Hemodynamics of Dogs in Histamine Shock, with Special Reference to Splanchnic Blood Volume and Flow

Abstract

After the subcutaneous injection of histamine (3 mg/kg), changes in splanchnic and systemic circulation were studied in splenectomized dogs under sodium pentobarbital. The estimated splanchnic blood flow (BSP clearance and extraction) decreased by 67%. The extent of the decrease was almost the same as that for the mean arterial pressure; thus the splanchnic vascular resistance remained unchanged. This unchanged splanchnic resistance was ascribed to a combination of arteriolar dilatation and hepatic venoconstriction, and the latter was indicated by the increase in the wedged hepatic venous pressure in the face of a decreased flow. The ciculating splanchnic blood volume (equilibration technique) was not significantly changed after histamine, but there was a decrease in the splanchnic cell percentage. Therefore, the evidence indicates that during histamine shock there was a shift of blood from the hepatic veins to the capillaries, rather than a pooling of blood in the splanchnic circulation. The decrease in the splanchnic cell percentage was about the same as the decrease in the overall cell percentage. The venoconstriction in the hepatic circulation and probably also that in the other circuits contributed to a reduction in venous return. The cardiac output (indicator dilution method) decreased by an average of 51%. The total peripheral resistance decreased by an average of 39%. The drastic and persistent arterial hypotension in histamine shock was due to decreases in both the cardiac output and the peripheral resistance.