Selective radial or ulnar nerve localization in triple-injection technique of axillary beachial plexus block : success of sensor and motor block

Selective ulnar nerve localization is not essential in a four-injection technique of axillary brachial plexus block. The effectiveness of selective radial and ulnar nerve localization in triple-injection technique is still of interest. The aim of our study was to determine the success rate and the differences in motor and sensor block after selective radial and ulnar nerve localization in this technique. Sixty patients (female 32, male 28 ; 21-81 old ; ASA I-IV) were randomly divided in the two equal groups and included in prospective, double-blind study. Nerve detection was performed by Simuplex® ; HNS 11 at 0.5 mA, 2Hz and 0.1 ms. In the bough group, the median and musculocutaneus nerve were localized above the axillary artery and separately injected with 15 and 5 ml mixture of local anaesthetics (1:1 ; 0.5% levibupivacaine and 2% lidocaine). In Group R, radial and in Group U, ulnar nerve was located inferior to the artery and injected with 15 ml of the same local anaesthetic mixture. Motor block was determined by the modified Bromage scale. Sensor block was assessed in 10 min intervals by pinprick. Data was analysed by ANOVA and Fisher exact test. The success rate of the block was higher after selective radial nerve stimulation (96% vs. 88%) in the significant shorter time of effective block analgesia (18+/-4 vs. 34+/-4min) and anaesthesia (26+/-3 vs. 41+/-3 min)(P=0.000). Complete motor (88% vr.43% in Group U) and satisfactory sensor block (C6 99%-C8 85% vs. C6 48%-C8 78% in Group U) was achieved faster in Group R already at the time of block analgesia (P=0.005). Selective radial nerve localization in triple-injection technique of axillary brachial plexus block allows higher block effectiveness and better motor and sensor block already at the time of block analgesia to compare with selective ulnar nerve localization.