Clinical evaluation of the lateral sagittal infraclavicular block developed by MRI studies.

BACKGROUND AND OBJECTIVES: Lateral sagittal infraclavicular block by single injection has a faster performance time and causes less discomfort than does axillary block by multiple injections. This prospective, descriptive, multicenter study assessed block effectiveness, onset time, and incidence of adverse events and verified the noninvasive measurements from magnetic resonance imaging (MRI).

METHODS: One hundred sixty patients were anesthetized by use of the lateral sagittal infraclavicular block and following the MRI recommendations for needle insertion. Each patient received a mixture that contained equal volumes of ropivacaine 7.5 mg/mL and mepivacaine 20 mg/mL with epinephrine 5 mug/mL, in a total amount that corresponded to 0.5 mL/kg (minimum 30 mL, maximum 50 mL). Block effectiveness (analgesia or anesthesia of all 5 nerves below the elbow after 30 minutes), performance and onset times, needle insertion depth and dorsal angle, twitch type, analgesia of the individual nerves, and incidence of adverse events and complications, as well as patient's acceptance, were recorded.

RESULTS: One hundred forty-three patients (91%) had successful blocks, 12 patients required supplementary nerve blocks in the axilla, 3 patients had total failures of blocks (no forearm analgesia at all), and 2 patients were excluded from the assessments. Median block performance time was 4 minutes (range, 2-10 minutes) and the onset time 20 minutes (range, 10-50 minutes). Plexus nerves were found at a mean depth of 53 mm +/- 10 mm and the needle dorsal angle was 23 degrees +/- 9 degrees . Four patients experienced painful paresthesias and 3 patients had accidental punctures of axillary vessels. Signs or symptoms of complications (hematoma, local anesthetic toxicity, pneumothorax, or neuropraxias) were not observed. Only 3 patients would prefer general anesthesia in the future. Finger/wrist extension may be an optimal twitch response (P = .14).

CONCLUSIONS: Block effectiveness (91%) and onset time (20 minutes) were satisfactory and comparable to the vertical paracoracoid approach. The low rate of axillary vessel punctures (2%) may be the most important advantage of this block. The needle insertion depth measurements confirmed the MRI findings, but the dorsal angle was steeper than predicted.