Background: This randomized study was designed to compare discomfort caused by axillary or infraclavicular blocks in ambulatory patients. We identified which of the three block components, needle passes, local anesthetic (LA) injections, and electrical stimulations, is most painful and quantified pain intensity on a visual analog scale (VAS 0-100). We also assessed onset and quality of analgesia, adverse events and patients' acceptance.
Methods: Eighty patients were studied. In axillary group-A, four LA injections were made after stimulating median, musculocutaneous, ulnar and radial nerves. In infraclavicular group-I, the whole LA volume was injected after stimulating median or ulnar or radial nerves. Patients were ready for surgery when they had analgesia/anesthesia distal to the elbow.
Results: Median intensity of block discomfort was 22 in A group and 10 in I group (P < 0.01). There was no difference in distribution of the most painful block components between the groups. Block performance times were 4 min in I group and 7 min in A group (P < 0.01). Block onset times were 18 min in A group and 20 min in I group (NS). There was one block failure in I group. Three patients in A group and five in I group required supplementary blocks (NS). Transient adverse events occurred in 14 A-group and two I-group patients (P<0.01). Thirty-seven I-group and 33 A-group patients were satisfied with the block (NS).
Conclusions: Infraclavicular block by single injection caused less discomfort and fewer adverse events than axillary block by multiple injections. Block effectiveness, onset time and patients' acceptance were similar.