(1) Hypertonic dehydration is also called hypernatremia due to primary dehydration or decrease of extracellular fluid, which is characterized by more water loss than sodium loss, serum sodium concentration > 150 mmol/L, plasma osmotic pressure > 3 10 mosm/L.. 1, causes and mechanisms (l) insufficient drinking water. Dystonia: Hypothalamic lesions can damage the thirst center, and some patients with cerebrovascular accidents will also lose their thirst; (3) Without water, such as getting lost in the desert or being shipwrecked. Under the above circumstances, water is evaporated through the constant insensitivity of skin and breathing, resulting in more water loss than sodium loss and increased plasma osmotic pressure. (2) Excessive water loss: including simple water loss and more water loss than sodium loss, that is, the loss of hypotonic liquid. ① Simple dehydration includes percutaneous dehydration, respiratory dehydration and renal dehydration. The former is caused by high fever, hyperthyroidism and hyperventilation, while the latter is caused by insufficient production and release of ADH in central diabetes insipidus and insufficient response to ADH in renal diabetes insipidus, so the kidney excretes a lot of water. Because this dehydration occurs at the farthest end of nephron, most of the pro-sodium ions have been reabsorbed in this part, so patients can excrete 10 ~ 15L of diluted urine every day, which contains only a few millimoles of sodium. ② The loss of water is more than that of sodium. First, the digestive juice with low sodium content is lost through the gastrointestinal tract, which is mainly seen in some infants with watery diarrhea, and the fecal sodium concentration is below 60 mmol /L L ... Secondly, when sweating, low-permeability liquid is lost, which often happens in high temperature environment. In addition, when hypertonic substances (such as mannitol, urea and hypertonic glucose) are repeatedly injected intravenously, osmotic diuresis may lose more water than sodium due to the increase of osmotic pressure of renal tubular fluid. 2, pathophysiological changes, water loss is more than sodium loss, which leads to the increase of osmotic pressure of extracellular fluid, which is a pathophysiological change caused by hyperosmotic dehydration (l) The increase of osmotic pressure of extracellular fluid stimulates thirst center and causes thirst for drinking water. (2) The increase of osmotic pressure of extracellular fluid stimulates the osmotic pressure receptor of hypothalamic supraoptic nucleus, which increases the release of ADH and the reabsorption of water by renal tubules, resulting in the decrease of urine volume and the increase of urine specific gravity. (3) The increase of osmotic pressure of extracellular fluid can make intracellular fluid water with relatively low osmotic pressure transfer to the outside of the cell. It can be seen that during hypertonic dehydration, both intracellular fluid and extracellular fluid decrease, but the intracellular fluid mainly decreases and cell dehydration occurs, and extracellular fluid can be supplemented from the above three aspects, so the decrease of extracellular fluid and blood volume is not as obvious as that of hypotonic dehydration, and fewer people have circulatory disorders. (4) In patients with early or mild symptoms, sodium is still excreted with urine because the blood volume has not decreased significantly and aldosterone secretion has not increased, and its concentration can be increased due to the increase of water reabsorption caused by ADH; In advanced or severe patients, due to the decrease of blood volume and the increase of ADS secretion, the urinary sodium content can be reduced. (5) Severe increase of osmotic pressure of extracellular fluid can lead to dehydration, fever and dehydration of brain cells. The former is due to the dehydration of skin and sweat gland cells, the sweat secreted by sweat glands and the evaporation of skin moisture are reduced, and the heat dissipation is affected, resulting in an increase in body temperature, which is more common in infants with poor thermoregulation ability. The latter can cause symptoms of central nervous system dysfunction, such as drowsiness, muscle twitching, coma and even death. When the brain volume is obviously reduced due to dehydration, the space between the skull and the cerebral cortex increases the vascular tension, which leads to intracranial hemorrhage and subarachnoid hemorrhage due to vein rupture. 3, the principle of prevention and treatment to prevent the primary disease, remove the cause. Simple dehydration, oral fresh water or infusion of 5% glucose solution; For those who lose more water than sodium, while giving priority to hydration, sodium should be supplemented appropriately. In principle, replenish water first and then sodium, usually two 5% glucose solutions and one physiological saline. (2) Hypoosmotic dehydration, also known as secondary dehydration or hyponatremia accompanied by extracellular fluid reduction, is characterized by more sodium loss than water loss, serum sodium concentration 20mo1/L); If it is caused by extrarenal causes, the renal blood flow decreases and the blood sodium concentration decreases when the blood volume is low, and the RAA system is activated, which directly stimulates the adrenal cortex glomeruli, increases the secretion of ADS, and increases the sodium reabsorption of renal tubules, resulting in the decrease of urinary sodium content (< 10 MMO 1/L). (5) Due to the decrease of extracellular fluid, the plasma volume also decreases, which makes the blood concentrate and the plasma colloid osmotic pressure increase, leading to interstitial fluid entering the blood vessels to replenish the blood volume. As a result, the reduction of tissue fluid is more obvious, so the patient's skin elasticity is lost, the eye socket and the baby's fontanel are sunken, and obvious dehydration occurs. 3, the principle of prevention and treatment to prevent the primary disease, remove the cause. Generally, isotonic sodium chloride solution should be used to replenish blood volume in time. Severe cases can be given hypertonic sodium chloride solution (3 ~ 5%), followed by 5% or 10% glucose solution. If shock has occurred, it should be rescued in time. (3) Isoosmotic dehydration Isoosmotic dehydration is also called mixed dehydration or reduction of extracellular fluid with normal blood sodium concentration. It is characterized by the proportional loss of water and sodium, the serum sodium concentration is 130 ~ 150 mmol/L, and the plasma osmotic pressure is 280 ~ 310 mosm/l ...1.Causes and mechanisms Any isotonic loss of body fluids and insufficient isotonic sodium chloride solution for hypotonic dehydration may lead to this type. (l) Acute loss of digestive juice: gastrointestinal fluids, especially small intestinal fluids, are isotonic fluids, and severe diarrhea, small intestinal fistula, small intestinal obstruction or drainage can all cause the loss of isotonic fluids. (2) The formation of a large number of pleural effusion and ascites. (3) extensive burns, severe trauma, etc. Causing plasma loss. 2. Pathophysiological changes (l) Because the extracellular fluid is lost first, the blood volume and tissue fluid are lost, but the osmotic pressure of the extracellular fluid is normal, and the intracellular fluid does not transfer to the outside of the cell, so the intracellular fluid amount does not change much. (2) The decrease of effective circulating blood volume increases the secretion of ADS and ADH, increases the reabsorption of sodium and water by renal tubules, replenishes extracellular fluid to some extent, and at the same time reduces urine volume and increases urine specific gravity. (3) The blood volume of severe patients decreases rapidly and obviously, which may be accompanied by shock. (4) If it is not treated in time, it can be transformed into hypertonic dehydration by continuous dehydration through non-inductive evaporation; If only water is supplemented without sodium, it can be converted into hypotonic dehydration. Isoosmotic dehydration has no specific clinical manifestations, including hypertonic dehydration and hypotonic dehydration. Mild symptoms are mainly manifested as loss of salt, such as anorexia, nausea, fatigue, thirst, oliguria, dry oral mucosa, sunken eye sockets and decreased skin elasticity. In severe cases, the main manifestation is peripheral circulation failure. 3, the principle of prevention and treatment to prevent the primary disease, remove the cause. The osmotic pressure of hypotonic sodium chloride solution should be 1/2 ~ 2/3 of that of isotonic solution.