Evaluation of the Stress Response in Bariatric Surgery With and Without the Use of Opioids

"* 40 mg/kg magnesium sulfate in 100 ml N/S infusion~* 0.4 mcg/kg dexmedetomidine, max total dose 50mcg in 50 ml N/S infusion~* 0.3 mg/kg ketamine in 10 ml volume~* 0.2 ml/kg of the Multimix regimen in 100 ml N/S infusion as a bolus (The Multimix regimen consists of 50mcg dexmedetomidine, 500 mg lidocaine and 50mg ketamine).~* 0.2 ml/kg/h of the Multimix regimen in 100 ml N/S infusion as a continuous infusion. Except for standard analgesic strategies, both groups will receive fentanyl as a rescue dose (1mcg/kg) based on a nociceptive level value \> 25 or elevation of Heart Rate and/or Blood Pressure \>20%.~Placebo infusions of normal saline will be prepared to enable blinding."

"* 2 mcg/kg fentanyl in 10 ml volume~* 0.2 mL/kg/h remifentanil infusion~* 0.1 mg/kg morphine. Except for standard analgesic strategies, both groups will receive fentanyl as a rescue dose (1mcg/kg) based on a nociceptive level value \> 25 or elevation of Heart Rate and/or Blood Pressure \>20%.~Placebo infusions of normal saline will be prepared to enable blinding."