Pre-existing Factors Affecting Recovery

Abstract

The type and dosage of drugs given as premedication can influence recovery from anaesthesia in many ways:

• 1. A relative overdose of depressant drugs relative to the patient’s age and weight is one of many causes of a delayed return of consciousness (p. 93). This is particularly true when large doses of narcotic analgesic agents are given to the frail and elderly, but relative overdose may also follow benzodiazepine, phenothiazine or hyoscine (scopolamine) administration. Reversal of the effects of opiates can be achieved by intravenous naloxone (0.1–0.4 mg) or doxapram (50–100 mg).

  Benzodiazepines can be reversed by the recently introduced specific antagonist flumazenil. Like naloxone, it should be administered slowly until the desired effect is obtained. The usual dose is 300–600 µg.

• 2. Long-acting premedicating agents whose action may persist into the postoperative period, especially if the surgical procedure is brief. Examples include droperidol and lorazepam.

• 3. Anti-sialogogues. When anti-sialogogues have been omitted, recovery may be accompanied by excessive salivation, especially following intubation, oral surgery and certain premedications e.g. lorazepam. Frequent suction may be necessary to maintain a clear airway and to prevent coughing and laryngeal irritation.