Major intra and extracellular electrolytes

Major Intra- &
Extracellular Electrolytes
Abhishek B Rai

Electrolytes
Electrolytes are the substances that ionize when dissolved in a suitable solvent
like water.
Eg:
NaCl, KCl, CaCl2, MgCl2
NaHCO3,
KH2PO4,
K2SO4,

Electrolytes
Body fluids are aqueous solutions of organic and inorganic substances.
Different body fluids have different composition based on their functions and can
be classified into:
• Fluid present inside cells. (Comprise 45-50% body weight), Cytoplasm.
Intracellular fluid
• Fluid present outside cells
• Interstitial Fluids (Comprising 12-15% body weight)
• Vascular Fluids/Plasma (Comprising 4-5% body weight)
Extracellular fluid

Electrolytes
All the body fluids are separated from each other by a selectively permeable
membrane (permeable to water and certain organic/inorganic entities &
impermeable to large molecules) having selectivity for different substances like
Na+, K+, Mg+2 etc.
Composition of each fluid i.e. electrolyte pattern is maintained both ionically as
well as osmotically by different body mechanisms under normal circumstances.
“Maintenance of a constant environment in various cells, tissues and body
fluids physically as well as chemically is termed homeostasis”. Mainly including
pH control, ionic balance, osmotic balance etc. in different body fluids.”
Common inorganic electrolytes associated with homeostasis include Na+, K+,
Ca+2, PO4
-3, HPO4
-2, H2PO4
-1, Cl-, CO3
-2, HCO3
-, Mg+2, Fe+3, Fe+2, I-, Zn+2, Cu+2,
Co+2, Mn+2 etc.

Electrolytes
All the electrolytes have a definite concentration pattern in different body fluids
and they are distributed accordingly.
Some of them are required in trace quantities like Mo, Cr+3, Se etc. whereas
some are required in quantities as high as 5-10 grams like NaCl.
Their absorption, metabolism and primary physiological functions vary
considerably.
Their deficiency as well as excessiveness may lead to various clinical
manifestations of various metabolic disorders.
Primary functions of electrolytes:
➢ Maintenance of electrolyte balance, including acid-base balance and osmotic
equilibrium in various body fluids.
➢ To facilitate specific metabolic function through supply of specific ion to body
fluids associated with particular cell/tissue/organ.

Electrolytes
Major Electrolytes include Na+, K+, Ca+2, Mg+2, PO4
-3, HPO4
-2, H2PO4
-1, Cl-,
HCO3
- etc.
Electrolyte Extracellular conc.
(mEq/lit)
Intracellular conc.
(mEq/lit)
Sodium (Na+) 142 10
Potassium (K+) 5 160
Calcium (Ca+2) 5 -
Magnesium (Mg+2) 2 35
Total Cations 154 205
Chloride (Cl-) 105 2
Bicarbonate (HCO3
-) 25 8
Phosphate (HPO4
-2) 2 140
Sulphate (SO4) 1 -
Organic Acids (RCOO-) 5 -
Proteins 16 55
Total anions 154 205

Functions of major physiological ions
Chloride(Cl-):
Major extracellular ion.
Amount present: 50 mEq/Kg
Daily requirement: 5-10 gm as NaCl.
Main sources: table salt, animal food.
Absorption: Absorbed completely.
Elimination: Eliminated with urine from blood by glomerular filtration and reabsorbed by DCT. Some
amount through sweat.
Functions: maintenance of hydration, osmotic pressure, normal electrolyte balance, acid-base balance, gastric
acid.
Clinical condition in deficiency: Hypochloremia
Clinical condition in excessiveness: Hyperchloremia

Sodium(Na+):
Major extracellular ion. (Constitute ~90% extracellular cations)
Amount present: 1.8 g/Kg
Daily requirement: 3-5 gm as NaCl.
Main sources: table salt, salty foods, baking soda, some vegetables, animal food.
Absorption: Absorbed completely and readily.
Elimination: Eliminated with urine from blood by glomerular filtration and reabsorbed by DCT. Some
amount through sweat. Body content regulated by kidneys; Aldosterone promotes reabsorption from DCT.
Functions: maintenance of hydration, osmotic pressure, buffer constituent, acid-base balance, cell membrane
permeability, muscle contraction (muscle irritability), Carbon dioxide transport, transmission of nerve impulse
in nerve fibers
Clinical condition in deficiency: Hyponatremia,
Clinical condition in excessiveness: Hypernatremia

Calcium(Ca+2):
Almost 99% present in bones and teeth. Remaining mainly in extracellular fluid
Amount present: 22 g/Kg
Daily requirement: 1 gm
Main sources: Milk and milk products, eggs, green vegetables, some fishes.
Absorption: Absorbed poorly(~20-40%); varies depending upon body requirements; Vit. D, lactose & acidity
increases the absorption whereas fat, phytate, oxalate, low dietary phosphorous intake decreases the
absorption.
Elimination: Eliminated in feces. Blood Calcium levels along with phosphate levels and their mobilization
into bones are controlled by parathyroid hormone.
Functions: Formation of apatite, hardening of bones and teeth, blood coagulation, muscle contraction,
neuromuscular irritability, cell membrane permeability.
Clinical condition in deficiency: Hypocalcemia, rickets and poor growth in children, hyperexcitability,
tetany
Clinical condition in excessiveness: Hypercalcemia, fatigue, muscle weakness, constipation, anorexia,
irregular cardiac functions, renal failure.

Bicarbonate(HCO3
-):
Present mainly in extracellular fluids
Amount present: 25-30 mEq/l blood
Daily requirement: traces
Main sources: Citrous fruits, milk etc.
Absorption: Orally taken bicarbonate salts will be neutralized by gastric acid; organic acid radicals lactate,
citrate etc are converted into bicarbonate invivo, some CO2 is converted into carbonic acid and bicarbonate
ions.
Elimination: in the form of CO2 through lungs.
Functions: Maintenance of physiological acid base balance, CO2 transport, maintenance of hydration, gastric
acid, electrolyte balance.
Clinical condition in deficiency: Metabolic acidosis viz in uncontrolled diabetes with ketosis, renal disease,
poisoning by acid salt, excessive loss of intestinal fluid by vomiting/diarrhea/colitis, hyperphea
Clinical condition in excessiveness: Metabolic alkalosis, intake of large large quantities of alkali.

Phosphate(PO4
-3):
Anion present mainly in intracellular fluids
Amount present: 12g/kg
Daily requirement: 800 mg
Main sources: Milk and dairy products, oatmeal, wholegrains, legumes, nuts egg yolk, liver, kidney etc.
Absorption: Absorbed from intestine.
Elimination: Mainly in urine; small amount in feces.
Functions: Predominant constituent of bones and teeth, constituent of HPO4
-2/H2PO4
-1 buffer, cell
phosphoprotein, cell phospholipids, nucleoproteins, hexose phosphates, metabolic intermediates & cofactors,
ATP, NAD, FAD etc.
Clinical condition in deficiency: Hypophosphatemia
Clinical condition in excessiveness: Hyperphosphatemia.

Potassium(K+):
Cation present mainly in intracellular fluids. Intracellular concentration is 23 times more than extracellular
concentration
Amount present: 2.6 g/kg
Daily requirement: 1.5 – 4.5 g
Main sources: Milk and dairy products, wholegrains, legumes, vegetables, meat.
Absorption: Absorbed rapidly. Active transport Na/K pump
Elimination: Mainly in urine by kidneys.
Functions: Electrolyte, acid-base and water balance, constituent of physiological buffer, muscle contraction,
membrane transport, CO2 transport.
Clinical condition in deficiency: Hypokalemia
Clinical condition in excessiveness: Hyperkalemia.

Magnesium(Mg+2):
Cation present mainly in intracellular fluids.
Amount present: 0.5 g/kg
Daily requirement: 300 mg
Main sources: vegetables, legumes, nuts, Milk, wholegrains, beans.
Absorption: Absorbed slowly, absorption retarded by alkaline media
Elimination: Unabsorbed portion is excreted in feces, absorbed magnesium is excreted through urine, bile
and intestinal secretions.
Functions: Part of several enzymes involving phosphate metabolism (eg. transferase), constituent of bones,
teeth, essential for protein synthesis. Assures smooth functioning of neuromuscular junctions.
Clinical condition in deficiency: Confusion, tremors, choreiform movements, vasodilatation,
hyperirritability.
Clinical condition in excessiveness: Hypermagnesemia, nervous system depression, anesthesia, paralysis of
skeletal muscles.

Electrolyte imbalance
Physiological condition when distribution of electrolytes disturb. Such situations if
persists for longer durations can lead to prolonged fever, severe vomiting/diarrhea
etc.
Body tries to balance the electrolytic composition of different body fluids by
homeostasis in normal circumstances.
When the imbalance is beyond the capacity of body homeostasis or it can’t be
balanced by body itself, replacement by deficient electrolytes and discontinuing
the intake of electrolytes which are in excess can restore the normal electrolyte
balance.
The electrolyte imbalance can be corrected by appropriate administration of
formulations containing electrolytes, acids and bases, blood products,
carbohydrates, amino acids, proteins etc.

Conditions responsible for electrolyte imbalance
S. No. Conditions leading to fluid and electrolyte
imbalance
Management of electrolytes required
01. Accident, hemorrhage, surgery etc. Fluid and electrolytes
02. Diarrhea, vomiting, dehydration due to GI infection
or ingestion of toxic/allergic substances
Fluid and electrolytes / rehydration therapy
03. Drug induced electrolyte elimination (Thiazide or
loop diuretic/ natri-uretic drugs)
Administration of appropriate salt (eg.
Nacl/KCl)
04. Retention of electrolytes due to excessive use of salts Fluid free from excessive electrolyte
05. Metabolic disorder leading to acidosis or alkalosis Appropriate electrolyte preparation for acute
conditions to restore normalcy & treatment of
underlaying cause
06. Deficiency of essential ions; nutritional/excessive
elimination
Appropriate salt
07. Excessive presence of specific ion Discontinuing the intake of that salt &
treatment of underlaying cause

Electrolytes used in replacement therapy
What so ever the reason, when there is electrolytic imbalance inside the body and
bodily homeostatic mechanisms are not able to rebalance, replacement therapy is
given.
The electrolytes which are in excess are replaced by the electrolytes in deficiency.
Commonly used electrolytes for replacement therapy include Sodium chloride,
Potassium Chloride, Calcium Gluconate, Potassium gluconate, Calcium lactate,
dibasic calcium phosphate and magnesium sulphate,

Sodium Chloride
Chemical Formula: NaCl
Mol. Wt. 58.44
Synonym: Common Salt, Natrii Chloridum, Sod.Chlor.
Sodium chloride is one of the most essential electrolyte involved in maintaining
osmotic pressure of Blood and body tissues.
Major component of extracellular fluids. Normal plasma contains 140 mEq/L of
Na+ and 100 mEq/L of Cl-.
Daily dietary intake of NaCl is 5 – 12 gm as a taste enhancer. Equivalent amount
is excreted from urine and sweat maintaining the electrolyte balance.
If taken in excess, it works as saline diuretic.
In nature, NaCl is distributed abundantly in the form of salt rocks/deposits & salt
lakes. Sea water can have 2.5-3% NaCl.

Sodium Chloride
Preparation:
From Rock Salt: Bore hills are drilled in rock salt deposits and water is run down
to rock salt strata. Sodium chloride is dissolved in water forming Brine solution.
The clear brine solution is pumped above to the surface and its water is evaporated
with the help of triple effect evaporators to obtain Sodium Chloride.
From Sea water: Sea water contains around 3-3.8% of different salts out of which
75-80% is NaCl. This has been main source for manufacture of NaCl for hundreds
of years. Sea water is filled in small artificial lakes/shallow pans/ shallow tanks
and allowed to get evaporated. The impurities are removed by dissolving so
obtained salt in water and filtering it. Alum and Lime are added to settle down all
the suspended impurities
In Pure form NaCl is prepared by passing HCl gas through a Conc. Aqueous
solution of Common salt. HCl gas dissolves in water forming hydrochloric acid.
NaCl being insoluble in hydrochloric acid gets crystallized leaving the impurities

Sodium Chloride
Properties:
Colorless crystals or white crystalline powder. Odorless having saline taste.
Freely soluble in water and more soluble in boiling water, soluble in glycerin and
slightly soluble in alcohol.
Storage:
As NaCl is hygroscopic in nature, it should be kept stored in tightly closed
containers.
Solution on storage may cause separation of small solid glass particles from glass
containers.
Dose:
Orally 3 – 6 g/day; IV infusion as per requirements.

Sodium Chloride
Uses:
Electrolyte replenisher.
0.9% solution as NS, as wet dressing for irrigating body cavities/wounds/tissues.
As IV injection or infusion in electrolyte depleted situations.
In Oral Rehydration Therapy.
Hypertonic solution as emetic.
Saline diuretic (For Bromide/iodide poisoning).
Taste Enhancer.
Assay:
Weigh 0.5g NaCl and dissolve in 50 ml water, titrate with 0.1N AgNO3. using
solution of potassium chromate.

Sodium Chloride
Preparations:
Sodium Chloride Injection: (NaCl Intravenous Infusion):
0.9% w/v (±0.05%) sterile isotonic solution of NaCl in water for injection.
Contains no antimicrobial agents. The solution must be clear.
Used as fluid and electrolyte replenisher; isotonic vehicle; irrigation solution.
Stored in single dose container of glass/plastic.
Sodium Chloride hypertonic Injection: (Hypertonic saline)
1.6% w/v (±0.08%) sterile solution of NaCl in water for injection containing no
antimicrobial agents. The solution must be clear.
Used as fluid and electrolyte replenisher.

Sodium Chloride
Preparations:
Compound Sodium Chloride Injection: (Ringer’s Injection):
0.86%w/v (±0.04%) NaCl, 0.03% w/v (±0.0015%) KCl and 0.033% w/v
(±0.003%) CaCl2.2H2O sterile solution in water for injection containing no
antimicrobial agents. Filtered to make it clear and autoclaved for sterilization.
Used as fluid and electrolyte replenisher.
Compound Sodium Chloride Solution: (Ringer’s Solution)
Solution of 0.86%w/v (±0.04%) NaCl, 0.03% w/v (±0.0015%) KCl and 0.033%
w/v (±0.003%) CaCl2.2H2O in purified water.
Used as irrigation solution for external use.
Stored in tightly closed container.

Sodium Chloride
Preparations:
Sodium Chloride & Dextrose Injection: (NaCl & Dextrose IV infusion):
Sterile solutions of NaCl and Dextrose containing not less than 95.0% and not
more than 105.0% of the stated amounts. Official injections include
Used as fluid, nutrient and electrolyte replenisher.
Stored in single dose container of glass/plastic in cool place. Should not be used if
visible turbidity is there.
%NaCl %C6H12O6 %NaCl %C6H12O6 %NaCl %C6H12O6
0.11 5 0.33 5 0.9 5
0.18 5 0.45 5 0.9 10
0.2 5 0.45 5 0.9 10
0.225 5 0.45 10 0.9 25
0.3 5 0.9 2.5

Sodium Chloride
Preparations:
Sodium Chloride Tablets:
Tablets of strengths 0.3g, 0.6g, 1.0g, 2.25g prepared with some lubricant and
binding agents.
Used as electrolyte replenisher.
Stored in tightly packed container.
Sodium Chloride Solution: (Normal saline solution)
0.9% w/v isotonic solution.
Used as irrigation solution, wet dressing and isotonic vehicle.
Stored in tightly closed container.

Potassium Chloride
Chemical Formula: KCl
Mol. Wt. 74.55
Synonym: Kalii Chloridum.
Potassium chloride is an important electrolyte, potassium being major intracellular
cation whereas chloride being major extracellular anion.
It occurs in the form of Carnallite (MgCl2.KCl.6H2O), Sylvite (Mixture of NaCl
& KCl) and as a bed of solid salt of complex composition at Searles Lake, USA.
Preparation:
By Fractional crystallization or special fusion or floatation of natural minerals.
In laboratory it can be prepared by action of HCl on Potassium carbonate.
K2CO3 + 2HCl -----------→ 2KCl + CO2 + H2O

Potassium Chloride
Properties:
Colorless, prismatic or cuboidal crystals or white granular powder. Odorless with
saline taste. Freely soluble in water and slightly more soluble in boiling water,
practically insoluble in alcohol and ether.
Uses:
In the treatment of potassium deficiency as oral replacement therapy.
Treatment of Mysthenia gravis
Antidot for digitalis intoxication.
Dose:
500 mg to 8 gm daily as per requirement.
Storage:
As its hygroscopic, it is stored in well closed containers.

Potassium Chloride
Preparations:
Potassium chloride sustained release tablet:
Containing 600mg KCl equivalent to 8 mEq.
Strong potassium chloride solution:
Liquid in syrup/sorbitol base having 10 – 15% KCl.
Potassium Chloride Injection
1.5g/10ml, 3g/12.5ml, 6g/30ml of KCl in sterile water for injection
Used in Hypokalemia, digitalis intoxication, familial periodic paralysis, diuretic
therapy, hepatic cirrhosis with ascites, states of aldosterone excess with normal
renal function etc.
Ringer’s solution & Injection
Oral electrolyte powder and solution

Calcium Gluconate
Chemical Formula: (𝑪𝟏𝟐𝑯𝟐𝟐𝑶𝟏𝟒𝑪𝒂. 𝑯𝟐O)
Mol. Wt. 448.4
It is Calcium D-Gluconate monohydrate.
Preparation:
By boiling a solution of gluconic acid with excess of Calcium carbonate.
2𝐶𝐻2 𝑂𝐻 [ 𝐶𝐻𝑂𝐻 4𝐶𝑂𝑂𝐻 + 𝐶𝑎𝐶𝑂3 −−−−−→ 𝐶12𝐻22𝑂14𝐶𝑎. 𝐻2 O
Properties:
White crystalline powder. Odorless and tasteless. Freely soluble in boiling water,
sparingly soluble in water and insoluble in alcohol, ether and chloroform.
Uses:
In the deficiency of Calcium.

Oral Rehydration Therapy
In the case of acute diarrhea, along with water electrolytes like Cl- and Na+ are
actively secreted from the gut mucosa and there is a significant loss of these ions.
If an isosmolar solution of Glucose and Sodium Chloride is administered orally,
glucose and sodium are absorbed.
Along with sodium water absorption is also promoted.
This makes the physiological basis of Oral Rehydration Therapy.
Oral Rehydration Salts are composed of Anhydrous Glucose, Sodium Chloride,
Potassium Chloride and either Sodium bicarbonate or Sodium Citrate. The dry
preparation is mixed with specified amount of water. The solution so obtained is
used for oral rehydration therapy.

These Quantities are dissolved in 1 liter water.
Formula II and III are recommended by WHO and UNICEF to control diarrhea.
Oral Rehydration Salt (ORS)
Ingredients Formula I Formula II Formula III
Sodium Chloride 1.0 gm 3.5 gm 3.5 gm
Potassium Chloride 1.5 gm 1.5 gm 1.5 gm
Sodium bicarbonate 1.5 gm 2.5 gm -
Sodium citrate - - 2.9 gm
Anhydrous Glucose 36.4 gm 20.0 gm 20.0 gm

WHO has released new formula for ORS.
Oral Rehydration Salt (ORS)
Ingredients Quantities (g/l)
Sodium Chloride 2.6
Potassium Chloride 1.5
Trisodium citrate dihydrate 2.9
Anhydrous Glucose 36.4

Physiological Acid-Base Balance
Similar to electrolyte composition, all the body fluids have definite pH for their
optimum functioning and it must be maintained. Regulation of pH is essential for
different biochemical processes taking place in different cells and tissues.
Normal pH range of certain body fluids is as:
Body Fluids pH Range
Blood 7.4 – 7.5
Saliva 5.4 – 7.5
Urine 4.5 – 8.0
Gastric Juice 1.5 – 3.5
Duodenal fluid 5.5 – 7.5
Gall bladder bile 5.5 – 7.7
Pancreatic Juice 7.5 – 8.2
Semen 7.2 – 7.6

pH in individual organ is maintained by acid/alkali secretion to suit optimum
levels.
Acidic pH of gastric juice is maintained by secretion of Hydrochloric acid in
Stomach by parietal cells in response to chemical stimuli like histamine at H2
receptor, acetyl choline at M2 receptor etc.
This low pH is optimum for functioning of pepsin which is present in the gastric
juice.
pH of saliva is 5.4 – 7.5 which is suitable for optimum functioning of Ptyalin. The
action of ptyalin is inhibited at pH 1.5 in stomach.
The blood has pH range of 7.4 – 7.5. As blood is the major fluid in the body this is
the general pH which can be altered in an individual organ for optimum
functioning of the organ.

Different metabolic processes in body cells produce acidic products viz. carbonic
acid from CO2 and water; sulfuric acid and phosphoric acid from proteins and
phosphoproteins; lactic acid and pyruvic acid from anaerobic metabolism and
alkali viz. bicarbonate ions from organic acid salts like citrate lactate etc, which
tend to alter the pH of the tissue fluid and blood.
There are certain regulatory mechanisms which maintain the pH of the fluids to
optimum. These mechanisms are:
✓ Buffers of the body fluids
✓ Respiratory mechanisms
✓ Renal regulation

Buffers:
Chemicals that resist the change in pH.
Plasma contains MHCO3/H2CO3, M2HPO4 /MH2PO4, M-organic salt/organic acid
and M-proteins/proteins, where M = 𝑁𝑎+, 𝐾+, 𝐶𝑎+2 or 𝑀𝑔+2.
The ability of complex buffer systems present in the blood to bind with the H+
ions or neutralize acids is called “Alkali reserve” of the blood. In case pH of the
blood falls below 7.4, these reserve alkali react with the excess of acid/ H+ ions
and their amount decreases. Such a condition can lead to acidosis.
Likewise, when the pH raises above 7.5, the excess of alkali use the acid reserve,
and situation of alkalosis can take place.
Physiological buffer systems prohibit sudden change in pH in body fluids but in
order to function optimally it requires for some mechanisms by which some
amount of acids/bases can be made available. Lungs and kidneys provide for such.

Respiratory Mechanism :
When rate of respiration is slowed down, CO2 which is acidic, gets accumulated
inside the body and neutralizes the alkali reserve of the blood and causes acidosis.
When rate of respiration is higher, there is excessive excretion of CO2, which may
lead to alkalosis.
Thus acidity and CO2 concentration are both stimulant for respiratory mechanism
and can alter the rate as well as depth of respiration.
In the situation of acidosis, H2CO3 is converted into CO2 and water and the CO2 is
rapidly breathed out.
In case of alkalosis, both acidity and H2CO3 content is decreased. So, both
respiratory rate and depth are decreased leading to retention of CO2 and thus
increase in H2CO3 till the normal ratio of MHCO3/H2CO3 is reached.

Renal Mechanism:
Kidneys form ammonia which combines with acids produced by protein
metabolism and excrete it in urine.
pH of urine varies widely from 4.8 to 8.0. But in general it remains a bit acidic,
anyways varies with the nature of diet, exercise etc.
Fixed acids like phosphoric acid, sulphuric acid, hydrochloric acid etc are
removed through kidneys.
A 24 hours urine output of a normal individual contains equivalent of 20 – 40 ml
of 0.1N acid termed as titrable acidity of urine.

Disturbance in Acid-base balance:
Different physiological buffer systems, respiratory system and excretory system,
work together to maintain the acid base balance of the body.
Defect in elimination of CO2 or any metabolic disorder can alter the pH of the
blood and other body fluids beyond the physiological limits. Such conditions are
termed as physiological acid-base disturbance and are classified as:
Respiratory Acidosis
Respiratory Alkalosis
Metabolic Acidosis
Metabolic Alkalosis

Major intra and extracellular electrolytes

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