Canadian Journal of Anesthesia, Vol 45, 122-129, Copyright © 1998 by Canadian Anesthesiologists' Society

ARTICLES

Minimum effective anaesthetic concentration of hyperbaric lidocaine for spinal anaesthesia

PW Peng, VW Chan and A Perlas
Department of Anaesthesia, Toronto and Mount Sinai Hospital, University of Toronto, Ontario, Canada.

PURPOSE: Minimum effective anaesthetic concentration (MEAC) of lidocaine for spinal anaesthesia, defined as the concentration at which a spinal anaesthetic agent produces surgical anaesthesia within 20 min of administration in 50% of patients, was determined in a randomised, double-blind study in young patients undergoing knee and ankle surgery. METHODS: Using the combined spinal-epidural technique, 48 or 72 mg hyperbaric lidocaine containing dextrose 7.5% was administered intrathecally to 43 patients at concentrations ranging from 0.2-0.9%. The choice of lidocaine concentration was determined by Dixon's up-and-down method. Complete anaesthesia was defined as: (1) pinprick anaesthesia at or higher than T12, (2) anaesthesia to transcutaneous tetanic electric stimulation (50 Hz at 60 mA for five seconds) in the knees and (3) complete leg paralysis; all occurring in both lower extremities within 20 min. Epidural anaesthesia was initiated if anaesthesia was incomplete. RESULTS: In the 48 mg group, MEAC was 0.54% (95% CI-0.21-0.87). Anaesthetic effect was variable with mean duration of anaesthesia of 29 min (range: 20-50 min) and maximum pinprick sensory level ranging from T2-T10. In the 72 mg group, successful anaesthesia was achieved consistently at a concentration of 0.3%, i.e., MEAC was < 0.3%. Mean duration of complete anaesthesia was 46 min (range: 30-60 min) with maximum sensory level from T3-T8. DISCUSSION: Spinal anaesthesia can be accomplished with very dilute lidocaine solutions (< 0.9%). The value of MEAC is dose-dependent, i.e., complete anaesthesia can be accomplished with lower concentrations by increasing the dose of spinal anaesthetic administered.

This article has been cited by other articles:

				M. Camorcia, G. Capogna, G. Lyons, and M. O. Columb The Relative Motor Blocking Potencies of Intrathecal Ropivacaine: Effects of Concentration Anesth. Analg., June 1, 2004; 98(6): 1779 - 1782. [Abstract] [Full Text] [PDF]

				N. Rawal Analgesia for day-case surgery Br. J. Anaesth., July 1, 2001; 87(1): 73 - 87. [Abstract] [Full Text] [PDF]

				A. Casati, G. Fanelli, P. Beccaria, L. Magistris, A. Albertin, and G. Torri The Effects of Single or Multiple Injections on the Volume of 0.5% Ropivacaine Required for Femoral Nerve Blockade Anesth. Analg., July 1, 2001; 93(1): 183 - 186. [Abstract] [Full Text] [PDF]

				A. Casati, G. Fanelli, L. Magistris, P. Beccaria, M. Berti, and G. Torri Minimum Local Anesthetic Volume Blocking the Femoral Nerve in 50% of Cases: A Double-Blinded Comparison Between 0.5% Ropivacaine and 0.5% Bupivacaine Anesth. Analg., January 1, 2001; 92(1): 205 - 208. [Abstract] [Full Text] [PDF]

				V. W. S. Chan, P. Peng, H. Chinyanga, S. Lazarou, J. Weinbren, and Z. Kaszas Determining Minimum Effective Anesthetic Concentration of Hyperbaric Bupivacaine for Spinal Anesthesia Anesth. Analg., May 1, 2000; 90(5): 1135 - 1140. [Abstract] [Full Text] [PDF]