Factors affecting localization and dispersion of alcohol in peripheral nerve block.

Abstract

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. 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. 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). 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.