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 action. It is unclear whether intravenous vitamin K-1 is safe or efficacious 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 heart transplantation) on intraoperative blood product utilization, hemodynamics and coagulation parameters. We also determined the direct effects of vitamin K-1 in vitro on rings of human saphenous vein and internal mammary artery. Results: in the retrospective limb, 29 of 67 patients were administered vitamin K-1 preoperatively via slow intravenous 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 equal 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+/-26 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 anticoagulant effect of warfarin and produced modest hemodynamic changes. The decrease in systemic vascular resistance is probably not due to a direct effect of vitamin K-1 on vascular smooth muscle.