By Christian Bohringer, MD, MBBS
About one-third (35%) of Americans are considered obese, which is defined as having a body mass index (BMI) greater than 30 kg/m2. In addition to its association with serious health risks, obesity is a primary risk factor for the development of sleep apnea (Romero-Corral, Caples, Lopez-Jimenez, & Somers, 2010). Sleep apnea is characterized by repetitive episodes of complete or partial upper airway obstruction while sleeping; it is twice as likely to occur in patients with obesity (Peppard, Young, Palta, Dempsey, & Skatrud, 2000).
Obesity and sleep apnea are associated with the recent reduction of life expectancy in the United States.
Yet while sleep apnea affects 9%–24% of the general population—or 29.4 million American men and women, according to the American Academy of Sleep Medicine (AASM)—more than 90% of cases remain undiagnosed.
For undiagnosed individuals, surgical procedures may present a serious risk. Sleep apnea patients have been shown to be more difficult to ventilate by face mask (Kheterpal, Martin, Shanks, & Tremper, 2009) and more difficult to intubate (Corso et al., 2011), although the availability of new airway equipment like high-flow nasal cannulas and video laryngoscopes have helped to mitigate these difficulties. Additionally, sleep apnea patients have been shown to have a higher rate of postoperative complications like hypoxemia, reintubation, unexpected ICU admission, atrial fibrillation, and heart failure after receiving a conventional anesthetic (Holt, Downey, & Naughton, 2019).
Undiagnosed apnea also siphons scarce health resources. An economic analysis conducted for AASM estimates that undiagnosed obstructive sleep apnea cost the United States approximately $149.6 billion in 2015, and that diagnosing and treating every patient in the United States who has sleep apnea would produce an annual economic savings of $100.1 billion (Frost & Sullivan, 2016).
Clearly, a more diligent approach to diagnosing sleep apnea is necessary. Anesthesiologists can play a key role in community health by identifying these patients throughout the surgical process, carefully monitoring them in the postoperative period, and helping to steer them into treatment.
The preoperative anesthesia consultation represents the first opportunity to identify undiagnosed apnea. A history of snoring and intermittent episodes of stopping to breathe at night should be elicited from the patient’s spouse or other housemates. Daytime somnolence and episodes of narcolepsy, like falling asleep while talking to somebody or while driving a vehicle, further raise the suspicion. Age greater than 50 years, a large neck circumference, and male gender also are associated with higher risk (Chung, Abdullah, & Liao, 2016).
Importantly, sleep apnea can also occur in the absence of obesity when patients have a sleep apnea phenotype with an upper airway anatomy that predisposes them to airway obstruction (Holt et al., 2019). Routine lab work and diagnostic testing can provide additional insights. High blood pressure and a BMI > 35 kg/m2 are associated with risk. If the sleep apnea is severe, the patient may have a high hematocrit due to a secondary polycythemia resulting from the recurrent nocturnal desaturation. Hypoxemia during sleep may also cause pulmonary hypertension; an echocardiogram can confirm a suspicion of right ventricular hypertrophy and pulmonary hypertension, which puts patients at high risk of perioperative death.
The administering of anesthesia during surgery presents a second key opportunity to identify apnea. Of course, it is impractical to delay surgery to obtain a sleep study in all patients that are potentially at risk, but every general anesthetic or sedation is basically the equivalent of a drug-induced sleep study. During surgery, anesthesiologists administer sedative drugs like the benzodiazepine midazolam or the alpha-2 agonist dexmedetomidine for anxiolysis in the preoperative area while we closely observe the patient’s breathing pattern. If these drugs lead to an obstructed breathing pattern even before the patient is asleep, sleep apnea is very likely.
In these cases, respiratory depressant drugs are risky; opioid-free surgery is the safest course. Opioid-free bariatric surgery has been shown to lead to equally good outcomes in patients with and without sleep apnea (Mulier & Dillemans, 2019). A multimodal regimen of drugs like dexmedetomidine, lidocaine, magnesium, intravenous acetaminophen, ketorolac, gabapentin, and ketamine is used as a replacement for opioids (Sultana, Torres, & Schumann, 2017). Unlike opioids, none of these medications has a significant respiratory depressant effect. Peripheral nerve blocks and spinal and epidural techniques are also excellent choices to reduce exposure to opioids if these strategies are not contraindicated by the clinical circumstances.
Finally, anesthesiologists carefully monitor patients in the postoperative period, given that the risk of respiratory arrest after surgery persists for several days and is greater when large doses of opioid drugs are required to achieve adequate postoperative analgesia. For patients with suspected sleep apnea, multimodal opioid-sparing analgesia needs to be continued well into the postoperative period. Additionally, patients at significant risk should be cared for in a closely monitored environment where urgent reintubation can be accomplished quickly if necessary.
After recovery, anesthesiologists can share their firsthand observations with the patient, discuss the possibility of sleep apnea, and refer them to clinicians who specialize in sleep disorders for assessment and treatment.
The high incidence of sleep apnea will probably remain with us for the foreseeable future as obesity rates in the United States and other developed countries are unlikely to decrease to their levels from 40 years ago. The U.S. healthcare system and clinicians in particular must therefore always be vigilant to consider the possibility of sleep apnea. Anesthesiologists are well positioned to identify undiagnosed cases of apnea, give these patients information about their condition, refer them to a sleep physician, and initiate the path to treatment. In this way, we will be able to prevent many premature deaths.
Christian Bohringer is a clinical professor of anesthesiology at UC Davis Medical Center in Sacramento, California. He serves on the Board of the California Society of Anesthesiologists.
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