Effect of an Hypnotherapy Session on the NOL Variations After Stimulation

Study Design: Prospective randomized double-blind, mono-centric trial (patient does not know if the conversation is hypnotic or not, the anesthesiologist in charge during the case is not here during the preoperative conversation and is not the one doing the medical conversational hypnosis or standard conversation).

This study proposes to answer two questions :

• To measure the difference in the variation of the NOL index (delta NOL) after standardized electrical stimulation performed after tracheal intubation under general anesthesia between two types of anesthetic induction : pharmacological induction associated with a brief session of medical hypnosis versus a standard pharmacological induction.
• To measure variation of heart rate, arterial pressure, BISpectral index after intubation, standardized electrical stimulation, incision and other intraoperative surgical stimuli. Evaluation of postoperative pain, analgesic consumption in the recovery room, and recovery room discharge time. 50 Adults scheduled for elective laparoscopic surgery under general anesthesia expected to last less than 3 hours will be enrolled.

Patients will be informed and included the day before surgery. Randomization will be done by web-base-systeme-algorithm dividing patients into two groups: general anesthesia alone or general anesthesia coupled with hypnosis. No premedication will be administered.

The hypnotherapist will meet briefly with the patient before admission to the operating room to introduce himself.

When the patient enters the operating room, a checklist is performed by the staff, the usual monitoring is set up (electrocardiogram, pulse oximeter, non-invasive blood pressure, muscle relaxation monitor, bispectral index, NOL index). Nasoparyngeal temperature and monitoring of expired carbon dioxide will be placed following tracheal intubation to allow monitoring of normothermia and normo capnia intraoperatively.

The PMD200TM monitor and the BIS index will be connected to the patient. Registration of the index NOL will be done continuously via the PMD200TM monitor, which will be switched on at the start of the procedures.

When everything is ready for pharmacological induction the anesthesiologist in charge will leave the operating room.

In the control arm the therapist will have a standard discussion to check all things are all right with the patient before pharmacological induction starts. No hypnotic conversation will be proposed.

In the hypnosis arm a short session of hypnosis will be done before the pharmacological induction.

The period of discussion in both the groups will be between 6 and 15 minutes, hypnotic or not.

Then, the anesthesiologist will be called for pharmacological induction of general anesthesia.

The protocol of anesthesia will be the same in both groups : the induction will be done by propofol (with a goal of Bispectral index : 40-60) and Remifentanil (with goal of NOL < 25), and muscle relaxation with Rocuronium (0.8 mg.kg-1).

After tracheal intubation, the remifentanil will be discontinued. After a period of at least 10 minutes after remifentanil discontinuation, a standardized tetanic stimulation (70mA, 100Hz, 30 seconds at the ulnar level) will be applied and all the anesthesia parameters and NOL index will be electronically recorded every 5 seconds.

After this stimulation, general anesthesia will be maintained as follows: sevoflurane inhaled anesthesia for a bispectral index between 40-60; remifentanil analgesia for a NOL index between 5-25; rocuronium for a muscle relaxation with TOF index between 1-3. Total consumption of remifentanil during the case will be monitored and calculated in mcg.kg-1 per hour of surgery as it will be a surrogate of intraoperative pain/nociception that will be analyzed too. At the end of surgery, anesthesia is discontinued, hydromorphone 7mcg.kg-1 will be administered at the end of skin closure in anticipation of postoperative pain. Acetaminophen will also be given PR at the end of surgery as well as intravenous ketorolac. Skin incisions for laparoscopic surgery will be infiltrated with 0.5% bupivacaine (maximum 20mL). Once the patient extubated, she/he will be transferred to post anesthesia care unit (PACU) where classical pain management will be offered. Pain scores in PACU, patients' satisfaction, opioid consumption will be evaluated between the two groups in PACU.

Data analysis: The main outcome analyzed will be the delta NOL or the variation of the NOL index between pre and post stimulation in the two groups. The mean maximum value of the NOL index after stimulation will also be compared between the two groups.

Statistical analyses will be performed using SAS version 9.4 or higher and will be performed at a bilateral significance level of 0.05, unless otherwise specified. Descriptive statistics of central tendency (e.g., mean and 95% CI, median) and dispersion (SD, frequency table) will be used to describe the characteristics of the patients in each group of the study. The intraoperative data collected in the groups will be compared using parametric (e.g. Student's t-test) or non-parametric (e.g. Mann-Withney's U-test, Chi-square test) tests depending on the type of variables and their distribution.