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DURHAM, N.C. -- Using a database of nearly 1 million Americans who underwent major joint replacement surgery, a team led by researchers at Duke University Medical Center have determined those surgical patients with diabetes, hypertension or obesity were significantly more likely to suffer post-operative complications.

The team recommended that physicians and researchers evaluate treating such at-risk patients before surgery to control blood sugar, reduce blood pressure and prevent dangerous clot formation, to reduce the likelihood of complications.

These findings have broad implications for the health care delivery system, the researchers said, since more than 700,000 major joint replacement surgeries are performed annually in the U.S. at a cost exceeding $10 billion. Furthermore, as the incidence of diabetes, hypertension and obesity increases and the population ages, orthopedic surgeons must expect to see not only more, but sicker, patients and they will need to know how to effectively treat them, said the researchers.

Of three conditions that the researchers studied, obesity conferred the highest risk of post-operative complications and the need for additional post-discharge care.

The findings of the Duke analysis were published June 1, 2005, in the journal Clinical Orthopaedics and Related Research.

"Hypertension, diabetes and obesity are important independent predictors of increased complications for patients undergoing major joint replacement surgery," said the study's first author Nitin Jain, M.D., currently a post-doctoral fellow at Brigham & Women's Hospital, Harvard Medical School. He conducted the study as a research associate in the laboratory of Duke orthopedic surgeon Laurence Higgins, M.D., senior member of the research team.

"The results of our study should may surgeons to more accurately predict which of their patients are most likely to have adverse outcomes after their surgery," Jain continued. "With this knowledge, surgeons should not only be able to better counsel their patients before surgery, but also consider strategies during and after surgery to ensure better outcomes. However, the risks and benefits of a joint replacement procedure should be weighed by surgeons on an individual patient basis. "

Specifically, in their analysis of patients undergoing hip, knee or shoulder replacement surgery, the researchers found that 3.7 percent of obese patients experienced in-hospital complications, compared to 2.6 percent for non-obese patients. For patients with hypertension, the rates were 2.8 percent versus 2.6 percent, and for patients with diabetes, the ranges were 2.9 percent versus 2.6 percent.

Furthermore, the likelihood of a "non-routine" discharge from the hospital was 30 percent higher for diabetics and 45 percent higher in obese patients -- for patients with diabetes who were also obese, the likelihood rose to 75 percent. Non-routine discharges are those to another facility where further care is necessary, such as short-term hospitals, intermediate care facilities or home health care.

For their analysis, the team consulted the Nationwide Inpatient Samples (NIS) database. The NIS, sponsored by the U.S. Agency for Healthcare Research and Quality, is a publicly available database of more than 8 million patients from more than 1,000 U.S. hospitals. The hospitals vary by region, size, location, teaching status and ownership.

The Duke team's analysis identified 959,839 patients who received knee, hip or shoulder replacements between 1988 and 2000. Overall, the patients tended to be white (64.2 percent) and female (64.6 percent) with an average age of 70.8 years.

"This database is a very powerful tool that can give us real-life answers for patients and physicians facing major joint replacement surgery," Higgins said. "Past studies have included much smaller numbers of patients or were conducted at a single center. The NIS is a true reflection of what is happening across the country.

"In this case, the analysis identified a subset of patients who are at increased risk for worse outcomes," Higgins continued. "Our study demonstrates the need for clinical protocols and guidelines specifically aimed at patients with these comorbidities, as well as the need for adequate assessment of the risks and benefits of joint replacement procedures in these patients."

While further studies are needed to find strategies to reduce complication rates, the researchers said that strategies such as better control of blood glucose levels and blood pressure during surgery need to be evaluated as possible ways to improve the outcomes for patients with diabetes and high blood pressure. They also recommend that the use of blood-thinning drugs post-operatively to prevent the formation of deep vein thrombosis (DVT), in which clots that can form deep in muscles during extended periods of inactivity can break loose to cause heart attacks or stroke, be evaluated.

The researchers plan to refine their analysis to include other complicating factors as well as additional complications. They also will investigate whether outcomes are influenced by health care delivery factors, such as the volume of cases performed by individual surgeons and hospitals, or patient characteristics such as age, gender and race.

The analysis was supported by Duke's Center for Excellence in Surgical Outcomes (CESO).

Other members of the research team, who are also CESO members, were Ulrich Guller, M.D., University of Basel, Switzerland; Thomas Bond, M.D., Louisiana State University Health Sciences Center, New Orleans; and Shamsah Kazani, University of Buffalo, N.Y. Duke's Ricardo Pietrobon, M.D., Ph.D., research director of CESO, was also a member of the team.