Lack of a pre-emptive effect of low-dose ketamine on postoperative pain following oral surgery

The aim of this study was to assess the effect of pre- vs postincisional low-dose iv ketamine on postoperative pain in outpatients scheduled for oral surgery under general anesthesia.Eighty-four patients were randomly assigned to receive intravenously saline before and after surgery in Group 1, ketamine 300 microg x kg(-1) iv before and saline after surgery in Group 2, saline before and ketamine 300 microg x kg(-1) iv after surgery in Group 3. Postoperative analgesia consisted of iv proparacetamol and ketoprofen. Rescue analgesia consisted of nalbuphine 200 microg x kg(-1) iv. Analgesia at home consisted of oral ketoprofen, and acetaminophen with codeine as rescue analgesia. A telephone interview was conducted on the first and second postoperative days.There were no significant differences between groups with respect to pain scores, the number of patients requiring nalbuphine in the postanesthesia care unit (PACU), (36.7%, 38.7%, and 39.5% for Groups 1, 2, and 3 respectively), or nalbuphine consumption in the PACU (66.5 microg x kg(-1) +/- 16.8, 75.9 microg x kg(-1) +/- 17.5, 66.7 microg x kg(-1) +/- 21.6 for Groups 1, 2, and 3 respectively). The number of rescue analgesic tablets taken at home, and time to first request for rescue analgesia, sedation scores, or side-effects were similar amongst groups. No patient required nalbuphine in the ambulatory care unit.There was no benefit to pre-emptive administration of ketamine 300 microg x kg(-1) iv whether administered pre- or postoperatively.