Mechanical prophylaxis for venous thromboembolism prevention in obese individuals

Obesity represents a significant risk factor for venous thromboembolism (VTE), with a relative risk increase of 2.5 for the development of deep vein thrombosis (DVT). Given the rise in rates of obesity, targeted efforts are necessary to refine and optimise VTE prophylaxis regimens for obese individuals. Mechanical and pharmacological prophylaxis remain the mainstay in VTE prevention. Current mechanical strategies to reduce venous stasis include graduated compression stockings (GCS) and active devices, such as intermittent pneumatic compression (IPC). Whilst mechanical prophylaxis is effective in preventing VTE compared to no intervention, its clinical utility has been cast into doubt, particularly as an adjunct to other strategies. Recently the PREVENT and GAPS trials, published in 2019 and 2020, respectively, showed no added benefit of mechanical prophylaxis when pharmacological prophylaxis was in place. The addition of pharmacological to mechanical prophylaxis with IPC, and vice versa, was the subject of a 2016 Cochrane Review. The meta-analysis performed showed that the addition of IPC to pharmacological prophylaxis reduced episodes of PE, with no difference in DVT or bleeding. However, the addition of pharmacological prophylaxis to IPC reduced the incidence of DVT at a cost of increased risk of bleeding, without impacting upon rates of pulmonary embolism (PE). A subsequent trial by Kamachi et al., which compared IPC with IPC plus pharmacological prophylaxis, found the addition of pharmacological prophylaxis yielded no difference in rates of either DVT or PE; it being noteworthy that all VTE episodes in this study were asymptomatic and detected on screening CT imaging. These findings in this recent trial may be driven, at least in part, by the wide-reaching advances in patient care that have been observed to drive down VTE rates, such as early mobilisation and enhanced recovery after surgery protocols, which may have contributed to underpowering in this study. Importantly, obese patients have been relatively underrepresented in past trials with, for example, obese patients’ inclusion ranging between 2.9% and 42% in the above trials. Impaired venous return worsened by increased intra-abdominal pressure, longer hospital admission and reduced mobility are proposed mechanisms for the increased risk of VTE in the obese patient group. Co-morbidities associated with obesity, such as varicose veins or impaired cardiac function, may further worsen venous return. As such, it is plausible that obese patients may particularly benefit from mechanical prophylaxis to counteract these contributors to venous stasis. Indeed, counteracting the immobility in stroke patients with IPC significantly reduced VTE incidence in the CLOTS 3 trial. Despite obesity being a VTE risk factor and the theoretical benefit of mechanical prophylaxis, there remains a lack of evidence in this area. This paucity of data was highlighted almost a decade ago by Freeman and colleagues yet, to the best of our knowledge, no trials have been initiated focusing on obese patients. A systematic database search performed by the authors of this editorial, combining relevant free text and MeSH terms relating to VTE, mechanical prophylaxis and obesity, found no studies investigating mechanical prophylaxis in obese patients outside of bariatric surgery, despite the number of trials investigating VTE prophylaxis in general. The use of mechanical prophylaxis in bariatric surgery was the subject of a recent systematic review. Limited evidence may be extrapolated from two observational studies investigating bariatric surgical patients, comparing IPC against the combination of