This is an intravenous regional anaesthesia / analgesia of the arm used for minor surgery and the manipulation of fractures, e.g. Colles'.
A cannula is inserted intravenously into the limb on which the procedure is to be performed. A double cuff is placed around the proximal part of the arm. The limb is raised to promote exsanguination: a rubber bandage tightly applied from distally to proximally can facilitate this cause. The upper cuff is then inflated to 250 mmHg in order to prevent even arterial flow.
20-40 millilitres of local anaesthetic - depending on the location of the cuff - is then injected into the cannula: 0.5% prilocaine is the drug of choice because it is less cardiotoxic than alternatives; maximum dosage is 3mg/Kg. Approximately 10 minutes later the anaesthetic should have started to work and pain-free procedures can be carried out on the arm. 20 minutes after the injection of local anaesthetic the lower cuff is inflated past arterial pressure and the upper cuff is then deflated. This is to prevent the pain of occlusion in the region of the upper cuff where the local anaesthetic has a relatively minimal action.
On releasing the upper cuff, there is the danger of a large bolus of local anaesthetic entering the systemic circulation. Fitting is an uncommon sequel and in frail patients this may be a sufficient risk to prevent a Bier's block in favour of general anaesthesia.
All tourniquets should be released after a maximum of one-and-a-half hours.
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