The goal of this clinical trial is to learn whether different frequencies of transauricular vagus nerve stimulation (tVNS) can reduce postoperative pain and opioid consumption in adults undergoing abdominal or urologic surgery. It will also evaluate the effects of tVNS on recovery quality, autonomic function, and treatment safety. The main questions it aims to answer are:
Does transauricular vagus nerve stimulation reduce postoperative opioid consumption during the first 24 hours after surgery? Do different stimulation frequencies (high-frequency and low-frequency tVNS) produce different effects on postoperative pain and autonomic responses? Is transauricular vagus nerve stimulation safe and well tolerated in surgical patients?
Researchers will compare high-frequency tVNS, low-frequency tVNS, and sham stimulation (inactive stimulation) to determine their effects on postoperative pain and opioid requirements.
Participants will:
Be randomly assigned to receive high-frequency tVNS, low-frequency tVNS, or sham stimulation.
Receive two 30-minute stimulation sessions, one before anesthesia and one after surgery in the post-anesthesia care unit.
Undergo assessments of postoperative pain, opioid consumption, need for rescue analgesics, postoperative nausea and vomiting, heart rate changes, and quality of recovery.
Be monitored for adverse events related to the intervention during the study period.
A total of 174 participants will be enrolled in this single-center, randomized, double-blind, sham-controlled clinical trial.
Adults aged 18 to 59 years.
Undergoing elective abdominal or urologic surgery.
American Society of Anesthesiologists (ASA) physical status I-III.
Able and willing to provide written informed consent.
History of neurological disorders.
History of psychiatric disorders.
Inability to understand study procedures.
Pregnancy.
Parallel
Transauricular Vagus Nerve Stimulation (tVNS)
DeviceNon-invasive electrical stimulation of the auricular branch of the vagus nerve applied bilaterally through ear electrodes. Stimulation is delivered before anesthesia and after surgery using predefined frequency settings.
Sham Transauricular Vagus Nerve Stimulation (sham tVNS)
DeviceSham stimulation delivered using the same device and electrode placement as active stimulation. The device is activated to mimic treatment but does not deliver therapeutic electrical stimulation.
Total postoperative opioid consumption during the first 24 hours after surgery
Total opioid consumption during the first 24 postoperative hours, recorded according to the institutional postoperative analgesia protocol.
Postoperative pain intensity (VAS)
Pain intensity measured using a 100-mm Visual Analog Scale (VAS). Pain scores will be assessed at predefined postoperative time points and compared among study groups.
Rescue analgesic use
Number of participants requiring rescue analgesics and total rescue analgesic administration during the first 24 postoperative hours.
Postoperative nausea and vomiting (PONV)
Incidence of postoperative nausea and/or vomiting and use of rescue antiemetic medication during the postoperative period.
Heart rate changes
Changes in heart rate measured immediately before and immediately after transauricular vagus nerve stimulation sessions as an indicator of autonomic nervous system activity.
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Federal University of Bahia
Lead sponsor
Faculdade de Medicina de Botucatu, UNESP, Botucatu, Brasil
Collaborator
