Bupivacaine and prilocaine in intravenous regional anaesthesia

Six volunteers underwent intravenous regional anaesthesia of the non-dominant arm on four occasions using two equipotent doses of bupivacaine and prilocaine, administered in a randomised double-blind sequence. Equipotent doses produced similar degrees of motor and sensory blockade. Bupivacaine produced more rapid motor power loss and delayed motor recovery (p less than 0.01). Prilocaine produced more prolonged objective blockade following tourniquet release (p less than 0.01), although this was not clinically useful, and bupivacaine led to a marked prolongation of subjective blockade (p less than 0.01). Increase of dose with both drugs gave more rapid and complete sensory and motor blockade and delayed recovery (p less than 0.05). This was, however, associated with more marked toxicity. It is suggested that in intravenous regional anaesthesia there are no clinical differences between the drugs in equipotent solutions, and that the lower concentrations are the appropriate ones for standard use.