Open Approach Transversus Abdominis Plane Block for Postoperative Pain Management in Bitches Undergoing Ovariohysterectomy: First In Vivo Study

OBJECTIVE: To compare the postoperative analgesic efficacy of the Open Approach Transversus Abdominis Plane block with the traditional ultrasound-guided technique in female dogs undergoing elective ovariohysterectomy. STUDY DESIGN: Prospective, randomized, controlled, blinded clinical study. ANIMALS: Ten female dogs, weighing 3-5 kg, aged between 1-6 years. METHODS: Animals were divided into two groups to receive either the ultrasound-guided TAP block (G-US, n = 5) or the open-approach TAP block (G-OA, n = 5). Pre-medication with methadone (0.3 mg/kg) was followed by propofol induction (4 mg/kg IV) and isoflurane maintenance. The TAP block was performed using 0.25% bupivacaine at a total dose of 0.3 mL/kg, administered as 0.15 mL/kg per side of the abdomen. Postoperative monitoring for 24 hours assessed physiological parameters and pain using the Visual Analogue Scale (VAS) and the Short Form of the Glasgow Composite Pain Scale (CMPS-SF). Data were analyzed using ANOVA, Chi-square, and Shapiro-Wilk tests, with significance set at P < 0.05. RESULTS: The Open Approach technique significantly reduced block execution time (p < 0.001) compared to the US-guided approach. No significant differences were observed between groups in postoperative pain scores (VAS, p = 0.054; CMPS-SF, p = 0.922) or additional analgesic requirements (p > 0.999). CONCLUSION AND CLINICAL RELEVANCE: The Open Approach TAP block is a safe and effective alternative to the ultrasound-guided technique for dogs undergoing OVH. It provides comparable analgesia while reducing procedural time and eliminating ultrasound-related risks. Its simplicity may enhance clinical accessibility, making it a valuable addition to veterinary locoregional anesthesia.