Identifying and managing unrecognized obstructive sleep apnea (OSA) before surgery can improve postoperative airway function, according to the results of a new study. Auto-titrated continuous positive airway pressure (APAP) treatment decreased postoperative apnea hypopnea index (AHI) and improved oxygenation in patients who had moderate or severe OSA in a randomized open-label trial.
“In the general population, 80% to 90% of sleep apnea is not diagnosed. Patients with undiagnosed or unrecognized OSA may have an increased risk of respiratory depression from opioids for postoperative pain treatment,” lead author Frances Chung MBBS FRCPC, Professor, Department of Anesthesiology, University of Toronto Medical Director, Ambulatory Surgical Unit and Combined Surgical Unit Toronto Western Hospital, University Health Network, told ConsultantLive.
“Sometimes there is not a lot of time between the visit of preoperative clinic and the scheduled surgery,” Dr Chung said. “Patients who are suspected to have sleep apnea are referred to a sleep physician and may undergo a sleep study. If the sleep study is positive, they then have to go to the sleep laboratory again for a second night of CPAP titration. APAP does not require CPAP titration in a sleep laboratory since it automatically senses the obstruction of the airway to give an appropriate CPAP for the obstruction. In a way, it is a newer type of CPAP.”
Chung and colleagues examined 177 patients with an AHI of more than 15 events per hour; 87 patients received APAP for 2 or 3 nights before surgery and 5 nights after surgery, and 90 patients received routine care. One hundred patients completed the study. Patients who received APAP did so for 2.4 to 4.6 hours per night.
Postoperatively, patients who received APAP did better. Those who received APAP had a median AHI of 3 events per hour on the third postoperative night compared with a median of 32 events per hour for the control group. There was no significant change in the central apnea index.
“The data of APAP can be downloaded very easily and can give the results of abolition of apnea and hypopnea and improvement of oxygen saturation,” said Dr Chung. “This will be great positive feedback to the patient.”
“Most patients do not understand that sleep apnea causes repeated intermittent hypoxia during the night,” Dr Chung added. “This causes endothelial dysfunction and increased inflammation to the body. Sleep apnea has been shown to be associated with hypertension, heart disease, diabetes, and renal diseases. Using APAP or CPAP can abolish the repeated obstruction of airway during the night.”
The Toronto researchers have devised a validated screening tool for OSA, STOPBang. “Primary care physicians can use STOPBang questions to screen patients for sleep apnea,” Dr Chung noted. “A patient with a score of 0 to 2 is unlikely to have sleep apnea. If the score is 3 or 4, the risk is intermediate. If the score is 5 to 8, the risk is high.”
Dr Chung’s message to primary care physicians: “More recognition of these patients with sleep apnea is needed to avoid postoperative complications.”
The researchers reported their results in the October 2013 issue of the Journal of Anesthesiology.