OBSTRUCTIVE SLEEP APNEA
Obstructive sleep apnea (OSA) is a major risk factor for intra- and postoperative complications, including post-extubation hypoxemia, hypercarbia, unplanned reintubation, pneumonia, all-cause respiratory failure, cardiac complications (including arrhythmia and myocardial injury), unplanned ICU transfer, longer length-of-stay, and even sudden death. (Ref 1-5) The use of sedative/ analgesic medications and the sleep deprivation that often occurs in the hospital both likely play a major role in these adverse events. (Ref 6)
Sleep-disordered breathing is common, affecting 20% of adults, with up to 7% with moderate or severe OSA, and studies have suggested that up to 80% of patients with OSA in the general population are undiagnosed. (Ref 7) These numbers are likely higher among surgical patients, especially candidates for bariatric surgery. (Ref 8) In patients with OSA, pre-op CPAP compliance has been shown to reduce postoperative complications. (Ref 9)
Assess for possible sleep apnea:
- Risk factors include obesity, old age, male sex, female menopause, alcohol intake
- Daytime somnolence / napping, non-restorative sleep, witnessed snoring or apneic episodes, awakening from sleep (restlessness, choking), morning headaches; consider using the STOP-Bang screening tool (inset) (Ref 10)
- Exam: Collar/neck size, BMI, HTN
- Workup: Consider if symptoms are severe and surgery is purely elective
- Gold standard: Overnight polysomnogram (PSG).
- Apnea-hypopnea index (AHI) = number of apneas+hypopneas / number of hours of sleep: 5-15 (mild), 15-30 (moderate), >30 (severe). CPAP machine covered by Medicare and Medicaid if AHI >15, or AHI >5 with severe symptoms or comorbidities (HTN, CAD, CVA etc) (Ref 6)
Patients with known OSA:
- Ascertain and document CPAP or BIPAP settings, type of mask (nasal vs. full face), amount of bleed-in oxygen (if any), and actual patient compliance
- If patients have an ill-fitting mask, refer back to their sleep clinic for mask refitting
- Remind patients to bring their mask and machine (labeled with their name) to the hospital
- Assess for signs and symptoms of pulmonary hypertension (see “Pulmonary Hypertension”) and right heart failure; consider echocardiogram in selected cases (see discussion)
- Consider obtaining a preoperative room air ABG, if mild hypoxia or evidence for daytime hypercarbia (e.g. elevated serum bicarbonate)
Alert anesthesia and operative team to the presence of known or suspected OSA before surgery
- Extubate to CPAP / BiPAP at home settings, and continue when asleep (naps and overnight)
- Close respiratory monitoring, especially with sedating medications (e.g. opiates)
- Consider ICU care, or continuous pulse oximetry monitoring if on floor care, depending on extent of surgery, severity of OSA, and compliance with CPAP
- Semi-upright (30-45 degrees) or lateral (side-lying) positioning
- If cannot tolerate CPAP or cannot use CPAP due to the surgical site, initiate supplemental O2 while sleeping (exercise caution in patients with concomitant COPD)
- Minimize opiate medications when possible (considering scheduled acetaminophen or NSAIDS to augment pain control in appropriate candidates)
Monitoring in patients with OSA after ambulatory surgery is controversial. Recent ASA practice guidelines (Ref 11) (based on expert opinion, but not on clear evidence) recommend observing patients for an additional 3 hours before discharge home, and if any episode of airway obstruction or apnea, monitoring should continue for additional 7 hours. These recommendations hold even for patients who undergo only regional anesthetic block.
We recommend very close attention perioperatively to patients with OSA. The appropriate setting for adequate respiratory monitoring is institution and surgery dependent—for example, our gastric bypass surgeons routinely admit patients with OSA to the ICU postoperatively.
At least mild pulmonary hypertension (PAH) is present in up to 50% of patients with OSA (Ref 12) , although it is an unusual cause of moderate or severe PAH. Many patients with OSA have dyspnea on exertion due to obesity and deconditioning, and edema due to venous stasis, without having right heart failure or PAH. Neck veins in these patients are difficult to assess. It is unknown to what degree screening for PAH by echo changes management or affects outcomes. The ACCP does not recommend routine evaluation for PAH in all-comers with OSA, but consideration of TTE in newly diagnosed patients who are set to undergo high-risk surgical procedures and/or are likely to receive high doses of postop opioids. (Ref 13)
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Updated May 2011