Transient loss of consciousness is known as syncope in medicine, which is the sudden onset of a transient state of loss of consciousness. It is a syndrome of sudden and transient loss of consciousness due to sudden decrease in cardiac output, severe hypotension, and transient generalized cerebral insufficiency of blood supply, which leads to high inhibition of the cerebral cortex. Most of the syncope can recover consciousness by itself after appropriate treatment or without any treatment, and the prognosis is good. When syncope is the first symptom of a serious disease, the prognosis is dangerous, such as cardiac syncope, the mortality rate can reach 20%-30%. Transient loss of consciousness is characterized by transient loss of consciousness, decreased blood pressure, slowed heart rate and neurological signs. Transient loss of consciousness can be induced by many reasons, such as hypoglycemia, upright hypotensive syncope, vasovagal syncope and so on.