Study Shows Large Percentage of Surgical Patients With Undiagnosed Obstructive Sleep Apnea

Preoperatively, surgeons were not aware of the ongoing study and did not identify 90% of the patients who had severe OSA. Anesthesiologists did not diagnose 53% of these patients.

Singh M, Liao P, Kobah S, Wijeysundera DN, Shapiro C, Chung F

Br J Anaesth. 2013;110:629-636

4-29-13 SURG.2

Study Summary
The goal of this study was to better understand how many patients arriving to the operating room have undiagnosed obstructive sleep apnea (OSA). A better way to identify these patients ahead of time would be useful for tailoring the anesthetic as well as postoperative care and monitoring.

Singh and colleagues asked almost 6000 patients who were seen in a preoperative clinic in Toronto to enroll in this study, and 1085 agreed. After dropouts, 819 patients completed the study. Of the 819 patients, 111 patients had pre-existing OSA. The remaining 708 patients were screened for OSA.

First, patients answered the screening STOP-BANG questionnaire:

• Do you snore loudly (loud enough to be heard through closed doors)?

• Do you often feel tired, fatigued, or sleepy during the daytime?

• Has anyone observed you stop breathing during your sleep?

• Do you have or are you being treated for high blood pressure?

• Is your body mass index > 35 kg/m2?

• Is your age over 50 years old?

• Is your neck circumference > 40 cm?

• Are you male?

A person is deemed to be at high risk for OSA if he or she answers yes to 5 or more of the 8 questions.

The patients also underwent a sleep study (polysomnography) to measure the number of abnormal respiratory events (apnea or hypopnea) per hour of sleep. More than 30 of these events per hour is diagnostic for severe sleep apnea, as is an apnea/hypopnea index (AHI) score > 30.

Among the 708 study patients with no pre-existing diagnosis of OSA, 31% had no OSA, 31% had mild OSA (AHI: 5-15), 21% had moderate OSA (AHI: 15-30), and 17% had severe OSA (AHI > 30).

Preoperatively, surgeons were not aware of the ongoing study and did not identify 90% of the patients who had severe OSA. Anesthesiologists did not diagnose 53% of these patients. Overall, one third of patients with sleep study-identified OSA had only 1 or no cardinal symptoms of OSA. This indicates that these asymptomatic, “silent” patients are not going to be identified purely by history obtained by the physician.

More than 60% of the sleep study-identified patients with moderate and severe sleep apnea reported at least 2 symptoms suggestive of the diagnosis. These symptoms were daytime sleepiness (most common), witnessed apnea, and snoring. Singh and colleagues suggest that, had patients been screened before their surgeries with the STOP-BANG questionnaire, most cases of undiagnosed moderate and severe OSA would have been identified.

In patients with sleep apnea, perioperative pulmonary complications after orthopaedic and general surgery are significantly more frequent vs matched samples without sleep apnea, according to new research.

Stavros Memtsoudis, MD, with the Weill Medical College of Cornell University, in New York, NY, and colleagues reported their findings in Anesthesia & Analgesia.

Sleep apnea increased the risk for perioperative tracheal intubation and mechanical ventilation by 5-fold after orthopaedic surgery and doubled the risk after general surgical procedures, the researchers report.

References
1.  Gross JB, Bachenberg KL, Benumof JL, et al. Practice guidelines for the perioperative management of patients with obstructive sleep apnea: a report by the American Society of Anesthesiologists Task Force on Perioperative Management of patients with obstructive sleep apnea. Anesthesiology. 2006;104:1081-1093.

2.  Giarda M, Brucoli M, Arcuri F, Braghiroli A, Valletti PA, Benech A. Proposal of a presurgical algorithm for patients affected by obstructive sleep apnea syndrome. J Oral Maxillofac Surg. 2012;70:2433-2439.

3.  Seet E, Chung F. Management of sleep apnea in adults – functional algorithms for the perioperative period: Continuing Professional Development. Can J Anaesth. 2010;57:849-864.

Anesthesiologists worry that such patients will be at higher recovery risk, especially when discharged home on opioids for pain. These patients may also have a higher incidence of difficult intubation, postoperative complications including delirium, increased admissions to the intensive care unit, and longer hospital stays.

Almost one fifth of surgical patients have previously undiagnosed severe OSA. These patients were only diagnosed because they agreed to be enrolled in this study. As the investigators commented, the disparity between a high prevalence of undiagnosed OSA in the population and the low level of recognition and diagnosis at the time of preoperative consultation by surgeons and anesthesiologists is important.

It should be possible to reduce the proportion of undiagnosed severe OSA by implementing a formal screening tool as part of the routine preoperative anesthesia assessment. The results of screening can be used to determine whether a formal sleep study is indicated. In addition to the American Society of Anesthesiologists[1] practice guidelines, functional algorithms have been published that recommend preoperative screening.[2,3] This information has value beyond the benefits to anesthesia care. After being diagnosed with OSA, the patient can be referred to an internist or sleep physician to receive proper long-term treatment after the operation.

Source of information: MedScape

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