The perioperative combination of methadone and ketamine reduces post-operative opioid usage compared with methadone alone

Background A synergy between ketamine and methadone (ME) to produce antinociception has been demonstrated in experimental neuropathy. We wanted to compare post-operative opioid requirements in patients undergoing multilevel lumbar arthrodesis after the administration combined MEketamine (MK) or ME alone. Methods This was a randomised double-blind study. During sevofluraneremifentanil anaesthesia, 11 patients in each group received the following: ketamine bolus (0.5?mg/kg) after tracheal intubation, followed by an infusion of 2.5?mu g/kg/min in the MK or saline bolus plus infusion in the ME group. Post-operative analgesia during 48?h was provided by patient-controlled analgesia (PCA), delivering bolus containing the following: ME 0.25?mg plus ketamine 0.5?mg in the MK group or ME 0.5?mg in the ME group. Lockout was 10?min, maximum of 3 boluses/h in both groups. Before closing the wound, all the patients received intravenous (i.v.) ME 0.1?mg/kg, dexketoprophen and paracetamol. Pain intensity was evaluated by a numerical rating scale (NRS), on arrival at recovery room (RR) and 24 and 48?h after surgery. In the RR, i.v. ME was administered until NRS was 3 when PCA was started. Dexketoprophen and paracetamol were administered 48?h. Results Remifentanil requirements were higher in the MK group (P?=?0.004). Patients in the MK group received 70% less ME by PCA at 24?h (MK vs. ME group, median and interquartile range) 3.43?mg (1.96.5) vs. 15?mg (9.6517.38) (P <?0.001) and at 48?h 2?mg (0.53.63) vs. 9.5?mg (3.513.75) (P?=?0.001). Patients in the MK group also attempted less doses, at 24?h: 19.5 (12.7579.5) vs. 98 (41.5137) (P?=?0.043). Both groups had similar NRS values and comparable side effects. Conclusions Perioperative ketamineME combination significantly decreased opioid consumption by PCA.