Longer Stockings May Cut Risk for DVT in Stroke Patients, Study Reports

Neurology Today
2 December 2010; Volume 10(23); p 1, 29

Fitzgerald, Susan

Ultrasound scans identified proximal deep vein thrombosis in 6.3 percent of stroke patients who wore the thigh-length stockings, compared to 8.8 percent of patients who wore the shorter version.

THE STUDY provided a head-to-head comparison of the knee- and thigh-high stocking for preventing deep vein thrombosis after stroke.

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Stroke patients who wear thigh-length compression stockings are less likely to develop deep vein thrombosis (DVT) than patients who wear below-knee stockings, according to a new study that did a head-to-head comparison of the two stocking lengths.

Ultrasound scans identified proximal DVT in 6.3 percent of stroke patients who wore the thigh-length stockings, compared to 8.8 percent of patients who wore the shorter version, an international team of investigators led by Martin Dennis, MD, of the University of Edinburgh in Scotland, reported in the Nov. 2 Annals of Internal Medicine.

Those numbers indicate a 30-percent reduction in risk for DVT for patients who wore the thigh-high stockings. But the study is open to interpretation because of previous findings, and is unlikely to serve as the final word on what role stockings should play in the care of hospitalized stroke patients who are bedridden.

The study is the second of three conducted by the CLOTS [Clots in Legs Or stockings after Stroke) Trials collaborative study group, which was set up to assess the effectiveness of external compression for stroke patients. The study group is now studying the value of using intermittent pneumatic compression to reduce clot risk, but the results are not yet available.

Although many stroke patients receive low dose unfractionated or low molecular weight heparins, up to 20 percent of stroke patients, those with intracerebral hemorrhage, need a mechanical alternative, so the question is clinically relevant, experts not involved with the study told Neurology Today.

DR. MARTIN DENNIS:“In view of the lack of direct evidence for the effectiveness of below-knee stockings in any group of patients, this trial suggests that in cases where stockings are to be used, then thigh-length stockings should be chosen.”

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The current study involved 3,114 patients hospitalized for acute stroke (ischemic or hemorrhagic) at 112 hospitals in nine countries, including the United Kingdom, Italy, Ireland, Australia and the Czech Republic. To meet the definition of immobile, patients had to be unable to walk to the toilet on their own. Patients with subarachnoid hemorrhage and those with severe vascular disease or diabetic or sensory neuropathy were ineligible to participate.

About half of the patients were given thigh-length stockings and the other half were assigned the shorter version. The patients were instructed to wear the stockings day and night. About seventy-five percent of the patients wore the stockings for 30 days or until they were discharged, died or regained mobility, according to the report.

The patients underwent an ultrasound exam of both legs between seven to 10 days after enrolling in the study and again at about 25 to 30 days afterward, though not all patients had the second ultrasound. The study's primary outcome was the occurrence of symptomatic or asymptomatic DVT in the popliteal or femoral veins, detected on either scan.

“Proximal DVT occurs more often in patients with stroke who wear below-knee stockings than in those who wear thigh-length stockings,” the researchers concluded.

The two groups did not differ in survival, calf DVT, pulmonary embolism or adherence to wearing the stockings, according to the report. Skin breaks occurred in 3.9 percent of patients wearing thigh-high stockings and 2.9 percent of those wearing the shorter ones, but the researchers said the skin problems were usually mild.”

Although the study indicated an advantage to the longer stockings, its results are confusing when compared with the findings of the CLOTS 1 Trial, which were reported in The Lancet in 2009. In that study, the researchers compared stroke patients who wore thigh-length stockings to patients who went without stockings. The study found no statistically significant benefit to wearing the thigh-high stockings.

In this latest report, the researchers attempted to address their seemingly contradictory findings. “If thigh-length stockings are truly ineffective in patients with stroke, it may be surprising that they seem to be more effective than below-knee stockings,” they wrote. “One explanation is that below-knee stockings may increase the risk for DVT after stroke.”

A statistical analysis of data pooled from the two studies suggested that could be the case; another possibility is that the first study underestimated the benefit offered by the thigh-length stockings.

The investigators noted that they did “not systematically screen for pulmonary emboli with routine imaging, and that “many patients received anticoagulant therapy to lessen the risk for symptomatic events.”

But, Dr. Dennis told Neurology Today: “In view of the lack of direct evidence for the effectiveness of below-knee stockings in any group of patients, this trial suggests that in cases where stockings are to be used, then thigh-length stockings should be chosen.

“At the moment most hospitals choose below-knee stockings by default, perhaps because they are cheaper and easier to fit. There should be a major change in practice wherever stockings are used unless evidence emerges that in situations such as surgery short stockings are as effective as long ones.”

Dr. Dennis and his team acknowledged some study limitations. Not all patients underwent a second ultrasound, for example. “Our inability to perform all scheduled compression duplex untrasonography, although unlikely to introduce bias, reduced the number of DVT events detected and therefore the power of our trial.”

Researchers not involved with the CLOTS study told Neurology Today that until more data are available from the third study on pneumatic compression stockings, the best approach for managing patients who have a contraindication to heparins is not yet known.

In comments to Neurology Today, Philip Gorelick, MD, director of the Center for Stroke Research at the University of Illinois College of Medicine at Chicago, noted that “in the US, the American Heart Association/American Stroke Association guidelines are weighted more heavily in the direction of administration of subcutaneous heparins and use of pneumatic compression devices.”

DR. PHILIP GORELICK:“In the US, the American Heart Association/American Stroke Association guidelines are weighted more heavily in the direction of administration of subcutaneous heparins and use of pneumatic compression devices.”

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Nneka Ifejika-Jones, MD, assistant professor of neurorehabilitation at the University of Texas Medical School at Houston, told Neurology Today that while she found the study to be interesting, she didn't think it would have a big impact on clinical practices.

“I know how difficult it is to get patients to comply with wearing below-knee stockings,” she said. “When I come into the room, they're often on the floor.”

Patients also will roll down the stockings to make themselves more comfortable.

She said thigh-high stockings can be particularly problematic because they “tend to slide down the thigh.” She said nurses would need to be trained to properly fit the thigh-high ones because one size does not fit all.

The study researchers noted, however, that even a modest per-patient advantage in using thigh-high stockings could add up to a large cumulative payoff.

“The 2.5-percentage point difference in absolute risk for proximal DVT may not seem to be of great clinical significance for individual patients…however, many patients worldwide are fitted with stockings for DVT prophylaxis, which suggest a potentially substantial effect on public health,” the researchers noted.

They concluded that until more data are available from the third CLOT study, which could provide more clarity on how best to treat stroke patients, it “would seem sensible that thigh-length stockings should be the preferred option, at least until robust evidence indicates that below-knee stockings are both as effective as thigh-length stockings and more effective than no stockings.”

The CLOTS (Clots in Legs Or stockings after Stroke) Trial Collaboration. Thigh-length versus below-knee stockings for deep venous thrombosis prophylaxis after stroke: A randomized trial. 2010;153:553-562.

Dennis M, Sandercock PA, Venables G, et al, for the CLOTS Trials Collaboration. Effectiveness of thigh-length graduated compression stockings to reduce the risk of deep vein thrombosis after stroke (CLOTS trial 1): A multicentre, randomized controlled trial.. 2009;373:1958-1965.