Water and sodium are deficient at the same time, but water deficiency is less than sodium deficiency, serum sodium is below the normal range, and extracellular fluid is hypotonic. The body reduces the secretion of antidiuretic hormone, which reduces the reabsorption of water by renal tubules and increases the urine volume, thus improving the osmotic pressure of extracellular fluid. But the amount of extracellular fluid decreased even more. Tissue fluid entering the blood circulation can partially compensate the blood volume, but the decrease of tissue fluid exceeds that of plasma. Faced with the obvious reduction of circulating blood volume, the body will no longer consider osmotic pressure and strive to maintain blood volume. The excitation of renin-aldosterone system reduces renal sodium excretion and increases the reabsorption of Cl- and water. Therefore, the content of sodium chloride in urine decreased obviously. Decreased blood volume will stimulate the posterior pituitary gland, increase the secretion of antidiuretic hormone, increase water reabsorption, and lead to oliguria. If the blood volume decreases and will continue to decrease, when the above compensation function can no longer maintain the blood volume, shock will occur. This kind of shock caused by massive sodium loss is also called hyponatremia shock.

clinical picture

According to the degree of sodium deficiency, the common symptoms are dizziness, blurred vision, fatigue, rapid pulse, and in severe cases, unconsciousness, muscle spasmodic pain, weakened tendon reflex, coma and so on. According to the degree of sodium deficiency, hypotonic water deficiency is clinically divided into three degrees:

1, mild sodium deficiency: the patient feels weak, dizzy, numb hands and feet, and thirsty is not obvious. When the blood sodium is lower than135 mol/L, the urine sodium decreases.

2, moderate sodium deficiency: In addition to the above symptoms, nausea, vomiting, rapid pulse, unstable blood pressure, blurred vision, and less urine. Serum sodium is lower than1.30 mmol/L.

3. Severe sodium deficiency: the patient is unconscious, tendon reflex is weakened or disappeared, and numbness or even coma occurs. Shock often occurs. Serum sodium is lower than1.20 mmol/L.

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