Lidocaine and bupivacaine mixtures for epidural blockade

In a prospective double-blind clinical study, single-dose lumbar epidural blockade was instituted in 60 healthy patients undergoing lower abdominal surgery. Patients were randomly assigned to one of five groups. Each group received treatment with a different local anesthetic solution containing 1:200,000 epinephrine. Local anesthetic solutions used were 0.5 per cent bupivacaine HCl, 2 per cent lidocaine HCl, and lidocaine-bupivacaine mixtures in the ratios of 1:3, 1:1 or 3:1 by volume. Onset and complete spread of sensory blockade were similar in all five groups. Time to regression to two segments of partial and complete sensory blockade was positively correlated (P less than 0.05) with increasing dose of bupivacaine in the solutions and ranged from 84 min (partial) and 70 min (complete) for lidocaine, to 128 min (partial) and 101 min (complete) for bupivacaine. Using skin temperature as a criterion of sympathetic blockade, all three mixtures demonstrated a duration of action intermediate between the two single drugs, lidocaine (124 +/- 13 min) and bupivacaine (286 +/- 32 min). Onset of complete motor blockade was fastest and the degree of motor blockade was most profound with the mixture containing equal proportions of lidocaine and bupivacaine. Pharmacokinetics of individual drugs were unaltered in any of the mixtures.