Perivascular axillary block VI: the distribution of gelatine solution injected into the axillary neurovascular sheath of cadavers.

Axillary perivascular injection of 50 ml blue-stained gelatine was made in 20 cadavers, and a total dissection of the axilla was performed. The distribution of injected gelatine and the contact between nerves and gelatine were examined on cross-sections of the neurovascular bundle. The spread of gelatine was characterized by: restriction of gelatine to the neurovascular bundle, an upper border of the gelatine which was constantly found to be proximal to the coracoid process, and bulging of the gelatine towards the medial part of the axillary space. Cross-sections of the neurovascular bundle showed the nerves and vessels to be located in the periphery of the gelatine and in close contact with the lateral wall of the axillary space. The median and the ulnar nerves were in all dissections found to be in direct contact with the gelatine, whereas the radial, the musculocutaneous, and the axillary nerves did not always have direct contact with the gelatine. Abduction of the arm to 90 degrees brings the stretched neurovascular bundle close to the lateral wall of the axilla and this compromises perivascular circumferential spread of the injected gelatine. On the basis of the present investigation, it is hypothesized that insufficient circumferential spread is the cause of incomplete axillary blockades, and the perivascular injection of local anaesthetic should consequently be made with the arm along the side of the body.