General medicine/original research
Emergency Department Management of Patients on Warfarin Therapy

Presented as a poster at the American College of Clinical Pharmacy annual meeting, October 2008, Louisville, KY.
https://doi.org/10.1016/j.annemergmed.2011.01.018Get rights and content

Study objective

To characterize warfarin management in the emergency department (ED).

Methods

This was a retrospective, cross-sectional, observational study of patients who were receiving warfarin and were discharged from a tertiary care, academic urban ED between June and August 2007. We abstracted patient demographics, presenting complaint, international normalized ratio (INR) if tested, indication for warfarin if documented, new medications administered or prescribed in the ED, and discharge instructions. Presenting complaints were categorized according to whether they were warfarin-related and concerning for thrombosis or bleeding. The primary outcome measure was the prevalence of warfarin therapy. The secondary outcome measures were frequency with which ED providers obtained an INR result, response to nontherapeutic results, administration or prescription of interacting medications, and percentage of patients receiving recommendations for anticoagulation follow-up.

Results

Two percent (111/7,195) of all patients presenting to and discharged from the ED during the study period were found to be receiving warfarin. Seventy-one percent (79/111) had an INR checked. Nontherapeutic INRs were recorded for 49% (39/79) of patients; ED providers intervened to address these results in 21% (8/39) of cases. Seventy-one percent (5/7) of patients with a supratherapeutic INR received an intervention compared with 9% (3/32) of patients with a subtherapeutic INR. Seventeen percent (19/111) and 13% (14/111) of patients received or were prescribed potentially interacting medications, respectively. Recommendations for specific anticoagulation follow-up were documented for 19% (21/111) of all patients.

Conclusion

Patients receiving warfarin frequently present to the ED and often have nontherapeutic INRs. Potential areas for improvement in ED management include greater attention to subtherapeutic INRs, interacting medications, and discharge planning.

Introduction

An estimated 2 million new patients in the United States begin receiving warfarin each year for the prevention or treatment of various thromboembolic disorders.1 Warfarin-related visits to the emergency department (ED) may account for 43,000 ED visits annually.2 “Reduce the likelihood of patient harm associated with the use of anticoagulant therapy” is one of the 2011 National Patient Safety Goals identified by The Joint Commission.3 However, these national standards focus on improvement in anticoagulation management of hospitalized patients and are not targeted to address concerns specific to the ED.

Complications from anticoagulation therapy are often urgent and require ED treatment. Additionally, patients receiving warfarin often have significant underlying illnesses that may bring them to the ED in between routine anticoagulation monitoring appointments. These ED visits can present opportunities for prevention of subsequent warfarin-related complications. Previous studies have suggested a prevalence of nontherapeutic international normalized ratios (INRs) from 11% to as high as 58% in outpatients presenting to their anticoagulation providers for routine INR checks.4 ED patients may be even more likely to have out-of-range INRs: 72% of patients receiving warfarin were found to have nontherapeutic INRs in one study conducted at the ED of 2 urban academic medical centers in New York.4 Given that INRs above and below the therapeutic range have been strongly associated with bleeding or thromboembolic events in multiple studies, the ED visit may be an opportunity to prevent substantial morbidity in patients with nontherapeutic INRs.5

Previous studies on ED management of patients receiving warfarin have evaluated patients presenting to the ED with nontherapeutic INRs.4, 6 However, these studies do not report on the overall prevalence of patients receiving warfarin who present to the ED. Moreover, many of the patients included in previous studies required hospital admission. Data are lacking about the care provided to patients receiving warfarin who present to and are discharged directly from the ED. For example, how frequently are ED providers checking INRs, addressing out-of-range INRs, prescribing interacting medications, or making anticoagulation-related follow-up arrangements for these patients?

It is important to evaluate warfarin management specific to care received in the ED, particularly in cases that do not require hospital admission and where follow-up is uncertain, so that areas for improvement can be identified. This has the potential for preventing complications in patients receiving this high-risk medication.

The goal of this investigation was to describe the prevalence and management of patients receiving warfarin who present to and are discharged directly from the ED, including: the frequency with which INRs are obtained and addressed; the frequency with which potentially interacting medications are administered in the ED or prescribed on discharge; and the percentage of patients who receive a documented recommendation for specific anticoagulation-related follow-up.

Section snippets

Study Design

This was a cross-sectional observational study of patients receiving warfarin who presented to and were discharged directly from a tertiary care, academic urban ED in California between June 1 and August 31, 2007. Data were collected by retrospective chart review of the ED electronic medical record. Approval was obtained from the University of California, San Francisco Committee on Human Research.

Setting

The ED in which the study was performed is located within a tertiary care, urban academic medical

Results

Between June and August 2007, 9,273 patients presented to the ED at the study site, with 2,078 of these patients subsequently admitted to the hospital (Figure 1). Of the remaining 7,195 patients who were discharged directly from the ED, 241 met search criteria. One hundred thirty patient visits were excluded because they involved repeat visits for the same patient (n=34), patients not receiving warfarin (n=94), or patients who were subsequently hospitalized (n=2). As a result, 111 patients met

Limitations

This study's retrospective, single-center design limits the applicability of the results to other hospitals. In addition, a single investigator who was not blinded to the study objectives abstracted the data. To counter this weakness of having only a single coder, particular care was taken when coding data such as presenting complaints to apply clear definitions that, if applied by another chart reviewer, would result in the data being coded the same way. The reliance on ED provider chart

Discussion

Our results indicate that ED providers care for a substantial number of patients receiving warfarin therapy, and often these patients present with nontherapeutic INRs. Furthermore, nontherapeutic INRs are addressed for a minority of patients, with a particular lack of attention to subtherapeutic INRs. Interacting medications were prescribed to nearly one fifth of patients, but follow-up arrangements to ensure management of these drug interactions were infrequently documented. Finally, written

References (7)

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Cited by (6)

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    Citation Excerpt :

    The use of warfarin has several disadvantageous, a wide range of drug interactions and a narrow therapeutic INR range which entails constant monitoring of its action [26]. It has been reported that patients receiving warfarin generally have an INR outside the therapeutic range [27,28]. Data from the first cohort of the Global Anticoagulant Registry in the Field (GARFIELD) study shows that, among 6047 patients on vitamin K antagonists, monitoring of drug action via the INR was recorded for only 3952 patients, and only 1660 had a therapeutic level that met the current recommendation, with a time in therapeutic range above 60 % [29].

Supervising editor: Steven M. Green, MD

By Annals policy, submissions authored by faculty in the department of the editor in chief (Dr. Callaham) are handled entirely by other senior editors, and Dr. Callaham plays no role in their decisionmaking nor is informed of any details during the process.

Author contributions: EM conceived the study, obtained approval for the study from the University of California, San Francisco Committee on Human Research, collected the majority of the data, analyzed all data, and drafted the article. All authors designed the study, with EJW providing advice about the types of outcome measurements that could be obtained using the ED's electronic database, as well as those that would be of greatest interest to ED providers. CED and EJW assisted EM with a portion of data collection. All authors substantially revised the article. EM takes responsibility for the paper as a whole.

Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article that might create any potential conflict of interest. The authors have stated that no such relationships exist. See the Manuscript Submission Agreement in this issue for examples of specific conflicts covered by this statement.

Publication date: Available online April 8, 2011.

Please see page 193 for the Editor's Capsule Summary of this article.

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Dr. Meeker is currently affiliated with the Department of Pharmacy, School of Pharmacy, University of Washington, Seattle, WA.

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