Effects of intraabdominally insufflated carbon dioxide and elevated intraabdominal pressure on splanchnic circulation: An experimental study in pigs

Background: Intraabdominally insufflated carbon dioxide (CO₂) during laparoscopy may have a specific effect on splanchnic circulation that may be unrelated to the effects of increased intraabdominal pressure alone. Therefore, the influences of insufflation with CO₂ versus air on splanchnic circulation were compared. Methods: Pigs were chronically instrumented for continuous recording of mesenteric artery, portal venous, inferior vena cava, and pulmonary arterial blood flow and portal venous pressure. After induction of anesthesia, CO₂ or air was insufflated in 14 and 10 pigs, respectively. With the pigs in the supine position, intraabdominal pressure was increased in steps of 4 mmHg up to 24 mmHg by graded gas insufflation. Results: During air insufflation, mesenteric artery vascular resistance was unchanged, whereas mesenteric arterial blood flow decreased with increasing intraabdominal pressure. Shortly after CO₂ insufflation to an intraabdominal pressure of 4 mmHg, mean arterial pressure, mesenteric arterial blood flow, and mesenteric arterial vascular resistance were increased by 21%, 12% and 9%, respectively. Subsequently, with the onset of CO₂ resorption in the third minute, mean arterial pressure declined to baseline values and mesenteric arterial vascular resistance declined to 85% of baseline values, whereas mesenteric arterial blood flow continued to increase to a maximum of 24% higher than baseline values. At steady-state conditions during CO₂ insufflation, mesenteric arterial blood flow was increased up to an intraabdominal pressure ≤ 16 mmHg but decreased at higher intraabdominal pressures. Conclusions: In contrast to air insufflation, intraabdominal insufflation of CO₂ resulted in a moderate splanchnic hyperemia at an intraabdominal pressure ≤12 mmHg. At higher intraabdominal pressure values, pressure-induced changes became more important than the type of gas used.