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Orthostatic hypotension, also known as postural hypotension, orthostasis, and colloquially as head rush or dizzy spell, is a form of low blood pressure in which a person's blood pressure falls when suddenly standing up or stretching. In medical terms, it is defined as a fall in systolic blood pressure of at least 20 mm Hg or diastolic blood pressure of at least 10 mm Hg when a person assumes a standing position. The symptom is caused by blood pooling in the lower extremities upon a change in body position. It is quite common and can occur briefly in anyone, although it is prevalent in particular among the elderly, and those with low blood pressure. ==Signs and symptoms== When orthostatic hypotension is present, the following symptoms can occur after sudden standing or stretching (after sitting): * Dizziness * Euphoria or dysphoria * Bodily dissociation * Distortions in hearing * Lightheadedness * Nausea * Headaches * Temporary decrease in hearing * Tinnitus * Blurred or dimmed vision (possibly to the point of momentary blindness) * Seizures * Generalized (or extremity) numbness/tingling and fainting * Coat hanger pain (pain centered in the neck and shoulders) * And in rare, extreme cases, vasovagal syncope (a specific type of fainting). They are consequences of insufficient blood pressure and cerebral perfusion (blood supply). Occasionally, there may be a feeling of warmth in the head and shoulders for a few seconds after the dizziness subsides. The drop in blood pressure may cause a vasovagal episode to occur. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「orthostatic hypotension」の詳細全文を読む スポンサード リンク
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