COMA. - A profound state of unconsciousness (from Gk. κολυμβίω = I sleep) characterized by muscular relaxation, abolition of sensation, and loss of consciousness, while the conditions of respiration, circulation, and thermoregulation remain nearly unchanged. It is produced by various causes: disturbances in carbohydrate metabolism (hypoglycemic and diabetic coma), accumulation in the blood of toxic metabolic substances (uremic coma, hepatic coma), severe trauma, and circulatory alterations in the nervous centers due to vascular spasms or hemorrhages (cf. APOPLESSIA).
From very mild forms, with simple stupor in which consciousness can easily be aroused by more or less strong stimuli (vigil coma), one progresses to the most severe forms with fully developed symptomatology: paralysis of reflexes, slow and stertorous breathing, difficulty in swallowing, and complete loss of consciousness. In severe coma, the individual must be considered as being deprived of means to interact with the external world, incapable of feeling or willing. Coma may regress, and the individual may regain consciousness and activity if the cause producing this state is reparable and overcome.
Giuseppe de Ninno