Monitoring of hepatic venous oxygen saturation for predicting acute liver dysfunction after Fontan operations

Acute liver dysfunction after Fontan operations may result from inadequate hepatic perfusion along with low cardiac output and high central venous pressure. We monitored hepatic venous oxygen saturation in 15 patients after Fontan operations to determine whether oxygen saturation predicts the occurrence and severity of acute liver dysfunction. We measured oxygen saturation from hepatic venous blood samples every 4 to 5 hours for at least 24 hours after the operation and used the mean hepatic venous oxygen saturation value for the first 24 hours after the operation to analyze the relationship between oxygen saturation and hepatic function. As indices of hepatic function, we measured serum alanine aminotransferase, total bilirubin, blood lactate (arterial, hepatic venous, and the difference between them), and the arterial ketone body ratio (the ratio of aceto-acetate to beta-hydroxybutyrate). For alanine aminotransferase and bilirubin, we used the maximal values during the first week in the analysis, and for blood lactate and ketone body ratio, we used the mean values for the first 24 hours after the operation. Significant broken-line regression relationship existed between mean hepatic venous oxygen saturation and hepatic function indices (alanine aminotransferase, total bilirubin, and blood lactate). The interpretation of these relationships is that hepatic indices are constant above the critical mean hepatic venous oxygen saturation values but are correlated with mean hepatic venous oxygen saturation below critical points in the range of 21% to 26%. Thus a hepatic venous oxygen saturation value below about 25% during the first 24 hours after a Fontan operation predicts the occurrence and the severity of acute liver dysfunction. We suggest that monitoring hepatic venous oxygen saturation is useful for management of critically ill patients after Fontan operations.