The main reasons for hypotension caused by dialysis are as follows: 1. The patient is on dialysis for the first time, old and frail, due to the rapid entry of blood into the extracorporeal circulation within a short period of time, resulting in a decrease in the volume of blood circulating in the human body. 2. Because ultrafiltration during dialysis is too fast and excessive, resulting in a large volume of blood in the whole body in a short period of time. 3. Severe arrhythmias occur during dialysis, resulting in a decrease in blood ejection from the heart to the peripheral vasculature. 4. Heparin is used for anticoagulation during hemodialysis, and heparinization can cause acute pericardial tamponade and hypotension. 5. Hypotension can also occur when acute heart failure or acute infarction occurs. 6. The patient may be on antihypertensive medication. 7. The patient may have various kinds of bleeding, etc.