Loss of water more than sodium and high serum sodium concentration

Introduction Hypertonic dehydration (hypertonic dehydration), also known as primary dehydration or hypernatremia with decreased extracellular fluid, characterized by loss of water more than loss of sodium, serum sodium concentration >150mmol / L, plasma osmotic pressure >310mOsm /L. When the lack of water is more than the lack of sodium, the extracellular fluid osmotic pressure increases, the secretion of antidiuretic hormone increases, the reabsorption of water by the renal tubules increases, and the amount of urine decreases. Aldosterone secretion increases, and sodium and water reabsorption increases to maintain blood volume. If the water shortage continues, the extracellular fluid osmotic pressure is further increased, and the intracellular fluid is moved to the outside of the cell. Eventually, the degree of water shortage in the cell exceeds the degree of water shortage in the extracellular fluid, and finally the brain cell dysfunction is caused by water shortage of the brain cell.

Cause

Water and sodium are lost at the same time, but the lack of water is more than the lack of sodium, so the serum sodium is higher than the normal range, and the extracellular fluid is hyperosmotic. The main symptoms in the early stage were thirst, decreased urine output, weakness, nausea and vomiting, and elevated body temperature; signs of dehydration. In the late stage, there are clinical manifestations of brain cell dehydration, such as irritability, irritability or mental apathy, sleepiness, convulsions or epileptic seizures and coma; signs of increased muscle tone and hyperreflexia, and severe death.

an examination

Related inspection

Serum sodium (Na+, Na) by serum sodium blood analyzer

Pathophysiological changes: more water loss than sodium loss leads to increased extracellular fluid osmotic pressure. The serum sodium concentration is >150mmol/L, the normal serum sodium concentration is 135-145mmol/L, which accounts for 92% of plasma cations and 90% of total osmotic pressure. Therefore, the amount of plasma sodium plays a decisive role in osmotic pressure.

The degree of water shortage is different, the symptoms should be different, generally the hypertonic water shortage is three degrees:

Mild water shortage: Except for thirst, there are no other symptoms. The amount of water shortage is 2% to 4% of body weight.

Moderate water shortage: extreme thirst, with fatigue, low urine, and high urine weight. Dry lips, poor skin elasticity, eye sockets, often irritated. The water shortage is 4% to 6% of body weight.

Severe water shortage: In addition to the above symptoms, there are symptoms of brain dysfunction such as mania, hallucinations, slang, and even coma. The amount of water shortage is more than 6% of body weight.

Differential diagnosis

Hypotonic dehydration: also known as secondary dehydration or hyponatremia with decreased extracellular fluid, characterized by loss of sodium more than loss of water, serum sodium concentration <135mmol / L, plasma osmotic pressure < 280mosm/L.

Isotonic dehydration: also known as mixed dehydration or a decrease in extracellular fluid with normal blood sodium concentration. It is characterized in that water is lost in proportion to sodium, the serum sodium concentration is 130-150 mmol/I, and the plasma osmotic pressure is 280-310 mosm/L.

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