The Electrocortical Effects of Enflurane: Experiment and Theory

Overview

Journal Anesth Analg

Specialty Anesthesiology

Date 2009 Sep 19

PMID 19762755

Citations 12

Authors

James W Sleigh

Jeannette A Vizuete

Logan Voss

Alistair Steyn-Ross

Moira Steyn-Ross

Charles J Marcuccilli

Anthony G Hudetz

Affiliations

Soon will be listed here.

Abstract

Background: High concentrations of enflurane will induce a characteristic electroencephalogram pattern consisting of periods of suppression alternating with large short paroxysmal epileptiform discharges (PEDs). In this study, we compared a theoretical computer model of this activity with real local field potential (LFP) data obtained from anesthetized rats.

Methods: After implantation of a high-density 8 x 8 electrode array in the visual cortex, the patterns of LFP and multiunit spike activity were recorded in rats during 0.5, 1.0, 1.5, and 2.0 minimum alveolar anesthetic concentration (MAC) enflurane anesthesia. These recordings were compared with computer simulations from a mean field model of neocortical dynamics. The neuronal effect of increasing enflurane concentration was simulated by prolonging the decay time constant of the inhibitory postsynaptic potential (IPSP). The amplitude of the excitatory postsynaptic potential (EPSP) was modulated, inverse to the neocortical firing rate.

Results: In the anesthetized rats, increasing enflurane concentrations consistently caused the appearance of suppression pattern (>1.5 MAC) in the LFP recordings. The mean rate of multiunit spike activity decreased from 2.54/s (0.5 MAC) to 0.19/s (2.0 MAC). At high MAC, the majority of the multiunit action potential events became synchronous with the PED. In the theoretical model, prolongation of the IPSP decay time and activity-dependent EPSP modulation resulted in output that was similar in morphology to that obtained from the experimental data. The propensity for rhythmic seizure-like activity in the model could be determined by analysis of the eigenvalues of the equations.

Conclusion: It is possible to use a mean field theory of neocortical dynamics to replicate the PED pattern observed in LFPs in rats under enflurane anesthesia. This pattern requires a combination of a moderately increased total area under the IPSP, prolonged IPSP decay time, and also activity-dependent modulation of EPSP amplitude.

Citing Articles

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Contributions of synaptic and astrocyte physiology to the anaesthetised encephalogram revealed using a computational model.

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Frontal-temporal functional connectivity of EEG signal by standardized permutation mutual information during anesthesia.

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Kadam S, DAmbrosio R, Duveau V, Roucard C, Garcia-Cairasco N, Ikeda A Epilepsia. 2017; 58 Suppl 4:10-27.

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