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
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
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
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
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
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
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
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
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