Background
Blood stasis during circulatory arrest (CA) leads to clot formation in a pig model of liver transplantation from donors after cardiac death (DCD). We aim to determine the effects of fibrinolytic therapy administered during a post-CA period of normothermic regional perfusion (NRP).

Materials and Methods
Donor pigs were subjected to 60min CA followed by 60min heparinized NRP; three groups of 9 animals were performed: 1) no pre-CA heparin or tissue plasminogen activator (tPA) given (control); 2) no pre-CA heparin but tPA administration during NRP (tPA group); and 3) pre-CA heparinization, no tPA given (heparin group). Livers were recovered, cold stored 4h, and transplanted. Thromboelastometry (ROTEM) was performed to monitor tPA effect.

Results
Three livers had to be discarded in the control and tPA groups each because NRP failed due to massive clotting. No livers had to be discarded in the heparin group. ROTEM demonstrated significant fibrinolytic differences between tPA and control groups: mean LI30 0% (IQR 0-58%) vs. 98% (96-100%), P=0.011; ML 100% (100-100%) vs. 14% (12-17%), P=0.002. No ongoing fibrinolytic effect was detected in any recipient after reperfusion. When pre-arrest heparinization was performed hepatic flows during NRP and transaminases in the recipients were better than those measured in grafts without pre-CA heparinization, both with and without tPA.

Conclusion
Fibrinolytic therapy administered during NRP cannot effectively counter massive clot formation occurring during CA in porcine DCD donors. Pre-arrest heparinization should be performed whenever possible to prevent the deleterious consequences of intravascular clotting.