EFFECTS OF HEPARIN, DESMOPRESSIN, AND ISOVOLEMIC HEMODILUTION WITH DEXTRAN ON THROMBUS FORMATION IN SYNTHETIC VESSEL GRAFTS INSERTED INTO THE VENA-CAVA OF THE RABBIT

The objective of this study was to investigate the effects of isovolem ic hemodilution with dextran-70 on thrombus formation and blood flow i n synthetic venous vessel grafts. Polytetrafluoroethylene grafts (leng th, 11 mm; inner diameter, 3 mm) were inserted into the vena cava of r abbits. Six groups were studied: (1) the control group; (2) animals th at underwent isovolemic hemodilution with dextran-70 to a hematocrit, of about 30%; (3) animals that underwent isovolemic dextran hemodiluti on combined with a bolus injection of heparin; (4) animals that underw ent heparin treatment only; (5) animals that underwent isovolemic dext ran hemodilution combined with infusion of desmopressin; and (6) anima ls 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 befo re and after hemodilution and graft insertion and at the termination o f the experiments at 2 days (groups 1 to 5) and 2 weeks (group 6) afte r surgery. Graft patency and thrombus mass weight were evaluated. In t he control group, most of the vessels occluded within 2 days. Hemodilu tion with dextran improved blood flow and reduced thrombus mass weight significantly. Desmopressin, which increases factor VIII, did not inf luence the effects of hemodilution with dextran, which suggests that t he 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 iso volemic 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 an d 6 were all patent.