The Journal of Thoracic and Cardiovascular Surgery, Vol 77, 267-276, Copyright © 1979 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Pharmacologic antagonism of beta-adrenergic blockade in dogs. I. Hemodynamic effects of isoproterenol, dopamine, and epinephrine in acute propranolol administration
GJ Avery 2d, HM Spotnitz, EA Rose, JR Malm and BF Hoffman
Hemodynamic effects of isoproterenol, dopamine, and epinephrine were
studied before and after acute beta-adrenergic blockade in 16 open- chest,
anesthetized mongrel dogs. Beta blockade was induced with 1 mg. per
kilogram of intravenous propranolol. Cardiac output measurements were
obtained by thermal dilution, and pressure recordings were obtained in the
right ventricle, pulmonary artery, left atrium, left ventricle, and aorta.
Derived parameters included stroke volume, pulmonary and systemic vascular
resistances, and peak left ventricular dP/dt. In the presence of
propranolol, epinephrine became a lethal drug in large doses and did not
increase cardiac output in standard doses. Dopamine, in 25 to 50 mcg. per
kilogram per minute doses, increased arterial pressure and systemic
resistance; cardiac output was diminished compared with dopamine, 10 mcg.
per kilogram per minute, prior to propranolol, as a result of increased
resistance and decreased LV contractility. Isoproterenol, 0.6 to 0.9 mcg.
per kilogram per minute, 15 to 20 times standard dosages, had moderately
positive inotropic effects and increased cardiac output. Left ventricular
systolic pressure with isoproterenol after propranolol was reduced when
compared with effects of smaller doses prior to propranolol. These
observations suggest that none of the catecholamines studied would be
optimal for circulatory support in heart failure in the presence of
propranolol. The present results define a pharmacologic basis for design of
appropriate drug combinations for circulatory support in beta- blocked
animals.
