The dose and volume-response relationship of an ethanol-induced tibial nerve block in a rabbit model.

Abstract

The aim of this study was to observe the dose-response relationship in an ethanol-induced tibial nerve block in a rabbit model. Sixteen New Zealand white rabbits were separated into three groups that received increasing injections of 100% ethanol (0.1, 0.3, and 0.5 ml). All tibial nerves were successfully located with a nerve stimulator. Compound muscle action potentials were measured before injection; 1, 2, 4, and 7 days after injection; and 2, 3, 4, 5, 6, 7, and 8 wks after injection. Histologic studies were performed to evaluate the destruction of the nerves and surrounding muscles. The compound muscle action potential amplitude significantly decreased (P < 0.01) on the first day after ethanol injection in all groups. The compound muscle action potential amplitude in the 0.1-ml group recovered to baseline by week 2, whereas the 0.3-ml group recovered by week 8. The 0.5-ml group did not recover by week 4 (P < 0.01), but observations had to stop because of severe complications. The authors found that the degrees of axonal degeneration and muscle desmoplasia were related to injection volume. There was a positive linear relationship between ethanol injection volume and effect on compound muscle action potential. The safe and effective volume of 100% ethanol for a tibial nerve block is 0.3 ml in a rabbit model.