Observational study for clinical outcomes of Enoxaparin, with comparison to Aspirin Monotherapy, for Venous Thromboembolism Prophylaxis in obese patients, post-surgical interventions

Background There was a clear gap in knowledge about enoxaparin prophylactic use in obese patients identified as part of the literature review. The studies conducted in this field of research share some common weaknesses, such as being mostly laboratory-based with no easily identifiable clinical endpoint(s), and subject recruitment and observation typically ended at the point of discharge with no post-discharge follow-up. Where clinical endpoints were included, they were typically inpatient chart audit only, with little to no clinical history or context. Due to these limitations, it was difficult to ascertain and assess the success or failure of thromboprophylaxis, especially in an obese population. Aim The aim of this study was to investigate the potential impact of obesity on patients’ clinical outcome and response to the usual post orthopaedic surgery thromboprophylaxis enoxaparin or aspirin. Additionally, the participants perceived barrier(s) to adherence to the prescribed prophylaxis were explored. Design and Methods This study was conceptualised to be a low-cost, single-investigator, multiphase, observational study. The data collected included secondary quantitative data collected from medical records, and semi-structured phone survey for primary data in qualitative components. The extracted data from relevant databases were then manually cross-checked against the predetermined inclusion and exclusion criteria. For the subsequent qualitative phase, all eligible patients were invited to participate in semi-structured phone survey to share their experience in the relevant episodes of admission and, if applicable, any subsequent re-presentation or readmission to hospital or any other care settings related to thromboembolic event/s (including pulmonary embolism, deep vein thrombosis or major bleeding). Patients who returned their consent forms and agreed to be surveyed by phone, and for their medical records to be reviewed, were enrolled for the first phase of the study. This phase was designed to investigate the success or failure of enoxaparin thromboprophylaxis therapy in the context of patient adherence to the prescribed regimen dose and duration. The next phase was designed to explore the impact of obesity on the success or failure of enoxaparin thromboprophylaxis in post-surgical patients after they were discharged from hospital. Lastly, the third sub-study was designed to compare thromboprophylaxis success or failure in two patient cohorts who received either aspirin or enoxaparin following elective orthopaedic surgery. Results The qualitative analysis found that most patients were adherent to enoxaparin subcutaneous injections as thromboprophylaxis, with only 12% of patients self-reported to be non-adherent to treatment. Barriers identified to their adherence included: practitioner–patient miscommunication, mismatched prescriber–patient expectations, under-empowerment of patients with medication-specific knowledge, and deficits in practitioners’ adherence to guidelines. Patients who received only enoxaparin as venous thromboembolism prophylaxis had their records screened (n = 1189), 319 patient records met the selection criteria and were included in the analysis. Symptomatic thrombotic events were detected in 0.63% of patients (n = 2), with a single case of a major bleeding event (0.31%, n = 1). In the screened sample of patient records (n = 1189), it was identified that 152 of the patients were prescribed enoxaparin, and 227 patients prescribed aspirin as thromboprophylaxis mono-agents after orthopaedic surgical procedures. There was a total of 8 cases (2.11%) reported with at least one deep vein thrombosis or pulmonary embolism event, where 7 episodes resulted in extended hospital stay (n = 2 for enoxaparin, and n = 5 for aspirin), or readmission to the care facility after initial discharge (n = 2 for aspirin). The aspirin group contributed most of the symptomatic cases (2.64% of all aspirin sample compared to 1.31% of all enoxaparin cases). Although no statistical significance was detected between the number of symptomatic cases in each group compared to the total samples, the incidence in the aspirin group (n = 6) was higher than that of enoxaparin (n = 2) by threefold, which may be interpreted as a clinically significant finding. Neither group reported any events of major bleeding. Conclusion Although no statistical difference was detected between aspirin and enoxaparin, the difference in clinical outcomes might be of value for consideration by prescribers. Low molecular weight heparin appeared to be the choice that yielded improved clinical outcomes. Some of the barriers to total adherence to prophylactic therapy were identified; however, further research is required to formulate strategies to overcome these barriers, and there may be other reasons for non-adherence that may not have been identified in this study due to the small sample size. Whilst prescribers might find the evidence to be clinically significant and it might have some degree of impact on their practice, there needs to be a large, full-scale, head-to-head interventional study directly comparing the two dosing strategies. A statistically significant difference might be found in a study of that nature in order for the new and emerging evidence to be accepted.