Correlation between Changes in End-Tidal Carbon Dioxide Concentration and Cardiac Output during Inferior Vena Cava Clamping and Unclamping in Living-donor Liver Transplantation

Background To test the hypothesis that low end-tidal carbon dioxide tension encountered during anhepatic phase in liver transplantation is related to hemodynamic status rather than ventilatory status, and can be used to predict the change in cardiac output during anhepatic phase. Methods We retrospectively analyzed and compared data, included end-tidal carbon dioxide tension (ETCO₂), arterial blood pressure, heart rate, central venous pressure, cardiac output, cardiac index, and stroke volume, before and after inferior vena cava clamping, and 0, 5, 10, 30 minutes during the anhepatic, and 5 minutes after the release of IVC cross clamp during the reperfusion phase, with paired Student t test, repeated measurement, and linear regression. P <.05 was regarded as significant. Results The cardiac output and ETCO₂ decrease significantly after clamping the inferior vena cava and increase concomitantly after unclamping. There is a positive correlation between the changes in % in cardiac output and ETCO₂ (Pearson coefficient r = 0.741). Conclusion The changes in ETCO₂ can be used to predict the changes of the cardiac output in % when cardiac output monitoring is not available. Before unclamping of the IVC, mild hyperventilation is suggested to prevent excessive increase in PaCO_2.