Challenges of Warfarin Management in a Nursing Home Setting

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Warfarin management remains challenging in nursing homes and is a substantial burden on nurses’ time1

Survey results indicated the weekly nursing time required for each resident starting warfarin*1

hours per week

On average, LTC residents spend 50% of the time outside an INR range of 2‑32

pie chart
INR = international normalized ratio

In one study of an elderly population aged 65 and older3:

of all hospitalizations related to adverse drug events are caused by warfarin (95% CI, 28.0-38.5)3

More than insulin, oral antiplatelet agents, and opioids combined3
CI = confidence interval.

Warfarin management presents substantial challenges beyond monitoring

Substantial safety risks
due to adverse warfarin-related events2
  • Bleeding
  • Myocardial infarction
  • Stroke
  • Any 2 of the following: transfusion of 3 or more units of blood, hypotension, critical anemia, or acute bleeding (>3 days)

Over 220 drug-drug
interactions including§4
NSAIDs = nonsteriodal anti-inflammatory drugs

Discontinuation of
warfarin therapy
in studied nursing home residents¶7
one year
           (95% CI, 54%-76%)

Warfarin causes more LTC medication errors than any other drug#8

most errors
In the most recent year for which data are available, 2007.

* Patel study design: A primary, semi-quantitative, web-based survey of staff nurses who were responsible for the care of LTC residents receiving warfarin. Specific objectives included determining the specific nursing tasks related to warfarin therapy and estimating the time requirements for treatment initiation, warfarin management, and monitoring. Forty LTC nurses validated the survey to determine what protocols/procedures were involved in warfarin management. Twenty LTC nurses completed the survey, quantifying the time they spent on procedures related to warfarin management, and how often they performed each procedure for each resident each week.1
Limitations: Study limitations included the potential for bias due to small sample size, representativeness of the sample, and the possibility of inaccuracies in respondents’ self-reported time estimation of warfarin-related procedures. The study was not powered to determine differences in the time taken to perform warfarin-related procedures based on nurse designations and type of LTC. Additional work carried out by other LTC personnel (eg, laboratory staff and assistant nurses) and other factors not related to time estimation (eg, quality of care) were not accounted for. Study results should be regarded as a conservative estimate of resource time required for carrying out warfarin-related procedures in LTC facilities in the United States.1

† Gurwitz study design: A cohort study of all LTC residents of 25 nursing homes (sizes ranging from 90 to 360 beds) in Connecticut during a 12-month observation period. The total number of residents in these facilities ranged from 2946 to 3212 per quarter. A total of 490 residents received warfarin therapy. Possible warfarin-related incidents were detected by quarterly retrospective review of nursing home records by trained nurse abstractors. Each incident was independently classified by 2 physician reviewers to determine whether it constituted a warfarin-related event, its severity, and its preventability. The primary outcome was an adverse warfarin-related event, defined as an injury associated with the use of warfarin. Potential adverse warfarin-related events were defined as situations in which the INR was noted to be 4.5 or greater, an error in management was noted, but no injury occurred. Time in specified INR ranges per nursing home resident day on warfarin was also assessed.2
Limitations: Study authors relied on information that could be ascertained solely through retrospective review of nursing home records to assess the occurrence of warfarin-related incidents. The study was not designed to assess the effectiveness of warfarin therapy for the prevention of thromboembolic events.2

‡ Budnitz study design: Adverse-event data from the National Electronic Injury Surveillance System—Cooperative Adverse Drug Surveillance project was used to estimate the frequency and rates of hospitalization after emergency department (ED) visits for adverse drug events in patients aged ≥65 years from January 2007 through December 2009 (N=5077 hospitalized; N=7589 ED visits but not hospitalized). The contribution of specific medications, including those identified as high risk or potentially inappropriate by national quality measures, was also assessed.3
Limitations: The study utilized public health surveillance systems, which may underestimate the number of emergency hospitalizations because of unintended bias towards detecting acute, known drug effects or effects for which testing is available. Estimates of emergency hospitalizations for adverse drug events did not include patients who were directly admitted for diagnostic evaluation or transferred from another hospital. Data utilized did not provide direct estimates of person-year exposure to medications and excluded medications initiated in nursing homes, ambulatory surgery centers, at hospital discharge, and through telephone or email contact.3

§Suh study design: A nested case-control study of long-term warfarin-treated AF patients ≥18 years old using the Medstat MarketScan database of health insurance claims from 2004 to 2009 (N=7971). Patients with a hemorrhagic event were matched to control patients using incidence density sampling. Drug potentiating warfarin effects were identified within 30 days before the hemorrhagic event. The association between use of potentiating drugs and hemorrhagic risk was calculated using conditional logistic regression. Potentiating medications that increased the anticoagulant effect of warfarin or increased the risk of bleeding through alternate mechanisms were identified from published drug interaction references.4
Limitations: The study was unable to capture the use of any over-the-counter agents or assess potential effects of patient diet and adherence on the effectiveness of warfarin due to the nature of claims data. Selection of treatment by variables not available from health insurance claims data was not controlled in the analysis. Also, there was an essential selection bias and potential underestimation of the risk of hemorrhage from combination therapy. The use of ICD-9-CM codes may have also underestimated the true incidence of hemorrhagic events.4

|| Baillargeon study design: A case-control study nested using enrollment and claims data for a 5% national sample of Medicare beneficiaries with Part D benefits. The study examined the risk of bleeding associated with exposure to all antibiotic agents combined as well as several specific antibiotic agents in a cohort of 38,762 Medicare beneficiaries aged 65 years and older who were continuous warfarin users from January 1, 2008 until hospitalization for a bleeding event or the end of study period (December 31, 2008), whichever occurred first. Logistic regression analysis was used to calculate adjusted odds ratios (aORs) and 95% CIs for the risk of bleeding associated with prior exposure to antibiotic medications.6
Limitations: Some of the cases identified in the study may have been based on misclassified ICD-9-CM codes. There were several limitations with Medicare Part D data: there was no information on co-administration of over-the-counter medications that interact with warfarin to increase the risk of bleeding, the daily dose of warfarin, or the date the prescription was purchased or picked up. As such, the study did not have complete information on the intensity of anticoagulation and the true drug exposure periods may have been underestimated. While the cohort of continuous warfarin users was identified by assessing the number of days the medication was prescribed, changes in INR response that affect weekly dosing schedules may have underestimated that value. The study also assumed that patients adhered to their prescribed medication regimen. The study was not able to assess the extent to which the sequelae of infection may have contributed to increased risk of bleeding among patients with antibiotic exposure.6

¶ Patel study design: A retrospective longitudinal cohort analysis of data obtained from the US AnalytiCare study database of LTC residents with atrial fibrillation who were newly started on warfarin (N=148). The main objective was to measure persistence of warfarin over the first year of therapy. Survival analysis included Kaplan-Meier plots and a multivariate Cox proportional hazards model to test the association of resident characteristics and conditions with warfarin discontinuation.7
Limitations: This screening process may limit statistical power because relatively small eligible populations are often selected, and would have especially limited the ability to identify true associations in the multivariate analysis of resident factors with warfarin discontinuation. Although a discontinuation event was defined as occurring when a gap after the previous warfarin fill exceeded 37 days, residents who experienced a discontinuation event may have restarted warfarin therapy at a later point in time that was beyond the time frame of this analysis. In this study, the indications for which warfarin was used could not be confirmed. Although data for all prescriptions dispensed to eligible residents were expected to be complete, facility medication administration records were not available for cross-validation.7

# Hansen study design: Retrospective analysis using data from the Medication Error Quality Initiative (MEQI) individual event reporting system. Participants were North Carolina nursing homes that submitted incident reports to the web-based MEQI data repository during the 2006 and 2007 reporting years. Data from 206 nursing homes were summarized descriptively, and then a disproportionality analysis was applied. Data collected in 2007 analyzed for this study included individual reports of incidents, near misses, and circumstances of unsafe conditions submitted. Associations between medication type and possible causes at the state level were explored. A single nursing home was selected to illustrate how the method might inform quality improvement at the facility level. Disproportionality analysis of drug errors in this home was compared with benchmarking.8
Limitations: Applying the study approach for prospective quality improvement may face barriers as there may be insufficient volume of medication error reports over short intervals for early detection of error signals. Participation in MEQI is mandatory under North Carolina licensing regulations, but reporting is effectively voluntary in that there is no auditing process. Even among the homes that frequently report their errors, the accuracy of safety signals depends on the correct classification of causes and other error characteristics. The facility selected for the prototype was atypical with respect to the total number of errors it reported, therefore running the analyses for other facilities may be less informative. Disproportionality analysis is subject to reporting bias if there is a correlation between propensity to report an error and other relevant variables (eg, drug, error type, or personnel). As with all adverse event data mining, disproportionality analysis generates hypotheses that are only the first steps in a quality improvement process.8

  1. Patel AA, Nelson WW. Nurses’ self-reported time estimation of anticoagulation therapy: a survey of warfarin management in long-term care. BMC Nursing. 2015;14:8.
  2. Gurwitz JH, Field TS, Radford MJ, et al. The safety of warfarin therapy in the nursing home setting. Am J Med. 2007;120(6):539–544.
  3. Budnitz DS, Lovegrove MC, Shehab N, Richards CL. Emergency hospitalizations for adverse drug events in older Americans. N Engl J Med. 2011;365:2002–2012.
  4. Suh D-C, Nelson WW, Choi JC, Choi I. Risk of hemorrhage and treatment costs associated with warfarin drug interactions in patients with atrial fibrillation. Clin Ther. 2012;34(7):1569-1582.
  5. Coumadin© [Prescribing Information]. Princeton, NJ: Bristol-Meyers Squibb Company.
  6. Baillargeon J, Holmes HM, Lin YL, et al. Concurrent use of warfarin and antibiotics and the risk of bleeding in older adults. Am J Med. 2012;125(2):183–189.
  7. Patel AA, Reardon G, Nelson WW, et al. Persistence of warfarin therapy for residents in long-term care who have atrial fibrillation. Clin Ther. 2013;35:1794–1804.
  8. Hansen RA, Cornell PY, Ryan PB, et al. Patterns in nursing home medication errors: disproportionality analysis as a novel method to identify quality improvement opportunities. Pharmacoepidemiol Drug Saf. 2010;19(10):1087–1094.