Mechanism of the hypertensive effect of droperidol in pheochromocytoma.

Droperidol is used in the anaesthetic management of pheochromocytoma because of its sedative, anti-dysrhythmic and alpha-adrenoreceptor blocking properties. However, droperidol when used in pheochromocytoma, has been reported to produce a paradoxical hypertensive response. In vitro experiments with perfused rabbit ear arteries using a histochemical fluorescence technique, showed droperidol to be an inhibitor of noradrenaline uptake into sympathetic nerve endings, and this uptake inhibition was dose related. The uptake inhibition effect did not, however, produce pressor changes in experiments simulating pheochromocytoma in cats. The hypertensive response to droperidol may be due to blockade of presynaptic alpha-adrenoreceptors and this possible mechanism of action is discussed.