Preoperative evaluation of adults with sleep apnea
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Patients with sleep apnea present unique challenges in the perioperative period. Over half of patients with sleep apnea are undiagnosed at the time of surgery. I review how to assess risk in patients with suspected or confirmed sleep apnea.
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Preoperative evaluation of adults with sleep apnea
- 1. Preoperative Evaluation of Adults With or Suspected of Having Obstructive Sleep Apnea Terry Shaneyfelt, MD, MPH Assoc. Professor, UAB Department of Medicine
- 2. • Estimated 7% prevalence in presurgical patients (Anesth Analg 2010;110:1007) • Over 50% of patients with OSA who present for surgery are undiagnosed • OSA increases perioperative complications Background
- 5. Factors contributing to perioperative aggravation of OSA
- 6. • All patients should be screened but especially: • Obese patients (BMI ≥ 30kg/m2) • Bariatric surgery • Medical conditions in which OSA is prevalent (HTN, DM) • h/o difficult intubation • Upper airway characteristics that predict difficult intubation • STOP-Bang, Berlin, Sleep apnea clinical score ASA recommends screening for OSA (Practice Guidelines for the Perioperative Management of Patients with OSA Anesthesiology 2014;120:268-86)
- 7. Low risk of ASA: Yes on 0-2 Intermediate: Yes on 3-4 High risk: Yes on 5-8 (15.7 inches)
- 8. • Severity • Current symptoms • Sleep study • Adequacy of current treatment • Residual symptoms • adherence Assessment of patients with known OSA
- 9. Who needs further evaluation prior to surgery?
- 10. • OSA increases risk of a variety of postoperative complications • Patients should be screening for OSA esp if they are obese or have medical problems associated with OSA • No further evaluation is needed in low risk patients undergoing low risk procedures • No further evaluation is needed in patients with OSA who are well controlled and adherent to therapy Summary
Editor's Notes
- These PowerPoints will review preoperative evaluation of adults with or suspected of having OSA.
- The prevalence of OSA in presurgical patients in the largest study to date is estimated to be 7%. Previous studies that reported higher prevalence were blighted by selection bias. Unfortunately half of these patients are undiagnosed when they present for surgery. OSA increases the risk of a variety of postoperative complications including cardiac events. The figure above is from a study of over 2.6 million orthopedic procedures and over 3.4 million general surgical procedures. As can be seen OSA patients (black bars) have increased risks of aspiration, ARDS and intubation in the postoperative period compared to patients without OSA (grey bars)
- This systematic review shows a broader array of outcomes affected by OSA. In this figure both cardiac events and postoperative respiratory failure were significantly increased in patients with OSA. Note that the event rates were 3.8% for cardiac events and 1.96% for resp failure in OSA patients compared to 1.7% and 0.7% for non-OSA patients respectively.
- OSA patients had more postoperative desaturation (10.7% vs. 5.6%) and ICU transfer (5.1% vs. 1.6%). NOTE: both of these analyses had moderate heterogeneity.
- Several factors contribute to the perioperative exacerbation of OSA: Perioperative medications: sedatives, general anesthetics, opioids, neuromuscular blocking agents. These may reduce upper airway tone and inhibit protective reflexes. They may also reduce central respiratory drive. Upper airway narrowing: can be caused by postintubation edema, edema related to surgery, nasal tubes, etc Supine positioning: worsens upper airway collapse Sleep deprivation: its hard to sleep postoperatively due to anxiety, pain, hospital environment, etc). This also can lead to REM rebound (reestablishment of sleep patterns on 3rd or 4th hospital day leads to increased REM sleep, the stage during which OSA is most severe) Perioperative discontinuation of CPAP therapy- either forgotten at home, nausea, NG tube, or the surgical circumstances prevent its use.
- All patients should be screened for sleep apnea but especially those with the above conditions. Remember half of patients with OSA are undiagnosed prior to surgery. Thus screening is important. There are 3 instruments that can be used to screen for OSA.
- This is the STOP-Bang instrument. The total number of “Yes” answers are tallied and risk is then determined as noted at the bottom of the slide. I prefer this instrument because it has undergone wider validation that the other instruments. The Berlin questionnaire is also very popular. Adding serum bicarbonate > 28 mmol/L to a STOP-Bang score of 3 improves the specificity for moderate to severe OSA. These patients should be treated as if they have a STOP-Bang score of 5 or greater.
- Preoperative evaluation of patients with known OSA should include an assessment of the severity of sleep apnea and the adequacy of treatment. Severity of OSA can be assessed by evaluating current symptoms or by results of a sleep study. Poorly controlled symptoms might mean more severe OSA and may indicate the need for further evaluation and treatment prior to surgery. The apnea-hypopnea index (total number of apneic and hypopneic episodes/hour) is used to judge the severity of OSA as seen in the table. (apnea is cessation of breathing for at least 10 seconds and hypopnea is overly shallow or abnormally slow breathing) Adequacy of treatment is assessed by asking patients using therapy about residual symptoms. It is important to ask about adherence and any issues with equipment. Its also a good time to remind them to bring their equipment to the hospital on the day of surgery.
- Most patients will have low risk OSA, be adequately treated, or undergoing low risk procedures. These patients can go directly to surgery with no further testing or treatment. Surgery should be delayed in patients undergoing high risk surgical procedures (major invasive surgery that will impact airway or cardiopulmonary function and those that will require substantial post op opioid medications) and those with moderate to severe OSA (or high risk of OSA) that is not optimally managed. High risk patients might need a sleep study for diagnosis or optimization of therapy. Underlying comorbid conditions might need to be optimized also prior to surgery. See my presentation and/or video on perioperative management of OSA for more details on optimization of OSA prior to surgery and postoperative management of the sleep apnea patient.