Anaphylaxis after low dose intravenous vitamin K

Characterizing the Severe Reactions of Parenteral Vitamin K1

Parenteral vitamin K1 (phytonadione) is used for anticoagulant reversal, and a boxed warning exists with intravenous and intramuscular administration due to the possibility of severe reactions, including fatalities. These reactions resemble hypersensitivity or anaphylaxis, including anaphylactoid reaction, and have led to shock and cardiac and/or respiratory arrest. The objective of this review is to summarize the available literature detailing the anaphylactic/anaphylactoid reactions with parenteral vitamin K1 in order to better characterize the reaction and provide a more in-depth understanding of its importance. A comprehensive literature search of MEDLINE (1946 to June 2016) and EMBASE (1947 to June 2016) was conducted using the terms vitamin K1, phytonadione, phytomenadione, vitamin K group, anaphylaxis, polyoxyethylated castor oil, and cremophor. A total of 2 retrospective surveillance studies, 2 retrospective cohort studies, and 17 case reports were identified for inclusion and assessment. Based on a review of the literature, use of parenteral vitamin K1 may result in severe hypotension, bradycardia or tachycardia, dyspnea, bronchospasm, cardiac arrest, and death. These reactions are most consistent with a nonimmune-mediated anaphylactoid mechanism. It appears that intravenous administration is more frequently associated with these reactions and occurs at an incidence of 3 per 10 000 doses of intravenous vitamin K1. The solubilizer may also increase the risk of adverse reactions, which occurred in patients with and without previous exposure to vitamin K1. Although there are known factors that increase the risk of an adverse drug event occurring, reactions have been reported despite all precautions being properly followed.

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 < or = 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 < or = 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.

Warfarin reversal in anticoagulant-associated intracerebral hemorrhage

Anticoagulant-associated intracerebral hemorrhage (ICH) is a devastating disease, causing death in half of patients and permanent disability in the majority of survivors. The finding that patients often continue bleeding after hospital presentation offers the possibility that emergency warfarin reversal may improve outcomes. As no clinical trials have demonstrated the superiority of any one treatment strategy, various treatment options are available. Intravenous vitamin K is the definitive therapy; however, as monotherapy it can require many hours to take effect. Therefore, it is often considered an adjunct agent. Coagulation factors can be repleted with fresh frozen plasma (FFP), which is widely available and relatively low cost, but can require substantial time to deliver in real-world settings. A number of coagulation factor products collectively termed prothrombin complex concentrates (PCCs) are widely available that can rapidly provide many or all the vitamin K-dependent coagulation factors. Recombinant activated factor VII is used in many centers for this purpose, as it is thought to provide a procoagulant effect that may compensate for the lack of the other critical factors. Until clinical trials demonstrate the superiority of any one means of warfarin reversal, a number of expert guidelines from national organizations are available to help local providers guide therapy. At our institution, we have focused on improving the rapid and reliable delivery of a combination of intravenous vitamin K and FFP, with continued re-dosing until the desired INR lowering is achieved.

Perioperative management of patients receiving vitamin K antagonists

PURPOSE

As the number of patients taking vitamin K antagonists (VKA) is growing, the clinician is increasingly faced with having to make decisions regarding anticoagulation therapy before, during and immediately after surgery. In this article we review the indications for VKA and assess their use in the perioperative period based on available pharmacological and clinical data.

SOURCE

An on-line computerized search of Medline was conducted limited to English and French language articles. The bibliographies of relevant articles and additional material from other published sources were retrieved and reviewed.

PRINCIPAL FINDINGS

Assessment of patients taking VKA who need surgery must include three factors: 1) the indication for anticoagulation, which determines the thromboembolic risk; 2) the pharmacokinetics of VKA, which determine the moment at which treatment should be discontinued; and 3) the type of surgery, which determines the hemorrhagic risk. Some patients will need to stop VKA treatment and start a substitution or "bridging" anticoagulant therapy, such as unfractionated heparin or low molecular weight heparin, prior to and after surgery. In patients requiring emergency surgery, prothrombin complex concentrate can be used to improve coagulation and is preferable to, although more expensive than fresh frozen plasma.

CONCLUSIONS

For the perioperative setting, further studies are required to determine the optimal substitution ("bridging") regimen and the clinical circumstances that necessitate substitution therapy.