Evaluation of peri-operative epidural analgesia with ropivacaine, ropivacaine and sufentanil, and ropivacaine, sufentanil and epinephrine in isoflurane anesthetized dogs undergoing tibial plateau levelling osteotomy

The purpose of this study was to compare four epidural protocols for peri-operative analgesia in dogs undergoing tibial plateau levelling osteotomy. Forty client-owned dogs were randomly assigned to one of four treatments - groups R0.5 and R1 received 0.5mg/kg and 1mg/kg ropivacaine, respectively. Group SR0.5 received 1mug/kg sufentanil plus 0.5mg/kg ropivacaine, and group SER0.5 received 1mug/kg sufentanil, 0.5mg/kg ropivacaine plus 6mug/kg epinephrine. Dilution, when required, was performed with saline, so that the injected volume was always 0.2mL/kg. Intra-operatively, nociception assessment was based on the evaluation of changes in heart rate, respiratory rate and mean arterial pressure. Post-operative pain assessment was performed using the Glasgow visual analogue pain scale, and an ad hoc multifactorial pain score. Motor block was evaluated using a modified Bromage score. Intra-operatively, none of the animals was hypotensive. All groups except SER0.5 required rescue intra-operative fentanyl (40%, 30% and 40% of the animals in groups R0.5, R1 and SR0.5, respectively). Group SER0.5 showed lower post-operative pain scores, and group R1 significantly greater motor block, compared to the other treatment groups. None of the dogs had urinary retention. Epidural sufentanil-epinephrine-ropivacaine provided superior peri-operative analgesia compared to the other treatments, without producing clinically relevant side effects.