DVT prevention: Debate on prophylaxis vs. multimodal aspirin treatments continues

ACCP guidelines on DVT treatment may be insufficient for orthopedists, increase bleeds.

Issue: February 2007

On the issue of deep vein thrombosis prevention after joint replacement surgery, surgeons typically position themselves on one side of the fence or the other.

Some fear the worst and opt to use the strongest combatant, typically warfarin (Coumadin, Bristol-Myers Squibb), enoxaparin sodium (Lovenox, Sanofi-Aventis) or other low-molecular-weight heparin (LMWH). But with the risk of bleeding complications related to these drugs, others prefer to take a more conservative approach with aspirin and compression devices.

Robert B. Bourne, MD, FRCS, makes an argument for using drugs, such as LMWH. With older age comes a greater risk for thromboembolism, and at a time when more elderly patients are undergoing joint replacement surgery, routine use of LMWH might cover all bases in preventing deep vein thrombosis (DVT).

Robert B. Bourne, MD [photo]
Robert B. Bourne

But Lawrence D. Dorr, MD, takes a more conservative approach with multimodal treatments, including aspirin and intermittent pneumatic compression devices.

"Published data with multimodal treatments show that there is significant and equivalent benefit against pulmonary embolism and better benefit against death and bleeds," Dorr said. "In our personal experience with this treatment, we have not had a pulmonary embolism since 1985."

His and Bourne's comments came during the Current Concepts in Joint Replacement winter meeting.

High-risk population

Bourne routinely uses LMWH, not only because of an increasing older population, but because of the increasing number of joint replacement patients with malignancy, comorbidity, decreased mobility or prior history of venous thromboembolism.

He also said that evidence shows prophylaxis further decreases the mortality rate, and the risk of pulmonary emboli and blood clots.

"If you look at deep vein thrombosis, [in terms of preventing it] it is the most common preventable cause of hospital death," Bourne said. Furthermore, he said, massive pulmonary emboli typically occur without warning, leaving surgeons with limited time for resuscitation.

"There's a whole host of patients who ... develop post-thrombotic syndrome. We'd all like to prevent this no matter which way you approach it," Bourne said.

To reduce the bleeding risk, Bourne gives patients a half dose of LMWH on the first postoperative day or delays the first dose until the next morning.

Multimodal treatments

With the bleeding complications that surgeons see with LMWH and other prophylaxis, Dorr said, he sees no reason to use those drugs over the conservative method.

Lawrence D. Dorr, MD [photo]
Lawrence D. Dorr

Aspirin is sufficient for preventing clots, he said, and literature has shown that the death rate is similar regardless of treatment protocol in these patients. Bleeding complications occur four to 20 times more often with chemoprophylaxis than they do with aspirin and intermittent pneumatic compression devices, Dorr said.

"There has been a culture of fear that only ... these drugs will give us adequate protection against the formation of clots," Dorr said. "And that data is based on surrogate markers of deep venous thrombosis that are used to judge the efficacy of a drug." He added that decreased DVT does not necessarily mean a lower risk for pulmonary embolism. For example, total knee replacement (TKR) patients present with two to three times more DVTs than patients with total hip replacement (THR). But TKR patients are at lower risk for pulmonary embolism than THR patients.

"In this situation, more clots equals less pulmonary embolism," Dorr said.

Lack of effective guidelines

At present the only existing guidelines for preventing DVT are the American College of Chest Physicians (ACCP) Guidelines, which are based on 950 articles with Level 1 evidence, Bourne said.

"They found that low-molecular-weight heparin, fondaparinux and warfarin were the only agents that had Level 1 evidence to prevent venous thromboembolism," Bourne said.

But Dorr said these guidelines do not necessarily work for orthopedic surgery. A study by Barrack and colleagues even showed that using Lovenox based on the ACCP guidelines led to an unacceptable rate of bleeds, Dorr said.

Further, "The randomized studies on which [the ACCP] put the most emphasis ... were conducted by exclusion of all high-risk patients," Dorr said. "When you come up with an incidence of bleeding complications and bleeding deaths in the healthiest patients, it makes me question the validity of these randomized studies as the best treatment."

He also said that some studies are outdated and are therefore inapplicable because of today's different recovery techniques.

"Patients don't stay in bed 2 to 3 days or stay in the hospital for 1 week," Dorr said. "Patients are mobilized immediately and are out of the hospital, ambulatory and functional. That difference is significant in regard to occurrence of a clot."

While Bourne agreed with Dorr on these points, he added: "We have this document out there with Grade 1 evidence and I think it behooves us as orthopedists, if we're going to refute it, to have evidence that will stand up in peer review and prove it."

Dorr and his colleagues are attempting to do just that. They recently conducted a study on 1,179 surgeries in 970 patients treated with the multimodal protocol of aspirin and intermittent pneumatic compression devices. The 133 high-risk patients in the group received LMWH or warfarin in lieu of aspirin. The researchers performed ultrasound Doppler scans on all patients at 6 months. "There were no fatal pulmonary embolisms, a death rate of 0.4%, symptomatic clots were less than 5% and asymptomatic clots were less than 1%," Dorr said.

Dorr and his colleagues found that patients who received chemoprophylaxis had 35 times more bleeding incidents than the patients who received the multimodal treatment.

Treat to risk level

Neither Bourne nor Dorr rule out the other's treatment options for patients on different risk levels. Dorr uses his multimodal approach for low- or no-risk patients. But he gives Warfarin, instead of aspirin, for 6 to 12 weeks to high-risk patients, including those with thrombophilia or a history of DVT within the previous 5 years. In patients with a lower risk for DVT, Bourne typically uses the minimal amount of LMWH for 10 days with the first dose on the day after surgery.

"Hopefully with debates such as this, we will come up with some answers that you can take back to your every day practice," Bourne said.

For more information:
Dorr LD. DVT prophylaxis: Take aspirin, call me in the morning — Affirms. #96.
Bourne RB. DVT prophylaxis: Take aspirin, call me in the morning — Opposes. #97. Presented at the 23rd Annual Current Concepts in Joint Replacement Winter 2006 Meeting. Dec. 13-16, 2006. Orlando, Fla.
Robert B. Bourne, MD, FRCS, London Health Sciences Center, 339 Windermere Road, Rm. C9-122, London, Ontario N6A 5A5, Canada; 519-663-3512; robert.bourne@lhsc.on.ca. He indicated that he is a consultant for Smith & Nephew Orthopaedics. Lawrence D. Dorr, MD, The Dorr Arthritis Institute at Centinela Hospital Medical Center, 501 East Hardy Street, Suite 300, Inglewood, CA 90301; 310-695-4838; centinela.appts@tenethealth.com. He indicated that he is a consultant and independent contractor for Zimmer Inc.