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)
what is a colloid
fluid which contains both large organic macromolecules and electrolytes.
what happens when colloids are given IV
expansion of IV space, redistribution of water like isotonic crystalloids but lesser due to colloid binding to water
what are colloids theoretically good for? what tends to actually happen when given?
theoretically good for rapid volume expansion, hypovolemia, and hypoalbuminemia (albumin is a colloid) but in reality increased morbidity, mortality, dehydration, renal injury, coagulation issues can all occur because the body isn’t happy about metabolizing starches
when could you consider a colloid? which type?
hydroxyl ethyl starch (HES) is a synthetic colloid. can consider for short term BP support in anesthesia, use minimum volume needed. may be imprudent for critically ill patients
For a vomiting dog (assume no other issues), what type of fluid would you choose, and would you add anything to that fluid?
-Provided no other issues, isotonic crystalloids for replacement
-Potassium can be added (20 to 40 mEq/L). If you are ever adding K+ to fluid you cannot bolus
For a hyperkalemic animal, what type of fluid(s) are ideal?
- Unbalanced or balanced isotonic (replacement) crystalloids
- Balanced may be better as it can help correct acid-base issues and less likely to cause hyperchloremia –> otherwise contributes to metabolic acidosis and increases renal vascular resistance
How would you treat an initial hypoglycemic episode with dextrose? How does this differ to subsequent hypoglycemic episodes?
-50% dextrose in 2 parts, diluted in 0.9% saline as a bolus over 2 mins
-Subsequent hypoglycemic events, you should dextrose add to the infusion at 2.5 to 5% in 0.9% NaCl
- Do not bolus for subsequent hypoglycemic events
You have a hypochloremic animal with concurrent hypokalemia, what type of fluid would you use?
-Saline (0.9%) with potassium supplemented
Why would you be cautious to add dextrose to a SubQ fluid solution?
-Impacts the osmolality of the fluid, which may interfere with absorption into the body
Why would we provide albuterol/salbutamol puffs and dextrose to a patient that is hyperkalemic?
-Helps move K+ inside the cell
Why is it better to provide hyperosmolar fluids via a central venous catheter versus a peripheral intravenous catheter?
-With peripheral venous catheters, you may get phlebitis with a highly osmolar solution
Why do some balanced isotonic crystalloids provide magnesium?
-Commonly low in critically ill animals
When is intravenous catheterization indicated for fluid therapy?
-When you need to quickly expand the intravascular space (hypovolemia), deliver large amounts of fluid and/or have a critically ill patient
What type of clinical presentation/situation would SubQ fluids be most appropriate for?
-Animal that has had some additional fluid loss (e.g. vomiting, increased urination), but is not significantly (> 7%) dehydrated, and has overall a good mentation, and energy
What situations (4) would an intraosseus catheter be indicated?
-Very young animals that are too small for an IV catheter; patients that have clotting issues; edematous patients; obese patients; shock patients where veins are too collapsed to access
What is the maximum volume for maintenance fluid requirement that you can give at any one time subQ?
-Half the maintenance requirement at a time
What is one benefit of a central venous catheter over a peripheral venous catheter in terms of drug therapies?
-Central venous catheters, depending on the number of lumens, can allow you to administer multiple incompatible drugs or fluids
What is emergency venous cutdown?
-Basically, you dissect out the saphenous vein and make an incision on one side of the wall so that you can directly insert an IV catheter into the vein
What happens to the body when you provide fluids too quickly to a chronic hyponatremia case?
-Pontine demyelination
What happens if we correct chronic hypernatremia acutely?
-Will cause cerebeal edema and neurological signs
What are iogenic osmoles?
-Osmotically active molecules cells make to modulate their osmolarity relative to the interstitial environment
What are 4 pros of SubQ fluids compared to IV?
-Less expensive
-Minimal restraint
-Can be done outpatient
-Overall well tolerated
What are 4 complications of IO catheters?
-Osteomyelitis
-Bone marrow necrosis with hypertonic solutions
-Difficult to maintain long-term as continual nursing care is needed
-Discomfort/pain
True or false. Potassium phosphate cannot be provided with 0.9% saline, as it will precipitate with calcium.
-False. Potassium phosphate cannot be provided with Lactated Ringers (LRS actually contains some calcium unlike saline)
So if Na is 125 mmol/L and needs to go to 145 mmol/L, how long will that take?
145-125 = 20 mmol/L /0.5 mmol/L/h = 40 hours
So if Na is 125 mmol/L and needs to go to 145 mmol/L, how long will that take?
145-125 = 20 mmol/L /0.5 mmol/L/h = 40 hours
In a case of hyponatremia, where will iogenic osmoles go?
-Outside of the cell (increase interstitial osmolarity)
In a case of chronic hypernatremia where do iogenic osmoles go?
-Stay inside the cell
How much can we change sodium in either a chronic hyponatremia or chronic hypernatremia case?
-Cannot change Na more than 0.5 (ideal) to 1 mmol/L/hour
How long from the point of an electrolyte imbalance to the point when iogenic osmoles are being spit out/produced?
-24 to 48 hours
How long from the point of an electrolyte imbalance to the point when iogenic osmoles are being spit out/produced?
-24 to 48 hours
How long does fluid administered via SubQ take to fully absorb?
24 to 48 hours
For an acute hyponatremia, can we correct the electrolyte imbalance quickly?
yes
Before treating any sodium disorder, what are the two major questions you need to consider before treatment?
1) Is it acute (< 24 hours) or chronic (>24 hours)?
2) Did the body have time to spit out or make intracellular iogenic osmoles?
