Effects of heparin, desmopressin, and isovolemic hemodilution with dextran on thrombus formation in synthetic vessel grafts inserted into the vena cava of the rabbit.

Abstract

The objective of this study was to investigate the effects of isovolemic hemodilution with dextran-70 on thrombus formation and blood flow in synthetic venous vessel grafts. Polytetrafluoroethylene grafts (length, 11 mm; inner diameter, 3 mm) were inserted into the vena cava of rabbits. Six groups were studied: (1) the control group; (2) animals that underwent isovolemic hemodilution with dextran-70 to a hematocrit of about 30%; (3) animals that underwent isovolemic dextran hemodilution combined with a bolus injection of heparin; (4) animals that underwent heparin treatment only; (5) animals that underwent isovolemic dextran hemodilution combined with infusion of desmopressin; and (6) animals that underwent an identical treatment to group 3 but with a 2-week, instead of a 2-day, follow-up. Vena cava blood flow was measured before and after hemodilution and graft insertion and at the termination of the experiments at 2 days (groups 1 to 5) and 2 weeks (group 6) after surgery. Graft patency and thrombus mass weight were evaluated. In the control group, most of the vessels occluded within 2 days. Hemodilution with dextran improved blood flow and reduced thrombus mass weight significantly. Desmopressin, which increases factor VIII, did not influence the effects of hemodilution with dextran, which suggests that the effects of dextran are not mediated by a reduction in the level of this coagulation factor. A single bolus dose of heparin did not reduce thrombus formation in the grafts but did potentiate the effects of isovolemic hemodilution on thrombus mass and graft blood flow. We conclude that isovolemic dextran hemodilution combined with a single bolus of heparin had beneficial long-lasting effects. The grafts in groups 3 and 6 were all patent.