Perioperative use of ketamine infusion versus dexmedetomidine infusion for analgesia in obese patients undergoing bariatric surgery: a double-blinded three-armed randomized controlled trial

BACKGROUND: Bariatric surgery depends on the development of novel anesthetic techniques to reduce the incidence of complications and improve postoperative outcomes. Ketamine and dexmedetomidine have been used for perioperative analgesia and we hypothesized that they would decrease postoperative morphine requirements. The objective of this trial is to study whether choice of ketamine or dexmedetomidine infusion would affect postoperative total morphine consumption. METHODS: Ninety patients were equally randomized into three groups. The ketamine group received a bolus dose (0.3 mg/kg) of ketamine over 10 min, followed by an infusion of the same drug (0.3 mg/kg/h). The dexmedetomidine group received a bolus dose (0.5 mcg/kg) of dexmedetomidine over 10 min, followed by an infusion of this drug (0.5 mg/kg/h). The control group received a saline infusion. All infusions were given till 10 min before the end of surgeries. Intraoperative fentanyl was given when patient developed hypertension and tachycardia despite adequate anesthesia and muscle relaxation. Postoperative pain was managed by a rescue dose of 4 mg of IV morphine, with a minimum interval of 6 h between morphine doses if the numerical rating scale (NRS) score was ≥ 4. The primary outcome was the total morphine dose, and the secondary outcomes were intraoperative fentanyl requirement, time to extubation, postoperative nausea and vomiting (PONV), NRS scores, and modified observer’s agitation/sedation scale (MOASS) scores. RESULTS: Compared with ketamine, dexmedetomidine decreased the need for fentanyl intraoperatively (160 ± 42 µg), shortened the time to extubation (3 ± 1 min), and improved MOASS and PONV scores. In turn, ketamine decreased postoperative NRS scores and the need for morphine (3 ± 3 mg). CONCLUSIONS: Dexmedetomidine treatment was associated with lower fentanyl doses, a shorter time to extubation, and better MOASS and PONV scores. Ketamine treatment was associated with significantly lower NRS scores and morphine doses. These results indicated that dexmedetomidine effectively decreased intraoperative fentanyl requirement and the time to extubation, while ketamine decreased the need for morphine. TRIAL REGISTRATION: This trail was registered on the clinicaltrials.gov registry (NCT04576975) on October 6, 2020. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12871-023-02059-3.