THE CEREBRAL HEMODYNAMIC-RESPONSE TO ELECTRICALLY-INDUCED SEIZURES INMAN

The hemodynamic response to seizure has long been a topic for discussi on in association with the neuronal damage resulting from convulsion. Electroconvulsive therapy (ECT) is an appropriate clinical model for t he investigation of the cerebral physiology of seizure. In this study, we monitored the oxygenation state of brain tissue using near infrare d (NIR) spectrophotometry, and flow velocity at the middle cerebral ar tery (MCA) using transcranial Doppler ultrasonography (tc-Doppler) in ninety cases where ECT was prescribed to patients suffering from endog enous depression. Under general anesthesia with thiopental and succiny l choline, an electrical current was applied bilaterally at the minima l energy level. Throughout the therapy, end-tidal CO2 tension was main tained at 30-35 mmHg, and the SpO(2) value was maintained above 98% by manual ventilation assistance. The total- and oxy-hemoglobin contents in the brain were reduced during the electrical shock, and then recov ered to the pre-shock value (total-hemoglobin; 44.13 +/- 12.88 s after the shock, oxy-hemoglobin; 88.62 +/- 11.69 s after the shock). Subseq uently, these values further increased beyond the preshock value. On t he other hand, the deoxy-hemoglobin content increased for 90.73 +/- 15 .88 s during and after the electrical shock, and decreased afterward. Reduction of cytochrome alpha alpha 3 began 3.04 +/- 0.51 s after the electrical shock, and this was reoxygenated at 171.88 +/- 12.95 s afte r the shock. The flow velocity at MCA was drastically increased (mean flow velocity; from 44.8 +/- 1.2 cm/s to 106.4 +/- 7.5 cm/s) 1 min aft er the shock and returned to the pre-shock level after 10 min. From th ese observations, it was suggested that electrical shock provoked a co ntraction of arterial wall smooth muscle, and depolarized the synaptic terminal, which triggered neurotransmitter release and sympathetic ac tivation. This depolarization also caused an abrupt increase in the en ergy consumption of neurons and the cytochrome alpha alpha 3 was tempo rarily reduced. However, this imbalance in energy supply and consumpti on was improved by the subsequent hyperdynamic blood circulation and b y suppression of neuronal activity at the postictal phase. It was conc luded that electrically induced seizure provokes a temporary imbalance in energy consumption and supply, and that these new non-invasive mon itors are useful in the study of the physiological events that occur i n the nervous system in man.