Perioperative small-dose S(+)-ketamine has no incremental beneficial effects on postoperative pain when standard-practice opioid infusions are used

Several studies report that when small-dose racemic ketamine, an N-methyl-D-aspartate receptor antagonist, is administered perioperatively, opioid consumption is reduced postoperatively. S(+)-ketamine has a higher affinity for the N-methyl-D-aspartate receptor and less-serious side effects than racemic ketamine. Thirty patients scheduled for elective arthroscopic anterior cruciate ligament repair were enrolled in this randomized, double-blinded clinical trial designed to determine the preemptive effect of S(+)-ketamine on postoperative analgesia requirements in a setting of clinically relevant perioperative analgesia. Total IV anesthesia was induced and maintained with remifentanil (0.125-1.0 mug.kg(-1).min(-1)) and a propofol target-controlled infusion (target 2-4 mug/mL). The Ketamine group received a bolus of 0.5 mg/kg S(+)-ketamine before incision, followed by a continuing infusion of 2 mug.kg(-1).min(-1) until 2 h after emergence from anesthesia. The Control group received NaCl in the same sequence. After IV morphine provided pain relief down to less than or equal to3 on a visual analog scale scored from 0 to 10, patients were connected to a patient-controlled analgesia device. There were no significant differences between the two groups in terms of total morphine consumption or VAS scores, either at rest or with movement. In our study, S(+)-ketamine did not contribute to postoperative pain reduction, possibly because of the clinically routine perioperative opioid analgesia.