Use of the rectus sheath block for perioperative analgesia in three foals undergoing omphalectomy and cystoplasty

Locoregional techniques promote multimodal analgesia and may reduce general anaesthetic requirements. However, there is limited evidence in foals. The rectus sheath block (RSB) is an interfascial plane block previously described in other species such as dogs, cats, pigs, and calves, and recently in foals, which targets desensitization of ventral abdominal midline. This block may provide an efficacious analgesic alternative for ventral celiotomies and umbilical surgeries. This case series reports the use of a bilateral RSB with 0.25-0.3 mL kg^-1 bupivacaine (maximum dose of 2 mg kg^-1) per hemiabdomen for perioperative analgesia in three client-owned foals undergoing omphalectomy and cystoplasty under general anaesthesia. All foals were premedicated intravenously with xylazine and butorphanol, and anaesthesia was induced with ketamine and propofol. General anaesthesia was maintained with isoflurane in 100% oxygen. Bupivacaine was deposited between the rectus abdominis muscle and its internal sheath. Intraoperative antinociceptive response to surgical stimulus and haemodynamic changes were monitored and recorded during surgery. Intraoperative rescue analgesia (butorphanol or ketamine) was given if heart rate or mean arterial pressure increased > 20% from baseline due to surgical stimuli. Postoperatively, pain was assessed every 2 hours using a facial pain scale for foals, for 12 hours following extubation. In these three anaesthetized foals, the bilateral RSB contributed to perioperative analgesia, as postoperative pain scores indicated minimal discomfort, and no postoperative opioids were used.