Effect of regional heating of upper body on the liver blood flow in rats.

The changes in rat liver blood flow, caused by hyperthermia, were studied. The liver region of rats was heated with Thermotron IV, an experimental capacitive heating device utilizing 8 MHz RF, and the liver blood flow was measured with radioactive microspheres. Portal venous blood flow slightly decreased during 30 min heating of the liver at 41 degrees C and returned to control level after the heating. When the liver was heated at 43 degrees C, portal venous blood flow decreased initially by about 20%, but gradually returned to control level during the 30 min heating. Hepatic arterial blood flow increased slightly during 30 min heating at 41 degrees C and 43 degrees C. Because almost 85% of the liver blood flow is portal venous blood flow, the change in total liver blood flow paralleled the change in portal venous blood flow. During regional heating of the liver the cardiac output declined significantly, which may account in part for the decrease in splanchnic blood flow, and thus portal venous blood flow. Changes in vascular resistance in the viscera may be another reason for the decrease in portal venous blood flow during heating of the liver region.