Osmolarity and Tonicity-Fluid Transport

Question 1

Penetrating Solutes

Answer 1

Can enter the cell:
Glucose
Urea
Glycerol
-Solutes will distribute to equilibrium

Question 2

Non-penetrating solutes

Answer 2

Cannot enter the 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

Question 3

Which solutes (non-penetrating vs. penetrating) solutes determine tonicity

Answer 3

It is the non-penetrating solutes that ultimately determine the tonicity of the solution (after the penetrating solutes have equilibrated)

Question 4

Tonicity of a solution

Answer 4

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 5

Iso-osmotic

Answer 5

Total osmotic pressure of the solution is equal to that of the cell

Question 6

Hyperosmotic

Answer 6

Solution has greater osmotic pressure than the cell

Question 7

Hypo-osmotic

Answer 7

Solution has less osmotic pressure than the cell

Question 8

Hypertonic

Answer 8

Solution causes cell to shrink
-Non-penetrating solute concentration on the outside of the cell is higher than on the inside

Question 9

Hypotonic

Answer 9

Causes the cell to swell
-Non-penetrating solute concentration on the outside of the cell is lower than on the inside
-Tonicity impacts long term steady state of cell volume (after the penetrating solutes have equilibrated)

Question 10

5% Dextrose in Water

Answer 10

Isotonic, but physiologically hypotonic
-Provides free water necessary for renal excretion of solutes, used to replace water losses and treat hypernatremia, and energy (170 calories/L). No electrolytes present

Question 11

10% Dextrose in Water

Answer 11

Hypertonic
-Provides the free water only, non electrolytes, Provides 340 calories/L

Question 12

0.45% Saline

Answer 12

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

Question 13

0.9% Saline

Answer 13

Isotonic
-Used to expand intravascular volume and replace extracellular fluid losses. Only solution that may be administered with blood products. Contains Na+, and Cl- in excess plasma levels. Does not provide free water, calories, or other electrolytes. May cause intravascular overload or hyperchloremic acidosis.

Question 14

3.0% Saline

Answer 14

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

Question 15

5% Dextrose in 0.225% Saline

Answer 15

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

Question 16

5% Dextrose in 0.45% Saline

Answer 16

Hypertonic
-Same as 0.45% NaCl except provides 170 calories

Question 17

5% Dextrose in 0.9% Saline

Answer 17

Hypertonic
-Same as 0.9% NaCl except provides 170 calories

Question 18

Ringers Solution

Answer 18

Isotonic
-Similar in composition to plasma except that it has excess Cl-, no Mg2+ and no HCO3-. Does not provide free water or calories. Used to expand the intravascular volume and replace ECF losses.