Exam 3 Flashcards
1
Q
Colloid
A
a substance microscopically dispersed evenly throughout another substance. Colloids contain larger insoluble molecules, such as gelatin or albumin. Blood is a colloid; mixture of two different phases of matter
2
Q
Crystalloids
A
are aqueous solutions of mineral salts or other water-soluble molecules. Normal saline is a crystalloid; dissolved- no suspended
3
Q
Osmolality
A
is a measure of the osmoles of solute per kilogram of solvent (osmol/kg or Osm/kg); per mass
4
Q
Osmolarity
A
is the measure of solute concentration, defined as the number of osmoles (Osm) of solute per liter (L) of solution (osmol/L or Osm/L); per volume
5
Q
Colloid Osmotic Pressure (Oncotic Pressure)
A
osmotic pressure exerted by proteins in blood plasma that pulls water into the circulatory system
6
Q
Tonicity
A
the state of being hypertonic, hypotonic, and isotonic, is related to how much osmotic pressure is exerted on a membrane by a fluid; measure of the osmotic pressure gradient (defined by water potential of the 2 solutions) of two solutions separated by semipermeable membrane
7
Q
Osmotic Pressure
A
is the pressure which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane
8
Q
What was the ECC primed with during early years?
A
“Fresh” heparinized homologous blood
9
Q
Mannitol
A
aka. Osmitrol; oncotic agent, pulls fluid into blood stream; crystalloid
10
Q
Crystalloid Prime Consists of….
A
Dextrose
pH balanced crystalloid fluids
mannitol (Osmitrol)
11
Q
Advantages of crystalloid prime
A
Easy to handle during priming/de-airing
Cheaper
No anaphylactoid reactions
12
Q
Crystalloid Solution Examples
A
Plasmalyte Normosol 0.9% Normal Saline Lactated Ringers D5 0.9% NS D5 0.45%NS D5 0.33% NS D5 0.18% NS
13
Q
PlasmaLyte Characteristics
A
Closely mimics human plasma
Electrolytes, osmolality & pH (similar to human)
Buffer capacity
Anions: Acetate, gluconate, lactate converted to bicarb, Co2 and water
No evidence that it is superior to other crystalloids
14
Q
Plasmalyte Advantages
A
Volume/Electrolyte deficit correction
Addresses acidoses
15
Q
PlasmaLyte Disadvantages
A
Fluid overload Edema with weight gein Lung edema Worsening of ICP Magnesium: PVR, HR, worsen ischemia
16
Q
Magnesium in Prime
A
Book says its a problem
Works in concert with calcium
Partially replenishes myocytes
No substantial effect on SVR based on research
17
Q
Lactated Ringer’s
A
“Balanced” electrolyte solution with lactate added
Lactate converted into bicarbonate by a functioning liver into bicarbonate
18
Q
Normal Saline (0.9% saline solution)
A
Must add bicarb because its so acidic
Matches blood tonicity
Just sodium chloride
19
Q
Colloid Prime Characteristics
A
Contains protein or starch
Preserve high COP in the blood
20
Q
Colloid Prime Advantages
A
Maintain COP and reduce tissue edema
21
Q
Colloid Prime Disadvantages
A
Colloids associated with increased incidence of anaphylactoid reactions and clinical coagulopathy
22
Q
Colloid Examples
A
Albumin
Dextrans
Gelatins
Hydroxyethyl starch (Hespan)
23
Q
How is albumin sterilized?
A
Cold filtered
24
Q
Hypertonic
A
Osmolarity > 350 mOsm/L
Solution cannot be “hypertonic” unless there is some indication of what it might be hypertonic to; greater amt of solbe more hypertonic
25
Is D10-10% Dextrose has what tonicity?
Hypertonic (temporarily)
Becomes hypotonic metabolizes sugar
Becomes water
26
Hypotonic
Osmolarity <250 mOsm/L
Distilled water is hypotonic to everything
Causes fluid to shift, lowers osmolarity, allows fluid to shift out of vessel into cells and interstitial space
Hypotonic fluids have the potential to cause sudden fluid shifts out of bloodvesels
27
Examples of Hypotonic Fluids
0.45% NS and 0.25% NS
28
Istonic
~285-295 mOsm/L
| Freely move into and out of the intravascular compartments and increase circulating volume in the cells
29
Osmosis
Movement of water through a semipermeable membrane from an area of lower concentration of solute to higher concentration of solute
30
Osmotic Pressure
pressure which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane
31
Oncotic Pressure
Created by the presence of large protein molecules such as albumin (55%) Immunoglobulins (38%) Fibrinogen (7%) and other regulatory and clotting factors tend to retain fluid in the capillaries
*Note: oncotic pressure is a type of osmotic pressure
32
Hydrostatic Pressure
pressure of the intravascular fluid against hte wall of the vein
33
How to convert L to kg?
1 Liter of H20 at 4 degrees C = 1 kg (2.205 lbs)
34
Advantages of Hemodilution
Decreased blood viscosity
Improved regional blood flow
Improved oxygen delivery to tissues
Decreased exposure to homologous blood products
improved blood flow at lower perfusion pressure (lower shear stress), especially during hypothermic perfusion
35
How much do you hemodilute?
Most centers try to achieve hematocrits below 30% during CPB.
36
What's the normal priming volume range?
1000-1500 mL
37
Advantage of Albumin in Prime
Increases COP white at the same time (at least temporarily) attenuating the platelet-lowering effects of CPB
38
Basic Prime Constituents: Adults
```
Normosol/PlasmaLyte
Hetastarch/Albumin
Antibiotic
NaHCO3
Mannitol
Heparin 10k units
```
39
Basic Prime Constituents: Pediatrics
```
Normosol
25% Albumin
Antibiotic
Solumedrol
NaHCO3
Heparin 100 units
Mannitol
CaCl
PRBCs
```
40
25% Albumin
```
Large molecule
Aids pacificiation of tubing
Elevates COP and serum osmolarity
Good osmotic "Pull" from tissues (1.3:1)
A Jehovah's Witness "no-no"
```
41
Pacification
Foreign surface pacification may significantly reduce the detrimental effects of the CPB circuit
*Without albumin, pacification will lead to low circulating proteins
To date, albumin is the only intervention consistently shown to be beneficial
42
What two constraints does siphonage place on venous drainage?
1. venous reservoir must be below the level of the patient
| 2. lines must be full of blood (or fluid) or an air lock can occur and disrupt the effect
43
What influences CVP?
Intravascular Volume
| Venous compliance
44
What influences venous compliance?
Medications
Sympathetic Tone
Anesthesia
45
Solutions to Chattering/Fluttering/Chugging
Partially occlude clamp on venous line
| Increase the systemic blood flow
46
What is the ultimate limit to venous flow?
Amount of blood returning to the great veins from the body
47
Newton's Law of Universal Gravitaiton
F=G (m1m2/r^2)
| F=ma
48
How to calculate mass
volume x density
49
How to calculate weight
mass x gravity
50
What is the constant for gravity
9.8 m/sec^2
51
What is the density of water
1 @ 37 degrees C
52
Principle of transmission of fluid-pressure
pressure exerted in a confined incompressible fluid is transmitted equally in all directions throughout the fluid so pressure variations remain the same
53
Pascal's Law
1mmHg for every 13.6 mm heigh
Potential energy to do work
P=pgh
54
What is the normal siphon gradient?
30 to 40 mmHg
55
What three factors affect the siphon gradient?
CVP
Cannula Resistance
Height (to end of venous inlet tube)
56
Why use augmented venous return (AVR)?
- smaller diameter cannula and venous line (minimal volume)
- Long, narrow cannula (peripheral access)
- generate venous return using smaller heigh differential, smaller diameter cannula, smaller diameter venous line, no fluid in venous line
- Allow minimally invasive surgery
57
Methods of Augementation
VAVR
KAVR
Modified Roller Pump
58
Where do you monitor pressure in augmented return?
10 cm before pump inlet OR within hard-shell reservoir
59
Max negative pressure in augmented return
-60 to -100 mmHg
60
What could happen if the pump head is not occlusive?
Could pull retrograde
61
Why would you want shunt around roller pump to be partially occluded?
Prevent build-up of excessive negative pressure
62
Relief valve pressure limits
```
Low positive (+15 mmHg)
High negative (-150 mmHg)
```
63
Augmented Venous Return complications
Hemolysis
Decreased flow
Damage to vascular structures
Air aspiration
Over-pressurization of hard-shell venous reservoir (too much positive pressure)
Under-pressurization of hard-shell venous reservoir (too much negative pressure)
Imbalance between venous and arterial flows
64
When do we use AVR?
```
Minimally invasive surgeries
Femoral venous cannulation
unprimed venous lines (w.o VAP)
small heigh differential
smaller prime circuits (3/8'' venous)
pediatrics
possibly all cases
```
65
Calculating Effective Negative Pressure Gradient
Effective negative pressure gradient = negative pressure (VAVR) + Gravity Drainage
Effective negative pressure = Negative pressure (KAVR) + Gravity drainage
66
Range from the regulator in VAVR
-20 to -80 mmHg Range from regulator
67
Because pressurization is a risk in CPB and VAVR, what should you set the alarm to?
+10
68
In KAVR, what RPMs relate to what pressure
700-1100 RPM related to -50 to -80 mmHg
69
Actions of the Real Lung
Gas exchange
Filtration
Immune Function
Biochemical function
70
Actions of the Artificial Lung
```
Gas exchange
Secondary actions (filtration; drug delivery)
```
71
Diffusion proportion
Diffusion prop (PAS)/(Distance sq rt MW)
72
Only True membrane
Silicone
73
Surface Area of Natural vs Membrane
```
Natural= 70 m^2
Membrane= 0.6-4 m^2
```
74
Blood Path Width Natural vs Membrane
Natural 8 um
| Membrane 200 um
75
Blood path length Natural vs membrane
Natural 200 um
| Membrane 250,000 um
76
Membrane thickness Natural vs membrane
Natural 0.5 um
| Membrane 150 um
77
Maximum O2 Transfer Natural vs membrane
Natural 2,000 ml/min
| Membrane 400-600 ml/min
78
Oxygen gradient Natural vs membrane
```
Natural 105 (alv) - 40 (ven) = 65
Membrane [160 to 760] - 40= [120 to 720]
```
79
Carbon dioxide gradient natural vs membrane
Natural 40-45 = 5
| Membrane 45 - 0 = 45
80
CO2 during gas exchange
Chemical Reaction 0.4 seconds
Red Cell (including chemical reaction)
Plasma (lease amount of time)
Alveolar Wall
81
O2 during gas exchange
```
Alveolar Wall (most time) 0.25 seconds
Plasma (third most) 0.1 second
Red Cell (second most) 0.2 seconds
Chemical reaction (least)
```
82
Who made the film oxygenator?
Gibbon
83
Who made the rotating screen?
Dennis
84
Who made the bubble oxygenator?
DeWall-Lillehei
85
Who made the coil membrane?
Kolf
86
How do you remove bubbles with a bubble oxygenator?
Separation
| Absorption
87
How do you defoam a bubble oxygenator?
Silicon Antifoam-A (96% liquid polymer dimethylpoysiloxane and 4% particulate silica)
Bubble mechanically restrained by mesh net
Area low blood flow velocity-allow bubble chance to rise to surface
88
Pressure drops for bubble oxygenator & membrane oxygenator
30 mmHg bubble oxygenator
| 100 + mmHg membrane oxygenator
89
Where is a bubble oxygenator placed?
Placed before the arterial pump head
90
What materials does the defoaming/dububbling area have?
Steel wool
Polyurethane foam
Silicone Antifoam-A
91
What does a heat exchanger do in a bubble oxygenator?
Transfer heat
Additional gas exchange
Additional air removal
92
Basic components of a bubble oxygenator system
```
Gas sparger
Mixing column (turbulence)
Defoaming/Debubbling area
Heat exchanger
Arterial reservoir
```
93
Archimedes Principle
principle that states that a body immersed in a fluid is buoyed up by a force equal to the weight of the displaced fluid.
Buoyancy- used to eliminate air bubbles in the arterial reservoir
94
Bubble Size and Surface Area
Small: Surface: Volume ratio is high
Large: Surface: Volume ratio is low
95
What size bubbles has faster equilibration?
Small bubbles
96
Bubble size and O2 exchange
Small: O2 exchange efficient
Larger: O2 exchange less efficient
97
Bubble size and CO2 exchange
Small: Co2 exchange inefficient
Large: CO2 exchange efficient
98
Bubble size and GME potential
GME potential is high with small bubbles and low with large bubbles
99
What is FiO2 always set to?
100%
100
What is the purpose of turbulence?
Increases efficiency of gas exchange
101
Where does secondary gas exchange occur?
Heat exchanger/ defoamer
102
LOW Gas:Blood Flow
Decrease O2 transfer
Decreased CO2 transfer
Arterial PO2 goes down
Arterial PCO2 goes up
103
HIGH Gas: Blood Flow
Increased O2 transfer
increased co2 transfer
arterial PO2 goes up
arterial PCO2 goes down
104
Bubble Oxygenator Disadvantages
Balance O2 and CO2 transfer difficult to achieve
GME
Defoaming/filter increase foreign surface exposure w.o significant contribution to gas exchange efficiency
Direct blood:gas interaction damaging to plasma proteins and blood components
105
Membrane Types
Coil
Flat Plate
Capillary
106
"True Membrane"
Complete barrier between the gas side and the blood side
| Ex. Silicon
107
Hollow Fiber Oxygenators
```
Fibers:
200-250um in diameter
10-15 cm long
25-50 um thick
Blood flow Extra luminal/Intraluminal
```
108
Extraluminal Blood Flow
Blood outside, gas inside
| Greater surface area: less prime volume, decrease resistance to blood flow
109
Intraluminal Blood Flow
Blood inside, gas outside
110
Permeability Equation
Solubility x Rate of diffusion
111
Membrane Performance
```
Gas transfer characteristics of "membrane"
(gas exchange occurs at "pores")
Surface area
Fiber design- size & flow pattern
Gas flow: Blood flow ratio
(Influence co2 exchange only)
Gas blender (100% oxygen & room air)
FiO2:O2
```
112
Hollow Fiber Oxygenator Durability
long term use leads to "wetting" of the membrane surface resulting in plasma leakage through the pores; deterioration of oxygenator performance
113
Hollow Fiber Oxygenator Efficiency
Still 2-8 times less efficient as the natural lung
| Primary limitation to gas exchange is gas diffusion in the blood phase
114
Capillaries: Natural Lung
0.5 to 1.0 um length
| 3 to 7 um diameter
115
Capillaries: Artificial Lung
10-15 cm in length
| 150-250 um diameter
116
Flow Patterns: Natural Lung
Minimize shear forces
| Maximize RBC contact with capillary (1:1)
117
Flow Patterns: Artificial Lung
High shear forces
| RBC contact with "capillaries" is low
118
Contact Time: Natural Lung
Not a limitation in gas exchange even at extreme exercise
119
Contact Time: Artificial Lung
Gas exchange efficiency decrease with higher blood flows
120
Biocompatibility is associated with...
```
Type and composition of surface
Shear Forces
Pressure drop across oxygenator
surface area-to-volume ratio
Duration of exposure
patient status...
```
