Phathophysiology2(water And Electrolytes Balance And Imbalance)

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Water and Electrolytes Balance and Imbalance

DURGE RAJ GHALAN [email protected]

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Contents ✠ Disorders of Water & sodium metabolism ✠ Disorders of potassium metabolism ✠ Disorders of magnesium metabolism ✠ Disorders of calcium & phosphorus metabolism 3

After completing this chapter, you should be able to  Describe mechanisms which maintain normal water and sodium balance  Predict changes in the volume and osmolality of the fluid compartments in response to gain or loss of water or Saline  Explain the pathogenesis and consequences of hypotonic and hypertonic dehydration  Outline the basic mechanisms of edema

Water balance

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2.1

Water and Sodium Balance

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Distribution of body fluid(BF) ICF 40%

BF 60%

plasma 5% ECF 20% Interstitial fluid 15%

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Electrolyte in BF Na

Na Cl

K

Na Cl

HCO3

HCO3

HPO4

HPO4

SO4

Organic acid

Ca Mg Pr

plasma

K

SO4

Organic Ca Mg acid

Interstitial fluid

K

HCO3

HPO4 Ca

SO4

Mg

Pr

ICF

Multiple choice questions of type A The major cation in plasma is A.Na+               B.K +         C.Ca2+             D.Mg2+ E.Fe2+  

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H2O

Osmolality↑

H2O

Osmolality↓

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Osmolality of BF •Directly related to the concentration of solutes in the solution •The higher the solute concentration, the greater the osmotic pressure and the greater the tendency of water to move into the solution

Normal OPP ＝ cation(151) ＋ anion(139) ＋ nonelectrolyte (10) ＝ 300mmol/L(280 ～ 310mmol/L)

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A

B

(A) Addition of water to the E

I

E

I

body

concentration

(B) Addition of hypertonic salt C

solution

D E

I

E

I

(C) Addition of isotonic salt solution (D) loss of sodium chloride

Volume

Changes in volume and osmolality of intracellular(I) and Extracellular (E) fluids.

Regulation of Water & Sodium Balance Water balance Sodium balance Regulation of Volume & Osmolality of BF

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Water balance

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Sodium (Na +) ❚ most abundant cation in ECF ❚ creates osmotic pressure of ECF ❚ N=130-150 mmol/L ❚ essential for electrical activity of neurons and muscle cells 16

Sodium balance ❚ Intake: 100-200 mmol/day ❚ Output : urine, sweat ❚ Sodium balance is regulated by kidney

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Volume & Osmolality regulation of BF ADH

variation of BF vol

aldosterone ANP

variation of OPP

Thirst center ADH

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Regulation of Water Intake

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Regulation effects of ADH (antidiuretic hormone)

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Renin-Angiotensin-Aldosterone System

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summary water

volume

sodium

osmolality

Thirst center

↑Intake

↑

-

ADH

↓Output

↑

-

↓

RAAS

↓Output

↑

↑reabsorption

normal

ANP

↑output

↓

↓ reabsorption

normal

↓

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2.2

Disorders of Sodium and Water Metablism

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Classification of H2O & Na disorders

volume

Serum sodium concentration Hyponatrem ia hypernatremia Normal <130mmol/ >150mmol/L L

hypovolemic Hyponatremia

hypovolemic

hypovolemic hypernatremia

Isotonic dehydration

hypervolemi hypervolemic Hyponatremia c

hypervolemic hypernatremia

edema

nomovolemi nomovolemic Hyponatremia c

nomovolemic hypernatremia

normal 26

hyponatremia ❚

serum sodium ＜ 130 mmol/L ↓ ECF Osmolality ＜ 280 mmol/L ↓

thirsty ↓

↓ intake↓

ADH ↓

↓ output↑

water redistribution

↓ cellular swelling

ECF Osmolality ↑volume ↓ 27

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Ture or false

Hyponatremia=loss of sodium ?

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hyponatremia ❚

hypovolemic hyponatremia

❚

hypervolemic hyponatremia

❚

nomovolemic hyponatremia

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hypovolemic hyponatremia (hypotonic dehydration)

Definition Causes & mechanism Effects Principles of therapy

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Definition 　　 sodium loss > water loss 　　 serum sodium ＜ 130 mmol/L 　　 OPP ＜ 280mmol/L

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Causes & mechanism ❚ renal loss Diuretics

❚ ex- renal loss

Adrenal insufficiency

GI tract(diarrhea, vomiting or

Renal disease

gastric suction)

renal tubule acidosis Renal output of Na

Third space (hydrops) Skin (burn or sweating)

and H2O ↑

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Effects ECF

OPP

circulatory failure 　 shock Bl vol↓ 　 aldo↑→ UNa↓ 　　　　　 ADH ↑→oliguria interstitial fluid↓→sign of dehydration 　 Thirst ↓ →water intake↓ ADH ↓ → renal output↑ ICF →ECF↓

 Caused

by renal factors ， UNa↑ 34

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Principles of therapy ❚

Treat underlying cause

❚

Restoration the vol of ECF

❚

Treat complication

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Multiple choice questions of type A loss of BF caused by hypotonic dehydration exists in A. extracellular fluid    

 B. plasma

C. interstitial fluid

D. intracellular

fluid E. both ECF and ICF 37

hypernatremia ❚

serum sodium >150 mmol/L ↓ ECF Osmolality ＞ 310 mmol/L ↓ thirsty ↑ ADH ↑ water redistribution ↓ ↓ ↓ intake ↑ output↓ cell dehydration

ECF Osmolality ↓ volume ↑ 38

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hypernatremia ❚

hypovolemic hypernatremia

❚

hypervolemic hypernatremia

❚

Isovolemic hypernatremia

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hypovolemic hypernatremia (hypertonic dehydration)

Definition Causes & mechanism Effects Principles of therapy

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Definition 　　 water loss > sodium loss 　　 serum sodium >150 mmol/L 　　 OPP > 310mmol/L

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Causes & mechanism ❚ Water intake↓ Unavailability of water Thirst ↓ Unable to drink

❚ Water output↑ air tube Skin kidney GI tract

ADH secretion↓ diuretics high protein diet

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Effects

ECF

OPP

　　　　　 aldo↑→ oliguria Bl vol↓ 　　　　　　 　　　　　 ADH ↑→oliguria UNa↑ Interstitial fluid↓→sign of dehydration 　 thirst→water intake↑ ADH ↑ → oliguria ICF ↓ →brain cell dehydration →CNS disorders

Twitching, somnolence, respiratory paralysis 44

Principles of therapy ❚

Treat underlying cause

❚

Restoration vol of ECF

❚

Adding NS

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Comparison between hypotonic and hypertonic dehydration hypotonic

hypertonic

The thirst sensation

↓

↑

Urine output

↑

↓

hypovolemic shock

√

+

Effects of CNS

-

√ 46

Multiple choice questions of type A Shock is often caused by which of the following disorder of water and electrolytes A.   B. C. D. E.

hypotonic dehydration      hypertonic dehydration isotonic dehydration water intoxication hypokalemia 47

2.2 Edema

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Edema ❚

Definition

❚

Pathogenesis of edema

❚

Effects of edema

❚

Principles of therapy

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Definition ❚ Fluid accumulation in the interstitial compartment

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Types of edema ❚ Extent

　 anasarca 　 local edema

❚ causes

　 cardiac edema/renal edema/hepatic edema/ 　　 nutritional edema/inflammatory edema/ lymphatic edema

❚ location

　 cutaneous dropsy/brain edema/ pulmonary edema

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Pitting edema

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nutritional edema

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Pathogenesis of edema Imbalance of fluid interchange across capillaries

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Pathogenesis of edema ❚

the increased renal retention of sodium and water glomerular Filtration rate ↓ (glomerulopathy /circulation volume ↓) Augmented filtration fraction(FF) Release of aldosterone and ADH ↑→Water and sodium reabsorb in renal tubules ↑ 57

Effects of edema 　 ❚ Benificial effects Protective effects of inflammatory edema

❚

Harmful effects Nutritional disturbance Effects on functions of organs and tissues

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CASE PRESENTATION ❚ An 84-year-old woman was brought to the hospital because she was lethargic and refused to drink. On admission, she weighed 60 kg. Her blood pressure was 100/60mmHg with a pulse of 110 per minute and poor skin turgor. laboratory examination revealed a BUN of 100mg/dl, sodium of 170mEq/L, potassium of 4.0Eq/L, and CO2 of 24mmol/L. serum creatine was 2.5mg/dl. Urinalysis showed a specific gravity of 1.030, no protein, glucose, or acetone was present. urine sodium was 5mEq/L and urine osmolality 59 726mOsm/L.

Questions ❚ What kind of disorders of water and sodium metabolism happened to this patient? ❚ What’s the primary reason for the water and sodium imbalance?

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