Erector spinae plane block reduces intraoperative nociception in bitches undergoing ovariohysterectomy: A randomised clinical trial

BACKGROUND: Erector spinae plane (ESP) block is a regional anaesthetic technique described in dogs, but clinical evidence of its perioperative effects in abdominal procedures remains limited. This study evaluated its antinociceptive efficacy during elective ovariohysterectomy in bitches. METHODS: Sixteen healthy client-owned female dogs were randomly assigned to two groups (n = 8). All the patients received 0.05 mg/kg acepromazine and 0.3 mg/kg methadone intramuscularly, followed by propofol-based induction and maintenance. Ultrasound-guided bilateral ESP blocks were performed at the first lumbar vertebra using 0.25% bupivacaine (0.5 mL/kg per side) in the bupivacaine group or 0.9% saline in the saline solution group. Vital signs and nociceptive responses were recorded intraoperatively; 2.5 µg/kg fentanyl intravenously was used as rescue analgesia. Postoperative pain was assessed over 24 hours using the short-form Glasgow pain scale. RESULTS: The ESP group required significantly fewer intraoperative fentanyl rescues (8 vs. 19; p = 0.031). No significant differences were observed in postoperative pain scores or analgesic rescue requirements. LIMITATIONS: The small sample size and use of physiological nociceptive indicators may limit generalisability. Only a single non-opioid postoperative rescue was needed, potentially masking postoperative differences. CONCLUSION: Ultrasound-guided ESP block reduces intraoperative opioid use in dogs undergoing ovariohysterectomy but has limited impact on postoperative pain control.