Anatomical Evaluation of the Thoracolumbar Nerves Related to the Transversus Abdominis Plane Block Technique in the Dog

Abstract

Transversus abdominis plane (TAP) is a fascial plane containing the thoracolumbar nerve branches that innervate the abdominal wall. Limited information is available on the anatomical organization of these nerve branches in the dog, which is of great importance for the success of the TAP block anaesthetic technique. The aim of this study was to describe the origin and conformation of thoracolumbar nerves running through the TAP in 20 hemi-abdominal walls of 10 adult mongrel dog cadavers with an average body weight of 12.6 kg (range: 9.6-15.6). The abdominal walls were dissected from superficial to deep direction, the skin and both obliquus externus abdominis and obliquus internus abdominis muscles were dissected and reflected dorsally to expose the transversus abdominis muscle and the thoracolumbar nerve branches located in this plane. The anatomical features of ventral nerve branches were described. The thoracic nerve branches: T7-T12 and costoabdominalis; and the lumbar nerve branches: iliohypogastricus cranialis, iliohypogastricus caudalis, ilioinguinalis and cutaneus femoris lateralis were identified in all the cadavers. Anatomical variations related to the presence or absence within the TAP of the T7, T8 and T9 nerve branches were found. These variations should be taken into account when planning the TAP block technique in dogs.

A Retrospective Study of Vertebral Fracture and Luxation in Dogs Presented to University Veterinary Hospital, Universiti Putra Malaysia in 2015 to 2017

“…The dogs admitted to UVH, UPM were mostly local breed and stray dogs; hence, it is expected to be overrepresented in this study. Despite various breeds in the study, the spinal anatomy between breed, size or age are comparable (Bodh et al, 2016; -Herrera et al, 2017); thus, it is less likely to affect the nature of the lesion.…”

Anatomical Differences in the Abdominal Wall Between Species with Implications for the Transversus Abdominis Plane Block

“…The canine abdominal wall receives innervation from spinal nerves T7 to L3 and, as previously mentioned, dogs have a 13 th thoracic vertebrae (and subsequent rib and spinal nerve) that is absent in humans [46,47,[71][72][73]. Interestingly, in dogs, the umbilicus is innervated by T10 as it does in humans [47,71].…”

“…Additionally, there is considerable variation in the course of the canine upper thoracic nerves from T7 to T9 and their presence in the TAP. Often, only the spinal nerves from T10 to L2 are found within the TAP of dogs [72]. Similarly, in primates, the upper T8 and T9 are occasionally absent from the TAP overlying the transversus abdominis [53].…”

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

“…This locoregional technique involves the infiltration of local anaesthetic into the fascial plane between the internal oblique and transversus abdominis muscles to block the sensory components of the abdominal wall. Recently, the TAP block has been introduced in veterinary anaesthesia, both in experimental and clinical settings [4][5][6][7]. This technique involves injecting a volume of local anaesthetic into the neurovascular plane between the transversus abdominis and internal oblique muscle in order to saturate somatic afferents before they leave the TAP and provide analgesia in that anatomical area [8,9].…”

“…Anatomical studies carried out in dogs showed that the nerves involved in TAP are the ventral branches of T11-T13 and L1-L3. These nerves are the target of the anaesthetic block in this plane [5,11]. Using the ultrasound-guided (US-guided) technique, the TAP can be correctly identified and, both the needle trajectory and injectate spread can be performed between the IO and TA muscle layers with accuracy and safety, potentially reducing the risk of block failure, accidental intraperitoneal injection, and injury to adjacent structures [14,15].…”