Anesthesia for patients with insulinoma treatment with oral diazoxide

Abstract

Insulinoma, first described in 1924 by Harris, is a beta islet cell tumor of the pancreas that produces marked hypoglycemia resulting from sudden, episodic, and massive release of endogenous insulin. Avoidance of hypoglycemia is the cornerstone of medical management in patients with this disorder prior to surgical excision of the tumor. Fraser first described hyperinsulinism during anesthesia and the intraoperative and postoperative episodes of hypoglycemia responding to rapid administration of glucose intravenously. The importance of rapid, frequent intraoperative blood glucose determinations has been emphasized by many authors, and the prophylactic use of 50 per cent glucose to maintain moderate intraoperative hyperglycemia has been suggested. Anesthetic techniques previously reported for surgical removal of insulinoma include nitrous oxide-relaxant techniques, and methoxyflurane. Colella and Vandam recommended diethyl ether as the anesthetic of choice since it has the theoretical advantage of releasing catecholamines which enhance hepatic glycogenolysis and inhibit insulin release. Use of enflurane for maintenance of general anesthesia for insulinoma surgery has not previously been published. Diazoxide (Proglycem®), a nondiuretic benzothiadiazine derivative with peripheral vascular dilating activity, directly inhibits release of pancreatic insulin and has proven to be a major advance in the medical management of patients with insulinoma. No discussion of anesthetic implications for patients taking oral diazoxide preoperatively exists. We describe two cases where enflurane was utilized to anesthetize patients for surgical removal of insulinomas, where oral diazoxide was used preoperatively to combat perioperative hypoglycemia. In addition, limiting the intraoperative infusion of 5 per cent dextrose containing solutions to 2 ml.kg-1.h is suggested, and a possible drug interaction between diazoxide and thiopental is proposed.