Effect of portal venous pressure on portal venous inflow and splanchnic resistance

The effect of portal venous pressure on the prehepatic splanchnic vascular resistance was studied in 12 anesthetized and 2 unanesthetized dogs. Over the range of portal pressures used, splanchnic resistance was found to increase linearly with increases in portal pressure. The relationship was similar in the conscious animal and was not altered by treatment with a ganglionic blocking drug. Splenectomy had the effect of increasing the pressure dependence of the remaining splanchnic resistance. The significance of the response with regard to control of total hepatic blood flow is discussed. It is suggested that, because of this portal splanchnic response, alterations in the total hepatic blood flow may be more effectively accomplished by changes in portal venous rather than hepatic arterial resistance. This response may also be partly responsible for the greatly decreased portal venous flow found in patients with hepatic cirrhosis.