Please confirm that an ethics committee approval has been applied for or granted: Not relevant

Background and Aims Upper extremity surgical procedures distal to the elbow can be performed under axillary brachial plexus block. Using ultrasonography, the block can be executed in two ways – perineural (PN) and perivascular (PV). A prospective, trust-based clinical audit was designed to observe and compare these two methods. The primary outcome of the study was the time to perform the nerve block, which was defined as the time from probe placement to withdrawal of needle. The secondary outcomes were the block success rate, incidence of any complications, and onset of sensory and motor anaesthesia in the respective nerve divisions.

Methods Findings were compared in 50 patients scheduled to undergo orthopedic surgeries distal to the elbow, under axillary brachial plexus block only In PN group, local anaesthetic was deposited individually around four nerves. In PV technique, a single injection of local anaesthetic was performed at 6 ‘o’ clock position with respect to the axillary artery, with the aim to surround the artery with drug.

Results PV group had a shorter procedural time of 7.64 minutes, whereas the PN group had a mean time of 10.56 minutes. PN group took longer to achieve motor anaesthesia (19.52 minutes). A higher rate of successful block was observed in the PV group (92%) than the PN group(84%). One vascular puncture was observed in PV group.

Conclusions PV technique can be used with a higher success rate in large volume centres due to shorter performance times, especially in population with complex anatomy where identification of all four nerves is difficult.