Trans-auricular vagus nerve stimulation to reduce perioperative pain and morbidity: protocol for a single-blind analyser-masked randomised controlled trial.

Background: Established or acquired loss of parasympathetic vagal tone is associated with complications, including pain, after noncardiac surgery. We describe a study protocol designed to test the hypothesis that transcutaneous auricular nerve stimulation may preserve efferent parasympathetic activity to reduce pain and morbidity after noncardiac surgery.

Methods: Participants aged >18 yr scheduled for urgent/elective orthopaedic surgery (=86) will be randomly allocated to bilateral transcutaneous auricular nerve stimulation or sham protocol for 50 min at the same time of day, before and 24 h after surgery.