Thoracolumbar epidural anaesthesia with 0.5% bupivacaine with or without methadone in goats

BACKGROUND Epidural anaesthesia is one of the most commonly used locoregional techniques in ruminants. The lumbosacral epidural technique is reasonably easy to perform and requires low volumes of local anaesthetic drug to allow procedures caudal to the umbilicus. However, surgical procedures in the flank of the animal would require an increased volume of drugs. The anaesthetized area provided by thoracic epidural technique is larger than the lumbosacral technique; however the former is rather challenging to perform. Therefore, access through lumbosacral area to introduce a catheter into the thoracolumbar space is a potential alternative to thoracic access. Epidural anaesthesia is achieved with local anaesthetics; opioids can be added to improve analgesia. This study aimed to evaluate the effects of 0.5% bupivacaine with or without methadone, administered through an epidural catheter inserted through the lumbosacral access and advanced to the thoracolumbar space, on thoracolumbar epidural anaesthesia in goats. METHODS Six animals received two treatments each in a randomized crossover study: BUP treatment consisted of 0.5% bupivacaine (1 mL per each 10 cm of spine column; 1 ± 0.2 mg/kg BW) and BMT treatment was the same; however 1 mL of bupivacaine was replaced by 1 mL (0.22 ± 0.03 mg/kg BW) of methadone (10 mg/mL). The treatments were administered near to T11-T12 through an epidural catheter. Motor blockade and analgesia were evaluated by electrical stimulation. RESULTS Heart rate, respiratory rate, ruminal motility and rectal temperature were evaluated before and after the treatment. Motor blockade was observed on both treatments, up to 6 h post-treatment. Analgesia was observed on BUP up to 4 h and on BMT up to 6 h post-treatment. Physiological values did not change at any moment. CONCLUSIONS Bupivacaine-methadone combination promoted longer-lasting analgesia in goats compared to bupivacaine alone when administered through an epidural catheter into the thoracolumbar space.