Electrolytes and Fluids - Fluid Mgmt & Osmolality
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A normal adult has ~___L of fluid
42L of fluid
Distribution of total body fluid (TBF) is estimated as what percentage of lean body weight (LBW) in men? In women?
- Men - 60% LBW
- Women 50% LBW
Distribution of total body fluids include ___% of TBF being intracellular and ___% being extracellular.
Extracellular space includes __% interstitial and __% intravascular space
60% intracellular, 40% extracellular
Extracellular: 75% interstitial, 25% intravascular
Intracellular space is highly permeable to what? Extracellular space is permeable to all solutes except what?
- Intracellular - water
- Extracellular - all solutes except proteins
Lactated ringers (LR) consists of what? (5)
For 0.9% NaCl, LR, and D5W, what % of fluid can be found in intracellular, extracellular, and intravascular space?
0.9% NaCl and LR: 0% intracellular, 100% extracellular, 25% intravascular
D5W ~ free H2O: 60% intracellular, 40% extracellular, 25% intravascular
Between 0.9% NaCl, LR, D5W, which fluids should NOT be given to patients w/elevated ICP (intracranial P)?
D5W d/t crossover of glucose into cerebral cells
Colloids include what 4 fluids?
- 1. pRBC's
- 2. Pooled human plasma (5% and 25% albumin, 5% plasma protein fraction)
- 3. Dextran (semisynthetic glucose polymers)
- 4. Hetastarch ( semisynthetic hydroxyethyl starch)
What GENERAL type of fluid is too large to cross capillary membranes and remain 100% in intravascular space?
Which SPECIFIC type of fluid causes a shift from interstitial to intravascular fluid d/t 5x increased oncotic P than normal plasma?
25% albumin (100ml of administered fluid will result in 500ml fluid into intravascular space)
25% albumin should be AVOIDED in patients needing ______ ___________, and why? Patients that may benefit from this fluid include those who need __________ of fluids.
Avoid in pt's who need fluid resuscitation d/t shifting out of IS space causing dehydration.
This will benefit in those who need redistribution of fluids (ascites, pleural effusions)
What are 2 possible reasons that could result in intravascular fluid depletion? When do signs/symptoms start to occur?
Hemorrhage or septic shock
S/Sx start to occur when 15% of blood volume is lost = 750ml (of 5L) OR when it shifts out of intravascular space (severe sepsis)
What are 2 main differences in fluid administration processes between fluid resuscitation and maintenance of fluids?
- 1. Fluid resuscitation occurs rapidly in 500ml to 1000ml boluses
- 2. ...and is administered via central IV cathether
- (Maintenance is continuous IV infusion via peripheral IV catheter)
What are the NINE s/sx of intravascular volume depletion? (HINT: 3 symptoms, 5 objective signs, 1 "wait and see")
- 1. Dry mucous membranes
- 2. Decreased skin turgor
- 3. Dizziness
- 4. Tachycardia >100bpm
- 5. Hypotension SBP<80mmHg
- 6. Orthostatic changes in HR or BP
- 7. Inc'd BUN/SCr ratio >10:1
- 8. Dec'd UOP
- 9. Improvement in HR or BP after 500ml-1L fluid boluses
Although crystalloids are recommended during fluid resuscitation, LR was theoretically preferred d/t what? Why does this NOT matter during shock?
LR preferred d/t lactate metabolizing to bicarbonate and useful in metabolic acidosis
Doesnt matter b/c lactate metabolism impaired during shock (ineffective source of bicarbonate)
What 3 common scenarios would colloids be considered over crystalloids during fluid resuscitation?
- 1. When ~4-6L crystalloids have failed to achieve hemodynamic goals OR there is clinically significant edema from crystalloid
- 2. Specifically, albumin may be considered in patients with albumin <2.5g/dL who require large volumes of resuscitation fluids
- 3. 25% albumin considered in conjunction w/diuretics for clinically signif edema (i.e. pulm edema -->resp failure) AND albumin <2.5g/dL when appropriately dosed diuretics are ineffective
What are the 2 formulas for daily maintenance IV fluids for adults and children?
- 100ml/kg for 1st 10kg
- 50ml/kg for next 10kg
- 20ml/kg for every kg over 20kg
2nd (adults only): 20-40ml/kg/day
What are the typical maintenance IV fluids for patients?
D5W with 0.45% NaCl plus 20-40mEq of KCl per liter
What is the normal plasma osmolality between?
Whats the diff b/w osmolality and osmolarity? Whats the diff for plasma?
- Osmolality: Osm solute/kg solvent
- Osmolarity: Osm solute/L solution
No difference in plasma of both... only ~1%
What is the estimated equation for plasma osmolality?
mOsm/kg: (2xNa) + (GLU/18) + (BUN/2.8)
What occurs to the cell and plasma when there are increases or decreases in plasma osmolality?
Inc'd plasma osmolality: Shift out into plasma, cells dehydrate and shrink
Dec'd plasma osmolality: Shift INTO cell, cells overhydrate and swell
What occurs to cells when patients receive hypertonic, and hypotonic fluids? For hypotonic, at which osmolarity does the shift occur?
- Hypertonic: Cells shrink
- Hypotonic osmolarity <150mOsm/L: Cells swell
Explain what occurs to RBC's, and brain cells when hypotonic fluids are given. For brain cells, when does it typically begin?
- RBC: Swell and rupture - hemolysis
- Brain cells: Cerebral edema and herniation, occurring in less than 2 days w/hypoNa
Of the four, which electrolyte has a valence of 2? What does this do to equivalent weight (g)?
Na, K, Cl, Mg.
- Valence of 2, so MW is divided by 2
Of the three, which has 3 oSm?
NaCl, KCl, CaCl2
How do you convert 23.4% NaCl to g/ml?
23.4% = g/100ml = 23.4g/100ml
What is the importance of osmotic coefficient (used to calculate osmolarity of IV fluids b/c salt forms dont completely dissociate in solution).
Not considered clinically relevant, but for NS, it is 0.93 (and thus 0.9% NaCl)
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