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Revisiting the International Normalized Ratio Threshold for Bleeding Risk and Mortality in Primary Total Hip Arthroplasty

A National Surgical Quality Improvement Program Analysis of 17,567 Patients

Rudasill, Sarah E. BA1; Liu, Jiabin MD, PhD2; Kamath, Atul F. MD3

The Journal of Bone and Joint Surgery: October 11, 2019 - Volume Latest Articles - Issue - p
doi: 10.2106/JBJS.19.00160
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Background: Efforts to identify preoperative risk factors for primary total hip arthroplasty have amplified with its increasing incidence. The international normalized ratio (INR) is 1 measure that may influence postoperative outcomes. This study of a national database assessed whether there exists an association between preoperative INR and postoperative bleeding and mortality among patients who underwent primary total hip arthroplasty.

Methods: We retrospectively analyzed 17,567 adult patients who underwent primary total hip arthroplasty in the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) between 2005 and 2016. Patients were stratified by preoperative INR into 4 groups: INR <1.0, 1.0 to <1.25, 1.25 to <1.5, and ≥1.5. Bleeding necessitating transfusion was the primary outcome, and secondary outcomes included mortality, infection, and readmission. Multivariable logistic regressions controlled for baseline differences.

Results: Among the patients who underwent total hip arthroplasty, 20.5% had INR <1.0, 73.6% had INR 1.0 to <1.25, 4.2% had INR 1.25 to <1.5, and 1.8% had INR ≥1.5. Mortality increased incrementally from 0.3% for INR <1.0 to 4.9% for INR ≥1.5 (p < 0.001), and bleeding risk increased from 13.2% for INR <1.0 to 29.3% for INR ≥1.5 (p < 0.001). After adjustment, bleeding risk was increased for INR 1.25 to <1.5 (odds ratio [OR], 1.55 [95% confidence interval (CI), 1.26 to 1.92]) and INR ≥1.5 (OR, 1.55 [95% CI, 1.15 to 2.08]) compared with INR <1.0. The only group associated with increased mortality was INR ≥1.5 (OR, 2.69 [95% CI, 1.07 to 6.76]). The length of stay significantly increased with increasing INR, from 3.6 to 6.3 days (p < 0.001).

Conclusions: This study found a significant, independent effect between increased preoperative INR and increased bleeding and mortality. Bleeding risk becomes evident at INR ≥1.25, and those patients with INR ≥1.5 are at significantly increased risk of mortality.

Level of Evidence: Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

1David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California

2Department of Anesthesiology, Hospital for Special Surgery, New York, NY

3Department of Orthopaedic Surgery, Cleveland Clinic, Cleveland, Ohio

Email address for S.E. Rudasill: srudasill@ucla.edu

Email address for J. Liu: liuji@hss.edu

Email address for A.F. Kamath: akamath@post.harvard.edu

Investigation performed at the Department of Orthopaedic Surgery, Cleveland Clinic, Cleveland, Ohio

Disclosure: The authors indicated that no external funding was received for any aspect of this work. On the Disclosure of Potential Conflicts of Interest forms, which are provided with the online version of the article, one or more of the authors checked “yes” to indicate that the author had a relevant financial relationship in the biomedical arena outside the submitted work (http://links.lww.com/XXXXXXX).

Copyright 2019 by The Journal of Bone and Joint Surgery, Incorporated
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