This document discusses electrolyte disturbances and provides details about electrolyte composition in the body, osmolarity and osmolality of body fluids, regulation of electrolytes, and conditions involving electrolyte imbalances like dehydration, overhydration, and water intoxication. It focuses on sodium as a key electrolyte, outlining its functions, dietary requirements, and sources. The key points are that sodium and other electrolytes are essential for fluid balance, cell function, and acid-base regulation, and imbalances can result in serious health issues.

1. Electrolytes Disturbances
M.B.B.S., MD., Fellowship in Diab., PGDEM.,FRCEM
CONSULTANT EMERGENCY MEDICINE DIABETOLOGIST
ASSISTANT PROFESSOR, BIOCHEMISTRY

2. Introduction
Electrolytes are the compounds which readily dissociate in solution and
exist as ions i.e. positively and negatively charged particles.
For instance, NaCl does not exist as such, but it exists as cation (Na+) and
anion (Cl–). The concentration of electrolytes are expressed as
milliequivalents (mEq/l) rather than milligrams.
A gram equivalent weight of a compound is defined as its weight in grams
that can combine or displace 1 g of hydrogen.
One gram equivalent weight is equivalent to 1,000 milliequivalents.

3. •The following formula is employed to convert the concentration mg/l to
mEq/l.
mEq/l = mg per litre x valency
Atomic weight

4. Electrolyte composition of body fluids
Electrolytes are well distributed in the body fluids in order to maintain the
osmotic equilibrium and water balance
The total concentration of cations and anions in each body compartment
(ECF or ICF) is equal to maintain electrical neutrality.

5. Electrolyte composition of body fluids
There is a marked difference in the concentration of electrolytes (cations
and anions) between the extracellular and intracellular fluids.
Na+ is the principal extracellular cation while K+ is the intracellular cation.
 This difference in the concentration is essential for the cell survival which
is maintained by Na+ – K+ pump .
As regards anions, Cl– and HCO3 – predominantly occur in extracellular
fluids, while HPO4 – , proteins and organic acids are found in the
intracellular fluids.

6. Electrolyte composition of body fluids

7. Osmolarity and osmolality of body fluids
Osmolarity : The number of moles (or millimoles) per liter of solution.
Osmolality : The number of moles (or millimoles) per kg of solvent.
If the solvent is pure water, there is almost no difference between
osmolarity and osmolality.
However, for biological fluids (containing molecules such as proteins),
the osmolality is more commonly used. This is about 6% greater than
osmolarity.

8. Osmolality of plasma
Osmolality is a measure of the solute particles present in the fluid medium.
The osmolality of plasma is in the range of 285-295 milliosmoles/kg
Sodium and its associated anions make the largest contribution (~90%) to
plasma osmolality.
 Osmolality is generally measured by Osmometer.

9. Osmolality of plasma
For practical purposes, plasma osmolality can be computed from the concentrations (mmol/l)
of Na+, K+, urea and glucose as follows
2(Na+) + 2(K+) + Urea + Glucose
The factor 2 is used for Na+ and K+ ions to account for the associated anion concentration
(assuming complete ionization of the molecules). Since plasma Na+ is the most predominant
contributor to osmolality, the above calculation is further simplified as follows
Plasma osmolality = 2 x Plasma Na+

10. Osmolality of ECF and ICF
Movement of water across the biological
membranes is dependent on the osmotic pressure
differences between the intracellular fluid (ICF)
and extracellular fluid (ECF).
 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.
 As such, there is no net passage of water
molecules in or out of the cells, due to this osmotic
equilibrium.

11. Regulation of electrolyte balance
Electrolyte and water balance are regulated together and the kidneys play a
predominant role in this regard.
 The regulation is mostly achieved through the hormones :
 aldosterone
 ADH
 renin-angiotensin
ANF (atrial natriuretic factor)

12. Aldosterone : It is a mineralocorticoid produced by adrenal cortex. Aldosterone
increases Na+ reabsorption by the renal tubules at the expense of K+ and H+
ions. The net effect is the retention of Na+ in the body.
Antidiuretic hormone (ADH) : An increase in the plasma osmolality (mostly
due to Na+) stimulates hypothalamus to release ADH. ADH effectively
increases water reabsorption by renal tubules.

13. Renin-angiotensin : The secretion of aldosterone
is controlled by renin-angiotensin system.
 Decrease in the blood pressure (due to a fall in
ECF volume) is sensed by juxtaglomerular
apparatus of the nephron which secrete renin.
Renin acts on angiotensinogen to produce
angiotensin I.
The angiotensin I is then converted to angiotensin
II which stimulates the release of aldosterone.

14. Atrial natriuretic factor (ANF) : ANF or atriopeptin is a 28-amino acids containing
peptide.
 It is produced in the atrium of heart in response to increased blood volume,
elevated blood pressure and high salt intake.
ANF acts on kidneys to increase GFR, sodium excretion and urine output.
Thus ANF opposes the actions of renin and aldosterone (which increase salt
retention and blood pressure).

15. Na+ concentration and ECF
It is important to realise that Na+ and its anions (mainly Cl–) are confined to
the extracellular fluid.
The retention of water in the ECF is directly related to the osmotic effect of
these ions (Na+ and Cl–).
Therefore, the amount of Na+ in the ECF ultimately determines its
volume.

16. DEHYDRATION
Dehydration is a condition characterized by water depletion in the body. It may be due
to insufficient intake or excessive water loss or both.
Dehydration is generally classified into two types.
 Due to loss of water alone.
 Due to deprivation of water and electrolytes
Dehydration may occur as a result of diarrhea, vomiting, excessive sweating,
fluid loss in burns, adrenocortical dysfunction, kidney diseases (e.g. renal
insufficiency), deficiency of ADH (diabetes insipidus) etc.
CAUSES OF DEHYDRATION

17. Characteristic features of dehydration
There are three degrees of dehydration—mild, moderate and severe.
The salient features of dehydration are given hereunder
1. The volume of the extracellular fluid (e.g. plasma) is decreased with a
concomitant rise in electrolyte concentration and osmotic pressure.
2. Water is drawn from the intracellular fluid that results in shrunken cells and
disturbed metabolism e.g. increased protein breakdown.
3. ADH secretion is increased. This causes increased water retention in the body and
consequently urine volume is very low.

18. Characteristic features of dehydration
4. Plasma protein and blood urea concentrations are increased.
5. Water depletion is often accompanied by a loss of electrolytes from the body
(Na+, K+ etc.).
6. The principal clinical symptoms of severe dehydration include increased pulse rate,
low blood pressure, sunken eyeballs, decreased skin turgor, lethargy, confusion and
coma.

19. TREATMENT
• The treatment of choice for dehydration is intake of plenty of water.
• In the subjects who cannot take orally, water should be administered intravenously in
an isotonic solution (usually 5% glucose).
• If the dehydration is accompanied by loss of electrolytes, the same should be
administered by oral or intravenous routes.
• This has to be done by carefully monitoring the water and electrolyte status of the
body.

20. Osmotic imbalance and dehydration in cholera
Cholera is transmitted through water and foods, contaminated by the bacterium Vibrio
cholerae.
This bacterium produces a toxin which stimulates the intestinal cells to secrete various
ions (Cl–, Na+, K+, HCO3 – etc.) into the intestinal lumen. These ions collectively raise
the osmotic pressure and suck the water into lumen.
This results in diarrhea with a heavy loss of water(5–10 liters/day). If not treated in time,
the victims of cholera will die due to dehydration and loss of dissolved salts.
Thus, cholera and other forms of severe diarrhea are the major killers of young children
in many developing countries. Oral rehydration therapy (ORT) is commonly used to
treat cholera and other diarrheal diseases.

21. OVERHYDRATION
• Overhydration or water intoxication is caused by excessive retention of water in the
body.
• This may occur due to excessive intake of large volumes of salt free fluids, renal
failure, overproduction of ADH etc.
• Overhydration is observed after major trauma or operation, lung infections etc.
• Water intoxication is associated with dilution of ECF and ICF with a decrease in
osmolality.
• The clinical symptoms include headache, lethargy and convulsions.
• The treatment advocated is stoppage of water intake and administration of hypertonic
saline.

22. Water tank model
The distribution of body water (in the ECF and ICF), dehydration and
overhydration can be better understood by a water tank model.
The tank has an inlet and outlet, respectively, representing the water
intake(mostly oral) and water output (mainly urine) by the body.
Dehydration is caused when the water output exceeds the intake.
On the other hand, overhydration is due to more water intake and less output

24. Sodium
Sodium is the chief cation of the extracellular fluid. About 50% of body sodium is
present in the bones, 40% in the extracellular fluid and the remaining 10% in the soft
tissues
Biochemical functions :
1. In association with chloride and bicarbonate, sodium regulates the body’s acid base
balance.
2. Sodium is required for the maintenance of osmotic pressure and fluid balance.
3. It is necessary for the normal muscle irritability and cell permeability.
4. Sodium is involved in the intestinal absorption of glucose, galactose and amino
acids.
5. It is necessary for initiating and maintaining heart beat.

25. Dietary requirements
For normal individuals, the requirement of sodium is about 5-10 g/day which is mainly
consumed as NaCl.
For persons with a family history of hypertension, the daily NaCl intake should be less
than 5 g.
For patients of hypertension, around 1 g/day is recommended.
 It may be noted that 10 g of NaCl contains 4 g of sodium.

26. Sources:
The common salt (NaCl) used in the cooking medium is the major source of sodium.
The ingested foods also contribute to sodium.
The good sources of sodium include bread, whole grains, leafy vegetables, nuts, eggs
and milk.
Absorption
Sodium is readily absorbed in the gastrointestinal tract and, therefore, very little of it (<
2%) is normally found in feces. However, in diarrhea, large quantities of sodium is lost in
feces.

27. Plasma sodium :
In the plasma (serum), the normal concentration of sodium is 135-145 mEq/l.
Sodium is an extracellular cation, therefore, the blood cells contain much less
(35 mEq/l).
The mineralocorticoids, secreted by adrenal cortex, influence sodium
metabolism.
A decrease in plasma sodium and an increase in its urinary excretion are
observed in adrenocortical insufficiency.

28. Excretion
Kidney is the major route of sodium excretion from the body.
 As much as 800 g Na/day is filtered by the glomeruli, 99% of this is reabsorbed
by the renal tubules by an active process.
This is controlled by aldosterone.
Extreme sweating also causes considerable amount of sodium loss from the
body.

29. Hyponatremia
• This is a condition in which the serum sodium level falls below the normal.
CAUSES :
• Diarrhea, vomiting, chronic renal diseases, adrenocortical insufficiency
(Addison’s disease).
• Administration of salt free fluids to patients. This is due to overhydration.
• Decreased serum sodium concentration is also observed in edema which occurs in
cirrhosis or congestive heart failure.
• The manifestations of hyponatremia include reduced blood pressure and circulatory
failure.

30. Types of Hyponatremia

31. • Hyponatremia due to water retention is the most common biochemical
abnormality observed in clinical practice.
• Hyponatremic patients with out edema have water overload and they can be treated
by water restriction.
• Hyponatremia with edema is due to both water and sodium overload and will have
to be treated by diuretics and fluid restriction.
• Syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is a
condition with hyponatremia; normal glomerular filtration rate, and normal
serum urea and creatinine concentration.
• Urine flow rate is less than 1.5 L/ day. Symptoms are proportional to the rate of
fall off sodium and not to the absolute value.
Hyponatremia due to water retension

32. Hypertonic Hyponatremia
•Normal body sodium and additional drop in measured sodium due to presence
of osmotically active molecules in serum which cause a shift of water from
intracellular to extracellular compartment,
Examp: Hyperglycemia can cause a drop in serum sodium level of 1.6 mmol/L
for every 100 mg increase in glucose above 100 mg/dL.
• When glucose level exceeds 400 mg/dL this drop will also increase to 2.4
mmol/L for every 100 mg raise of glucose .
• The high level of glucose increases the osmolality leading to hypertonic
hyponatremia.
• A similar effect is seen during mannitol infusion also.

33. Normotonic hyponatremia
• Severe hyperlipidemia and paraproteinemia can lead to low measured
serum sodium levels with normal osmolality since plasma water fraction
falls.
• This pseudohyponatremia is seen when sodium is measured by flame
photometry, but not with ion selective electrode.

34. Treatment of hyponatremia
• Treatment of hyponatremia depends on cause, duration and severity.
• In acute hyponatremia, rapid correction is possible; but in chronic cases too
rapid correction may increase mortality by neurological complications.
• Effects of administered sodium should be closely monitored, but only after
allowing sufficient time for distribution of sodium, a minimum of 4-6
hours.

35. Treatment of hyponatremia
• Water restriction, increased salt intake, furosemide and anti-ADH
drugs are the basis of treatment for hyponatremia.
• The correction of hypernatremia and hypertonicity is to be done with care to
prevent sudden overhydration and water intoxication.
• But chronic cases should be treated slowly to prevent cerebral edema.
Rapid correction can also cause herniation and permanent neurologic
deficit.

36. Hypernatremia

37.  Cushing’s disease
 Prolonged cortisone therapy
 In pregnancy, steroid hormones cause sodium retention
 In dehydration, when water is predominantly lost, blood volume is decreased with
apparent increased concentration of sodium
 Exchange transfusion with stored blood
 Primary hyperaldosteronism
 Elderly patients with poor water intake, and inability to express thirst
 Excessive intake of salt
 Drugs:
 Ampicillin , Tetracycline , Anabolic steroids , Oral contraceptives , Loop diuretics
, Osmotic diuretics.
Causes of Hypernatremia

38. Potassium
• Potassium is the principal intracellular cation. It is equally important in the extracellular
fluid for specific functions.
Biochemical functions
1. Potassium maintains intracellular osmotic pressure.
2. It is required for the regulation of acid base balance and water balance in the cells.
3. The enzyme pyruvate kinase (of glycolysis) is dependent on K+ for optimal activity.
4. Potassium is required for the transmission of nerve impulse.
5. Adequate intracellular concentration K+ is necessary for proper biosynthesis of
proteins by ribosomes.
6. Extracellular K+ influences cardiac muscle activity.

39. Dietary requirements : 3-4 g/day.
Sources :
Banana, orange, pineapple, potato, beans, chicken, and liver. Tender coconut water is a
rich source of potassium.
Absorption :
The absorption of K+ from the gastrointestinal tract is very efficient (90%) and very
little is lost through feces. However, in subjects with diarrhea, a good proportion of K+
is lost in the feces.

40. Plasma potassium :
The plasma (serum) concentration of potassium is 3.5-5.0 mEq/l.
The whole blood contains much higher level of K+ (50 mEq/l), since it is
predominantly an intracellular cation.
Care should, therefore, be taken to avoid hemolysis of RBC for the estimation of
serum K+.
Excretion :
Potassium is mainly excreted through urine.
The maintenance of body acid-base balance influences K+ excretion.
Aldosterone increases excretion of potassium.

41. Hypokalemia
• Decrease in the concentration of serum potassium is observed due to
overactivity of adrenal cortex (Cushing’s syndrome)
 prolonged cortisone therapy, intravenous administration of K+ free fluids
 treatment of diabetic coma with insulin,
 prolonged diarrhea and vomiting.
Symptoms
 irritability, muscular weakness, tachycardia, cardiomegaly and cardiac arrest.
 Changes in the ECG are observed (flattened waves with inverted T wave)

43. Hyperkalemia
• Increase in the concentration of serum potassium is observed in
renal failure
adrenocortical insufficiency (Addison’s disease)
diabetic coma
severe dehydration
 intravenous administration of fluids with excessive potassium salts
SYMPTOMS
 Depression of central nervous system, mental confusion, numbness, bradycardia with
reduced heart sounds and, finally, cardiac arrest.
Changes in ECG are also observed (elevated T wave).

45. Chlorine
• Chlorine is a constituent of sodium chloride. Hence, the metabolism of chlorine and
sodium are intimately related.
• Biochemical functions
1. Chloride is involved in the regulation of acid-base equilibrium, fluid balance and
osmotic pressure. These functions are carried out by the interaction of chloride with
Na+ and K+.
2. Chloride is necessary for the formation of HCl in the gastric juice.
3. Chloride shift involves the active participation of Cl–.
4. The enzyme salivary amylase is activated by chloride.

46. Dietary requirements :
5-10 g.
Adequate intake of sodium will satisfy the chloride requirement of the body.
Sources :
Common salt as cooking medium, whole grains, leafy vegetables, eggs and milk.
Absorption :
In normal circumstances, chloride is almost totally absorbed in the gastrointestinal
tract.
Plasma chloride
The normal plasma concentration of chloride is 95-105 mEq/l

47. Excretion :
There exists a parallel relationship between excretion of chloride and sodium. The renal
threshold for Cl– is about 110 mEq/l.
Hypochloremia : A reduction in the serum Cl– level may occur due to vomiting,
diarrhea, respiratory alkalosis, Addison’s disease and excessive sweating.
Hyperchloremia : An increase in serum Cl– concentration may be due to
dehydration, respiratory acidosis and Cushing’s syndrome.

48. Thank you…