Dose-Response of Ketorolac as an Adjunct to Patient-Controlled Analgesia Morphine in Patients After Spinal Fusion Surgery

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Abstract
This randomized, blind study was designed to determine the appropriate dose of ketorolac (a drug used as a supplement to opioids) to administer to patients who have undergone spinal stabilization surgery. The ketorolac was administered every 6 h, in addition to patient-controlled analgesia (PCA) with morphine, to 70 inpatients undergoing spine stabilization by one surgeon. The study was performed to determine the analgesic efficacy and incidence of side effects with different doses of ketorolac. The patients were divided into seven groups. They were given either i.v. saline (control group) or i.v. ketorolac (5, 7.5, 10, 12.5, 15, or 30 mg) every 6 h. The outcomes measured included pain scores, 24-h morphine usage, level of sedation, and side effect profile six times during the first 24 h postoperatively. The total dose of morphine was significantly larger in the control and 5 mg ketorolac groups than in the other five groups. Morphine consumption was similar in all groups receiving > or = 7.5 mg of ketorolac. The pain scores were significantly higher in the control group than in some of the larger dose groups at three of the study intervals. The 5 mg group had higher pain scores than the other groups at most of the time intervals studied. There were no significant differences in pain scores among the other five groups. Sedation scores were higher (i.e., patients were more sedated) in the control group than in the other six groups at three of the time periods. We conclude that the administration of ketorolac 7.5 mg every 6 h has a morphine-sparing effect equivalent to that of larger doses in patients undergoing spine stabilization surgery. Using larger doses of ketorolac did not result in less somnolence, lower morphine use, or less pain. We recommend that ketorolac 7.5 mg be given every 6 h to patients undergoing spinal fusion surgery in addition to PCA morphine. Using smaller doses of ketorolac (e.g., 7.5 mg every 6 h) as a supplement to morphine patient-controlled analgesia is as effective as larger doses in patients who have undergone spine stabilization surgery.