Baroreflex participation of cardiovascular response to E. coli endotoxin

The purpose of this experiment was to evaluate the effects of the arterial baroreceptor buffering capacity on cardiovascular parameters during hypotension caused by E. coli endotoxin in anesthetized dogs. In the control group, mean blood pressure and cardiac output fell significantly from 104 +/- 10 mmHg to 63 +/- 7 mmHg and 1.17 +/- 0.16 l/min to 0.67 +/- 0.08 l/min, respectively, 60 min after intravenous injection of endotoxin (1 mg/kg). Central venous pressure also decreased significantly after the injection. Total peripheral resistance and portal vein pressure increased significantly immediately after the injection, and then returned toward baseline levels. The time course of changes in these five cardiovascular parameters after the injection of endotoxin was the same as that in dogs with sino-aortic denervation. Following the injection of endotoxin, stroke volume and left ventricular dP/dt fell significantly in both control and denervated dogs; however, these decreases in the denervated group were significantly greater. These findings suggest that the arterial baroreceptors may play a role in the poor compensatory response to hypotension induced by endotoxin, at least, in the cases of mean blood pressure, cardiac output, total peripheral resistance, central venous pressure, and portal vein pressure.