Studies on the elimination of bilirubin pre-operatively in patients with mitral valve disease

This study looked at the hypothesis that patients with mitral valve disease have a reduced capacity to eliminate bilirubin prior to surgery for valve implantation. Radiolabelled bilirubin was administered as a bolus and as a steady state i.v. infusion so that its incorporation into plasma bilirubin, and the latter's elimination after the load, could be measured. Patients with mitral valve disease (10) and aortic valve disease (10), in NYHA functional classes II-III, with total bilirubin concentration < 26 mumol.l-1, were studied. The plasma conjugated bilirubin increased significantly during infusion with radiolabelled bilirubin; radioactivity also increased after 3-5 min both in mitral and aortic valve diseased patients. After termination of the infusion the decrease in plasma-free bilirubin concentration followed an exponential decay curve with a rate constant of 0.0101 +/- 0.0013 (mean +/- SD) and 0.00419 +/- 0.00130 for patients with aortic valve disease and mitral valve disease (P < 0.05) respectively. The rate constant correlated significantly with cardiac index (r = 0.55) (P < 0.01), and inversely with bilirubin concentration (r = -0.57) (P < 0.01). Patients with advanced mitral valve disease and normal bilirubin concentration demonstrated normal uptake. However, conjugation of bilirubin in the liver, with a diminished ability to eliminate a bilirubin load, indicated a functional block in the elimination of conjugated bilirubin, most likely related to a reduced liver flow.