Opioid-free Total Intravenous Anesthesia With Propofol, Dexmedetomidine and Lidocaine Infusions for Laparoscopic Cholecystectomy; Comparison With Propofol, Remifentanil Infusions

Patients are randomly allocated into two groups to have either opioid-free anesthesia (Group DL) with dexmedetomidine (0.6 mg/kg loading, 0.3 mg/kg/h infusion), lidocaine (1.5 mg/kg loading, 2 mg/kg/h infusion), and propofol infusions or opioid-based anesthesia (Group RF) with fentanyl, remifentanil (0.25μg/kg/min), and propofol infusions.

Simple randomization was done using 80 opaque sealed envelopes, 40 for each group, indicating group assignment and describing the anesthetic protocol. Before anesthesia induction, an anesthesiologist will open the next envelope in the sequence to reveal the treatment allocation. This anesthesiologist will only prepare the study medications and will be involved in neither preoperative and postoperative data collection nor anesthesia management of the patients.

The drugs will be delivered in 10 ml and 50 ml syringes labeled as "loading" or "infusion" respectively. To ensure proper blinding, the loading doses of drugs (dexmedetomidine and lidocaine in Group DL or fentanyl and normal saline in Group RF) will be calculated according to the patient's body weight and diluted to a 10 ml volume labeled as "loading-1" and "loading-2" in order of administration. The infusion drugs (dexmedetomidine and lidocaine in Group DL or remifentanil and normal saline in Group RF) will be prepared in 50 ml syringes and labeled as "infusion-1" and "infusion-2" respectively.

At the preoperative holding area, patients will be instructed in the use of the verbal numerical rating scale (VNRS) and patient controlled analgesia (PCA) pump. Same anesthesiologist (MB) who is blinded to the study groups will perform the anesthesia management of all procedures.

On arrival at the operating room, standard monitoring will be applied consisting of ECG, noninvasive blood pressure, pulse oximetry and bispectral index (BIS). After premedication with intravenous midazolam (0.03 mg/kg), baseline heart rate and mean arterial blood pressure (MAP) will be determined which are average of three consecutive measurements. Preoxygenation with 5 L/min of pure oxygen will be performed during administration of loading doses. Before induction, patients in Group DL received 0.6 μg/kg dexmedetomidine (loading-1) diluted to a total volume of 10 ml and infused in 10 minutes. To avoid bias, patients in Group RF will receive 2 μg/kg fentanyl in same fashion. At the induction, dexmedetomidine or remifentanil (1 μg/ml and 50 μg/ml respectively, infusion-1) infusions 0.3 ml/kg/h will be started and lidocaine 1.5 mg/kg (loading-2) in Group DL or normal saline in Group RF and propofol 1.5 mg/kg will be administered. Lidocaine (20 mg/ml) or normal saline infusions 0.1 ml/kg/h and propofol infusion 10 mg/kg/h will be started immediately after loading doses. Vecuronium 0.1 mg/kg i.v. will be given to facilitate tracheal intubation.