Dehydration

Introduction Dehydration refers to a group of clinical syndromes caused by a decrease in extracellular fluid. Dehydration refers to the fact that the human body consumes a large amount of water due to lesions, but cannot be immediately replenished, causing a symptom of metabolic disorder. In severe cases, it may cause collapse and even life-threatening. It is necessary to rely on infusion to replenish body fluids. According to the changes of blood sodium or osmotic pressure, dehydration is divided into hypotonic dehydration, ie, extracellular fluid reduction combined with hyponatremia; hypertonic dehydration, ie, extracellular fluid reduction combined with hypernatremia; isotonic dehydration Extracellular fluid is reduced and blood sodium is normal.

Cause

Reasons for dehydration:

Etiology classification

There are many reasons for the loss or reduction of body fluids. Under normal circumstances, water loss and loss of sodium coexist. In some cases, water loss is more than loss of sodium, or loss of sodium is more than loss of water. In some cases, water supplementation is insufficient or sodium supplementation is insufficient on the basis of water loss and sodium loss. Types of dehydration and the inadequacy of dehydration. Therefore the following causes of different types of dehydration are not absolutely constant.

First, high permeability dehydration

(1) Insufficient water intake

Patients with coma or mental disorders do not have a thirst. They do not know that they need water and water intake, or that the oral and upper gastrointestinal diseases cannot enter the water, or that the water source is cut off, such as in deserts and accidents.

(2) Increase in water demand

Patients with high fever or increased water demand in high temperature environments, but insufficient supplementation.

(3) excessive water loss

1. Vomiting, diarrhea, intestinal thinness, and gastrointestinal drainage cause a large amount of digestive juice to be lost and cannot be replenished.

2. Diabetes insipidus or renal tubular anti-diuretic hormone (ADH) is not sensitive and discharges a large amount of diluted urine, receiving lysogenic diuretics (mannitol, glycine, etc.) or high protein salt diet excessive intake of osmotic diuretic Uncontrolled diabetic patients expel a large amount of diabetes, and renal dysfunction leads to more drainage of the kidneys than sodium.

3. A lot of sweating during high temperature and heavy physical labor.

4. Tracheotomy and hyperventilation can cause large amounts of water to be lost from the respiratory tract. This lost water is pure water, which can easily cause hypertonic dehydration in the case of insufficient water intake.

Second, isotonic dehydration

1. In the digestive tract, the liquid in the digestive tract, except for saliva, gastric juice and the secretion of sodium in the colon, contains less sodium. The content of sodium in other secretions of the digestive tract is similar to that of plasma, so diarrhea and duodenal decompression. Digestive tract thin tubes and the like are also common causes of isotonic dehydration. Patients with hypertonic dehydration can also cause isotonic dehydration with only a small amount of water supplementation.

2. A large amount of drainage of pleural effusion, ascites, or chest and abdominal drainage.

3. Large areas of skin burns cause a large amount of exudate.

4. Acute massive blood loss.

Third, low permeability dehydration

Hypotonic dehydration is common in hypertonic or isotonic dehydration when only water is added without supplemental salts. Such as the above-mentioned large loss of digestive juice, the application of diuretics, acute renal failure, polyuria, diabetes insipidus, diabetes and renal dysfunction caused by the discharge of a large amount of urine, a lot of sweating, a large number of chest, ascites, a large number Blood loss and so on.

Fourth, insufficient renal drainage

In acute and chronic renal insufficiency and oliguria, the renal drainage function is drastically reduced. If the water intake is not limited, it can cause water retention in the body, severe heart failure or cirrhosis, due to effective circulating blood volume and renal blood flow. Reduced, kidney drainage is also significantly reduced, if increased water load is also likely to cause water poisoning.

5. In the late stage of hypotonic dehydration, extracellular fluid is transferred to the cells due to hypotonic extracellular fluid. It can cause intracellular edema, so when you input a lot of water, it can cause water intoxication.

an examination

Related inspection

Urine routine urine volume urinary blood routine blood pressure

Diagnosis and examination of dehydration:

First, medical history

Should pay attention to the various possible conditions that cause fluid loss, such as diarrhea, vomiting, various drainage, sweating urine, blood loss. Exudate, diet, including water intake, if necessary, calculate the total amount of liquid intake and discharge daily. In addition, you should also pay attention to the changes in weight, eating habits and past history, such as the head with or without trauma, changes in consciousness and history of diabetes.

Patients with conscious consciousness are more likely to make a diagnosis based on medical history, physical symptoms, body weight, and hematuria. However, it is easy to diagnose patients who are unconscious or have entered a coma. In particular, patients with coma can not talk about thirst, ask for water, nasal feeding, high protein and high concentration of liquid diet caused by "hypertension syndrome" or "nasal feeding syndrome", due to the presence of solute diuretic, the patient's urine volume is not significantly reduced, this It is easy to cause false leak diagnosis.

Second, physical examination

Should pay attention to the patient's nutritional status, mental state, fever and sweating, should pay attention to the performance of the skin and facial film, the typical performance of dehydration is the reduction of skin elasticity, skin flattening time, eye socket and hysteresis depression, tongue and oral film Dry, dry skin of the ankle and groin, the skin is easy to "wrinkle. If tachycardia, orthostatic hypotension, lower blood pressure, jugular vein collapse. Lower central venous pressure, it indicates that blood volume has been reduced, effective circulation The blood volume is reduced, and the signs of circulatory insufficiency caused by dehydration have appeared. The hypertonic dehydration and the hypotonic dehydration signs are slightly different. The former has thirst, weakness, irritability, and often fever; the latter often shows headache and dizziness. Debilitating, weak and indifferent, dehydrated body surface symptoms appear early and more obvious, and the symptoms of circulatory failure appear early and obvious. Clinically, according to weight loss (water loss) and clinical manifestations, dehydration points will be For three degrees:

l. Mild dehydration and water loss account for 2%-3% of body weight or 5% of body weight. Only general neurological symptoms such as headache, dizziness, weakness, and skin elasticity are slightly reduced. Hypertonic dehydration has thirst.

2. Moderate dehydration loss is 3%-6% of body weight or 5%-10% of body weight loss. The symptoms of dehydration are obvious, and symptoms of circulatory insufficiency begin to appear.

3. Severe dehydration loss of water accounted for more than 6% of body weight or weight loss of more than 10%, the aforementioned symptoms increased, and even shock, coma.

Third, laboratory inspection

1. Urine tests include urine volume, urine relative density, urine sodium and other ingredients. The hyperosmotic and hypotonic dehydration performances are different. In the early stage of hypotonic dehydration, the amount of urine does not decrease, the later period decreases, the urine relative density is low, and the urine sodium is significantly reduced. In the early stage of hypertonic dehydration, the amount of urine is reduced, the relative density of urine is high, and the urinary steel is high. A large amount of urine and a relatively high density should pay attention to solute diuresis, check urine sugar, ketone body and so on.

2. Blood tests often show changes when moderately dehydrated. Elevated serum sodium is often an important indicator of the degree of dehydration. Serum sodium should be more than 150 mmol/L. Plasma osmotic pressure can reflect the osmotic pressure of extracellular fluid, >310mmo/L is hyperosmotic, and <280mmol/L is hypotonic. When the hypertonic dehydration osmotic pressure>330mmol/L, the brain cells dehydrate, the nerve cells shrink, and the brain tissue is congested and the nervous system function changes. When the temperature is >360mmol/L, sleepiness, even coma and respiratory arrest may occur. Hemoglobin is significantly elevated, often reflecting the phenomenon of blood concentration. When hypotonic dehydration occurs, water enters TY red blood cells, so hematocrit increases, and the average red blood cell volume or mean blood cell volume (MCV) increases. Elevated blood urea nitrogen indicates renal dysfunction, which occurs mostly in the late stage of dehydration or dehydration.

Differential diagnosis

Differential diagnosis of dehydration:

Dehydration of brain cells: When the extracellular fluid osmotic pressure is increased, dehydration of brain cells can cause a series of symptoms of central nervous system dysfunction, including lethargy, muscle twitching, coma, and even death. It belongs to hypertonic dehydration. When the brain volume is significantly reduced due to dehydration, the vascular tension between the skull and the cerebral cortex increases, which can lead to rupture of the vein and local intracerebral hemorrhage and subarachnoid hemorrhage. Dehydration of brain cells, showing disturbance of consciousness, irritability, neck rigidity, severe angulation, muscle tremor, local or general convulsions. There are even sequelae. The capillary endothelial cells in the brain tissue are closely connected with the brain cells, and there is no interstitial between the blood and the brain. When the brain cells are dehydrated, the water directly flows into the blood circulation. Because the brain tissue is enclosed in the cranial cavity, the shrinkage of the brain cells can reduce the intracranial pressure, and the blood pressure of the heart pump has not changed. As a result, the cerebral blood vessels can be dilated, and in severe cases, cerebral hemorrhage or thrombosis can be caused.

Dehydration heat: refers to the phenomenon that the body (especially children), after severe dehydration, is reduced by the evaporation of water from the skin, which is caused by the heat dissipation of the body, which leads to an increase in body temperature. When the indoor temperature is too high, the water of the newborn's skin evaporates, the intake of breast milk is insufficient, and the blood is concentrated. The body temperature can rise to 37.8-38.2 degrees in a short period of time, and there are no other symptoms.

Dehydration of the nucleus pulposus: the degeneration of the nucleus pulposus is mainly manifested by a small amount of pathological changes such as a decrease in water content and a loosening of the nucleus due to dehydration. After dehydration, the intervertebral disc loses its normal elasticity and tension. The nucleus pulposus is prominent due to heavier trauma or multiple recurring inconspicuous injuries, resulting in a weak or broken fibrous ring.

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