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′ISO60) 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′ISO60 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′ISO60, 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.