Plasma catecholamine changes during excision of pheochromocytoma.

Sequential changes in plasma norepinephrine (NE) and epinephrine (EPI) concentration were correlated with changes in blood pressure and cardiac rate in 14 patients undergoing surgery because of pheochromocytoma. All patients had elevated preoperative plasma catecholamine levels that increased during induction of anesthesia, intubation, and skin incision, but mean values did not become significantly higher than preoperative values until tumor manipulation. Episodes of hypertension were associated with increased plasma catecholamine levels, and plasma catecholamine levels and blood pressure decreased dramatically after tumor resection. NE and EPI were usually secreted simultaneously, but release of either NE or EPI alone occurred on some occasions. There were marked variations in the concentration ratio of NE to EPI in plasma at different periods of observation, which suggests that pheochromocytomas release varying amounts of catecholamines in a random fashion. Studies of the effect of the duration of preoperative preparation on intraoperative blood pressure, pulse rate, and cardiac arrhythmias failed to demonstrate that treatment for 14 days or longer was more effective than treatment for 4 to 7 days. Neither the brief nor the prolonged period of therapy prevented development of severe hypertension during tumor manipulation.