Are Sequential Compression Devices Effective at Reducing DVT Risk in ICU Patients?

Aaron B. Holley, MD


May 23, 2019

When it comes to chemoprophylaxis to combat venous thromboembolism (VTE), the pendulum has swung both ways. Prior to 2011, guidelines tacitly endorsed defaulting to chemoprophylaxis for VTE in most hospitalized patients.[1] The rationale was threefold: Most patients would have VTE risk factors and benefit from chemoprophylaxis; individualized risk stratification was cumbersome and risk scores lacked external validation; and we needed to optimize administration of this proven preventive therapy and force providers to justify not using it. However, in 2011, when studies questioned the efficacy and risk-benefit of chemoprophylaxis, it fell out of favor as the default strategy.[2,3]

With this shift came a renewed interest in mechanical prophylaxis. Among the available forms, sequential compression devices (SCDs), also known as pneumatic compression devices, are the best studied and most commonly used. Some guidelines recommend them for specific patient groups,[4,5,6] while others recommend against them.[2,7] Proponents of SCDs support their use on the basis of a favorable side-effect profile and low bleeding risk. Detractors believe that there are few high-quality trials that demonstrate efficacy, and also that application is poor (ie, even when they're ordered, patients don't wear them, and doctors and nurses don't enforce their use). Physiology tells us that their anticoagulant effect does not persist beyond removal, so continuous use is required for protection against VTE.[8]

Recently entered into this debate is a large randomized controlled trial whose results were just published.[9] Researchers enrolled 2003 patients admitted to intensive care units at 20 different sites across Saudi Arabia, Australia, Canada, and India. All patients were given chemoprophylaxis with either low-molecular-weight or unfractionated heparin, with half randomly assigned to additional mechanical methods (different forms were allowed but most sites used SCDs) and half to chemoprophylaxis alone.

The patients in both groups were fairly sick, with a mean Acute Physiology and Chronic Health Evaluation (APACHE) score of 20 and 66% receiving mechanical ventilation. Lower-extremity ultrasound surveillance was performed twice weekly. The primary outcome was incident proximal lower-extremity deep vein thrombosis (DVT). Secondary outcomes included prevalent proximal DVT, all DVT, pulmonary embolism, various composites, and safety measures.

The trial was extraordinarily well conducted in its review of the data. Most important, the patients in the intervention group wore SCDs for a median of 7 days and 22 hours per day. This was matched by the control group, which received chemoprophylaxis alone consistently for 7 days. The authors reported no effect on the primary outcome or on any secondary outcome, and no effect when conducting sensitivity analyses.

When interpreting these results alongside previously published data, a few specific points are of interest. First, there was no difference in skin breakdown between the groups, and no major adverse safety events were noted. Although one could argue that there is a cost in time, labor, and equipment, this trial found SCDs to be safe. Second, overall VTE rates were lower than expected, so even with a large sample size, the trial may not have been powered to detect a small, incremental VTE reduction using SCDs in addition to chemoprophylaxis. Finally, the group studied isn't the one that I am most concerned about; more data are needed on the safety and efficacy in patients with contraindications to chemoprophylaxis who are at risk for VTE and only use SCDs. The CLOT-3 study provides the best data on efficacy in this group, although it's restricted to patients who are immobile from cerebrovascular accident, and it didn't require contraindications to chemoprophylaxis for enrollment.[10]

Most, if not all, guidelines recommend SCDs but lament the lack of high-quality evidence. More resources dedicated to studying high-risk patients with contraindications to chemoprophylaxis are needed.

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