Fluids & Electrolytes Flashcards
Osmolarity
number of particles per LITER of solvent (mOsmoles/L)
Osmolality
number of particles per KG of solvent (mOsmoles/kg)
Tonicity
effective Osmoles in soln
i.e. solutes that don’t freely cross the mem & determine osmotic pressure gradients
Plasma
aq portion of blood WITH clotting factors (not RBC & WBC)
Serum
plasma WITHOUT clotting factors
Serum osmolality calculation
mOsm/kg = 2 Na + Glucose/18 + BUN/2.8
Serum osmolality normal range
275-295 mOsm/kg
reflects tonicity of serum
Hypovolemic presentation
- hypotension/orthostasis
- tachycardia
- poor skin tugor/dry mucus mem
- slow capillary refill
- cool extremities
Hypervolemic presentation
- hypertension
- edema
- weight gain
- jugular venous distention
Part(s) of kidney that secrete water
collecting duct via aquaporins
Part(s) of kidney that reabsorb water
prox tubule, ascending loop, distal tubule (Na reabs, water follows)
Causes of hypovolemia
- poor PO intake
- infection/fever
- hypermetabolic states (burn/trauma)
- blood loss
Maintenance fluids for adults
30-35 mL/kg
Maintenance fluids in peds
1st 10 kg -> 100 mL/kg/day
2nd 10 kg -> 50 mL/kg/day
> 20 kg -> 20 mL/kg/day
Adjustment for maintenance fluids in CKD, chronic liver disease, and mild HF
x 0.75
Adjustment for maintenance fluids in severe HF, and ESRD
x 0.5
Use normal maintenance fluids for..
- NPO for procedure
- CKD w/ mild dehydration
- HF w/ mod dehydration
- ESRD w/ severe dehydration
Adjustment for maintenance fluids in mild dehydration
x 1.25
Adjustment for maintenance fluids in mod dehydration
x 1.5
Adjustment for maintenance fluids in severe dehydration
x 2
Adjustment for maintenance fluids in hemodynamic shock
use a large vol bolus
Hypotonic fluid loss
insensible, sweat, urine
Isotonic fluid loss
blood, vomiting, diarrhea
D5W
- hypotonic
- no electrolytes
- 1000 mL free water
- shifts water intracell
1/2 NS
- hypotonic
- 77 mEq/L Na & Cl
- 500 mL free water
- shifts water intracell
3% NaCl
- hypertonic
- 513 mEq/L Na & Cl
- (-)2133 mL free water
- shifts water extracell
NS
- isotonic
- 154 mEq/L Na & Cl
- stays in extracell
Lactated ringers
- isotonic
- 130 mEq/L Na & 105 mEq/L Cl
- stays in extracell
5% albumin
- isotonic
- no electrolytes
- stays in extracell
Balanced crystalloids
mimic plasma electrolyte conc
- lactated ringers (acidotic)
- plasma-lyte A (neutral expensive)
N5 D5W
- isotonic
- stays in extracell
N5 D5W w/ 20mEq KCl
- hypertonic
- (-)125 mL free water
- shifts water extracell
1/2 NS D5W
- hypotonic
- 500 mL free water
- shifts water intracell
1/2 NS D5W w/ 20mEq KCl
- hypotonic
- 370 mL free water
- shifts water intracell
1/2 NS D5W w/ 40mEq KCl
- hypotonic
- 240 mL free water
- shifts water intracell
Hyponatremia labs
Na < 135
Drug-induced hyponatremia
syndrome of inappropriate anti diuretic hormone
- SSRI
- carbemazepine
- thiazides
- opiates
Cause of isotonic hyponatremia
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