POSTERIOR APPROACH TO THE LUMBAR PLEXUS COMBINED WITH A SCIATIC-NERVEBLOCK USING LIDOCAINE

A combination of lumbar plexus block, by a posterior technique, and sc iatic nerve block can be a useful technique for outpatient anaesthesia . The purpose of this study was to examine the clinical characteristic s of these blocks using lidocaine and to measure the serum lidocaine c oncentrations. Forty-five patients, undergoing lower extremity surgery , were studied. Sciatic nerve and lumbar plexus blocks were made with lidocaine, 680 mg with adrenaline 0.3 mg. For each patient the followi ng data were collected: weight, age, sex, site of surgery, time to per form each block, needle depth, speed of onset of the sensory and motor blocks in the territories of the sciatic, femoral, obturator and late ral cutaneous (sensory) nerves and postoperative analgesic requirement s. Lidocaine serum concentrations were measured in ten of these patien ts at 0, 2, 5, 10, 30, 60, 90 and 120 min after the second block. Anal gesia was complete in 88% (40/45) of the patients. The remaining five patients needed analgesics (fentanyl 150 mu g or less). Despite the hi gh dose of lidocaine, the serum concentrations were within safe limits (mean +/- SD) (CUAX = 3.66 +/- 2.21 mu g . ml(-1)). Only one patient had a serum concentration > 5 mu g . ml(-1) (C-MAX = 9.54 mu g . ml(-1 )). This was associated with a contra-lateral extension of the block. We conclude that this combination of blocks is a valuable alternative for unilateral lower extremity anaesthesia. However, clinicians must b e aware of the implications of a contra-lateral extension of the block .