Mechanisms of formation of brain bioelectrical activity suppression patterns under adverse effects caused by neurotoxicants

Abstract

The aim of the stady wos to investigate the mechanisms of suppression of cerebral bioelectrical activity under adverse effects caused by neurotoxicants using inhalation anesthesia with sevoflurane. The research included 19 cases (male/female 12/7, aged 19—55, BMIs under 35) with intracerebral tumors. Patients were under medical observation and neurosurgical treatment. Invasive procedures were carried out under sevoflurane-based general anesthesia with a dose of anesthetic varying from 0,8 to 1,3 MAC (minimum alveolar concentration). Technologically advanced neurosurgical procedures involved neurophysiological polymodal monitoring, which included EEG and ECoG testing. Probit analysis results showed that, with cerebral cortex bioelectrical activity suppression index equal to 32±8%, nearly half the cases displayed a formation of an «outburst-suppression» type of pattern on the scalp EEG. The condition for half the cases displaying a formation of this type of periodic pattern is the suppression index equaling 58±7% on ECoG. Space-and-time evolution of suppression patterns, formed on the cerebral cortex, is the main reason for persistence of uninterrupted activity on EEG. The obtained results allow to further define principles of neurodynamics, which apply to acute intoxication with neurotoxicants. With regard to relative similarity of intoxication-induced coma cases, registration of periodic EEG patterns even with a low suppression index indicates a more severe form of cerebral insufficiency.