British journal of anaesthesia
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In experimental trials, ketamine has been shown to reduce hyperalgesia, prevent opioid tolerance, and lower morphine consumption. Clinical trials have found contradictory results. We performed a review of randomized, double-blinded clinical trials of ketamine added to opioid in i.v. patient-controlled analgesia (PCA) for postoperative pain in order to clarify this controversy. ⋯ The benefit of adding ketamine to morphine in i.v. PCA for orthopaedic or abdominal surgery remains unclear. Owing to huge heterogeneity of studies and small sample sizes, larger double-blinded randomized studies showing greater degree of homogeneity are required to confirm these findings.