Circulatory and respiratory effects of lidocaine administered into the rat maxillofacial circulation

The inadvertent intra-arterial administration of local anesthetics is a serious hazard of oral operations. For this reason, the circulatory and respiratory consequences of introducing lidocaine into the maxillofacial (MF) arterial circulation were examined in anesthetized rats. Lidocaine boluses of 0.3 to 6.0 mg/kg increased infusion pressure (IP) by up to 85%, signifying considerable local vasoconstriction; following a 6.0 mg/kg injection, heart rate (HR) remained unaffected, mean blood pressure (BP) increased by 5%, and respiratory rate (RR) decreased by 20%. Infusions of 50 or 150 micrograms/kg/min for 30 minutes had no effect on the preceding parameters, but within 15 minutes of infusing lidocaine at 600 micrograms/kg/min, IP increased by 97% and RR decreased by 31%; BP and HR remained unaffected. It was concluded that the main consequences of administering plain lidocaine at the aforementioned doses into the rat MF arterial bed were considerable local vasoconstriction and a large reduction in respiratory rate. Heart rate remained unaffected by lidocaine; neither it nor blood pressure is a reliable indicator of approaching systemic toxicity.