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) (EI(8) 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 EI 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 EI 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 EI was dose dependent (P < 0.05), and the half maximal inhibition concentration of EI was 5.46%.


CONCLUSIONS
EI produced completely reversible and dose-dependent nerve conduction inhibition, which had slower onset and faster recovery compared with those produced by lidocaine.
Li
Zhuo
Z
Laboratory of Anesthesia and Critical Care Medicine, State Key Laboratory of Biotherapy of Cancer, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China. weiweiyang72@gmail.com
Yang
Jing
J
Liu
Jin
J
Gong
Chun-Yu
CY
Gan
Jing
J
Zhang
Xian
X
Luo
Wen-Jun
WJ
Li
Guo-Hua
GH
D000200:Action Potentials / Q000187:drug effects; D000765:Anesthesia, Conduction / Q000379:methods*; D018685:Anesthetics, Inhalation / Q000008:administration & dosage* / Q000494:pharmacology*; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002023:Bufo bufo; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004553:Electric Conductivity; D004594:Electrophysiology; D005217:Fat Emulsions, Intravenous; D066298:In Vitro Techniques; D007530:Isoflurane / Q000008:administration & dosage* / Q000494:pharmacology*; D009407:Nerve Block / Q000379:methods*; D009431:Neural Conduction / Q000187:drug effects*; D012584:Sciatic Nerve / Q000187:drug effects*; D012964:Sodium / Q000378:metabolism
D018685:Anesthetics, Inhalation; D005217:Fat Emulsions, Intravenous; D012964:Sodium; D007530:Isoflurane