Regional cooling of the extracorporeal blood circuit: A novel anticoagulation approach for renal replacement therapy?

Abstract

Objective: To test the hypothesis that cooling of blood in the extracorporeal circuit of continuous veno-venous hemofiltration (CVVH) enables to realize the procedure without the need of anticoagulation. Design: Experimental animal study. Methods: We developed the device for selective cooling of extracorporeal circuit (20°C) allowing blood rewarming (38°C) just before returning into the body. Twelve anesthetized and ventilated pigs were randomized to receive either 6 h of CVVH with application of this device (COOL; n = 6) or without it (CONTR; n = 6). Measurements: Before the procedure and in 15, 60, 180, 360 min after starting hemofiltration variables related to: (1) circuit patency [time to clotting (TC), number of alarm-triggered pump stopping (AS), venous and transmembranous circuit pressures (VP, TMP)], (2) coagulation status in the extracorporeal circuit [thrombin-antithrombin complexes (TATcirc), thromboelastography (TEG)] and (3) animal status (hemodynamics, hemolysis and biochemistry) were assessed. Results: The patency of all circuits treated with selective cooling was well maintained within the observation period. By contrast, five of six sessions were prematurely clotted in the untreated group. As a result, the number of AS was significantly higher in the CONTR group. In-circuit thrombus generation in CONTR group was associated with a markedly increasing TATcirc. TEG performed at 180 min of the procedure revealed a tendency to a prolonged initial clotting time and a significant decrease in clotting rate of in-circuit blood in the COOL group. No signs of repeated cooling/rewarming-induced hemolysis were observed in animals treated with "hypothermic circuit" CVVH. Conclusion: In this porcine model, regional extracorporeal blood cooling proved effective in preventing in-circuit clotting without the need to use any other anticoagulant.