INTRAVENOUS VITAMIN-K-1 PRIOR TO ORTHOTOPIC HEART-TRANSPLANTATION - EFFECTS IN-VIVO AND IN-VITRO

Background: Vitamin K-1 is used to reverse warfarin's anticoagulant ac tion. It is unclear whether intravenous vitamin K-1 is safe or efficac ious prior to urgent cardiac surgery. Methods: We retrospectively and prospectively examined the effects of preoperative intravenous vitamin K-1, in vivo (administered for warfarin reversal immediately before h eart transplantation) on intraoperative blood product utilization, hem odynamics and coagulation parameters. We also determined the direct ef fects of vitamin K-1 in vitro on rings of human saphenous vein and int ernal mammary artery. Results: in the retrospective limb, 29 of 67 pat ients were administered vitamin K-1 preoperatively via slow intravenou s infusion. Vitamin K-1 administration produced no adverse outcome but did not affect subsequent perioperative use of blood products. In the prospective limb (n=10), vitamin K-1 significantly (P less than or eq ual to 0.01, Student t-test) altered mean arterial pressure (from 85+/ -15 to 76+/-16 mmHg), systemic vascular resistance (from 1364+/-308 to 1078+/-252 dyn . s . cm(-5)), and cardiac index (from 2.3+/-0.3 to 2. 7+/-0.3 L/min/m(2)) (mean+/-SD). Significant decreases in prothrombin time (19.8+/-2.7 to 17.7+/-1.8 s) and activated clotting time (164+/-2 6 to 137+/-24 s) were observed at 60 min. In vitro, vitamin K-1 (10(-7 ) to 10(-4) M) had no effect on the tone of noradrenaline-constricted rings. Conclusions: Vitamin K-1, administered by intravenous infusion prior to heart transplantation, did not alter subsequent perioperative blood product administration. Vitamin K-1 rapidly reversed the antico agulant effect of warfarin and produced modest hemodynamic changes. Th e decrease in systemic vascular resistance is probably not due to a di rect effect of vitamin K-1 on vascular smooth muscle.