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Section II: Disorders of Water and Sodium Metabolism

Section II: Disorders of Water and Sodium Metabolism. 一、 Classification. According to the changes of volume: 1. Dehydration 2. Overhydration According to the changes of [Na + ]e: 1. Hypernatremia 2. Hyponatremia 3.Normonatremia with changes of volume.

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Section II: Disorders of Water and Sodium Metabolism

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  1. Section II: Disorders of Water and Sodium Metabolism

  2. 一、 Classification According to the changes of volume: 1. Dehydration 2. Overhydration According to the changes of [Na+]e: 1. Hypernatremia 2. Hyponatremia 3.Normonatremia with changes of volume

  3. According to the clinic importance: (1) Dehydration 1) Hypertonic dehydration 2) Hypotonic dehydration 3) Isotonic dehydration (2) Overhydration 1) Hypertonic overhydration 2) Hypotonic overhydration (Water intoxication) 3) Isotonic overhydration (Edema)

  4. 二、Dehydration

  5. Dehydration脱水 (Hypovolemia) Concept: The volume of body fluid decreases below the normal range after the loss of body fluid. In dehydration the [Na+]e may be in three manifestations: --------------------------------------------------------------- Dehydration [Na+] Osmotic pressure (mmol/L) (mOsm/L) --------------------------------------------------------------- Hypertonic >150 > 310 Hypotonic <130 < 280 Isotonic 130~150 280~ 310 --------------------------------------------------------------

  6. 1 Hypertonic Dehydration (1) Concept (2) Causes (3) Adaptive (compensatory) responses of the body (4) Characteristic effects (5) Principle of treatment

  7. 1 Hypertonic Dehydration (1) Concept Both water and sodium are lost (hypovolemia), but the water loss is in excess of salt loss. Then the volume of ECF is reduced, the [Na+] is over 150 mmol/L, the plasma osmotic pressure is over 310 mOsm/L.

  8. (2) Causes 1)Decreased water intake can be seen in: ① No water during navigation or in desert. ② No sense of thirst due to brain injury or coma, ③ Severe vomiting ④ Difficulty in swallowing because of esophageal diseases. ⑤ Underdose of infusion in treatment of patients At the same time, pure water loss from lung (300ml/d) and skin (500ml/d) is not avoidable, even increased.

  9. 2) Increased loss of water ①via skin ②via respiration ③via gastrointestinal tract ④via kidney, gains (ml/day) loss (ml/day) ------------------------------------------drink 1200 lung 300 food 1000 skin 500 metabolic feces 200 water 300 urine 1500 ------------------------------------------ total 2500 2500

  10. ① via skin: Normally 500 ml of pure water will be lost by insensible evaporation from skin each day. When the environmental or body temperature is increased, the evaporation (insensible loss) will increase from skin. Elevation of 1℃(celsius) will increase loss of 500 ml pure water by evaporation each day. Since sweat is hypotonic (0.2%NaCI), there will be more water loss than salt loss during sweating. If water replenish is not enough.

  11. ② via respiration: Since the expired air contains water vapour, the water loss from lung is 300 ml of pure water each day. The pure water loss is increased to 1300ml/day. during hyperventilation. (metabolic acidosis, bronchitis, fever) If water replenish is not enough.

  12. ③ via gastrointestinal tract Vomiting and diarrhea will lose a lot of body fluid. Gastric juice is isotonic, loss of gastric juice with the loss of pure water from skin and lung may lead to hypertonic dehydration. The [Na+] ofwatery stool is about 60 mmol/L (hypotonic fluid). If water replenish is not enough.

  13. ④ via kidney: When the ADH secretion is reduced, such as diabetes insipidus. Increased water loss occurs. Patients with diabetes also have increased urinary water loss due to the osmotic diuresis. Tube feeding with a high concentration of protein is used to unconscious (coma) patients. The urea will increase in the urine, which causes osmotic diuresis. If water replenish is not enough.

  14. (3) Adaptive (compensatory) responses of the body 1) Drink more water because of severe thirst Hyperosmolarity and hypovolemia stimulate the sense of thirst. Diminished saliva and the dry mucous membranes lead to the sense of thirst. Obvious thirst occurs at early stage of hypertonic dehydration. If possible, the patient may drink water until the patient has again normal osmolarity and normal volume of ECF.

  15. increase of ECF osmolality (1~2%) elevated angiotensin II vasoconcentration dryness of mouth hypovolemia osmoreceptor (anterior hypothalamus) volume receptor in venae cavae and atrium • no thirst thirst center (anterior hypothalamus) sense of thirst and drink of water decrease of ECF osmolality increase of ECF volume decrease of angiotensin concentration II disappear of dryness of mouth

  16. 2) Increased water reabsorption by increased ADH ADH release is stimulated by the hyperosmolarity of the ECF and the hypovolemia. ADH increases the reabsorption of water in kidneys. The volume of ECF will increase. The high osmolarity will decrease to normal.

  17. increase of ECF osmolality (1~2%) via osmoreceptor hypovolemia via volume receptor synthesis and release of ADH increases the reabsorption of water in kidneys increase volume of ECF decrease osmolality of ECF

  18. 3)Shift of water Increase of blood volume by shift of water from intracellular space. ECF ICF

  19. (4) Characteristic effects of hypertonic dehydration on the body 1)Thirst occurs at the early stage of hypertonic dehydration. 2) Oliguria occurs at the early stage of hypertonic dehydration. (<400~500 ml/day). Metabolic wastes like urea anduric acidare retained in the body because of the oliguria. Urea anduric acidare harmful to the body. (azotemia) Urine specific gravity is increased. Na+ in urine???

  20. renal blood flow [Na+] in macula densa excitement of sympathetic nerve renin release from the juxtaglomerular cells increase of angiotensin II releases [K+], [Na+] blood flow in plasma aldosterone secretion from adrenal cortex Na+ reaborption in renal tubules K+ and H + excretion from kidneys

  21. 3) Fever Fever may be present because water is necessary to regulate the body temperature. Fever is more severe in infants because of the dysfunction of thermoregulatory center, which is called infantile dehydration fever.

  22. 4) Intracellular dehydration • Water will shift from ICF to ECF because the ECF is hypertonic. All the cells will shrink.

  23. Brain cell dehydration produces brain dysfunction like lethargy (weakness, apathy, absence of interest), which may progresses to coma (unconsiousness) when the water deficient is severe. • Increased irritability (muscular twitch, delirium) may occur, especially in children. • Twitch: uncontrollable sudden, quick movement of muscle • Delirium: violent mental disturbance accompanied by wild talk (wild excitement) • Subarachnoid hemorrhage

  24. 5) loss of body weight Loss of body weight occurs within short period of time, which is useful in diagnosis of severity of dehydration. 6) blood concentration (hemoconcentration) Count of WBC ↑ Count of RBC ↑ Hb (hemoglobin) ↑(in total blood, RBC) Hematocrit ↑(percentage of RBC in total blood) use in diagnosis?

  25. (5) Principle of treatment 1) Treat the primary disease, such as diarrhea. 2) Replace firstly with 5% glucose solution to reduce the hyperosmolarity and to increase the volume of ECF. 3) Add small amount of 0.9% NaCl after infusion of 5% glucose solution.

  26. 4) How to decide the volume of fluid replacement? -------------------------------------------------------------------------------- Degree Volume of water loss clinic manifestation (% of body weight) -------------------------------------------------------------------------------- Mild 2~5% thirst, oliguria Moderate 5~10% severe thirst fever dryness of mucosa Severe 10~15% delirium, stupor, coma -------------------------------------------------------------------------------

  27. 3 . Hypotonic Dehydration (1) Concept There is loss of both water and sodium (hypovolemia),the Na+ loss is in excess of water loss, The ECF is hypotonic ([Na+]<130 mmol/L), the osmolarity is lower than 280mOsm/L.

  28. (2) Causes 1) Replace of water only to the patients with dehydration caused by vomiting, diarrhea, gastric suction and excessive sweating lost. 2) Adrenocortical insufficiency (Addison’s disease) can cause excessive renal loss of sodium because the secretion of aldosterone is reduced. 3) Some diuretics (e.g. Furosemide速尿) inhibit the Na+ reabsorption in renal tubules.

  29. (3) Adaptive responses • Aldosterone secretion is stimulated by the low sodium concentration, except in the case of adrenocortical insufficiency.

  30. (4) Characteristic effect of hypotonic dehydration on the body 1) Urine volume Urine volume is variable (low, normal, high) depending on the ADH secretion. At the early stage of hypotonic dehydration, decreased osmolarity is the superior change, which inhibits ADH secretion, the urine is increased. At the late stage, severe hypovolemia is the superior change, which increase the ADH release . the urine volume is decreased.

  31. 2) Water shifts into the cells from ECF. Severe hypovolemia (Compare with hypertonic dehydration.) ICF ECF

  32. 3) Hypotension The blood pressure may decrease. Postural hypotension and shock will occur because the decreased blood volume. (increased urine and water shifts into the cells)

  33. 4) Severely reduced interstitial fluid Low protein concentration and colloid osmotic pressure in interstitial space. The reduce of skin elasticity Eyeball tension is decreased, the eyeballs are soft and sunken.

  34. 5) Intracellular overhydration • Water will shift from ECF to ICF because the ICF is relatively hypertonic. The cell will swell. • Brain cell overhydration produces brain dysfunction. (Cranial cavity is fixed) • (severe headache, high brain pressure)

  35. 5) There is no obvious thirst at early stage because of the low crystal osmotic pressure. 6) Blood concentration Counts of WBC and RBC ? Hematocrit ? Plasma protein concentration ? Hb in plasma ? Hb concentration in RBC ?

  36. (5) Principles of treatment • Replacement of isotonic saline (0.9%NaCl) . • Replacement of hypertonic fluid may lead to hypertonic state. • Pure water is easy to loss via skin and lung. • Hyperosmotic fluid are seldom used, except in urgent state of brain edema.

  37. 4. Isotonic Dehydration • (1) Concept • There is loss of fluid (dehydration), the water loss is equal to salt loss. The ECF in the body is isotonic, • the [Na+] is 130~150 mmol/L, • the osmolarity is 280~310 mOsm/L.

  38. (2) Causes 1) Loss of fluid is caused by vomiting, diarrhea, hemorrhage and from the burned area. 2) The isotonic dehydration can be induced from hypertonic and hypotonic dehydration by the renal regulation.

  39. (3) Adaptive responses The main change in isotonic dehydration is the reduced volume of ECF. 1) It stimulates the thirst, so that the patient will ask to drink water to replace the volume of ECF. (not as strong as hypertonic dehydration) 2) ADH release is stimulated, so that the water reabsorption will increase to replace the volume of ECF.(not as much as hypertonic dehydration) 3) Secretion of aldosterone is increased due to hypovolemia.(not as much as hypotonic dehydration)

  40. (4) Effect on the body • 1) Urine volume is diminished because of the decreased GFR, increased ADH and aldosterone secretion. • 2)Thirst • 3) Poor skinelasticityand sunken eyeball, because of the reduction of interstitial fluid. • 4) No water shift and related symptoms and signs.

  41. Turn into hypertonic dehydration ( loss pure water) or to hypotonic dehydration (replacement of water only).

  42. (5) Principle of treatment Hypotonic saline is needed to replace the fluid deficiency. • Isotonic NaCl first.

  43. Case Discussion No.1 A 36-year-old man was hospitalized with a 3-day history of fever and watery diarrhea. His blood pressure was 90/60 mmHg, the pulse was 112/min, temperature is 38.0℃. The abdomen was distended with low skin elasticity. The laboratory results were: Arterial blood: pH=7.21, PaCO2=26 mmHg PaO2= 108 mmHg. [Na+]=135 mmol/L [K+] =3.0 mmol/L [HCO3-] = 16 mmol/L Urine: pH=5.0, Specific gravity= 1.028

  44. The patient’s problems were: • (1)isotonic dehydration • (2)metabolic acidosis • (3)hypokalemia.

  45. 2. 病例分析 • 患婴，3个月，入院前1天开始发热。呕吐，水样便每日20余次。伴烦躁、烦渴。查体：39.8℃, 嗜睡，醒后烦躁，皮肤干热，明显腹胀。治疗：抗菌素，输入生理盐水1200ml。次日病情加重，极烦渴，呼吸深，惊厥，昏迷，并发肠麻痹死亡。

  46. 三、 Overhydration • According to the [Na+] concentration: • Hypertonic overhydration • (2) Hypotonic overhydration • (Water intoxication) • (3) Isotonic overhydration (Edema)

  47. 1. Water intoxication (1) Concept Excessive fluid in the body is called overhydration. Excessive hypotonic fluid in the body is called hypotonic overhydration (water excess, dilutional hyponatremia ). Severe water excess causes a serial of symptoms and signs, and is called water intoxication.

  48. (2) Causes The main causes are excessive water intake and less loss of water. 1) Excessive water intake ①Excessive venous infusion of 5% glucose solution. ②Excessive water intake of psychotic disturbances (e.g. schizophrenia) may cause water intoxication.

  49. Chicago Daily News Aug. 9, 1958 reported that the world’s water drinking champion (1935) drank 20 L of water within 30 min, and was awarded a “hose”. It is obvious that this champion is healthy (without water intoxication). Excessive water intake only can not lead to the water intoxication . The reason is ???

  50. At the same time, the kidneys cannot eliminate the excessive water.

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