The significance of heparin-coated veno-venous bypass circuits in liver transplantation

We studied the effects of veno-venous bypass (VVBP) circuit surface heparinization on the activation of the plasma defence systems (coagulation, fibrinolysis, kallikrein-kinin and complement) and leukocyte activation in a prospective randomized study in 20 patients during and 1 day after liver transplantation (OLT). To our knowledge, this is the first study of this kind where the possible benefits of surface heparinization of the VVBP circuit in OLT have been investigated. Twenty patients were randomized to either heparin-coated (HC) VVBP equipment or to otherwise identical noncoated (NC) circuits. Five blood samples were drawn during the OLT procedure: one just before VVBP, three during VVBP and one 5 min after portal venous reperfusion (PVR). A further sample was taken 1 day after the operation. Components of the blood coagulation, fibrinolytic and kallikrein-kinin systems were analysed using functional assays (chromogenic peptide substrate assays) or enzyme immunoassays (EIA). Complement system factors and granulocyte activation, represented by myeloperoxidase (MPO) release, were analyzed by EIA. Activation of the plasma defence systems occurred in both groups at an early stage during OLT and a further activation occurred 5 min after PVR. MPO levels were slightly elevated 5 min after PVR. However, no significant differences between the two groups were observed. Significant activation of the humoral defense systems was found in both groups during OLT. A considerably larger study, including at least 330 patients, is necessary to fully assess the possible benefits of surface heparinization of the VVBP circuit.

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 (WBP) in orthotopic 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 a non-pulsatile flow (2 l/min) and at a constant temperature (37.5 degrees C) for 12 h. 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 tubing was 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 were 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), 12h = 31* (17.7-63.6), HC: baseline = 4.9 (3.2-6.8), 3h = 9* (6-14.4), 12h = 13.7* (7.4-18.1). TCC: NC: baseline = 0.4 (0.2-0.6), 3h = 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 < 0.05). The C3bc and TCC concentrations were significantly higher in the NC group at 3 and 12 h, compared to the HC group: C3bc (NC vs. HC group): 3 h, p < 0.001; 12 h, p < 0.001. TCC (NC vs. HC group): 3h, p < 0.001; 12 h, p < 0.001. Significant increases in the values of thrombin-antithrombin complexes (p = 0.003), prothrombin fragment 1 + 2 (p = 0.006) and plasmin-alpha2-antiplasmin complexes (p = 0.016) were found in the non-coated group, but not in the heparin-coated group during the observation period, showing that the coagulation and fibrinolytic systems were activated in the non-coated circuits. We conclude that heparin-coating of the internal surface of the extracorporeal perfusion circuit used for WBP reduces activation of the plasma cascade systems in a closed venous system in vitro.