The relationship between regional blood flow and absorption of lignocaine

With the increasing application of certain surgical procedures to 'day surgery' cases, there has been greater utilization of local anaesthetic agents. Such procedures are undertaken using single infiltration dosage recommendations for lignocaine, both with and without adrenaline. The present paper describes results obtained from a sheep model that considers the role of the regional blood flow of the injected site as a determinant of lignocaine absorption and resultant pharmacokinetics. The peak concentration of lignocaine in plasma following administration to two selected sites of different vascularity (as determined by a technetium99 washout method), as well as the effect of concomitant adrenaline administration, was shown to correlate with the regional blood flow to the site (rs = 0.73, P = 0.008). Extrapolating these animal data to the clinical situation suggests that larger dosages of lignocaine could be used safely for infiltration anaesthesia in regions of poor regional blood flow without posing a threat of lignocaine-induced toxicity, and that the current dosage recommendations could be modified in respect of the regional blood flow of the particular site to be infiltrated.