The effect of alkalinisation of lignocaine on axillary brachial plexus anaesthesia.

Alkalinisation of local anaesthetic drugs is a controversial technique for improving regional blockade. Forty-two patients scheduled for upper limb surgery received axillary brachial plexus anaesthesia using a cannula technique. Patients were randomly allocated to receive either lignocaine 1.5% with 1 in 200,000 adrenaline (pH = 4.2) or lignocaine 1.5% with 1 in 200,000 adrenaline (pH = 7.2). There was no significant difference in the incidence of satisfactory blockade or distribution of anaesthesia between the two groups. The percentage of patients with complete anaesthesia at 10, 20 and 30 min following injection was significantly increased in the alkalinized group with regard to the ulnar and median nerves, and the median cutaneous nerve of the arm (p < 0.05). In the alkalinized group, there was a significant reduction in the time to useful anaesthesia and a reduced requirement for adjuvants (p < 0.05). There was no effect on the duration of anaesthesia.