Ex vivo testing of heparin-coated extracorporeal circuits: bovine experiments.
In this study the intrinsic thrombogenicity of the extracorporeal circuits and the benefit of heparin-bonded circuits in an extracorporeal life support system without full systemic heparinization and with minimal interference of the so called material-independent factors was tested in four calves. In two circuits (group A) all blood-contacting surfaces were coated with end-point-attached heparin and the other two were non-coated (group B). Under standardized conditions the calves were perfused at a blood flow rate of 2 L/min. After only one bolus injection of heparin (250 IU/kg body weight) before cannulation, plasma heparin activity rapidly decreased in both groups: half life of about 55 minutes. This decrease of the heparin activity was accompanied by a fall of the activated clotting time (ACT) level to baseline values. The experiments using a heparin-coated circuit, had a runtime of more than 360 minutes, whereas the experiments using a non-coated circuit had to be terminated after a runtime of 255 minutes, because massive fibrin formation was noticed in the circuit. This formation was accompanied by a rapid increase in the line pressure, measured just before the inlet of the oxygenator. The macroscopic inspections after terminating the experiments and rinsing the circuit showed a clean circuit in group A. The fibrinopeptide A (FPA) level increased faster during perfusion with the non-coated circuit than in the heparin coated circuit. Lung histopathological examinations of the lungs of the animals in group A showed no fibrin deposition, whereas most of the blood vessels of the lung preparations of the animals in group B were partially or completely occluded with fibrin. These results suggest that heparin-bonding greatly reduces the thrombogenicity of the extracorporeal circuit, and therefore it can reduce the need for systemic heparinization in an extracorporeal life support system.
Weerwind
P W
PW
Department of Extra Corporeal Circulation, University Hospital Nijmegen, The Netherlands. p.weerwind@thchir.azn.nl
van der Veen
F H
FH
Lindhout
T
T
de Jong
D S
DS
Cahalan
P T
PT
D000818:Animals; D000925:Anticoagulants / Q000627:therapeutic use; D000933:Antifibrinolytic Agents / Q000097:blood; D002406:Catheterization, Peripheral; D002417:Cattle; D005112:Extracorporeal Circulation / Q000295:instrumentation* / Q000379:methods; D015199:Extracorporeal Membrane Oxygenation / Q000295:instrumentation; D005337:Fibrin / Q000032:analysis; D005344:Fibrinopeptide A / Q000032:analysis; D006493:Heparin / Q000097:blood; D008168:Lung / Q000098:blood supply / Q000473:pathology; D013499:Surface Properties; D013927:Thrombosis / Q000517:prevention & control; D014914:Whole Blood Coagulation Time
D000925:Anticoagulants; D000933:Antifibrinolytic Agents; D005344:Fibrinopeptide A; D005337:Fibrin; D006493:Heparin