[ Back to EurekAlert! ] Public release date: 28-Jun-1999
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Contact: David Williamson
David_Williamson@unc.edu
919-962-8596
University of North Carolina at Chapel Hill

UNC-CH study shows compressed air sleeve prevents blood clots during hip replacement

Chapel Hill - Surgeons at the University of North Carolina at Chapel Hill have discovered they can almost always prevent life-threatening blood clots from forming during total hip replacement surgery.

They have their patients wear a sterile, inflatable sleeve over the leg as it's being operated on and for a few days afterwards. Inflating and deflating in waves, the sleeve stimulates blood flow inside leg veins comparable to the flow walking and other movements produce.

The procedure, which adds just a few minutes to preoperative preparations, avoids the need for blood-thinning drugs such as heparin and warfarin. Those drugs also prevent clot formation and have been widely used for many years, the surgeons say, but they significantly boost the risk of dangerous bleeding in the hip or elsewhere.

A report on the clinical study appears in the May issue of the Journal of Bone and Joint Surgery, an orthopaedic surgery journal. Authors are medical student Jennifer A. Hooker and Drs. Paul F. Lachiewicz and Scott S. Kelley, professor and associate professor of orthopaedic surgery, respectively, at the UNC-CH School of Medicine.

"Total hip replacement is very common now and is the most effective treatment for arthritis and other painful conditions of the hip in adults," Lachiewicz said. "Probably the most common early complication of the operation is developing blood clots in the legs, also called thrombophlebitis or thromboembolism."

Such clots can produce pain and swelling, he said, but the most serious complication results when they break off and flow to the lungs, causing pulmonary embolism and sometimes death. Blood-thinning drugs can cause excessive bleeding during and after the surgery and other serious complications.

"We came up with the idea that we might be able to avoid the drugs and still prevent blood clots at the same time by using what we call intermittent pneumatic compression and a spinal anesthetic, which also helps reduce clot formation, possibly by preventing blood vessels from going into spasm," Lachiewicz said. "Clots can form during operations because the legs don't move, and surgeons, who have to twist the leg as they replace the hip joint, are probably kinking leg veins."

Beginning in 1991, the UNC-CH surgeons asked the Kendall Corp. of Boston to make them a sterile version of an inflatable plastic sleeve they could have patients wear for the first time during operations. Other doctors had fitted patients with non-sterile sleeves only after surgery, but that seemed likely to be less effective, the two thought.

More than 500 hip replacements later, technicians performing sophisticated Doppler ultrasound examinations of patients' veins at UNC-CH's Peripheral Vascular Laboratory found no symptomatic deep vein clots while those patients were hospitalized. Only three patients showed partial lung blockages during hospitalization, but no one died from blood clots trapped in the lungs.

Fewer than 5 percent of patients showed any clot formation, and those did not cause noticeable symptoms. Only three patients developed symptoms after discharge up to 22 weeks later.

"These results are pretty darn good," Lachiewicz said. "They mean we don't have to worry about patients bleeding too much because we don't have to use drugs to thin out their blood. Using the pneumatic compression during surgery makes total hip replacement safer not just for healthy people but for everybody including the elderly."

The study demonstrated the effectiveness of the pneumatic sleeve technique for preventing both deep vein thrombosis and pulmonary embolism, he said. Using them during and for several days after hip replacement reduced the rate of both complications. Earlier patients who had not had the inflatable devices placed around their legs served as control subjects and provided comparison figures.

"The overall prevalence of thromboembolism was similar to that reported with either warfarin or heparin, but there were fewer serious bleeding complications," the surgeon said.

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Note: Lachiewicz can be reached at 919-966-9073.
Contact: David Williamson, 919-962-8596.




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