In medicine, fainting refers to the complete loss of awareness, which is a serious phenomenon of complete loss of things in the human body. The reason is because of various reasons that the higher nerves are severely pressed and the performance of high consciousness boudoir broken, must quickly identify the cause, timely adoption of useful methods to rescue. Coma is usually divided into two kinds, deep coma and shallow coma. The clinical coma is divided into two kinds of shallow coma and deep coma. 1, shallow coma random motor loss, only a relatively small number of unconscious spontaneous movements, to painful stimuli (such as pressure on the supraorbital rim), there is an avoidance response and painful expression, but can not answer questions or perform simple commands. The gag reflex, cough reflex, corneal reflex, pupil-to-light reflex, and tendon reflex are still present, and there are no significant changes in vital signs. It may be accompanied by delirium and agitation. 2, deep coma, spontaneous movements completely disappeared, muscle relaxation, no response to external stimuli, corneal reflex, pupillary reflex, cough reflex, swallowing reflex and tendon reflex all disappeared, irregular breathing, blood pressure decreased. In other words, all kinds of reactions and reflexes are gone. The pathological signs continue to exist or disappear, and there may be changes in vital signs. Coma is a sign of critical condition and the cause should be actively sought and should be actively managed. Causes of coma: 1. Coma caused by acute infectious diseases. The most common are various meningitis, encephalitis, toxic dysentery, and sepsis, pneumonia, brain abscess, etc. 2, non-infectious diseases of the central nervous system caused by coma. Such as craniocerebral trauma, cerebral hemorrhage, advanced brain tumor, brain herniation caused by cerebral edema, etc. 3.Coma caused by drug or chemical poisoning. Such as organophosphorus pesticide poisoning, carbon monoxide poisoning, and ethanol (alcohol), barbiturates, heliopiazine, isoniazid fat, belladonna drug poisoning, etc. 4. Coma caused by accidental injury. Such as drowning, electrocution, heat stroke, etc. 5.Liver coma. Often have a history of liver disease. 6, uremic coma. Most have a history of nephritis, coma is progressive aggravation. Before coma, there are often signs of loss of appetite, nausea and vomiting, diarrhea, hypertension, swelling, anemia and renal hypofunction. 7. Glucose coma. Coma can occur when blood glucose is below 50 mg%. Before coma, there are often symptoms of hypoglycemia such as hunger, dizziness, weakness, sweating and hand trembling. As you can see from the above, there are many causes and situations that cause coma, and they are rather complicated, so to find the correct cause you should go to the hospital for careful examination. However, in many cases, time is of the essence, and the patient cannot wait to go to the hospital before he or she has a life crisis. So family self-help is especially critical, usually should learn more about first aid, in case of an accident.