Topographical analysis of the EEG effects of a subconvulsive dose of lidocaine in healthy volunteers.

Abstract

The purpose of the present study was to assess the effects of intravenous lidocaine on spatial changes of electroencephalographic power and on psychomotoric status in conscious volunteers. In 11 healthy volunteers lidocaine (2-min bolus, 100 mg; 15 min infusion, 40 micrograms.kg-1.min-1) or placebo were given intravenously in a randomized, single-blinded, two-way crossover study. Haemodynamics and lidocaine plasma concentrations were measured at baseline and within a period of 30 min following bolus injection. Vigilance and emotional status were tested using visual analogue scales (VAS). Toxic CNS effects were evaluated by a questionnaire. The raw EEG (17 leads, reference Cz) and computed power spectra were continuously recorded. The chosen lidocaine dosage led to nearly constant plasma concentrations (unbound lidocaine 2.5 min and 15 min after bolus 0.36 +/- 0.14 microgram/ml and 0.30 +/- 0.06 microgram/ml, respectively [mean +/- SD]). The placebo caused no symptoms, changes in VAS-scores or EEG-parameters. Lidocaine induced pronounced subjective symptoms and significant increases in delta activity for 15 min, most dominant at the frontotemporal and occipital leads (max. +219% O1). Frontal and occipital beta 1 and beta 2 power (max. +131% and +124% at O1, respectively) was immediately increased after the bolus injection. No EEG changes occurred at central region Cz, and no interhemispheric EEG differences were noted. Theta, alpha 1, and alpha 2 power remained unchanged. The current data demonstrate simultaneous changes in psychomotoric status as well as delta and beta spectral power during lidocaine infusion. These data could be an indication that the pronounced frontotemporal and occipital EEG changes are the electroencephalographic expression of subjective sensations.