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

Abstract 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.