Anaesthetic Management with Morphine in Phaeochromocytoma

Morphine was used as the principal anaesthetic agent for five patients undergoing resection of phaeochromocytoma, and changes in plasma catecholamines were monitored. Phenoxygenzamine (0.5 mg X kg-1 X day-1) was orally given one week before operation. After premedication with hyoscine (0.4 mg) and diazepam (20 mg) of meperidine (50 mg), anaesthesia was induced with an infusion of morphine (1 mg X kg-1) over 30 min and maintained with diazepam, nitrous oxide and oxygen. Pancuronium was used as the muscle relaxant. In three of the five patients, blood pressure transiently rose (ranging from 15 to 60 mg) following orotracheal intubation, but vasodilators were not required. In two of the three, plasma norepinephrine increases were 1.1 and 1.3 ng X ml-1. In the other two patients, whose blood pressure was stable, the change in plasma norepinephrine was 0.1 and 0.7 ng X ml-1. After reaching a peak at the time of ligation of drainage vein from the tumour, plasma catecholamines rapidly decreased to the preoperative levels, but the blood pressure was well maintained in all cases. Ventricular arrhythmias did not occur despite the increased levels of endogenous catecholamines. These findings suggest that morphine can be used as an alternative anaesthetic agent during operation for phaeochromocytoma and that exaggerated pressor responses to morphine (when given slowly) seem not to occur in phaeochromocytoma.