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Axillary nerve block describes the reversible loss of sensation of the axillary nerve territory by infusing local anaesthetic.
The axillary artery is palpated at its most proximal point in the axilla along the line of the humerus. A few millilitres of 1% lignocaine is injected to anaesthetise the skin at this point. A tourniquet is applied distal to this site and is inflated in order to ensure that local anaesthetic tracks up the brachial plexus.
After a few minutes, a needle is passed slightly superior to the axillary artery. Paraesthesia is felt on progressing to the depth of the axillary nerve. Aspirate to ensure the that the needle is not in the vessel. The local anaesthetic is then injected: up to 40 ml of 1% lignocaine with adrenaline. The cuff is deflated a few minutes later.
Axillary nerve block can be commenced prior to the correction of fractures distally in the arm. However, the procedure is fraught with danger: neuropraxia, intravascular injection and the dissemination of malignancy are all possible. Axillary blocks are poor for above-elbow procedures.