Hemodynamic effects of continuous norepinephrine infusion in dogs with and without hyperkinetic endotoxic shock.

We compared, at constant preload maintained by polygeline (gelatin) infusion, the hemodynamic effects of continuous infusion of norepinephrine (0.5, 1, and 1.5 micrograms/kg X min) in anesthetized dogs with and without hyperdynamic endotoxic shock. In both groups, norepinephrine infusion increased systolic, diastolic and mean aortic BP, cardiac index, stroke index, index of myocardial contractility, and mean pulmonary artery pressure. No significant change in right atrial pressure, left ventricular end-diastolic pressure, heart rate, systemic vascular resistance, or pulmonary vascular resistance was observed. Oxygen consumption index and oxygen extraction ratio remained unchanged. Increases in systolic aortic BP were dose-related, whereas maximal effects on other variables were obtained at 0.5 to 1 microgram/kg X min. The rise in aortic pressure resulted from an increased cardiac index but not from an increased systemic vascular resistance. Stroke index increased as contractility improved. The slight alpha-adrenergic effect of continuous, low-dose norepinephrine infusion did not impede the beneficial effects of the marked beta-adrenergic stimulation on cardiac function. The combination of these two effects improved hemodynamic disturbances of hyperdynamic endotoxic canine shock.