Journal of neurosurgical anesthesiology
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J Neurosurg Anesthesiol · Jul 1998
Comparative StudyThe effects of exogenous epinephrine on a convulsive dose of lidocaine: relationship with cerebral circulation.
In order to understand why exogenous epinephrine decreases the convulsive dose of lidocaine, the authors investigated cerebral circulation and plasma lidocaine concentrations in Wistar rats under general anesthesia. In the first experiment, baseline evaluations of each rat's electroencephalogram (EEG), mean arterial pressure (MAP), regional cerebral blood flow (r-CBF), cerebrospinal fluid (CSF) pressure, and cerebral perfusion pressure (CPP) were made. The rats were then assigned to one of three groups: Group L (n=6) received intravenous lidocaine (5 mg/kg/min); Group LE (n=6) received intravenous lidocaine (5 mg/kg/min) and epinephrine (2.5 kg/kg/min); and Group E (n=5) received intravenous epinephrine (2.5 microg/kg/min). ⋯ Neither decreased PtO2 nor extravasation of EB was observed in rats treated with epinephrine and lidocaine, excluding cerebral ischemia and BBB breakdown from possible mechanisms by which epinephrine decreased the convulsive dose of lidocaine. None of the rats in Group E exhibited EEG findings suggestive of a preconvulsive state, ruling out a convulsive effect of epinephrine itself. The results suggest that an increase in lidocaine supply to the brain caused by increased CBF causes the low cumulative dose of lidocaine at the onset of convulsion in rats given lidocaine plus epinephrine.