Name the colligative properties of biological fluids
Colligative properties of Serum
- Osmotic pressure: 6.5 atm (0°C), 7.6 atm (37°C)
- Freezing point depression ΔTf: 0.52°C decreasing (below 0°C)
Water and electrolytes balance - Normally plasma contains
- (compare to the value from 0.9% NaCl)
- Electrolytes: ~155 mEq/L of cations and 155 mEq/L of anions.
- Osmolarity (serum) ~ 300 ± 10 mOsmol/L
Physiologic effects associated with increases in osmolility
Serum Osmolality(mOsmol/kg) Physiologic Changes
330 Fainting, central nervous system changes
320 Weakness
300 ± 10 Normal
250 Weakness
233 Seizures, coma
What are isotonic solutions?
- Isotonic solutions produce no discomfort when instilled in the eye, nasal tract, blood, or other body tissues
- Isotonic solutions cause no swelling or contraction of the tissues with which they come in contact
- Physically and biologically: Isotonic solutions have the same osmotic pressure as that of the body fluids, with respect to a certain bio-membrane
Describe an isotonic solution
Same # of impermeable solute particels per liter
Water in = water out
Usually freezing point equal -0.52C
What is a hypertonic solution?
- Higher total impermeable solute particle concentration than cellular contents
- Freezing point lower than - 0.52 C
- Water flow out of cell, cause crenation (cell shrinkage)
What is a hyptonic solution?
- Lower concentration of impermeable solute particle than cellular contents
- Usually, freezing point higher than - 0.52 C (- 0.52 ~ 0 C )
- Water flow into cell, hemolysis (cell swelling and bursting)
Does isomotic and isotonic equal?
- Usually but not always equal
Osmotic pressure is related to an ideal semi-permeable membrane which only allow water to pass through
Isotonicity is related to the cell membrane permeability.
- Cell membrane may allow certain molecules to pass through, in addition to water
- If a solute can also diffuse freely across the cell membrane, it does not exert (contribute) tonicity properties with the membrane.
- e.g. NH4Cl , urea, alcohol, glycerin, and boric acid can cross the blood cell membrane, and should not be counted for isotonicity
Isosmotic with blood, freezing point -0.52 C
Hyptonic with blood –> boric acid can pass through the erythrocyte freely and cause rapid hemolysis
Isotonic with lacrimal fluid –>Boric acid cannot past through eye mucous lining
What are the two methods to adjust tonicity?
Class I method
- Cryoscopic method (Freezing point depression)
- Sodium chloride equivalent method (E value)
Class II method
- White- Vincent method
- Sprowls method
What is the cyroscopic method?
It is the freezing point depression method see sheet and power point for equation
Describe the sodium chloride equivalent method (E value)
Sodium chloride equivalent value (E) by Mellen and Seltzer 1936 – “Tonicic equivalent”
The NaCl equivalent (E value) of a drug is the amount of NaCl that has the same tonicity effect as 1 g of the drug.
“WNaCl” = E Wdrug
E = “WNaCl” / Wdrug
E, Liso, Tf 1% Values were determined experimentally and are available for calculation
What is the E value?
See equation
How to calculate using E values
- Amount of NaCl equivalent to the amount of drug in solution
“WNaCl” = E x Wdrug
“WNaCl” = E · (amount of drug in solution) = X g
2.If the drug were not added, how much NaCl would be needed to make V(ml) of isotonic solution?
WNaCl = (0.9g /100ml) · V = Y g
V: Volume of solution in ml
- How much NaCl is needed to render the solution isotonic :
WNaCl = WNaCl – “WNaCl” = Y – X
What are tonicity agents?
NaCl, NaNO3
Ringer’s solution (NaCl, KCl, CaCl2)
Dextrose
Mannitol
Propylene glycol
Glycerin
Drug!
All solutes that are impermeable
What is the white-vincent method?
V = W E 111.1 ml
V: the volume (ml) of isotonic solution can be prepared by dissolving only the drug in pure water
W: Weight (gram) of the solute
E: sodium chloride equivalent value of the solute
What is 111.1? ….
What is a multi-component solution?
To prepare multi-component solution
V = [ (Wi Ei)] 111.1
What is the Sprowl’s method and prowl’s value?
Sprowl’s value—the volume of an isotonic solution that can be prepared by the addition of water to 0.3g of drug
When W = 0.3 g,
Sprowl’s value = V
= W E 111.1 ml
= 0.3 E 111.1 ml
SUMMARY
ISOTONIC SOLUTIONS: definitions, properties and exceptions
METHODS OF ADJUSTING TONICITY
Class I method
Cryoscopic method (Freezing point depression)
Sodium chloride equivalent method
Class II method
White-Vincent method
Sprowls value
Other calculations
E from Liso
E from Sprowls value
