Electrolyte Solution

Electrolyte Solution
- Meq
-Mmoles/L
-Osmol

1. Milliequivalents
Millimolesand Micromoles
Osmolarity
Water and Electrolyte Balance
ELECTROLYTE SOLUTIONS

2. Preface
The molecules of chemical compounds in solution:
may remain intact “nonelectrolytes”,
E.g. Urea and dextrose in body water.
or may dissociate into particles known as ions, which carry an electric
charge“electrolytes”.
E.g. sodium chloride in body fluids.
Sodium chloride in solution provides Na
+
and Cl
-
ions, which
carry electric charges.
Ifelectrodes carrying a weak current are placed in the solution, the
ions move in a direction opposite to the charges.
Na
+
ions move to the negative electrode (cathode) and are called cations.
Cl
-
ions move to the positive electrode (anode) and are called anions.

3. Preface
Electrolyte ions in the blood plasma include:
the cationsNa
+
, K
+
, Ca
++
, and Mg
++
.
& the anions Cl
-
, HCO3
-
, HPO4
--
, SO4
--
, organic acids
-
, and
proteins
-
.
Electrolytes in body fluids play an important role in:
maintaining the acid-base balance in the body.
controlling body water volumes.
regulating body metabolism.

4. Applicable Dosage Forms
Electrolyte preparations are used in the treatment of
disturbances of the electrolyte and fluid balance in the body.
In clinical practice, they are provided in the form of:
oral solutions and syrups,
dry granules intended to be dissolved in water or juice to make
an oral solution,
oral tablets and capsules,
intravenous infusions.

5. Milliequivalents
A chemical unit, the milliequivalent(mEq), used to express the
concentration of electrolytes in solution.
It is a unit of measurement of the amount of chemical activity of an
electrolyte.
Under normal conditions, blood plasma contains 154 mEqof cations
and an equal number of anions.
The total concentration of cationsalways equals the total concentration
of anions.
However, it should be understood that normal laboratory values of
electrolytes vary, albeit within a rather narrow range.

8. Milliequivalents
The concentration of electrolytes in intravenous infusion fluids is
most often stated in mEq/L.
In the International System (SI), molar concentrations [as
millimolesper liter (mmol/L) and micromoles per liter
(µmol/L)] are used to express most clinical laboratory values,
including those of electrolytes.
1 mEqis represented by 1 mg of hydrogen, 23 mg of sodium, 35.5
mg of chlorine, 39 mg of potassium, 20 mg of calcium, and so
forth.
How?

10. Example Calculations of
Milliequivalents
1-What is the concentration, in milligrams per milliliter, of a
solution containing 2 mEqof potassium chloride (KCl) per
milliliter?
2-What is the concentration, in grams per milliliter, of a solution
containing 4 mEqof calcium chloride (CaCl
2⋅2H
2O) per milliliter?
3-What is the percent (w/v) concentration of a solution containing
100 mEqof ammonium chloride per liter?

11. Example Calculations of
Milliequivalents
4-A solution contains 10 mg/100 mL of K
+
ions. Express this
concentration in terms of milliequivalentsper liter.
5-A solution contains 10 mg/100 mL of Ca
++
ions. Express this
concentration in terms of milliequivalentsper liter.
6-A magnesium (Mg
++
) level in blood plasma is determined to be
2.5 mEq/L. Express this concentration in terms of milligrams.

12. Example Calculations of
Milliequivalents
7-How many milliequivalentsof potassium chloride are represented
in a 15-mL dose of a 10% (w/v) potassium chloride elixir?
8-How many milliequivalentsof magnesium sulfate are represented
in 1 g of anhydrous magnesium sulfate (MgSO
4)?
9-How many milliequivalentsof Na
+
would be contained in a 30-
mL dose of the following solution?
Disodium hydrogen phosphate “Na
2HPO
4.7H
2O” 18 g
Sodium biphosphate“NaH
2PO
4.H
2O” 48 g
Purified water ad 100 mL

13. Example Calculations of
Milliequivalents
10-A person is to receive 2 mEqof sodium chloride per kilogram of
body weight. If the person weighs 132 lb., how many milliliters of a
0.9% sterile solution of sodium chloride should be administered?

14. Example Calculations of
Milliequivalents/Parenteral Nutrition

15. Example Calculations of
Milliequivalents/Parenteral Nutrition
The formula for a TPN solution calls for the addition of 2.7 mEqof
Ca
++
and 20 mEqof K
+
per liter. How many milliliters of an
injection containing 20 mg of calcium chloride (CaCl
2.2H
2O) per
milliliter and how many milliliters of a 15% (w/v) potassium
chloride injection should be used to provide the desired additives?

16. Example Calculations of
Milliequivalents/Parenteral Nutrition
A potassium phosphate injection contains a mixture of 224 mg of
monobasic potassium phosphate (KH
2PO
4) and 236 mg of dibasic
potassium phosphate (K
2HPO
4) per milliliter. If 10 mL of the
injection are added to 500 mL of D5W (5% dextrose in water for
injection):
(a) how many milliequivalentsof K
+
,and
(b) how many millimolesof total phosphate are represented in the
prepared solution?

17. Millimolesand Micromoles
The SI expresses electrolyte concentrations in millimolesper
liter (mmol/L) in representing the combining power of a
chemical species.
For monovalent species, the numeric values of the
milliequivalentand millimoleare identical.
A mole is the molecular weight of a substance in grams.
A millimoleis one thousandth of a mole, and a micromole is
one millionth of a mole.

18. Example Calculations of Millimolesand
Micromoles
1-How many millimolesof monobasic sodium phosphate
NaH
2PO
4.H
2O (m.w. 138) are present in 100 g of the substance?
2-How many milligrams would 1 mmolof monobasic sodium
phosphate weigh?
3-What is the weight, in milligrams, of 1 mmolof HPO4
--
?
4-Convert blood plasma levels of 0.5 µg/mL and 2 µg/mL of
Tobramycin (m.w. 467.52) to µmol/L.

19. Osmolarity
Osmotic pressure is important to biologic processes that
involve the diffusion of solutes or the transfer of fluids
through semipermeable membranes.
The United States Pharmacopeiastates that knowledge of the
osmolarconcentrations of parenteral fluids is important.
This information indicates to the practitioner whether the
solution is hypoosmotic, iso-osmotic, or hyperosmotic with
regard to biologic fluids and membranes.

20. Osmolarity
Osmotic pressure is proportional to the total number of particles in solution.
The unit used to measure osmotic concentration is the milliosmole(mOsmol).
For dextrose, a nonelectrolyte, 1 mmol(1 formula weight in milligrams)
represents 1 mOsmol.
This relationship is not the same with electrolytes, however, because the total
number of particles in solution depends on the degree of dissociation of the
substance in question.
Assuming complete dissociation, 1 mmolof NaClrepresents 2 mOsmol(Na
+
+
Cl
-
) of total particles, 1 mmolof CaCl
2represents 3 mOsmol(Ca
++
+ 2Cl
-
) of
total particles, and 1 mmolof sodium citrate (Na
3C
6H
5O
7) represents 4 mOsmol
(3Na
+
+ C
6H
5O
7
–3
) of total particles.

21. Osmolarity
According to the United States Pharmacopeia, the idealosmolar
concentration may be calculated according to the equation:
In practice, as the concentration of the solute increases,
physicochemical interaction among solute particles increases, and
actualosmolarvalues decrease when compared to ideal values.
Deviation from ideal conditions is usually slight in solution within
the physiologic range and for more dilute solutions, but for highly
concentrated solutions, the actual osmolaritiesmay be appreciably
lower than ideal values.

22. Osmolarity
For example, the ideal osmolarityof 0.9% sodium chloride
injection is:
Because of bonding forces, however, n is slightly less than 2 for
solutions of sodium chloride at this concentration, and the actual
measured osmolarityof the solution is about 286 mOsmol/L.
Some pharmaceutical manufacturers label electrolyte solutions
with ideal or stoichiometric osmolaritiescalculated by the
equation just provided, whereas others list experimental or actual
osmolarities.

23. Osmolarity/Osmolality
A distinction should be made between the terms osmolarity
and osmolality.
osmolarityis the milliosmolesof solute per liter of solution,
osmolality is the milliosmolesof solute per kilogram of solvent.
For dilute aqueous solutions, osmolarityand osmolality are
nearly identical.
For more concentrated solutions, however, the two values
may be quite dissimilar.

24. Osmolarity/Osmolality
Normal serum osmolality is considered to be within the
range of 275 to 300 mOsmol/kg.
Osmometersare commercially available for use in the
laboratory to measure osmolality.
Abnormal blood osmolality that deviates from the normal
range can occur in association with:
shock, trauma, burns, water intoxication (overload), electrolyte
imbalance, hyperglycemia, or renal failure.

26. Example Calculations of Milliosmoles
1-A solution contains 5% of anhydrous dextrose C
6H
12O
6in water for
injection. How many milliosmolesper liter are represented by this
concentration?
2-A solution contains 156 mg of K
+
ions per 100 mL.How many
milliosmolesare represented in a liter of the solution?
3-A solution contains 10 mg% of Ca
++
ions. How many milliosmolesare
represented in 1 liter of the solution?
4-How many milliosmolesare represented in a liter of a 0.9% sodium
chloride solution?

27. Clinical Considerations of Water and
Electrolyte Balance
Maintaining body water and electrolyte balance is an essential
component of good health.
Waterprovides the environment in which cells live and is the
primary medium for the ingestion of nutrients and the excretion
of metabolic waste products.
Normally, the osmolality of body fluid is maintained within
narrow limits through:
dietary input,
regulatory endocrine processes,
balanced output via the kidneys, lungs, skin, and the gastrointestinal
system.

28. Clinical Considerations of Water and
Electrolyte Balance
In clinical practice, fluid and electrolyte therapy is undertaken
either to:
provide maintenance requirements,
replace serious losses or deficits.
Body losses of water and/or electrolytes can result from a number
of causes, including:
vomiting, diarrhea, profuse sweating, fever, chronic renal failure,
diuretic therapy, surgery, and others.
The type of therapy undertaken (i.e., oral or parenteral) and the
content of the fluid administered depend on a patient’s specific
requirements.

29. Clinical Considerations of Water and
Electrolyte Balance
Examples:
Apatient taking potassium wasting diuretics may simply require a
daily oral potassium supplement along with adequate intake of water.
An athlete may require rehydration with or without added
electrolytes.
Hospitalized patients commonly receive parenteral maintenance
therapy of fluids and electrolytes to support ordinary metabolic
function.
In severe cases of deficit, a patient may require the prompt and
substantial intravenous replacement of fluids and electrolytes to
restore acute volume losses resulting from surgery, trauma, burns, or
shock.

30. Clinical Considerations of Water and
Electrolyte Balance
Total body water in adult males normally ranges between
55% and 65% of body weight depending on the proportion
of body fat.
The greater the proportion of fat, the lesser the proportion of
water.
Values for adult women are about 10% less than those for
men.
Newborn infants have approximately 75% body water, which
decreases with growth and increases in body fat.

31. Clinical Considerations of Water and
Electrolyte Balance
Of the adult body’s water content, up to two thirds is
intracellular and one third is extracellular.
The proportion of extracellular body water, as a fraction of
total body weight, decreases in infants in the first year from
approximately 45% to 30% while the intracellular portion
increases.
For an adult, approximately 2500 mL of daily water intake
(from ingested liquids and foods and from oxidative
metabolism) are needed to balance the daily water output.

32. Clinical Considerations of Water and
Electrolyte Balance
In general terms, 1500 mL of water per square meter of
body surface area may be used to calculate the daily
requirement for adults.
On a weight basis, estimates of 32 mL/kg for adults and 100
to 150 mL/kg for infants have been cited as average daily
requirements of water intake for healthy individuals.
These estimated requirements differ greatly in persons with
clinical disorders affecting water and electrolyte homeostasis
and in conditions of acute deficit.

33. Clinical Considerations of Water and
Electrolyte Balance
The composition of body fluids generally is described with regard
to body compartments:
intracellular (within cells),
intravascular (blood plasma),
interstitial (between cells in the tissue).
Intravascular and interstitial fluids commonly are grouped
together and termed extracellular fluid.
Although all electrolytes and nonelectrolytes in body fluids
contribute to osmotic activity:
sodium and chloride exert the principal effect in extracellular fluid,
potassium and phosphate predominate in intracellular fluid.

34. Clinical Considerations of Water and
Electrolyte Balance
Since cell membranes generally are freely permeable to
water, the osmolality of the extracellular fluid (about 290
mOsm/kg water) is about equal to that of the intracellular
fluid.
Therefore, the plasma osmolality is a convenient and accurate
guide to intracellular osmolality, and may be approximated
by the formula:
where: sodium (Na) and potassium (K) are in mEq/L, and
blood urea nitrogen (BUN) and glucose concentrations are in
mg/100 mL (mg/dL).

35. Example Calculations of Water
Requirements and Electrolytes in Parenteral
Fluids
1-Calculate the estimated daily water requirement for a healthy
adult with a body surface area of 1.8 m
2
.
2-Estimate the plasma osmolality from the following data: sodium,
135 mEq/L; potassium, 4.5 mEq/L; blood urea nitrogen, 14 mg/dL;
and glucose, 90 mg/dL.
3-

36. Example Calculations of Water
Requirements and Electrolytes in
Parenteral Fluids