[Comparison of carbonated lidocaine and mepivacaine in epidural anesthesia]

OBJECTIVE. To compare carbonated mepivacaine to carbonated lidocaine in epidural anaesthesia. DESIGN. Nonrandomised control trial. SETTING. University Hospital. PATIENTS. Forty patients undergoing epidural anaesthesia for orthopaedic surgery. METHODS. Epidural anaesthesia at the fourth lumbar interspace, administering either carbonated mepivacaine 20 ml (group M, 20 patients) or carbonated lidocaine 20 ml (group L, 20 patients). Parameters recorded: onset of sensory block (time required to reach L1 and time required to reach the upper level), cranial spread of analgesia (number of dermatomes), duration of block (time between achievement of maximum spread of analgesia and regression of sensory block by two dermatomes) and motor block (Bromage score). RESULTS. No statistically significant differences have been found between group M and group L in the time required to reach L1 (means and standard deviations 6.3 +/- 3.8 and 6.5 +/- 2.1 minutes, respectively), in the time required to reach the upper level of analgesia (means and standard deviations 14.3 +/- 4.2 and 16.5 +/- 3.5 minutes, respectively), in the cranial spread of analgesia (means and standard deviations 7.1 +/- 3.4 and 7.6 +/- 2.7 dermatomes, respectively) and in the degree of motor block (means and standard deviations 1.5 +/- 0.8 and 1.1 +/- 0.8, respectively). Group M exhibited a much higher duration of sensory block, compared to group L (means and standard deviations 91.6 +/- 20.2 and 58.8 +/- 23.4 minutes, respectively, p < 0.001). CONCLUSIONS. Carbonated mepivacaine is more indicated than carbonated lidocaine in epidural anaesthesia when a high duration of sensory block is desired.