Ultrasound and gross anatomy of the brachial plexus and major nerves of the forelimb. An anesthetic approach using the domestic rabbit (Oyctolagus cuniculus) as an experimental model1.

Rodrigo Mencalha,Carlos Augusto Dos Santos Sousa,Marcelo Abidu-Figueiredo,Orlando Costa

doi:10.1590/s0102-865020160040000001

Rodrigo Mencalha, Carlos Augusto Dos Santos Sousa + Show 2 more

Open Access

https://doi.org/10.1590/s0102-865020160040000001

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Abstract

To update the gross and sonographic anatomy and propose landmarks to perform ultrasound-guided (US-guided) axillary brachial plexus block (BPB) in rabbits. Forty New Zeeland's rabbit (NZR) cadavers were dissected and the nerves were trimmed, identified, measured, and photographed. Additionally, in twenty NZRs, sonographic images of brachial plexus (BP) were performed through a simple-resolution ultrasound device. The US-guided block was achieved through a minimum volume of lidocaine necessary to surround the BP roots. The effectiveness of the brachial plexus block was assessed on sensitivity and motor functions. The BP resulted from connections between the ventral branches of the last four cervical spinal nerves and the first thoracic spinal nerve. In the axillary sonoanatomy, the BP appeared as an agglomerate of small, round hypoechoic structures surrounded by a thin hyperechoic ring. The amount of time and the minimum volume required to perform was 4.3 ± 2.3 min and 0.8 ± 0.3ml, respectively. The gross and sonographic anatomy of the BP showed uncommon morphological variations. Moreover, from sonographic landmarks, we showed complete reproducibility of the axillary US-guided brachial plexus block with simple resolution equipment and small volume of anesthetics required.

Highlights

MethodsSurgical orthopedic and oncologic procedures in the forelimb are routinely performed in humans and small animals, triggering neuroendocrine responses and severe postoperative pain
Locoregional anesthesia and peripheral nerve blocks are widely used in human anesthesia, and the use and evaluation of this technique have been described in small and laboratory animals
According to the combination of the ventral branches of C4, C5, C6, C7, C8, T1 and T2 as roots of brachial plexus, three types were obtained with different origins

Summary

Introduction

Surgical orthopedic and oncologic procedures in the forelimb are routinely performed in humans and small animals, triggering neuroendocrine responses and severe postoperative pain. Locoregional anesthesia and peripheral nerve blocks are widely used in human anesthesia, and the use and evaluation of this technique have been described in small and laboratory animals. Locoregional blocks were exclusively performed through anatomical references, and had high rates of failure and injury. Currently high-resolution electronic ultrasound (US) transducers have been increasingly used for human regional anesthesia, allowing visualization of the neural and adjacent structures as well the dispersion of local anesthetic in real time. Sonographic visualization enables optimal distribution of local anesthetics around the nerve structures and the avoidance of complicated procedures such as intraneural and intravascular injection

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