Decreased extracellular fluid

Introduction The loss of extracellular fluid caused by the loss of body fluids is called dehydration. When people work under high temperature conditions, strenuous exercise or certain diseases (such as severe vomiting, severe diarrhea), they will lose a lot of water and inorganic salts (mainly sodium salts), which will lead to the extracellular fluid osmotic pressure of the body. Drops and symptoms such as decreased blood pressure, increased heart rate, and four chills, severe and even coma. Water balance disorder can be expressed as the total water is too little or too much or the overall water changes little, but the water distribution has a significant difference, that is, the intracellular water increases and the extracellular water decreases, or the intracellular water decreases and the extracellular water increases. Water balance disorders are often accompanied by changes in electrolytes in body fluids and changes in osmotic pressure.

Cause

First, the water balance disorder

Water balance disorder can be expressed as the total water is too little or too much or the overall water changes little, but the water distribution has a significant difference, that is, the intracellular water increases and the extracellular water decreases, or the intracellular water decreases and the extracellular water increases. Water balance disorders are often accompanied by changes in electrolytes in body fluids and changes in osmotic pressure.

Dehydration

The loss of extracellular fluid caused by the loss of body fluids is called dehydration. Dehydration can be divided into hyperosmotic, isotonic and hypocritical dehydration due to changes in plasma sodium concentration.

1. Hypertonic dehydration and dehydration are mainly caused by water loss. Compared with water, electrolyte loss is less, that is, every 1L of body fluid is lost, and electrolyte below about 300mOsm is lost, so that extracellular osmotic pressure is increased, which is more common in drinking water, such as high temperature. A large amount of sweating in the operation, or the patient's non-dominant dehydration is still being carried out, thereby increasing the amount of water discharged. The characteristics of high permeability dehydration are: 1 the concentration of body fluid electrolyte increases, the plasma Na+ concentration is greater than 150mOsm/L or the sum of CL- and HCO3- concentration is greater than 140mmol/L; 2 the extracellular fluid volume is reduced; 3 the intracellular fluid is extracellular The liquid transfer causes a significant decrease in intracellular fluid. The clinical symptoms are thirst, rising body temperature and various neurological symptoms, as well as symptoms such as decreased urine output and consequent weight loss.

2. Isotonic dehydration is mainly caused by the loss of extracellular fluid. Since the lost water and electrolyte are basically balanced, that is, about 300 mOsm/L of electrolyte is lost every time 1 L of body fluid is lost, the extracellular fluid osmotic pressure remains normal, so it is called isotonic dehydration. Common in vomiting and diarrhea and other loss of digestive juice, at this time the patient's body fluid electrolyte concentration did not change. Normally, the plasma Na+ concentration is 130-150 mmol/L or the sum of Cl- and HCO3- concentrations is 120-140 mmol/L; however, the extracellular fluid volume is reduced and the intracellular fluid volume is normal. Isotonic dehydration damage to the body is caused by a decrease in extracellular fluid volume resulting in insufficient blood volume, decreased blood pressure, and peripheral blood circulation disorders.

3. Hypotonic dehydration is mainly caused by electrolyte loss. Compared with water, electrolyte loss is more, that is, every 1L of body fluid is lost, and electrolyte of about 300mOsm or more is lost at the same time. Therefore, the osmotic pressure of extracellular fluid is lower than normal, so it is called low. Permeability dehydration. The cause is more common when the body fluid is lost, only the water is added without supplementing the electrolyte, such as the loss of gastrointestinal digestive juice (diarrhea, vomiting, etc.) and a large amount of sweating, only the water is added and not supplemented from the digestive juice and sweat. The electrolyte lost, resulting in hypotonic dehydration. At this time, the plasma Na+ concentration is less than 130 mmol/L or the sum of the Cl- and HCO3- concentrations is less than 120 mmol/L. The amount of extracellular fluid is reduced, the amount of intracellular fluid is increased, and the body weight is slightly reduced.

an examination

Related inspection

Plasma osmotic pressure (POP)

Symptoms and signs of water shortage are the most common and most important clinical features; the patient has thirst, oliguria, high urine specific gravity, dry lips, decreased skin elasticity, concave eyelids, etc., blood volume, blood pressure changes are lighter than normal, later . The typical performance is that the skin elasticity is reduced, the skin flattening time is prolonged, the eye sockets and the hysteresis are sunken, the tongue surface and the oral cavity film are dry, the skin of the ankle and groin is dry, and the skin is prone to wrinkle. If tachycardia occurs, the erectility is low. Lower blood pressure, lower blood pressure, and jugular vein collapse. The decrease in central venous pressure suggests that blood volume has decreased, effective circulating blood volume has decreased, and signs of circulatory insufficiency due to dehydration have appeared.

Differential diagnosis

Differential diagnosis of extracellular fluid reduction:

(1) Water-deficient dehydration: Loss of water is greater than loss of salt, resulting in an increase in extracellular fluid osmotic pressure, and water is transferred from the cell to the outside of the cell. The initial extracellular fluid volume is reduced, which in turn leads to a decrease in intracellular fluid.

(2) Desiccated dehydration: Loss of salt is greater than loss of water, resulting in decreased extracellular fluid osmotic pressure, renal drainage, resulting in decreased extracellular fluid volume.

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