Should We Modify Anticoagulant Venous Thromboembolism Prophylaxis For Underweight Patients?

SHOULD WE MODIFY ANTICOAGULANT VENOUS THROMBOEMBOLISM PROPHYLAXIS FOR UNDERWEIGHT PATIENTS?

Dr. David Paje, MD, MPH^*^1,2;Vineet Chopra, MD, MSc²;Anna Conlon, PhD¹;Dr. Steven J Bernstein, MD, MPH² and Dr. Scott A Flanders, MD¹, (1)University of Michigan Health System, Ann Arbor, MI, (2)VA Ann Arbor Healthcare System, Ann Arbor, MI

Meeting: Hospital Medicine 2017, May 1-4, 2017; Las Vegas, Nev.

Abstract Number: 119

Category: Research

Sub-Category: Patient Safety

Keywords: Heparin, low BMI, major bleeding, underweight and venous thromboembolism

Background: Prophylactic anticoagulation is effective at reducing the risk of venous thromboembolism (VTE), but can also increase the risk of bleeding. Whether anticoagulant prophylaxis should be modified for underweight patients to minimize bleeding complications is unknown. We sought to determine whether being underweight is associated with the risk of major bleeding in hospitalized medical patients and whether use of prophylactic anticoagulation modifies risk.

Methods: From December, 2011 to July, 2016, trained abstractors at 51 hospitals participating in the Michigan Hospital Medicine Safety (HMS) consortium collected detailed demographic and clinical data on hospitalized adult medical patients, including receipt of anticoagulants for VTE prophylaxis. For this analysis, patients with contraindication to prophylactic anticoagulation (e.g. active bleeding) or with INR ≥ 2 on admission were excluded. The primary outcome was major bleeding during the hospital stay, as defined by the International Society on Thrombosis and Haemostasis (ISTH). The association between underweight body mass index (BMI < 18.5 kg/m²) and the risk of major bleeding was assessed. In addition, the effect of anticoagulant prophylaxis received during the first two days of hospitalization on the rate of major bleeding in underweight patients was evaluated. Odds ratios were calculated using mixed effect multivariable logistic regression with hospital specific random intercepts, controlling for age, gender and Charlson-Deyo comorbidity score.

Results: Of the 88,952 patients included in this analysis, 4,347 (4.9%) were underweight, of which, 3,121 (71.8%) received anticoagulant prophylaxis during the first two days of hospitalization, including 1,414 (32.5%) who received 1-3 doses of unfractionated heparin (UFH), 1,027 (23.6%) >3 doses of UFH, and 667 (15.3%) enoxaparin. The median length of hospital stay was 4 days (interquartile range 3 to 6 days). Among underweight patients, 50 (1.15%) had a major bleeding event. Compared to patients with BMI ≥ 18.5 kg/m², underweight patients were more likely to develop major bleeding, odds ratio (OR) 1.88 (95% confidence interval [CI], 1.40 to 2.53). The receipt of prophylactic anticoagulants had no significant effect on the risk of bleeding (Table 1).

Conclusions: Being underweight increases the risk of major bleeding in hospitalized medical patients. However, the administration of prophylactic anticoagulants is not associated with any incremental risk of bleeding.

Table 1. Rates of Major Bleeding in Underweight Medical Patients According to Receipt of Prophylactic Anticoagulants

Prophylactic Anticoagulant	Total N	Major Bleeding Events
Prophylactic Anticoagulant	Total N	n (%)	OR (95%CI)
None	1,226	13 (1.06%)	reference
1-3 doses Unfractionated Heparin	1,414	18 (1.27%)	1.06 (0.51, 2.18)
> 3 doses Unfractionated Heparin	1,027	13 (1.27%)	1.04 (0.48, 2.26)
Enoxaparin	667	6 (0.90%)	0.73 (0.28, 1.95)
Other	13	0 (0.00%)	–
Total	4,347	50 (1.15%)