Coma
Coma is a state of unconsciousness where there is no response to vigorous external stimulus. There are a number of causes, including trauma from any head injury causing brain damage, any prolonged episode of interference of the oxygen supply to the brain (such as in near drowning), bleeding from aneurysms or arterio-venous malformations (see blood and ciculation in the chest cavity section) in the blood supply to the brain, raised pressure due to a tumour or blockage of the drainage of the CSF (see raised intra-cranial pressure), metabolic disturbances in the levels of any of the salts such as sodium or calcium in the circulation, extremes in the level (too high or too low) of blood sugar, severe kidney or liver failure, or drug overdose (including alcohol in the experimenting adolescent). The management is that of the underlying cause, where this is possible: raised intra-cranial pressure can be reduced, metabolic disturbance corrected, organ failure (sometimes) treated, and some drug effects reversed. Irreversible brain damage is, unfortunately, currently irreversible, and usually due to trauma, bleeding or brain death through oxygen starvation.
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