Chapter 9: Fluids and Electrolytes Flashcards
Water weight distribution
2/3: intracellular (mostly muscle)
1/3: extracellular
Extracellular water distribution
2/3: Interstitial
1/3: plasma
Determine plasma/interstitial compartment osmotic pressures
Proteins
Determines intracellular/extracellular osmotic pressure
Sodium
MCC is iatrogenic; first sign is weight gain
Volume overload
What is the first sign of volume overload?
Weight gain
Can release a significant amount of water
Cellular catabolism
Normal saline:
[Na], [Cl]
[Na] = 154 [Cl] = 154
3% Normal saline
[Na], [Cl]
[Na] = 513 [Cl] = 513
Lactated ringer’s
[Na], [K], [Ca], [Cl], [Bicarb]
[Na] = 130 [K] = 4 [Ca] = 2.7 [Cl] = 109 [Bicarb] = 28
Calculate plasma osmolarity
(2Na) + (Glucose/18) + (BUN/2.8)
Normal plasma osmolarity
280 - 295
How does water achieve osmotic equilibrium?
Water shifts from areas of low solute concentration (low osmolarity) to areas of high solute concentration (high osmolarity) to achieve osmotic equilibrium.
Estimates of volume replacement
4 cc/kg/h for 1st 10kg
2cc/kg/h for 2nd 10kg
1 cc/kg/h for each kg after that
Best indicator of adequate volume replacement
Urine output
Fluid loss during abdominal operations
0.5 - 1.0 L/h unless there are measurable blood losses
When should you think about replacing blood?
> 500 cc
What are insensible fluid losses?
10 cc/kg/day; 75% skin, 25% respiratory, pure water
Replacement fluids after major adult gastrointestinal surgery:
1st 24 hours ->
After 24 hours ->
1st 24 hours: LR
After 24 hours: D5 1/2 NS with 20 mEq K+
Why switch to D5 1/2 after 24 hours with replacement fluids after major adult gastrointestinal surgery?
- 5% dextrose will stimulate insulin release, resulting in amino acid uptake and protein synthesis (also prevents protein catabolism)
How much glucose does D5 1/2 NS @ 125/h provide?
150g glucose per day (525 kcal/day)
GI fluid secretion:
Stomach
1-2 L/day
GI fluid secretion:
Biliary system
500 - 1,000 mL/day
GI fluid secretion:
Pancreas
500 - 1,000 mL/day
GI fluid secretion:
Duodenum
500 - 1,000 mL/day
Normal K+ requirement
0.5 - 1.0 mEq/kg/day
Normal Na+ requirement
1 - 2 mEq/kg/day
Electrolyte loss: sweat
Hypotonic (Na concentration 35-65)
Electrolyte loss: saliva
K+ (highest concentration of K+ in body)
Electrolyte loss: stomach
H+ and Cl-
Electrolyte loss: pancreas
HCO3-
Electrolyte loss: bile
HCO3-