Loss of sodium more than water and low serum sodium concentration

Introduction Hypotonic dehydration (hypotonic dehydration), also known as secondary dehydration or hyponatremia with decreased extracellular fluid, is characterized by more sodium loss than dehydration, serum sodium concentration <135mmol / L, plasma osmotic pressure <280mOsm / L. Hyponatremia is serum sodium <135mmol / L, only reflects the decrease in sodium concentration in plasma, does not necessarily mean the loss of total sodium in the body, the overall sodium can be normal or even slightly increased. According to the degree of sodium deficiency, common symptoms include dizziness, blurred vision, weakness, pulse speed, severe unconsciousness, muscle spasm, weak tendon reflexes, and coma.

Cause

After the fluid is lost, only the water is added or the glucose solution is instilled, and no sodium is added. Renal and non-renal loss of sodium, accompanied by loss of water but less than the loss of sodium. Plasma osmotic pressure is reduced (blood sodium concentration is the main component of plasma osmotic pressure maintenance). Loss of sodium is often accompanied by loss of water. Regardless of the cause of hyponatremia, the effective blood volume is reduced, resulting in the release of non-osmotic ADH, in order to increase the reabsorption of water by the renal tubules, so as to avoid further reduction of blood volume. However, this protective mechanism is more important for the reduction of blood sodium and plasma osmotic pressure. This compensatory mechanism occurs in the early stage of effective blood volume reduction. When blood [Na+] drops to <135mmol/L, ADH release is inhibited.

an examination

Related inspection

Blood analyzer to check blood biochemistry six tests for serum sodium (Na+, Na)

Loss of sodium is more than dehydration, resulting in decreased extracellular fluid osmotic pressure and decreased serum sodium concentration. The normal serum sodium concentration is 135 mmol/L-145 mmol/L.

Hypotonic dehydration is mainly caused by a significant decrease in extracellular fluid, accompanied by decreased blood volume and peripheral circulatory failure, often with venous collapse, decreased arterial blood pressure, and fine pulse rate.

If hypotonic dehydration is sodium loss through the kidney, the patient's urinary sodium content increases (>20mmo1/L); if it is caused by extrarenal causes, the renal blood flow decreases due to hypovolemia, and the RAA system and blood sodium concentration decrease. Direct stimulation of the adrenal cortical spheroidal band increased the secretion of ADS, and increased renal sodium reabsorption, resulting in a decrease in urinary sodium (<10mmo1/L).

As the extracellular fluid is reduced, the plasma volume is reduced, the blood is concentrated, and the plasma colloid osmotic pressure is increased, which causes the interstitial fluid to enter the blood vessel to supplement the blood volume. As a result, the interstitial fluid is more reduced, so the patient's skin elasticity is lost, the eye socket and Infant sag sag, showing obvious dehydration.

Differential diagnosis

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.

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.

Loss of sodium is more than dehydration, resulting in decreased extracellular fluid osmotic pressure and decreased serum sodium concentration. The normal serum sodium concentration is 135 mmol/L-145 mmol/L.

Hypotonic dehydration is mainly caused by a significant decrease in extracellular fluid, accompanied by decreased blood volume and peripheral circulatory failure, often with venous collapse, decreased arterial blood pressure, and fine pulse rate.

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