Plasma concentrations of lidocaine after proximal and peripheral facial nerve block

We compared plasma levels of lidocaine after the administration of proximal and peripheral blocks of the facial nerve in 30 cataract patients to evaluate the risk of systemic toxicity after both procedures. We performed the two block techniques with 5 ml 1% lidocaine solution plus (1:20,000) naphazoline nitrate as follows: the proximal block, at the dorsal rim of the mandible and the peripheral block, by subcutaneous infiltration of the lids. After the administration of the proximal block, mean plasma concentrations of lidocaine increased continuously for 15 min, whereas after the peripheral block they peaked within 12 min. Mean plasma concentrations were significantly lower following the proximal facial block than after the peripheral block of the facial nerve's terminal branches (P = 0.008-0.039, Wilcoxon test). In all patients, plasma concentration of lidocaine were below toxic levels.