163 - Investigation of Autonomic Dysfunction in Acute Stroke

Abstract

This chapter investigates autonomic dysfunction in acute stroke. Autonomic investigation is performed to document clinical symptoms and prevent complications. Because the cardiac abnormalities that frequently cause death after stroke have been recognized as autonomically based, cardiovascular control is essential. Pharmacological tests have the advantage of providing autonomic information in clinically uncooperative patients. Reduced or increased heart rate (HR) and blood pressure responses after administration of drugs such as noradrenaline, tyramine, isoprenaline, clonidine, edrophonium, and atropine are indicative of sympathetic or parasympathetic dysfunction. Some simple tests, such as continuous ECG and noninvasive blood pressure monitoring as well as the assessment of norepinephrine levels appear to improve mortality rates due to heart failure after stroke. Some other methods are of limited clinical usefulness, but provide information on certain physiopathological mechanisms of complex autonomic pathways. These include spectral analysis of HR variations indicative of sympathetic/parasympathetic balance and physiological cardiovascular tests. A rational approach to autonomic investigation is to use tests that do not require patient cooperation, that are noninvasive, and that do not induce discomfort and stress during the acute phase of stroke.