Osmolarity And Tonicity

Question 1

What are the types of solutions?

Answer 1

Isotonic- no volume change

Donate water to cell- hypotonic

Sequester water from cell- hypertonic

Question 2

What are the rules for normal functioning cells?

Answer 2

1. All hypo-osmotic solutions are hypotonic
2. ISO-osmotic solutions can be hypo or isotonic
3. 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

Question 3

Give a list of intravaneous fluid

Answer 3

5% dextrose in water- isotonic, but physiologically hypotonic

10% dextrose in water- hypertonic

0. 45% saline- hypotonic
1. 9% saline -isotonic
2. 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

Question 4

What are the indications and considerations for 5% dextrose in water?

Answer 4

Provides free water necessary for renal excretion of solutes, used to replace water losses and treat hypernatremia, provides 170 calories/L. No electrolytes

Question 5

What are the indications and considerations for 10% dextrose in water?

Answer 5

Provides free water only, no electrolytes, provides 340 calories/L

Question 6

What are the indications and considerations for 0.45%saline?

Answer 6

Provides free water in addition to Na+ and Cl-. Used to replace hypotonic fluid losses. Used as maintenance solution. Provides no calories

Question 7

What are the considerations and indications of 0.9% saline?

Answer 7

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

Question 8

What are the considerations and indications of 3.0% saline?

Answer 8

Used to treat symptomatic hyponatremia, must be administered slowly with extreme caution because it may cause dangerous intravascular fluid overload and pulmonary edema

Question 9

What are the considerations and indications of 5% dextrose in 0.225%saline?

Answer 9

Provodes Na+, Cl- and free water. Used to replace hypotonic losses and treat hypernatremia, provides 170 calories/L

Question 10

What are the considerations and indications of 5% dextrose in 0.45% saline?

Answer 10

Same as 0.45% NaCl except provides 170 calories

Question 11

What are the considerations and indications of 5% dextrose in 0.9% saline?

Answer 11

Same as 0.9% NaCl except provides 170 calories/L

Question 12

What are the indications and considerations for Ringers solution?

Answer 12

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

Question 13

How does water movement between capillaries occur?

Answer 13

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

Question 14

If water transport is entirely passive, why do we have aquapori(s?

Answer 14

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

Question 15

If membrane is impermeable to NaCl in salt solution(reflection coefficient=1)…

Answer 15

Water moves in direction of low solute concentration to high solute concentration

Question 16

What are the driving forces for water movement within the body?

Answer 16

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

Question 17

What are hydrostatic pressures? What are their effects?

Answer 17

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!!

Question 18

What is osmolarity?

Answer 18

Total concentration of all particles in solution

Osmolarity= osmotic coefficient(usually 1) xnumber/mole of particles in solution x concentration

Question 19

What is tonicity?

Answer 19

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

Question 20

Contrast penetrating and non-penetrating solutes

Answer 20

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)

Question 21

What are iso-osmotic solutions?

Answer 21

If the total osmotic pressure of the solution is equal to that of the cell

Question 22

What is a hypo-osmotic solution?

Answer 22

If the solution has less osmotic pressure than the cell

Question 23

What is a hyper-osmotic solution?

Answer 23

If the solution has less osmotic pressure than the cell

Question 24

What are the impacts of osmolarity and tonicity?

Answer 24

Osmolarity impacts transient changes in cell volume

Tonicity impacts long term steady state of cell volume (after the penetrating solutes have equilibrated

Question 25

What is an isotonic solution?

Answer 25

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

Question 26

What of a hypertonic solution?

Answer 26

If it causes the cell to shrink

-non-penetrating solute concentration on the outside of the cell is higher than on the inside

Question 27

What is a hypotonic solution?

Answer 27

If it causes the cell to swell

• non-penetrating solute concentration on the outside of the cell is lower than on the inside