Premedication and adjuncts to general anaesthesia

Premedication is used to prepare the patient for general anaesthesia. The objective is to reduce feelings of anxiety and lightly sedate the patient. In addition, drugs may be used to prevent parasympathetic effects of some general anaesthetics. 

Four main groups of drugs are used as premedication and as adjuncts to general anaesthesia sedatives antimuscarinic drugs muscle relaxants and analgesics. Table 12.2 shows actions and examples of drugs used to supplement general anaesthesia. 

short-acting sedatives may be used to allay anxiety and produce some sedation and amnesia. 

Oral benzodiazepines, such as diazepam or midazolam are commonly used. These drugs also reduce muscle tone, which is useful during surgery. They have no analgesic effect, so may be used together with opioid analgesics. 

As a side effect benzodiazepine sedatives produce a degree of respiratory depression. 

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Premedication is intended to prevent the parasympathetic effects of anaesthesia (excessive salivation and bronchial secretion and a reduction in heart rate) and to reduce anxiety or pain. Premedication and adjuncts to general anaesthesia are discussed further on page 234. 

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