Reversible Conduction Block in Isolated Toad Sciatic Nerve by Emulsified Isoflurane

BACKGROUND: Studies have shown that the local use of volatile anesthetics can produce local anesthetic effects. We designed this study to evaluate the characteristics of nerve conduction block of emulsified isoflurane (EI) and compare its nerve blockade with 1% lidocaine, by measuring compound nerve action potential (CNAP) parameters in isolated toad sciatic nerve. METHODS: One hundred isolated toad sciatic nerves were selected and randomly assigned to 10 groups of 10 each, administered 2% to 8% EI (v/v) (EI8 group, etc.), 1% lidocaine, 30% Intralipid (R) (Huarui Pharmacy, Wuxi, Jiangsu, China), and Ringer solution (RS) for 10 minutes, respectively. All nerves were then washed and soaked with RS for 10 minutes and 30 minutes. The nerve conduction block effect was represented by CNAP parameters that were recorded by an extracellular recording technique per minute. RESULTS: The results showed that the negative amplitudes of CNAP were decreased by El and lidocaine (P < 0.05), and the conduction velocities of CNAP were also decreased at some time points (D7-W3) (P < 0.05). After RS washing, the 2 parameters recovered gradually. The changes in the 2 parameters induced by El had slower onset rates and faster recoveries than those produced by lidocaine (7 minutes vs 1 minute and 9 minutes vs 30 minutes). The nerve blockade induced by El was dose dependent (P < 0.05), and the half maximal inhibition concentration of El was 5.46%. CONCLUSIONS: El produced completely reversible and dose-dependent nerve conduction inhibition, which had slower onset and faster recovery compared with those produced by lidocaine. (Anesth Ana Ig 2010;110:1024-9)