Perioperative gastric tonometric PCO2 and intramucosal pH in patients undergoing liver transplantation

Background: Extensive research has focused on the role of insufficient gastro-intestinal perfusion and inflammatory activation in the development of organ dysfunction during critical illness. In patients undergoing liver transplantation, portal and caval vein clamping leads to gastro-intestinal and lower extremity venous congestion during the anhepatic phase, and studies suggest that gastro-intestinal perfusion may be compromised. This study was performed to investigate gastro-intestinal perfusion in patients undergoing liver transplantation. Methods: In 16 patients undergoing liver transplantation, perioperative gastric tonometry with determination of tonometric PCO₂, tonometric-arterial PCO₂ gradient and intramucosal pH were performed. Blood gases were obtained simultaneously from the arterial and portal vein blood. Results: Tonometric PCO₂ was 4.6 (4.2/5.3) kPa preoperatively and increased to 5.6 (4.5/6.0) kPa during the anhepatic phase (P<0.01), while the tonometric-arterial PCO₂ gradient increased from -0.3 (- 0.5/0.0) kPa preoperatively to 0.7 (0.3/1.2) kPa during the anhepatic phase (P<0.01). Intramucosal pH decreased to 7.27 (7.21/7.32) u during the anhepatic phase (P<0.01, compared to preoperatively). The portal vein PCO₂ was not significantly different from arterial PCO₂ or tonometric PCO₂ at any measurement point. Conclusion: This study demonstrates that clinical liver transplantation is associated with gastro-intestinal perfusion in the range of aerobic metabolism. The results do not support the presence of gastro-intestinal perfusion in the range of anaerobic metabolism.