Osmolarity/ Tonicity

How to calculate total body water?

- Body is 60% water

- Take the body weight (in kg) and multiply it by 0.6, gives water weight

- Take water weight and convert to liters (multiply by 1)

How do you convert pounds to kilograms?

1 lb = 0.454 kg

Multiply pounds by 0.454 kg

How much of the total body water is ICF?

About 2/3

How much of total body water is ECF?

About 1/3

What is the healthy plasma osmolarity range?

290-300 mOsM

What is the definition of osmolarity?

The number of particles in a solution, the concentration

What is the formula for osmolarity?

(mol x dissociation factor)/L OR molarity x dissociation factor

What is the definition for tonicity?

How the cell behaves/ nature of solute

Tonicity describes the ___, not the ____

Solution, cell

What does a cell do in a hypotonic solution?

Swell

What does a cell do in a hypertonic solution?

Shrink

What does a cell do in a isotonic solution?

Stay the same

In a hypotonic solution, there are more solutes …

Inside the cell then outside

In a hypertonic solution, there are more solutes …

Outside the cell then inside

In a isotonic solution, the solute concentration is…

Equal inside & outside the cell

What are the characteristics of normal saline?

Isosmotic & isotonic

What are the characteristics of D-5-W?

Isosmotic & hypotonic

What are the characteristics of ½ normal saline?

Hyposmotic & hypotonic

What are the characteristics of D5 normal saline?

Hyperosmotic & Isotonic

What are the characteristics of D5 ½ normal saline?

Hyperosmotic & hypotonic

What are the two types of particles?

Penetrating & non-penetrating

What is determined by non-penetrating particles?

Distribution of water & penetrating particles

Does penetrating particles effect the distribution of water?

No, p-particles will move across membrane until it is at equilibrium

What is deuterium oxide (D2O)?

Total body water

What is inulin?

ECF

What is Evan’s Blue?

Plasma volume, part of ECF

Osmosis is the ____ of water across the membrane

Diffusion (passive transport)

What is osmotic pressure?

Pressure due to water movement across the membrane

“Pulling” pressure from np-particles

For a dehydrated patient, it is better to give them a ____ solution

Hypotonic

How much Na is in normal saline?

0.9% ~ 9g for 1 L

In a hypotonic solution, there are more solutes ____ then _____ the cell

Inside, outside

In a hypertonic solution, there are more solutes ____ then _____ the cell

Outside, inside

What is the total body water for the physiology man in liters?

Total body water is 41.9469 ~ 42 L

Physiology man: 154 lbs

1.) Convert lbs to kgs: 154 lbs x 0.454 kg = 69.916 kg

2.) Find how much of that weight is from water: 69.916 kg x 0.6 = 41.9496 kg

3.) Convert kgs to liters: 41.9496 kg x 1 L = 41.9469 L

How many grams is in a liter?

1000g

How many grams are in a kilogram?

1000 g for 1 kg

What is the concentration formula?

c = sol/ vol

How do you solve for solute with the concentration formula?

sol = c x vol

How do you solve for volume with the concentration formula?

vol = sol/ c

How do you convert grams to moles?

Divide grams by the molar mass of the molecules

How do you convert mol to M?

Divide by 1 L

What is the dissociation factor for NaCl?

2

Na:1

Cl:1

What is D5W?

5% dextrose (glucose) in 1 L of water

How do red blood cells behave in normal saline?

They do not change because normal saline is isotonic

How do red blood cells behave in ½ normal saline?

Red blood cells swell because ½ NS is hypotonic

How do red blood cells behave in D5W?

Red blood cells swell because D5W is hypotonic

How do red blood cells behave in D5-NS?

They do not change because D5-NS is isotonic

How do red blood cells behave in D5-½ NS?

Red blood cells swell because D5-½ NS is hypotonic

Does osmolarity predict tonicity?

No

Osmolarity describes the number of solute particles in a solution. It compares a solution & a cell

Tonicity describes how a cell behaves in a given solution. Only describes the solution not the cell

What is the tonicity of a hyposmotic solution?

Can only be hypotonic

If a cell has fewer dissolved solutes compared to its surrounding, it can only ever

If solution A has more solutes then solution B, then solution A is ____ to solution B

Hyperosmotic

If solution A has more solutes then solution B, then solution B is ____ to solution A

Hyposmotic

What is the dissociation factor of glucose?

1

What is the dissociation factor of urea?

1

How many OsM is in mOsM?

1 OsM = 1000 mOsM

What is the molecular weight of glucose?

~180 g/mol