Feasibility of a simultaneous ultrasound (US) and peripheral nerve stimulation (PNS) guided interscalene brachial plexus injection in calves

Abstract

The feasibility of a simultaneous ultrasound and peripheral nerve stimulation (PNS) guided interscalene brachial plexus injection was investigated in 6 calves, using three different techniques (2 calves per group, bilateral injections). Group 1: one aliquot of 0.3 mL/kg administered near the ventral branches of the eighth cervical/first thoracic (C8-T1) nerves. Groups 2 and 3: two aliquots of respectively 0.15 mL/kg and 0.3 mL/kg, one administered near C8-T1 and one near the ventral branches of the sixth/seventh cervical (C6-C7) nerves. The calves were sedated (0.2 mg/kg xylazine intramuscularly and 2 mg/kg ketamine intravenously) and positioned in lateral recumbency. Following aseptic preparation, a linear ultrasound probe was positioned at the shoulder level, transversely oriented to the longitudinal axis of the first rib. The ventral branches of C8-T1 and C6-C7 were visualised between the scalene muscles, and a 20 gauge insulated needle connected to a PNS was inserted in-plane until near the target nerves. A dye solution was injected once the motor response was absent below 0.4 mA stimulus. The procedure was repeated in the contralateral limb, and the calves were euthanised (70 mg/kg pentobarbital intravenously). Dissection was performed to assess nerve staining (Not stained, Poor, Partial or Complete circumference with at least 1-centimetre length).

Results

C8-T1: 3/4 completely and 1/4 partially stained (all groups). C6-C7: 0/4; 2/4; 4/4 partially, 3/4; 2/4; 0/4 poor and 1/4; 0/4; 0/4 not stained in groups 1, 2 and 3, respectively. In conclusion, this technique seems feasible. Further research is needed to determine the ideal injection volume.