Retrospective clinical evaluation of ultrasound guided transverse abdominis plane block in dogs undergoing mastectomy

History Eleven female dogs of different breeds undergoing unilateral radical (n=7) or regional abdominal mastectomy (n=4) received an ultrasound guided transverse abdominis plane block (TAP-block). Physical examination Subjects showed single or multiple mammary tumours. Serum biochemistry, CBC and electrocardiogram were unremarkable. Eight animals were classified as ASA physical status II and 3 as ASA III. Management Dogs were premedicated with methadone [0.1 or 0.2mgkg-1 intravenously (IV) or intramuscularly respectively] or fentanyl (2.5gkg-1 IV). Anaesthesia was induced with propofol and maintained with isoflurane or sevoflurane. Unilateral ultrasound guided TAP blocks were performed in the caudal and cranial abdomen with bupivacaine 0.25% (0.3 to 0.35 mLkg-1). Intercostal nerve blocks (T4 to T11) with bupivacaine 0.25% (0.013 to 0.04 mLkg-1) completed the blocked area in dogs undergoing radical mastectomy. Follow up The median (range) of end-expired isoflurane and sevoflurane necessary to maintain anaesthesia was 1.15 (1.07-1.22) and 2.07 (2.05-2.2) vol% respectively. A single administration of fentanyl (2.5gkg-1, IV) was administered to control nociception (defined as an increased heart rate or mean arterial blood pressure above 20% of the pre-incisional value) in four of 11 dogs. All dogs received carprofen (2mgkg-1 subcutaneously) at the end of surgery. Post-operative pain, assessed for 120minutes using the short form of Glasgow Composite Pain Scale (0-24), was always lower than 3. No rescue analgesia (allowed by the protocol) was required in this time. Conclusion Transverse abdominis plane block combined with intercostal nerve blocks may be useful to produce intraoperative anti-nociception and short term post-operative analgesia in dogs undergoing unilateral mastectomy.