Postoperative analgesia after peripheral nerve block for pediatric surgery: Clinical efficacy and chemical stability of lidocaine alone versus lidocaine Plus Ketorolac

Background and Objectives: The purpose of this study was to determine wheth er the addition of ketorolac tromethamine to local anesthesia for ankle blo ck alters the quality or duration of analgesia after pediatric surgery. The second aim was to determine the chemical stability of ketorolac tromethami ne when added to local anesthetic solutions. Methods: The study design was double-blinded, placebo-controlled, and rando mized. Seventy-nine American Society of Anesthesiologists (ASA) class I or 17 patients scheduled for bunionectomy or hammer toe repair, or both were r andomized to 1 of 4 groups. Group L received plain 1.73% lidocaine for thei r ankle block. Group It received 1.73% lidocaine with ketorolac (4 mg/mL) a dded to the local solution. Group Kiv received 1.73% plain lidocaine for an kle block and 20 mg of ketorolac intravenously. Group E received 1.73% lido caine with .67% ethanol added. The final concentration of lidocaine for all groups was 1.73%. The block performed in each patient was a 5-point ankle block. Beginning at 1 hour after the completion of the block and every 30 m inutes thereafter, visual analogue stale (VAS) and verbal pain scores were recorded. The time from performance of the block to the initial pain and ti me to the first oral pain meditation intake were also recorded. The lime an d amount of postoperative oral analgesics in the first 9 hours after the bl ock were recorded. Adverse events were also recorded for each group. Results: There were significantly lower overall VAS and verbal pain scores for group K compared with groups E and L and group Kiv compared with group E. Group It also had a significantly longer time to the first reported pain and first oral pain medications than groups E and L, but not with Group Ki v. The same group had significantly fewer average doses of pain medications postoperatively than Groups E and L. Group E had significantly shorter tim es to first report of pain and first pain medications and higher mean dose of postoperative oral analgesics than group K and Group Kiv. There were no untoward side effects reported from any group. Chemical analysis by gas chr omatography (GC) and capillary electrophoresis (CE) showed no significant c hange in composition of the solutions when ketorolac was mixed with lidocai ne and/or bupivacaine and stored at 37 degrees C for 1 week. Conclusions: The addition of ketorolac to Lidocaine for ankle block contrib uted to longer duration and better quality analgesia after foot surgery com pared with plain 1.73% lidocaine or 1.73% lidocaine plus intravenous ketoro lac. The ethanol vehicle is unlikely responsible far the analgesic effects of ketorolac. Ketorolac retains its chemical stability when placed in local solutions of lidocaine or bupivacaine.