Effects of carbon dioxide and epinephrine on serum levels of lidocaine after epidural anaesthesia.

Carbonated lidocaine is believed to penetrate membranes more rapidly than its hydrochloride salt and could possibly cause higher serum levels. To compare serum levels, arterial blood samples drawn at intervals were analyzed in a group of 18 patients under epidural anaesthesia with equivalent doses of lidocaine hydrochloride and lidocaine hydrocarbonate, with and without epinephrine. Results show that serum levels were significantly higher when lidocaine hydrocarbonate was used for epidural analgesia.