To address the challenges that anesthesiologists face perioperatively while managing patients with OSA, the Society of Anesthesia and Sleep Medicine (SASM) released new practice guidelines in Anesthesia & Analgesia(2016;123:452-473).

“OSA patients pose a two- to threefold risk of cardiac and pulmonary complications compared to a normal patient without OSA,” said Frances Chung, MBBS, FRCPC, chair of the SASM Preoperative Assessment Task Force, which reviewed 61 published, peer-reviewed articles consisting of 413,304 OSA patients and 8,556,279 non-OSA patients. All these articles showed an increased risk for complications from OSA with surgery. “This is the reason why we developed the guideline,” said Dr. Chung, who also is professor of anesthesiology and pain medicine at University Health Network, University of Toronto, and immediate past president of SASM.

This is an essential guideline for anesthesiologists to use during preoperative screening assessment and preparation of patients with known and unknown OSA, as well as treated and untreated OSA.

Dr. Chung said it is important that anesthesiologists be aware of suspected OSA patients and patients who are nonadherent to continuous positive airway pressure (CPAP) therapy. “Patients with suspected OSA and those who are not treated may receive opioids during and after surgery, which may cause issues,” she said.

The guideline recommends that patients fill out the short updated STOP-Bang sleep apnea questionnaire to identify suspected OSA (Figure). “This screening tool identifies, with reasonable accuracy, OSA cases,” Dr. Chung said. “We also advocate that a family doctor and/or surgeon attempt to identify patients who may have suspected OSA earlier in the process.”

The guidelines state that although a diagnosis of OSA may change postoperative outcomes, there is not enough evidence to support delaying or canceling surgery, with a few exceptions. Patients with obesity hypoventilation syndrome, severe pulmonary hypertension or resting hypoxemia may warrant further evaluation, including perhaps treatment, such as with CPAP. In these patients, further optimization is necessary to prevent postoperative complications (Table 1).

Figure. Updated STOP-Bang Questionnaire
Snoring?
Yes No Do you Snore Loudly (loud enough to be heard through closed doors or your bed-partner elbows you for snoring at night)?
Tired?
Yes No Do you often feel Tired, Fatigued, or Sleepy during the daytime (such as falling asleep during driving or talking to someone)?
Observed?
Yes No Has anyone Observed you Stop Breathing or Choking/Gasping during your sleep?
Pressure?
Yes No Do you have or are being treated for High Blood Pressure?
Body Mass Index more than 35 kg/m2
Yes No
Age older than 50 years old?
Yes No
Neck size large? (Measured around Adams apple) 
Yes No For male, is your shirt collar 17 inches/43 cm or larger? For female, is your shirt collar 16 inches/41 cm or larger?
Gender = Male?
Yes No
Scoring Criteria for general population

Low risk of OSA: 
Yes to 0-2 questions
Intermediate risk of OSA:
Yes to 3-4 questions
High risk of OSA:
Yes to 5-8 questions
or Yes to 2 or more of 4 STOP questions + male gender
or Yes to 2 or more of 4 STOP questions + BMI > 35 kg/m2
or Yes to 2 or more of 4 STOP questions + neck circumference (17”/43cm in male, 16”/41cm in female)
Proprietary to University Health Network. www.stopbang.ca

Modified from: Chung F et al. Anesthesiology 2008;108:812-821; Chung F et al. Br J Anaesth 2012;108:768–775; Chung F et al. J Clin Sleep Med 2014;10:951-958.
Table 1. Summary of Recommendations for Screening To Identify Patients With Suspected OSA
Recommendations Level of Evidence Grade of Recommendation
1.1.1 Patients with a diagnosis of OSA should be considered to be at increased risk for perioperative complications Moderate Strong
2.1.1 Adult patients at risk for OSA should be identified before surgery Low Weak
2.2.1 Screening tools such as STOP-Bang, P-SAP, Berlin, and ASA checklist can be used as preoperative screening tools to identify patients with suspected OSA Moderate Strong
2.3.1 Insufficient evidence exists to support canceling or delaying surgery to formally diagnose OSA in those patients identified as being at high risk of OSA preoperatively, unless there is evidence of uncontrolled systemic disease or additional problems with ventilation or gas exchange Low Weak
ASA, American Society of Anesthesiologists; OSA, obstructive sleep apnea

If available, it may be prudent to have the results of a sleep study and the patient’s recommended PAP setting before undergoing surgery. Similarly, if feasible, facilities may want to invest in PAP equipment for perioperative use or have patients bring their own PAP equipment to the surgery location.

“There is preliminary evidence that CPAP may provide some benefits to patients in the perioperative period,” Dr. Chung said. “For patients who are already on CPAP, we recommend that the therapy continue after surgery.” Setting adjustments may be required, however, for facial swelling, upper airway edema, fluid shifts, pharmacotherapy and respiratory function.

“Patients who are not adherent to CPAP need to be watched, and may require further monitoring or CPAP in the post-op period,” Dr. Chung said (Table 2).

Table 2. Best Preoperative Practices for Surgical Patients With Known OSA, Adherent or Nonadherent to PAP Therapy, or a High Probability of OSA
Recommendations Level of Evidence Grade of Recommendation
3.1 Surgical patients with OSA who are adherent to PAP therapy
3.1.1 The patient and the health care team should be aware that a diagnosis of OSA may be associated with increased postoperative morbidity Low Strong
3.1.2 Consideration should be given in obtaining the results of the sleep study and the recommended PAP setting before surgery Low Weak
3.1.3 Facilities should consider having PAP equipment available for perioperative use or have the patient bring their own PAP equipment to the surgical facility Low Strong
3.1.4 Patients should continue to wear their PAP device at appropriate times during their stay in the hospital, both preoperatively and postoperatively Moderate Strong
3.2 Surgical patients with OSA but decline or are poorly adherent to PAP therapy
3.2.1 The patient and the health care team should be aware that untreated OSA may be associated with increased postoperative morbidity Low Strong
3.2.2 Consideration should be given to obtaining the results of the sleep study and the recommended PAP setting before surgery Low Weak
3.2.3 Facilities should have PAP equipment for perioperative use or have the patient bring their own PAP equipment with them to the surgical facility Low Strong
3.2.4 Additional evaluation for preoperative cardiopulmonary optimization should be considered in patients with known OSA who are nonadherent or poorly adherent to PAP therapy and have uncontrolled systemic conditions or additional problems with ventilation or gas exchange such as: (i) hypoventilation syndromes, (ii) severe pulmonary hypertension, and (iii) resting hypoxemia in the absence of other cardiopulmonary disease Low Weak
3.2.5 Untreated OSA patients with optimized comorbid conditions may proceed to surgery, provided strategies for mitigation of postoperative complications are implemented. The risks and benefits of the decision should include consultation with the surgeon and the patient Low Weak
3.2.6 Patients should be encouraged to wear their PAP device at appropriate times during their stay in the hospital, both preoperatively and postoperatively Moderate Strong
3.3 Surgical patients who have a high probability for OSA
3.3.1 The patient and the health care team should be aware that a high probability of OSA may increase postoperative morbidity Low Strong
3.3.2 Additional evaluation for preoperative cardiopulmonary optimization should be considered in patients who have a high probability of having OSA and have uncontrolled systemic conditions or additional problems with ventilation or gas exchange such as: (i) hypoventilation syndromes, (ii) severe pulmonary hypertension, and (iii) resting hypoxemia in the absence of other cardiopulmonary disease Low Weak
3.3.3 Patients who have a high probability of having OSA may proceed to surgery in the same manner as those with a confirmed diagnosis, provided strategies for mitigation of postoperative complications are implemented. Alternatively, they may be referred for further evaluation and treatment. The risks and benefits of the decision should include consultation with the surgeon and the patient Low Weak
3.3.4 Patients should be advised to notify their primary medical provider that they were found to have a high probability of having OSA, thus allowing for appropriate referral for further evaluation Low Weak
OSA, obstructive sleep apnea; PAP, positive airway pressure

Because opioids may cause respiratory depression and impair the arousal response in OSA patients, anesthesiologists should adjust or titrate pain medication according to the needs of an individual patient, Dr. Chung said. “These patients may need postoperative monitoring.”

Furthermore, to better manage OSA patients overall, “there needs to be a collaborative effort among the surgeon, the family doctor, the patient and the anesthesiologist,” Dr. Chung said.

Unlike some of the previous practice guidelines, “ours is based on the most recent evidence, easy to implement and more cost-effective,” Dr. Chung said. However, further research is needed to delineate how best to risk-stratify OSA patients and how to optimize the preoperative assessment and preparation of patients with known and unknown, and treated and untreated, OSA.

—Bob Kronemyer


The STOP-Bang questionnaire is proprietary to University Health Network. Dr. Chung reported no relevant financial disclosures.

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