In this double-blind study, interscalene brachial plexus (ISBP) block was p
erformed in 11 volunteers using 10 mi of either 0.25% (n=6) or 0.5% (n=5) b
upivacaine with epinephrine 1:200 000. Diaphragmatic excursion, respiratory
function and neural function were assessed for 90 min. Our results showed
that hemidiaphragmatic excursion declined significantly after block in the
0.5% group and paradoxical movement during inspiration was more common than
in the 0.25% group. Forced vital capacity and forced expiratory volume in
1 s declined significantly in the 0.5% group (mean 74.6 (SD 13.0)% and 78.2
(19.9)% of baseline, respectively) but not in the 0.25% group. Sensory ana
esthesia in the upper limb was found consistently in both groups, although
biceps paralysis occurred earlier after 0.5% bupivacaine. We conclude that
ISBP block using 10 ml of 0.25% bupivacaine provided upper limb anaesthesia
to pinprick in C5-6 dermatomes with only occasional interference with resp
iratory function.