Ventilatory strategy during liver transplantation: implications for near-infrared spectroscopy-determined frontal lobe oxygenation

Background: As measured by near infrared spectroscopy (NIRS), cerebral oxygenation (S(c)O(2)) may be reduced by hyperventilation in the anhepatic phase of liver transplantation surgery (LTx). Conversely, the brain may be subjected to hyperperfusion during reperfusion of the grafted liver. We investigated the relationship between S(c)O(2) and end-tidal CO(2) tension (EtCO(2)) during the various phases of LTx. Methods: In this retrospective study, 49 patients undergoing LTx were studied. Forehead S(c)O(2), EtCO(2), minute ventilation (VE), and hemodynamic variables were recorded from the beginning of surgery through to the anhepatic and reperfusion phases during LTx. Results: In the anhepatic phase, S(c)O(2) was reduced by 4.3% (95% confidence interval: 2.5–6.0%; P < 0.0001), EtCO(2) by 0.3 kPa (0.2–0.4 kPa; P < 0.0001), and VE by 0.4 L/min (0.1–0.7 L/min; P = 0.0018). Conversely, during reperfusion of the donated liver, S(c)O(2) increased by 5.5% (3.8–7.3%), EtCO(2) by 0.7 kPa (0.5–0.8 kPa), and VE by 0.6 L/min (0.3–0.9 L/min; all P < 0.0001). Changes in S(c)O(2) were correlated to those in EtCO(2) (Pearson r = 0.74; P < 0.0001). Conclusion: During LTx, changes in S(c)O(2) are closely correlated to those of EtCO(2). Thus, this retrospective analysis suggests that attention to maintain a targeted EtCO(2) would result in a more stable S(c)O(2) during the operation.