phathophysiology2(water and electrolytes balance and imbalance)

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Water and Electrolytes Balance and Imbalance

DURGE RAJ GHALANghalan_raj@hotmail.com

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Contents

Disorders of Water & sodium metabolism

Disorders of potassium metabolism

Disorders of magnesium metabolism

Disorders of calcium & phosphorus

metabolism

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

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Water balance

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2.1

Water and Sodium Balance

Distribution of body fluid(BF)

BF 60% plasma 5%

Interstitial fluid 15%

ICF 40%

ECF 20%

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Electrolyte in BF

ClNa Na Cl K

HPO4

plasma

Interstitial fluid

ICF

KCa Mg

KCa Mg

HCO3

HPO4

HCO3

HPO4

HCO3

SO4SO4SO4

PrPrOrganic

acid

Organic acid

Na

Ca

Mg

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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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Osmolality↑

Osmolality↓H2OH2O

H2OH2O

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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)

(A) Addition of water to the

body

(B) Addition of hypertonic

salt solution

(C) Addition of isotonic salt

solution

(D) loss of sodium chloride

E I E I

E I E I

Volume

conce

ntra

tion

A B

C D

Changes in volume and osmolality of intracellular(I) and

Extracellular

(E) fluids.

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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

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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

variation of BF vol

variation of OPP

ADH

aldosterone

ANP

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 sodiumosmolality

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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volume

Serum sodium concentrationHyponatrem

ia<130mmol/

L

hypernatremia >150mmol/L

Normal

hypovolemichypovolemic Hyponatremi

a

hypovolemic hypernatremia

Isotonic dehydration

hypervolemic

hypervolemic Hyponatremia

hypervolemic hypernatremia

edema

nomovolemic

nomovolemic Hyponatremia

nomovolemic hypernatremia

normal

Classification of H2O & Na disorders

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hyponatremia

serum sodium ＜ 130 mmol/L ↓ ECF Osmolality ＜ 280 mmol/L ↓ thirsty ↓ ADH ↓ water redistribution ↓ ↓ ↓ intake↓ output↑ cellular swelling

ECF Osmolality ↑volume ↓

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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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　　 sodium loss > water loss

　　 serum sodium ＜ 130 mmol/L

　　 OPP ＜ 280mmol/L

Definition

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Causes & mechanism

renal loss ex- renal lossDiuretics

Adrenal insufficiency

Renal disease

renal tubule acidosis

Renal output of Na

and H2O ↑

GI tract(diarrhea, vomiting

or gastric suction)

Third space (hydrops)

Skin (burn or sweating)

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Effects

OPP

　Thirst ↓ →water intake↓ADH ↓ → renal output↑

ICF →ECF↓

ECF

circulatory failure 　 shockBl vol↓ 　 aldo↑→ UNa↓　　　　　 ADH ↑→oliguriainterstitial fluid↓→sign of dehydration

Caused by renal factors ， UNa↑

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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

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hypernatremia

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

ECF Osmolality ↓ volume ↑

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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↓ Water output↑

Unavailability of water

Thirst ↓

Unable to drink

air tube

Skin

kidney

GI tract

ADH secretion↓

diuretics

high protein diet

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Effects

ECF

　　　　　 aldo↑→ oliguriaBl vol↓ 　　　　　　　　　　　 ADH ↑→oliguria UNa↑Interstitial fluid↓→sign of dehydration

　thirst→water intake↑ ADH ↑ → oliguriaICF ↓ →brain cell dehydration →CNS

disorders

OPP

Twitching, somnolence, respiratory paralysis

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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 - √

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Multiple choice questions of type A

Shock is often caused by which of the following disorder of water and electrolytes

A. hypotonic dehydration     

  B. hypertonic dehydration

C. isotonic dehydration

D. water intoxication

E. hypokalemia

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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 ↑

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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 726mOsm/L.

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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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