Alkalinization of lidocaine 2% does not influence the quality of epidural anaesthesia for elective caesarean section

This double-blind randomized study compared the effects of an epidural injection of lidocaine hydrochloride 2% (HCl) (Group 1), alkalinized lidocaine 2% (1 ml NaHCO3 per 10 ml of solution) injected either immediately (Group 2) or one hour after preparation (Group 3) in 45 parturients (n = 15 per group) scheduled for elective Caesarean section. Each patient received 16 ml of one of the three solutions. The mean pH values measured just before administration with a pH-meter PHM 64 Metrohm AG were 6.77 for the HCl lidocaine 2% solution, 7.34 for the freshly alkalinized solution and 7.35 for the solution prepared one hour before injection. The median maximal sensory level (range) observed was T3 (T8-C7), T4 (T5-C8) and T4 (T6-C6), obtained after 19 +/- 6 min, 18 +/- 8 min and 16 +/- 6 min respectively for each group. A motor block of grade 2 or 3 on the Bromage scale was obtained in 11, 10 and 14 patients respectively. No failure was observed although 3, 5, and 2 patients in Groups 1, 2, and 3 respectively required a supplementary bolus 20 min after the initial injection because of inadequate sensory level or pain at the operative site. In conclusion, this study shows that neither fresh alkalinization of 2% lidocaine nor the delay of one hour between preparation and injection of the alkalinized solution influences the onset or quality of epidural anaesthesia for elective Caesarean section.