Dysautonomia and It’s Perioperative Implications

Abstract

Many bodily functions proceed without any conscious supervision from our central nervous system (CNS). For example, we don’t have to remember to digest our food after a meal, or sweat when too warm. These functions are controlled subconsciously, with a degree of automaticity, by a branch of the nervous system - The Autonomic Nervous system (ANS). The ANS can thus be thought of as the regulatory system that partly or wholly controls most of the body’s organ systems and homeostatic mechanisms. In general, ANS effects are involuntary, relatively rapid, neuronal reflexes. Dysautonomia (or autonomic dysfunction, autonomic neuropathy) refers to an abnormality of function of the autonomic nervous system. There are two divisions of the autonomic nervous system: the sympathetic and the parasympathetic. Although the latter occasionally may be involved, abnormal function of the sympathetic division produces the most striking symptoms of dysautonomic syndromes. The term orthostatic hypotension is often used as a synonym for dysautonomia. It is the most dramatic of the symptoms and is the one that most often brings the patient to the physician, but it is not an adequate description of the full dysautonomic syndrome. Dysautonomia is not a single disease process. The autonomic nervous system may undergo injury as part of several different degenerative neurologic diseases. These are the primary dysautonomias. There are also non-neurologic systemic illnesses of a variety of causes in which injury to the autonomic nervous system may occur and become a predominant component. These are the secondary dysautonomias. Finally, side effects of drugs are often manifested as abnormalities of function of the autonomic nervous system, producing an iatrogenic form of dysautonomia. Dysautonomia does not produce unique symptoms. The patient's individual complaints can each be part of another disease process. It is the set of symptoms, taken together, that suggests that a dysautonomic state is present. In obtaining the history, therefore, three tasks must be accomplished. The physician must: 1) Develop a sufficient body of information to establish that a dysautonomic syndrome actually exists 2) Distinguish the secondary dysautonomias, including drug side effects, many of which will improve or disappear when the causative problem is treated, from the primary dysautonomias for which there is only symptomatic relief. 3) Distinguish among the several forms of primary dysautonomia, since these have different natural histories and prognoses. The first objective of management of a patient with autonomic neuropathy is to administer specific treatment for treatable conditions. For example, if an autoimmune neuropathy is present, attempted management with immunomodulatory therapies should be considered. If diabetes mellitus is the underlying cause, strict control of blood glucose to prevent further worsening is essential. However, many of the autonomic neuropathies are not treatable with specific therapy. In these cases, symptomatic therapy becomes vitally important. Many anaesthetic procedures and drugs used in anaesthetic practice have a direct influence on the autonomic nervous system. It is therefore essential that the anaesthetist should have a basic understanding of its structure and function.