[The importance of high-dose alpha-receptor blockade for blood volume and hemodynamics in pheochromocytoma].

This prospective clinical study evaluates the possible beneficial effects of increased phenoxybenzamine dosage in the preoperative treatment of patients with pheochromocytoma. For this purpose total blood volume (TBV) prior to and after treatment with phenoxybenzamine and hemodynamic changes during surgery were determined in two groups of patients: group I (n = 12) received a mean dosage of 140 mg, group II (n = 12) 270 mg/day. The mean TBV in group I showed no changes after treatment with phenoxybenzamine, while the TBV in group II increased by 5.6 ml/kg body weight, corresponding to an increase in plasma volume (PV) of 10.2%. These changes were not significant, however. The intraoperative vasodilator requirement for the treatment of catecholamine induced hypertension during tumor manipulation was significantly less for group II: total nitroprusside administration averaged 8.7 mg in group I and 0.8 mg in group II (P less than 0.0005). Patients in group I received a total of 2.6 mg nitroglycerin compared with only 0.5 mg for patients in group II (P less than 0.005). In conclusion, preoperative treatment of patients with pheochromocytoma with increased dosages of phenoxybenzamine is beneficial to intraoperative management by decreasing hemodynamic instability due to tumor manipulation and following resection. This treatment was effective for preventing complications such as excessive tachycardia, cardiac arrhythmias, hypertensive crises, or left ventricular failure.