Phenol block of peripheral nerve condition: titrating for optimum effect. (Sungkyunkwan University of Medicine, Seoul, Korea). Arch Phys Med Rehabil. 2001;82:671–676.

This experimental study was conducted to verify the dose-response relationship in phenol nerve block and to determine the concentration and volume of phenol injectate required for effective nerve conduction block. The test group consisted of 71 New Zealand white rabbits. Group I (n = 48) received tibial nerve block by perineural injection (phenol, n = 40; saline, n = 8), Group II (n = 21) by submerging the nerve in phenol solution. The 6 subgroups of Group I each received different concentrations (3%, 4%, 5%) and volumes (0.1 mL, 0.2 mL, 0.3 mL). Compound muscle action potential (CMAP) and tension of triceps surae muscles by electric stimulation of the sciatic nerve were measured preintervention and at day 1, and weeks 1, 2, 4, and 8 postblock. Histologic studies were performed on 2 animals from group I. Two rabbits in Group I died before results were obtained. In the remaining animals, CMAP amplitude reduced significantly as the volume of 5% phenol solution increased from 0.1 mL, 0.2 mL, to 0.3 mL. A high concentration of phenol produced a more pronounced conduction block; however, no significant difference existed among the 3 concentrations. Submerged tibial nerve had a greater degree of conduction block than perineurally injected nerve. Depth of the degeneration area in nerve fascicle varied with distance from the injection point. Conclude that the nerve block effect of phenol can be titrated by adjusting the concentration and volume of phenol solution if the technique of application and localization of a block site are standardized.