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In physiology and medicine, hypovolemia (also hypovolaemia, oligemia or shock) is a state of decreased blood volume; more specifically, decrease in volume of blood plasma. It is thus the intravascular component of volume contraction (or loss of blood volume due to things such as hemorrhaging or dehydration), but, as it also is the most essential one, ''hypovolemia'' and ''volume contraction'' are sometimes used synonymously. Hypovolemia is characterized by salt (sodium) depletion and thus differs from dehydration, which is defined as excessive loss of body water. ==Causes== Common causes of hypovolemia are〔Sircar, S. Principles of Medical Physiology. Thieme Medical Pub. ISBN 9781588905727〕 * Loss of blood (external or internal bleeding or blood donation) * Loss of plasma (severe burns and lesions discharging fluid) * Loss of body sodium and consequent intravascular water; e.g. diarrhea or vomiting * Vasodilation (involving widening of blood vessels) such as trauma leading to dysfunction of nerve activity on blood vessels and inhibition of the vasomotor center in the brain or drugs such as vasodilators typically used to treat hypertensive individuals. Excessive sweating is not a cause of hypovolemia, because the body eliminates significantly more water than sodium.〔(【引用サイトリンク】title=Saladin 5e Extended Outline : Chapter 24 : Water, Electrolyte, and Acid–Base Balance ) 〕 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「Hypovolemia」の詳細全文を読む スポンサード リンク
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