Effect of a low-dose ketamine regimen on pain, mood, cognitive function and memory after major gynaecological surgery

Abstract

Major gynaecological abdominal surgery is associated with moderate to severe postoperative pain, hyperalgesia and the need for multimodal analgesia to reduce high morphine consumption. A low-dose ketamine regimen appears to prevent postoperative hyperalgesia. We examined the potential beneficial effect of ketamine on postoperative pain management and cognitive function. Ninety patients were included in this double-blind, randomized, placebo-controlled study to test the efficacy and adverse effects of ketamine (as an intraoperative bolus of 0.15 mg kg-1, followed postoperatively by ketamine 0.5 mg per morphine 1 mg in a patient-controlled analgesia device). All patients received additionally ketoprofen. The main end-point was morphine consumption over the first 24 h. Secondary efficacy and safety end-points were morphine consumption during the titration period and during the patient-controlled analgesia period (48 h), the number of morphine-related adverse effects and the results of psychometric tests. Ketamine, in combination with morphine and ketoprofen, did not improve postoperative pain scales and did not reduce morphine consumption and the incidence of morphine-related adverse effects. Ketamine did not modify mood, cognitive and memory functioning. Adding a low dose of ketamine to an efficacious multimodal analgesic regimen did not improve analgesia after gynaecological surgery. Although this combination appears to be safe, the lack of benefit suggests that a low dose of ketamine should not be used for routine care.