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 Compared to patients without apnea, people with severe apnea were
more than twice as likely to die of heart complications or
experience serious cardiac events like heart attacks and strokes
within 30 days of surgery, researchers report in JAMA.
Previous research suggests that sleep irregularities can increase
the risks for a variety of cardiovascular disorders, such as clogged
or hardened arteries, high blood pressure, irregular heartbeat, and
stroke, as well as metabolic problems like high cholesterol, obesity
and diabetes that all contribute to cardiovascular disease.
For the current study, researchers did sleep studies for 1,218
patients before they had surgery for conditions unrelated to heart
disease. None of the patients had been previously diagnosed with
apnea - which occurs when breathing repeatedly stops and starts
during sleep - but two-thirds of them were found to have the
condition based on their sleep study results.
"In patients with severe obstructive sleep apnea, there are repeated
episodes of complete or partial airway obstruction during sleep,"
said lead study author Dr. Matthew Chan of the Chinese University of
Hong Kong.
"Patients having surgery are particularly vulnerable because the
surgery and anesthetics are likely to worsen airway obstruction,"
Chan said by email.
The type of anesthesia during the surgery didn't appear to influence
the risk of heart complications afterwards. Use of opioids and
oxygen therapy after surgery also didn't appear to impact the risk.
Slightly more than one in 10 patients in the study had severe apnea,
when breathing stopped and started more than 30 times a night.
About 19 percent of participants had moderate apnea, when breathing
stopped and started at least 15 times a night; 37 percent had mild
apnea with no more than no more than five episodes a night.
Like severe apnea, moderate and mild cases also appeared to increase
the risk of cardiac events after surgery. But with the exception of
severe apnea, the increased risk was too small to rule out the
possibility that it was due to chance.
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Patients with mild and moderate apnea were typically overweight, and
people with severe apnea tended to be obese.
The study wasn't a controlled experiment designed to prove whether
or how undiagnosed or untreated apnea might directly cause heart
problems after surgery.
One limitation of the study is the potential for differences in
postoperative care to influence the risk for heart complications,
the study authors note.
Even so, the results suggest that identifying patients with
undiagnosed apnea prior to surgery may help reduce their risk of
cardiac complications afterward, said Dr. Dennis Auckley of Case
Western Reserve University and MetroHealth Medical Center in
Cleveland, Ohio, who wrote an editorial that was published with the
study.
That's because the recurrent episodes of low oxygen levels that
happen with sleep apnea are associated with increased blood pressure
and heart rate and place significant stress on the cardiovascular
system, Auckley said by email.
"When this is happening every time an individual goes to sleep,
night after night, it increases their risk for long-term
cardiovascular complications (i.e. heart attacks, heart rhythm
problems, stroke)," Auckley added. "It may be that the increased
stress of the post-surgery environment, which can temporarily worsen
obstructive sleep apnea and the low oxygen level associated with it,
accelerates the development of these bad outcomes in someone at risk
for them (e.g. severe untreated obstructive sleep apnea)."
SOURCE: http://bit.ly/2JEhekV and http://bit.ly/2JLdJcm JAMA, online
May 14, 2019.
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