Practice Patterns of Venous Thromboembolism Prophylaxis and Adherence to Standardized VTE Order Sets in Hospitaized Obese Patients

Introduction: Obesity is a known independent risk factor for venous thromboembolism (VTE). While effective pharmacologic prophylaxis has been established in nonobese medical and surgical inpatients, the ideal drug, dose, frequency, and duration in hospitalized obese patients (HOPs) is unknown. In our tertiary academic medical center, a standardized electronic physician order set derived from the 2008 American College of Chest Physicians guidelines is utilized for inpatient VTE risk stratification and thromboprophylaxis on the day of admission. Obesity places a patient in the moderate risk category with standard doses of unfractionated heparin (UFH), enoxaparin, or fondaparinux provided as options for thromboprophylaxis. Sequential compression devices (SCDs) are optional for moderate risk patients. This retrospective analysis evaluates VTE prophylaxis prescribing patterns and assesses adherence to our VTE risk stratification and thromboprophylaxis recommendations.

Methods: A single center retrospective chart review using the hospital administrative database identified adult obese patients (based on BMI >30 kg/m²) admitted from January 1, 2012 through December 31, 2012. Exclusion criteria were patients admitted: 1) on therapeutic anticoagulation, 2) for a primary diagnosis of bleeding, 3) for bariatric surgery, 4) to the obstetric service, 5) with hospital length of stay <24 hours or >30 days, 6) with suspected VTE, or 7) with acute renal failure, end-stage renal disease, or chronic kidney disease. Primary outcomes included adherence to order set risk stratification and prescribing patterns of pharmacologic VTE prophylaxis (drug, dose, frequency, and medication administration) in a random sample of 1000 patients from the entire cohort. Chart review of electronic medical records including physician orders for pharmacologic prophylaxis for each hospitalization day was completed. Descriptive analysis was performed with continuous variables summarized by mean (+/- standard deviation) or median (interquartile range) and categorical variables by frequencies (percentages). All statistics were generated using SAS v 9.4 (the SAS Institute, Cary, NC).

Results: A total of 5993 patient encounters representing 4860 unique patients met inclusion/exclusion criteria. Of the 1000 patients randomly sampled for detailed chart review, mean age was 53.2 (+/-15.3) years, 59.4% were female, mean BMI was 37.1 (+/-7.5) kg/m2, median LOS was 4 (5) days. Pharmacologic prophylaxis was prescribed in 4694 (79.1%) of 5931 patient days. Pharmacologic prophylaxis was not prescribed on the day of admission in 253 (25.3%) patients encounters. Standard prophylaxis regimens included: UFH 5000 units (u) TID in 2531 (42.8%) patient days, UFH 5000u BID in 219 (3.7%) patient days, enoxaparin 40mg QD in 1046 (17.7%) patient days, enoxaparin 30mg BID in 183 (3.1%) patients days, fondaparinux 2.5 mg QD in 64 (1.1%) patient days. More aggressive thromboprophylaxis prescribed were: UFH 7500u BID or TID in 369 (6.2%) patient days, enoxaparin 40mg or 50mg BID in 94 (1.6%) patient days, fondaparinux 5mg QD in 17 (0.3%) patient days. Pharmacologic prophylaxis was not administered in 843 (18.0%) patient days. The primary reason prophylaxis was not administered included “patient refused” (51.31%), or no reason was given (12.9%). SCDs were ordered for 61.9% of patient encounters on the day of admission. Clinicians risk stratified patients utilizing the standardized VTE order set at the time of admission for 787 (78.7%) patient encounters. Among those risk stratified, 114 (11.5%) were deemed low risk, 649 (65.3%) moderate risk, and 24 (2.4%) high risk for VTE. Based on the clinical risk factors for VTE delineated on the standardized order set, 28 (2.8%) had no VTE risk factors, 893 (89.3%) had 1-2 risk factors, and 79 (7.9%) had 3 or more risk factors other than obesity.

Conclusion: The majority of HOPs patients were appropriately stratified as at least moderate risk for VTE and prescribed standard thromboprophylaxis regimens. However, a significant portion of HOPs was incorrectly categorized as low risk and did not receive any thromboprophylaxis during their hospitalization. Whether this underutilization of thromboprophylaxis and inappropriate risk stratification translates into increased clinically relevant outcomes (e.g. VTE, bleeding, VTE- related death) in this population needs to be investigated.