the effects of adding ketamine to morphine in patient-controlled intravenous analgesia after orthopedic surgeries

background and aims: a routine method to control post-operative pain is patient-controlled intravenous analgesia (pcia) using opioids. regarding complications of opioids, it seems necessary to reduce their dosage and to improve the quality of analgesia using  adjuvants. we aimed  to assess the effect of adding ketamine to morphine in pcia pumps for post-operative pain control in orthopedic patients.   materials and method:                                                                                                                                                             sixty patients, being 20-60 years old (asa class i-ii) and undergoing orthopedic surgery in lower extremity, were enrolled  they had no history of opioid addiction or epilepsy. our patients were randomly allocated to three groups  20 mg morphine sulfate, 100 mg ketamine plus 20 mg morphine and  200 mg ketamine plus 10 mg morphine in their pcia pump. the pain score was evaluated using vas (0-10) and vrs (0-5) besides the sedation score and the degree of nausea-vomiting were assessed with ramsay scale (0-5) and n&v; score (1-4), respectively. all these measurements were performed 2, 4, 12, 24, and 48 hours postoperatively. findings: the incidence of  adverse drug reactions was not different among the three groups (p>0.05), but pain control was significantly better in the second and third group (ketamine plus morphine) in comparison with the first one (p<0.05). there was no difference in the quality of pain control between the second and the third groups. also, the need for additional opioid was significantly reduced in the two latter groups compared with the first one (p<0.05). conclusion: adding ketamine to morphine in pcia pumps would result in better pain control and less need for additional break-through analgesic.