Can oral vitamin K before elective surgery substitute for preoperative heparin bridging in patients on vitamin K antagonists?

Background: After a vitamin K antagonist (VKA) overdose, 1-2 mg of oral vitamin K can lower the International Normalized Ratio (INR) to the therapeutic range. Objective: To establish whether oral vitamin K can substitute for heparin bridging and decrease the INR to < 1.5 before elective surgery. Methods: Patients on long-term VKAs were randomized either to heparin bridging after the last VKA dose on day - 5 before surgery (group H) or to VKA treatment until day - 2, followed by 1 mg of oral vitamin K on the day before surgery (group K). Blood clotting variables were assessed on days -5/-2, 1 and 0, and postoperatively. If the target INR was not achieved 2 h before incision, surgery was deferred or performed after injection of prothrombin complex concentrate (PCC). Results: In 30 of 94 included patients, baseline INR was outside the chosen range (18, INR < 2; 12, INR > 3.5), leaving 34 eligible patients in group H and 30 in group K. The groups were balanced in terms of body mass index, VKA treatment duration and indication, scheduled surgery, preoperative and postoperative hemoglobin, and blood loss. The INR was significantly higher in group K on days - 1 and 0 than in group H. An INR < 1.5 was not achieved in 20 group K patients (66%). Surgery was postponed or performed after PCC injection in 12 of these 20 patients. Conclusions: Oral vitamin K (1 mg) cannot substitute for heparin bridging before surgery. In addition, one-third of patients on VKAs were exposed to a risk of bleeding (overdose) or thrombosis (underdose), thus highlighting the need for new oral anticoagulants.