Warfarin cessation prior to cardiopulmonary bypass

The rate and extent to which active vitamin K (vit K) dependent factors replenish after discontinuation of warfarin for cardiac surgery is poorly defined. This study examines the recovery of vit K dependent coagulation factors along with the effects of CPB on coagulation factors. The potential benefit of preoperative oral vit K on the levels of the vit K dependent coagulation factors was investigated via a randomized, placebo controlled trial. Forty patients on warfarin undergoing CPB were randomized to receive 5 mg of oral vit K or placebo 6 days prior to surgery. Blood samples were drawn just prior to study medication administration (baseline), on the morning of operation (pre0), just before initiation of CPB (B4), 10 min on CPB, on ICU admission, and on postoperative day 5. Samples were assayed for prothrombin time, and functional levels of factors II, V, VII, IX, and protein C. Multilevel modeling illustrated that measurement period, time between measurements, and their interaction predicted levels. Factors II and VII levels were less than 50% on CPB. Incomplete recovery of factors II, VII, and protein C by the morning of operation was observed despite normalization of PTs. Vit K dependent factor levels on the morning of operation trended higher in the Vit K group, but did not achieve statistical significance. Our findings demonstrate that discontinuation of warfarin 6 days preoperatively may not be long enough for complete factor recovery in cardiac surgery patients. Furthermore, 5 mg of oral vit K upon warfarin cessation may not be sufficient to optimize these levels. A model of functional coagulation factor levels throughout the perioperative period was defined.TABLE—ABSTRACT 37FactorIIVIIIXProt CGroupKCtrlKCtrlKCtrlKCtrlBaseline0.410.380.390.350.760.700.340.34∗0.140.180.160.160.170.180.140.26Pre00.880.790.880.771.131.051.030.87∗0.210.230.260.170.200.200.190.26∗Mean functional level SD in u/ml.