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Intravenous ketamine anaesthesia has been used by the British army in the field for many years. A recognised problem has been the unpredictable recovery profile this produces. We anaesthetised 28 ASA 1 patients using a standard British military technique. At termination of the anaesthetic, half of the patients were given a physostigmine/glycopyrronium mixture and half were given the equivalent volume of saline 0.9%. There was a significant difference between the two groups with regard to recovery times (p < 0.001). There was no significant difference with regard to other variables. In trauma anaesthesia the improved recovery profile from the use of physostigmine following ketamine anaesthesia may lead to earlier evacuation of the patient.

The arterial hypertension of ketamine is prevented by verapamil, a calcium ion antagonist. This indicates that ketamine is a direct myocardial stimulant acting by increasing the availability of calcium across the cell membranes of the myocardial and the Purkinjé systems. The positive chronotropic action of ketamine is not reversed by verapamil. Both the chronotropic and the inotropic effects of ketamine are prevented by halothane which acts partly by increased vagal tone and partly by what appears to be a verapamil-like depression of calcium availability. Ketamine blocks the reflex sympathetic response of the peripheral blood vessels to surgical stimuli. The site of the block within the sympathetic reflex arc has not been identified. It is not at the alpha adrenoceptor level. The clinical implications of the findings have been discussed.

Labetalol, a new antihypertensive agent with alpha and beta-adrenoceptor blocking properties was given to five series of patients anaesthetised with a ketamine infusion. in an attempt to reduce the cardiostimulatory effects of ketamine. It proved very effective in controlling the chronotrophic action of ketamine but was unreliable in controlling the rise in blood pressure. In doses of 1.0 mg kg-1 given with tubocurarine, it was not without side effects.

In an attempt to attenuate the cardiostimulatory effects of ketamine, a number of drugs were given individually, or in combination, to fit adults undergoing body surface operations, either before or aftera ketamine induction of 1 mg kg-1 followed by an infusion of 1 mg ml-1. Of these, practolol, phentolamine, practolol-phentolamine, phentolamine-practolol, promethazine, hexamethonium, procainamide and verapamil were unacceptable. Labetalol, in doses of 0.5 mg kg-1 and 1.0 mg kg-1, proved to be the most promising drug and is worthy of further study.