Osmolarity And Tonicity Flashcards
What are the types of solutions?
Isotonic- no volume change
Donate water to cell- hypotonic
Sequester water from cell- hypertonic
What are the rules for normal functioning cells?
- All hypo-osmotic solutions are hypotonic
- ISO-osmotic solutions can be hypo or isotonic
- Hyper-osmotic solutions can be hypo-, iso-, or hypertonic depending on the ratio of non-penetrating solutes between the 2 compartments
These are needed to determine the best intra a round fluid to be used
Give a list of intravaneous fluid
5% dextrose in water- isotonic, but physiologically hypotonic
10% dextrose in water- hypertonic
- 45% saline- hypotonic
- 9% saline -isotonic
- 0% saline- hypertonic
5% dextrose in 0.225% saline- isotonic
5% dextrose in 0.45% saline-hypertonic
5% dextrose in 0.9% saline-hypertonic
Ringers solution- isotonic
What are the indications and considerations for 5% dextrose in water?
Provides free water necessary for renal excretion of solutes, used to replace water losses and treat hypernatremia, provides 170 calories/L. No electrolytes
What are the indications and considerations for 10% dextrose in water?
Provides free water only, no electrolytes, provides 340 calories/L
What are the indications and considerations for 0.45%saline?
Provides free water in addition to Na+ and Cl-. Used to replace hypotonic fluid losses. Used as maintenance solution. Provides no calories
What are the considerations and indications of 0.9% saline?
Used to expand intra vascular volume and replace extracellular fluid losses. Only solution that may be administered with blood products. Contains Na+m and Cl- in excess plasma levels. Does not provide free water, calories, or others electrolytes. May cause intravacular overload or hypercholermic acidosis
What are the considerations and indications of 3.0% saline?
Used to treat symptomatic hyponatremia, must be administered slowly with extreme caution because it may cause dangerous intravascular fluid overload and pulmonary edema
What are the considerations and indications of 5% dextrose in 0.225%saline?
Provodes Na+, Cl- and free water. Used to replace hypotonic losses and treat hypernatremia, provides 170 calories/L
What are the considerations and indications of 5% dextrose in 0.45% saline?
Same as 0.45% NaCl except provides 170 calories
What are the considerations and indications of 5% dextrose in 0.9% saline?
Same as 0.9% NaCl except provides 170 calories/L
What are the indications and considerations for Ringers solution?
Similar in composition to plasma except that it has excess Cl-, Mg2+ and no HCO3^-. Does not provide free water or calories. Used to expand the intravascular volume and replace ECF losses
How does water movement between capillaries occur?
Capillaries surrounded by endothelial cells which separates them from the interstitium. Movement across epithelial cells is called trans-cellular, between the cells paracellular -determined by how ‘tight’ or ‘leaky’ the epithelia or endothelia cells are
If water transport is entirely passive, why do we have aquapori(s?
They allow greater flux of water across membranes, depending on osmotic gradients
Because it is simple diffusion, water transport doesn’t show saturation and has linear kinetics
If membrane is impermeable to NaCl in salt solution(reflection coefficient=1)…
Water moves in direction of low solute concentration to high solute concentration
What are the driving forces for water movement within the body?
2 major driving forces for water movement in the body :
- osmotic
- hydrostatic driving forces
The osmotic forces are associated with the concentration of solutes within the fluid — water wanting to move to an area with high solute concentration
What are hydrostatic pressures? What are their effects?
This is the effect of gravity on the fluid across capillary endothelial cells(CV, Renal)
Hydrostatic forces across membranes at the cellular level are 0 since membranes cannot withstand large hydrostatic f9rces water movement is governed by solute concentration —> this 8s not true 9f solute transport across vasculature!! Pressures matter!!
What is osmolarity?
Total concentration of all particles in solution
Osmolarity= osmotic coefficient(usually 1) xnumber/mole of particles in solution x concentration
What is tonicity?
Concentration of only the osmotically active particles
- only impermeable particles contribute to tonicity and cause changes in cell volume
- Tonicity of a solution describes the volume change of a cell at equilibrium
- Net water movement will be into the compartment that has the higher concentration of non-penetrating solutes
Contrast penetrating and non-penetrating solutes
Penetrating solutes: can enter cell (glucose, urea, glycerol)
-solutes will distribute to equilibrium
Non-penetrating solutes: cannot enter cell (sucrose, NaCl, KCl)
-water will move to dilute solutes
Determine relative concentration of non-penetrating solutes in solution and in cell to determine tonicity
It is the non-penetrating solutes that ultimately determine the tonicity of the solution (after the penetrating solutes have equilibrated)
What are iso-osmotic solutions?
If the total osmotic pressure of the solution is equal to that of the cell
What is a hypo-osmotic solution?
If the solution has less osmotic pressure than the cell
What is a hyper-osmotic solution?
If the solution has less osmotic pressure than the cell
What are the impacts of osmolarity and tonicity?
Osmolarity impacts transient changes in cell volume
Tonicity impacts long term steady state of cell volume (after the penetrating solutes have equilibrated
What is an isotonic solution?
If at equilibrium m it causes the cell to neither swell or shrink
-the non-penetrating solute concentrations on both sides of the cell membrane are the same
What of a hypertonic solution?
If it causes the cell to shrink
-non-penetrating solute concentration on the outside of the cell is higher than on the inside
What is a hypotonic solution?
If it causes the cell to swell
- non-penetrating solute concentration on the outside of the cell is lower than on the inside
