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.