Water and salt metabolism disorder

Introduction Water and inorganic salts (electrolytes) are important components of the body and an important component of body fluids. Body fluid is the internal environment of cell life activity, and its constant capacity, osmotic pressure, pH and appropriate ion concentration play an important role in ensuring the normal metabolism of cells. For example, hypotonic water shortage is the simultaneous loss of water and sodium, but the lack of water is less than the loss of sodium. This situation is the metabolic imbalance between water and inorganic salts.

Cause

Hypotonic water shortage is also called chronic water shortage or secondary water shortage. Water and sodium are missing at the same time, but the lack of water is less than the loss of sodium, so the serum sodium is lower than the normal range, and the extracellular fluid is hypotonic. The body reduces the secretion of antidiuretic hormone, so that the reabsorption of water in the renal tubules is reduced, and the amount of urine is increased to increase the osmotic pressure of the extracellular fluid. However, the amount of extracellular fluid is reduced more, and the interstitial fluid enters the blood circulation. Although it can partially compensate the blood volume, the interstitial fluid is reduced more than the plasma. Faced with a significant reduction in circulating blood volume, the body will no longer consider osmotic pressure and try to maintain blood volume. Excited by the renin-aldosterone system, the kidneys are reduced in sodium, and CI- and water reabsorption increases. Therefore, the sodium chloride content in the urine is significantly reduced. Decreased blood volume will stimulate the posterior pituitary, which will increase the secretion of antidiuretic hormone and increase the reabsorption of water, leading to oliguria. If the blood volume continues to decrease and the above compensatory function is no longer able to maintain blood volume, shock will occur. This kind of shock caused by a large amount of sodium loss, also known as hyponatremia shock.

The main causes are: 1 continuous loss of gastrointestinal digestive juice, such as repeated vomiting, long-term gastrointestinal tract attraction or chronic intestinal obstruction, so that sodium is lost with a large amount of digestive juice; 2 large wound surface chronic exudate; 3 kidney discharge water and Excessive sodium, such as the application of sodium-diuretic dilute (chlorthalidone, uric acid, etc.), did not pay attention to the supply of appropriate sodium salt, so that the body's sodium deficiency is relatively more than water shortage.

an examination

Related inspection

Blood test for sucrose water hemolysis

Diagnosis According to the patient's history and clinical manifestations of fluid loss, the diagnosis of hypotonic water deficit can be initially made. Further can be made:

1 urine Na +, CI - determination, often significantly reduced. Although there may be no significant changes in serum sodium in mild sodium deficiency, the amount of sodium chloride in the urine has often decreased. Excessive discharge of water and sodium in the kidney. For example, when a sodium-diuretic dilute (chlorthalidone, uric acid, etc.) is applied, an appropriate amount of sodium salt is not paid attention, so that the sodium deficiency in the body is relatively more than that of water deficiency.

2 serum sodium determination, according to the results of the determination, can determine the degree of sodium deficiency; serum sodium is lower than 135mmol / L, indicating hyponatremia such as repeated vomiting, long-term gastrointestinal tract attraction or chronic intestinal obstruction, so that sodium with a large number of digestion Lost in liquid.

3 red blood cell count, hemoglobin volume, hematocrit, blood non-protein sodium nitride and urea increased, and urine specific gravity is often below 1.010.

Differential diagnosis

It should be differentiated from isotonic water shortage, hyperosmotic water shortage and so on.

Isotonic water shortage is also called acute or mixed water shortage. Since water and sodium are lost in proportion at this time, serum sodium is still in the normal range, and the osmotic pressure of the extracellular fluid can be kept normal. However, isotonic water shortage can cause a rapid decrease in extracellular fluid volume (including circulating blood volume).

Hypertonic water shortage is also called primary water shortage. Although water and sodium are lost at the same time, due to lack of water, the serum sodium is higher than the normal range, and the osmotic pressure of the extracellular fluid is increased.

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