Ear Vagus Nerve Stimulation Linked to Less Inflammation After Surgery

This is a randomised controlled trial, the strongest design for testing a treatment. Researchers at a tertiary care academic surgical center enrolled 90 adults aged 18 to 70 who were having planned major abdominal or heart and chest surgery. The trial ran over 16 months. Patients were assigned by computer, 45 to active stimulation and 45 to a sham group. The sham group had the same electrodes and device connection, but no electrical current. Patients and outcome assessors were blinded.

Surgery always triggers inflammation. Some is needed for healing. Too much is tied to problems such as delayed wound healing, serious systemic inflammation and longer stays in intensive care. The authors note that the usual tools, corticosteroids and anti-inflammatory painkillers, carry risks of their own, including weakened immunity, impaired wound healing, stomach problems and kidney problems.

The study tests a different route. The vagus nerve links the brain with the body's organs and helps regulate immune activity. The authors describe a circuit, called the cholinergic anti-inflammatory pathway, in which signals along this nerve calm immune cells and dampen the production of inflammatory proteins. One branch of the vagus nerve reaches the outer ear, so it can be stimulated from the skin without an implanted device.

Patients in the active group received the stimulation through electrodes on the left ear. It began 90 minutes before the incision, continued through the operation, and was repeated for 30 minutes every six hours for the first 72 hours afterward.

Blood tests showed a clear difference. At 24 hours after surgery, both groups had raised inflammatory markers, but the stimulation group's rise was smaller. Interleukin-6 (IL-6) was 22.4 pg/mL against 38.6 in the sham group. Tumour necrosis factor-alpha (TNF-α) was 18.6 against 31.4. C-reactive protein (CRP) was 48.4 mg/L against 74.8. IL-10, a protein that restrains inflammation, was higher: 32.4 against 18.2. Activity of NF-κB, a switch that turns on inflammatory genes, was also lower in the stimulation group.

Recovery measures followed the same pattern. First oral intake came at 14.2 hours against 22.8 hours. First walking came at 18.4 hours against 28.6. Hospital stay averaged 4.8 days against 7.4. Pain scores and total painkiller use were lower, and return to normal daily activity came sooner. All of these differences had p-values below 0.001.

Complications were also less common in the stimulation group. Wound infection occurred in 4.4% against 13.3%. Ileus, a temporary halt in bowel movement, occurred in 6.7% against 17.8%. Pulmonary complications occurred in 2.2% against 8.9%. Readmission within 30 days was 4.4% against 11.1%. These p-values were between 0.038 and 0.049, close to the usual cutoff of 0.05. With only 90 patients, such differences in rare events could shift in a larger trial.

Heart rate variability, a measure of how well the autonomic nervous system is working, was also higher at 24 hours in the stimulation group. The authors read this as better autonomic recovery.

For people thinking about surgery later in life, the question is whether the body's own anti-inflammatory circuit can be switched on to smooth recovery without the side effects of drugs. The study did not test older patients specifically. It included adults up to age 70 and excluded people with certain heart rhythm problems, implanted cardiac devices, autoimmune disease or steroid treatment. It does not show how the approach would work in frail or very old patients. The study describes the method as safe, but the findings come from a single centre, and the paper's own background notes that robust randomised evidence has been limited.

The authors conclude that the findings support ear stimulation as a safe, noninvasive way to suppress post-operative inflammation and speed recovery. That is a promising result, not proof. It needs confirmation in larger, multi-centre trials, ideally including older patients, before anyone can say it should become routine care.

What to watch next

Replication in larger trials across more hospitals and age groups, with attention to complication rates.

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