Perivascular axillary block II: influence of injected volume of local anaesthetic on neural blockade.

Perivascular axillary blockade was performed on 150 patients with the aid of a catheter technique. Blockade failure due to injection outside the neurovascular sheath was found in 5.7% of the subject material. The patients were randomly allocated to three groups. The amount of local anaesthetic was constant in each group: 400 mg mepivacaine with adrenaline. However, the injected volume was a variable factor, namely 20, 40 or 80 ml. Sensory and motor blockade was tested 30 min after each injection. The following results were obtained: 1) Apart from the axillary, musculocutaneous and radial nerves, a high frequency of analgesia was found in all cutaneous areas (over 85%). 2) In the axillary area, improvements were found with increasing volume. 3) Analgesia in the musculocutaneous area occurred in 52% of the patients in group 1 (20 ml) and improved to 75% in group 2 (40 ml). However, no difference was found between group 2 and group 3 (80 ml). 4) Volume had no influence on analgesia in the radial area. 5) Motor blockade was intensified with decreasing volume, i.e. with an increase of concentration of local anaesthetic solution.