Arterial Inflow Into the Mesenteric and Hepatic Vascular Circuits During Hemorrhagic Shock

¹ From the Department of Physiology, Western Reserve University, School of Medicine, Cleveland, Ohio

Mesenteric artery and hepatic artery flows were studied in dogs during a standardized hemorrhagic shock procedure. Both flows decreased in response to hemorrhage, with development of greater vascular resistance in the hepatic artery circulation. Toward the end of the hypotensive period vascular resistance in the mesenteric artery often entered a declining phase, correlated with an increase in portal venous pressure, but hepatic artery resistance increased somewhat further. On transfusion, mesenteric artery flow increased rapidly, often exceeding the control values. Portal pressure doubled, and mesenteric resistance decreased to values less than control for about 30 minutes. This may represent a phase of pooling and trapping of blood in the capillaries and venules of the mesenteric circulation favored by reduced inflow resistance, and increased outflow resistance. This was followed by a phase of increased mesenteric resistance which often persisted until the demise of the animal, although it decreased in some animals during the terminal stage. Following transfusion, hepatic artery flow increased more gradually than mesenteric artery flow and reached a peak about 1 1/2 hours post-transfusion, at a time when flow in the mesenteric artery was markedly reduced and its resistance was maximal. The mechanism of this reciprocity of flow and resistance is discussed and its relevance to the interpretation of the hepatic artery flow changes in shock is considered.