Perioperative Fluid Therapy (Exam IV) Flashcards
What is the formula for osmotic pressure?
P = (NRT) / V
P = pressure
N = # of molecules
R = constant
T= temp
V= volume
What is osmolarity?
particles / Liter of solvent
Higher osmolarity = _______ “pulling power”.
higher
What is osmolality?
particles / kg of solvent
What is normal serum osmolality?
280 - 290 mOsm
What three components produce oncotic pressure?
- Albumin
- Globulins
- Fibrinogen
What is the normal daily fluid intake?
- 750 mL from solids
- 350 mL from metabolism
- 1400 mL liquid intake
What is the normal daily fluid output?
- 1000 mL insensible loss
- 100 mL GI loss
- 0.5 - 1 mL/kg/hr UO
Urine output makes up approximately ___% of daily water loss.
60%
What sensors does the body have for fluid balance?
- Hypothalamic osmoreceptors
- Low pressure baroreceptors
- High pressure baroreceptors
Where are high pressure baroreceptors located?
Low pressure baroreceptors?
- High pressure → carotid sinus & aorta
- Low pressure → large veins & RA
Where is renin release from?
What does it do?
Renin (released from juxtaglomerular cells) cleaves angiotensinogen to make angiotensin I.
How long does RBC replacement via erythpoiesis take?
4-8 weeks
Where is aldosterone released from?
What does it do?
- Adrenal Cortex
- Na⁺ and H₂O retention
What issues are associated with normal saline use?
- Hemodilution
- ↑ Cl⁻ and K⁺
- Hyperchloremic metabolic acidosis
- ↑AKI & RRT in critical care patients
How does lactated ringers osmolarity compare to that of NS?
LR osmolarity is lower than NS.
Why is lactate added to LR?
Buffering capacity
___ will excrete excess water faster than NS.
LR
Suppresses ADH secretion, allows for diuresis.
Lactate formation relies on what?
Hepatic metabolism
Colloid particles are separated via a centrifuge. T/F?
False. Colloid particles cannot be separated from crystalloid solution (via centrifuge or filtration).
What are the hemodilutionary effects of colloid administration?
- ↓ plasma viscosity
- ↓ RBC aggregation
What fluid “class” can have adverse effects on the immune, coagulation, and renal systems?
Colloids
What is Hetastarch?
What is it derived from?
Modified natural polymers of amylopectin derived potato or corn/maize.
How much of intravascular volume expansion from hetastarch is still present in the system 90 minutes later?
70-80%
What are side effects of hetastarch?
- Coagulopathy
- Renal dysfunction
What is Dextran?
Highly branched polysaccharide
What type of surgery is dextran useful for? Why?
Microvascular surgery due to inhibition of clotting cascade.
What can dextran interfere with? (besides the clotting cascade)
Blood crossmatching due to coating of RBCs
What are signs/symptoms of high intravascular volume?
- ↑ capillary hydrostatic pressure
- Edema
- ↓ tissue O₂
- Poor wound healing
- Dysfunctional coagulation
What are standards for NPO status?
What is the classic formula for NPO/maintenance fluid replacement?
4-2-1 Rule
1st 10kg = 4 mL/kg/hr → 40mL/hr
2ⁿᵈ 10kg = 2 mL/kg/hr → 20mL/hr
Each 1kg over 20kg = 1mL/kg/hr
What would the maintenance fluid rate (4-2-1 rule) be for a 110kg patient?
40 mL + 20 mL + (90 x 1mL/kg/hr) → 150 mL/hr
What would the maintenance fluid rate be for a 18kg toddler?
1st 10kg → 40 mL
2ⁿᵈ 8kg → 16 mL
= 56 mL/hr
How is fluid deficit replaced in a surgery?
½ calculated volume in 1st hour
¼ volume in 2ⁿᵈ hour
¼ volume in the 3rd hour
How is fluid deficit calculated?
hours NPO x 4-2-1 maintenance rate
How is hourly intraoperative volume replacement calculated?
Deficit + Maintenance + EBL
How much blood do lap sponges hold?
100 mL
How much blood do Raytech’s hold?
20 mL
How much blood does a 4x4 hold?
10mL
What would the replacement volume rate be for a surgical case that exhibits minimal (robotic, toe pin, cataract, etc.) evaporative/redistributive volume loss?
0-2 mL/kg/hr
What would the replacement volume rate be for a surgical case that exhibits moderate evaporative/redistributive volume loss?
2-4 mL/kg/hr
What would the replacement volume rate be for a surgical case that exhibits severe evaporative/redistributive volume loss?
4-8 mL/kg/hr
How is the Parkland burn resuscitation formula calculated?
4 mL/kg/ %BSA burned
How is the volume calculated via the parkland formula given?
½ in the 1st 8 hours
½ in the next 16 hours
What are the general characteristics of goal directed therapy?
- Volume administration based on hemodynamics
- 1-3 mL/kg/hr crystalloid
- 250cc fluid challenges for ↓SV
- 1:1 colloids for blood loss
What is normal SVV?
(PPV, SPV as well)
10 - 15 %
What are the limits to assessment of volume via arterial waveform monitoring?
Low HR and/or RR
Irregular HR
Mechanical ventilation
Increased abdominal pressure
Thorax open
Spontaneous ventilation
