Multiple choice questions
1
Crystalloids, colloids, blood and blood products and substitutes
Which of the following is true regarding the interaction between infused fluids, volume status and interstitium?
- A.
In a hypovolaemic state the positive pressure applied by the compressed interstitium prevents fluid filtration
- B.
During sepsis much of the administered intravenous fluids will be redistributed to the interstitium
- C.
Fluid accumulation in the interstitium is independent of the rate of fluid administration
- D.
Following intravenous infusion 0.9% saline stays significantly shorter than Ringer’s lactate solution in the interstitium
- E.
Volume expansion of the interstitium decreases with increasing mean arterial pressure
2
Regional anaesthetic techniques for paediatric surgery
Which of the following are true regarding performing a caudal block and its complications in children?
- A.
The success rate of caudal block with landmark based technique is similar to that using an ultrasound
- B.
The needle is inserted through the sacral hiatus which is a result of an incomplete fusion of the lamina of S5
- C.
In children older than 2 years the cephalad spread of local anaesthetic becomes unpredictable
- D.
Clonidine is licensed to be used as an adjunct for local anaesthesia for caudal block
- E.
A large volume of local anaesthetic may be injected into the caudal space to provide a block for supra-umbilical surgery
3
Procedural sedation for children: principles and practice
Which of the following are true regarding procedural sedation in children?
- A.
Chloral hydrate is widely used for paediatric sedation outside of the operating theatre due to low prevalence of adverse reactions
- B.
Ketamine is unsuitable as an analgesic adjunct due to concerns regarding emergence phenomena
- C.
UK National Institute for Health and Care Excellence guidelines recommend a specialist to undertake sedation in children with sleep disorders
- D.
It is recommended that children should have fasted for at least 6 hours prior to procedural sedation for an urgent procedure in the emergency department
- E.
Guidelines from the Academy of Royal Colleges mandate that a sedationist needs to have a dedicated assistant while providing procedural sedation
Single best answer
4
A 4-year-old obese boy with autism and asthma is listed for an adeno-tonsillectomy for sleep-disordered breathing. Which of the following statements is true about the perioperative pain management of this child?
- A.
Per-rectal paracetamol may be suggested as the bio-availability is similar between oral and rectal routes
- B.
This boy may develop higher plasma morphine concentrations when compared to a similar age child of normal weight
- C.
This child may be sent home safely with codeine for postoperative pain control
- D.
Celecoxib may be a better option compared to diclofenac due to his history of asthma
- E.
Preoperative ibuprofen may increase the risk of bleeding intraoperatively
5
Which one of the statements given below is true regarding various models of total intravenous anaesthesia in children?
- A.
The Marsh model is the preferred model in a haemodynamically unstable child
- B.
Minto remitentanil target-controlled infusion is a validated model suitable for children below 12 years
- C.
With the Eleveld model for propofol there is a long gap with no infusion following the initial bolus
- D.
The Kataria model in children is an extrapolation of the Schnider model in adults
- E.
Remifentanil infusion models based on micrograms/kg/minute use the lean body mass instead of actual body weight
Answers
1. Correct Answers: A, B, E
2. Correct Answers: B, C
3. Correct Answers: A, C
4. Correct Answer: B
Paracetamol is used as an anti-pyretic and analgesic agent. It is available in oral (tablet, elixir), rectal and intravenous preparations. Paracetamol is an effective analgesic for mild to moderate pain, with level I evidence showing that it decreases opioid requirements after major and minor surgery in children. Paracetamol has good oral bioavailability (>90%) and less predictable rectal bioavailability (25–98%).
Non-steroidal anti-inflammatory drugs (NSAIDs) are anti-inflammatory, anti-pyretic and analgesic agents that have proven efficacy in the management of postoperative pain in children. NSAIDs (e.g. ibuprofen, diclofenac) inhibit both COX-1 and COX-2 isoenzymes. Selective COX-2 inhibitors have subsequently been produced (celecoxib, parecoxib, rofecoxib) with the aim to decrease the incidence of unwanted adverse effects seen with non-selective NSAIDs. Evidence has shown that NSAIDs can safely be used in healthy children across multiple surgical specialties without an increase in postoperative bleeding rates. The role of coxibs in children remains unclear and advantages over commonly used non-selective NSAIDs have not been fully demonstrated.
Codeine is hepatically metabolized primarily via the CYD2D6 enzyme which is subject to genetic polymorphisms and inter-individual variability in function. Intermittent or poor metabolizers with reduced or no CYP2D6 activity are found in approximately 46% of children in the UK and will show little or no analgesic effect from codeine. Conversely, ultra-rapid metabolisers have more than two times CYP2D6 activity and are at increased risk of sedation and respiratory depression, especially in breastfeeding neonates, infants and those with underlying sleep apnoea. Paediatric use of codeine, especially following adenotonsillectomy, has been associated with mortality, particularly in ultra-rapid metabolizers of the CYP2D6 enzyme.
5. Correct Answer: C
Both Paedfusor and Kataria models use weight as the parameter for scaling the compartments V1-3. In the Paedfusor model, the weight is additionally used to calculate the elimination constant K10. It is an extrapolation of the Marsh modelling, and scales V1 in a non-linear fashion above the age of 12 years.
The Marsh model ignores age (it has a minimum programmable age of 16 years) and uses an initial bolus related to a V1 which is much larger than other adult models – this leads to a larger initial bolus. It is important to be mindful of this if using total intravenous anaesthesia in haemodynamically unstable patients.
The Eleveld model provides the first allometric scaling of infusion dosing; that is, relating the size of the patient to the physical characteristics of their age and physiology. It also incorporates compartment allometry, and a maturation model for clearance (CL) based on post-menstrual age. It is best utilized as an effector-site model. It also assumes a low Ke0 (distribution to a theoretical effect site compartment). This results in a prolonged gap with no infusion following the (relative to other models, large) initial bolus.
The Minto model is a three-compartment model that can be programmed to target effect site (cet) or plasma site (cpt). It has an age cut-off of 12 years and a minimum weight of 30 kg.
Remifentanil can be run as an infusion (micrograms/kg/minute). The disadvantage of this is that it uses only actual body weight (ABW) to predict the pharmacokinetics of remifentanil in an individual patient. LBM is a more accurate variable.
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