Postoperative analgesia with i.v. patient-controlled morphine: effect of adding ketamine

We have studied the effect of adding ketamine to i.v. morphine patient-cont rolled analgesia (PCA) for the treatment of pain after laparotomy. Thirty p atients were allocated randomly to receive PCA with saline or ketamine in a double-blind, randomized study. Analgesia was started in the recovery room when visual analogue scale (VAS) scores were >4. A bolus dose of morphine 3 mg was given to all the patients followed by i.v. PCA. Simultaneously, an infusion of ketamine 2.5 mu g kg(-1) min(-1) or saline was started. Pain s cores, morphine consumption and side effects were noted for up to 48 h afte r the start of PCA. VAS scores decreased significantly with time (P = 0.000 1) and were similar (P = 0.3083) in both groups. Cumulative morphine consum ption at 48 h was significantly lower in the ketamine group (28 mg) than in the control group (54 mg) (P = 0.0003). Nausea was less frequent in the ke tamine group (P = 0.03).