Sleep apnoea ups delirium risk after surgery

An anecdotal observation of a possible link between sleep apnoea and post-surgical delirium has been measured and confirmed by a team of researchers at the Duke University Medical Center.

"The association between sleep apnoea and postoperative delirium is big news because it may offer us a way to control postoperative delirium which can be devastating," said senior author Madan Kwatra, Ph.D., who is associate professor of anesthesiology at Duke.

The study appears in Anesthesiology.

Delirium is not a minor consequence. The condition involves an acute and fluctuating consciousness and ability to understand, and is associated with health problems and higher risk of death right after surgery. Delirium is a strong predictor of mortality even 10 years after surgery.

There is hope for prevention, Kwatra said. "If the association between pre-existing sleep apnoea and postoperative delirium discovered in this study is confirmed by a larger study, we may be able to prevent postoperative delirium by treating sleep apnoea before and immediately after surgery."

What causes delirium after surgery?

The prospective study investigated patients who were having a total knee replacement, a routine procedure for older patients that restores function and reduces pain.

Out of 106 patients in the study, 27 developed delirium after surgery. Eight out of the 15 patients in the study who had been diagnosed with obstructive sleep apnoea experienced post-operative delirium, or 53%. By comparison, 20% of the patients without apnoea (19 out of 91) experienced delirium.

In the analysis, apnoea was the only statistically significant factor that predicted delirium out of many medical conditions that were analysed. The study provides early evidence that doctors might do better presurgical screening for sleep apnoea and introduce effective therapy for obstructive sleep apnoea as a way to reduce the risk of delirium, Kwatra said.

The causes of postsurgical delirium are still unknown, but lack of oxygen before or after surgery or possibly immune factors that lead to inflammation may play a role, he said.

The study findings support recent recommendations to screen for and treat obstructive sleep apnoea in an effort to reduce respiratory and cardiovascular problems associated with obstructive sleep apnoea.

(EurekAlert, March 2012) 

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