A Comparison of Opioid-Free Anesthesia (OFA) and Standard Fentanyl-based General Anesthesia in Patients with Morbid Obesity Undergoing Laparoscopic Bariatric Surgery

Adult patients (over 18 years old) with a BMI ≥ 40, ASA ≤ II, qualified for elective bariatric surgery under general anesthesia with endotracheal intubation, who provided informed, voluntary consent to participate in the study, were included. Patients with BMI < 40, ASA III and above, heart failure, arrhythmias (especially bradyarrhythmia), hypovolemia, shock, unstable coronary artery disease, autonomic neuropathy with orthostatic hypotension, with a history of allergic reactions, pregnancy, indications for urgent surgical intervention, or those who did not consent to participate in the study, were excluded. Patients' weight, height, and BMI were measured. All obtained data were anonymized.

After transporting the patient to the operating room, the envelope was opened, and the patient was assigned to either the OFA or FNT anesthesia group.

Patients in the OFA group were anesthetized as follows: before induction: ketamine 0.15 mg/kg (corrected body weight), lidocaine 1-1.5 mg/kg (corrected body weight) slow infusion, magnesium sulfate 30-50 mg/kg (corrected body weight), dexamethasone 8 mg, paracetamol 2.0g. Induction: after three minutes of preoxygenation with 100% oxygen, propofol 2.5 mg/kg (actual body weight) was administered. Following confirmation of mask ventilation, rocuronium bromide 0.6 mg/kg (actual body weight) was given. Bag-mask ventilation with 100% oxygen continued for 3 minutes. After achieving full neuromuscular blockade, confirmed by the loss of all four responses using a peripheral nerve stimulator, the patient was intubated and connected to the anesthesia machine and ventilated with 1-1.5 MAC sevoflurane. Maintenance: ketamine 0.125-0.25 mg/kg/h (corrected body weight), lidocaine 1.5-3 mg/kg/h (corrected body weight), magnesium sulfate 10 mg/kg/min (corrected body weight), and rocuronium bromide 1.25 µg/kg/min (corrected body weight) were used. After surgery, neuromuscular blockade was reversed with sugammadex at 2-4 mg/kg (corrected body weight). The patients were also administered ephedrine in case of hypotension, atropine for bradycardia, and beta-blockers for tachycardia and hypertension.

Patients in the FNT group were anesthetized as follows: before induction: fentanyl 1.5-3 µg/kg (corrected body weight) iv, preoxygenation with 100% oxygen for 3 minutes, propofol 2.5 mg/kg (actual body weight) and following confirmation of mask ventilation, rocuronium bromide 0.6 mg/kg (actual body weight) bolus. Bag-mask ventilation with 100% oxygen and 2% inhaled sevoflurane continued for 3 minutes. After achieving full neuromuscular blockade, the patient was intubated and connected to the anesthesia machine and ventilated with 1-1.5 MAC desflurane. Maintenance dose for fentanyl was 0.003-0.006 µg/kg/min (corrected body weight) and rocuronium bromide 1.25 µg/kg/min (corrected body weight) were used. After surgery, neuromuscular blockade was reversed with sugammadex at 2-4 mg/kg (corrected body weight).

During induction, patients were positioned supine with the head and torso elevated at a 25-degree angle on a positioning pad. Anesthetic monitoring included HR, NIPC-SYS, NIPC-MEAN, NIPC-DIA, SpO2, esCCO, esCCI, and esSVI using the Vismo monitor and EtCO2.