Exam 1

Question 1

first successful open heart operation using cardiopulmonary bypass was done by

Answer 1

John Gibbon on May 6, 1953

Question 2

who is the father of ECMO?

Answer 2

Robert bartlett

Question 3

who practiced cross-circulation?

Answer 3

Dr. Walton Lillehei

Question 4

who discovered heparin and in what year?

Answer 4

Jay Mclean 1916

heparin was first clinically used in humans in 1935

Question 5

roller heads

Answer 5

used for A line, suckers, and cardioplegia
positive displacement pump
NOT afterload dependent
occlusive
max RPM 150

Question 6

volume per foot of tubing size

Answer 6

3/16’ (4.5 mm( = 5 ml/ft
1/4“ (6 mm) = 9.65 ml/ft
3/8“ (9 mm) = 21.71 ml/ft
1/2“ (12 mm) = 38.61 ml/ft

Question 7

centrifugal heads

Answer 7

used for arterial line
non occlusive
afterload dependent/ non-positive displacement pump
- flow is based on resistance (afterload)
max RPM 3500-4000 RPM

at normal resistance and max RPM, can go up to 7-8 LPM

heat generation–> causes hemolysis, prone to clot formation
- heat generation and hemolysis occurs mostly where RBC dont have alot of movement (up and center of centrifugal head)

Question 8

what resistance the blood encounters after it leaves the pump

Answer 8

1. patients systemic vascular resistance
2. oxygenator
3. length and radius of tubing
4. viscosity of blood (hematocrit)
   cannula size and placement

Question 9

priming volumes for centrifugal heads

Answer 9

i. LivaNova Revolution = 57 ml
ii. Terumo Sarns = 48 ml
iii. Medtronic Affinity = 40 ml
iv. Rotaflow = 32 ml
v. Centrimag = 31 ml

Question 10

signs of hemolysis on CPB

Answer 10

1 source of immediate massive hemolysis is “pump head thrombosis” → due to increased turbulence

hemoglobinuria - plasma free hemoglobin excreted from the kidneys into the urine –> looks red-ish or pink urine observed

1. Turbulent flow > 2000 (Reynold’s #)
2. Laminar flow < 2000 (Reynold’s #)

“Pump head thrombosis” - large clot formation in a centrifugal head that is NOT
easily visible, typically occurs toward the end of CPB when flow is decreased
(less movement of blood) or during ECMO

Question 11

safety mechanisms

Answer 11

E clamp (fast clamp) or retro guard valve (1-way valve) –> prevent backflow

Question 12

flow meter

Answer 12

accurately measures velocity
two types of low meters are ultrasonic and electromagnetic

The flow meter is ALWAYS after the oxygenator because of possible open purge (recirc) lines

you can clamp the outflow tubing distal to the pump and centrifugal head will recirculate in within the pump (for centrifugal heads)

Question 13

Venous reservoirs

Answer 13

what holds/collects the venous blood that is drained from the patient

1. venous filter –> 100-200 microns (less fine filtrtion than cardiotomy
2. has less defoamer w/ antifoam A –> small amount of air comes through venous line through entrainment at loose purse strings or increased vacuum-assisted venous drainage (Venturi effect)
3. Sock –> imbedded into the pleated filter
4. Anything introduced into the venous line has a greater chance of sending
   air bubbles to the patient than when going through the cardiotomy
5. Entrained air has a higher tendency to go through the venous
   reservoir/filter rather than the cardiotomy because it has less fine of a
   filter and has less defoamer compared to the cardiotomy
6. Venous line from pt mix w/ more blood than air

Question 14

PRIMING VOLUMES FOR VENOUS RESERVOIRS

Answer 14

MEDRTRONIC AFFINITY = 200 ML
ii. Sorin Inspire = 150 ml
iii. Terumo Capiox = 150 ml

Question 15

Cardiotomy

Answer 15

vents, suckers and waste from the field (anything from the chest) go into the cardiotomy; it is for cardiotomy drainage, NOT venous drainage

1. Finer filtration → ~ 40-47 microns
   a. Cardiotomy is a depth type filter
   - has multiple filter mediums
   b. Depth filter - better filtration than screen filter, but higher
   resistance; solution must pass through different mediums (i.e. defoamer sponge, filter, sock)
2. More defoamer → lined with Antifoam-A (more than in venous reservoir)

a. Antifoam-A breaks the surface tension of air bubbles 3. Suckers and vents from the field mix w/ more air than blood

Question 16

Priming volumes for oxygenators

Answer 16

i. Sorin Inspire 8F = 351 ml
1. 6F → rated for up to 6 LPM → will have smaller reservoir 2. 8F→ratedforupto8LPM
ii. Medtronic Affinity Fusion = 260 ml
iii. Terumo FX15 = 144 ml

has an internal arterial filter
Exception –> medtronic affinity fusion does not have one because the membrane is wound up in such a way that the actual membrane itself is the filter … (has a slightly higher pressure drop)

Question 17

hemo concentrator

Answer 17

is an internal hollow fiber device –> blood runs on the inside of the fibers

–> a fluid removal device to control hemodilution; removes free plasma water and various inflammatory mediators

Question 18

heat -exchangers

Answer 18

Counter-current flow is best for heat exchange and gas exchange → 100% efficiency
i. Concurrent only gives 50% efficiency

Heat exchange efficiency of an oxygenator is rated at the top flow of the oxygenator in which gives you 50% heat transfer efficiency

i. The faster you flow the less heat exchange you’ll have bc you’re not in contact with the heat exchanger → convection can’t happen
ii. All heat exchangers are rated at 50% efficiency

Question 19

internal heat exchangers

Answer 19

i. Typically the heat exchanger is integral to the oxygenator, sometimes it is external
ii. Integral Heat Exchanger:
1. Less efficient → takes a longer time to heat the blood furthest from the
heat exchanger
2. Heat exchanger is made of plastic
3. sometimes heater-cooler connections are directional, depending on the oxygenator

Question 20

external heat exchanger

Answer 20

1. More efficient → blood moves through the heat exchanger first before
   moving through the fiber bundle
2. Heat exchanger is made of stainless steel
3. Requires an external arterial filter
4. Ex: Medtronic Affinity NT oxygenator

Question 21

Pressure drop of oxygenator

Answer 21

At top flow pressure drop max should be 100-150 mmHg

inlet pressure - outlet pressure

Question 22

O2 transfer rate

Answer 22

is typically 300-400 ml/min for adult oxygenators

i. If venous blood is 75% O2 saturation you’ll transfer at least 300-400 ml/min of O2

ii. After anesthesia and hypothermia, pt might only need 150 ml/min of O2

iii. Anesthesia decreases O2 requirement by 25%
1. Ex: if pt’s O2 requirement is 400 ml/min, after anesthesia it is now 300 ml/min

iv. for every degree that you cool body temperature there is a decrease in O2
requirement by 7%
1. Ex: you cool the pt 5 degrees → decreases O2 requirement by 35% → starting at 300 ml/min, now the pt’s O2 requirement is 195 ml/min
.35 x 300 =105
300-105 =195

Question 23

Decoupling

Answer 23

when the centrifugal head is not properly aligned with the magnet in the motor → lower the RPM and the magnets will catch

Question 24

Purge lines on oxygenator

Answer 24

1) Pre-filter purge line –> blood goes directly to cardiotomy incase there is any air in the blood
2) post filter purge line –> after the arterial filter
–> measures blood gas after oxygenator
–> deliver medications
3) purge line that goes to the manifold
–> the 1st port on the manifold should always be where you’re drawing lab
samples so it is NOT contaminated by any drugs

Question 25

Internal arterial filter

Answer 25

integrated in the oxygenator
- 30-32 microns
arterial filter is a screen type filter

the evolution from external to internal arterial filter helped decrease priming volume

Question 26

external arterial filter

Answer 26

30-40 microns
pleated screen filter - 1 filter medium (unlike the fepth filter ina cardiotomy that has multiple filter mediums)

blood flow enters the top of the filter and exits from the bottom of the screen filter to allow air to escape at the top of the filter

hydrostatic pressure forces air up out of the filter and into the carditomy

external arterial filters should always be place higher than the oxygenator

Question 27

pre bypass filter

Answer 27

0.2 microns
must remove pre-bypass filter before going on bypass b/c bloos is 7-8 microns and is NOT able to pass through the pre-bypass filter

• used to remove all particles out of the priming solution
• attaches to venous line prior to reservoirs
  –> sometimes its incorporated into the A-V loop in the pack

not all institutes used a pre-bypass filter bc they’re 400-500 dollars

Question 28

CO@ prime:

Answer 28

Flush circuit with 100% CO2
a. CO2 is heavier than N2 and displaces the room air (and all the N2) in the circuit

b. Removes N2 gas from the circuit

c. CO2 is 30x MORE soluble than N2 gas

d. CO2 prime helps remove gas bubbles from the circuit once it is primed

e. Path: attach gas line w/ filter (green tubing) to the stopcock in the venous line → A-V loop
(venous to arterial) → arterial filter → oxygenator → centrifugal head → reservoir → leave through the vacuum port

Question 29

heater-cooler check

Answer 29

a) Checking for a water to blood leak

b) Heat exchanger is in the middle of the oxygenator and the hollow fibers surround it

c) Water circulates in the heater cooler

d) If the heat exchanger has a leak water will leak into the fibers where the gas is flowing through → this will sound like a percolator (air going through water)

e) Must check this before priming the pump so you can hear the leak if there is one
i. If you turn the heater-cooler on after you prime the pump then a sign of a heater-cooler leak will be an increase in circuit volume

Question 30

Prime circuit

Answer 30

a) Always prime circuit when you’re warm → because gas is more soluble in colder liquids than in warmer liquids → if you remove all the air bubbles when you’re warm then any remaining missed bubbles will dissolve when you’re cold

b) Always prime circuit after turning on heater-cooler:
i. If you prime your circuit before turning the heater cooler on then there will be a large temperature gradient and air bubbles will leave solution that you now have to try to remove

1. Large temp gradient going from room temperature to body temperature: going from 20°C to 37°C
2. Ideal temperature gradient is 8°C

Question 31

In an emergency, what should you setup first?

Answer 31

Always set up pump-oxygenator circut first, this is all you need to keep someone alive

–> ancillary equipment (CPG, vent) can be set up after

Question 32

whats the order of priming/checks?

Answer 32

1. CO2 prime
2. heater-cooler check
3. prime circuit