A comparative study of the hemodynamic actions of histamine and endotoxin

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Abstract
The present study is a logical extension of earlier work with the aim of evaluating the relative role of histamine in endotoxin shock. A variety of experiments on 91 dogs were carried out in which the hemodynamic actions of histamine, a histamine releaser (48/80), and endotoxin were compared. Results indicate definite similarities of action in a number of vascular parameters: a) an early increase in portal venous pressure coincident with a decrease in venous return, pooling, and a rapid decrease in systemic arterial pressure and b) eventual increases in foreleg resistance, foreleg small vein pressure, leg weight, and circulating hematocrit. The early responses to endotoxin are greatly altered when 48/80 is administered prior to endotoxin which suggests a common underlying mechanism for the action of each agent. Histamine appears to serve as a triggering device for the sustained release of adrenergic-like agents which superimpose their effects on those of histamine. These findings offer additional evidence for the early release of histamine in endotoxin shock.