Peroperative ketamine and morphine for postoperative pain control after lumbar disk surgery.

BACKGROUND: Ketamine, a N-methyl-D-aspartate receptor antagonist, may reduce postoperative opioid demand and improve postoperative analgesia.

METHODS: Sixty-nine patients scheduled for lumbar disk surgery under general anaesthesia were enrolled in a randomised, double-blind study comparing three analgesic combinations that were started before surgical incision: morphine 0.1 mg kg(-1) alone (group M; n=23); ketamine 0.15 mg kg(-1) alone (group K; n=22); and a combination of morphine 0.1 mg kg(-1) with ketamine 0.15 mg kg(-1) (group KM; n=23). Postoperatively patient-controlled analgesia was provided with intravenous morphine. Morphine consumption was assessed during 24 H, and pain scores were measured using a visual analogue scale (VAS) at rest and on mobilisation, during the first two postoperative days.

RESULTS: In group KM, less i.v. morphine was administered in the post anaesthesia care unit than in group M (median [range]: 0mg [0-2] vs. 7 mg [6-9], P=0.009). Cumulative 24 H morphine consumption was reduced by 57% in group KM vs. group M, and by 48% in group KM vs. group K. Postoperative VAS scores were lower in group KM vs. groups K and M. Maximal VAS score on mobilization was reduced in group KM compared to groups K and M (38 mm [35-45] vs. 52 mm [48-59] and vs. 59 mm [55-64], in groups KM, K and M, respectively, P=0.05 and P=0.002). The incidence of postoperative nausea and vomiting was decreased in group KM compared to group M (21.7% vs. 43.5%, P=0.001).

CONCLUSION: Ketamine small-dose, combined with morphine improves postoperative analgesia and reduces opioid-related side effects in lumbar disk surgery.