Effects of Perioperative TEAS on Postoperative Pain and Agitation in Pediatric Adenoidectomy and Tonsillectomy

Sample size The sample size estimation was based on the incidence of agitation in previous studies. It was selected for a type I error of 0.05, a power of 0.80, and the dropout rate 0f 0.2. The calculation was done through a website program (https://www.medsci.cn), and 200 patients should be included .

Randomization and blinding On arrival at the operating room, a simple randomization method will be used to make sure that the patient is randomly allocated to one of four groups at the 1:1:1:1 ratio.Investigator put the group information in four different envelopes. When the first envelope is extracted, the following patients intelligently extract the group from the remaining envelopes, and so on, until all four envelopes are extracted, and investigator repeat the process. The anesthesiologist who carried out the TEAS procedures and in charge of intraoperative anesthesia is aware of the assignment to group TEAS. But the outcome assessors responsible for collecting and analyzing the data are blind to patient treatment.

Procedure Before entering the operating room, intravenous (IV) access should be clear and no medication is given previously. After entering the operating room, electrocardiogram (ECG), pulse oxygen inundation (SpO2), noninvasive blood pressure (NIBP), SedLine and analgesia nociception index(ANI) are checked according to the manufacturer's recommendations . At the same time, the electrodes are placed at Hegu (LI4), Neiguan （PC 6）and Zusanli (ST36) of both sides.Anesthesia is induced with 2-3 mg/kg of propofol, 0.3 µg/kg of sufentanil. Meanwhile, 0.1 mg/kg of atropine and 0.2 mg/kg of dexamethasone are given to prevent postoperative nausea and oral secretions. After confirming the absence of a response to eye stimulus, 0.15 mg/kg of cis-atracurium is administered. Ventilation is conducted with a mask using 100% oxygen, and tracheal intubation is done after realizing the adequate depth of anesthesia. Next, to preserve the spectral edge frequency (SEF) between 14 and 20, anesthesia is maintained with the end-tidal concentration of sevoflurane 2-2.5 vol% and remifentanil at a dose of 0.2-0.3ug/kg/min during surgery, while ventilation is measured to sustain the end-tidal carbon dioxide (EtCO2) between 40 ± 5 mmHg. Furthermore, baseline hemodynamic variations are kept within a ±20% range.

Intervention patients are randomly divided into TEAS and control groups, and TEAS group is divided into three subgroups (S1, S2 and S3) according to the time of treatment started: S1 treatment initiate at 30 minutes before induction and last for 30min, S2 treatment initiate immediately after induction and stop at the end of surgery, S3 treatment initiate immediately after extubating and last for 30 minutes. The TEAS group receive TEAS treatment(disperse-dense waves; frequency, 2/100 Hz)on acupoints Hegu(LI4) , Neiguan(PC6) and Zusanli（ST 36）of both sides, and the present intensity(8～12 mA) is the maximum current that could be tolerated. Then, the TEAS treatment is administered twice a day (once in the morning and once in the afternoon) on the first and second postoperative day, which last for 30 minutes each time. And the control group is given all manipulations without electrical stimulation.

Statistical analyses Measurement data of normal distribution are reported as the mean ± SD. Categorical variables are analyzed through chi-squared test or the Fisher's exact probability test and presented as numbers (%). Comparisons between two groups are performed with Student's t-test. Repeated measurements were compared using repeated measure' ANOVA. For all tests, P<0.05 is considered statistically significant.