Autonomic Dysfunction and Hypotension.

The autonomic nervous system, especially through the cranial parasympathetic and lumbosacral sympathetic outflow, is closely involved in the beat-to-beat control of systemic blood pressure, heart rate, and the regional blood supply to skeletal muscle and vital organs. It is of major importance in ensuring adequate tissue perfusion, in maintaining supplies of oxygen and nutrients, and in transporting metabolic end-products in response to the demands of varying situations. It accomplishes these actions through a complex system of pathways that involves the brain and spinal cord, preganglionic and postganglionic pathways, and synapses at the target organs; the immense flexibility and capability of the autonomic nervous system are dependent on intricate pathways that may be damaged in a variety of conditions that affect one or more sites with the brain, spinal cord, or periphery1 (Fig. 88.1). A key component is the baroreflex pathway, an exquisitely sensitive mechanism that provides beat-bybeat blood pressure control (Fig. 88.2). This chapter discusses the classification of autonomic disorders that affect the cardiovascular system, and describes the main clinical manifestations, tests of autonomic dysfunction, and features of key major autonomic disorders. [ABSTRACT FROM AUTHOR]