Postural hypotension is hypotension that occurs as a result of a change in position, such as a sudden shift from a lying position to an upright position, or prolonged standing. It is usually considered postural hypotension when the systolic blood pressure drops 20 mm Hg or the diastolic blood pressure drops 10 mm Hg after standing compared with that in the lying position. Postural hypotension is divided into two types: sudden and secondary. Sudden hypotension is mostly caused by the dysfunction of the small upright arteries due to the disturbance of the plant nervous system. The main manifestation is low blood pressure when standing upright, which may be accompanied by unstable standing, blurred vision, dizziness, weakness, incontinence, etc. In severe cases, syncope may occur. Secondary hypotension is often seen in spinal cord disease, acute infectious diseases or serious infections (e.g. lobar pneumonia), endocrine disorders, chronic malnutrition or after the use of antihypertensive drugs or sedative drugs. Postural hypotension is a common disease in the elderly, according to statistics, about 15% of the elderly over 65 years of age have postural hypotension, of which up to 30% to 50% of the elderly over 75 years of age. The gradual hardening of the heart and vascular system in the elderly, as well as the reduction of large-vessel elastic fibers and the enhancement of sympathetic nerves, can cause systolic blood pressure to rise in the elderly. Long-term high blood pressure not only damages the sensitivity of pressure receptors (located at the carotid artery), but also affects the compliance of blood vessels and heart chambers. When there is a sudden change in body position or after taking antihypertensive medication, the risk of ischemia is greatly increased along with a sudden drop in blood pressure. In addition, the poorer energy to tolerate hypovolemia in the elderly may be related to their impaired ventricular diastolic filling. Therefore, any acute illness resulting in excessive water loss, or insufficient oral fluids, or after taking antihypertensive drugs and diuretics, as well as patients who are usually less active and bedridden for a long time, are prone to postural hypotension after standing up.