Coma

: A state of deep unarousable unconsciousness. Coma may occur as the result of numerous causes including head trauma, diseases such as diabetes, poisoning, etc.

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1. A state of profound unconsciousness from which one cannot be roused; may be due to the action of an ingested toxic substance or of one formed in the body, to trauma, or to disease. [G. koma, deep sleep, trance] 2. An aberration of spherical lenses; occurring in cases of oblique incidence ( e.g., the image of a point becomes comet-shaped). [G. kome, hair] 3. SYN: c. aberration.

- delayed c. after hypoxia c. that develops a few days to 3 weeks after an acute hypoxic insult; the latter was usually severe enough to cause an initial bout of c., which cleared, and was followed by a transient interval of apparent normality. SYN: severe postanoxic encephalopathy.

- diabetic c. c. that develops in severe and inadequately treated cases of diabetes mellitus and is commonly fatal, unless appropriate therapy is instituted promptly; results from reduced oxidative metabolism of the central nervous system that, in turn, stems from severe ketoacidosis and possibly also from the histotoxic action of the ketone bodies and disturbances in water and electrolyte balance. SYN: Kussmaul c..

- hepatic c. c. that occurs with advanced hepatic insufficiency and portal-systemic shunts, caused by elevated blood ammonia levels; characteristic findings include asterixis in the precoma stage and paroxysms of bilaterally synchronous triphasic waves on EEG examination.

- hyperosmolar (hyperglycemic) nonketotic c. (hi′per-os-mo-lar) a complication seen in diabetes mellitus in which very marked hyperglycemia occurs (such as levels over 800 mg/dL) causing osmotic shifts in water in brain cells and resulting in c.. It can be fatal or lead to permanent neurologic damage. Ketoacidosis does not occur in these cases. SYN: nonketotic hyperglycemia.

- hypoglycemic c. a metabolic encephalopathy caused by hypoglycemia; usually seen in diabetics, and due to exogenous insulin excess.

- hypoventilation c. c. seen with advanced lung failure and resultant hypoventilation. SYN: CO₂ narcosis, hypoxic-hypercarbic encephalopathy, pulmonary encephalopathy.

- Kussmaul c. SYN: diabetic c..

- metabolic c. c. resulting from diffuse failure of neuronal metabolism, caused by such abnormalities as intrinsic disorders of neuron or glial cell metabolism, or extracerebral disorders that produce intoxication or electrolyte imbalances.

- thyrotoxic c. c. preceding death in severe hyperthyroidism, as in thyroid storm or thyrotoxic crisis.

- trance c. SYN: lethargic hypnosis.

- uremic c. a metabolic encephalopathy caused by renal failure.

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Committee on Medical Aspects [food and nutrition]

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co·ma 'kō-mə n a state of profound unconsciousness caused by disease, injury, or poison

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n.

a state of unrousable unconsciousness. See also Glasgow scoring system.

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co·ma (koґmə) [L., from Gr. kōma] 1. a state of unconsciousness from which the patient cannot be aroused, even by powerful stimulation; called also exanimation. See also consciousness. 2. the optical aberration produced when an image is received upon a screen which is not exactly at right angles to the line of propagation of the incident light.