THE HEMODYNAMIC-EFFECTS OF INTRAVENOUS BOLUS DOSES OF MEPERIDINE IN CONSCIOUS SHEEP

The hemodynamic effects of 100, 200, and 300 mg of meperidine injected intravenously were studied in five chronically instrumented adult ewes. The maximum rate of increase of left ventricular pressure was decreased, respectively, by 27.4% +/- 3.9%, 37.5% +/- 5.6%, and 31.9% +/- 13.0%, and recovery occurred by 5, 8, and 0.5 min, respectively. Mild central nervous system stimulatory effects (agitation) were observed in three of five sheep at 200 mg and moderate effects (rigor and jumping movements) were observed in four of five sheep at 300 mg. These doses also produced increases in heart rate (43%-64%) and mean arterial blood pressure (17%-27%). At these doses, cardiac output was increased for 0.5 min by approximately 25% without changes in stroke volume and left ventricular stroke work. Coronary blood flow was increased by 44%-81% for 0.5 min. We conclude that, in unpremedicated sheep, meperidine has a brief direct negative inotropic effect on the myocardium, but that at larger doses this is overridden by stimulatory central nervous system (CNS) and indirect hemodynamic effects.