it explains the distribution of water in various compartments. how it is balanced in our body or regulated. with its disorders of water metabolism.

2. Fluid & Electrolyte Balance
Dr . N. Sivaranjani ,MD biochem
Asst prof.

3. 60% of body consists of fluid
Intracellular space
Extracellular space
Distribution of water in different body water
compartments depends on the solute
content of each
compartment
Osmolality of the intra and
extra-cellular fluid is the same, but
there is marked difference in the
solute content.Dr. N. Sivaranjani 3

4. Distribution of Body Water
Intravascular
Interstitial
IntracellularICF
ECF Na+
K+
Cl-
Essential for normal cell function
Provides medium for metabolic processes
spaces between cells
plasma-arteries, veins, capillaries
Cerebrospinal fluid, Pleural spaces, Synovial spaces
Peritoneal fluid spaces
Transcellular
1 L
Dr. N. Sivaranjani 4

5. Fluid composition varies with body fat, age and gender
75% water
ECF=45%,ICF=30%
65% water,
ECF= 25%, ICF = 40%
Adult female
50% water,
ECF=10-15%,
ICF=40%
fat cells contain little
water and lean tissue is
rich in water, the more
obese the person, the
smaller the percentage
of total body water.Dr. N. Sivaranjani 5

6. Human life is suspended in a saline solution having a salt concentration of 0.9%
Body fluids must remain fairly constant with regard to amount of H2O & specific electrolytes
Primary component of body fluid: Water
Women lower % body water than men
Total body water decreases with age
Dr. N. Sivaranjani
6

7. How importance is water
 Water provides a medium for transporting nutrients to cells and
wastes from cells and for transporting substances such as hormones,
enzymes, blood platelets, and red and white blood cells
 Water facilitates cellular metabolism and proper cellular chemical
functioning
 Water acts as a solvent for electrolytes and nonelectrolytes
 Helps maintain normal body temperature
 Facilitates digestion and promotes elimination
 Acts as a tissue lubricant
 Component in all body cavities [parietal, pleural… fluids]
Water is the
principal body
fluid which is
essential for
life.
Dr. N. Sivaranjani 7

8. Intake and output of water
Factors that Dictate Body Water Requirement
1) Amount needed to give the proper osmotic concentration
2) Amount needed to replace water lost excretion
Normal Routes of water gain and loss
INTAKE OUTPUTml/day ml/day
Exogenous :-
Fluid intake 1,500
Food 700
Endogenous :-
Metabolism 300
TOTAL 2,500
Insensible loss (skin + lung) 850
Feces 150
Urine (kidney) 1,500
TOTAL 2,500

9. Dr. N. Sivaranjani 9

10. Regulation of Body Fluid Compartments
Diffusion
 Molecules → from an area of ↑ concentration to an area of ↓
concentration
Osmosis
 is the movement of water through a semipermeable membrane to a
higher concentration of solutes.
Active Transport
 is movement of substance across permeable membrane and gradient;
requires energy and pump.
Filtration
 H2O & dissolved substances → from an area of high hydrostatic
pressure to an area of low hydrostatic pressure
Dr. N. Sivaranjani 10

11. Diffusion
High Solute Concentration Low Solute Concentration
Fluid
Solutes
Dr. N. Sivaranjani 11

12. Osmosis
Fluid
High Solution
Concentration,
Low Fluid
Concentration
Low Solute
Concentration,
High Fluid
Concentration
Controls body fluid movement between
ICF & ECF
Dr. N. Sivaranjani 12

13. Dr. N. Sivaranjani
13

14. Dr. N. Sivaranjani 14

15. Osmotic Pressure
The amount of hydrostatic pressure required to stop the flow of
water by osmosis
Osmolality
reflects the concentration of fluid that affects the movement of
water between fluid compartments by osmosis
Dr. N. Sivaranjani 15

16. Osmolality : Number of osmotically active particles present per
kilogram of water.
Osmolarity: Number of osmotically active particles present per litre of
water.
Electrolytes: Electrolytes are substances whose molecules dissociate into
ions when placed in solution
Ions : An ion is an atom or group of atoms with an electrical
charge.
Dr. N. Sivaranjani 16

17.  Normal plasma Osmolality = 285-292 mOsm/kg
 Plasma osmolality can be measured directly using the osmometer
or indirectly as the concentration of effective osmoles
Osmolality =2(Na+) + 2(K+) + Urea + Glucose, mmol/L.
 Plasma osmolality (mmol/kg) = 2x Plasma Na+(mmol/l)
 Estimated by doubling serum Na concentration
 Clinical uses :- diagnosis of disorders of water and electrolyte
balance and NKHC
Osmolality increases – Hyperglycemia, DKA, NKHC, Hypernatremia with water
loss (DI)
Decreased – Hyponatremia – water and Na gain (CCF), SIADH.Dr. N. Sivaranjani 17

18.  The difference in measured osmolality and calculated osmolality
called Osmolar Gap. (normal - numerically similar)
 Increase in osmotically active substances – Ethanol,
Mannitol, neutral and cationic amino acids.
 Fractional water content of plasma is reduced –
hyperlipidemia or hyperproteinemia .
Dr. N. Sivaranjani 18

19. In a healthy state, the osmotic pressure of ECF, mainly due to Na+ ions, is
equal to the osmotic pressure of ICF which is predominantly due to K+ ions
Dr. N. Sivaranjani
19

20. Tonicity - measure of transport of water across the biological system causing
change in cell volume.
0.9% Normal SalineDr. N. Sivaranjani
20

21. 0.9% Normal Saline
Dr. N. Sivaranjani
21

22. (0.45% NS)
< concentration of solutes as plasma
Causes H2O to move into cells & swell
(hemolysis)
Dr. N. Sivaranjani
22

23.  (3% NS)
 > concentration of solutes as plasma
 Causes H2O to draw out of cell
(shrink)
 Mannitol –treatment of cerebral
edema.
Dr. N. Sivaranjani
23

24. Dr. N. Sivaranjani
24

25. ELECTROLYTES
 Substances whose molecules dissociate into ions
(charged particles) when placed into water
Cations: positively-charged
Anions: negatively-charged
 Sodium – major cation of ECF
 Chloride - major anion of ECF
 Potassium – major cation of ICF
 Phosphate – major anion of ICF
Dr. N. Sivaranjani 25

26. ELECTROLYTE Composition
Electrolyte Conc Plasma (mEq/L) ICF
Sodium, Na+ 142 10
Potassium, K+ 5 150
Calcium, Ca++ 5 2
Magnesium, Mg++ 3 40
(155)
Chloride, Cl- 103 2
Bicarbonate, HCO3
- 27 10
Biphosphate, HPO4
- 2 140
Sulfate, SO4
-2 1 5
Protein 16 40
Organic acids 6 5
(155)
Dr. N. Sivaranjani 26

27. Functions of Electrolytes
 Promote neuromuscular irritability
 Regulate acid and base balance
 Regulate distribution of body fluids among body
fluid compartments
Dr. N. Sivaranjani 27

28.  are regulated together
 kidneys play a predominant role
 major regulatory factors are the hormones - Aldosterone,
ADH and
Renin angiotensin
Atrial natriuretic peptide
 Hypothalamic regulation - Stimulates thirst and ADH release
 Pituitary regulation - Releases ADH
 Adrenal cortical regulation – Releases Aldosterone
 Renal regulation - Primary organs for regulating fluid and electrolyte balance
Selective reabsorption of water and electrolytes
Renal tubules are sites of action of ADH and aldosterone
Electrolyte and water balance
Dr. N. Sivaranjani 28

29. Synthesis Action Action on sodium
and water
Aldosterone secreted by the zona
glomerulosa
of the adrenal cortex
regulates the
Na+ → K+ exchange and
Na+ → H+ exchange at
the renal tubules.
Sodium and water
retention
Anti-Diuretic
Hormone (ADH)
Under control of
hypothalamus, posterior
pituitary releases ADH
increase the water
reabsorption by the renal
tubules.
Retention of
water
Renin-
Angiotensin
System
release of renin by the
juxtaglomerular cells
Angiotensin-II BP by
vasoconstriction of the
arterioles.
It also stimulates
aldosterone production
Retention of
sodium and water
Atrial natriuretic
peptides
stimulation of atrial
stretch receptors
Inhibit renin and
aldosterone secretion –
cause elimination of sodium
Increases urinary
excretion of
sodium.Dr. N. Sivaranjani 29

30. DECREASED FLUID VOLUME
Stimulation of thirst
center in hypothalamus
Increase in thirst
↑ intake of water
INCREASES PLASMA OSMOLALITY
Dr. N. Sivaranjani 30

31. Posterior pituitary
gland
Osmoreceptors in
hypothalamus +↑Osmolarity
↑ADH
Kidney
↑H2O reabsorption
↑vascular volume and
↓osmolarity
Stress, hypoglycaemia,
Anesthetic agents, Heat,
Nicotine, Antineoplastic
agents, Narcotics,
Surgery
ANTIDIURETIC HORMONE REGULATION MECHANISMS
Fluid
volume
Increase permeability of renal
collecting ducts to water by
binding to V2 receptors –
cause insertion of water
channels to luminal
membrane

32. Juxtaglomerular cells↓Serum Sodium
↓Blood volume
↓Blood Pressure
↓renal blood flow Angiotensin I
Distal renal
tubules
Angiotensin II
Adrenal Cortex↑Sodium reabsorption (H2O
resorbed with sodium)
Angiotensinogen in
plasmaRENIN
Angiotensin-
converting enzyme
ALDOSTERONE
Via vasoconstriction of arterial smooth muscle
ALDOSTERONE-RENIN-ANGIOTENSIN SYSTEM
Increases Blood Pressure

33. INCREASED BLOOD VOLUME ,
INCRESED BLOOD PRESSURE
ATRIAL NATRIURETIC PEPTIDE RELEASE
Reduces in thirst
Decreased intake of water
STIMULATION OF ATRIAL STRETCH RECEPTORS
Inhibits release of ADH
Diuresis – increase urine output
Inhibits release of
Aldosterone
Decreases Na reabsorption
Natriuresis – Na excretion

34. Dr. N. Sivaranjani
34

35. Volume Disorders 2° Alteration in Sodium Balance
ECF Expansion
Isotonic Inc N N Water and Na retention – Edema- 2̊ Cardiac failure
2̊ Hyper- aldosteronism due to hypoalbunemia.
Hypertonic Inc Dec Inc Na retention due to excess mineralocorticoid –
cushing’s syndrome or conn’s syndrome
Hypotonic Inc Inc Dec water retention due to ADH excess or
Glomerular dysfuncion
Volume ECF ICF Conditions
Disorder Vol. Vol. Osmolality

36. ECF Contraction
Isotonic Dec N Normal loss of Na & water
common cause – loss of GIT fluid
SI obstruction, SI fistulae, paralytic ileus
Hypertonic Dec Dec Increased water depletion
Diarrhea – Commonest cause
Diabetes insipidus - rare
Hypotonic Dec Inc Decreased sodium depletion
infusion of IV fluids with low Na-dextrose
aldosterone deficiency- Addison’s disease
Volume ECF ICF Conditions
Disorder Vol. Vol. Osmolality

37. • Dehydration • Fluid Overload
Dr. N. Sivaranjani 37

38. Dehydration / water depletion
 Pure (tissue) water loss – less common
 Depletion of Na and water – more common
 and hypovolemia to sodium loss and thus loss of blood volume.
Dr. N. Sivaranjani 38

39. Causes of water depletion :
 Decreased intake of water –
• Inadequate water supply
• Mechanical obstruction for drinking
• Impaired response of thirst center – Comatose patient
 Increased loss of water –
• Increased renal loss of water – RTA, DI
• Increased loss of water from skin – Burns,
excessive sweating
• Increased loss through lungs – hyperventilation
• Increased loss of gut – vomiting ,diarrhea
Dr. N. Sivaranjani 39

40. Earliest Detectable Signs
 low BP
Dry skin and mucous membranes
Sunken eye balls, fontanels
Circulatory Failure (coolness, mottling of
extremities)
Loss of skin elasticity
Delayed cap refill
 lethargy , confusion and coma
Dr. N. Sivaranjani 40

41.  Skin turgor assessment – this
assessment can be done on the forearm.
Skin that does not flatten immediately
after release is called “tenting”, an
example of fluid volume deficit.
 Dry and cracked lips
 Sunken eyes
 Thirst and
discomfort
Dr. N. Sivaranjani 41

42. Loss of Skin
Elasticity due
to dehydration
Dr. N. Sivaranjani 42

43. Dr. N. Sivaranjani 43

44. Manifestations of ECF Deficit (Dehydration)
Signs & Symptoms
 Weight loss
Blood pressure drop
Delayed capillary refill
Oliguria
Sunken fontanel
Decreased skin turgor
Physiologic Basis
Decreased fluid vol.
Inadequate circ. Blood
Decreased vascular volume
Inadequate kidney circ.
Decreased fluid volume
Decreased interstitial fluid
Dr. N. Sivaranjani 44

45. Degrees of Dehydration
Mild Moderate Severe
Fluid Vol loss <50ml/kg 50-90ml/kg >100 ml/kg
Skin Color Pale Gray Mottled
Skin Elasticity Decreased Poor Very Poor
M.M. Dry Very Dry Parched
U.O. Decreased Oliguria Marked
Oliguria
BP Normal Normal or
lowered
Lowered
Pulse Normal or
Increased
Increased Rapid,
thready
Dr. N. Sivaranjani 45

46. Biochemical finding :
 plasma sodium – increased
 urine volume – decreased
 urine concentrated
Treatment :
Aim - Expand ECF volume and improve circulatory
and renal function
 plenty of water
 Treatment of underlying causes
 Replacement of fluid deficit –
5% dextrose

47. Water intoxication / water excess /over hydration
 predominant water excess
Decrease in serum Na+
 Causes :
Excessive intake of water
 Compulsive drinking of water – psychogenic polydypsia
 Excessive administration of fluid through parental route
Impaired renal excretion of water
 Severe renal failure
 SIADH syndrome of inappropriate ADH
 Drugs acting as vasopressin agonist
Dr. N. Sivaranjani 47

48. SIADH –
 Plasma hypo-osmolality
 Normal renal , thyroid, adrenal function
 Increased urine Na excretion
 Dilutional hyponatremia
 Elevated serum ADH
Clinical features
Behavioral disturbances
Confusion
Headache
Muscle twitching
Convulsion
Coma

49. Biochemical finding :
 plasma sodium – decreased
 decreased plasma osmolality
 urine dilated
Treatment :
Treatment of underlying causes
 Fluid restriction
SIADH – vasopressin antagonist

50. 50
Edema
the accumulation of fluid within the interstitial space
Causes:
•increased hydrostatic pressure
• venous obstruction, lymphedema, CHF, renal failure
•lowered plasma osmotic pressure (protein loss)
• liver failure, malnutrition, burns
•increased capillary membrane permeability
• Inflammation, sepsis
Dr. N. Sivaranjani

51. Dr. N. Sivaranjani
51