Estimation of functional liver reserve in patients before cardiac surgery using antipyrine plasma clearance test

Hyperbilirubinemia is not uncommon and is sometimes fatal after valvular surgery. One important cause of it is a poor functional liver reserve, however, conventional tests reflect hepatic blood flow and do not offer precise evaluation of the pure functional liver reserve. Antipyrine has particular pharmacological properties, and its plasma clearance represents quantitatively the functional capacity of the liver. In this study, we measured antipyrine plasma clearance in cardiac surgical patients and evaluated the feasibility of using this parameter as a predictor of the risk of postoperative hyperbilirubinemia.

The plasma clearance of antipyrine was measured preoperatively in 40 cardiac patients undergoing mitral and/or tricuspid valvular surgery and its relations with hemodynamics or postoperative course were studied.

Antipyrine clearance in preoperative patients was 0.365+/-0.175 (mean +/- SD) ml/min/kg, lower than the normal range (0.405+/-0.04 ml/min/kg), and showed no correlation with cardiac index, while the plasma disappearance rate of indocyanine green depended on the cardiac index. The maximum postoperative total bilirubin level showed significant correlation with antipyrine clearance (r=-0.699); this correlation coefficient was greater than that with indocyanine green (-0.477). The correlation was more prominent in patients with cardiac dysfunction. Furthermore, antipyrine clearance showed significant predictability of the duration of ICU stay.

Antipyrine clearance provides a precise estimate of functional liver reserve which is independent of hemodynamics and predicts the risk of postoperative hyperbilirubinemia in preoperative cardiac patients.