Plasma Concentrations of Lidocaine Associated with Epidural Anesthesia and Axillary Nerve Block

Forty adult patients who received lumbar epidural anesthesia and axillary nerve block were assigned to four groups. Of these, 15 patients in group 1 (lumbar epidural anesthesia group) were given 1.5% lidocaine 400 mg (27 ml) and 15 patients in group 2 (lumbar epidural anesthesia group) were given lidocaine with epinephrine (200,000:1) in the same volume and concentration as in group l. 5 patients in group 3 (axillary nerve block group) were given lidocaine in the same volume and concentration and 5 patients in group 4 (axillary nerve block group) were given lidocaine with epinephrine (200,000:1). The plasma concentration of lidocaine were measured by immunofluorescence assay and the peak concentration were achieved 15 and 30 min, after injection in group 1, 2, respectively. Similar results were observed in group 3 and 4. The peak plasma concentration in group 1, 2,3 and 4 were 2.85±1.17, 1.81±0.60, 2.35±0.97 and 1.62± 0.67 μg/ml (Mean±SD), respectively. and the time course of plasma levels of lidocaine in group 2 and 4 lower than those in group 1 and 2. These results indicate the mixed injection of 1.5% lidocaine 400 mg with epinephrine is considered safe when there is no contraindication because plasma concentration is reduced significantly.