CARDIOVASCULAR REACTIVITY IN ANAEMIC DOGS

Abstract

Cardiovascular responses to the intravenous administration of adrenaline were measured as a means of assessing cardiovascular reactivity in intact anaesthetized dogs, before and at 3 hours and 3 days after the rapid production of anaemia by a dextran-for-blood exchange. Three types of experiments were carried out. In experiments A and B, 2.0 and 5.0 μg/kg of adrenaline (respectively) were injected intravenously before and at both periods after exchange, and the changes in arterial blood pressure were assessed. In experiment B the changes in the arterial plasma concentration of potassium and sodium were also measured. In experiment C, several cardiovascular parameters, including cardiac output (Fick method), arterial pressure, and heart rate, were measured before and at the end of a 15-minute infusion of adrenaline in a dose of 0.2 μg/kg minute. In all three experiments, evidence of a reduced cardiovascular response to adrenaline was found when the dogs were anaemic; and in experiment B the adrenaline-induced hyperkalaemia and hyponatraemia were found to be significantly reduced during anaemia.The mechanism of the hyporeactivity to adrenaline during anaemia is not clear, but may include changes in blood volume, electrolyte disturbances, and severe anoxia.