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.
Department of Extra Corporeal Circulation, University Hospital Nijmegen, The Netherlands. p.weerwind@thchir.azn.nl
P W
PW
Weerwind
F H
FH
van der Veen
T
T
Lindhout
D S
DS
de Jong
P T
PT
Cahalan
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