Preoperative small-dose ketamine has no preemptive analgesic effect in patients undergoing total mastectomy

We evaluated the preemptive analgesic effect of a small dose of ketamine gi ven before or immediately after surgery in a randomized, double-blinded stu dy performed in 128 women undergoing total mastectomy. Group 1 patients rec eived ketamine 0.15 mg/kg as a 5-mL IV injection 5 min before surgery and i sotonic saline 5 mt IV at the time of skin closure. Group 2 received 5 mt I V of isotonic saline, then 0.15 mg/kg IV ketamine. A standard general anest hesia procedure including sufentanil was used. In the recovery room, patien t-controlled analgesia IV morphine was used for postoperative analgesia. Po stoperative pain was assessed by measuring morphine consumption and visual analog scale pain scores. No significant intergroup differences were seen i n the pain scores. Patient-controlled analgesia morphine consumption was lo wer during the first 2 h after surgery in patients given ketamine at the ti me of skin closure. No patient complained of hallucinations or nightmares. The incidence of adverse effects was not different between the two groups. In conclusion, administering ketamine at the end of surgery is more effecti ve in reducing morphine consumption than it is when given before surgery. I mplications: We administered the same small dose of ketamine before or afte r surgery. The preoperative administration of 0.15 mg/kg ketamine in patien ts undergoing total mastectomy did not elicit a preemptive analgesic effect . Ketamine given at closure reduced the patient-controlled analgesia morphi ne requirement in the first 2 h after surgery.