PREEMPTIVE USE OF KETOROLAC IN LIMITED ORTHOPEDIC SURGERY

Abstract

S300 INTRODUCTION: Preemptive analgesia may prevent "sensitization" of the central nervous system and contribute to better postoperative pain relief with lower total doses of analgesics [1]. Ketorolac has been demonstrated to possess preemptive analgesic effects in hip surgery, but with increased blood loss [2]. The present study was designed to determine if ketorolac has preemptive effects in limited orthopedic surgery under tourniquet where the effects on blood loss should be minimal. METHODS: After IRB approval and informed consent, 29 patients ages 18-64, ASA 1-2, for ankle fracture repair, were enrolled in this double blind, randomized controlled trial. All patients received identical general anesthetics. Each patient was randomly assigned to one of two treatment groups: PRE (n=14) 30mg ketorolac administered IV 5 min. prior to tourniquet inflation with placebo after inflation and POST (n=15) 30mg ketorolac administered IV 5 min. after tourniquet inflation with placebo prior to inflation. All patients received postoperative morphine PCA. Morphine usage, visual analogue pain scores (VAS), postoperative nausea and vomiting scores (PONV) and presence/absence of excessive bleeding were recorded at 2, 4, 6, 8, 10 and 24 hours after tourniquet inflation. Postoperative nausea and vomiting (PONV) was recorded on a 5 point scale from 1 = no nausea to 5 = nausea with emesis. ANOVA was used to analyze morphine usage and VAS, and Kruskall-Wallis One-Way ANOVA for PONV. Statistical significance was defined as P<0.05. RESULTS: Patient demographics were similar. Two patients were eliminated in each group due to protocol errors or, in one case, to a surgical decision to abandon tourniquet usage. Group PRE patients had lower, but not statistically significant morphine requirements than Group POST at 2, 4 and 6 hours after tourniquet inflation. Both groups had similar requirements at 8, 10 and 24 hours (see Table 1).Table 1: Morphine requirements in [micro sign]g/Kg/hr (mean +/- 1 S.D.)VAS were identical between the PRE and POST groups. PONV was less in PRE at 6hr (PRE = 1 +/- 0, POST = 1.9 +/- 1.2, P = 0.006) and 8hr (PRE = 1.6 +/- 1.2, POST= 1.8 +/- 1.2, P = 0.008). No patient had excessive postoperative bleeding. DISCUSSION: Preliminary results of this study suggest a trend towards lower PCA requirements in the PRE group at approximately 2-6 hours after ketorolac administration, thus suggesting the existence of a preemptive analgesic effect. Lower PONV scores in the PRE group may be due to the lower morphine requirements. It is quite possible that the results will become significant once more patients are enrolled.