Vasodepressor Syncope: EEG and Circulatory Changes

The common faint or vasodepressor syncope is a frequently observed disorder in which there is sudden loss of consciousness associated with a fall in arterial blood pressure. It is usually accompanied by characteristic electroencephalographic changes and by autonomic activity such as pallor, sweating, nausea, and bradycardia. Although several studies on the effects of reduction of blood pressure on cerebral circulation have been made,¹⁻³only a few have attempted to determine the critical levels of arterial pressure necessary to maintain consciousness.⁴,⁵The early studies on vasodepressor syncope employed indirect or auscultatory methods of determining arterial blood pressure, a technique which made moment-to-moment observations difficult and did not permit accurate measurement of diastolic pressure at the time of fainting.⁶,⁷More recently, Finnerty, Guillaudeau, and Fazekas,⁵using intra-arterial techniques, studied the hemodynamic changes during cerebral ischemia induced by administration of hexamethonium and head-up tilt. The present study summarizes