Abstract
Transversus abdominis plane (TAP) block is a regional anesthetic technique used to desensitize the abdominal wall in several species. This study aimed to describe the anatomical characteristics of the abdominal wall and to identify a feasible approach for an US-guided TAP injection that would result in adequate staining of the relevant nerves in the abdominal wall in pig cadavers. Fresh cadavers from five Landrace pigs (age, 12 weeks; body weight, 35.5 ± 1.6 kg) were used. One pig (n = 1) was anatomically dissected, and four pigs (n = 4; i.e., 8 hemiabdomens) were used for TAP injections and evaluation of dye spread. The volume of 0.3 mL/kg/injection point of methylene blue was injected bilaterally. In the caudal retrocostal approach, the injection was performed ventral to the most caudal part of the costal arch. In the lateral approach, the injection was performed between the last rib and iliac crest. A needle was inserted in plane for the caudal retrocostal and the lateral approach caudocranially and craniocaudally, respectively. Successful staining was defined as presence of dye on the nerve for a length of >1 cm in its entire circumference. The TAP was found between different muscle layers in the described anatomical regions. In the caudal retrocostal approach the TAP was found between the external abdominal oblique and transversus abdominis muscle bellies. In the lateral approach the TAP was found between the internal abdominal oblique and transversus abdominis muscles. The approach combining lateral and caudal retrocostal injections at the studied volume stained a median of 5 (3–6) target nerves from the fourth-last thoracic nerve to L2 (six nerves). Combined caudal retrocostal and lateral TAP injections of 0.3 mL/kg/injection point, resulted in staining of target nerve branches which supply the periumbilical and caudal abdominal wall in pig cadavers.
Highlights
Regional anesthesia is a widely used technique in human and veterinary medicine [1]
The ultrasound-guided transversus abdominis plane (TAP) block is a regional anesthetic technique used in humans to desensitize the anterolateral abdominal wall, which corresponds to the ventrolateral abdominal wall in veterinary patients [9, 10]
The belly of the IOM was absent (Figs 1 and 2D). Both in the caudal retrocostal and lateral injection point, ventral rami of thoracolumbar nerves were found running within the TAP
Summary
Regional anesthesia is a widely used technique in human and veterinary medicine [1]. It provides numerous benefits in the minimization of adverse effects over other techniques such as the use of systemic analgesics [1, 2]. Based on anatomical similarities observed in the innervation of the abdominal wall between species [9,10,11,12,13], this technique has been extrapolated to animals undergoing abdominal surgery (e.g., dog, cat, horse, calf, lynx, chinchilla) [14,15,16,17,18,19]. Further development of this block has occurred in veterinary medicine as anatomy of the abdominal wall differs between the species. Despite the popularity of the TAP block and the commonly performed abdominal surgical procedures in pigs, either for clinical or research purposes, this technique has not yet been investigated in this species
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