Role of epidural ketamine for postoperative analgesia after upper abdominal surgery

Ketamine, a N-methyl-D-aspartate receptor antagonist inhibits central sensitization due to peripheral nociception thus potentiating the analgesic effect of morphine. The purpose of our study was to evaluate the effect of adding small-dose ketamine in a multimodal regimen of postoperative patient-controlled epidural analgesia (PCEA). One hundred patients of American Society of Anesthesiologists physical status I-II, undergoing major upper abdominal surgery were randomly allocated to two groups. Group I received PCEA device containing bupivacaine hydrochloride 0.0625% and morphine sulphate (preservative free) 0.05mg/ml. Group II received PCEA device containing bupivacaine hydrochloride 0.0625%, morphine sulphate (preservative free) 0.05 mg/ml and ketamine hydrochloride (preservative free) 0.2 mg/ml. The mean morphine consumption in group I after 1(st)and 2(nd)postoperative day was 8.38±2.85 and 7.64±1.95 mg, respectively, compared to 6.81±1.35 and 6.25±1.22 mg (P<0.05) in group II. Although group II consumed significantly less morphine, pain relief at rest and at movement after 6, 12, 24 and 48 hours, postoperatively was significantly better in group II (P<0.05) than in group I. These findings suggest that adding small-dose ketamine to a multimodal PCEA regimen provides better postoperative analgesia and reduces morphine consumption.