Adding Pneumatic Compression to Heparin Therapy Does Not Reduce DVT in Critically Ill Patients

According to results from the PREVENT trial, adjunctive pneumatic compression plus pharmacologic thromboprophylaxis did not lower the risk of new lower-limb deep vein thrombosis (DVT) in patients who were admitted to the intensive care unit (ICU). The findings, which were published in the New England Journal of Medicine, suggest that pneumatic compression is unnecessary in this patient setting.

“In many ICUs, pneumatic compression is used in conjunction with pharmacologic thrombo-prophylaxis routinely,” study author Yaseen Arabi, MD, of the King Saud bin Abdulaziz University for Health Sciences in Saudi Arabia, told ASH Clinical News. “Our study shows that this practice does not provide an additional protection.”

The PREVENT (Pneumatic CompREssion for PreVENting Venous Thromboembolism) trial included medical, surgical, or trauma patients who were enrolled within a 48-hour period following admission to the ICU. The trial was conducted at 20 sites in Saudi Arabia, Canada, Australia, and India.

Patients were randomized 1:1 to one of the following treatment groups:

  • intermittent pneumatic compression (via knee-length, thigh-length, or foot-pump devices) plus pharmacologic thromboprophylaxis with unfractionated or low-molecular-weight heparin (n=991)
  • pharmacologic thrombo-prophylaxis only (n=1,012)

Participants who were randomized to the intermittent pneumatic compression group received compression to both lower limbs for at least 18 hours per day. Compression was discontinued when the researchers suspected or confirmed a DVT or pulmonary embolism or when ischemia or a leg ulcer was diagnosed.

In the control group, participants received intermittent pneumatic compression only when pharmacologic thromboprophylaxis was interrupted. Graduated compression stockings were not permitted in either group.

“The lack of benefit … highlights the importance of examining questions related to effectiveness of therapeutic interventions in randomized controlled trials.”

—Yaseen Arabi, MD

Proximal venous ultrasonography of both limbs was performed within 48 hours of randomization, then twice per week thereafter or if DVT was suspected.

The primary intent-to-treat analysis included 957 patients in the pneumatic compression group and 985 patients in the control group; 34 and 27 patients, respectively, were found to have pre-existing DVTs at study start.

Patients in the intervention group received pneumatic compression for a median of 22 hours (interquartile range [IQR] = 21-23 hours) per day for a median of seven days (IQR=4-13 days).

The primary outcome of the study (incident proximal lower-limb DVT until discharge from the ICU, death, full mobility achievement, or trial day 28, whichever occurred first) occurred in 3.9% of patients who received pneumatic compression and 4.2% of the control group. This translated to a statistically nonsignificant risk reduction of 7% with adjunctive pneumatic compression (relative risk [RR] = 0.93; 95% CI 0.60-1.44; p=0.74).

The authors also noted that there was no significant difference between the treatment groups regarding secondary outcomes, though p values were not provided):

  • prevalence of proximal DVT: 3.4% with pneumatic compression vs. 2.7% in the control group (RR=1.29; 95% CI 0.78-2.12)
  • prevalence of any lower-limb DVT: 9.6% vs. 8.4% (RR=1.14; 95% CI 0.86-1.51)
  • composite outcome of lower-limb DVT, pulmonary embolism, or death from any cause at 28 days: 23.3% vs. 24.0% (RR=0.97; 95% CI 0.83-1.14)

The lack of benefit with adjunctive pneumatic compression also was seen across all subgroup and sensitivity analyses, the authors added.

However, they noted that the lower-than-expected incidence of the primary outcome in the control group is a potential limitation of the study and reduced its power. “Consequently, our results do not rule out the possibility of a clinically important treatment effect (a benefit of as much as 40% or a harm of as much as 44%),” they wrote.

Other limitations include the trial’s unblinded design and the variability in the pneumatic compression devices used among participating centers.

“Previous smaller studies and observational work suggested that pneumatic compression is beneficial in reducing DVT risk when added to pharmacologic thromboprophylaxis,” Dr. Arabi explained. “The lack of benefit as demonstrated in PREVENT highlights the importance of examining questions related to effectiveness of therapeutic interventions in randomized controlled trials.”

The authors report no relevant conflicts of interest.

Reference

Arabi YM, Al-Hameed F, Burns KEA, et al. Adjunctive intermittent pneumatic compression for venous thromboprophylaxis. N Engl J Med. 2019;380:1305-15.

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