sedation and analgesia

CHAPTER 11 Procedural sedation and analgesia



Lara Goldstein



Introduction


Pain is one of the most common reasons for patients to present to the ED and it is a reasonable expectation that their pain will be swiftly and skilfully managed. Similarly, patients in the ED often require diagnostic or therapeutic procedures that may cause apprehension or pain, or both. Patient dissatisfaction often relates to poor management of pain and anxiety or an inappropriate approach to the management of procedures. Emergency physicians are well qualified to administer procedural sedation and analgesia (PSA) while simultaneously monitoring the respiratory and cardiovascular status of both critically ill or injured patients and those with less dramatic but nonetheless painful conditions. Adequate analgesia and sedation for diagnostic and therapeutic interventions should be the standard of care in the ED.


The provision of safe and effective sedation and analgesia (for procedures or otherwise) is an important part of Emergency Medicine practice. The failure to adequately treat a patient’s pain can have negative consequences, potentially affecting later psychological and physiologic responses and behaviours, especially in children. Appropriately treating pain and anxiety decreases patient suffering, facilitates medical interventions, increases patient/family satisfaction, improves patient care, and may improve patient outcome.


Providing effective and safe PSA in the ED is dependent on a number of factors:


• Appropriate patient selection and assessment.

• Appropriate selection and use of pharmacologic and non-pharmacologic agents.

• An appropriate environment for the procedure.

• Appropriate monitoring during and after the procedure.

• Appropriate post-procedure and pre-discharge evaluation.

There are many drugs and various non-pharmacologic modalities that can be used for PSA. The selection of a particular agent or modality is influenced by many factors, including patient characteristics (age, diagnosis, other illnesses, allergies) and the procedure to be performed (painful or painless, duration, depth of sedation required). Appropriate experience, staffing, equipment, monitoring and assessment are critical for safe and effective PSA.


Some of the myths that surround the use of analgesia in the ED negatively impact on the adequate and appropriate use of analgesic agents to treat pain and to be used as part of PSA. Some of these myths include:


• Children don’t feel pain.

• Children don’t remember pain.

• Patients can get addicted to opiates after a single dose.

• Opiates administered to patients can obscure the diagnosis of underlying pathology.

• PSA should be done only by anaesthetists.


What is PSA?


PSA involves the administration of sedative or dissociative agents with or without analgesic agents to induce a state that allows the patient to tolerate unpleasant or painful procedures. During the procedure, the patient maintains control of their airway and breathing because the protective airway and breathing reflexes are preserved. While PSA causes the patient to have a depressed level of consciousness, it allows them to maintain cardiorespiratory function.



Depth of sedation


Four levels of sedation have been defined by the American Society of Anesthesiologists (ASA):


• Minimal sedation (formerly anxiolysis). This is a state during which patients respond normally to verbal commands. Cognitive function and coordination may be impaired but ventilatory and cardiovascular functions are unaffected.

• Moderate sedation (formerly conscious sedation). This is a state of depressed consciousness during which patients respond purposefully to verbal or light tactile stimulation while maintaining protective airway reflexes. No cardiovascular or ventilatory assistance is required. In order to carry out potentially unpleasant procedures, moderate sedation is generally the goal.

• Deep sedation. This is a level of consciousness during which patients are not easily aroused and may need airway and/or ventilatory assistance. They may respond purposefully to repeated or painful stimulation. Cardiovascular function is usually maintained.

• General anaesthesia. This is a state of drug-induced loss of consciousness in which patients are not arousable and therefore require intervention for airway protection. They often have impaired cardiorespiratory function needing support.

These somewhat arbitrary categories are part of a continuum through which the patient may drift to a lighter or deeper sedative state. Individuals may also vary in their responses to the initial dose of a specific sedative with a resulting lighter or deeper sedation than intended. Physicians administering PSA should be proficient in the skills needed to rescue a patient at a level greater than the desired level of sedation. If moderate sedation is desired, the practitioner should be able to provide the skills needed to perform deep sedation. If deep sedation is required, the practitioner should be competent in the airway management and cardiovascular support involved in providing general anaesthesia.


Dissociative sedation, as produced by ketamine, is another form of sedation where a trance-like state is induced which provides analgesia and amnesia whilst leaving protective airway reflexes and cardiovascular stability unaffected. It cannot be categorised into any of the above levels of sedation.



How to perform PSA


The main aims for this chapter on PSA are to provide, or revise, some basic principles that can be used to improve patient care using an evidence-based approach. The physician should be able to ensure:


• Patient safety.

• Patient comfort.

• Physician comfort (i.e. decreased anxiety regarding the procedure and the patient’s discomfort).

• An increased chance of successful completion of the intended procedure (although PSA does not necessarily guarantee that the procedure will not fail!).

In order to perform PSA safely in the ED according to evidence-based recommendations, there are seven key questions which need to be considered:


1. What are the human resources required to safely perform PSA in the ED?

2. How should patients be assessed before performing PSA?

3. Is fasting necessary before initiating PSA?

4. What equipment is required to perform PSA?

5. What monitoring is required to perform PSA in the ED?

6. How should respiratory status be assessed during PSA?

7. Can ketamine, midazolam, fentanyl, propofol and etomidate be safely administered to adults and children by emergency physicians in the ED?

So where do we start and how do we apply this in creating a plan for PSA? It’s as easy as ABC (Fig. 11.1):


A– Assessment

B– Back-up/Background

C– Consent

D– Drugs

E– Equipment and monitoring

F– Fasting

G– Guidelines for discharge

image

Fig. 11.1 Procedural sedation plan checklist.



Assessment


The assessment of the patient pre-PSA requires some additional information over and above the basic history and examination that has probably already been performed. Focus on the following:


• ASA physical status classification.

• Airway assessment.

• AMPLE history.

Children under the age of 2 years should generally receive PSA from a specialist with expertise in the management of infants.



ASA physical status classification


The ASA stratifies patients who will be undergoing anaesthesia according to a physical status classification (Table 11.1).


Table 11.1 ASA physical status classification


















Class 1 Normally healthy patient
Class 2 Mild systemic disease
Class 3 Severe systemic disease, but not incapacitating
Class 4 Severe systemic disease that is a constant threat to life
Class 5 Moribund, not expected to survive without the procedure

The limitation of this classification is that it was developed using general anaesthesia guidelines. Its utility in the emergent PSA application has not yet been formally established. Patients who fall into ASA class 3 or above have been shown to have a greater risk of sedation-related adverse events. It is generally accepted that patients in ASA classes 1 and 2 can safely undergo procedural sedation in the ED. ASA class 3 patients can be considered for ED procedural sedation – the potential risks and benefits should be taken into account, e.g. an awake patient with a supraventricular tachycardia requiring sedation for electrical cardioversion.



Airway assessment


In many ED scenarios the urgency of airway management does not always allow for the evaluation of a patient’s airway in advance. This sometimes leads to the uncomfortable finding of an unanticipated difficult airway for which you are not prepared (unless you consider that every airway is going to be difficult!).


PSA can be considered to be semi-elective. It is therefore essential to assess your patient’s airway prior to the performance of the procedure in order to have the relevant back-up equipment/medical staff available should the patient require airway and ventilatory management. This assessment should include predicting difficult bag–mask ventilation and intubation. Awareness of abnormal airway anatomy (e.g. micrognathia or macroglossia), the presence of dental appliances or false teeth, a full beard, facial piercings, limited neck mobility, a short neck or history of stridor may all predict a difficult airway. The procedure should then be deferred to the operating theatre. The Mallampati score given for the view on mouth opening can also be added to the assessment process.


A useful aide-mémoire to recall the potential causes of difficult bag–mask ventilation is BOOTS.


Beard/Body piercings

Obesity

Old age (>65 years old)

Teeth abnormalities/Toothless

Snoring/Stridor/Syndromes

The mnemonic MMAP can be used to assess the patient’s anatomy for possible difficult laryngoscopy.


Mallampati score. Class I and II generally correlate with easy direct laryngoscopy, while III and IV with difficult laryngoscopy.

Measurements 3-3-1. Likely intubation difficulty can be envisaged if the patient can fit less than 3 of their own fingers in the hyomental area; less than 3 fingers between their upper and lower teeth (mouth opening); and has less than 1 cm of jaw protrusion (the ability to protrude the lower teeth anterior to the upper teeth).

Atlanto-occipital extension. If cervical spine precautions are not required, assess the patient’s ability to flex the neck at the lower part of the cervical spine and extend the head on the upper cervical spine. (PSA should not be performed on a patient with a potential cervical spinal injury except under exigent circumstances.)

Pathology of the upper airway. Assess for evidence of upper airway obstruction resulting from medical causes (e.g. angioedema, tumours, epiglottitis) or traumatic causes (e.g. burns, penetrating neck trauma). The presence of stridor might identify such pathologies.


AMPLE history


The AMPLE mnemonic is useful in your initial patient assessment.


Allergies. It is important to enquire about allergies to medication and/or previous adverse events when the patient has been sedated or undergone anaesthesia.

Medication. Medication that is currently being used must be established. Both allopathic and homeopathic medications may cause drug interactions. The use of chronic medication can reveal a diagnosis that may not have been mentioned previously. Also check whether the patient has taken/been given analgesia/other medication for the current problem prior to hospital arrival.

Past medical history. This would have hopefully been covered in the initial patient evaluation but serves as a reminder.
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Jul 4, 2016 | Posted by in ANESTHESIA | Comments Off on sedation and analgesia

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