Ultrasound-Guided Lateral Transversus Abdominis Plane (TAP) Block in Rabbits: A Cadaveric Study

The aims of the study were to describe the ultrasonographic-guided lateral TAP block in rabbit cadavers and evaluate the spread of a lidocaine/methylene blue solution through a single fascial infiltration. The US-guided block and anatomical dissections were performed in 17 New Zealand rabbit cadavers. The probe was placed perpendicular to the column, one centimetre ventrally to the transverse processes, halfway between the iliac crest and the costal margin. External oblique (EO), internal oblique (IO), and transversus abdominis (TA) muscles were visualised, and 1 mL/kg of lidocaine 2% plus methylene blue 1% was injected. After dissection, the branches of spinal nerves stained were measured. Moreover, the percentage of length and height of the area marked were calculated. A good visualisation of the TAP was obtained in all 34 hemiabdomens. T11 nerve eminence was successfully stained in 52% of cases. T12, L1, and L2 were stained in 75%, 95%, and 100% of cases, respectively. L3 and L4 were stained in 60% and 40% of cases, respectively. The lateral TAP block with a single point of injection can be easily performed in rabbits, but it is not sufficient to cover the nerve eminences of the cranial abdomen. The two-point TAP block (lateral and subcostal) could represent a better option, particularly when large surgical incisions are required.