5 Anaesthesia—Sedation

Procedural sedation and analgesia (PSA) is used in ENT surgery to reduce pain and anxiety and to provide amnesia for surgical procedures. PSA involves the administration of sedatives or dissociative agents, with or without analgesics, to induce an altered state of consciousness that allows the patient to tolerate painful or unpleasant procedures while preserving cardiorespiratory function.

5.1 Depth of Sedation

Four levels of sedation are defined by The American Society of Anesthesiologists (ASA).

1. Minimal sedation: A drug-induced state during which the patient responds normally to verbal commands. Cognitive function and physical co-ordination may be impaired, but airway reflexes, ventilatory and cardiovascular functions are unaffected.

2. Moderate sedation: A state where a purposeful response to verbal commands either alone (conscious sedation), or accompanied by light tactile stimulation, is maintained. The airway is normally unaffected and spontaneous ventilation is adequate.

3. Deep sedation: A state where the patient cannot easily be aroused but responds purposefully to repeated or painful stimulation. It may be accompanied by clinically significant ventilatory depression. The patient may require assistance to maintain a patent airway, and may require positive pressure ventilation.

4. General anaesthesia: A controlled state of unconsciousness accompanied by a loss of protective reflexes, including loss of the ability to maintain a patent airway or to respond purposefully to physical stimulation or verbal command.

5.2 Use of PSA in ENT Surgery

Where possible, PSA may be considered in patients unfit for general anaesthesia (GA), for patients who express a preference for it, and for procedures when patient co-operation is useful, for example vocal cord medialisation. When considering this technique, it is imperative to evaluate the surgeon’s operative needs and to select the patients carefully. PSA will not be suitable for some, nor provide adequate operating conditions for many ENT procedures.

Middle ear surgery: Tympanoplasty, mastoid-ectomy, myringotomy, grommet insertion and cochlear implantation can be performed under local anaesthesia and sedation. Under local anaesthesia, many patients experience discomfort including a sense of noise, anxiety, dizziness, backache, claustrophobia or earache. Sedation may help alleviate some of these symptoms.

Nasal surgery: Functional endoscopic sinus surgery, septoplasty, balloon dilation of frontal sinus duct, dacryocystectomy and reduction of fractured nasal bones can all be successfully performed under local anaesthesia with sedation using various intravenous sedatives and/or analgesics.

Head and neck surgery: Excision of head and neck skin lesions, lip lesions, oral, oropharyngeal lesions and laryngeal procedures might lend themselves to PSA.

5.3 Pre-Operative Assessment

The very young and old, frail, morbidly obese, those with obstructive sleep apnoea (OSA), pulmonary and cardiac disease, and patients with significant kidney or liver disease are, amongst others, at higher risk of complications when receiving sedation. These patients may be best served by an anaesthetist administering their PSA. Patients should be carefully assessed for the presence of predictors of difficult bag-mask-ventilation, for example dysmorphic facial features, the presence of a beard, significant cachexia, morbid obesity, history of snoring or limited neck extension. Again, it may be prudent for an anaesthetist to manage these patients. Any patient receiving anything more than minimal sedation should be fasted to reduce the risk of aspiration of stomach contents into the airway. Fasting guidelines for general anaesthesia should be followed.

5.4 Patient Consent

For elective procedures, information about the procedure and intended level of sedation should be explained to the patient well in advance, along with an explanation of all material risks and alternative management options (see Chapter 14, Consent and Capacity). The information should emphasise that during sedation patient is likely to be aware, and may have a recall, but that the intention is to improve comfort and reduce anxiety. On the day of procedure, it should be stressed that sedation is not GA and sedation should be described again from patient’s perspective using terminology given in the NAP5 report on accidental awareness under general anaesthesia (AAGA). The rate of reports of AAGA following sedation was as high as after GA. These represent failure of communication between the anaesthetist and patient.

5.5 Monitoring

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