Halothane anaesthesia does not modify the cardiovascular response to phenylephrine in man.

Conflicting results exist regarding the ability of halothane to alter the vascular response to alpha 1 adrenergic agonists in animals. Because data from humans are lacking, we studied the haemodynamic response to phenylephrine (PHE) in eight patients about to undergo coronary artery bypass surgery before and during halothane anaesthesia. After obtaining baseline measurements in patients while awake, the responses to PHE infusion at 30, 40, and 50 micrograms.min-1 were determined. New baseline measurements were made following stabilisation during anaesthesia with halothane, one per cent inspired in oxygen, prior to surgical incision. Then the responses to identical PHE doses were measured again. Halothane did not influence the cardiovascular response to PHE: there was no dose-response shift for any cardiovascular variable. No arrhythmias or signs of ischaemia were observed. We conclude that one per cent halothane anaesthesia does not attenuate PHE-induced vasoconstriction in man.