Transient neurologic symptoms after spinal anesthesia with mepivacaine and lidocaine

Background: Spinal anesthesia with lidocaine is ideal for ambulatory surgery because of its short duration of action. However, transient neurologic symptoms (TNS) occur in 0-40% of patients, The incidence of TNS with mepivacaine, which has a similar duration of action, is unknown. Methods: Sixty ambulatory patients undergoing knee arthroscopy received spinal anesthesia in a randomized, double-blinded manner, with either 45 mg 1.5% mepivacaine or 60 mg 2% lidocaine. An L3-L4 midline approach was used with a 27-gauge Whitacre needle and a 20-gauge introducer. The local anesthetic was injected over approximately 30 s with the aperture of the Whitacre needle in a cephalad direction. Two to 4 days after operation, each patient was questioned about the development of TNS. In addition, the two groups were compared for time to regression of sensory and motor blockade and time to discharge milestones. Results: Three patients receiving lidocaine were lost to follow-up. None of the 30 patients in the mepivacaine group developed TNS, whereas 6 of 27 (22%) in the lidocaine group did (P = 0.008). Time to regression to the L5 sensory level and to complete resolution of motor block were similar in both groups. The times to discharge milestones were also comparable, Conclusions: The incidence of TNS is greater with 2% lidocaine than with 1.5% mepivacaine for patients having unilateral knee arthroscopy under spinal anesthesia. Mepivacaine seems to be a promising alternative to lidocaine for outpatient surgical procedures because of its similar duration of action. Further studies are warranted to determine the optimal dose of intrathecal mepivacaine for ambulatory surgery and the incidence of TNS with other doses and concentrations of intrathecal mepivacaine.