Blood flow in the upper limb during brachial plexus anaesthesia.

Changes in finger blood flow, arm blood flow and cardiac output were measured using electrical impedance plethysmography in 20 patients after brachial plexus anaesthesia. The anaesthetic solution used in all patients was 1% lignocaine with adrenaline 1:200,000. Significant increases in cardiac output and blood flow to the unanaesthetised arm were observed immediately after anaesthesia had become effective. A highly significant increase in the blood flow to fingers of the blocked hand was observed throughout the period of anaesthesia but there was no overall increase in the blood flow to the arm. It is suggested that the adrenaline contained in the local anaesthetic solution increased the cardiac output and caused arterial vasoconstriction at the site of injection.