Abstract 203: Outcomes Comparison of Low Risk Medical and Surgical Patients Treated with Unfractionated Heparin vs. Enoxaparin
Authors: Corbelli John , Zammit Kimberly , Griffiths Beth , Ma Changxing , Tung Ying , Graves Clifford , Genena Daniel , Boyd Donald , Meyer Francis , Arbogast Patricia , Bourji Mohamed 
Published: March 2022

Objectives:
We sought to compare the relative risks for adverse arterial vascular events in patients considered to be low risk for venous thromboembolism (VTE) events who were treated with enoxaparin compared to unfractionated heparin (UFH) for VTE prophylaxis, while comparing clinical efficacy for VTE and overall inpatient costs.

Methods:
We retrospectively identified patients admitted to the medical and general surgical services who received VTE prophylaxis with either UFH or enoxaparin and compared outcomes before and after implementation of a evidenced based anticoagulation protocol during a twelve month period. Exclusions were: (1) high risk surgical patients, specifically patients undergoing orthopedic, cardiovascular, and bariatric surgery; (2) high risk medical patients, specifically patients admitted with, or having a history of, pulmonary embolism (PE), deep venous thrombosis, atrial fibrillation, or valve replacement; and (3) patients with a therapeutic INR (>2.0) on admission. Using Logistic regression analysis, the following outcomes were compared between the UFH and enoxaparin treated groups: deep venous thrombosis, PE, myocardial infarction (MI), stroke, transient ischemic attack (TIA), heparin induced thrombocytopenia (HIT) and mortality among both groups. Length of hospital stay (LOS) and length of intensive care unit (ICU) LOS were compared using multiple regression analysis. Total costs between the two treatment groups were also compared using a t-test.

Results:
From the study group, a total of 6,390 patients received UFH prophylaxis and 1,565 received enoxaparin. The enoxaparin patients’ average age was younger than the UFH treated patients’ age by 2.4 years (59.1 and 61.5 years old, respectively, p<0.0001). The incidence of deep venous thrombosis, PE and HIT was similar in both groups. The enoxaparin group had a 52% higher odds for TIA (3.64 vs. 2.49 per 100 patients, OR=1.52, CI 1.113,2.078, p= 0.0024), 61% higher odds for stroke (9.3 vs. 6.6 per 100 patients, OR=1.589, CI 1.298, 1.945, p= 0.0009), while having a 54% lower odds for MI (2.1 vs. 4.7 per 100 patients, OR=0.46,CI 0.32, 0.66, p<0.0001) and lower mortality rate (0 vs. 1.3 per 100 patients). The hospital LOS in the enoxaparin group was 0.73 days lower than in the heparin group (4.41 days vs. 5.13 days, p<0.0001) and the ICU LOS was also shorter by 0.6 days (0.095 vs. 0.69 days, p<0.0001). The total cost (20, 690 vs. 25,946 dollars) was lower in the enoxaparin group.

Conclusions:
In low-risk medical and general surgical patients, UFH was as effective as enoxaparin in the prevention of thromboembolic events, with no difference in the incidence of HIT. When compared to UFH, enoxaparin was associated with lower MI and mortality rates, and shorter LOS and ICU LOS, at the expense of higher rates of stroke and TIA. Enoxaparin was associated with lower total inpatient costs than UFH.