Objective of the study was to evaluate the influence of adding ketamine to PCA on analgesia, morphine consumption and adverse effects after major abdominal surgery. The results showed that the patient, anesthesia and surgery related characteristics were compared in 2 groups. VAS score at rest and on movement at 24 and 48 hours after surgery was not different between the 2 groups. Morphine consumption during 24h and 48h in group MK was significantly less than that in group M
36.6 + or - 6.2 mg versus 40.4 + or - 7.2 mg and 65.5 + or - 10.3 mg versus 71 + or - 8.9 mg, respectively (p 0.05). Rates of vomitting, nausea, priritus and Ramsay's sedation score 4 were not significantly different between two groups (p 0.05). In conclusion, addition of ketamine to morphine in PCA was effective as an analgesia and can decrease morphine consumption, but did not have a significant affect on the rates of PONV and priritus and the level of sedation.