The use of ketamine as rescue analgesia in the recovery room following morphine administration--a double-blind randomised controlled trial in postoperative patients

Abstract

In some patients, control of postoperative pain can be difficult with morphine alone. This double-blind randomised controlled trial was designed to evaluate whether a small bolus dose of ketamine could improve pain scores in those patients who had inadequate relief of their postoperative pain after two standard doses of morphine. Forty-one patients with uncontrolled postoperative pain were randomly assigned to receive either morphine (M) alone, or morphine plus 0.25 mg/kg ketamine (K) in the recovery room. No other analgesics were to be given. The study had adequate power to detect a 25% difference in pain scores. There was no statistically significant difference in verbal rating scale pain scores between the two groups either in the recovery room (K = 5.16, M = 6.28, P = 0.065), or at a later time on the ward. There was no apparent difference between groups in sedation, morphine consumption, postoperative nausea and vomiting, quality of recovery or need for rescue analgesia. We could not demonstrate an effective role for ketamine in the management of problematic postoperative pain at the dose studied.