Cell Physiology - Body Fluid Compartments Flashcards
what is normal plasma osmolarity?
285-295 mOsm/L
when infusing isotonic saline, what compartment increases in volume?
ECF only
Are there any osmolytes present in pure water?
NOPE
what usually is the first step in most of these problems?
calculating the total amount of osmoles in the body
when pure salt is added to the system, what changes?
osmolality goes up in both; volume goes down in ICF and increases in the ECF. right?
What is D5W?
glucose and water solution
what happens when D5W is infused? (long term)
- there is no increase in osmolarity because glucose gets metabolized
- it’s essentially the same as adding pure water to the system
- use the 60-40-20 rule to determine the how much will go in each compartment (ex: 1 liter will lead to .67 liters in ICF and .33 liters in ECF)
when might it be appropriate to administer D5W to a patient?
- following a free water loss
- ex: sweating profusely on a hot day, leaving the patient hypernatremic
why administer D5W and not pure water?
rbc rupture
what happens when there is an infusion of an isotonic solution?
- ECF volume increases alone; there is no movement of water across membrane
- therefore plasma concentration will not change in the long run
what are the components of plasma?
- main: RBCs, WBCs, platelets
- dissolved substances - proteins, electrolytes, nutrients, gases, waste products
How do people measure fluid compartment sizes?
- using indicator method
- the indicator must be able to cross the membrane
How do you determine the ICF fluid volume?
- find the ECF volume and subtract it from TBW?
oncotic pressure
osmotic pressure across the epithelium
starling forces are also known as _____
filtration and absorption forces
