Intraoperative management of phaeochromocytoma with sodium nitroprusside.

Sodium nitroprusside (SNP) is a powerful, peripherally acting hypotensive agent with a rapid onset but short duration of action. It is highly effective for hypertensive episodes in patients with a phaeochromocytoma and may be used safely with adrenoceptor-blocking agents. Two cases are described that illustrate its effectiveness in this condition, even in the presence of exceptionally high circulating concentrations of catecholamines. A simple and reliable regimen for preparing these patients for surgery may be based on oral adrenoceptor-blocking medication (phenoxybenzamine and propranolol) to provide "background" hypotensive and antiarrhythmic cover. SNP by infusion is then used as the principal intraoperative hypotensive agent, dysrhytmias being controlled with additional intravenous propranolol if required.