Plasma Concentrations of Lidocaine Associated with Cervical, Thoracic, and Lumbar Epidural Anesthesia

We measured arterial plasma concentrations of lidocaine by enzyme immunoassay when 10 ml of 2% lidocaine without epinephrine was injected into the cervical, thoracic, or lumbar epidural spaces in 30 patients. There was no difference in the time courses of plasma levels of lidocaine. Peak concentrations were achieved 10 min after injection and were similar regardless of the site of injection. These results indicate the absence of significant differences in the rate of vascular absorption of lidocaine from different parts of the epidural space.