Cephalic kinetics of intra-arterially injected lidocaine.

The intravenous injection of 3 mg./kg. of lidocaine into the facial artery resulted in internal carotid artery blood levels between 5 and 7 microgram/ml. 15 seconds thereafter. Internal and external jugular vein blood levels exceeded 30 microgram/ml. at the same time. When the same amount of lidocaine was injected into the facial vein, carotid blood levels were less than 3 microgram/ml., peaking at 30 seconds. Concentrations of the local anesthetics in the jugular vein peaked at 15 seconds, exceeding 35 microgram/ml. The feasibility of local anesthetic drugs reaching the cerebral circulation through a retrograde pathway was indicated, suggesting that this mechanism may be the route for some of the untoward reactions observed after the injection of local anesthetics in the head and neck area.