardiovascular effects of these techniques. There are no α1-receptors in the pulmonary circulation. Ketamine may raise pulmonary vascular resistance, but its safe use has been reported in the literature.

Question 76: TTFFF

A thyroid storm is a hypermetabolic crisis that may occur in thyroid disease or be precipitated by drugs, radioiodine or surgery. Mortality may be as high as 30%. Management includes resuscitation and cooling. Specific therapy includes:

  • Propranolol, which reduces effects via β-blockade and reduction in T4 to T3 conversion

  • Hydrocortisone, which treats relative adrenal insufficiency and blocks T4 to T3 conversion

  • Lugol’s solution, which delivers high concentrations of iodine, which suppresses thyroid hormone synthesis via the Wolff–Chaikov effect (not the Jod–Basedow mechanism).

Amiodarone has a high iodine content and can be a precipitant of a thyroid crisis, so should be used with great caution. Paracetamol can be used as an antipyretic, but NSAIDs can displace bound thyroid hormone and should be avoided.

Question 77: TTFFT

The systemic effects of cigarette smoke are widespread, owing to the different chemicals contained therein. In the respiratory system, airway reactivity is increased, predisposing to laryngospasm and bronchospasm. There is a greater production of airway secretions compared to non-smokers, and combined with impaired ciliary function, results in mucous plugging and sputum retention. Smokers are at risk of developing COPD and lung cancer.

In the cardiovascular system, nicotine acts to increase heart rate, systemic vascular resistance and blood pressure. Prolonged exposure to cigarette smoke increases the risk of developing ischaemic heart disease and peripheral vascular disease. In the presence of carboxyhaemoglobin, the oxyhaemoglobin dissociation curve is shifted to the left, resulting in impaired release of oxygen to the tissues and the risk of hypoxia. Hepatic enzymes can be induced by cigarette smoking; this may result in lower levels of drugs than might otherwise be anticipated. Smoking reduces the risk of postoperative nausea and vomiting. The mechanism by which this occurs is uncertain.

Question 78: TFFFF

Atrial fibrillation with a spontaneously slow ventricular response is an indication for pacemaker insertion. The pressing need for surgery must be balanced against the risk of compromise to the cardiovascular system if a pacemaker is not inserted preoperatively and an alternative mechanism of pacing, such as transcutaneous pacing, should be available.

Patients who receive β-blockers as part of their routine management of atrial fibrillation should take these on the morning of surgery. The risk of developing a rapid ventricular response in the perioperative period outweighs that of hypotension intraoperatively, which is usually relatively straightforward to manage with vasoconstrictors or chronotropic agents.

Digoxin doses should be reduced by a third when an oral dose is converted to intravenous. It is not essential to measure digoxin levels on the day of surgery in patients who have been established on digoxin long term without a recent dose change; adequate rate control and an ECG without concerning features of toxicity are acceptable.

Patients undergoing elective surgery are able to take their routine medications – unless contraindicated – with a small amount of water. There is no need to routinely convert oral medications to intravenous formulations.

Question 79: TTTFT

Interscalene block provides reliable anaesthesia and analgesia for procedures (open and arthroscopic) involving the shoulder joint, lateral two-thirds of the clavicle and proximal humerus. It effectively blocks the proximal nerve roots, distal cervical plexus (supraclavicular nerves) and important nerves such as the suprascapular, which exit proximally from the plexus. A sterile high-frequency (10–13 MHz) probe is used to scan the neck transversely between the level of the cricoid cartilage and supraclavicular fossa until an optimal view of the hypoechoic round images of C5 and C6 nerve roots or upper trunk is obtained. There is level 1a evidence to confirm that phrenic nerve blockade is almost always seen with traditional high volume (20 ml or more) blocks, including continuous infusions for postoperative analgesia.

Question 80: FTTFT

The liver is the principle organ in the body for drug metabolism. The phases of metabolism are typically split into two and aim to make the drug easier to excrete. Phase 1 reactions are non-synthetic and involve formation of a new or modified functional group, or cleavage (commonly oxidation, reduction, hydrolysis or hydration). Phase 2 reactions are synthetic and involve conjugation with endogenous hydrophilic groups to increase solubility and hence renal excretion (e.g. glucuronide, sulfate, glycine).

Benzodiazepines undergo oxidation in the liver, whilst morphine undergoes glucuronidation (the most common phase 2 reaction). Morphine is metabolised to morphine-3- (inactive) and morphine-6-glucoronides (active).

Cytochrome enzymes function as electron transfer agents and are found in many tissues including the liver, gut and kidneys. They are proteins containing haem as a co-factor. The term P450 is from the spectrophotometric wavelength absorption maxima for the enzyme in the reduced state complexed with carbon monoxide (450 nm). These enzymes are typically found on the inner mitochondrial membrane or in the endoplasmic reticulum, and are generally terminal oxidase enzymes in electron transfer chains. Cytochrome P450 enzymes are the major enzymes involved in drug metabolism. They are also important in hormone synthesis and breakdown.

Question 81: TFTTF

Sepsis and its related complications remain the most common cause of death in the ICU. Oxygen utilization rather than delivery is the main problem. Normally, antioxidant defences act to protect the mitochondria against the production of reactive oxygen species (ROS). In sepsis this mechanism is overwhelmed by the increased production of ROS and nitric oxide. This results in an oxidative stress and mitochondrial damage leading to impaired ATP production. Although antioxidants have shown some promising results in the laboratory, there is still little evidence to support their regular use in humans.

Question 82: TTTFF

It is becoming more common for women with spinal cord injuries to go through labour. The level of lesion involved can have a significant effect upon potential complications and labour management. Lesions above T5 have a reasonable likelihood of autonomic dysreflexia being present and this can cause severe cardiovascular instability, commonly causing hypotension, headaches and bradycardia. In extreme cases cardiac arrest is possible. Labour can be a trigger for this instability and therefore a pre-emptive epidural can be used to protect against it. The instability can continue for up to 48 hours post delivery so the epidural should continue into the postdelivery period. Suxamethonium should be avoided for up to one year post injury to prevent a hyperkalaemic response to its use, although this is controversial and many clinicians would avoid suxamethonium altogether.

Question 83: TTTTT

Since the majority of pulmonary resection patients have a smoking history, they already have one risk factor for coronary artery disease. Surgical risk estimate is a broad approximation of 30-day risk of cardiovascular death and myocardial infarction that takes into account only the specific surgical intervention, without considering the patient’s co-morbidities. Intrathoracic, non-major surgeries are considered as intermediate-risk procedures, whereas pneumonectomy is considered a high-risk procedure. The surgical stress increases myocardial oxygen demand. Surgery also causes alterations in the balance between prothrombotic and fibrinolytic factors, potentially resulting in increased coronary thrombogenicity. CT angiography has a high sensitivity for coronary stenosis, but is less specific. Thus, a patient with a normal CT coronary angiogram can proceed to surgery.

Question 84: FTTFT

The parathyroid glands lie within close anatomical proximity to the thyroid gland. As such, the parathyroid glands may be accidently damaged during thyroid surgery. Transient hypocalcaemia may present 36 hours postoperatively in 20% of patients having undergone thyroidectomy for large multinodular goitre. Permanent hypocalcaemia is rare. Hypocalcaemia may present with:

  • Perioral tingling

  • Muscle twitching

  • Confusion

  • Tetany

  • Layngospasm

  • Seizures

  • Ventricular arrhythmias

  • Trousseau’s sign – carpopedal spasm (may be caused by non-invasive blood pressure cuff inflation)

  • Chvostek’s sign – facial twitch or spasm upon tapping over the facial nerve at the parotid gland

  • Prolonged QT interval

Treatment with calcium replacement should commence immediately. The route of calcium replacement depends upon serum calcium concentration:

  • Serum calcium >2 mmol.l–1 – oral calcium replacement

  • Serum calcium <2 mmol.l–1 – intravenous calcium with, e.g. 10 ml of 10% calcium gluconate. A calcium infusion may be required in severe cases

Question 85: FFFTF

Enzyme functions tend to be poorer in newborns so suxamethonium has a prolonged action. In addition, 80% of the body weight in a neonate is water so there is a larger extracellular volume that can dilute suxamethonium.

Question 86: TFTTT

Laparoscopic surgery reduces venous return. Insufflation can cause marked vagal stimulation resulting in bradycardia; coupled with reduced venous return in a dehydrated elective patient, this can result in marked hypotension. Insufflation should therefore be gradual with intra-abdominal pressures limited to 20 mmHg. Trochar introduction to the abdominal cavity may also result in vascular injury, resulting in rapid hypovolaemia. Anaphylaxis should be amongst the differentials – cardiovascular collapse is a common initial presenting feature of anaphylaxis under general anaesthesia. Air embolism is a risk with laparoscopic surgery, especially in the presence of venous injury. However, as CO2 is a relatively soluble gas, any gas embolism should be short-lived – which is the reason it is the gas of choice when creating a pneumoperitoneum in laparoscopic surgery. Too small a blood pressure cuff would cause falsely high blood pressure readings at the extremes of blood pressure.

Question 87: TTFFF

Awareness is most often associated with emergency situations or patients with a higher ASA grade due to the higher risk of haemodynamic instability. Patients with chronic alcohol and opiate use are more likely to be aware compared to those with acute intake.

Patients with TIVA are not proven to have higher rates of awareness.

Question 88: FFFTF

The Difficult Airway Society (DAS) rapid sequence induction (RSI) guideline advises:

  1. 10 N of pressure to the cricoid while the patient is awake and 30 N once consciousness has been lost

  2. That during initial tracheal intubation (Plan A), no more than three attempts should be made at intubation

  3. That a second dose of muscle relaxant should not be administered

During anaesthesia, oxygen consumption in a healthy adult stays relatively constant at approximately 250 ml.min–1. During a RSI, haemoglobin is not important as an oxygen store, but as an oxygen transporter, therefore anaemia will only cause a small decrease in the time taken to reach critical hypoxia. However, if the FRC is reduced, anaemia will have a more significant effect on the time taken for desaturation to occur.

Question 89: FTFFF

The most commonly used irrigation fluid is glycine 1.5% in water, which is hypotonic, with an osmolality of 220 mmol.l–1. Irrigation fluid is normally absorbed at a rate of approximately 20 ml.min–1, although absorption can be much greater. The rate of absorption depends on the infusion pressure of the irrigation fluid and the venous pressure within the patient; therefore, the pressure of the irrigation must be kept to the minimum that still allows adequate flow (it should never be at a height of greater than 100 cm). TURP syndrome is the result of large amounts of irrigation fluid being absorbed through open venous sinuses, which causes fluid overload and hyponatraemia. TURP syndrome is more common in procedures lasting over an hour, when the prostate weighs more than 50 g, when the patient is hypovolaemic/hypotensive (as this creates a greater pressure gradient for absorption) and when high irrigation pressures are used.

Question 90: TTFTT

The patency of the ductus arteriosus (DA) depends on the high concentration of prostaglandin E2. Acidosis and low arterial pO2 are the two main stimuli for PG E2 release. In pulmonary hypertension, the blood flows from the pulmonary trunk to the aorta before reaching the lung (deoxygenated blood), leading to release of PG E2, maintaining the DA open.

Question 91: TTTTF

Local anaesthetic toxicity depends on the volume of the drug injected, as well as the absorption rate and the site of injection. Intercostal blocks have the highest rate of absorption after intravenous, then caudal, paracervical, epidural, brachial, sciatic and subcutaneous.

Signs of LA toxicity depend on the plasma concentration of the individual agent used. For example: bupivacaine concentration of 2–4 μ–1 and lignocaine level of 10–12 μ–1 can initiate the CNS excitatory stage of LA toxicity. Circumoral numbness and tingling are the first signs of toxicity, followed by respiratory then cardiovascular signs and symptoms.

Blood samples should be taken to diagnose the plasma levels of the drug used, yet not as a first line of action. First stop the injection, then deal with the collapsed patient in an ABC manner. The appropriate action is 100% O2, with constant CVS monitoring and supportive treatment. Candidates would be advised to familiarize themselves with the AAGBI guidelines regarding the use of intralipid.

Question 92: TFTTF

Cardiopulmonary exercise (CPET) testing requires appropriate monitoring as listed and two members of staff, one to instruct and look after the patient and the other to watch the monitoring screen and run the test. The equipment includes a static cycle and a metabolic cart containing a gas analyzer to enable breath-by-breath measurement of oxygen consumption (VO2) and carbon dioxide production (VCO2). The duration of exercise is between 6 and 10 minutes.

Question 93: TFFFT

The sciatic nerve is formed from the nerve roots L4 to S3. The two components of the nerve (tibial and common peroneal) diverge approximately 4 to 10 cm above the popliteal crease to separately continue their paths into the lower leg.

Blocking the sciatic nerve will provide anaesthesia of the leg below the knee with the exception of the medial strip of skin, which is innervated by the saphenous nerve.

The inferior or Raj approach to the sciatic nerve requires the patient to lie supine with the knee flexed to 90°. A line is drawn connecting the greater trochanter to the ischial tuberosity and needle insertion is at the halfway point in the groove between the hamstring and the adductor muscles.

The sciatic nerve is usually found at a depth between 40 and 80 mm.

Adrenaline is not advised because of the risk of ischaemia of the sciatic nerve.

Question 94: FFFTF

Dose equivalence of opioid patches:

Table 5.94.1 Buprenorphine

Patch Drug delivery μg.h–1 Oral morphine mg per 24 h
Butrans®5 5 5–10
BuTrans® 10 10 10–20
BuTrans®20 20 25–40

Table 5.94.2 Fentanyl

Patch Drug delivery μg.h–1 Oral morphine mg per 24 h
Fentanyl 12 12 20–60
Fentanyl 25 25 60–100
Fentanyl 50 50 120–200
Fentanyl 75 75 180–300
Fentanyl 100 100 240–400

Question 95: TTFFF

See explanation for Question 27.

Question 96: TTTFF

See explanation for Question 26.

Question 97: FTTFT

Chlorhexidine gluconate was developed in the UK in the 1950s. It is a cationic, bisbiguanide molecule that is used widely for skin decontamination prior to procedures. It has good activity against Gram-positive bacteria, somewhat less activity against Gram-negative bacteria and fungi, and is minimally active against mycobacteria. It is not sporicidal and because chlorhexidine is a cationic molecule, its activity can be reduced by natural soaps, various inorganic anions, non-ionic surfactants and hand creams containing anionic emulsifying agents. For skin preparation prior to central neuraxial block, a 0.5% chlorhexidine preparation is recommended. The antimicrobial activity of chlorhexidine is not seriously affected by the presence of organic material, including blood. Care must be taken to avoid contact with the eyes, as concentrations of 1% or greater can cause conjunctivitis. Chlorhexidine is also ototoxic and direct contact with brain tissue or meninges should be avoided.

Question 98: TFFFF

Standard ET tubes can be used to isolate one lung in an emergency, and in conjunction with either bronchial blockers (or unconventionally, Fogarty or Foley catheters), or pulmonary artery catheters in paediatrics, put down an ET tube. However, for elective surgery this is not recommended, and an appropriately sized double lumen tube should be used. The dependent (lowermost) lung is the lung that is being ventilated, so clamping its pulmonary artery will dramatically worsen hypoxia. Left-sided double lumen tubes are most commonly used so that the right upper lobe is not accidentally occluded. Malpositioned ET tubes have been implicated in 30% of deaths in oesophagectomies. The double lumen tube is rotated 90° on passing through the vocal cords.

Question 99: FFFFF

A low intrinsic thyroid function blunts responses to inotropes and vasopressors – however, cardiovascular responses are variably affected and cautious initiation is recommended. Thyroid imaging is not essential, measurement of thyroid function is. Patients are typically hyponatraemic due to reduced cardiac output and altered renal handling of sodium and water. Lack of thyroid hormone leads to reduced cardiac index, reduced contractility and relative bradycardia. Steroid replacement should be considered for these patients, as there is a risk of concomitant Addison’s being made worse with thyroid hormone administration or pituitary failure being the cause. Passive rewarming is recommended, but aggressive active rewarming can lead to vasodilatation and worsening hypotension.

Question 100: TTTTT

It is important to note the presence of fistulae; intravenous access and blood pressure cuffs should be sited away from any active fistulae. Patients who are dialysis dependent may be fluid restricted. This needs to be taken into account when planning perioperative fluid management. It is therefore also important to note the volume status of the patient and when they are normally dialyzed, including the date and time of their last session and when they should next be dialyzed. Elective surgery should usually be planned for the day between dialysis sessions. Patients with renal disease are at risk of developing peripheral neuropathy. This should be documented preoperatively, particularly if peripheral nerve blockade is planned, and care taken when positioning the patient to ensure no further nerve damage occurs perioperatively.

Question 101: TFFFT

Regional blocks in children are usually performed after general anaesthesia has been administered. Calculated maximum allowable dose is based on patient ideal body weight (IBW). Estimating the IBW has particular relevance to the high BMI child.

As the structures of interest in the paediatric patient are relatively superficial, a higher-frequency probe will be more suitable. Penile block performed using the landmark approach has reported failure rates of 4–8%. Systemic absorption of local anaesthetic when performing ilioinguinal and iliohypogastric blocks is higher after ultrasound guidance when compared to a landmark approach, and careful attention needs to be paid to avoid local anaesthetic toxicity.

Question 102: FTFFF

The commonest cause for liver transplant is posthepatitis C cirrhosis, though acute liver failure, e.g. post paracetamol overdose, will be prioritized for transplantation. Most cases involve the transplantation of a whole adult liver from a non-living donor and removing the diseased organ (orthotopic transplant). Portions of adult livers can be used in paediatrics and split livers allow one liver to be used for two patients. In living-donor liver transplantation, a portion of a healthy liver is transplanted from the donor to the patient. Venovenous bypass can be used to allow venous return from the lower part of the body whilst the liver is being removed and the transplant implanted. Reperfusion syndrome post reperfusion of the liver graft will cause massive cytokine release and typically is accompanied by a small drop in patient temperature. The anhepatic phase and need for massive transfusion are also reasons for further intraoperative hypothermia. Typically hypocalcaemia is more common during the anhepatic phase as a result of chelation with unmetabolized citrate. Hepatic artery thrombosis is a real concern in the first few days post transplantation, but occurs in 0.5–5% of patients. Thrombectomy can be attempted, but retransplantation may be needed.

Question 103: TTTTF

In June 2012, a panel of experts announced a new definition and severity classification system for ARDS. It is known as the ‘Berlin Definition’ and aims to simplify the diagnosis of ARDS and clarify the ambiguity of the old definition. Acute lung injury (ALI) does not exist anymore, but rather three degrees of severity according to the paO2/FiO2 ratio. Patients with a ratio of 200–300 would now have ‘mild ARDS’ rather than ALI. The severity of hypoxaemia predicts the mortality; being measured at 45% for severe ARDS with a paO2/FiO2 <100. The old definition did not define the ‘acute onset’, which caused confusion in cases of acute on chronic hypoxaemia. Patients with heart failure can still develop ARDS and hence there is no more need to exclude a raised PCWP. However, if there is no obvious cause for ARDS, heart failure shold be excluded as a cause of bilateral lung opacities and pulmonary oedema. The need for high PEEP predicts neither mortality nor clinical outcome.

Question 104: TTFTF

Cardiac arrests in the pregnant population are increasing in frequency and have a current incidence of around 1:30 000 pregnancies. This increase is probably caused by the increasing ages and morbidities of women now going through pregnancy. Perimortem caesarean section (PMCS) is now widely considered to be the best chance for a successful resuscitation of the mother, but should aim to be performed within 5 minutes of any arrest. This is, however, difficult to achieve practically. If PMCS is performed it should be done so where the woman is being treated and ideally not involve moving her to theatre. Cardiac arrests occur for a variety of reasons and can occur ‘out of the blue’ during an otherwise apparently normal pregnancy and labour. There is no change to standard ALS protocols for the defibrillation of patients.

Question 105: TFFTT

Lung volume reduction surgery (LVRS) is a viable option for a select group of emphysema patients. General inclusion criteria include:

  • Age <75 years

  • FEV1 between 15 and 35% of predicted

  • paCO2 <55 mmHg (7.3 kPa)

  • Prednisone requirement <20–1

  • PAPsys <50 mmHg

An ideal anatomical precondition for LVRS is a lack of homogeneity of the lung structure, where normal lung tissue and severely destroyed, over-distended tissue are present in the same lung. If it is homogeneous and the FEV1 is <20% there is high morbidity and mortality.

Question 106: FTFTT

There are five subtypes of atlantoaxial subluxation that may result from rheumatoid disease. Anterior subluxation is the most common and can affect up to 80% of patients. It results from the C1 vertebra moving anteriorly on the C2 vertebra. The transverse ligament and apical ligaments are destroyed as a consequence, risking spinal cord compression by the odontoid peg. Anterior subluxation is made worse by neck flexion, whereas posterior subluxation (affecting less than 5% of patients) is made worse by neck extension. In posterior subluxation, destruction of the odontoid peg may cause posterior movement of the C1 vertebra on the C2 vertebra. Vertical subluxation affects between 10 and 20% of patients and results from the destruction of the lateral masses of the C1 and C2 vertebrae. The cervicomedullary junction is then compressed by subluxation of the odontoid peg through the foramen magnum. Other subtypes of atlantoaxial subluxation include lateral⁄rotatory (affecting 5–10% of patients) and subaxial (rare).

Question 107: FFTFT

Speed of induction with inhalational agents is increased with high inspired concentration, increased alveolar ventilation, small FRC, low blood–gas partition coefficient, low cardiac output and second gas effect.

Second gas effect: administration of rapidly absorbed gas, such as nitrous oxide, given in high concentration together with a volatile agent of lower solubility produces an increasing alveolar concentration of the second agent thus promoting its absorption.

Question 108: FFTFT

All the volatile anaesthetic agents and suxamethonium are known to cause malignant hyperpyrexia (MH) in susceptible individuals. Nitrous oxide, however, does not, but should be used through a clean circuit, ideally via an anaesthetic machine reserved solely for MH patients. Ketamine and etomidate are safe to use. Patients are referred to the specialist centre in Leeds for fresh muscle biopsy that is exposed to halothane and caffeine. In susceptible patients muscle contraction occurs at lower concentrations than normal.

Question 109: TFFTF

A disposable four-electrode sensor is placed on the forehead. The frontal EEG signal is converted by an algorithm to a dimensionless index of the depth of anaesthesia. A reading between 0 and 100 is produced; zero represents no electrical activity, 100 being awake. The manufacturers recommend a number between 40 and 60.

BIS monitors are not validated for use in paediatrics, especially in those below the age of one, despite data suggesting EEG patterns in those over five are similar to adults.

Question 110: FFTFT

The most commonly used irrigation fluid in the UK is 1.5% glycine solution in water. The ideal irrigation fluid for use during TURP is clear, electrically non-conductive, non-haemolytic, non-toxic, sterile, not metabolized and cheap. No fluid that fulfils all these criteria exists; other irrigation fluids include mannitol 5% and sorbitol 3.5%. Glycine is an inhibitory neurotransmitter, it is metabolized in the liver and kidneys by oxidative deamination to glyoxylic acid and ammonia.

Question 111: FTTFF

The ductus arteriosus normally closes spontaneously at 24 hours (90% by 60 hours). Isolated PDA should always be treated. Treatment options depend on the size of the PDA. Small PDA can be treated by indomethacin to prevent infective endocarditis. Moderate PDA could be treated by device occlusion via catheterization to prevent pulmonary vascular disease. Very large PDA is treated by ligation through left thoracotomy, to treat heart failure. Left to right shunts lead to heart failure due to sequestration, while right to left shunts lead to cyanosis due to bypassing the pulmonary circulation.

Question 112: TTFTT

Fresh frozen plasma (FFP) must be transfused to an ABO-compatible donor due to the presence of antibodies in the plasma. The usual FFP starting dose is 10–15–1. For children up to the age of 16 born after 1995 it is obtained from the USA to reduce the risk of transmitting variant Creutzfeldt–Jakob disease. The FFP is also treated with methylene blue to inactivate viruses within the transfusion.

Question 113: FTFFF

The coeliac plexus is the main junction for autonomic nerves supplying the upper abdominal organs and consists of bilateral coeliac ganglia with a network of interconnecting fibres. The greater (T5–T10), lesser (T9–T11) and least (T11–T12) splanchnic nerves provide the major contributions to the plexus with input from the vagus and phrenic nerves also.

The plexus lies anterior to the aorta on either side of the body of L1 and posterior to the pancreas.

Alcohol is usually preferred to phenol for coeliac plexus block due its greater ability to diffuse through tissues. Diarrhoea and hypotension are common side effects and damage to the L1 nerve root may occur. Paraplegia, either through direct trauma or spasm of the artery of Adamkiewicz, has been quoted as 1 in 683 in one large case study.

Question 114: FTFFF

Intraoperative sedation and general anaesthesia using a scalp block for analgesia or regional anaesthesia as the sole technique are the anaesthetic options for an awake craniotomy. The term ‘awake craniotomy’ can be misleading, since varying levels of sedation or anaesthesia may be used during the procedure. The patient is always fully awake for the process of ‘cortical mapping’, during which lesion resection takes place, in order to minimize the risk of damage to the eloquent cortex.

Patient selection is vital to the success of this surgery; absolute contraindications include patient refusal, inability to lie still and lack of cooperation, e.g. acute confusion. Relative contraindications include an inability to lie flat, having a cough, anxiety, a language barrier and learning difficulties.

In order to anaesthestize the scalp, six nerves need to be blocked bilaterally, these are the supratrochlear, supraorbital, zygomaticotemporal, auriculotemporal, and the lesser and greater occipital nerves. The greater auricular nerve and third occipital nerve may need to be blocked in some patients, making a total of eight on each side at most. To block the greater auricular nerve, local anaesthetic is injected approximately 2 cm posterior to the auricle at the level of the tragus.

Question 115: FFTTF

Table 5.115.1 Burns depth

Nomenclature Traditional nomenclature Depth Clinical features
Superficial First degree Epidermis Painful, blanchable
Superficial–dermal Second degree Through epidermis to upper layers of dermis Painful, blisters, blanchable, hair follicles present
Deep-dermal Second degree Into deep dermis but not entire dermis ± Pain, does not blanch, some hair follicles present
Full thickness Third/fourth degree Extends to subcutaneous tissue Painless, black eschar, no hair follicles

Question 116: FFTTT

The key message is to not make any assumptions about what is acceptable, and clarify exactly what each individual will accept in the way of treatment. Some Jehovah’s Witnesses will accept cell salvage, but not all. The AAGBI has produced guidance on good practice and mandates that consultant surgeons and anaesthetists should be directly involved in the care of these patients. In an emergency, anaesthetists are obligated to treat Jehovah’s Witnesses, but this is not true for elective surgery. However, they must refer Jehovah’s Witnesses to a colleague who is willing to anaesthetize them. AAGBI guidance makes provision for Jehovah’s Witnesses to change their advance directive under regional anaesthesia. Tranexamic acid may be used to decrease bleeding.

Question 117: TFFFF

AAGBI day-case guidelines state specific cut-offs for age and BMI are not appropriate in assessing patients for day-case surgery suitability. Asthma, obesity and epilepsy may be well suited to the principles of regional anaesthesia and short-acting techniques, as well as minimal disruption to daily routine. Oral intake should be able to resume within a few hours.

Question 118: TTFTF

In advanced renal disease, gastric emptying is delayed, residual volume is greater and pH lowered. This increases the risk of aspiration and a rapid sequence induction may be considered where a history of reflux is elucidated. Platelet count is usually normal, however platelet function may be impaired with decreased adhesiveness and aggregation. Standard tests of coagulation are often normal, however bleeding time may be prolonged. Atracurium is often considered to be the muscle relaxant of choice in patients with severe renal disease owing to its termination of action by Hoffman degradation. However its duration of action may still be altered in renal disease owing to the alteration in ion concentrations such as magnesium, which can prolong the duration of block. So it is recommended, as for all patients, that neuromuscular monitoring is utilized to ensure adequate reversal prior to emergence and extubation. Patients with renal dysfunction are likely to be relatively fluid overloaded and hypoalbuminaemic. Hypoproteinaemic states result in an increased fraction of free drug within the plasma and thus a higher concentration of free drug with heavily protein-bound drugs. Hyperkalaemia is a common electrolyte abnormality seen in renal dysfunction.

Question 119: FTTFF

The evidence for a reduction in thromboembolic complications comes mainly from the orthopaedic literature. Studies in abdominal surgery have shown only a non-significant trend towards reduction of thromboembolic complications. Epidural anaesthetic blocks afferent nociceptive input and reduces pain and sensitization. This reduces the incidence of chronic postsurgical pain. The reduced stress response occurring with a regional technique results in less postoperative immunocompromise with consequent reduced potential for the spread of micrometastases at the time of surgery. When epidural analgesia is used intraoperatively in abdominal surgeries, it reduces the depth of anaesthesia required and hence would have a beneficial effect in reducing postoperative cognitive dysfunction. The debate on whether intrathecal blocks are safer when performed on awake or anaesthetized patients in unresolved. Available evidence is low-level and conflicting.

Question 120: FTFFF

Cardioplegia can be either blood- or crystalloid-based and typically has 20 mmol.l–1 potassium, 16 mmol.l–1 magnesium and procaine. Rapid infusion of approximately 1 l renders the heart asystolic. Cold cardioplegia at 4 °C provides further myocardial protection again ischaemia. Cardioplegia is instilled into the ascending aorta (as long as the aortic valve is competent) with a cross clamp on the aorta distal to the cardioplegia cannula, and runs into the coronaries. If the aortic valve is incompetent, the cardioplegia can be instilled directly into the coronaries or can be retrograde instilled via the coronary sinus. The aim is for the cold, hyperkalaemic solution to cause depolarization and arrest in diastole, which is a relaxed state and, therefore, at a cellular level, metabolically less active. On cardiopulmonary bypass, the blood is typically pumped through roller pumps which provide non-pulsatile flow. Pulsatile flow may be more physiological, but is more expensive to produce and has shown little benefit (ECMO circuits typically use centrifugal pumps). As blood comes in contact with a large prothrombotic surface in the bypass circuit, it is essential that the patient is fully heparinized, aiming for an ACT >400 s, prior to going on to cardiopulmonary bypass.

Question 121: FTTFT

Enteral feeding is more physiological and hence should be considered before parenteral feeding. Whilst it is almost impossible to overfeed using the enteral route, overfeeding is more common with the parenteral route. Enteral feed protects the gut against bacterial translocation and hence may reduce the risk of hospital-acquired infection. Postpyloric feeding should only be considered if gastric absorption is problematic. Although early feeding is advocated for its benefits, it is certainly better to underfeed than overfeed. It is not advisable to attempt to match the calculated caloric requirement. Aiming for a high caloric intake during the acute phase of critical illness may be associated with a less favourable outcome.

Question 122: TTFFF

Diabetes is increasing in incidence in the general population and there is also a corresponding increase in gestational diabetes. Risk factors for gestational diabetes include BMI over 30 (therefore routinely screened for), first-degree relative with diabetes or certain ethnic subgroups (South Asian, Black Caribbean). With pre-existing diabetes, management should ideally commence preconception to ensure the risks of pregnancy-associated diabetes are reduced. Risks include increases in miscarriage, pre-eclampsia, stillbirth and birth trauma. Whilst the manufacturers of oral hypoglycaemic agents suggest avoiding their use in pregnancy for safety purposes, NICE guidelines recommend they are used and believe them to have an appropriate safety record (Clinical Guideline 63). During labour, blood glucose should be maintained between 4 and 7 mmol.l–1. Where this is not possible or if the patient is a Type I diabetic, insulin and dextrose should be used. Whilst there is an increase in larger babies and an associated risk of birth trauma and obstetric interventions being required, epidurals are not specifically recommended to women with diabetes.

Question 123: FFTFF

Hypoxic pulmonary vasoconstriction (HPV) is a reflex contraction of vascular smooth muscle in the pulmonary circulation in response to low regional partial pressure of oxygen (paO2). Animal studies show that at low doses almitrine enhances HPV by a vasoconstrictor effect specific to pulmonary arteries. Iron attenuates HPV and also greatly reduces the enhanced response normally seen after prolonged hypoxic exposure. The common intravenous anesthetic agents show no inhibition of HPV.

Question 124: TFFFF

An advance directive made in the presence of a witness is a legally binding document. The patient must be over 18 years of age and have capacity at the time of writing. Patients are encouraged to carry a copy of their advance directive, as well as keeping copies with their general practitioner, family and friends. The directive must specify the decision applied to a specific treatment if the individual’s life is at risk and if any of these conditions are not met, the directive may be invalid. A doctor who knowingly breaches the terms of the directive may face criminal charges and referral to the General Medical Council. In an emergency where the patient cannot express their own wishes, an advance directive should be obtained as soon as possible. However, where such a directive cannot be obtained, life-saving treatment should not be withheld. The views of family and friends may be sought where possible, but no individual can refuse treatment on behalf of a patient. Involvement of the hospital legal team and Jehovah’s Witness liaison, and documentation of all discussions and decisions are paramount in such situations.

Question 125: FTTFT

Cleft lip and palate (CLP) is one of the commonest congenital deformities. Two-thirds involve the lip with or without the palate and the remainder the palate alone. Cleft lip is unilateral in 80% of cases and occurs on the left in over 70% of cases. CLP is more common in males. Chronic rhinorrhoea is common due to food reflux into the nasal passages and may present with recurrent URTI. Snoring, apnoea during feeds or protacted feeding time may indicate chronic airway obstruction. Difficult mask ventilation is unusual. Difficult laryngoscopy and intubation are strongly associated with retrognathia and bilateral cleft lip, due to protruding maxilla. Nasopharyngeal airways are effective and well tolerated and should be inserted in patients with high risk of postoperative airway complications before emergence. Avoid an oropharyngeal airway due to risk of disrupting the surgical repair.

Question 126: TTFFT

Suxamethonium apnoea occurs due to abnormal levels of functional plasma cholinesterase, coded for on chromosome 3. Plasma cholinesterase may be present, but not functional. In E1f:E1f there is reduced or no activity of plasma cholinesterase. In 1957 Kalow and Genest described mixing plasma with benzoylcholine and measuring the light emitted. They established that normal plasma and benzoylcholine emitted light at a specific wavelength. Dibucaine inhibits this reaction, and the percentage inhibition by a set amount of dibucaine compared to a reference value is known as the dibucaine number. Normal is 80 and reduced values reflect lack of functional plasma cholinesterase in plasma samples. Low dibucaine number is therefore a reflection of plasma cholinesterase abnormality. The risks of transfusing blood products outweigh the benefits. Given time, the neuromuscular block will reverse. Fresh frozen plasma should only be given in emergency situations following consultation with a consultant haematologist. Methotrexate is a cause of acquired plasma cholinesterase deficiency.

Question 127: FTFTT

Perioperative hypothermia is split into three portions:

  1. 1. Preoperative (up to an hour prior to arriving in theatre suite)

  2. 2. Intraoperative

  3. 3. Postoperative (up to 24 hours after entry to recovery area)

Core temperature should be measured preoperatively and warming devices should be employed if temperature falls below 36 °C. NICE guidelines on perioperative hypothermia suggest groups at high risk of inadvertent hypothermia include patients with:

  • ASA grade ≥II

  • Preoperative temperature <36 °C

  • Combined general and regional anaesthesia

  • Undergoing major or intermediate surgery

  • At risk of cardiovascular complications

Question 128: FFTFF

The trachea divides into the left and right main bronchi at the level of approximately T5. The right main bronchus is wider, shorter (approximately 2.5 cm) and more vertically angled when compared with the left. The right main bronchus gives off the right upper lobe bronchus (which divides into the apical, anterior and posterior segments), the right middle lobe bronchus (which divides into the lateral and medial lobes), and the bronchus of the apical segment of the lower lobe (which divides into superior, anterior basal and lateral basal). The lower lobe bronchus continues downwards giving off the medial, anterior, lateral and posterior basal segments. The left main bronchus is longer (approximately 5 cm), narrower and more obliquely angled than the right. The left main bronchus gives off the left upper lobe bronchus, this divides into the superior division (which divides into the apical, posterior and anterior segments) and the lingular bronchus (divides into superior lingular and inferior lingular segments). The left lower lobe bronchus gives off the apical, anterior basal, medial basal (although can arise with the anterior basal), lateral basal and posterior basal.

Question 129: FTFFT

This neonate’s most likely diagnosis is tetralogy of Fallot. This is due to the presence of cyanosis (secondary to an over-riding aorta), a murmur over the pulmonary area (suggesting a right ventricular outflow tract obstruction) and evidence of right ventricular hypertrophy on the ECG. The degree of the right ventricular outflow obstruction (RVOT) will dictate the speed of onset of his cyanosis. Within 72 hours 90% of all PDAs will close, leading to significant cyanosis in cases of severe RVOT obstruction. Treatment should aim to improve pulmonary blood flow. This could be achieved medically by prostaglandin infusion until a more definitive shunt is established surgically. In the modified Blalock–Taussig operation, an anastomosis is established between the subclavian and the ipsilateral pulmonary artery.

Question 130: TFTTF

The following events are applicable for all incidents that occur on or after 1 April 2015 when providing NHS care:

  • Wrong site surgery

  • Wrong implant/prosthesis

  • Retained foreign object post procedure

  • Mis-selection of a strong potassium-containing solution

  • Wrong route administration of medication

  • Overdose of insulin due to abbreviations or incorrect device

  • Overdose of methotrexate for non-cancer treatment

  • Mis-selection of high-strength midazolam during conscious sedation

  • Falls from poorly restricted windows

  • Chest or neck entrapment in bedrails

  • Transfusion or transplantation of ABO-incompatible blood components or organs

  • Misplaced naso- or orogastric tubes

  • Scalding of patients

Wrong site surgery includes a surgical intervention performed on the wrong patient or the wrong site. It includes wrong level spinal surgery and wrong site block unless being undertaken as a pain control procedure. Retention of a foreign body post procedure does not include items inserted before the procedure that are not subject to the formal counting/checking process, such as a throat pack inserted in the anaesthetic room. Misplacement of naso- or orogastric tube itself is not a never event; however, failing to recognize misplacement and administering feed down a misplaced tube is.

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Oct 24, 2020 | Posted by in ANESTHESIA | Comments Off on Chapter 5b – Clinical Anaesthesia Answers
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