There are many causes of coma, commonly as follows: stroke coma: patients often have a history of hypertension, cerebral atherosclerosis, usually rapid onset, sudden onset of limb paralysis, speech impairment, usually accompanied by headache, epileptiform seizures, etc., and soon the patient falls into a coma with unstable vital signs, etc. CNS infectious coma: Severe CNS infections can cause impaired consciousness or coma. Such as meningitis, encephalitis, brain abscess, infectious toxic encephalopathy, etc. Patients usually have fever, vomiting, headache, irritability, delirium and other impairment of consciousness. Epileptic coma: Coma can result after a grand mal seizure or grand mal persistence. Diabetic coma: Patients mostly have symptoms such as irritable thirst, excessive drinking, polyuria, loss of appetite, nausea, drowsiness, and later coma. On examination, dry skin and mucous membrane, sunken eyes, ketone body odor, high urinary ketone body, and very high blood sugar are seen. Hypoglycemic coma: diabetic patients with overdose of insulin or other hypoglycemic drugs resulting in hypoglycemia, sudden onset, breathing without ketone body odor, low blood glucose of 3.3 mmol/L, urinary ketones, urinary sugar. Uremic coma: Patients have a history of renal disease, acidosis and azotemia symptoms, such as nausea and vomiting, reduced appetite, weakness and fatigue, and finally enter coma, may have epileptic seizures, blood urea nitrogen, uric acid and creatinine are increased, with elevated blood potassium and reduced blood calcium and sodium. Hepatic coma: also known as hepatic encephalopathy and hepatocerebral syndrome, patients with severe liver damage develop impaired consciousness and neurological and psychiatric symptoms, and patients with acute heavy hepatitis and liver failure quickly enter coma. Serum aminotransferase rises rapidly, and serum bilirubin and aminotransferase may appear to be separated. Chronic progressive liver disease appears coma slowly, often with loss of appetite, hepatosplenomegaly, abdominal distension, jaundice, liver odor and other symptoms. Pulmonary coma: It is hypercapnia, mostly seen in patients with chronic pulmonary heart disease and emphysema over 50, often induced by infection. The onset is sudden, with headache, lethargy and amnesia, followed by respiratory failure and impaired consciousness, with blurred consciousness and drowsiness in mild cases, or coma in severe cases. Pituitary coma: Complicated by hypopituitarism, mainly due to hypoglycemia, salt loss, water intoxication, etc. Clinical manifestations are indifference, drowsiness, memory loss, disorientation, and finally coma. Blood glucose is significantly low, and 24-hour urinary 17-ketosteroids and 17-hydroxysteroids are significantly lower. Exogenous poisoning: toxic substances are mostly central nervous system depressants, anesthetics, carbon monoxide, ethanol, cyanide, anticholinergic drugs, etc.