Dialysis is mainly for patients with uremic syndrome. If patients have severe water and sodium retention, significant toxin accumulation, acidosis, hyperkalemia, etc., they need to be treated with hemodialysis. Specifically, patients with sodium retention may have significant edema in both lower extremities, heart failure, and cerebral edema. Toxic accumulation is represented by creatinine and urea. If creatinine exceeds 707 μmoI/L and urea exceeds 28 mmol/L, hemodialysis is required. Acidosis is calculated by PH and CO2 binding capacity. If PH is less than 7.2 and CO2 binding capacity is less than 13mmol/L, it indicates that acidosis is more obvious and hemodialysis needs to be given. High blood potassium can lead to malignant arrhythmia, which is a very common cause of sudden death in uremic patients, and hemodialysis is required when the blood potassium is higher than 6.5 mmol/L. Some patients are recommended to be given early hemodialysis, such as children and the elderly.