March 16, 2010 (New Orleans, Louisiana) — Patients with obstructive sleep apnea (OSA) are at high risk of developing serious complications after hip or knee replacement surgery, according to a new study presented here at the American Association of Orthopaedic Surgeons 2010 Annual Meeting.

"These patients have higher rates of acute renal failure, as well as low oxygen blood levels and longer hospitalization after surgery," said lead researcher Javad Parvizi, MD, professor of orthopaedic surgery at Thomas Jefferson University in Philadelphia, Pennsylvania. "For this reason, it is recommended that these patients be monitored very carefully during recovery after surgery."

Concern about these patients led the investigators to implement a stringent surveillance protocol, which has been in place for the past 10 years.

"Once patients have been diagnosed with obstructive sleep apnea at our sleep center, they are treated with [continuous positive airway pressure, bilevel positive airway pressure], and, in some cases, uvulopalatopharyngoplasty," Dr. Parvizi told Medscape Orthopaedics.

After surgery, patients are placed in a "step-down" unit, where they are monitored with 1-to-1 nursing overnight so that any complications that arise can be dealt with immediately.

The anesthesia technique for these patients is also modified. No opioids are given and their oxygen saturation is optimized both during and after surgery. These patients are also kept in hospital for a slightly longer period to help ensure that their postop recovery is smooth, Dr. Parvizi explained.

In this study, they investigators sought to evaluate the impact of OSA on postoperative complications in patients undergoing hip or knee replacement, and to assess the effectiveness of their vigilant monitoring of these patients.

They reviewed their computerized database and identified 1016 patients with a clinically suspected or objectively documented diagnosis of OSA who underwent total joint replacement surgery between January 1998 and January 2008.

Of these, 418 patients underwent primary total hip replacement, 68 had revision hip replacement, 448 had primary total knee replacement, and 82 had revision knee replacement surgeries.

These patients were matched with 1016 control patients who underwent similar surgery but who did not have OSA.

The patients with OSA were significantly younger than the control patients, Dr. Parvizi reported. There were no differences between the 2 groups in the incidence of peripheral vascular disease, cerebrovascular disease, liver and kidney disease, cancer, or dementia. However, OSA patients were more likely to have a history of myocardial infarction, congestive heart failure, chronic obstructive pulmonary disease, and diabetes.

The study found that patients with OSA experienced higher rates of acute renal failure than control patients (16 vs 5 patients; P = .0200). They also experienced significantly higher rates of oxyhemoglobin desaturation, defined as less than 92%, than control patients (P = .0022), although the rate of severe oxyhemoglobin desaturation (<88%) was similar in both groups (P = .2000).

As per the protocol, which kept patients with OSA in hospital for a longer duration, there was a trend toward longer hospitalization in the OSA group than in the control group (4.49 vs 4.29 days; P = .0552).

There were no significant differences in other complications between the 2 groups.

"Implementing all of those intense monitoring strategies allowed us to minimize the risk of cardiopulmonary complications in this vulnerable patient population, but they still had a higher incidence of acute renal failure," Dr. Parvizi said during an interview withMedscape Orthopaedics. "This patient population remains challenging, and we believe that it is very important to invest more research into this problem and then allocate the resources appropriately to prevent them from running into problems in the postoperative period."

Douglas E. Padgett, MD, chief of Adult Reconstructive Service at the Hospital for Special Surgery in New York City, who moderated the session, told Medscape Orthopaedics that the study provides important information that demonstrates that there are not just pulmonary concerns, there are also cardiovascular-related problems with patients with OSA, probably because of "vascular dynamics following the surgery."

He suggested that, in addition to intensive monitoring, measures to improve cardiac output during the surgery should be considered in these patients.

"At our institution, we use regional anesthesia as opposed to general anesthesia, and we use modalities to maintain high cardiac output to mitigate these complications and problems."

Dr. Parvizi reports financial relationships with Stryker Orthopedics, Pfizer, Adolor, Cubist, 3M, Kimberly Clark, Ortho McNeill, Smartech, Smith and Nephew, Aircast, the Knee Society, and CyruMed. Dr. Padgett has disclosed no relevant financial relationships.

American Association of Orthopaedic Surgeons (AAOS) 2010 Annual Meeting: Abstract 492. Presented March 12, 2010.

Article by Fran Lowry, Medscape Medical News © 2010 Medscape, LLC