Section II: Disorders of Water and Sodium Metabolism

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Section II Disorders of Water and Sodium
Metabolism
2
?? Classification

• According to the changes of volume
• 1. Dehydration
• 2. Overhydration
• According to the changes of Nae
• 1. Hypernatremia
• 2. Hyponatremia
• 3.Normonatremia with changes of volume

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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)

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??Dehydration
5
Dehydration?? (Hypovolemia)

• Concept The volume of body fluid
  decreases below the normal range after the loss
  of body fluid.
• In dehydration the Nae may be in three
  manifestations
• --------------------------------------------------
  -------------
• Dehydration Na Osmotic
  pressure
• (mmol/L)
  (mOsm/L)
• --------------------------------------------------
  -------------
• Hypertonic gt150 gt
  310
• Hypotonic lt130 lt
  280
• Isotonic 130150 280
  310
• --------------------------------------------------
  ------------

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1 Hypertonic Dehydration

• (1) Concept
• (2) Causes
• (3) Adaptive (compensatory) responses of the
• body
• (4) Characteristic effects
• (5) Principle of treatment

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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.

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(2) Causes

• 1) Decreased water intake can be seen in
• ? No water during navigation or in
  desert.
• ? No sense of thirst due to brain injury
  or coma,
• ? Severe vomiting
• ? Difficulty in swallowing because of
  esophageal diseases.
• ? 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.

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• 2) Increased loss of water
• ?via skin
• ?via respiration
• ?via gastrointestinal tract
• ?via 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
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? 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 (0.2NaCI),
  there will be more water loss than salt loss
  during sweating.
• If water replenish is not enough.

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? 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.

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? 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 of watery stool is about
  60 mmol/L (hypotonic fluid).
• If water replenish is not enough.

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? 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.

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(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.
  

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increase of ECF osmolality (12)
elevated angiotensin II vasoconcentration
dryness of mouth
hypovolemia
osmoreceptor (anterior hypothalamus)
volume receptor in venae cavae and atrium
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

• no thirst

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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.

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increase of ECF osmolality (12) via osmoreceptor
hypovolemia via volume receptor
synthesis and release of ADH
increases the reabsorption of water in kidneys
decrease osmolality of ECF
increase volume of ECF
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3)Shift of water
Increase of blood volume by shift of
water from intracellular space.
ECF
ICF
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(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. (lt400500 ml/day).
• Metabolic wastes like urea and uric
  acid are retained in the body because of the
  oliguria.
• Urea and uric acid are harmful to
  the body. (azotemia)
• Urine specific gravity is
  increased.
• Na in urine???

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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
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• 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.

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4) Intracellular dehydration

• Water will shift from ICF to ECF
  because the ECF is hypertonic. All the cells will
  shrink.

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• 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

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• 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?

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(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.

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4) How to decide the volume of fluid replacement?

• --------------------------------------------------
  ------------------------------
• Degree Volume of water loss
  clinic manifestation
• ( of body weight)
• --------------------------------------------------
  ------------------------------
• Mild 25
  thirst, oliguria
• Moderate 510
  severe thirst
• 
  fever
• 
  dryness of mucosa
• Severe 1015
  delirium, stupor,
• 
  coma
• --------------------------------------------------
  -----------------------------

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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 (Nalt130
  mmol/L), the osmolarity is lower than 280mOsm/L.

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(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
  (Addisons disease) can cause excessive renal
  loss of sodium because the secretion of
  aldosterone is reduced.
• 3) Some diuretics (e.g. Furosemide??)
  inhibit the Na reabsorption in renal tubules.

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(3) Adaptive responses

• Aldosterone secretion is stimulated by
  the low sodium concentration, except in the case
  of adrenocortical insufficiency.

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(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.

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

ICF
ECF
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• 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)

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• 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.

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• 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)

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• 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 ?

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(5) Principles of treatment

• Replacement of isotonic saline
  (0.9NaCl) .
• 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. 

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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 130150 mmol/L,
• the osmolarity is 280310 mOsm/L.

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(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.
•  

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(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)

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(4) Effect on the body

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

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

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(5) Principle of treatment

• Hypotonic saline is needed to replace the
  fluid deficiency.
• Isotonic NaCl first.

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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
• pH7.21, PaCO226 mmHg
• PaO2 108 mmHg. Na135 mmol/L
• K 3.0 mmol/L HCO3- 16 mmol/L
• Urine pH5.0, Specific gravity
  1.028 

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• The patients problems were
• (1)isotonic dehydration
• (2)metabolic acidosis
• (3)hypokalemia.

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• 2. ????
• ??,3??,???1????????,?????20????????????39.8?,
  ??,????,????,??????????,??????1200ml???????,???,?
  ??,??,??,????????

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?? Overhydration

• According to the Na concentration
• Hypertonic overhydration
• (2) Hypotonic overhydration
• (Water intoxication)
• (3) Isotonic overhydration (Edema)

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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.

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(2) Causes

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

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• Chicago Daily News Aug. 9, 1958
  reported that the worlds 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 ???

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

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2) Decreased water output

• ? Oliguria due to low renal blood flow
  ( in congestive heart failure,cirrhosis).
• ? Oliguria due to excessive secretion of
  ADH
• Several factors can stimulate the ADH
  secretion, like fear, stress, anesthesia, pain
  and some drugs (e.g. morphine and meperidine),

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? Syndrome of inappropriate secretion of ADH
(SIADH)

• Causes of SIADH are
• pulmonary diseases (viral and bacterial
  pneumonias, tuberculosis, fungal infection, lung
  abscess),
• diseases of central nervous system (
  brain tumor, brain abscess, encephalitis and
  meningitis),
• tumors of lung, pancreas, thymus and
  duodenum (ectopic ADH synthesis)
• At the same time, fluid intake (intravenous
  or oral) is not carefully controlled.

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(3) Effects on the body

• (a) Dilutional hyponatremia
• Low serum protein concentration.
• Low serum osmosity
• Increased blood volume.
• (b) A rapid weight gain in acute water
  intoxication,
• (c) Cellular overhydration of central nervous
  system.
• Anorexia, nausea, vomiting
• Muscular weakness and twitching
• Mental disturbances, convulsive
  seizures, stupor, and coma.
• (d) Peripheral and pulmonary edema
•  

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5) Principle of treatment

• (a) Restriction of water intake
• (b) Diuretics to excrete the excessive
  water
• (c) Hypertonic saline (3NaCl) for severe
  case, to raise the osmolarity of ECF quickly, to
  start the movement of water from the cells into
  extracellular space, then excretion from kidneys.

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Case discussion

•   A 25-year-old male has a head injury and
  unable to eat. He received 45 L of 5glucose per
  day to replace his fluid losses and for
  nutritional purposes. On the 5th day he
  experienced convulsions and coma. The followings
  are his laboratory findings.

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• --------------------------------------------------
  ----------------------------------------
• Day Body weight PlasmaNa Plasma
  osmolarity
• (Kg) (mmol/L)
  (mOsm/L)
• --------------------------------------------------
  -----------------------------------------
• O 75 140
  300
• 1 76 137
  295
• 2 78 130
  280
• 3 79 125
  270
• 4 80 120
  260
• 5 82 115
  250
• --------------------------------------------------
  ---------------------------------------
• Questions
• (1)What is the problem (pathological
  process) he had?
• (2) Is this the normal response to
  intravenous infusion of
• 5GS?
• (3)What is the reason of convulsion and
  coma?