Effects of osmotic pressure on intrathecal and epidural lidocaine anesthesia

Lidocaine (1%), either in plain distilled water or in 10% dextrose, was intrathecally or epidurally administered to urethane-chloralose anesthetized cats. Electrical stimulation was applied to the gracile tract at a cervical level, and the resultant antidromic compound action potentials were recorded from the sural nerve. Lidocaine dissolved in plain distilled water was more effective than lidocaine dissolved in 10% dextrose solution in suppressing the compound action potentials. Lidocaine-free plain distilled water or dextrose solution caused partial suppression of the compound action potentils. The suppression was more marked following plain distilled water application than following application of 5% or 10% dextrose.