Blood coagulation studies during six day heparinless venoarterial bypass in sheep.

Heparinless venoarterial bypass (HL-VAB) was carried out in 16 sheep for 6 days, by means of a closed circuit tubing coated with nonthrombogenic polyurethane-polyvinyl-graphite (PPG) and a roller pump. Nine experiments were completed uneventfully. Seven sheep died during bypass. The causes of death were pneumonia (2), caseous granulomatous lung abscess (3) or abdominal abscess (1), and thromboembolism (1). The last complication was caused by inadverten trauma to the PPG coating at the time of tubing connection. In the animals in which HL-VAB was uneventful, no significant changes were noted in the hematologic studies including white blood counts, platelet counts, hematocrit, plasma fibrinogen levels, prothrombin time, thrombin time, activated partial thromboplastin time, Factors V and VIII, and free plasma hemoglobin levels. Inconsistant changes in the above parmeters were noted in the animals which died of complications. In conclusion, prolonged HL-VAB has no adverse effects on blood coagulation mechanism.