Comparative Haemodynamic Effects of Glucagon and Isoprenaline in the Early Postoperative Period in Cardiac Surgery

In order to study the haemodynamic effects of isoprenaline and glucagon in the immediate postoperative period, 16 patients who had single or multiple valve replacement or coronary artery bypass grafts were investigated. Measurements of cardiac index, stroke index, heart rate, arterial and right atrial mean pressures were made either before, during, or after the administration of both drugs. With the doses used, the inotropic effects of both drugs are similar, while the chronotropic action is statistically higher during isoprenaline infusion than after glucagon administration. This fact explains the greater increase in cardiac index after isoprenaline administration. Mean arterial pressure shows no significant changes after either drug, while right atrial mean pressure decreases significantly. Peripheral vascular resistance remained mostly constant. The activity of glucagon injected as a single bolus seems to be maximal 10 to 15 minutes after the injection and dissipates about 30 minutes later. The ideal dose of isoprenaline is between 0.8 and 2 mug/min. Within this range, the inotropic effect is maximal and the chronotropic and bathmotropic effects are limited. Above 2 mug/min, cardiac index and stroke index decrease, and arrhythmias become more frequent.