Veno-venous bypass in liver transplantation: heparin-coated perfusion circuits reduce the activation of humoral defense systems in an in vitro model

We studied the effects of bypass circuit surface heparinization on kallikrein-kinin, coagulation, fibrinolytic and complement activation in a closed model system for simulating veno-venous bypass (VVBP) in liver transplantation (OLT). The circuits were identical to those in routine use during clinical OLT in our institution. Fresh whole human blood diluted 1:2 with Ringer's acetate was circulated at non-pulsatile flow (2 L/min) and at a constant temperature (37.5°C) for 12 hours. In 10 experiments, the entire inner surface of the circuits was coated with end-point attached heparin (HC). In the remaining 10, non-treated PVC tubings were used (NC). Components of the plasma kallikrein-kinin, coagulation, fibrinolytic and complement systems were analyzed using functional techniques (chromogenic peptide substrate assays) and enzyme immunoassays at baseline, 3 and 12 h. Significant activation of the initial (C3bc) and terminal (TCC) components of the complement system was found in both the NC and HC groups after 3 and 12 h: C3bc: NC: baseline = 4 (3.5-7.7), 3 h = 17.3* (12.5-27), 12 h = 31* (17.7-63.6), HC: baseline = 4.9 (3.2-6.8), 3 h = 9* (6-14.4), 12 h = 13.7* (7.4-18.1). TCC: NC: baseline = 0.4 (0.2-0.6), 3 h = 5* (0.8-11.9), 12 h: 13.1* (4.2-25.7). HC: baseline = 0.5 (0.1-0.6), 3 h = 0.6* (0.1-0.8), 12 h = 1.2* (0.3-2) AU/ml; median and range, (*: p