① The osmotic pressure of extracellular fluid increases ② The blood pressure and volume decrease ③ The secretion of angiotensin II increases, which excites the thirst center and causes thirst, and vice versa inhibits it.

① Increase in extracellular fluid osmotic pressure stimulates osmoreceptors ② Decrease in effective circulating blood volume stimulates volume receptors

Increased ADH secretion increases the water permeability of the renal distal convoluted tubule and collecting duct, thereby increasing water reabsorption, and ultimately the extracellular fluid volume increases and the osmotic pressure decreases.

① Decrease in effective circulating blood volume ② Hyponatremia and hyperkalemia will increase ALD secretion, increase renal reabsorption of water and sodium, and ultimately increase extracellular fluid volume.

① Diuretic and natriuretic effects ② Antagonize the renin-aldosterone system ③ Inhibit ADH secretion and antagonize ADH effects.

Gastrointestinal tract skin loss, skin loss, renal sodium loss, fluid accumulation in the third space

Paralytic intestinal obstruction, massive drainage of pleural effusion and ascites, congenital malformations of the digestive tract of newborns, etc.

ECF osmotic pressure is normal, serum sodium concentration is normal

Massive loss of ECF → Decrease in blood volume and tissue fluid volume. No significant change in ICF

Increased secretion of ADH and ALD → enhanced renal reabsorption of sodium and water → reduced urine output

Simple water loss: ① Water loss through the skin, such as hyperthyroidism, etc. ② Water loss through the kidneys: such as diabetes insipidus. ③ Water loss through the lungs: such as increased evaporation of the respiratory tract caused by hyperventilation.

Water loss is greater than sodium loss, that is, loss of hypotonic fluid: ① Some infants and young children have diarrhea and gastrointestinal fluid loss (low to moderate loss of isotonic fluid) ② Profuse sweating ③ Loss of hypotonic urine through the kidneys, such as hypertonic glucose diuresis , draining more water than sodium.

(sense of thirst, oliguria, transfer of intracellular fluid to extracellular, central nervous system dysfunction, changes in urinary sodium, dehydration fever)

Dehydration fever: due to less evaporated water from the skin, the body's heat dissipation is affected, causing the body temperature to rise. It is not a fever, but a passive increase in body temperature (overheating).

Decreased ECF amount → Decreased blood volume → Decreased pulse speed and blood pressure (late symptoms)

Increased ECF osmotic pressure: ① Increased blood sodium concentration and plasma osmotic pressure ② Increased ADH secretion → increased renal reabsorption of water → high oliguria and high specific gravity ③ Intracellular dehydration → CNS dysfunction → hallucinations and agitation ④ Acts on the thirst center → Thirsty

Reduced skin evaporation → dehydration fever

Gastrointestinal loss: The most common cause is the loss of a large amount of digestive juices while only replenishing water

Skin loss: ① After sweating profusely, only replenish water; ② After large area burns, only replenish water

Renal sodium loss: ① Natriuretic diuretics ② Polyuretic stage of acute renal failure ③ "Salt-losing nephritis" ④ Addison's disease

(Easily prone to shock, obvious signs of dehydration, changes in urine output, and changes in urinary sodium)

Plasma osmotic pressure decreased and early urine output was normal.

Decreased ECF osmotic pressure: ① Decreased blood sodium concentration and plasma osmotic pressure ② Decreased secretion of ADH → Decreased renal reabsorption of water → Normal urine output (early stage) ③ Water moves into cells → Swelling of brain cells → Apathy and lethargy, which is also a factor in the decrease in ECF volume reason.

Decrease in ECF amount: ① Decreased blood volume (decreased pulse speed, blood pressure, venous collapse) → Decreased renal blood flow → Increased secretion of ALD and ADH → Oligouria, azotemia, and decreased urinary sodium (late stage) ② Direct induction of ADH and ALD Increased synthetic secretion ③ Decreased tissue fluid → dehydration

According to the cause: ① cardiac; ② hepatic; ③ renal; ④ inflammatory (not limited to unilateral); ⑤ allergic; ⑥ idiopathic

By location: ① subcutaneous edema; ② laryngeal edema; ③ papilledema; ④ pulmonary edema; ⑤ cerebral edema

According to scope: ① Local; ② Systemic

According to the existence status of edema fluid: ① Overt edema, also known as pitting edema. No inflammatory reaction; ② latent edema, invisible on the outside; ③ myxedema, accompanied by inflammatory reaction.

Basic factors affecting tissue fluid production and reflux

Abnormal fluid exchange inside and outside blood vessels, tissue fluid production > reflux: ① Increased capillary fluid hydrostatic pressure ② Decreased plasma colloid osmotic pressure, affecting intake, synthesis, and loss ③ Increased microvascular wall permeability, generally seen in inflammatory immune reactions. Pay attention to the difference between transudate and transudate ④ Lymphatic reflux disorder.

Imbalance of fluid exchange inside and outside the body - water and sodium retention: 99%~99.5% is reabsorbed by the renal tubules, of which the proximal tubule absorbs 65%~70%, and the final filtration is 0.5%~1%. ① Decreased glomerular filtration rate: affected by three aspects: decreased filtration area, effective circulating blood volume, and renal blood flow ② Increased renal tubular reabsorption: affected by far There are three effects: increased reabsorption in the convoluted tubules and collecting ducts (increased reabsorption in the distal convoluted tubules and collecting ducts), redistribution of intrarenal blood flow, and increased reabsorption in the proximal convoluted tubules (imbalance of tubular balance).

Take common generalized edema as an example: cardiac edema is caused by right heart failure; while left heart failure causes cardiogenic pulmonary edema.

Cardiac edema first occurs in the sagging area due to the effect of gravity. Generally speaking, "swelling below the heart (ankles) and above the kidneys (head, face, eyelids)"

Reduced water excretion: seen in acute and chronic renal dysfunction, etc. Due to the sharp reduction in renal drainage function or the reduction in effective circulating blood volume and renal blood flow → the renal drainage volume is greatly reduced. If the water load is increased, poisoning may easily occur;

Excessive ADH secretion: ① Stress: sympathetic nerve ( ), parasympathetic nerve (-) ② Abnormal increase in ADH secretion, increased ADH or ADH substances ③ Drugs: isoproterenol, etc. promote ADH secretion/enhancement of effects ④ Others: a. Effective Circulating blood volume decreases, vagus nerve ( ), ADH secretion increases; b. Adrenocortical hypofunction, adrenocortical hormone (-), hypothalamus secretion of ADH is inhibited (-).

Excessive water intake: In the late stage of hypotonic dehydration, extracellular fluid → intracellular fluid shifts. If a large amount of water is input, excessive water intake will occur.

Due to water retention, ECF volume increases and ECF osmotic pressure decreases: blood sodium decreases and blood is diluted; water moves into cells: ① ICF osmotic pressure decreases and ICF volume increases; ② Brain cell edema → lethargy, restlessness, and brain herniation.

The amount of fluid inside and outside the cells increases, and the osmotic pressure both inside and outside the cells decreases. The osmotic pressure of the extracellular fluid decreases more significantly. The osmotic pressure inside is always greater than outside, and cell edema continues to intensify. The main site of water retention is inside the cells; it is the most harmful to the body. It's cerebral edema.

Depolarization block: The phenomenon that the resting potential is equal to or close to the threshold potential (Na channel inactivation) reduces cell excitability.