The effect of alpha-adrenergic blockade on cardiac performance and tissue oxygen delivery during excision of pheochromocytoma.

To establish criteria for administration of the optimal dose of alpha-adrenergic receptor blocking drugs, we studied cardiac performance and tissue oxygen tension in three patients who underwent excision of pheochromocytoma. Subcutaneous oxygen tension was measured by the method of Niinikoski and Hunt. Cardiac function was assessed by thermodilution cardiac output, systemic and pulmonary arterial blood pressures, and continuous two-dimensional transesophageal echocardiography of a cross section of the left ventricle at the level of the papillary muscles. Despite large changes in cardiac output and systemic, pulmonary, and wedge pressures, intraoperative tissue oxygen tensions and ejection fractions remained normal (even at times of peak catecholamine excretion and very abnormal wedge pressures). Studies of healthy animals that received no alpha-adrenergic receptor blocking drugs showed major decrements of tissue oxygen in response to modest doses of epinephrine. We conclude that progressive administration of alpha-adrenergic receptor blocking drugs does not absolutely protect the patient from major changes in blood pressure during operation for pheochromocytoma, but that cardiac performance and oxygen supply to the tissues are unimpaired.