Blood purification is a kind of renal replacement therapy, which can also be used in the treatment of some poisoned patients. Generally speaking, it has no obvious harm to the body, but some corresponding complications may occur in the course of treatment, mainly including: dialysis imbalance syndrome, hypotension, thrombus, air embolism and so on. In addition, bleeding and other complications may occur because of long-term application of heparin. 1. Dialysis imbalance syndrome: it is mostly seen in patients who are on dialysis for the first time, and the dialysis efficiency is too high, or the blood creatinine and urea level before dialysis is very high, which may cause the patient’s intracranial pressure to increase and cerebral edema, so that the patient may have symptoms such as nausea, vomiting, headache and so on, and when it is serious, it may also have coma or even death. 2. Hypotension: there are many reasons for hypotension, including excessive and rapid ultrafiltration, insufficient effective blood volume of the patient, and autonomic neuropathy. 3. Thrombosis: Thrombosis may occur when dialysis is performed via artificial blood vessels or deep vein catheters. 4. Air embolism, painful myalgias, fever, dialyzer first use syndrome, and cardiac arrhythmias are also common.