Risk Factors Identified for Complications After Sleep Apnea Surgery

SEATTLE, Oct. 16 -- Surgery to correct obstructive sleep apnea (uvulopalatopharyngoplasty) is more likely to have complications if the conditions is severe, a concurrent retrolingual procedure is done, BMI is high, or there are medical comorbidities, found a VA study.

After uvulopalatopharyngoplasty, each additional illness besides sleep apnea almost doubled the risk of serious complications, and having a concurrent non-nasal procedure increased the complication risk almost fivefold compared with noncurrent procedures, according to a report in the October issue of the Archives of Otolaryngology--Head and Neck Surgery.

However, because of the low complication rate in this study, it was not possible to determine individual significance of the risks and whether they were independent of one another, said Edward Weaver, M.D., of the University of Washington here and colleagues. The cumulative complication risk of having a current separate retrolingual procedure is also unknown, he added.

Previous multisite studies of patients who had surgery for obstructive sleep apnea have found an overall 1.6% rate of serious complications, including a 0.2% 30-day mortality rate. But previous reports of risk factors for complications have been conflicting, Dr. Weaver's team said

The VA study was in two parts. The first included a prospective cohort of 3,130 consecutive patients (97% men, mean age 50) who had uvulopalatopharyngoplasty (including tonsillectomy) from 1991 to 2001. The patients, from the Veterans Affairs National Surgical Quality Improvement Program database, were analyzed to determine the relationship between perioperative complications and either medical comorbidity or having a concurrent procedure.

Demographic and health variables included age, sex, race, smoking status, and year of operation, a potential confounder because of temporal trends associated with practice patterns.

In this part of the study, 51 patients (1.6%) had complications, the researchers reported.

Comorbidities were associated with serious complications (adjusted risk ratio, 1.96, 95% confidence interval, 1.16-3.18) for each increase in the American Society of Anesthesiologists (ASA) class.

Concurrent nonnasal procedures also increased the complication risk compared with non-concurrent procedures (adjusted risk ratio, 4.94, CI, 2.34-10.4). Nonnasal procedures included various retrolingual surgeries.

Sixteen specific serious complications were identified in the database. These included 30-day mortality; respiratory events (reintubation, pneumonia, prolonged ventilation emergent tracheotomy, or pulmonary edema); cardiovascular events (cardiac arrest, myocardial infarction, cerebrovascular accident, or pulmonary embolism). Other complications included serious hemorrhage, coma, wound infection, deep venous thrombosis, renal failure, and systemic sepsis.

In the large cohort group, most patients had few major comorbid conditions: 79% had none, 14% had one, 6% had two, and 1% had more than two major conditions. About half of the patients had at least one concurrent upper airway procedure, most commonly a nasal procedure.

In the second part of the study, data on BMI, apnea-hypopnea index (disease severity), and oxygen saturation were collected from a nested case-control subset study of 43 of 51 veterans from the original cohort with complications and 212 matched controls.

In this subgroup, the apnea-hypopnea index, body mass index, and medical comorbidity were each associated with serious complications after adjustment for confounding variables.

However, this study had insufficient power to determine whether these risk factors were independent of one another, the researchers said. The same held true for the lowest oxygen saturation, which was not associated with serious complications, Even so, the authors said, the sample size was inadequate to rule out a small effect.

Having another retrolingual procedure at the same time was also independently associated with a serious complication after adjustment for confounders, but the cumulative risk of separate retrolingual procedures is unknown, the investigators wrote.

The study's limitations included the lack of data on sleep apnea severity and obesity in the prospective database, whereas the case-control analysis depended on the accuracy of recording sleep study results, medical comorbidity, and BMI in the medical records.

Perioperative management may also play a role in the likelihood that serious complications will develop, the investigators noted.

Despite the large sample size, the rare number of serious post- surgery complications may "render this study inadequately powered to isolate the independent significance of various risk factors," Dr. Weaver said.

Finally, he said, because the data came exclusively from veterans, the findings may not be generalizable to all adult patients, because, for example, on average veterans are sicker. On the other hand, he said, the large cohort size, broad geographic distribution, inclusion of various sleep apnea procedures, and variety of surgeons adds to the generalizability of this study.