Coma is a term that is used to describe a state of unconsciousness from which a person cannot be aroused.
What is going on in the body?
A person in a coma is unable to respond to the environment. He or she cannot be awakened by any means. A coma may or may not be reversible with treatment.
What are the causes and risks of the condition?
There are many possible causes of a coma, including:
medication, drug, or toxin exposure. This may include alcohol, barbiturate, or narcotic overdose, or carbon monoxide poisoning.
stroke, which is brain damage due to a lack of oxygen to the brain
bleeding into or around the brain. This may occur with a subdural hematoma, epidural hematoma, or subarachnoid hemorrhage.
infections, such as the brain infections called meningitis and encephalitis
low blood sugar levels, called hypoglycemia
out of control diabetes, which is a condition that results in high blood sugar levels
severe liver or kidney disease, such as end stage renal disease
seizures, or epilepsy, due to abnormal electrical activity in the brain
low oxygen levels in the blood. This can occur with severe lung or heart disease. For example, severe asthma, emphysema, irregular heartbeats, or arrhythmias, and a blood clot in the lung, called a pulmonary embolus, can all cause coma from low oxygen levels.
hypothermia, or abnormally low body temperature
severe salt imbalances. This may include an abnormally low sodium level, called hyponatremia or an overly high sodium level, called hypernatremia.
Other causes are also possible. Sometimes, the cause cannot be found.