Comparison of analgesic efficacy of epidural methadone or ropivacaine/methadone with or without pre-operative oral tepoxalin in dogs undergoing tuberositas tibiae advancement surgery.

Objective   To investigate the clinical efficacy of four analgesia protocols in dogs undergoing tibial tuberosity advancement (TTA). Study design  Prospective, randomized, blinded study. Animals  Thirty-two client owned dogs undergoing TTA-surgery. Methods  Dogs (n = 8 per treatment) received an oral placebo (PM and PRM) or tepoxalin (10 mg kg(-1) ) tablet (TM and TRM) once daily for 1 week before surgery. Epidural methadone (0.1 mg kg(-1) ) (PM and TM) or the epidural combination methadone (0.1 mg kg(-1) )/ropivacaine 0.75% (1.65 mg kg(-1) ) (PRM and TRM) was administered after induction of anaesthesia. Intra-operative fentanyl requirements (2 μg kg(-1) IV) and end-tidal isoflurane concentration after 60 minutes of anaesthesia (Fe'ISO(60) ) were recorded. Post-operative analgesia was evaluated hourly from 1 to 8 and at 20 hours post-extubation with a visual analogue scale (VAS) and the University of Melbourne Pain Scale (UMPS). If VAS > 50 and/or UMPS > 10, rescue methadone (0.1 mg kg(-1) ) was administered IV. Analgesic duration (time from epidural until post-operative rescue analgesia) and time to standing were recorded. Normally distributed variables were analysed with an F-test (α = 0.05) or t-test for pairwise inter-treatment comparisons (Bonferonni adjusted α = 0.0083). Non-normally distributed data were analysed with the Kruskall-Wallis test (α = 0.05 or Bonferonni adjusted α = 0.005 for inter-treatment comparison of post-operative pain scores). Results  More intra-operative analgesia interventions were required in PM [2 (0-11)] [median (range)] and TM [2 (1-2)] compared to PRM (0) and TRM (0). Fe'ISO(60) was significantly lower in (PRM + TRM) compared to (PM + TM). Analgesic duration was shorter in PM (459 ± 276 minutes) (mean ± SD) and TM (318 ± 152 minutes) compared to TRM (853 ± 288 minutes), but not to PRM (554 ± 234 minutes). Times to standing were longer in the ropivacaine treatments compared to TM. Conclusions and clinical relevance  Inclusion of epidural ropivacaine resulted in reduction of Fe'ISO(60) , avoidance of intra-operative fentanyl administration, a longer duration of post-operative analgesia (in TRM) and a delay in time to standing compared to TM.