Hyperbilirubinemia after cardiac operation. Incidence, risk factors, and clinical significance

Three hundred and two consecutive patients who had undergone cardiac operation for various cardiac lesions were studied prospectively to evaluate the incidence, risk factors, and the associated mortality of postoperative hyperbilirubinemia after cardiopulmonary bypass. Concentrations of the serum total (conjugated and unconjugated) bilirubin, alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, alkaline phosphatase, albumin, globulin, and serum haptoglobin were measured before the operation and again on the first, second, and seventh postoperative days. Postoperative hyperbilirubinemia was defined as occurrence of a serum total bilirubin concentration of more than 3 mg/dl in any measurement during the postoperative period. Logistic regression was done to identify possible risk factors for postoperative hyperbilirubinemia. Overall incidence of postoperative hyperbilirubinemia was 35.1%; the incidence of postoperative hyperbilirubinemia was higher in patients whose valves were replaced with mechanical prostheses than in those without prostheses (p < 0.00001). In patients with postoperative hyperbilirubinemia, 70% of the increase of total bilirubin on the first postoperative day came about from an increase in unconjugated bilirubin. Serum haptoglobin decreased significantly at the same time (p < 0.01). Development of the postoperative hyperbilirubinemia was associated with a higher mortality (5.6% versus 0.5%, p < 0.01) and higher frequency of use of intraaortic balloon counterpulsation, especially for patients in whom the highest postoperative total bilirubin occurred after the first 2 days. The numbers of valves replaced, preoperative right atrial pressure, and preoperative total bilirubin concentration are the significant risk factors that, in combination, correctly predict the occurrence of postoperative hyperbilirubinemia in 80% of the patients. We concluded that postoperative hyperbilirubinemia results mainly from an increase in unconjugated bilirubin and is associated with higher mortality, especially for patients in whom highest postoperative total bilirubin occurred late after operation. Patients with the higher preoperative right atrial pressure and total bilirubin level who then underwent multiple valve replacement procedures are at greater risk for development of postoperative hyperbilirubinemia.