Depending on the pathogenesis and clinical manifestations, heat stroke is usually classified as heat cramps, heat exhaustion, and heat (sun)-induced illness. The above 3 conditions may develop sequentially or may overlap.1. Heat cramps: headache, dizziness and painful spasms of the limbs and abdominal wall muscles after strenuous activity, profuse sweating and drinking hypotonic fluids, limited movement of the limbs, sometimes abdominal pain similar to the performance of acute abdomen, relieved in a few minutes, no obvious temperature increase, no mental disturbance. Heat cramps can also be early manifestations of pyrexia. 2, heat exhaustion: mostly seen in the elderly, children and patients with chronic diseases. Severe heat stress, excessive loss of body fluids and body sodium causes insufficient circulating volume. The manifestations are excessive sweating, fatigue, weakness, dizziness, headache, nausea, vomiting and muscle cramps, significantly increased heart rate, upright hypotension or syncope. The central body temperature is not elevated above 40°C, and there is no delirium. Increased hematocrit, hypernatremia, mild azotemia and abnormal liver function. 3. pyrexia: hyperthermia with delirium. Early damaged organs are brain, liver, kidney and heart in that order.