Hepatic vascular response to elevated intraperitoneal pressure in the rat.

The rat is increasingly being used to study the physiological response to elevated intra-abdominal pressure (IAP) during laparoscopic surgery. Although decreased portal venous flow associated with the elevated IAP has been reported in large animals, little information is available in rats. Furthermore, the relative blood flow changes in the hepatic artery and portal vein have not been reported. Therefore, this study was performed to elucidate the change in systemic and splanchnic circulation, including hepatic arterial and portal venular flow, during pneumoperitoneum in rats. Sprague-Dawley rats were assigned into either a ventilated or nonventilated group and then subjected to various levels of IAP (0, 5, 10, and 20 mm Hg) using carbon dioxide gas. At each pressure, both cardiac output and splanchnic organ flow were determined using fluorescent microspheres. There was no obvious hemodynamic difference between the ventilated and nonventilated groups. Mean arterial pressure and cardiac index were significantly lower with 20 mm Hg of IAP compared to 0 mm Hg in both groups. Flow to the spleen, stomach, duodenum, total intestine, and portal vein was all decreased by increasing IAP (P < 0.05 at 20 mm Hg compared to 0 mm Hg) and was significantly correlated to the decrease in cardiac index. However, the hepatic arterial flow was relatively preserved throughout all levels of IAP, suggesting activation of the hepatic arterial buffer response. We conclude that the decreased splanchnic flow during pneumoperitoneum largely depends on the decreased cardiac index. Hepatic artery flow, however, is selectively preserved and may provide protection for liver function during sustained elevations in IAP.