1. Water, sodium and potassium

2. Overview Introduction Distribution of body fluids Electrolytes
Major electrolyte imbalances

3. Introduction
To be in balance, the quantities of fluids and electrolytes leaving the body should be equal to the amounts taken in.
Electrolytes are molecules that release ions in water.
Anything that alters the concentrations of electrolytes will also alter the concentration of water, and vice versa.

4. Distribution of body fluids
Fluids occur in compartments (intracellular and extracellular compartments) in the body, and the movement of water and electrolytes between these compartments is regulated.
Fluid Compartments
The average adult female is 52% water by weight, while a male is 63% water, the difference due to the female's additional adipose tissue.

5. Electrolytes
Na+: most abundant electrolyte in the body.
K+ : essential for normal nerve impulse.
Cl-: Regulates osmotic pressure and assists in regulating acid base balance.
Ca2+: usually combined with phosphorus to form the mineral salts of bone and teeth, promotes nerve impulses, muscle contraction/relaxation.

6. Electrolytes
Mg +: Plays a role in carbohydrate and protein metabolism, storage and use of intracellular energy and neural transmission. Important in the functioning of the heart, nerves and muscle.

7. Electrolyte distribution

8. MAJOR ELECTROLYTE IMBALANCES
Hyponatremia (sodium deficit < 130mEq/L)
Hypernatremia (sodium excess >145mEq/L)
Hypokalemia (potassium deficit <3.5mEq/L)
Hyperkalemia (potassium excess >5.1mEq/L)

9. SODIUM/CHLORIDE IMBALANCES
Regulated by the kidneys
Influenced by the hormone aldosterone
Na is responsible for water retention and serum osmolality level
Chloride ion frequently appears with the sodium ion
Normal Na = mEq/L
Chloride mEq/L
Na and CL are concentrated in ECF

10. Osmolality
Is the osmotic pressure of blood. It measures the amount of solute concentration per unit of total volume of a particular solution. The normal values in serum are 280 to 295 mOsm/L.

11. Serum osmolality may be increased with:
Dehydration
Diabetes
Hyperglycemia
Hypernatremia
Ingestion of ethanol, methanol, or ethylene glycol
Kidney damage
Mannitol therapy
Shock

12. Serum osmolality may be decreased with:
excess hydration
Hypernatremia
Inappropriate ADH Secretion

13. Hyponatremia Excessive sodium loss or H2O gain
A normal sodium level is between 135 and 145 (mEq/L).
Hyponatremia occurs when the sodium in your blood falls below 135 mEq/L.

14. Causes of Hyponatremia
Prolonged diuretic therapy
Excessive diaphoresis
Insufficient Na intake
GI losses – suctioning, laxatives, vomiting
Administration of hypotonic fluids
Compulsive water drinking
Labor induction with oxytocin
Cystic fibrosis
alcoholism

15. Clinical manifestations
Headache
Faintness
Confusion
Muscle cramping/twitching
Increased weight
Convulsions

16. Types of hyponatremia

The imbalance between sodium and water in your blood may occur in three primary ways:
In hypervolemic hyponatremia, your body has too much water and sodium but the water gain is greater. Hypervolemic hyponatremia is commonly the result of kidney failure, heart failure or liver failure.
In euvolemic hyponatremia, your water level is too high. This condition is commonly due to chronic health conditions, cancer or certain medications.
In hypovolemic hyponatremia, you have too little water and sodium but the sodium loss is greater. This may occur, for example, when exercising in the heat without replenishing your fluid electrolytes or with marked blood loss.

20. Test yourself Osmolality 260 mmol/L (280 -296 mmol/L)
A 63-year-old man had a persistent chest infection, for the previous 2 months. There were no signs of dehydration or oedema. Examination of blood yielded the following results:
What is the most likely cause of low sodium and osmolality?
Na mmol/L ( mmol/L)
Osmolality 260 mmol/L ( mmol/L)
Urine Na+ 74 mmol/L
Urine osmolality 625 mmol/kg

21. Test yourself
_____is the most common extracellular cation, while _____ is the most abundant intracellular cation.
Sodium; Ca++
K+; Na+
Sodium; potassium
K+; Ca++

22. Test yourself When serum sodium is low , it means
Total body sodium is low
Total body sodium is high
Total body sodium is normal
Any of the above

23. Test yourself
The imbalance known as ____________ can be caused by certain diuretic medications.
Hyponatremia
Hyperatremia
Hypokalemia
hyperkalemia

24. Test yourself
Serum sodium is 130 with serum osmolality of 300 mOsm/kg. Most likely it is
inappropriate ADH secretion
Diabetic ketoacidosis
Uremia
Ethanol intoxication

25. Hypernatremia
Occurs with excess loss of H2O or excessive retention of Na
Can lead to death if not treated

26. Causes of Hypernatremia
Vomiting/diarrhea
Diaphoresis
Inadequate ADH
Some drugs
Hypertonic fluids/tube feedings
Major burns

29. Types of Hypernatremia

30. Hypokalemia
Hypokalemia is defined as potassium level less than 3.5 mEq/L
Moderate hypokalemia is a serum level of mEq/L.
Severe hypokalemia is defined as a level less than 2.5 mEq/L.

31. What causes hypokalemia?
GI losses (vomiting and diarrhea)
Renal losses
Drugs (diuretics and corticosteroids)
Alkalosis

32. Hyperkalemia
Is the commonest and most serious electrolyte emergency encountered in clinical practice.

33. Causes Renal failure Mineralocorticoid deficiency Acidosis
Potassium release from damaged cells

34. Match column A with the correct answer from B
Cl-
Most abundant negative electrolyte in intracellular fluid
Na+
Most abundant positive electrolyte in intracellular fluid K+
Least abundant positive electrolyte in extracellular fluid
Mg++
Most abundant positive electrolyte in extracellular fluid
HPO4--
Most abundant negative electrolyte in extracellular fluid

35. Hyperkalemia is defined as
a) reduction of plasma calcium level.
b) increase in plasma potassium level.
c) increase in plasma sodium level.
d) decrease in plasma potassium level

36. Test Yourself
A 55 year old man, was trapped for 7 hours in railway accident. He sustained severe multiple injuries. The following biochemical results were obtained on admission:
Na+ = 141 mmo/l
K+ = 8.1 mmo/l
What is the diagnosis?

37. References
Marshall, W. and Bangert, S. (2008). Clinical chemistry (6th ed.). Edinburgh, London: Mosby Elsevier. ISBN (chapter 2)
Gaw, A. et al. (2004). Clinical Biochemistry (3rd ed.)
Beckett, G. et al. (2008). Clinical Biochemistry (8th ed.)
Bishop., et al. (2000). Clinical Chemistry (4th ed.)