Factors affecting localization and dispersion of alcohol in peripheral nerve block

Abstract

OBJECTIVE: To explore the relationship between electrical current and nerve-needle distance for localization of target nerves in peripheral nerve block, and the effects of injection speed, concentration, and injectate volume on alcohol dispersion using an animal model. METHODS: Rabbit tibial nerves were selected for localization. Nerve-needle distance was ascertained using a manipulator. The minimum current eliciting motor responses was recorded at nerve-needle distances of 0, 1, 2, 3, 4 and 5 mm. Rabbit tibial nerves were assigned into 3 groups: speed group, concentration group, and volume group. Nerves were localized by a stimulator and neurolysed with alcohol/contrast medium. Helical computed tomography (CT) was performed to measure volume/dispersion patterns of injectate. RESULTS: A linear relationship was observed between nerve-needle distance (X) and minimal current (Y) (Y = 0.13X + 0.22; r2 = 0.974; p<0.05) for the localization of the target nerve. CT scan revealed that the injection speed and volume significantly influenced the dispersion of alcohol (p<0.01), but concentration had no effect (p<0.05). CONCLUSION: This study found a positive linear relationship between nerve-needle distance and minimum electrical stimulation in tibial nerve blockade. In addition, the results suggest that a low volume of alcohol with a low injection speed can help to improve nerve block in clinical practice.