Modelling of vitamin K half-life in patients treated with vitamin K antagonists before hip fracture surgery
Abstract
Background Guidelines recommend treatment with vitamin K in patients requiring reversal of the effect of vitamin K antagonists (VKA) before semi-urgent surgery. In clinical practice, the time for reversal of the international normalized ratio (INR) to values adequate for surgery is often reported longer than the expected 12–24 hours, which may delay surgery and increase the risk of complications. Methods In order to optimize the management of elderly patients treated with VKA and undergoing hip fracture surgery, we aimed to model the vitamin K half-life in this specific population. Files for patients admitted between 2006 and 2008 for hip fracture surgery and chronically treated with VKA were retrospectively studied. Only patients with an INR superior to 1.5 upon arrival were included in the study. The effect of vitamin K on the decrease in INR was modelled after a PK/PD analysis using NONMEM. Thirty-one patients’ files were analysed. Results Despite management in accordance with guidelines, 31% of the patients had a delayed return to INR values < 1.5 resulting in delayed surgery. Time to INR < 1.5 was longer than 24 hours in 50% of the patients. The calculated half-life of vitamin K was 24.7 hours in this population. Conclusion The vitamin K half-life in elderly patients treated with VKA and undergoing hip fracture surgery was prolonged. The use of vitamin K or of a more rapid acting alternative should be discussed, depending on the urgency of the surgery