Wearing noise-cancelling ear defenders during surgery significantly reduces the likelihood of nausea and vomiting afterward, according to a randomized trial presented at the Anesthesiology conference in San Diego. The findings offer a simple, non-pharmacological way to ease one of the most common and unpleasant side effects of anesthesia.
The study, led by Huayue Liu of the First Affiliated Hospital of Soochow University in Suzhou, China, enrolled 192 patients who underwent keyhole gynecological surgery under general anesthesia. Half were randomly assigned to wear noise-blocking ear defenders from the start of anesthesia until the end of the procedure, while the other half received standard care without hearing protection. All patients received standard anesthesia and anti-nausea medication.
Within 48 hours after surgery, 35 percent of patients who wore ear defenders experienced nausea or vomiting, compared with 52 percent of those who did not. The protective effect extended beyond incidence: symptoms were also less severe among patients whose hearing had been shielded, with less vomiting and a smaller impact on daily life.
Operating theaters are not quiet environments. Liu recorded average noise levels of 66 decibels during the study, roughly equivalent to a normal conversation. The relationship between sound, nausea, and anesthesia remains unclear, but noise is thought to trigger a stress response that activates the autonomic nervous system, which regulates involuntary functions such as heart rate and interacts with brainstem pathways involved in nausea and vomiting.
“That data is really encouraging and is actually in line with decades of research showing that anesthesia is not simply an off switch,” said Vigi Katlowitz of Baylor College of Medicine in Houston, who was not involved in the study. The results support the idea that the brain continues to process sounds even when a person is unconscious.
Liu cautioned that the researchers did not investigate the mechanism behind the effect, so the idea that ear defenders dampen a stress response “remains a hypothesis.” Still, he said the biological plausibility is that general anesthesia produces unconsciousness without necessarily eliminating all neural processing of sound. He hopes to conduct a larger, multi-site trial that measures noise exposure relative to nervous system activity in patients under general anesthesia.
Nausea and vomiting are common after surgery, and patients are routinely given drugs to prevent them. The new findings suggest that a low-cost intervention—simply blocking operating-room noise—could complement existing medications and improve recovery for surgical patients.
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