“Triceps Brachii Muscle Response to Neurostimulation of the Radial Nerve during Axillary Plexus Blockade: Clinical, Anatomical and Histological Correlation”

Abstract

Axillary plexus blockade is a common technique in clinical practice with a well-known pattern of structures around the brachial artery. Historically, the only proper response to radial nerve stimulation was considered to be extension of the hand and wrist. Twenty-five axillary blockades were assessed by ultrasound and neurostimulation; the principal objective was to correlate the needle position over the radial nerve with the anatomical and histological structure of that nerve. During the procedure, the needle was directed in two ways to reach the medial or lateral margin of the nerve: above the brachial artery or beneath it. Once the needle reached the nerve, the current was augmented gradually until a response was elicited. For the cadaveric anatomical study, eight axillae were dissected and histological samples were examined. The response of the triceps brachii muscle differed significantly between the two approaches to the radial nerve (P < 0.001), and the mean intensity of stimulation was significantly lower when the nerve was accessed above the artery (0.44 AE 0.15 mA) than below it (0.57 AE 0.17 mA) (P = 0.015). A triceps brachii motor response occurs at lower current intensity and lower needle-nerve distance when the radial nerve is accessed above the artery and over the latissimus dorsi tendon. These findings were correlated with the topography of the radial nerve in the axillary fossa. Clin. Anat. 33:578-584, 2020.

Comparison of the anesthesia effect of ultrasound-guided middle and low interscalene brachial plexus block: a randomized, controlled, non-inferiority trial

“…The deltoid, pectoralis, and biceps were mainly dominated by the C5 and C6 nerves, and any contraction of these muscles was considered the motor response of the superior trunk [ 16 , 17 ]. Similarly to previous studies, no extension of the wrist or fingers but the contraction of the triceps brachii was observed in our study with a current set at 0.4 mA when stimulated in the ventral ramus C7, which contributed largely to the radial nerve, so the contraction of the triceps brachii was considered to be the motor response to the stimulation of the middle trunk [ 18 , 19 ]. Due to the high accuracy feature, flexion of the fingers was considered the motor response elicited by the inferior trunk [ 20 , 21 ].…”