The use of labetalol in anaesthesia.

1 Observed and possible roles for the use of labetalol in anaesthesia are reviewed. 2 When used together with halothane inhalation anaesthesia, satisfactory conditions are achieved for safe hypotensive anaesthesia: (a) Labetalol and halothane have additive hypotensive effects. (b) The usual dose of labetalol is 25 mg intravenously together with 1% halothane. (c) The duration of hypotension can be controlled in the presence of halothane; withdrawal leads to rapid recovery of pre-surgery blood pressure. (d) High doses of halothane (3%) with labetalol predispose to the myocardial depressant effects of halothane and undesirable reductions in myocardial performance. 3 As it is now seen to be important to reduce the blood pressure before anaesthesia and surgery in hypertensive patients, then labetalol is likely to be satisfactory either by the intravenous route for immediate reduction or for less urgent reduction of raised arterial pressure by the oral route. 4 It is known that anaesthesia (for example, laryngoscopy) and surgery provoke hypertensive responses which are particularly undesirable in the patient with pre-existent myocardial ischaemia. In such cases it is likely that previous treatment with labetalol will satisfactorily modify unwanted hypertensive and cardiovascular responses.