CHAPTER 11 Procedural sedation and analgesia
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:
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:
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):
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:
In order to perform PSA safely in the ED according to evidence-based recommendations, there are seven key questions which need to be considered:
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):
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:
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.
The mnemonic MMAP can be used to assess the patient’s anatomy for possible difficult laryngoscopy.
AMPLE history
The AMPLE mnemonic is useful in your initial patient assessment.
