Variations in Visual Evoked Potentials under Anesthesia

Abstract

Publisher Summary This chapter discusses variations in visual evoked potentials under anesthesia. Even though the brain is the target organ of anesthetics, relatively little is known about brain function under anesthesia, and the means of monitoring it are meager. In contrast, abundant research on the heart and lungs, which are secondarily affected by anesthetics, has provided the basis for aggressive, invasive monitoring of circulation, and ventilation. The electroencephalography (EEG) and power spectrum analysis of the EEG have been used to monitor the effects of anesthetics, anesthetic concentration and the patient's response to surgical stimulation, however, the EEG has not been a rewarding tool in these applications since it represents the overall activity of the brain and lacks specificity. Sensory evoked responses may provide a better index of brain function under anesthesia since the ultimate aim of anesthesia is to prevent central nervous system (CNS) registration of sensory stimulation. Visual evoked responses (VERs) are obtained in an awake condition prior to medication and at varying concentrations of halothane in oxygen during surgery. All patients received thiopental induction, followed by anesthetic maintenance with halothane in oxygen, paralysis, and endotracheal intubation.