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Hypernatremia or hypernatraemia is an elevated sodium level in the blood.〔(【引用サイトリンク】title=Hypernatremia: Fluid and Electrolyte Metabolism: Merck Manual Professional )〕 Hypernatremia is generally not caused by an excess of sodium, but rather by a relative deficit of free water in the body. For this reason, hypernatremia often coincides with dehydration. Water is lost from the body in a variety of ways, including perspiration, imperceptible losses from breathing, and in the feces and urine. If the amount of water ingested consistently falls below the amount of water lost, the plasma sodium level will begin to rise, leading to hypernatremia. Rarely, hypernatremia can result from massive salt ingestion, such as may occur from drinking seawater or excessive amounts of a salty liquid like soy sauce.〔(Survival of Acute Hypernatremia Due to Massive Soy Sauce Ingestion ), The Journal of Emergency Medicine〕 When the total protein concentration is low in serum, a falsely high sodium measurement (pseudohypernatremia) tends to occur with the usual assay method, indirect potentiometry, an artifact explained by the electrolyte exclusion effect. Ordinarily, even a small rise in the plasma sodium concentration above the normal range results in a strong sensation of thirst, an increase in free water intake, and correction of the abnormality. Therefore, hypernatremia most often occurs in people such as infants, those with impaired mental status, or the elderly, who may have an intact thirst mechanism but are unable to ask for or obtain water. ==Signs and symptoms== Clinical manifestations of hypernatremia can be subtle, consisting of lethargy, weakness, irritability, neuromuscular excitability, and edema. With more severe elevations of the sodium level, seizures and coma may occur. Severe symptoms are usually due to acute elevation of the plasma sodium concentration to above 157 mEq/L〔name="Reynolds 702–705">〕 (normal blood levels are generally about 135-145 mEq/L for adults and elderly) Values above 180 mEq/L are associated with a high mortality rate, particularly in adults.〔 However such high levels of sodium rarely occur without severe coexisting medical conditions.〔Shier, Butler and Lewis, 11th edition, Hole's Human, Anatomy and Physiology, The McGraw-Hill Companies, Inc, 2007.〕 Serum sodium concentrations have ranged from 150-228 mEq/L in survivors of acute salt overdosage, while levels of 153-255 mEq/L have been observed in fatalities. Vitreous humor is considered to be a better postmortem specimen than postmortem serum for assessing sodium involvement in a death.〔J.I. Coe. Postmortem chemistry update. Emphasis on forensic application. Am. J. For. Med. Path. 14: 91–117, 1993.〕 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「hypernatremia」の詳細全文を読む スポンサード リンク
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