Mechanism of Decreased Venous Return

Recent work published by this laboratory in the subhuman primate has demonstrated that the primary cause of the decrease in mean systemic arterial pressure following a lethal injection of endotoxin is a decrease in venous return.¹However, a marked difference in response to endotoxin is observed in monkeys in contrast to dogs. In the former, a gradual fall in mean systemic arterial pressure is observed, and there is neither demonstrable pooling in the hepatosplanchnic bed nor loss of circulating blood to extravascular compartments.¹⁻⁵ The cause of the decrease in venous return in the primate has not been determined. A previous study did not differentiate between a decrease in venous return due to peripheral pooling or failure of cardiac contractility.¹The cardiac output in some human patients shows a steady decline,⁶,⁷although there is no evidence of primary cardiac failure in man⁶or the nonhuman primate.