Oral anticoagulation in the hospital: analysis of patients at risk

Impact of a Guideline for the Management of Antimicrobial/Warfarin Interactions in the Inpatient Setting and Across Transition of Care

BACKGROUND

Drug-drug interactions (DDIs) with warfarin and antimicrobial agents are a common cause of international normalized ratio (INR) instability, which can affect the risk for bleeding and thrombotic events.

OBJECTIVE

The purpose of this study was to assess the impact of a comprehensive guideline for the management of warfarin-antimicrobial DDIs across transitions of care. The guideline emphasizes improving identification of significant antimicrobial-warfarin DDIs during hospitalization, empirical warfarin dose modification based on DDI and baseline INR, patient education, documentation of the DDI, communication with outpatient providers regarding the DDI and anticipated antimicrobial stop date, and warfarin dose adjustment on discontinuation of antimicrobial.

METHODS

This retrospective, single-center, quasiexperimental, pre-post study compared end points 3 months before and after guideline implementation. The primary outcome was time within therapeutic range (TTR).

RESULTS

The study included 78 preguideline and 31 postguideline patients; baseline characteristics were similar between groups. Implementation of the guideline resulted in greater in-hospital TTR (72% vs 50%, P = 0.04) and improved TTR across transition of care (70% vs 46%, P = 0.01). Documentation of DDI in the pharmacy anticoagulation discharge summary significantly improved in the postguideline group (40% vs 14%, P = 0.02) and numerically improved within the daily pharmacy progress notes (94% vs 82%, P = 0.13). The implementation of the guideline was associated with a nonsignificant, numerical reduction in bleeding events compared with the preguideline group (0 vs 4 events, P = 0.11).

CONCLUSION

This single-center approach to optimize the comprehensive management of significant antimicrobial-warfarin DDIs resulted in improved communication with outpatient providers and improved INR TTR.

Predictors of warfarin-associated adverse events in hospitalized patients: Opportunities to prevent patient harm

BACKGROUND

The optimum international normalized ratio (INR) monitoring frequency for hospitalized patients receiving warfarin is unknown.

OBJECTIVE

Assess relationship between daily versus less frequent INR monitoring and overanticoagulation and warfarin-related adverse events.

DESIGN

Retrospective cohort study using Medicare Patient Safety Monitoring System data.

SETTING

Randomly selected acute care hospitals across the United States.

PATIENTS

Patients hospitalized from 2009 to 2013 for pneumonia, acute cardiac disease, or surgery who received warfarin.

INTERVENTIONS

None.

MEASUREMENTS

(1) Association between frequency of INR monitoring and an INR ≥6.0 or warfarin-related adverse event. (2) Association between the rate of change of the INR and a subsequent INR ≥5.0 and ≥6.0.

RESULTS

Among 8529 patients who received warfarin for ≥3 days, for 1549 (18.2%) the INR was not measured on 2 or more days. These patients had higher propensity-adjusted odds ratios (ORs) of having a warfarin-associated adverse event (OR: 1.48, 95% confidence interval [CI]: 1.02-2.17) for cardiac patients and surgical patients (OR: 1.73, 95% CI: 1.20-2.48), with no significant association for pneumonia patients. Cardiac and pneumonia patients with 1 day or more without an INR measurement had higher propensity-adjusted ORs of having an INR ≥6.0 (OR: 1.61, 95% CI: 1.07-2.41 and OR: 1.92, 95% CI: 1.36-2.71, respectively). A 1-day increase in the INR of ≥0.9 occurred in 621 patients (12.5%) and predicted a subsequent INR of ≥6.0 (positive likelihood ratio of 4.2).

CONCLUSION

Daily INR measurement and recognition of a rapidly rising INR might decrease the frequency of warfarin-associated adverse events in hospitalized patients.