Body electrolytes

1. BODY fluids and ELECTROLYTES
By D.R Siwale (MSc,Human Physiology, BSc.Biological
sciences, BSc Human Biology, Bip.Edu)

2. Normal Body water and electolyte levels
• Introduction
• Cells exist in an “internal sea” of the
Extracellular fluid (ECF) enclosed with the
integument of the animal.
• From ECF the cells takes up O2 and Nutrients
and discharges metabolic wastes products.
• The ECF is divided into interstitial fluid, Blood
plasma and Lymph
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3. Cont’d….
• Terminologies
• ECF: It is body fluid outside the cells. It is the internal
environment of all multicellular animals
• ICF: The cytosol, also known
as intracellular fluid (ICF) or cytoplasmic matrix, is
the liquid found inside cells. It is separated into
compartments by membranes
• IF: (Interstitial Fluid)The fluid which is neither Plasma
nor ICF. i.e fluid found in the intercellular spaces
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4. • Plasma: is a yellowish liquid component of blood
that normally holds the blood cells in whole
blood in suspension. In other words, it is the liquid
part of the blood that carries cells and proteins
throughout the body. It makes up about 55% of the
body's total blood volume
• Lymph: is the fluid that flows through vessels and
nodes of the lymphatic system. It is formed when the
interstitial fluid is collected through lymph capillaries
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5. Cont’d….
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6. Cont’d…
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7. • ECF volume and osmolality regulation is
controlled by three hormones. Aldosterone,
ADH, atrial natriuretic hormone.
• Whats the function of these three hormones?

8. Electrolytes and Acid/base
• Water is an excellent biological fluid that serves
as a solvent.
• Electrolytes (e.g NaCl) are molecules that
dissociate in water to their cation (Na+) and anion
(Cl-) equivalents. Physiologically important
electrolytes are Na+, K+, Ca2+, Mg 2+, Cl- and HCO3
-
• Electrolytes and other charged compounds (e.
Proteins) are Unevenly distributed in the body
fluids. This separation plays an important role in
physiology
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9. Cont’d…
• Solutes are broadly classified into;
• Electrolytes are inorganic salts, all acids and
bases, and some proteins
• Nonelectrolytes – examples include glucose,
lipids, creatinine, and urea
• Electrolytes have greater osmotic power than
nonelectrolytes.
• Water moves according to osmotic gradients
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10. Importance of some electolytes
(a)Sodium ions; is a mineral that's essential for life. It's regulated in the body by your kidneys, and it
helps control your body's fluid balance. It also helps send nerve impulses and affects muscle
function. ... Having less sodium in your diet may help you lower or avoid high blood pressure
(b)Potassium ions; is one of the most important minerals in the body. It helps regulate fluid balance,
muscle contractions and nerve signals. What's more, a high-potassiumdiet may help reduce blood
pressure and water retention, protect against stroke and prevent osteoporosis and kidney stones
(c) Calcium ions; But calcium is actually responsible for a lot of things in your body. Proper amounts
of calcium help keep your joints free of inflammation and arthritis, as well as help your muscles
contract
(d)Magnesium ions; is needed for more than 300 biochemical reactions in the body. It helps to maintain
normal nerve and muscle function, supports a healthy immune system, keeps the heart beat steady,
and helps bones remain strong. It also helps regulate blood glucose levels and aid in the production
of energy and protein
(e)Chloride ions; It helps keep the amount of fluid inside and outside of your cells in balance. It also
helps maintain proper blood volume, blood pressure, and pH of your body fluids. Tests for sodium,
potassium, and bicarbonate are usually done at the same time as a blood test for chloride
(f) Bicarbonate ions; The primary role of the bicarbonate ion in the blood system is to transport waste
carbon dioxide from the various body tissues to the lungs, where it can be expelled

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12. Water loss (Volume loss)
• It is decrease in the whole body fluid volume which
includes both ECF and ICF.
• It is usually ECF loss which is more important and
assessed.
• Water loss can be of two types;
• (1) isotonic volume depletion with both salt and
water loss leading into hypovolaemia,
• (2) only water loss with only minimal loss of
electrolytes leading into dehydration.

13. • Causes and Features
• (1) Isotonic volume depletion occurs due to
diarrhoea, vomiting, and excess diuresis. Here
normal or decreased sodium is observed.
• Fluid loss is only of ECF and so early intravascular
volume reduction occurs. This causes
hypotension and decreased tissue perfusion.
• Hypovolaemia can be mild (< 2l fluid loss);
moderate (2–3 L fluid loss); severe (>3 L fluid
loss).

14. • Features of isotonic volume depletion
• Dry tongue
• Rapid pulse
• Cold clammy extremities
• Sunken eyes
• Hypotension
• Oliguria
• Raised blood urea
• Decreased urinary sodium.

15. • (2) Only pure water loss occurs due to poor
fluid intake and diabetes insipidus. It causes
dehydration with proportionate decrease in
total body water (2/3rd ICF, 1/3rd ECF). As ECF
including intravascular fluid loss is less,
hypotension is less.

16. • Features of only pure water loss are;
• Severe thirst
• Confusion and convulsions due to hypernatraemia
• blood pressure is relatively normal. Dehydration can
be mild (weight loss 5%); moderate (10%); severe
(15%).

17. • Management of water Loss
• Evaluation is done by doing serum sodium,
urinary sodium, and blood urea.
• Isotonic volume depletion is corrected by
0.9% normal saline.
• Pure water depletion is corrected by more
water intake/ intravenous 5% dextrose.
• Monitoring fluid therapy by skin and tongue
examination, weight gain, pulse, blood
pressure, CVP, PCWP.

18. Water excess (ECF volume excess)
• It can be divided into water and salt excess or
predominantly water excess called as water
intoxication.
• Water and salt excess occurs in CCF, cirrhosis,
nephrotic syndrome, hypoproteinaemia, renal failure,
excessive saline infusion.
• Water intoxication occurs in TURP, excess infusion of
5% dextrose only, SIADH secretion, psychogenic
polydypsia.
• It is managed by stopping fluid infusion or procedure
(TURP); fluid restriction, and treating the cause.

19. • Causes of Water excess
• Excessive amount of intravenous dextrose (5%).
• During colorectal bowel wash for preparation of large bowel
for surgery, if water is used instead of saline, especially in
children.
• In TURP (Transurethral resection of prostate) when excess
irrigating fluid water or glycine is used (commonly used).
• In syndrome of inappropriate antidiuretic hormone (SIADH)
which is commonly associated with lobar pneumonia,
empyema, oat cell carcinoma and head injury.

20. Clinical features
• Drowsiness, weakness
• Convulsions and coma
• Nausea, vomiting
• Passage of dilute urine
• Distended neck veins
• Pedal oedema
• Gain in body weight—most sensitive and consistent sign
• Circulatory overload—tachycardia, pulmonary oedema,
hypertension
• Bilateral basal crepitations, ascites
• Raised CVP, PCWP

21. • Investigations of Excess water loss
• Haematocrit and sodium level (will show fall in level).
• Low potassium. Low blood urea.
• Treatment
• Water and salt restriction and observation.
• Monitoring in ICU.
• Management of fluid and electrolyte balance.
• Infusion of hypotonic sodium chloride.
• Administration of diuretics and hypertonic saline
should be avoided, as it may cause rapid changes in
serum sodium and water level which will lead to
neuronal demyelination and fatal outcome.

22. ECF LOSS
• Here only ECF loss is present with normal ICF.
• It is seen in vomiting, diarrhoea, intestinal obstruction.
• Treatment is infusion of normal saline.
ECF EXCESS
• Only ECF excess without an ICF excess.
• Excessive infusion of saline with impaired excretion.
• Raised JVP (earliest and best clinical sign), cardiac
failure and peripheral oedema.
• Treatment is fluid restriction and diuretics like
frusemide.

23. Hypernatremia
• Serum sodium level > 150 mEq/L. Excess infusion
of normal saline causes overload in circulating
salt and water. It is usually due to water deficit.
• Causes
• Renal dysfunction.
• Cardiac failure.
• Drug induced like NSAID, corticosteroids.
• It may be either primary sodium excess or
primary potassium excess or primary water
deficit.

24. • Types of Hypernatraemia
• Euvolemic (pure water loss): It is due to failure of water
intake like in comatous patients, bedridden people,
postoperative patients and in patients with high fever
leading into extrarenal loss of water. It can occur in
diabetes insipidus or chronic renal failure as renal loss of
water.
• Hypovolaemic (among loss of water and sodium, more
water is lost than sodium): It is due to vomiting, diarrhoea,
more undue sweating (extrarenal); osmotic diuresis by
glucose/mannitol (renal).
• Hypervolaemic (both sodium and water gain but sodium
gain is more than water gain) as seen in more salt intake,
excess steroids, sodium bicarbonate/hypertonic saline
infusion (salt gain).

25. • Clinical Features of hypernatremia
• Pitting oedema.
• Puffiness of face.
• Increased urination.
• Often dilated jugular veins.
• Features of pulmonary oedema.

26. • Investigation
• Serum electrolytes, plasma and urine osmolality, renal
function tests, haematocrit.
• Management
• Restriction of saline and sodium. Treatment of
pulmonary oedema.
• Hypernatraemia should be corrected slowly as follows:
• Initial infusion of normal saline, then infusion of half
strength saline (0.45%) and later with 5% dextrose, i.e.
gradual controlled correction is done.
• Otherwise cerebral oedema and hyperglycaemia can
develop.
• Oral and nasogastric administration of water/fluids.

27. HYPOKALEMIA
• Sudden Hypokalaemia
• Serum potassium level less than 3.5 mEq/l. It occurs
in patients in diabetic coma treated by insulin and
saline infusion.

28. • Gradual Hypokalaemia
• Causes
• Diarrhoea of any causes, villous tumour of the rectum,
ulcerative colitis.
• After trauma or surgery.
• Pyloric stenosis with gastric outlet obstruction.
• Duodenal fistula, ileostomy.
• After ureterosigmoidostomy.
• Insulin therapy.
• Poisoning.
• Drugs like beta agonists.
• Familial periodic paralysis.

29. • Clinical Features
• Slurred speech
• Muscular hypotonia—physical sign.
• Depressed reflexes.
• Paralytic ileus
• Weakness of respiratory muscles.
• Cardiac arrhythmias.
• Inability to produce concentrated urine and so causes
• Nocturia and polyuria.
• ECG shows prolonged QT interval, depression of the ST
segment and inversion of T wave, prominent U wave.
• Often hypokalaemia is associated with alkalosis. Serum
potassium will be decreased.

30. • Treatment
• Oral potassium 2 g 6th hourly, 15 ml potassium chloride syrup
(20 mmol of K).
• IV KCl 40 mmol/litre given in 5% dextrose or normal saline
slowly, often under ECG monitoring [Total dose is 40 mmol
(0.2 mmol /kg/hour). Maximum dose per hour is 20 mmol].
• Hypokalaemic alkalosis which occurs in pyloric stenosis should
be treated carefully by IV potassium as there will be severe
potassium loss.

31. ACID-BASE BALANCE
• Normal pH (– log 10 of H+) is 7.36–7.44.
• ™
. Buffer system
• –– Bicarbonate buffer
• –– Protein buffer
• –– Phosphate buffer
• ™
. Renal control of pH
• ™
. Respiratory control of pH

32. • Note:
• When H+ increases pH decreases.
• An acid is a substance that dissociates water to release hydrogen ion.
• A base is a substance that takes hydrogen ion. A buffer is a combination of
weak acid and conjugate base. These buffers maintain the H+
concentration in blood within fine limits.
• Natural buffers are extracellular or intracellular. Bicarbonate/carbonic acid
buffer, phosphate buffer and plasma proteins are extracellular natural
buffers.
• Haemoglobin and other proteins are intracellular buffers. Bicarbonate/
carbonic acid buffer is most important as carbonic acid levels are
regulated by lungs which eliminates excess of it as CO2.
• Bicarbonate part is separately controlled by kidney.
• Acidosis is pH of blood less than 7.35. Alkalosis is pH more than 7.45.

33. v
• Henderson Equation (Used to Assess
Hydrogen Ion Concentration)

34. • Here constant K is 800 (for H2CO3 / HCO3–
buffer).
• Carbonic acid (H2CO3) is solubility coefficient
of CO2 in blood (α) multiplied by partial
pressure of CO2 (PCO2). α is 0.03
ml/mmHg/100 ml of blood; PCO2 is 40 mmHg.
• H2CO3 = αPCO2 = 0.03 × 40 = 1.2 ml. Normal
blood bicarbonate/HCO3 level is 24 mmol/L.
• so H+ is 800 × 1.2 divided by 24 = 40 mmol/L.

35. • Henderson-Hasselbalch Equation
• (Used to Assess pH)
• It is used to find out pH of the blood using logarithm. Negative
• logarithm of constant K (800 for carbonic buffer) is called as
• pKa. It is 6.1 for H2CO3/HCO3
• – buffer system.

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37. question on pH
• Two men, Subject A and Subject B, have
disorders that cause excessive acid production
in the body.
• The laboratory reports the acidity of Subject
A’s blood in terms of [H+] and the acidity of
Subject B’s blood in terms of pH.
• Subject A has an arterial [H+] of 65 × 10−9
Eq/L, and Subject B has an arterial pH of 7.3.
• Which subject has the higher concentration
of H+ in his blood?

38. • ANSWER

39. Major buffers in the body
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40. •….END….