Abstract
Background: There have been many attempts to alleviate pain after surgery, but there is no common approach to the control of postoperative pain. The use of epidural opioids, with local anesthetics, has been a widely employed formula to date. Ketamine, an N-methyl-d-aspartate receptor antagonist, has an excellent analgesic effect. Although there have been many reports on the dose and route of administrating analgesics, there have been few concerning the continuous epidural infusion of ketamine with fentanyl. We designed this study to find the effects of ketamine compared to those of epidurally injected bupivacaine and fentanyl, and used this trial to study any potential side effects. Methods: In a double blind trial, 55 patients received either fentanyl, $0.3{\mu}g/kg/h$ (Group F), or fentanyl, $0.3{\mu}g/kg/h$, and ketamine, 0.1 mg/kg/h (Group FK), added to 0.125% bupivacaine, at rates as high as 2 ml/h, for patient controlled epidural analgesia (PCEA) following a transabdominal hysterectomy. Ten minutes before the operation, patients received 10 ml of 0.125% bupivacaine, with either 0.5 mg/kg ketamine or the same amount of normal saline with $50{\mu}g$ fentanyl added. The pain scores and the side effects were recorded at 1, 3, 6 and 24 hour post operation. Results: There were no differences in the pain scores or side effects between the two groups. Conclusions: We failed to find any effect of the addition of epidural ketamine compared to the that of the bupivacaine and fentanyl formula. However, it is suggested that further investigations will be required on the dose and route of administration.