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A group of patients with obstructive sleep apnea syndrome (OSAS) experienced a greater number of serious complications following elective knee or hip replacement surgery than patients without the syndrome, according to researchers at The Mayo Clinic in Rochester, MN. In addition, this same group had longer lengths of stay following surgery.
The study involved 101 patients diagnosed with OSAS and a like number of matched controls. Serious complications occurred in 24 patients in the OSAS group, compared with nine in the control group. Lengths of stay were significantly longer for the OSAS patients at a mean plus or minus standard deviation of 6.8/2.8 days compared with 5.1/4.1 days for patients in the control group.
The results of the study confirmed most of the intuitive concerns of the researchers, according to one of the authors, Peter C. Gay, MD, associate professor at The Mayo Clinic Graduate School of Medicine, and a consultant in pulmonary critical care and sleep medicine, a division of Mayo’s department of internal medicine. "We certainly showed a marked increase in the number of complications and an increase in the length of stay by more than a day in patients who had obstructive sleep apnea," he notes.
The specific adverse outcomes also were anticipated, he says. "I think most of the ones you’d be concerned about in terms of the patients having breathing and lower oxygen problems should relate to complications of heart rhythm and the need for additional airway support, and that’s what the study showed," he observes.
It was these post-op complications that led directly to the longer lengths of stay for these patients, Gay continues. "There’s no reason to think they had additional medical problems, because they were matched for other complicating diseases," he explains. "There’s no real reason to think something over and above the complications required them to be observed for a longer period of time."
Gay and his group felt it was important to study the issue of sleep apnea patients undergoing elective surgery, because OSAS often goes undiscovered during pre-op evaluation. "There is very little scientific information available about what happens to patients with OSAS as they undergo elective surgery, although there are a few studies concerning such patients when they have upper airway operations," he notes. "However, it is intuitively obvious that a patient who stops breathing at night may get into trouble when filled with narcotics and put on his back," Gay explains.
"When you look at this historically, however, when a patient comes in for surgery and is asked if he has a heart problem, he will be very thankful that condition was reviewed. But it doesn’t impact on the patient that he should talk about snoring at night; he becomes disinterested and just wants that surgery done, so the issue gets pushed aside," he says.
In other words, Gay explains, not only do patients often fail to mention the condition, but physicians may underappreciate the necessity of evaluating this condition because of a lack of literature. "So we decided to look at it on an urgent care basis and get a fairly uniform group, and see what happens with OSAS patients if the condition is not carefully addressed," he says.
Gay and his colleagues plan to further explore this area by looking at evaluation and treatment before surgery. "This really is a mechanical problem — keeping the upper airway open when the muscles of the tongue and other structures are relaxed," he explains. "If we utilize a masked system called CPAP [Continuous Positive Airway Pressure], there is every reason to believe it will take care of the situation, provided it is applied immediately after surgery and in two to three days following surgery." That’s because patients often don’t sleep at all on the first day following surgery, but then rebound on the second or third day, he explains.
In this next study, Gay and his colleagues will use what he calls "some fairly simple questions" before surgery that may be predictive of the likelihood of having sleep apnea. "It’s likely to be shown that we can capture these patients and intervene before there’s a problem," he predicts. Gay will be using the Berlin questionnaire, first described in the 1990s in the Annals of Internal Medicine by Kingman Strohl. (See Berlin questionnaire, below.) Gay adds the patients may also be given CPAP after surgery.
The bottom line, says Gay, is that elective surgery patients "ought to be evaluated beforehand for OSAS." He adds that patients and their families should be better educated about the potential risks associated with OSAS. "What is needed is the recognition that the problem of sleep apnea, which is thought of in the lay community as just loud snoring, is much more than that," he says. "If your bed partner describes not breathing at night and is especially sleepy during the day or has high blood pressure, that all suggests there may be a significant risk."
For more information, contact: Peter C. Gay, The Mayo Clinic, East 18B, Rochester, MN 55905. Telephone: (507) 284-7940.