Axillary block in children: single or multiple injection?

The goal of this double-blind prospective study was to compare the effect of a single injection versus multiple fractionated doses on the onset time and quality of motor and sensory block, obtained in 70 children anaesthetized with axillary block alone. The brachial plexus was identified with a peripheral nerve stimulator, and blocked with 0.5 ml.kg-1 of 1.5% lignocaine with adrenaline. In Group S (single injection), the total volume was injected after location of one nerve. In Group M (multiple fractionated doses), two nerves were located, including necessarily one nerve implicated in the surgical territory. Motor and sensory blocks were assessed according to Lanz's scale before surgery by a blinded observer. A block was considered complete if there was no feeling in at least three nerve territories at 30 min. No difference was found between groups for motor and sensory block quality. However the onset time of the block was faster after multiple fractionated doses (Group M, 25+/-7 min vs Group S, 29+/-4 min) and was faster in younger children (5-9 years: M=23+/-7 min vs S=28+/-5 min, 10-15 years: no difference). There was a significant difference in the quality of the sensory blockade of the musculocutaneous nerve: 18 versus 8 complete blocks, 10 versus 14 incomplete blocks, respectively for Group M versus Group S. No adverse effect was observed and analgesia was prolonged for more than 4 h. We can conclude that, unlike adults, fractionated doses in chilren bring no benefit to the quality of sensory and motor block. Selective block of the musculocutaneous nerve is recommended when a surgical procedure takes place in this territory.