POSITIVE RESULTS Since CPAP therapy may reduce the risk of cardiovascular events, patients should wear their devices both pre- and post-operatively.

Chances are, there are patients with obstructive sleep apnea sitting in your waiting room or lying in your pre-op bays right now. And they might not even know they have OSA. To help you recognize and treat the condition, Frances Chung, MBBS, FRCPC, a professor of anesthesia at the University of Toronto, recently chaired a task force to update guidelines for screening and assessing adult OSA patients (osmag.net/x4xssv). Here are the key takeaways.

• Proceed in most cases, but with caution. Is sleep apnea reason enough to delay or cancel surgery? No, says the task force — only if patients have additional problems that suggest disturbed ventilation or gas exchange. These include evidence of hypoventilation, severe pulmonary hypertension or resting hypoxemia in the absence of other diagnosed cardiopulmonary disease. Patients with these comorbidities have much higher rates of complications and should undergo further evaluations before having surgery.

There's also evidence to support delaying surgery in morbidly obese patients undergoing bariatric surgery. Roughly half of severely obese patients (those with BMIs of 40 or higher) have OSA, and 10% to 20% of those have obesity hypoventilation syndrome. Morbidly obese patients are also more susceptible to thromboembolic, infectious and surgical complications, and OSA increases those risks.

• Screen high-risk patients. Identifying high-risk patients for precautions and interventions can be burdensome, but a growing consensus believes that attempting to do so may reduce complications. For example, evidence supports avoiding general anesthesia in OSA patients undergoing specific procedures, such as joint arthroplasty. Additionally, since OSA can affect respiratory outcomes and promote post-operative cardiovascular events, it may be wise to consider monitoring both cardiac and respiratory function for OSA patients who have pulmonary hypertension and/or heart disease, both of which are common comorbidities.

Excessive daytime sleepiness and habitual snoring are classic symptoms of undiagnosed OSA patients, but numerous factors also increase the risk, including alcohol; smoking; obesity; increased neck circumference; male sex; advanced age; enlarged tonsils, adenoids and tongues; nasal obstruction; and craniofacial abnormalities.

• Recognize screening's limitations. Sleep testing, such as an overnight polysomnography, is the only completely accurate way to diagnose OSA, but because many patients are screened on the day of surgery, or only a day or 2 before, you'll likely have to rely on questionnaires or simple clinical models, which aren't 100% accurate.

Among current screening tools, STOP-Bang (osmag.net/fgtkk8) is the most validated in surgical patients (a score of 4 has a high sensitivity of 88% for identifying patients with severe OSA), and it has also been validated in sleep clinic patients and the general population. It's not perfect, but it adds clinical value to the pre-operative assessment and is a relatively easy way to determine risk. Other screening tools have varying degrees of accuracy across different patient populations.

Pre-operative testing of serum bicarbonate level may improve screening accuracy, and other parameters, such as oxygen desaturation index or cumulative duration of oxygen desaturation below 90%, may also improve predictions.

• Have CPAP equipment available. If patients don't bring in their own CPAP equipment on the day of surgery, consider having equipment for perioperative use available.

For patients who've previously been diagnosed with OSA, 2 recent large studies suggest that CPAP therapy is highly beneficial. In one, OSA patients given a prescription for CPAP before surgery had significantly reduced risk of cardiovascular adverse events, compared with patients with undiagnosed OSA. The second found that untreated OSA patients had significantly greater cardiopulmonary complication rates than those with prescribed PAP therapy. Untreated OSA patients also had significantly greater myocardial infarction rates and significantly more unplanned reintubations.

CPAP-adherent patients should continue to wear their devices at appropriate times both pre-operatively and post-operatively, as acute withdrawal of such therapy has been shown to result in recurrence of OSA and OSA-related symptoms within 1 to 3 days and physiologic derangements within 2 weeks.

Patients using alternative therapies for OSA should also be encouraged to continue using their therapy in the perioperative setting.

• Exercise caution with non-compliant OSA patients. For patients who've been diagnosed with OSA but who are non-adherent or poorly adherent to positive airway pressure therapy, pre-operative cardiopulmonary evaluation is recommended and, as noted previously, so is delaying surgery in the presence of hypoventilation or pulmonary hypertension, or resting hypoxemia in the absence of other known cardiopulmonary disease.
• Educate untreated and suspected OSA patients. Although it's clear that OSA can negatively influence outcomes, many procedures are low-risk, and, in part because screening tools aren't completely accurate, ultimately only a small percentage of patients identified as high risk have increased perioperative complications.

For patients with untreated or suspected OSA, discuss the risks and benefits of surgery, and consider the multiple relevant factors, such as comorbidities, the urgency and nature of the surgery, the anticipated need for high-dose opioids, and the availability of post-operative monitoring for opioid-related adverse events.

• Advise high-risk patients to consider diagnosis and treatment. Finally, advise patients identified as high risk to tell their primary care physicians, so they can be further evaluated. OSA is associated with numerous poor outcomes, including risk of death, cardiovascular events and average number of days hospitalized, and treatment appears to improve these outcomes. It's important to have a clear diagnosis for patients with OSA to have ongoing, long-term management. OSM

PREVALENT PROBLEM
Fast Facts About Sleep Apnea

DO THEY EVEN KNOW? Around 43% of men and 27% of women between ages 50 and 70 have obstructive sleep apnea.

• Just how prevalent is the problem? It's estimated that 43% of men and 27% of women between ages 50 and 70 have obstructive sleep apnea (OSA), as do 26% of men and 9% of women between 30 and 49.
• OSA is more common in patients who present for surgery.
• It's estimated that up to 90% of individuals with moderate to severe OSA remain undiagnosed. Not only don't they know they have it, but they also lack sufficient time before surgery to undergo formal diagnostic sleep testing.
• OSA patients have a 2 to 3 times higher risk of cardio-pulmonary complications than patients who have no sleep apnea.

— Jim Burger