Sleep studies essential before bariatric surgery

By Sally Robertson, B.Sc.Jul 10 2012

Obstructive sleep apnea (OAS) frequently goes undiagnosed in obese patients who undergo bariatric surgery (BS), show findings from a US study.

Such patients should undergo a preoperative sleep test (polysomnography) to check for the condition, advise the researchers.

As reported in European Archives of Oto-Rhino-Laryngology, almost 70% of the study population was diagnosed with OAS after being watched sleeping during the night before their operations were due.

However, only a small proportion of these individuals had actually been diagnosed with the condition before being placed on a surgery waiting list, report Madeline Ravesloot (St Lucas Andreas Hospital, Amsterdam, the Netherlands) and team.

"Patients with OSA are particularly vulnerable during anesthesia and sedation and are at an increased risk of developing respiratory and cardiopulmonary complications postoperatively," explain Ravesloot et al. More often than in the general population, these patients sleep/live alone, meaning they are often unaware of their breathing abnormalities.

To assess the prevalence and severity of OAS among the patients (n=279), the team calculated the individuals' apnea hypopnea index, (the sum of apneas and hypopneas occurring per hour of sleep), during a preoperative overnight assessment by polysomnography. All of the patients had a body mass index (BMI) greater than 35 kg/m² and associated comorbidity.

Ravesloot et al report that 195 (69.9%) of the individuals were found to meet the criteria for OAS, with 78 (40.4%) of those meeting the criteria for severe OAS.

However, a mere 37 (13.3%) of these individuals had previously been diagnosed with the condition.

"The finding of OSA has important perioperative implications," remarks the team. "All patients with OSA have been shown to have increased perioperative risk and specific perioperative measures have to be taken."

Further analysis of the predictive effects of three clinical parameters (BMI, neck circumference, and the Epworth Sleepiness Scale), showed that none had cutoff values that were sensitive or specific enough for predicting the presence of OSA.

The team concludes that polysomnography is an "essential component of the preoperative workup of patients undergoing BS."

Sally Robertson

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