Original contributionPreoperative identification of sleep apnea risk in elective surgical patients, using the Berlin questionnaire☆
Introduction
Sleep apnea is a disorder associated with increased risk of morbidity and mortality. Gupta and colleagues [1] have shown that persons with sleep apnea are more than twice as likely to undergo serious respiratory or cardiac adverse events after orthopedic joint replacement. This increased likelihood of adverse events may be related to the exquisite sensitivity of subjects with sleep apnea to opioid analgesic agents [2], [3]. Incidents of unexplained cardiopulmonary arrest after general anesthesia have been reported in association with sleep apnea [2], and have been linked to opioid administration [3]. Sleep apnea is also linked to difficult airway management and difficult intubation [4], [5]. Identification of sleep apnea before surgery allows the risk to be minimized by formulating a difficult airway/intubation plan, an appropriate anesthetic technique, and postoperative monitoring.
The “gold standard” for diagnosis of sleep apnea is an overnight sleep study (polysomnography). However, such testing is expensive, time-consuming, and clearly unsuitable for screening purposes. Questionnaire-based screening tools have been developed to identify the symptoms of sleep apnea [6], [7], [8], [9].
The literature indicates that the most widely used screening tool for detecting sleep apnea is the Berlin questionnaire. One study has assessed the validity of the Berlin questionnaire in identifying sleep apnea risk in the primary care setting [9]. Among US primary care (nonsurgical) patients, the Berlin questionnaire identified 37.5% of patients as being at high risk, demonstrating a sensitivity and specificity of 0.86 and 0.77, respectively, in identifying patients with more than 5 respiratory events per hour [9], [10]. The questionnaire consists of 9 items regarding snoring, witnessed apneic events, daytime sleepiness, and falling asleep while driving (Appendix). The purpose of this study was to use the Berlin questionnaire to identify the percentage of elective surgical patients at high risk of sleep apnea.
Section snippets
Materials and methods
Toronto Western Hospital ethics board approval was obtained before patients were recruited. A calculation of sample size requirement was made based on the finding of Harrison and colleagues [11] of a sleep apnea prevalence of 6.7% among elective orthopedic patients. To assess the prevalence with an accuracy of ±3% (95% confidence level), a sample size of 267 was calculated. Recruitment to the study continued until 305 patients were enrolled in the study. Patients were recruited during their
Results
The Berlin questionnaire identified 24% (73/305) of all patients as being at high risk of sleep apnea (Table 1) (95% confidence interval, 19%-29%). Nine patients in the study had been diagnosed previously with sleep apnea. The Berlin questionnaire correctly identified all these patients as being at high risk.
For 73 patients deemed to be at high risk of sleep apnea, their family physician was requested to refer them for polysomnography testing. Only 6 patients (of the 73) were referred. Of the 6
Discussion
In our study, 24% of elective surgical patients were identified as being at high risk of sleep apnea. This figure represented the number of patients at high risk of sleep apnea as identified by the Berlin questionnaire. The exact diagnosis of sleep apnea has to be confirmed by polysomnography. Prevalences as high as 24% have been reported among men in certain communities using sleep studies [12]. A large population-based study reported that based on an Apnea Hypoxia Index (AHI) score of 10 or
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Supported in part by the Department of Anesthesia, University Health Network-Mount Sinai Hospital, Toronto, Ontario, Canada.