Water how much is the phs

1. Limited Universities Press
Rafi M D: Textbook of Biochemistry for Medical Students (2nd Edn)
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Section VI
Clinical Biochemistry
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2. Limited Universities Press
Rafi M D: Textbook of Biochemistry for Medical Students (2nd Edn)
Water and Electrolytes

3. Limited Universities Press
Rafi M D: Textbook of Biochemistry for Medical Students (2nd Edn)
WATER
 Role of water
 Distribution of water in the body
 Water balance
 Water input
 Water outout

4. Limited Universities Press
Rafi M D: Textbook of Biochemistry for Medical Students (2nd Edn)
DISTRIBUTION OF WATER IN THE BODY

5. Limited Universities Press
Rafi M D: Textbook of Biochemistry for Medical Students (2nd Edn)
WATER BALANCE IN HUMANS

6. Limited Universities Press
Rafi M D: Textbook of Biochemistry for Medical Students (2nd Edn)
ELECTROLYTES – DISTRIBUTION AND
BALANCE
 Electrolytes are well distributed in body
fluids to maintain osmotic equilibrium and
water balance. Na+ is the principal cation of
ECF, while K+ is the chief cation of ICF.
 Osmolarity: Osmotic pressure exerted by the
number of moles per litre of solution.
 Osmolality: Osmotic pressure exerted by the
number of moles per kg of solvent.
Osmolality is more commonly used than
osmolarity in clinical practice.
(Continued…

7. Limited Universities Press
Rafi M D: Textbook of Biochemistry for Medical Students (2nd Edn)
Composition of electrolytes in body fluid compartments (mEq/L)
Extracellular
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8. Limited Universities Press
Rafi M D: Textbook of Biochemistry for Medical Students (2nd Edn)
Osmolality of plasma: The osmolality of
plasma is in the range of 280–300
milliosmoles/kg
…Continues)
(Continued…

9. Limited Universities Press
Rafi M D: Textbook of Biochemistry for Medical Students (2nd Edn)
Constituents contributing to plasma osmolality
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10. Limited Universities Press
Rafi M D: Textbook of Biochemistry for Medical Students (2nd Edn)
 Regulation of water and electrolyte balance
 Aldosterone
 Anti-diuretic hormone (ADH)
 Renin-Angiotension system
…Continues)

11. Limited Universities Press
Rafi M D: Textbook of Biochemistry for Medical Students (2nd Edn)
Causes of dehydration: Dehydration may occur
as a sequel to diarrhea, vomitting, excessive
sweating, fluid loss in burns, adrenocortical
dysfunction, kidney diseases (e.g. renal
insufficiency), deficiency of ADH (diabetes
insipidus).
Features of dehydration
The clinical manifestations of severe
dehydration include increased pulse rate, low
blood pressure, sunken eyeballs, decreased skin
turgor, lethargy, confusion and eventually coma.
DEHYDRATION

12. Limited Universities Press
Rafi M D: Textbook of Biochemistry for Medical Students (2nd Edn)
Treatment of dehydration
● Intake of plenty of water is a simple and
effective method of treating dehydration. In
persons who cannot ingest it orally, water
can be given via a nasogastric tube. If this is
not possible, water should be given
intravenously (IV) in an isotonic solution,
usually as 5% glucose (5% dextrose). If there
is an associated electrolyte depletion,
dextrose-saline (4% dextrose, 0.18% NaCl)
should be given intravenously.
TREATMENT
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13. Limited Universities Press
Rafi M D: Textbook of Biochemistry for Medical Students (2nd Edn)
● When sodium depletion alone is the problem,
giving intravenous isotonic fluid – normal
saline (0.9% NaCl) or plasma expanders or
albumin is the first line of management of
salt deficit. After restoring the intravascular
volume, the underlying cause must be
treated.
…Continues)

14. Limited Universities Press
Rafi M D: Textbook of Biochemistry for Medical Students (2nd Edn)
ELECTROLYTES - SODIUM
Sodium is the principal cation of the
extracellular fluid.
Dietary sources: Common salt (NaCl) used in
cooking medium is the major source of
sodium. Whole grains, nuts, eggs, leafy
vegetables, milk and bread are good sources
of Na+.
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15. Limited Universities Press
Rafi M D: Textbook of Biochemistry for Medical Students (2nd Edn)
Dietary requirements
The recommended dietary allowance (RDA) of
sodium is about 5–10 g/day.
Sodium in ECF: The normal concentration of
sodium in plasma is 135–145 mEq/L.
…Continues)
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16. Limited Universities Press
Rafi M D: Textbook of Biochemistry for Medical Students (2nd Edn)
Biochemical functions
1. Sodium regulates the body's acid–base
balance along with chloride and bicarbonate.
It is involved in forming a bicarbonate buffer
system (NaHCO3–H2CO3) and a phosphate
buffer system (NaH2PO4–Na2HPO4). These
buffer systems play an important role in the
acid–base balance.
2. Sodium plays a role in maintaining osmotic
pressure and fluid balance.
…Continues)
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17. Limited Universities Press
Rafi M D: Textbook of Biochemistry for Medical Students (2nd Edn)
3. Sodium is important in muscle excitability
and is necessary for initiating and
maintaining the heartbeat.
4. Sodium plays a role in cell permeability.
…Continues)

18. Limited Universities Press
Rafi M D: Textbook of Biochemistry for Medical Students (2nd Edn)
Hyponatremia
When the plasma sodium level falls below
normal, the condition is referred to as
hyponatremia. The causes include
DISEASES STATES
1. Vomitting
2. Diarrhea
3. Burns
4. Addison's disease (adrenocortical
insufficiency)
5. Renal tubular acidosis (tubular reabsorption
of sodium is defective)
6. Severe sweating (Continued…

19. Limited Universities Press
Rafi M D: Textbook of Biochemistry for Medical Students (2nd Edn)
Hypernatremia
This condition is marked by an elevation in the
plasma sodium level.
Causes of hypernatremia include
1. Cushing's syndrome (adrenocortical
hyperactivity)
2. Prolonged cortisone therapy
3. Pregnancy (steroid hormones cause sodium
retention in the body to some extent)
4. Dehydration (when water is lost, the blood
volume is decreased with apparent increase in
the concentration of sodium)
…Continues)

20. Limited Universities Press
Rafi M D: Textbook of Biochemistry for Medical Students (2nd Edn)
Potassium is the major intracellular cation.
Dietary sources: Banana, orange, pineapple,
potato, beans, chicken and organ meat (liver)
are good sources and coconut water has very
high content of potassium.
RDA: About 3–4 g/day.
Potassium in the ECF and ICF: The plasma
concentration of potassium is 3.5–5.0 mEq/L.
POTASSIUM

21. Limited Universities Press
Rafi M D: Textbook of Biochemistry for Medical Students (2nd Edn)
1. Potassium maintains intracellular osmotic
pressure. Movement of water across the
biological membranes is dependent on the
osmotic pressure differences between ICF
and ECF. In a healthy state, the osmotic
pressure of ECF (mainly due to Na+ ions) is
equal to the osmotic pressure of ICF
(contributed by K+ ions). As such, there is no
net passage of water molecules in or out of
the cells maintaining osmotic equilibrium.
BIOCHEMICAL FUNCTIONS
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22. Limited Universities Press
Rafi M D: Textbook of Biochemistry for Medical Students (2nd Edn)
2. It plays a role in the regulation of acid–base
and water balances in the cells.
3. The enzyme, pyruvate kinase (glycolysis) is
dependent on K+ for its optimal activity.
4. Potassium is required for the transmission of
nerve impulses.
…Continues)

23. Limited Universities Press
Rafi M D: Textbook of Biochemistry for Medical Students (2nd Edn)
DISEASE STATES
Hypokalemia
Hypokalemia is manifested as muscular
weakness, impaired myocardial contractility
leading to cardiac arrhythmias and even cardiac
arrest.
Hypokalemia is observed in hyperactivity of the
adrenal cortex (Cushing's syndrome).
(Continued…

24. Limited Universities Press
Rafi M D: Textbook of Biochemistry for Medical Students (2nd Edn)
Hyperkalemia
Hyperkalemia, leads to ventricular arrhythmia,
ventricular fibrillation, bradycardia and may
lead to cardiac arrest.
Decreased potassium excretion can occur in
mineralocorticoid deficiency (Addison's
disease) and by potassium sparing diuretics.