Feasibility of an infraclavicular block with a reduced volume of lidocaine with sonographic guidance.

OBJECTIVE A successful brachial plexus block requires a large volume of a local anesthetic. Sonography allows reliable deposition of the anesthetic around the cords of the brachial plexus, potentially lowering the anesthetic requirement. METHODS Fifteen sonographically guided infraclavicular blocks were performed in 14 patients with 2% carbonated lidocaine with epinephrine through a 17-gauge Tuohy needle. The amount of lidocaine injected at several points around each cord was based on satisfactory spread observed sonographically. A 19-gauge catheter was then placed with its tip between the posterior cord and axillary artery, and tip position was confirmed by observing the spread of 1 to 2 mL of injected air. Lidocaine was injected through the catheter if necessary to prolong the blocks. RESULTS Surgery was performed in all patients without general anesthesia, rescue blocks, or infiltration. A heroin user was given an additional 50 microg of fentanyl before the block. One patient required 5 mL of lidocaine through the catheter for an incomplete radial nerve block 5 minutes after initial injection. Seven patients received additional midazolam (mean, 2.5 mg) for alleviation of anxiety despite excellent blocks. The mean +/- SD volume of lidocaine for the initial block was 16.1 +/- 1.9 mL (4.2 +/- 0.9 mg/kg). In 4 patients, additional lidocaine 1 hour after an initial successful block increased the total volume to 19.5 +/- 7.1 mL (5 +/- 1.9 mg/kg). The mean times to perform the block, onset of the block, and achieving surgical anesthesia and the duration of surgery were 10.8 +/- 3.3, 2 +/- 1.3, 5.9 +/- 2.6, and 92.7 +/- 54.4 minutes, respectively. CONCLUSIONS A successful infraclavicular block in adults with 14 mL of lidocaine is feasible with the use of sonography. The reduced volume does not seem to affect the onset but shortens the duration of the block.