Fluids Flashcards
what is a crystalloid solution and what can it enter
has water and mainly electrolytes (mostly NaCl), only small molecs (dextrose, buffers), can enter all body compartments
what is the difference between hypotonic, isotonic, and hypertonic crystalloids
concentration of electrolytes they contain; relative ability of solution to initiate water movement across membrane, and depends on osmolarity of fluid compared to blood
what is is osmolarity
measure of total concentration of solute particles (osmotically active particles) in a solution; function of NUMBER of particles
what are the 3 most important kinds of osmotically active particles to know
electrolytes, glucose, urea, also ketones and mannitol
what is blood osmolality? and give formula for blood osmolality please
movement of water generated by osmotic pressure of blood. osmolality = 2 (Na + K) + glucose + BUN
what happens when you give isotonic fluids IV? how long does isotonic crystalloid fluid stay in intravascular space
within 45 minutes, 75% of the given electrolytes and water exit the IV space and enter the interstitial space; 25% of the volume remains IV
(so this is why isotonic crystalloids are a good choice for replacement fluid for hypovolemia and dehydration)
isotonic crystalloids have a concentration of Na and Cl close to what is in blood, so they replenish the intravascular space. what 2 conditions are they generally used to treat?
replacement fluid for hypovolemia and dehydration
isotonic crystalloids have a concentration of Na and Cl close to what is in blood, so they replenish the _______ space
intravascular
tell me 3 common isotonic crystalloid fluid types
0.9% NaCl, ringer lactate (LRS), and plasmalyte. (they all have the same osmolarity; 0.9% NaCl has the highest Na and Cl content; LRS has lactate; plasmalyte has acetate)
which isotonic crystalloids have buffers? what kind of buffer? what are these crystalloids with buffers called?
0.9% NaCl, no buffer, called unbalanced (so, not good for shock unless hypochloremic metabolic alkalosis, eg. profuse vomiting in dogs).
LRS has lactate and plasmalyte has acetate. called balanced crystalloids.
what do buffers do
many patients are acidotic (shock, GDV, vomiting, etc), so metabolism of buffer produces bicarbonate which binds to H+ ions, minimizing changes in pH.
what are isotonic fluids good for? what are they bad for?
good for hypovolemia and interstitial dehydration, but not for intracellular dehydration (no driving force to move fluids into this space).
isotonic crystalloid large volumes can be used to treat hypovolemic shock, but what is main caution with this?
cautious about risk for edema or might die if edema worsens: eg. hypoalbuminemic patients, cardiac patients, etc. you may still have to give in these patients, but with close monitoring
what are 4 kinds of hypotonic crystalloids commonly used
0.45% NaCl, D5W, 2.5% dextrose in 1/2 strength LRS, normofundin (has a high K+, can’t bolus)
what should we use hypotonic crystalloids? 3 cases
- need fluid, but presence of cardiac disease (low Na, less likely to cause edema bc it leaves blood space quickly)
- patient with hypernatremia
- normal patient with normal maintenance fluid needs
what happens when you give hypotonic fluid IV
expands the IV space slightly but rapidly diffuses into interstitial space and into cells
can you use hypotonic crystalloids to treat shock
no! leaves IV space too quickly
what is effect of dextrose in fluids? what is it equivalent to giving?
dextrose taken up by cells immediately, leaving pure water to equilibrate, so considered equivalent to pure water. it is used to provide osmolarit
can you bolus dextrose IV?
not given as bolus bc the water will explode the RBCs, UNLESS patient is hypoglycaemic (dextrose won’t be absorbed as quickly, so not left with pure water therefore not dangerous to cells). in this case you give as 50% bolus with 50% 0.9% NaCl, then add small amount dextrose to the solution
which hypertonic crystalloid is commonly used
7.5% NaCl
what happens when we give hypertonic crystalloids IV?
small volume of fluid will provide rapid and significant expansion of the IV space. within 45 min, 75% of the water will diffuse back into the interstitial space (like isotonic crystalloids)
when do we give hypertonic fluids? 2 cases please. what is it not good for?
hypovolemia and cerebral edema (hypertonic saline will suck up inflammation and increase the IV volute to improve perfusion).
not good for interstitial dehydration or intracellular dehydration (it is saltwater)