A prospective randomized study to determine the optimal dose of intravenous vitamin K in reversal of over‐warfarinization

Abstract

Summary.The optimal management of asymptomatic overanticoagulated patients remains unknown. We measured international normalized ratio (INR), activated partial thromboplastin time (APTT) and prothrombin fragment 1 1 2 (F1 1 2) over 7 d in 24 asymptomatic or mildly haemorrhagic patients on warfarin with prolonged INR of . 7´0 who were randomized to receive 0´5 mg, 1 mg or 2 mg intravenous vitamin K. Of six severely overanticoagulated patients (INR . 9´5 with APTT ratio . 2), five failed to achieve an INR # 4´0 on day 1, irrespective of vitamin K dose given. In the remaining 18 cases, an optimal response (INR 2±4 at day 1) was observed in 67% of those receiving 0´5 mg vitamin K, but only in 33% of those receiving 1 or 2 mg, the majority of whom developed an INR , 2´0. Our results support an optimal dose of 0´5 mg i.v. vitamin K for most overanticoagulated patients, with possibly a repeat dose in the small group of severely overanticoagulated patients.

Warfarin reversal

“…67 In addition, in severely over anticoagulated patients several doses of IV vitamin K may be required to achieve successful reversal. 68 Risk factors for serious bleeding during asymptomatic over anticoagulation Recently, a model has been described that attempts to base the decision to use vitamin K on the relative risk of haemorrhage as a result of over anticoagulation with the potential risk of thrombosis as a result of overcorrection with oral vitamin K. 19 This model estimates that the risk of bleeding is greater than the risk of thrombosis for INR . 7 (regardless of indication for warfarin).…”

How I treat warfarin-associated coagulopathy in patients with intracerebral hemorrhage

“…14,15 Guidelines subsequently evolved to recommendations of vitamin K 5 mg orally or intravenously in patients with major bleeding. 13,16,17 More recently, dose recommendations have been increased to 10 mg of vitamin K. 9,18 It has been recommended that intravenous vitamin K be infused slowly (over 30 minutes) because of an estimated 3/100 000 risk of anaphylaxis.…”

Management of Excessive Anticoagulant Effect Due to Vitamin K Antagonists

“…The best estimate of the frequency of this complication is about 3 per 10,000 doses administered; it may be more likely if formulations containing polyethoxylated castor oil are used to maintain the vitamin K in solution. 16 Modern formulations of vitamin K for intravenous injection utilize solubilizers that appear to be associated with a lower risk of anaphylaxis.…”