Fluids and Electrolytes Flashcards
How is TBW distributed in humans?
2/3 goes inside the cell
1/3 goes outside of the cell:
1/4 to vasculature, 3/4 to interstitial fluid
Difference between 5 and 25% albumin?
5% is isotonic and iso-oncotic (water goes to vasculature)
25% is isotonic and hyper-oncotic (goes to vasculature AND pulls water to vasculature from interstitial space)
In what disease states is albumin administration inappropriate?
Malnutrition Cirrhosis (exception: paracentesis, whatever that is)
What is the fluid requirement in adults?
1.5 L/day for the first 20 kg
then 20 mL/kg for each additional kg
INITIAL FLUID BOLUS in septic shock: 30 mL/kg
How does D5 distribute?
D5 is free water, so it distributes the same as TBW
2/3 to Cell
1/3 to extracellular space
1/4 to vasculature, 3/4 to interstitial space
How does 0.9% NS distribute?
NS = normal saline, sodium pump keeps sodium OUT of the cell so it ALL goes extracellular.
3/4 interstitial
1/4 vasculature
How does 0.45% NS distribute?
Half free water, so 1/3 goes into the cell!
The NS stays OUT of the cell bc of the sodium pump
so 1/3 to cell
2/3 to extracellular space
1/4 to vasculature, 3/4 to interstitial fluid
When is 0.45% NS used?
Often used as maintenance IV fluid in patients with hypernatremia
How does 5% albumin distribute?
Basically all of it stays in the vasculature because albumin is too big to cross the membranes
USED TO REPLETE VASCULAR VOLUME
How does 25% albumin distribute?
All stays in the vasculature bc albumin is too big to cross membranes, but it also pulls water from the interstitial space bc 25% albumin has a hyperoncotic pressure
When is 25% albumin used?
Often used in interstitial and pulmonary edema (bc it pulls water!)
Its use is followed by a loop diuretic
Which solutions can cause phlebitis?
Solutions that are more than 900 mOsm/L
Sodium chloride 3%
Which solutions can cause hemolysis?
Solutions that are less than 154 mOsm/L
Sterile water
Sodium chloride 0.225%
How to calculate osmol gap?
Osm of serum - Osm calc
Calculated osmoles: 2Na + Glu/18 + BUN/2.8
What electrolytes are normally found in the ICF?
Potassium (3.5-5 mEq/L)
Magnesium (1.5-2.8 mg/dL)
Phosphorous (2.7-4.5 mg/dL)
What electrolytes are normally found in the ECF?
Sodium (135-145 mmol/L)
Chloride (98-107 mmol/L)
Bicarb (24 mmol/L)
What is the treatment goal for hypokalemia?
4.0 mEq/L
How to treat hypokalemia?
First check Mg and adjust that first
Check ECG if K is less than 3.0 mEq/L
Use oral preferably, 20-80 mEq/day
IV 10-20 mEq/day, 20 requires central line
What should you do when a pt has high potassium?
Make sure it’s not a hemolyzed sample before treating
How do you treat hyperkalemia if it’s really high?
Stabilize cardiac membranes from effect of potassium (calcium chloride preferred for central line, calcium gluconate OK for peripheral access)
Shift K+ intracellularly with insulin (unless hyperglycemia is present)
or
with sodium bicarbonate (reverses H+/K+ ATP-ase activity)
or
B-2 agonist (increases Na+/K+ ATPase activity)
How do you treat hyperkalemia that is less than 6.5 mEq/L?
This is low so just remove K+ using sodium polystyrene (exchanges 1mEq/g in the large intestine)
Loop diuretics increase renal K+ excretion
Dialysis (esp if renal failure)
These take a while!!
How do you treat chronic hyperkalemia?
Patiromer
Non-absorbed cationic exchange polymer binds K+ in the GI tract
BINDS A LOT OF DRUGS - GIVE 6 HRS BEFORE OR AFTER ANYTHING ELSE
What is the treatment goal for hypomagnesemia?
Goal is over 2.0 mg/dL in hospitalized pts
Give Mg sulfate 1-2 g over 1 hour
Oral can give magnesium oxide 800-1600 mg/day*
*Note: Diarrhea/nausea common, and watch out for drug interactions with tetracyclines, fluoroquinones
What is the treatment for hypermagnesemia?
Supportive (Discontinue Mg)
Loop diuretic, IV calcium, hemodialysis (if severe)
