Sodium metabolism and its clinical applications

Electrolytes
• Electrolytes : compounds which readily dissociate in solution and
exist as ions i.e. positively (cation )and negatively charged particles
(anions)
• NaCl molecule exists as cation (Na+) and anion ( Cl - ).
• Concentration of electrolytes is expressed as milliequivalents per liter.
( mequ/L )
• 1gm equivalent weight of electrolyte is its weight expressed in grams
that can combine or displace 1g of hydrogen.
• 1gm equivalent weight= 1000 milliequivalents (mequ/L )
• mequ/l = mg per L x valency
Atomic weight

Metabolism of electrolytes
Key aspects of Metabolism of electrolytes involve
1. Distribution of electrolytes in body fluids
2. Dietary intake of electrolytes
3. Biochemical functions of electrolytes ( refer mineral metabolism )

• Electrolytes are distributed in the human body fluids to maintain the
osmotic equilibrium and water balance .
• The total concentration of cations and anions in each body
compartment (ECF and ICF )is equal to maintain electrical neutrality .
• There is marked difference in concentration of electrolytes ( cations and
anions ) between extracellular (ECF) and intracellular fluids (ICF).
• This difference in concentration of electrolytes is needed for cell
survival and maintained by Sodium Potassium pumps(Na+
-K+pump).

• Chief extracellular cation = Na+
• Chief intracellular cation = K+
• Principal extracellular anion = Cl⁻
• Principal intracellular anion = HPO₄⁻
• Cl⁻ and HCO⁻3 occur predominantly in extracellular fluids.
• HPO₄⁻,proteins ,organic acids are found predominantly
intracellular fluids.

Na⁺=142
K⁺= 5
Ca²⁺=5
Mg²⁺= 3
Total
=155
Cations
Cl⁻=103
HCO₃⁻ = 27
HPO₄2⁻ = 2
so₄2⁻=1
Proteins
=16
Organic
acids = 6
Total = 155
Anions
concentration of ions (milliequivalents /L )
Principle
Extracellular
Anion
Principle
extracellular cation

Na⁺=10
K⁺= 150
Ca²⁺=2
Mg²⁺=
40
Total
=202
Cations
Cl⁻=2
HCO₃⁻ = 10
HPO₄2⁻
=140
so₄2⁻=5
Proteins
=40
Organic
acids = 5
Total = 202
Anions
concentration of ions (milliequivalents /L )
Chief
intracellular cation
Chief
intracellular
anion

Osmosis
• Osmosis( Greek : push) refers to the movement of solvent (most
frequently water) through a semipermeable membrane.
• Flow of solvent occurs from solution of low concentration to a high
concentration , when both are separated by semipermeable
membrane.(permeable to the solvent and not to the solute)
• Osmosis is a colligative property –a character depends on the number
of solute particles and not on their nature.
• Osmotic pressure may be defined as the excess of pressure that must
be applied to a solution to prevent the passage of solvent into the
solution ,when both are separated by semipermeable membrane.
• Osmotic pressure is directly proportional to the concentration
(number) of solute molecules or ions .

Osmotic pressure
Osmotic pressure is directly proportional to the concentration (number) of solute molecules or ions .
Flow of solvent occurs from solution of low concentration to a high concentration , when both are
separated by semipermeable membrane.(permeable to the solvent and not to the solute)

Osmotic pressure
• Low molecular weight substances (e.g. glucose ,NaCl )will have
more number of molecules compared to high molecular weight
substances (e.g. Albumin, globulin)for unit mass.
• Substances with low molecular weight, in general exhibit greater
osmotic pressure.
• For ionizable compounds ,the total osmotic pressure is equivalent to
the sum of individual pressures exerted by each ion.
• One molar solution of NaCl will exert double osmotic pressure of one
molar of glucose solution .This is because NaCl ionizes to Na+ and Cl-
while glucose is non-ionizable .
• Oncotic pressure : is commonly used to represent the osmotic
pressure of colloidal substances. (e.g. Albumin, globulin)

Comparison of Osmotic and Oncotic pressure

Osmotic pressure
• Solutions that exert the same osmotic pressure are said to be
isosmotic .The term isotonic is used when a cell is in direct contact
with an isosmotic Solutions ( 0.9% NaCl ) which doesn't change
the cell volume and the cell tone is maintained .
• Solutions with relatively greater osmotic pressure are said to be
hypertonic.
• Solutions with relatively lower osmotic pressure are said to be
hypotonic.

Units of osmotic pressure
• Osmole is the unit of osmotic pressure.
• One Osmole= the number of molecules of gram molecular weight of
undissociated solute.
• One gram molecular weight of glucose (180 g) is One Osmole.
• One gram molecular weight of NaCl (58.5 g ) is equivalent to two
Osmoles since NaCl ionizes to give two particles ( Na+ and Cl- ).
• Osmotic pressure of biological fluids is frequently expressed as
milliosmoles .
• Osmotic pressure of plasma = 285-295 milliosmoles/L

Osmolarity and Osmolality of biological fluids
Expression of concentration of molecules with regards to the
osmotic pressure :
1. Osmolarity : number of moles (or millimoles) / per L of solution
2. Osmolality : number of moles (or millimoles )per kg of solvent
➢Solvent if water Osmolarity = Osmolality
➢Solvent if not water but biological fluid containing proteins & organic
acids : 6% Osmolality ˃ Osmolarity

Osmolality of plasma
1. Osmolality : is a measure of the solute particles present in the fluid medium.
( measured by osmometer or indirectly as the concentration of effective
osmoles)
2. Osmolality of plasma= 285-295miliosmoles /kg
3. Osmolality of plasma ( concentration mmols/L )=2  (Na⁺) +2(K⁺)+ Urea+
Glucose –for clinical purpose
4. Factor 2 is used for (Na⁺) and (K⁺)ions to account for the associated anion
concentration ( assuming complete ionization of the molecules )
5. Osmolality of plasma ( concentration mmols/L )= 2  x plasma (Na⁺) as Sodium
is a chief contributor to osmolality*- 90% osmolality of ECF.
6. * This simplified calculation holds good only if plasma concentration of
Glucose and Urea are in normal range .It is not valid in lipemia and severe
hyperproteinemia.

Distribution of constituents in plasma Osmolality
Constituent ( solute ) plasma Osmolality (milliosmoles-mOsm /kg )
Sodium 135
Associated anions 135
Potassium 3.5
Associated anions 3.5
Calcium 1.5
Magnesium 1.0
Urea 5.0
Glucose 5.0
Protein 1.0
Total 293

Osmolar Gap
• Osmolar Gap = difference between measured osmolality and
calculated osmolality
• Osmolar Gap increases when ethanol, mannitol, neutral and cationic
amino acids etc. are present in plasma .

Anion Gap in Metabolic Acidosis

Chloride ions and anion gap
• Sum of bicarbonate ion + chloride ion +10 = sodium ion concentration
• If Sum of bicarbonate ion + chloride ion is far less than sodium ion
concentration ,it may be inferred that possibly there has been addition of
substantial amounts of another anion (anion gap)
• anion gap is seen in lactic acidosis or diabetes ketoacidosis where lactate
or ketone bodies ( acetoacetate and – hydroxy butyrate ) anions fill the
anion gap respectively.

Osmolality of ECF and ICF
1. Movement of water across the biological membranes dependent on the
osmotic pressure differences between of the intracellular(ICF) and
extracellular fluid (ECF).
2. osmotic pressure of the extracellular fluid (ECF)predominantly due to
(Na⁺) :in healthy state
3. osmotic pressure of the intracellular fluid(ICF) predominantly due to (K⁺)
4. osmotic equilibrium:
osmotic pressure of the intracellular fluid (ICF) = osmotic pressure of extracellular
fluid (ECF) : observed in healthy state
❖There is no net passage of water molecules in or out of the cells due to this
osmotic equilibrium.

Summary of ECF and ICF
• At equilibrium ,the osmolality extracellular fluid (ECF) and
intracellular fluid (ICF) are identical
• Solute content of ICF is constant.
• Sodium is retained only in ECF.
• The body fluid osmolality= Total body Solute
Total body water
• Intracellular volume = Total intracellular Solute
plasma osmolality

Colloidal osmotic pressure of plasma
➢Colloidal osmotic pressure is exerted by proteins.
➢It maintains intracellular and intravascular fluid compartments .
• If gradient is reduced, the fluid will extravasate and accumulate in the
interstitial space leading to edema .
• Albumin is mainly responsible for maintain Colloidal osmotic pressure
and osmotic balance.

Colloidal osmotic pressure of plasma and Edema

Factors which influence the distribution of water
Osmotic pressure depends on
1. Electrolytes :
Na⁺ -chief cation of extracellular fluid , K ⁺ chief cation of intracellular fluid
2. organic substances of small molecular weight ( Glucose ,Urea , amino acids )
Properties :a. Free diffusion (small size ) b. influence total body fluid if present
in large in large quantities
3. organic substances of large molecular weight(Serum protein- Albumin)
At p H 7.4 : a. behaves as acids ( donate H ⁺ ) b. negatively charged c. combine
with cation ( Sodium )

Clinical applications of osmolality of fluid
Clinical applications of osmolality of fluid include :
1. Fluid balance and blood volume
2. Red blood cells and fragility
3. Transfusion
4. Action of laxatives/ purgatives
5. Osmotic diuresis
6. Edema due to hypoalbuminemia
7. Cerebral edema
8. irrigation of wounds

Fluid balance and blood volume : 1. Clinical applications of osmolality of fluid:
1.Fluid balance and blood volume :The fluid balance of different
compartments of body is maintained due to osmosis. Osmosis significantly
contributes to the regulation of blood volume and urine excretion.
• Isotonic fluids have same concentration of solutes as cells ,thus no fluid is
drawn out or moves into the cell.
• Hypertonic fluids have a higher concentration of solutes (Hyperosmolality)
than found inside the cells ,which causes fluid to flow out of the cell and
into extracellular spaces . This causes cells to shrink.
• Hypotonic fluids have a lower concentration of solutes(Hypoosmolality)
than found inside the cells ,which causes fluid to flow into cells and out
of extracellular spaces . This causes cells to swell and possibly burst .

Red blood cells (RBC)and fragility : 2.Clinical applications of osmolality of fluid:
2.Red blood cells (RBC) and fragility : when RBC are suspended in an
isotonic solution (0.9 % NaCl) ,the cell volume remains unchanged and RBC
are intact.
In Hypertonic solutions (e.g.1.8 % NaCl) water flows out of RBC and
cytoplasm shrinks. This phenomenon referred to as crenation.
In Hypotonic solutions (e.g. 0.3 % NaCl) water flows into RBC and cells
bulge due to entry of water which often causes rupture of plasma
membrane of RBC (hemolysis) .

2.Red blood cells (RBC) and fragility

Infusions (IV Fluids) :3a. Clinical applications of osmolality of fluid:
3a. Infusions (IV Fluids ) : isotonic solution of NaCl (0.9 % NaCl=saline )or (5
% glucose) or combination of these two are used in management of
dehydration and burns etc.

3.Management of dehydration and burns

3b. Blood Transfusion: osmolality of Blood is to be maintained .

Action of purgatives/laxatives : 4. Clinical applications of osmolality of fluid :
4.Action of purgatives/laxatives : The mechanism of action of laxatives
/purgatives is mainly due to osmotic phenomenon. For instance ,Epson
(MgSO4 7H2O),Glauber’s (Na2SO4 10H2O) salts withdraw water from
the body, besides preventing the intestinal water absorption.

4a/b. Mechanism Action of purgatives/laxatives

Osmotic diuresis : 5 . Clinical applications of osmolality of fluid :
5. Osmotic diuresis: The high blood glucose concentration causes
osmotic diuresis resulting in the loss of water, electrolyte and glucose
in the urine. This is the basis of polyuria observed in Diabetes mellitus .
• Diuresis can be produced by administrating compounds (e.g.
Mannitol ) which are filtered but not absorbed by renal tubules.

Edemaduetohypoalbuminemia:6.Clinicalapplicationsofosmolalityoffluid:.
6. Edema due to hypoalbuminemia : Disorders such as kwashiorkor and
glomerular nephritis are associated with lowered plasma albumin
concentration and edema . Edema is caused by reduced osmotic
pressure of plasma leading to accumulation of excess fluid in tissue
spaces.

6.Edema due to hypoalbuminemia

Cerebral edema : 7.Clinical applications of osmolality of fluid:
• 7.Cerebral edema :Hypertonic solution of salts (NaCl,MgSO4) are in
use to reduce the pressure of cerebrospinal fluid.

7. Management of Cerebral edema

Irrigationofwounds:Clinicalapplicationsofosmolalityoffluid: 8 .
8. Irrigation of wounds : Isotonic solutions are used for washing
wounds. The pain experienced by the direct addition of salt to wounds
is due to osmotic pressure.

Sodium
• Occurrence : Sodium exists as NaCl ,Na₂CO₃, NaHCO₃ in an extracellular
fluid about 40%- (exchangeable form), about 50% in bones and remaining
10% in soft tissue ( non-exchangeable form)
• Total body sodium : 4000 mequ/L (1.8g/kg)
• Sodium pump (ATP dependent mechanism) operating in all cells
keep sodium in extracellular compartment.
• Body can conserve sodium to the extent that on a sodium free diet
urine dose not contain sodium. Normally kidneys are primed to
conserve sodium and excrete potassium.

Daily Dietary requirement of sodium
❖Dietary Sources of sodium : NaCl ( cooking , seasoning ),Cheese,
wheat germ, bread ,carrot , eggs , milk ,nuts , radish, baking
soda/powder, fish, meat
❖Daily Dietary requirement of sodium :
1. for normal individual :1-5 g/day ( normal diet mainly in form of
NaCl)
2. Patients with hypertension : 1 g/day
3. Ideally Dietary: sodium intake < potassium intake ( processed food
have increased sodium content )

Dietary Sources of sodium
processed food have increased sodium contentFruits to be restricted in Diabetes Mellitus

Distribution of Sodium in human body
Fluid / cells mequ/L mg/ dl or 100 gm
Whole blood 70 160
Plasma 143 330
cells 37 85
Nerve tissue -- 60-160
Muscle tissue -- 312

Functions of sodium in human body

Functions of sodium in human body
❖Functions of sodium in human body include :
1. Regulation of acid-base balance in association with chloride and
bicarbonate ions as it is a constituent of buffer
2. Maintenance of osmotic pressure and fluid balance
3. Essential for muscle and neve irritability
4. Involved in cell membrane permeability
5. Involved in glucose ,galactose and amino acid absorption
6. Initiation and maintenance of heart beats

1.Regulation of acid-base balance in association with chloride and bicarbonate ions

2.Maintenance of osmotic pressure and fluid balance

3.Essential for muscle and nerve irritability

4. Involved in glucose ,galactose and amino acid absorption

5.Initiation and maintenance of heart beats

Metabolism of Sodium
• Osmotic effect of sodium : Na+ and Cl- cause retention of water in the ECF
therefore concentration of Na+ has direct effect on osmotic pressure of ECF and
its volume
• Absorption of dietary sodium : readily absorbed in gastrointestinal tract
• Plasma (serum ) concentration of sodium : 135-145 mequ/L .
Sodium is extracellular cation therefore blood cells contain 12 mequ/L(<35 mequ/L
of sodium.
Increase in Plasma /serum sodium concentration: Cushing's syndrome (
hyperactivity of adrenal cortex)
Decrease in Plasma /serum sodium concentration :Addison’s disease
(adrenocortical insufficiency increase in urinary sodium excretion )
❖Measurement of Plasma (serum ) concentration of sodium: using flame
photometer or ion selective electrode (when assayed in serum containing
hyperlipidemia / or hyperglobulinemia  apparent decrease in serum sodium
concentration )

Sodium ions and anion gap
• Sum of bicarbonate ion + chloride ion +10 = sodium ion concentration
• If Sum of bicarbonate ion + chloride ion is far less than sodium ion
concentration ,it may be inferred that possibly there has been addition of
substantial amounts of another anion (anion gap).
• Anion gap is seen in lactic acidosis or diabetes ketoacidosis where lactate
or ketone bodies ( acetoacetate and – hydroxy butyrate ) anions fill the
anion gap respectively.

Excretion of Sodium from human body
• Major route of Excretion of Sodium : urinary excretion by kidney
• In kidney , 800 g of Sodium is filtered in glomerular filtrate (175L /day ) and
99% of this is reabsorbed in proximal convoluted renal tubules by active
process.( controlled by Aldosterone - increases Sodium reabsorption )
• Along with Sodium ,water is facultatively reabsorbed.(Sodium reabsorption
is primary and water reabsorption is secondary) .
• Antidiuretic hormone ( ADH )increases water reabsorption from convoluted
renal tubules
• Excretion of Sodium in urine:10 gm NaCl intake /day = 4 gm of Na ⁺ output
(98% this is excreted in urine - 120 mequ/L ,60-150mmols/day)
• Excretion of Sodium in feces : ( < 2 % ),excretion of sodium in feces
increases in diarrhea
• Excretion of Sodium in sweat : individual variation

Mechanisms involved in regulation of urinary excretion of
Sodium :1
Mechanisms involved in regulation of urinary Excretion of Sodium
include :
• The Renin –angiotensin –aldosterone system (RAAS)
• The glomerular filtration rate (GFR):The rate of Na+
excretion is related to GFR . When GFR falls actually, the less Na+
is excreted or vice-versa.
• Dopamine :An increase in filtered sodium load causes
increased Dopamine synthesis by proximal convoluted renal
tubular cells. Dopamine then acts on the distal tubules to
stimulate sodium excretion.
• Atrial natriuretic peptide

Mechanisms associated with Excretion of Sodium from human body:2
1. Sodium hydrogen exchanger located in proximal convoluted renal
tubules and ascending limb
2. Sodium chloride cotransporter in distal tubules (ascending limb)
3. Sodium channels in the collecting ducts
4. Sodium potassium exchanger located in distal tubules
❖ Rate of excretion of sodium in urine is directly affected by:
a) Renal plasma flow
b) Blood pressure acting through Atrial Natriuretic peptide

Dietary intake and electrolyte balance
• Balanced diet  supplies the requirement of electrolytes
• Human don't possess the ability to distinguish between the salt
hunger and water hunger
• Thirst may regulate electrolyte intake also.
• In hot climates ,the loss of electrolytes is usually higher and mandates
supplementation drinking water with electrolytes .

Water & electrolyte balance are regulated together by
1.Kidneys : play predominant role
2. ADH or Vasopressin
3. Renin –Angiotensin –Aldosterone system (RAAS ) Hormones
4. Atrial Natriuretic factor ( ANF )
5. Sodium concentration in ECF
Regulation of Water & electrolyte balance is mostly achieved by
hormones .

Hormonal regulation of excretion of Urine

1. Hypothalamic mechanism controlling thirst
Water & Sodium output exceed intake
Negative Water & Sodium Balance
ECF volume contracts
decrease in plasma volume
decrease in cardiac output
Cardiovascular changes produce EFFECTS 

Stimulation of H₂O intake area of Hypothalamus - Thirst Centre
Stimulation of H₂O output area of Hypothalamus & ADH secretion
Stimulation of Renin Angiotensin Aldosterone System
Inhibition of release of Arterial Natriuretic Factor ( ANF )
Retention of Sodium & Water by the Kidney (till homeostasis)
EFFECTS 

Thirst center located in the third ventricle in hypothalamus

Hormonal regulation of electrolyte balance
Hormonal regulation of electrolyte balance by
1. Aldosterone ( a mineralocorticoid secreted by Adrenal cortex )
2. ADH( Antidiuretic hormone )secreted by posterior pituitary
3. Renin Angiotensin ( Angiotensinogen secreted by liver and its
activation to Angiotensin I by Renin ,followed by conversion of
Angiotensin I to Angiotensin II in kidney )

Site of action of Aldosterone and ADH

Hormonal regulation of electrolyte balance –by Aldosterone
 plasma osmolality ( mostly due to decrease in plasma sodium levels)
↑secretion of Aldosterone by Adrenal cortex
↑ Na ⁺ reabsorption by renal tubular cells ( at expense of K ⁺ & H⁺ )
↑ retention of Na ⁺ in body
Till Homeostasis is achieved

Regulation of electrolyte balance by Renin Angiotensin system
↑ Na ⁺ reabsorption by renal tubular cells ( at expense of K ⁺ & H⁺ )
↑ retention of Na ⁺ in body
The secretion of Aldosterone is controlled by Renin Angiotensin system

Hormonal regulation of electrolyte balance –by Antidiuretic hormone
↑ plasma osmolality ( mostly due to sodium)
↑ stimulus to Hypothalamus(sensation of thirst)
↑Antidiuretic hormone ( ADH ) secretion by posterior pituitary
↑reabsorption of H₂O by renal tubular cells(production of small volume urine)
Till Homeostasis is achieved

Hormonal regulation of electrolyte balance by Antidiuretic
hormone

Hormonal regulation of electrolyte balance by Antidiuretic hormone:1
↑ ECF ↑ plasma osmolality ( due to ↑sodium )
↑ stimulus to Hypothalamus
↑ Antidiuretic hormone (ADH) secretion posterior pituitary
↑reabsorption of water by renal tubular cells
Decreased urine out put till Homeostasis is achieved
Osmolality based on Na⁺ concentration

↓ECF ↓ plasma osmolality ( due to ↓ sodium )
↓ stimulus to Hypothalamus (suppression of thirst center)
↓ Antidiuretic hormone (ADH) secretion
↓ reabsorption of H₂O by renal tubular cells
More urine out put till Homeostasis is achieved
Diabetes Insipidus : Deficiency of ADH  loss of water from the body in excess

Comparison of Renin and Rennin
Renin
ENZYME
Secreted by
kidney
Involved in
activation of
Angiotensinogen
during fluid
balance
Rennin
Seen in
gastric juice
Proteolytic
enzyme in
children
Angiotensinogen -(alpha 2 globulin synthesized in liver )

Renin Angiotensin system
❖Factors which activate renin release are :
a) Decreased blood pressure
b) Salt depletion
c) prostaglandins

❖Factors which inhibit renin release are:
a) increased blood pressure
b) increased Salt intake
c) Prostaglandin inhibitors
d) Angiotensin II

Na + concentration
ECF VOLUME
Renal plasma flow
Release of Renin by the juxtaglomerular cells

Role of Renin Angiotensin system in regulation of electrolyte balance
Secretion of Aldosterone controlled by Renin Angiotensin system
↓Na + conc.
↓ECF volume
& blood
pressure
↑sensitivity of
juxta
glomerular
apparatus
↑ renin
secretion
Angiotensin I
Angiotensin II
Release of
Aldosterone
↑ reabsorption
of Na ⁺
Aldosterone /ADH
coordinate for water
& electrolyte balance
Homeostasis
Adrenal cortex
ConversionAngiotensinogen

Pathway of active Angiotensin production
Renin
Angiotensinogen  Angiotensin I
(453 amino acids ) ( 10 amino acids)
Angiotensin-converting enzyme (ACE )
Angiotensin I  Angiotensin II
( 10 amino acids) ( 8 amino acids)
Amino peptidase
Angiotensin II  Angiotensin III
( 8 amino acids) ( 7 amino acids)
Angiotensinase
Angiotensin II and Angiotensin III degradation products
Angiotensinogen and Angiotensin I : inactive
Angiotensin II and Angiotensin III : active

Angiotensin II
❖Angiotensin II
a) Increases blood pressure by causing vasoconstriction of the
arterioles.
b) Stimulates Aldosterone production by enhancing conversion of
corticosterone to Aldosterone.
c) It inhibits renin release from juxtaglomerular cells.
d) Thus maintains Sodium and water balance as well as ECF volume.

Angiotensin-converting enzyme (ACE)
➢Angiotensin-converting enzyme (ACE ) is a glycoprotein present in
lungs.
➢Angiotensin-converting enzyme (ACE ) converts Angiotensin I to
Angiotensin II which intern stimulate Aldosterone secretion by
adrenal cortex.
➢Angiotensin-converting enzyme (ACE ) inhibitors are useful in
treating edema and chronic congestive cardiac failure.
➢Peptide analogs of Angiotensin II ( Saralasin ) and antagonist of
Angiotensin-converting enzyme (ACE antagonist- Captopril ) are
useful in treatment of renin and angiotensin dependent hypertension.

Pathway of active Angiotensin production and their receptors

Angiotensinogen
Angiotensin I
Angiotensin II
Release of
ALDOSTERONE from
Adrenal Cortex
Na⁺ absorption
K ⁺ Excretion
Kidney RENIN
Decrease in serum Na ⁺
Kidney
Increase in serum Na ⁺
Renin Angiotensin Aldosterone system (RAAS )

Renin Angiotensin Aldosterone system (RAAS )

Role of Renin-Angiotensinogen in regulation of Water &electrolyte balance
Increase Renin secretion
Decrease in sodium supply
Angiotensin IAngiotensinogen
Angiotensin II
increase Aldosterone secretion
Thirsting behavior
ADH secretion
Increase in sodium reabsorption by renal
tubules
Increase in H+ ↔ Na+ exchangeWater retention
Expansion of ECW
Loss of water & sodium restoration ( ECW balance to normal)
(Homeostasis)
Homeostasis

Atrial Natriuretic factor ( ANF )
1. ANF is a Polypeptide containing 28 amino acids
2.ANF secretion by right atrium of Heart in response to increased blood volume ,elevated blood
pressure and high salt intake( stimulation of atrial stretch receptors )
3.Kidney plays role in sodium & water balance in association with ANF
( ANF increases GFR , Sodium excretion , urine output and ANF lowers renin activity )
4.ANF inhibits the secretions of renin , Aldosterone and epinephrine ( renin and Aldosterone
increase salt retention and hence increase blood pressure)
5.Increase in plasma sodium & water  increase in ANF
secretion increases sodium& water excretion(natriuresis)
6. Net effect of ANF sodium & water elimination ECW restore to normal
7. sodium & water balance  (Homeostasis)

ANF secretion by right atrium of Heart

Atrial Natriuretic factor ( ANF )

Mechanism of action of Atrial Natriuretic factor ( ANF )

Atrial Natriuretic factor ( ANF )in sodium Homeostasis
ANF increases sodium and water excretion by kidneys
In negative sodium and water contraction of ECW ANF inhibited
decrease in sodium and water excretion by kidneys sodium and
water retention by kidneys ECW restore to normal (Homeostasis)
In positive sodium and water expansion of ECWANF secretion
stimulated increase sodium & water excretion by kidneys ECW
restore to normal (Homeostasis)

Role of Atrial Natriuretic factor( ANF) in regulation of Water &electrolyte balance
High salt intake
Increased in blood volume
Elevation in blood pressure
ANF acts on kidney to increase GFR
Increase in Sodium excretion in urine
Increase in urine output till Homeostasis

Mineralocorticoids in Sodium Metabolism
Mineralocorticoids*(except Androgen ) in Sodium Metabolism
❖Mineralocorticoids*(except Androgen ):
a) Increase absorption of Sodium from diet / renal filtrate
b) Decrease excretion of Sodium through kidney (also skin through
sweat gland & gastro intestinal tract )

Hormonal regulation of Sodium balance by kidney- site of action

Hormonal regulation of Sodium balance by kidney
Angiotensin II
Adrenal
gland
AldosteroneAngiotensinogen
Angiotensin I
Renin
Na+ reabsorption by renal
tubules
Angiotensinogen is secreted by Liver

Regulation of Water &electrolyte balance –by Sodium in ECF
Na ⁺ & Cl ⁻ confined to ECF
↑Concentration of Na ⁺ & Cl ⁻ confined to ECF
↑osmolality of ECF
↑ Retention of water

Regulation of Water &electrolyte balance –by Sodium in ECF

Clinical significance of sodium metabolism
➢Sodium presents a threat to health more commonly from
overconsumption(leading to hypernatremia) than from its deficiency
(leading to hyponatremia).
➢Sodium increases water/fluid retention and activation of renin –
angiotensin system may cause high blood pressure .

Sodium depletion: Hyponatremia (low Serum sodium levels)

Sodium depletion
Sodium depletion occurs when there is loss of both sodium and water followed
by replacement of water without sodium.

Clinical Symptoms of sodium depletion
Tiredness ,apathy
Weight loss
Nausea
Vomiting
Hypotension
Muscle weakness
Intestinal dilation
Oliguria
Vasoconstrictive shock, tachycardia
Coma, Death ( circulatory failure /insufficiency)

Signs and symptoms of Hyponatremia

Causes of sodium depletion
Diminished intake ( Malnutrition, anorexia nervosa, chronic alcoholism)
Dehydration ( loss of water ) replaced only by water
Loss through skin-Burns ,cystic fibrosis, massive sweating exudative skin lesions )
Loss through gut -vomiting , prolonged Diarrhea ,steatorrhea , intestinal obstruction ,fistulae
Addison ’s disease ( adrenocortical insufficiency )
Salt losing chronic nephritis /chronic renal failure/over use of diuretics
Hyperglycemia /Diabetes ketoacidosis /excess glucose IV infusion
Sickcellsyndome(partofacuteorchronicillnessduetofailureofsodiumpump)

Drugs which cause hyponatremia
❖Drugs which cause hyponatremia include :
• ACE inhibitors
• Lithium
• Vasopressin
• Oxytocin
• Chlorpropamide
• NSAIDs

NSAIDs: Drugs which cause hyponatremia

Classification of hyponatremia
Dilutional hyponatremia due
to
• Increased water intake
• Inappropriate administration
of fluid with low sodium
content
• Addison ’s disease
• Syndrome Inappropriate ADH
secretion (SIADH)
• Nephrotic syndrome
• Congestive cardiac failure
• =Hypotonic hyponatremia
it always reflects the inability
of kidneys to handle
excretion of water to match
oral intake
Appropriate
Hyponatremia associated with
high plasma osmolality due to
• Increased plasma
concentration of urea ,
glucose ,alcohol and other
solutes
• Infusion of mannitol and
amino acids
• =Hypertonic hyponatremia
Normal body sodium and
additional drop in measured
serum sodium levels with
high osmality (presence of
osmotically active molecules-
glucose /mannitol ) *
Pseudo
hyponatremia
• associated with
paraproteinemia (myeloma)
and hyperlipidemia
• Mannitol
• =Normotonic hyponatremia
low measured serum sodium
levels with normal osmality (as
plasma water fraction falls )
• Serum sodium concentration
to be measured using flame
photometry not with ion
selective electrode

*Hypertonic hyponatremia
• Hypertonic hyponatremia: Normal body sodium and additional drop
in measured sodium due to presence osmotically active molecules in
serum which cause shift of water from intracellular to extracellular
compartment(e.g. hyperglycemia)
• The high levels of serum glucose increases osmolality leading to
Hypertonic hyponatremia. Similar effects are seen during mannitol
infusion also.
status of Hyperglycemia Drop in serum sodium levels for every
increment of 100 mg of glucose
Above100 mg of glucose 1.6 mmols/L
Above400 mg of glucose 2.4 mmols/L

Cotransport of Glucose and Sodium

Pseudo hyponatremia (PHN)
• Pseudo hyponatremia = Pseudo/ false hyponatremia is that it dose
not reflect a deficiency in total body sodium stores ( such as occurs in
renal sodium loss )
• Pseudo hyponatremia :The term is used in situation where blood
hyperosmolarity ,is due to severe hyperglycemia results in movement
of water from the intracellular fluid (ICF) to extracellular fluid (ECF)
diluting all the solutes of extracellular fluid (ECF) to restore
osmotic balance. When that happens, plasma sodium concentration
decreases along with the concentration of an other plasma
constituents that do not freely equilibrate across the cell membrane.
• This is sometimes called as hypertonic hyponatremia.

Clinical Symptoms of sodium depletion
Sodium depletion: Hyponatremia ( low Serum sodium levels)
❖Clinical Symptoms that appear after sodium equivalent of four liters of
isotonic saline lost include :
1. Tiredness ,apathy
2. Weight loss
3. Nausea
4. Vomiting
5. Hypotension (drop of blood pressure)
6. Muscle weakness
7. Intestinal dilation
8. Oliguria
9. Vasoconstrictive shock , tachycardia
10. Coma, Death (reduced blood pressure, circulatory failure /insufficiency)

Biochemical findings in sodium depletion
❖ Biochemical findings in sodium depletion include :
• Decrease in plasma sodium
• Decrease in ECF volume
• Decrease in ECF osmolality
• Decrease in urine volume
• urine sodium: Increase in in Addison’s disease & Decrease in urine
sodium in other conditions
• Increase in plasma proteins

Biochemical findings in sodium depletion
Decrease in plasma sodium
Decrease in ECF volume
Decrease in ECF osmolality
Decrease in urine volume
urine sodium: Increases in Addison’s disease & Decrease in urine sodium in other conditions
Increase in plasma proteins

Syndrome of inappropriate ADH secretion –SIADH

SIADH (Syndrome of inappropriate ADH secretion)
• SIADH (Syndrome of inappropriate ADH secretion)is a condition
with Hyponatremia, normal filtration rate, normal serum urea and
creatinine concentration .
• urine flow rate in SIADH : < 1.5L/day
• Symptoms of SIADH are proportional to the rate of fall of sodium
and not to absolute value.

Causes of SIADH (Syndrome of inappropriate ADH secretion)
• Infections (pneumonia ,sub phrenic abscess, TB, aspergillosis)
• Malignancy (cancer of colon ,pancreas, prostate ,small cell lung
cancer of the lungs )
• Trauma ( abdominal surgery , head Trauma)
• CNS disorders (Meningitis ,encephalitis ,brain abscess, cerebral
hemorrhage )
• Drug induced (Thiazide diuretics , chlorpropamide, carbamazepine
,opiates )

Causes of SIADH (Syndrome of inappropriate ADH secretion)

Biochemical findings for Diagnosis of SIADH
• Hyponatremia : serum sodium( <135 mmols/L or mequ/L)
• Decreased plasma osmality :( <275 mOsm/kg )
• Urine sodium : > 20 mmols/L or mequ/L
• Urine osmality :( >100 mOsm/kg )

Biochemical tests for Diagnosis of SIADH

Comparison of sodium depletion and SIAD

Homeostatic mechanisms in sodium depletion
Homeostatic mechanisms in sodium depletion involve the following
sequence of events :
• Inhibition of ADH secretion
• Loss of water in urine
• Decrease in ECF volume
• Stimulation of aldosterone secretion
• Reabsorption of sodium
• Restoration of plasma osmolality

Hormonal regulation of Sodium balance –by Aldosterone

Inhibition of ADH secretion
Loss of water in urine
Decrease in ECF volume
Stimulation of aldosterone secretion
Reabsorption of sodium till homeostasis is acheived

Management of sodium depletion
Management of Sodium depletion- Hyponatremia (low Serum sodium levels)
:depends upon cause ,duration and severity.
❖ Water restriction, increased salt intake ,furosemide ,and anti -ADH are basis
of management of Hyponatremia (Sodium depletion).
❖Intravenous infusion of saline should be closely monitored (after allowing
sufficient time for distribution of Sodium, minimum 4-6 hrs.)
❖Hyponatremic patients without edema have water overload and can be
treated by water restriction.
❖Hyponatremic patients with edema have water and Sodium overload and will
have to be treated by diuretics and fluid restriction.
❖In acute Hyponatremia rapid correction is possible.
❖ In chronic Hyponatremia rapid correction may increase mortality by
neurological complications.

Hypernatremia (high Serum sodium levels )

Causes of Hypernatremia (high Serum sodium levels )
Excess intake of sodium ( dietary / intravenously –excess administration of hypertonic sodium
bicarbonate after cardiac arrest )
Decreased water intake/loss of water from causing dehydration/Head injury with water depletion
Increased water excretion as in Diabetes Mellitus/Diabetes insipidus
Deceased excretion sodium as in renal failure due to low GFR
Cushing’s syndrome (excess mineralocorticoid hormone-hyper activity of adrenal cortex ) & Cohn’s
syndrome (increased sodium renal tubular reabsorption )
Pregnancy /Prolonged administration of cortisone, ACTH, of sex hormones
Drugs such as metronidazole
Accumulation of sodium ,not accompanied by equivalent amount of water occurs due to

Hypernatremia and Diabetes insipidus

Clinical symptoms in sodium excess
• Clinical symptoms in sodium excess ( Hypernatremia- high Serum
sodium levels ) include :
• Hypervolemia observed in sodium excess can cause hypertension
,weight gain and edema.
• ECF hyper osmolality causes thirst, mental confusion(restlessness)
• Coma and death due to cerebral dehydration

Sign and symptoms in sodium excess

Clinical symptoms of Cushing’s syndrome

Drugs which cause hypernatremia
❖Drugs which cause hypernatremia include :
• Ampicillin
• Tetracycline
• Anabolic steroids
• Oral contraceptives
• Loop diuretics
• Osmotic diuretics

Biochemical findings in sodium excess
❖Biochemical findings in sodium excess include:
• Increase in plasma sodium
• Increase in ECF volume
• Increase in ECF osmolality
• Decrease in plasma proteins
• Decrease in urine volume
• urine sodium: Decrease in Cohn’s syndrome & increase in urine

Consequences of Hypernatremia (high Serum sodium levels)
Increase in CNS pressure
Increase in pulmonary odema
eventual respiratory failure  DEATH
Influx of sodium within cell, efflux of Potassium out of a cell, excretion of Potassium in Urine

Homeostatic mechanisms in sodium excess
Increase in ECF osmolality (observed in sodium excess- hypernatremia )
has following consequences:
• Diffusion of water from ICF to ECF
• Inhibition of Aldosterone secretion
• Increase in urinary excretion of sodium
• stimulation of ADH secretion with reabsorption of water till
homeostasis is achieved

Increase in ECF osmolality (observed in sodium excess) has
following consequences
Diffusion of water from ICF to ECF
Increase in ECF volume
Inhibition of Aldosterone secretion
Increase in urinary excretion of sodium till homeostasis is
achieved

Management in sodium excess-- Hypernatremia
1. Management of sodium excess depends upon underlying cause,
duration and severity.
2. Restriction of sodium intake
3. Diuretic therapy for promoting sodium excretion
4. Dialysis if kidney function is impaired
❖In acute Hypernatremia rapid correction is possible.
❖ In chronic Hypernatremia rapid correction may cause herniation and
permanent neurological deficit.
❖The correction of Hypernatremia and hypertonicity is to be done
carefully to prevent sudden overhydration and water intoxication.

Management in sodium excess-- Hypernatremia

Disorders of water &Electrolyte balance
❖Water & Electrolyte imbalance lead to
➢Dehydration
➢Over hydration
Causes of Water & Electrolyte imbalance:
1. Imbalance of Water intake & output
2. Imbalance of Sodium intake & output

• Dehydration is the disturbance of water balance in which the output
exceeds the intake causing a reduction of body water below the normal
level or excessive water loss or both. ( water depletion in the body/negative
water balance )
• Dehydration may be as a result of
1.Pure water depletion=simple dehydration=Primary
Dehydration ( without corresponding loss of electrolytes )
2. Mixed type in which both Water and salt
depletion occur

Causes of dehydration
Dehydration may occur as a result of
1. Diarrhea
2. Vomiting
3. Excessive sweating
4. Fluid loss in burns
5. Adreno-corticoid dysfunction
6. Kidney diseases ( e.g. renal insufficiency )
7. Deficiency of ADH ( Diabetes Insipidus )

Pure water depletion( without corresponding loss of electrolytes )
A –Decreased water intake of as in
• Elderly debilitated persons
• Unconscious patients/coma
• Severe dysphagia
• Postoperative patients ,when oral
intake has been stopped
• Obstructive lesions in esophagus
• starvation
B- increased water loss due to
• Sweating ,during fever
• Hyperventilation
• Infantile gastroenteritis
• Diabetes insipidus due to ADH
deficiency(failure to conserve water)
• Diabetes Mellitus due to osmotic
diuresis
• Nephritis
• Acute renal failure
1.Pure water depletion ( without corresponding loss of electrolytes )occurs
under following conditions

Primary Dehydration
• 1. Primary dehydration : Definition : Pure water depletion( without
corresponding loss of electrolytes )
• Hypernatremia ( increase serum sodium )
1.Causes of coma & dysphagia*
2. When a patients is too weak or too ill to satisfy water needs*
3.Mental (psychiatric )patients*
4. Diabetes Insipidus ∆
5 . Tracheostomy ∆
6. heat stroke ∆
*Deficient water intake , ∆ excessive loss of water failure of regulatory mechanism ( conservation of water) by
kidney

Biochemical findings in simple dehydration
1. Volume of the ECF ( e.g. plasma )decreases with concomitant rise in
electrolyte concentration (increased ECF osmolality) and osmotic
pressure
2. Water is drawn from intracellular fluid  shrunken cells and disturbed
metabolism( e.g. increased protein breakdown)
3. Increased ADH secretion increased water retention decreased
urinary output (decreased urine volume)
4. Decreased urine sodium
5. Increased concentration of plasma sodium(hypernatremia) ,serum
protein ( Normal or slight increased ) and blood urea (mild)
6. Water depletion often accompanied by loss of electrolytes from body
(Na⁺ ,K⁺ etc.)

Pathophysiology of Primary dehydration
❖A. Pathophysiology of Primary dehydration :
Biological findings ( clinical symptoms )
a) Thirst
b) Oliguria ( decrease urine output )
c) Urinary chlorides increased
d) Increased Blood Urea & Negative nitrogen balance
e) Mental confusion
f) Death

Dehydration of muscles and nerve
cells leads to weakness and confusion .
- Oliguria
( and tongue )thirst
Hemoconcentration

Consequences of simple dehydration
❖Consequences of simple dehydration include :
• increased in plasma sodium and osmality
• Deceased renal flow which stimulates Aldosterone secretion with
increased reabsorption of sodium that aggravates hypernatremia
• Increased in ECF osmolality ,resulting in diffusion of water from the
cells –ICF to the ECF

Dehydration( vicious cycle)
Sodium
depletion
Anorexia
Vomiting
Loss of NaCl
in vomitus
Salt
depletion

Causes of Secondary dehydration
❖B Secondary dehydration : Pure salt depletion combined deficiency of water
&electrolytes (more common than simple dehydration )
Causes of Secondary dehydration :
a) Excessive sweating
b) Loss of GI fluids in small intestinal obstruction or intestinal fistula
c) Urinary losses of sodium in failure of renal tubular dysfunction
d) Vigorous use of Diuretics (removal of ECF as in edema ,ascites and paralytic
ileus)

Clinical symptoms of secondary dehydration
❖B Secondary dehydration : Pure salt depletion combined deficiency of water
&electrolytes
Clinical Symptoms of Secondary dehydration :
a) Absence of Thirst
b) Anorexia & nausea
c) Cramps/apathy/weakness
d) Sunken eyes & inelastic skin
e) Reduced plasma volume
f) Decreased GFR oliguria

Clinical symptoms of dehydration due to mixed water & salt ( sodium) depletion
❖C . Symptoms of Dehydration due to Mixed water & salt ( Sodium )
depletion include :
1. Wrinkled skin
2.Dry mucous membrane
3. Muscle cramps
4. Sunken eyeballs
5. Oliguria
6. Increased Blood Urea Nitrogen BUN
7. Increased hematocrit
8. increased weakness
9. Hypotension
10. shock
11. Death

Types of Dehydration :due to Mixed water & salt ( Sodium ) depletion
❖C Types of Dehydration due to Mixed water & salt ( Sodium ) depletion
Hypernatremic
or
Hyperosmolar
dehydration
Normonatremic
or
Iso-osmolar
dehydration
Hyponatremic
or
Hypo-osmolar
dehydration

Causes of dehydration due to mixed water & salt ( sodium ) depletion-
Hypernatremic
dehydration
• a. Excessive sweating &
inadequate intake of water
• b. Water & food
deprivation
• c. osmotic diuresis with
Glycosuria
• d. Diuretic therapy if water
intake is inadequate
Normonatremic
dehydration
• a. Vomiting
• b. Diarrhea
Hyponatremic
dehydration
• a. Salt wasting renal disease
• b. Adrenal cortical
insufficiency, Addison’s
disease
• c. Excessive sweating
• d. Diuretic therapy if water
intake is inadequate

Consequences of dehydration due to mixed water & salt ( sodium) depletion
Hypernatremic or
Hyperosmolar
dehydration
• water balance is more
negative than sodium
balance
• Increase in ECW
osmolarity causes
water to move out of
cell & contraction of
ICW volume occurs
Normonatremic
or
Isosmolar dehydration
• water balance is equal
to sodium balance
• No changes in ECW &
ICW osmolarity
therefore water influx
and water efflux stops
.
Hyponatremic
or
Hyposmolar
dehydration
• water balance is less
negative than sodium
balance
• With decrease in ECW
osmolarity causes
water to move into cell
& expansion of ICW
volume occurs

Consequences of dehydration due to mixed water & salt ( sodium) depletion-
Hypernatremic or
Hyperosmolar
dehydration
• The degree
extracellular volume
contraction is least.
• The total water deficit
is shared by
extracellular and
intracellular
compartments .
Normonatremic
or
Isosmolar dehydration
• The degree
contraction is
intermediate.
Hyponatremic or
Hyposmolar dehydration
• The degree
contraction is largest
with increased ICW
volume.

Consequences of dehydration due to mixed water & salt ( sodium) depletion

Biochemical findings in Dehydration due to Mixed water & salt(Sodium) depletion
❖C. Biochemical findings in Dehydration due to Mixed water & salt
( Sodium) depletion include :
a) Fluid volume in both ECF & ICF reduced
b) Low blood pressure
c) Blood Urea (uremia ) & heme concentration raised
d) Diminished urine output (deceased urine volume )
e) Increase in plasma proteins
f) deceased urine sodium

Homeostatic mechanisms in dehydration
❖Homeostatic mechanisms in dehydration that compensate
dehydration include:
• Stimulation of thirst center with increased intake of water
• ADH secretion with increased water reabsorption ( except Diabetes
insipidus )

Homeostatic mechanisms in Dehydration due to Mixed water &
salt(Sodium) depletion
❖Decreased in intravascular volume has following consequences :
▪ Decreased in renal blood flow
▪ Stimulation of Aldosterone secretion
▪ Reabsorption of sodium
▪ Increase in plasma osmolality
▪ Stimulation of ADH secretion
▪ Water reabsorption with distribution of water to all compartments till
homeostasis
 In renal failure Homeostatic mechanisms do not operate .

Homeostatic mechanisms in Dehydration due to Mixed water &
salt(Sodium) depletion
Decreased in intravascular volume has following consequences :
Decreased in renal blood flow
Stimulation of Aldosterone secretion
Reabsorption of sodium
Increase in plasma osmolality
Stimulation of ADH secretion
Water reabsorption with distribution of water to all compartments till homeostasis

Management of Dehydration due to Mixed water & salt ( Sodium ) depletion
❖Management of Dehydration due to Mixed water & salt (Sodium)
depletion: intravenous infusion of saline

Management of Dehydration
• Treatment of choice of dehydration : Intake of plenty of water
• Intravenous administration of isotonic solution (usually 5% glucose ) to
patient who cannot take orally (and should be monitored carefully )
• if dehydration is accompanied by loss of electrolytes : oral/intravenous
administration of isotonic solution (usually 5% glucose ) until urine
volume exceeds 1500ml

Management of Dehydration in children

Osmotic imbalance and dehydration in Cholera:1
• Cholera is transmitted through water and food contaminated by the
bacterium Vibrio Cholerae.
• Vibrio Cholerae produces a toxin which stimulate intestinal cells to
secrete various ions ( Cl - , Na+ ,K+,HCO3 - ) into intestinal lumen.

Vibrio Cholerae produces a toxin which stimulate intestinal cells to secrete various ions
( Cl
-
, Na+,K+,HCO3-) into intestinal lumen
These ions collectively raise the osmotic pressure and suck water into lumen
Diarrhea (heavy loss of water 5-10 L /day )
Loss of dissolved salts and severe dehydration
Death if not treated with oral rehydration therapy (ORT)

Overhydration ( water intoxication )
Definition of Overhydration : state of pure water excess or water intoxication
• Retention of large quantity of water  deleterious effects
• excretion large volume of dilute urine ( when water without electrolyte
given )
❖Causes of Overhydration :
a) Excessive intake of large volumes of salt free fluids
b) Renal failure
c) Excessive administration of fluids parenterally
d) Hyper secretion of ADH ( syndrome of inappropriate ADH secretion –
SIADH )
This lead to decrease plasma electrolytes(dilution of ECF &ICF)
↓
Decreased osmolarity

Overhydration ( water intoxication )

Clinical Symptoms of Overhydration ( water intoxication )
1 . Nausea
2. Vomiting
3. Head ache
4.Muscular weakness /lethargy
5. Confusion
7 convulsion
8. Coma
9. Death

Clinical Symptoms of Overhydration ( water intoxication )

Biochemical findings in water excess
(overhydration )
❖Biochemical findings in water excess (overhydration ) include:
• Decrease in plasma sodium
• Decrease in ECF osmolality
• Increase in urine volume
• Decrease in plasma proteins
• Decrease in urine sodium: in Addison’s disease and increase in urine

Biochemical findings in water excess (overhydration )

Management in water excess
Management in water excess (overhydration ) include :
➢Restriction of water intake
➢Infusion of hypertonic saline if water intoxication occurs

Comparison of Overhydration ( water intoxication ) and Dehydration

Management of Dehydration and Overhydration ( water intoxication )

In edema along with water ,sodium content of body is also increased.
Increased serum sodium concentration (hypernatremia) is observed
in edema which occurs in pregnancy, Congestive cardiac failure and
cirrhosis.
 Pregnancy as a cause of edema :steroid and placental hormones
cause sodium and water retention
 Congestive cardiac failure as a cause of edema :
In early phases of congestive cardiac failure ,hydrostatic pressure on
venous side is increased ,so water is retained within the body leading to
edema .

Edema
Retention of water
within the body.
Decreased plasma
sodium
concentration
Aldosterone
secretion
 Sodium retention
 Water retention
Early phase of congestive cardiac failure 
Secondary Aldosteronism
Vicious
cycle
This Vicious cycle is broken by administration of
Aldosterone antagonist as drugs .

Secondary Aldosteronism in congestive cardiac failure
Hypostatic
pressure on
venous side
is increased
Primarily
Retention
of water
in the
body
Dilution of
sodium
concentra
tion
Aldosterone
secretion is
triggered.
Retention of
sodium is
retained along
with further
retention of
water.
This vicious cycle is broken
with administration of
Aldosterone
antagonist as a drug .
(T (This is known as
Secondary
This is known as
Secondary
Aldosteronism.
Aldosteronism)
his is known as
Secondary
In early phases of
congestive cardiac
failure

Management of edema
Management of edema involve :
a) Administration of diuretic drugs (increase sodium excretion along
with sodium, water is also excreted)
b) Sodium restriction in diet (in Congestive cardiac failure and
hypertension)

Diuretics in the management of edema and hypertension
❖Diuretics are drugs that stimulate water and sodium excretion so that
urine volume is increased .
Commonly used Diuretics :
a) Mannitol
b) Bendrofluazide
c) Furosemide
d) Spironolactone

Mechanism of action of Diuretics in the management of edema and hypertension

Diuretics in the management of edema and hypertension –Mechanism of action

Mechanism Action of Aldosterone

Secondary Aldosteronism and congestive cardiac failure
• In early phases of congestive cardiac failure hypostatic pressure on
venous side is increased, so water is primarily retained in the body.
• This causes dilution of sodium concentration, which triggers
Aldosterone secretion. This is known as Secondary Aldosteronism.
Thus sodium is retained along with further retention of water .
• This vicious cycle is broken with administration of Aldosterone
antagonist as a drug .

Secondary Aldosteronism
❖ Accumulation of water and sodium in isotonic amounts is seen in
Secondary Aldosteronism is associated with
• Early phases of congestive cardiac failure
• Chronic liver disease
• Nephrotic syndrome
• Kwashiorkor associated with hypoalbuminemia and edema
• Essential , malignant or renal hypertension without edema
Biochemical findings :
a) Hemodilution
b) Decrease in plasma protein and urea
c) Normo natremia or mild hypo natremia
d) Low urinary sodium
• Management involves the underlying cause

Causes of Secondary Aldosteronism

Management of Secondary Aldosteronism

Comparison of Primary and Secondary Aldosteronism

Comparison of primary and Secondary Aldosteronism

• Distribution of body water ( in ECF and ICF ) ,dehydration ,overhydration
can be illustrated by Water tank model.
• Inlet of Water tank = water intake ( oral )
• outlet of Water tank = Water output ( mainly urine )

Sodium metabolism and its clinical applications

Sodium metabolism and its clinical applications

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