What’s New in the Patient Safety World

November 2010

More on Preoperative Screening for Obstructive Sleep Apnea



In our August 17, 2010 Patient Safety Tip of the Week “Preoperative Consultation – Time to Change” we noted one important condition to think about during the preoperative consultation or preoperative evaluation is obstructive sleep apnea (OSA).


We’ve talked previously about some of the dangers of obstructive sleep apnea (OSA) in the postoperative period and how to screen for them (see our Patient Safety Tips of the Week for June 10, 2008 “Monitoring the Postoperative COPD Patient” and August 18, 2009 “Obstructive Sleep Apnea in the Perioperative Period” and our July 2010 What’s New in the Patient Safety World column “Obstructive Sleep Apnea in the General Inpatient Population”). In patients scoring high on a tool like the STOP or STOP-Bang questionnaire, you may need to approach them as likely having OSA even if they have not yet had confirmation by polysomnography.


Two clinical studies just presented at the ANESTHESIOLOGY 2010 conference emphasize the need to identify OSA patients using screening procedures prior to surgery. One study done at the University of Toronto performed either standard nocturnal polysomnograms or portable home sleep studies on over 800 patients prior to anticipated surgery (surgeons and anesthesiologists were not informed of the results of those studies). Incredibly, 536 of the 819 patients enrolled had obstructive sleep apnea. Of those with severe sleep apnea, 85.5% were not diagnosed by surgeons and 47% were not diagnosed by anesthesiologists. Notably 84% of the patients overall had at least one symptom or sign of OSA such as snoring, excess daytime drowsiness, or observe sleep apnea.


In the second study, also from the Toronto group, the STOP-Bang questionnaire and a wristwatch pulse oximeter were used during the preoperative evaluation in 367 patients. Of these 61% were ranked at high risk for OSA using the STOP-Bang questionnaire. The accuracy of the data extracted from the pulse oximeter to detect moderate and severe sleep apnea was strong. The sensitivity to detect moderate and severe obstructive sleep apnea was 92.8 percent and 100 percent. The specificity to predict moderate and severe obstructive sleep apnea was 74.8 percent and 64.6 percent. There was a strong correlation between those scoring high risk on the STOP-Bang and those with an oxygen desaturation index greater than 10 on the wristwatch oximeter and having confirmed obstructive sleep apnea. The authors therefore suggest a screening process of administering the STOP-Bang, followed by the wristwatch pulse oximetry in those scoring as high risk.


Another group (Vasu 2010) just published a retrospective observational study correlating results of the STOP-Bang with surgical complications. They found that 41.5% of 135 patients who scored high risk on the STOP-Bang questionnaire had higher rates of postoperative complications than those who scored low risk (19.6% vs. 1.3%). They did not confirm OSA with polysomnograms so the association here is with the STOP-Bang score rather than confirmed OSA. Nevertheless, the association was strong and applied across a wide range of types of surgery. Using a cutoff of 3 on the STOP-Bang, they found a sensitivity of 91.7% and specificity of 63% for predicting postoperative complications, making the STOP-Bang a very good tool for screening to identify patients at high risk for postoperative complications.


In their discussion, they discuss how anesthesia, sedation, and analgesia may aggravate sleep-disordered breathing. They also note that REM sleep is diminished or absent on the first postoperative night but this is followed by REM rebound during subsequent nights and that REM-associated hypoxemic events may increase 3-fold on the second and third postoperative nights, with associated risk of complications. They further discuss management of suspected OSA in the perioperative period and use of nasal CPAP in preventing complications.


More good evidence that a simple, easy-to-administer tool can be very valuable in preventing complications in patients undergoing surgery.







American Society of Anesthesiologists. Studies Reveal a Need to Identify and Implement a Screening Procedure for Obstructive Sleep Apnea Prior to Surgery. Newswise 10/17/2010




Vasu TS, Doghramji K, Cavallazzi R, et al. Obstructive Sleep Apnea Syndrome and Postoperative Complications: Clinical Use of the STOP-BANG Questionnaire. Arch Otolaryngol Head Neck Surg. 2010; 136(10): 1020-1024













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