Analgesic efficacy of an ultrasound-guided three-points transversus abdominis plane (TAP) block in bitches undergoing laparoscopic ovariectomy

This prospective, randomized, blinded and non-inferiority clinical study was conducted to assess the analgesic efficacy of ultrasound-guided transversus abdominis plane (TAP) block compared with administration of methadone in dogs undergoing laparoscopic ovariectomy. After intramuscular premedication with dexmedetomidine and methadone, dogs were randomly assigned to receive an ultrasound-guided TAP block with ropivacaine 0.25% (0.25ml/kg per point; group R, n = 22) or 0.9% saline (0.25ml/kg per point; group C, n = 20) at three points per hemiabdomen. Intraoperative end-tidal isoflurane, heart rate and invasive mean arterial pressure were recorded, and fentanyl (2mcg/kg IV) was administered as rescue analgesia if required. Postoperative pain was assessed at 1, 2, 4, 6, 8 and 24hours using the Glasgow Composite Measure Pain Score-Short Form (CMPS-SF), dynamic and interactive visual analogue scales (DIVASa, DIVASb and DIVASc), and mechanical nociceptive threshold (MNT). Methadone (0.2mg/kg IV) was administered every 4hours in group C and in both groups if CMPS-SF ≥ 6/24. Group R required a significantly lower amount of intraoperative fentanyl (p = 0.02) and isoflurane (p = 0.028) than group C. Postoperatively, group R showed significantly lower DIVASc scores (p = 0.013), while no differences were observed for CMPS-SF, DIVASa, DIVASb or MNT. Three bitches in group C required rescue methadone compared with none in group R. In conclusion, the three-points TAP block reduced intraoperative anaesthetic and opioid requirements and provided effective postoperative analgesia for 24hours in dogs undergoing laparoscopic ovariectomy.