May 26, 2006

Study questions lung injury treatment’s value

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Arthur Wheeler, M.D.

Study questions lung injury treatment’s value

Vanderbilt investigators have shown that pulmonary artery catheters (PACs), long used to treat acute lung injury patients, did not improve survival or organ function in these patients and were associated with more complications.

For more than a quarter of a century, it's been standard practice at hospitals worldwide to use PACs to help treat critically patients; more than 1 million receive them each year to evaluate intravascular pressure and cardiac output, or circulation.

Arthur Wheeler, M.D., associate professor of Medicine at Vanderbilt University Medical Center, led 20 centers in a randomized trial to compare two commonly used methods in the treatment of acute lung injury.

The findings were surprising, he admitted.

“What we found was unexpected,” said Wheeler, principal investigator. “The PAC was introduced into practice in the 1970s, but interestingly enough it has never been studied to establish that the benefits to patients outweigh the risks.

“Here is a tube that is put into a large vein and passed through the heart to measure pressure and blood flow, but no studies showed it helped patients. Over the years, some had begun calling into question the value and safety of this catheter.”

The ground-breaking study, “Pulmonary Artery — or Central Venous Catheter — Guided Treatment of Acute Lung Injury,” released in this week's issue of the New England Journal of Medicine, (May 25) recommends that PACs no longer be used in the routine care of patients with ARDS. Wheeler also presented the findings at the American Thoracic Society meeting in San Diego on May 21.

In the study sample, 1,000 ARDS patients were enrolled, with half receiving the PAC while the other half received the central venous catheter (CVC) during a seven-day period. Investigators noted three additional key points:

• Patients who received PACs suffered more complications, like non-fatal cardiac arrhythmias.

• PAC patients spent more time in the ICU.

• PAC patients received more transfusions.

“One of the reasons physicians used the catheters in critically ill patients was the belief that recovery would be faster, decreasing the need for ventilators and lowering the rate of other organ malfunctions, like kidney failure.

“We have proven otherwise. There were no improved outcomes with the PAC group.”

PACs are inserted to measure pressures leading to the left side of the heart and cardiac output — how much blood the heart ejects each minute. The CVC, which does not measure cardiac output, provides doctors the pressure in the superior vena cava, which leads to the right side of the heart.

Wheeler said the shorter, less expensive CVC is much easier to insert and the complications from placement are fewer.

Participating centers are members of the ARDS Clinical Research Network of the National Heart, Lung and Blood Institute (NHLBI), part of the National Institutes of Health, which is the funding arm for the study. Gordon Bernard, M.D., professor of Medicine, heads the steering committee of this group.

“This work culminates my efforts to explore the value of the PAC in ARDS that began when I co-chaired a meeting of the FDA and NIH in 1997,” Bernard said. “The work of that group led directly to additional NIH NHLBI support for this project that allowed us to investigate the risks and benefits of the PAC and produce current findings. It has been a long but gratifying experience.”

“Our goal is to do clinical research to improve the way patients received care,” Wheeler added. “We want to find ways to help people.”

Wheeler cautions that this study does not prove the catheter to be unsafe or not useful for patients with other conditions.

The study is the second to appear in NEJM in less than a month on the topic of treatment of acute lung injury patients by Wheeler and Bernard's study group. In the April issue, the network of centers debunked the belief that the use of corticosteroids in ARDS patients improves survival.

The study found that steroids temporarily improve physiological variables, but the ultimate outcome of the disease was unchanged and there was no improvement in survival.