A Comparison of Epidural Blockade Produced by Plain 1% Lidocaine and 1% Lidocaine Prepared by Dilution of 2% Lidocaine with the Same Volume of Saline

Abstract

Local anesthetics are commonly diluted with saline, but the influence of the dilution on the epidural anesthesia remains unclear. We randomized 40 patients scheduled for gynecological abdominal surgery under epidural anesthesia to one of two groups; those in group P received plain commercially prepared 1% lidocaine and those in group D received 1% lidocaine derived from 2% lidocaine and the same volume of saline was infused epidurally with an epidural catheter at L1-2. The pH and sodium and chloride ion concentrations of the solutions were measured. Sensory and motor blockade, foot skin temperature, arterial blood pressure, and heart rate were assessed at 5, 10, and 15 min after the epidural infusion. The spread of sensory blockade was significantly wider in group P at all assessment times than in group D. The increase of foot temperature and decrease of mean arterial blood pressure were significantly faster in group P than in group D. Although the mean pH values of the two solutions were similar, sodium and chloride ion concentrations of the diluted solution were significantly larger than those of the plain solution. We conclude that 2% lidocaine diluted with the same volume of saline produces less potent epidural blockade than commercially prepared plain 1% lidocaine.