Fluid Management Flashcards
Between the ISF and the ICF, ____ is the main determinant of extracellular osmotic pressure
Na+
Between the ISF and the ICF, ____ is the main determinant of intracellular osmotic pressure
K+
What is hematocrit?
- It is also known as the packed cell value (PVC).
- It is measured by dividing the volume of RBCs in a centrifuged blood sample by the total volume of the sample.
What are some ways that we can assess fluid volume status?
- Vital signs
- Skin turgor
- Mucous membranes
- Edema
- Lung sounds
- UO
- Hct
- Urine spec grav
- BUN/Creat
Why are maintenance fluids given?
To replace insensible losses
- from respiritory tract, GI tract, urine, feces, perspiration, etc
What is the formula for maintenance fluids?
4-2-1 Rule!
- 4cc/kg for the 1st 10 kg
- 2cc/kg for the 2nd 10 kg
- 1cc/kg for each additional kg
How to calculate fluid deficit
(Maintenance rate) x (number of hours NPO)
- But remember to look at pt history!
- Inpatient - may not have a fluid deficit if on maintinence fluids
- Also, if hypovolemic at baseline, they will have a larger than calculated fluid deficit.
- ex- on ACE inhibitors, have been vomiting, have NG to suction, chest tube, etc.
- Fluid should be replaced to restore HR, BP, and filling pressures prior to induction
- Normal UO is also desirable
Replacement strategy for fluid deficit
Replace over 3 hours
- Replace 1/2 deficit in 1st hour
- Replace 1/4 in the 2nd hour
- Replace final 1/4 in the 3rd hour
When should we begin fluid deficit replacement?
ASAP! Start fluids in the holding area. Want to make sure they aren’t totally dry on induction.
A soaked 4x4 holds _____cc of blood
10cc
A soaked lap sponge (lap tape) holds ___cc of blood
100-150 cc (soaked an dripping)
We tend to (over/under)estimate the amount of blood loss
Underestimate
Calculations for estimated blood volume (EBV)
Neonates
- Preemies = 95 mL/kg
- Term = 85mL/kg
- Infants = 80 mL/kg
- Children = 70 mL/kg
Adults
- Men = 75 mL/kg
- Women = 65 mL/kg
Calculating ABL
- [EBV (Hct - allowable Hct)] / Hct
- Remember that this is not the trigger for transfusion.
- Always look at your pt’s condition
- HR, BP, Sats, etc
- You may need to transfuse earlier than expected.
Fluid loss due to third spacing may be caused by
- Burns, trauma, infection.
- Loss of intravascular volume due to massive redistribution of fluids.
Surgeries and their expected evaporative/3rd space loss
-
Minimal (0-2 mL/kg/hr)
- Eye cases, lap chole, hernia, knee scope
-
Moderate (3-5 mL/kg/hr)
- Open chole, appendectomy
-
Severe (6-9 mL/kg/hr)
- Bowel surgery, total hip replacement (THR)
- Emergency (10-15 mL/kg/hr)
- Gun shot, MVC
D5W has an osmolarity of
253
(these are called maintenance fluids)
Isotonic solutions have an osmolarity of
300
(these are called replacement fluids)
Examples of isotonic solutions
- NS
- LR
- Plasmalyte
- Normosol
Examples of hypertonic solutions and their osmolarities
- Used for hyponatremia or shock
- D51/2NS (432)
- 3% NS (1026)
- Do NOT use for fluid resussitiatin
- Risk hyperchloremia, hypernatremia, cellular dehydration
Advantages and disadvantages of crystalloids
Advantages:
- Easily warmed and stored
- non-allergenic
Disadvantages:
- No O2 carrying or coagulation capacity
- limited intravascular life
- will be peed out by patient
- more risks of extravasation and edema
LR provides ____cc of free water per liter of fluid
100cc
This tends to lower Na+
LR
- the most physiologic crystalloid solution most similar to ECF
- Should NOT be given with blood products d/t Ca++
- Provice <strong>100</strong> <strong>cc</strong> of <strong>free water/L</strong> (which is lower sodium)
It is made of normal saline with additives:
- Na+ (130 mEq)→results in hyponatremia
- K+ (4 mEq/L) → avoid in hemodialysis pts!!
- Ca++ (2.7 mEq/L)
- Cl- (110 mEq/L)
- Lactate (27 mEq/L) → BUFFER! → will be converted to bicarbonate
- pH = 6.5
Normal Saline
- 0.9% NaCl in water
- Isotonic solution
- In large volumes increase Cl-→ dilutional hyperchloremic acidosis
- Prefered solution for diluting PRBCs → No K or Ca
Electrolytes:
- Na+ (154 mEq/L)
- Cl- (154 mEq/L)
- pH = 6.0
Normosol
- Exactly physiologic pH
- Can give with blood products
It is made of normal saline with additives:
- Na+ (140 mEq)
- K+ (5 mEq/L) → avoid in hemodialysis pts!!
- Ca++ (0 mEq/L)
- Cl- (98 mEq/L)
- pH = 7.4
- Magnesuium (3 mEq/L)
- Acetate (27 mEq/L)
- Guconate (23 mEq/L)
This can result from large volumes of .9%NS
High chloride-content hyperchloremic acidosis
This is the preferred solution for diluting PRBCs
Normal Saline
D5W can cause these adverse effects
Free water intoxication and hyponatremia
What use does D5W have?
- Really only used for diabetics who need just a little more glucose
- Is also used as a carrier for regular insulin
- Provides 170 - 200 calories / liter
- Used in neonates too
Half-life of colloid solutions
16 hours (but may be as short as 2-3 hours)