Transverse Abdominal Plane (TAP) Block in Rabbit Cadavers: Anatomical Description and Measurements of Injectate Spread Using One- and Two-Point Approaches

The aim of the study was to describe the loco-regional anesthesia technique "TAP block" at one and two points on a cadaveric model and to identify the most effective loco-regional technique during abdominal surgery in rabbit. For this purpose, after infiltration of the fascial plane and tissue dissection, lidocaine/methylene blue diffusion was measured by identifying and comparing the different diffusion areas and the percentage of stained nerve fibers. TAP injections under ultrasound guidance were performed in 30 rabbit cadavers. Fifteen rabbits (group S) were inoculated bilaterally with 1 mL/kg of 2% lidocaine and 1% methylene blue in the fascial plane between the internal oblique and transversus abdominis muscles, at the preiliac level. In the other 15 rabbits (group D), 0.5 ml/kg of the same molecules were inoculated in the same point, furthermore, the injection of 0.5 ml/kg of lidocaine/methylene blue was also repeated at the retrocostal level. All cadavers were then dissected and stained spinal nerve branches were measured. In addition, the percentage of length, height and the total area of the stained tissue were calculated. In S group, T10, T11 and T12 nerve eminences were successfully stained in 18%, 52% and 75% of cases, respectively. Moreover, L1, L2, L3 and L4 were stained in 95%, 100%, 60% and 40% of cases, respectively. In D group, the ventromedial eminence of T10, T11 and T12 were stained in 68.1%, 100% and 98% of cases, respectively, and L1, L2, L3 and L4 were stained in 88%, 100%, 62% and 31% of cases, respectively. In conclusion, TAP block with two-point approach is more effective in covering the nerve eminences of the cranial abdomen than the preiliac approach alone and, therefore, could represent the best technique of choice during abdominal surgical procedures in rabbit, especially if involved a large area of the abdomen.