Intraoperative intravenous ketamine in combination with epidural analgesia: postoperative analgesia after renal surgery.

Abstract

We designed this double-blinded, randomized, controlled study to evaluate the effect of small-dose ketamine IV in combination with epidural morphine and bupivacaine on postoperative pain after renal surgery. An epidural catheter was inserted, and the administration of morphine and bupivacaine was started before surgery. Forty patients were assigned to one of two groups (ketamine or control). The ketamine group was administered a ketamine bolus and infusion during surgery. The median visual analog pain scale (VAS) scores at rest were significantly lower in the ketamine group during the first 6 h (P < 0.01). VAS pain scores on coughing were also significantly lower in the ketamine group (P < 0.01). Cumulative postoperative total analgesic consumption was less in the ketamine group on Days 1 and 2 (P < 0.001). The first analgesic demand time was shorter in the control group (9.2 +/- 11.5 min) than in the ketamine group (22.3 +/- 17.1 min) (P < 0.0001). The incidence of nausea and pruritus was more frequent in the control group (P < 0.05). In conclusion, postoperative analgesia was more effective when spinal cord and brain sensitization were blocked by a combination of epidural morphine/bupivacaine and IV ketamine. Renal nociception conducted multisegmentally by both the spinal nerves (T10 to L1) and the vagus nerve cannot be blocked by epidural analgesia alone. We demonstrated that IV ketamine had an improved analgesic or opioid-sparing effect when it was combined with epidural bupivacaine and morphine after renal surgery.