Hemodynamic Changes in Adrenalectomized Dogs

Abstract

Hemodynamic studies were conducted in trained, unanesthetized dogs before and after complete adrenalectomy. Three days after complete adrenalectomy there were consistent and significant decreases in cardiac output, stroke volume and mean arterial pressure, and increases in heart rate and total peripheral resistance. Intravenous infusions of dextran during adrenal insufficiency consistently increased cardiac output, stroke volume and arterial pressure, and decreased total peripheral resistance. Various programs of steroid therapy failed to restore completely the normal hemodynamic pattern, i.e., heart rate, blood pressure and stroke volume were restored partially or completely, but cardiac output remained low. However, definitive conclusions about the hemodynamic effects of steroid therapy will require additional data. In control dogs, studied repeatedly during a period of approximately 2 years, there was no significant tendency for the hemodynamic values to change with time. We conclude that the major hemodynamic alteration in acute adrenal insufficiency is a reduction in cardiac output and stroke volume, but the basic mechanism underlying this change is unknown. Our results are compatible with the thesis that myocardial function is deficient when there is adrenal insufficiency.