[Cardiovascular adaptability to acute hypercalcemia in the dog. The role of peroperative myocardial ischemia].

Since the hemodynamic consequences of acute hypercalcemia are altered by numerous interferences we have evaluated the role of peroperative myocardial ischemia on the adaptability to rapid calcium increment. Twenty-two dogs served as control and 16 were submitted to 1 hour of myocardial ischemia along with topical myocardial cooling. Each animal was equipped with blood flow transducer positioned around the ascending aorta and with central venous and aortic catheters. During each study 0.90 mEq of calcium was rapidly injected and hemodynamic data were recorded until base-line resetting. This experimental protocol was carried out 3 hours postoperatively and then daily during one month. Base-line hemodynamic data indicated the presence of myocardial failure in the experimental group in the immediate postoperative period only. Rapid calcium administration elicited transient positive inotropic response, widening of the arterial pulse pressure, reflex bradycardia and no evidence of peripheral vasoconstriction. In the early postoperative period (3 hours after surgery) the failing myocardium is more sensitive to the inotropic effect of hypercalcemia. Twenty-four hours after surgery both groups of animals have the same hemodynamic response to this stress; thereafter for both groups this response gradually decreased and finally stabilized by the 6th to 10th day after surgery. Acute hypercalcemia bears hemodynamic consequences that are amplified early after peroperative myocardial ischemia. However in long term this surgical component widely used clinically does not interfered with the cardiovascular adaptability to this pharmacological stress.