Adverse postoperative outcomes occurred in 24 percent of the patients with obstructive sleep apnea syndrome compared with nine percent of the patients in the study’s control group who did not have the syndrome. The study matched 101 patients with obstructive sleep apnea syndrome with 101 patients without it.
The study is published in the September issue of Mayo Clinic Proceedings. Authors of the study are: Rakesh M. Gupta, M.D., now of the Sleep Disorders Center, Roger Williams Medical Center, Providence, R.I.; Javad Parvizi, M.D.; Arlen D. Hanssen, M.D.; and Peter C. Gay, M.D. Drs. Parvizi, Hanssen and Gay are all with Mayo Clinic.
"Although we intuitively had concerns that obstructive sleep apnea patients undergoing surgery were at increased risk of complications, there is very little information about this," says Dr. Gay, the senior investigator in the study. "We are particularly anxious to bring these findings to the attention of both physicians and patients alike as the possibility of increased risk from sleep apnea during elective surgery is not often aggressively pursued. The next study we wish to pursue is to show that the evaluation and treatment of these patients beforehand, can actually help reduce the increased post-operative risks."
The prevalence of obstructive sleep apnea syndrome is estimated at five to nine percent and most often affects obese, middle-aged men. More than half of all cases of sleep apnea are diagnosed in people 40 years of age or older. The condition also is more common in men than women.
Obstructive sleep apnea occurs when the muscles in the back of the throat relax. These muscles support the soft palate, uvula, tonsils and tongue. When the muscles relax, the airway is narrowed or closed and breathing is momentarily cut off. This lowers the level of oxygen in the blood. The brain senses this decrease and briefly rouses the person from sleep so that the airways reopen. This awakening is usually so brief that a person doesn’t remember it. Breathing resumes, possibly with a snort. This pattern can repeat itself 10 times or more each hour, all night. A person is less able to reach the deep, restful phases of sleep and often feels sleepy during waking hours.
In general, only weight loss greater than 10 percent of body weight is thought to have any impact on symptoms caused by sleep apnea, the authors report from a previous study.
The authors also reported that the length of hospital stay was significantly longer for patients with sleep apnea (almost seven days) versus patients in the control group (five days).
Researchers say the frequency and severity of upper airway obstructions in patients with obstructive sleep apnea syndrome undergoing joint replacement are likely to be high for several reasons. First, because of the nature of the operation, these patients are expected to remain on their back after the operation. Second, uniform use of moderate amounts of intravenous narcotics after the operation is likely to precipitate or aggravate the respiratory complications in patients with obstructive sleep apnea syndrome.
The study also found that most complications occur in the first 24 hours. The authors suggest this may be due to the combined effect of the anesthetic agents, sedatives and narcotics, which tend to relax upper airway dilator muscles and increase upper airway resistance, thus aggravating obstructive sleep apnea syndrome.
Mayo Clinic Proceedings is a peer-reviewed and indexed general internal medicine journal, published for 75 years by Mayo Foundation, with a circulation of 130,000 nationally and internationally.
Contact:
John Murphy
507-538-1385 (days)
507-284-2511 (evenings)
e-mail: newsbureau@mayo.edu
Journal
Mayo Clinic Proceedings