CBP + IABP Flashcards
For what main two surgeries do we use CPB?
CABG and cardiac valve repair
Name the three essential functions performed by CPB:
1) Oxygenation of venous blood
2) Elimination of CO2
3) Maintenance of system perfusion
ECC stands for:
Extracorporeal circulation
Explain what CPB is.
A form of ECC in which the patient’s blood is rerouted outside the vascular system and the function of the heart, the lungs, and to a lesser extent the kidneys is temporarily assumed by surrogate technology
CPB has five physical components. What are they?
1) Blood reservoir
2) Oxygenators/ gas exchangers
3) Pumps
4) Heat exchangers
5) Filters
DHCA stands for?
Deep Hypothermic Circulatory Arrest = 18 *C
Normally, heat exchangers in CPB cool the body to:
30 *C
What is it called when you use heat exchangers in hypothermia to cool the body down to 18 *C?
Deep Hypothermic Circulatory Arrest
Blood reservoirs, Filters, Heat exchangers, pumps. What is missing from that list?
Oxygenators/gas exchangers
Oxygenators/gas exchangers, pumps, heat exchangers, filters. What is missing from that list?
Blood reservoir
How many cannulas are necessary to provide CPB?
2
Where is/are the CPB cannula(s) located?
One cannula is located in the right atrium–it provides venous drainage to the ECC.
Another arterial cannula placed in the ascending aorta allows arterial return to the patient from the ECC.
Under what circumstances who a surgeon perform CPB using a bicaval cannula?
For any procedure that required the isolation of the right ventricle or atrium
T/F: The majority of cardiac procedures are performed with venous cannulation through the right atrium, with a single two-stage cannula.
True
The majority of cardiac procedures are performed with venous cannulation through the right atrium using a:
single two-stage cannula
Single cannulation of the atria is also known as:
Cavoatrial
Which cannulation procedure allows complete CPB?
Bicaval
In two-vessel cannulation of the RA, the drainage holes are placed:
in the SVC and the IVC
The single “two-stage” cannula in CPB refers to the fact that:
The cannula has two sets of drainage holes: one in the right atrium and one in the IVC. This method bypasses the SVC entirely.
Which venous cannulation method includes the SVC?
Bicaval
Cardioplegia involves what two solutions?
A high-K+ containing crystalloid cardioplegia solution or a low-K+ containing crystalloid cardioplegia solution
Is cardioplegia solution crystalloid or colloid?
Crystalloid
By what means is perfusion of cardioplegia possible?
Antegrade through the coronary arteries or retrograde through a catheter in the coronary sinus
If cardioplegia flows antegrade, it does so via:
Coronary arteries
If cardioplegia flows retrograde, it does so via:
a catheter coronary sinus
When you think antegrade cardioplegia, think:
coronary arteries
When you think retrograde cardioplegia, think:
coronary sinus
When and where is the retrograde catheter for cardioplegia normally placed?
It is normally placed prior to CPB through the atrial wall to the coronary sinus.
Cardioplegia literally translates to:
Paralysis of the heart
T/F: the venous reservoir, heat exchanger, and oxygenator are all combined in one integrated, disposable unit.
True
What aspects of the CPB machine are all integrated as a single disposable unit?
Venous reservoir
Heat exchanger
Oxygenator
What mechanism is used to prevent LV distension due to high volume of return to the LV?
An LV vent and a roller pump
Why is it important that both heat exchanger and gas exchanger portions of the membrane lung contain manifolds that distribute blood flow evenly?
It minimizes the blood pressure drop at clinical flow rates.
Primary function of the small tubules in the gas exchanger?
Eliminates CO2 from blood
What controls the FiO2 delivered to the membrane oxygenator and therefore controls the oxygen partial pressure gradient between the gas and blood phases? Why is that significant?
An air-oxygen blender
In doing so, it alters the total amount of oxygen transfer by diffusion through the membrane, ultimately determining PaO2
In CPB, arterial PaO2 is independently controlled by:
gas flow (L/min) through the oxygenator (AKA sweep rate)
T/F: lower gas flow rates remove more CO2 from inner membrane surface than higher do.
False; higher remove more CO2 from the inner membrane surface.
What effects does removing CO2 form the inner membrane surface of the oxygenator have on PaCO2?
It decreases it because it establishes a diffusion gradient from the blood to the inside of the membrane.
By what means does an oxygenator encourage the removal of CO2 from blood?
High flows remove CO2 from the inner membrane of the oxygenator, creating a diffusion gradient by which CO2 tends to flow from higher concentration to lower concentration (blood to filter).
Might CPB circuits contain anesthetic vaporizors?
Yes.
What ultimately controls PaCO2?
Flow rate (sweep rate) of non-CO2 containing gases
What is lung surface area?
70m2
What is the surface area of current membranes in CPB filters?
2-4 m2
How do membranes of CPB filters compensate for the fact that they have significantly lower surface areas than the human lung?
Via increased contact or transit time of the blood with the membrane
What two types of pumps would you see on CPB?
Centrifugal pumps
Roller pump
Impeller
What type of blood flow does centrifugal pumps produce?
Semi-pulsatile (sinusoidal) blood flow
What type of blood flow does roller pumps produce?
Propels blood forward using surface tension of blood
Centrifugal pumps are primarily used for what type of bypass?
Venovenous bypass
Which is superior at generating pulsatile flow, roller pumps or centrifugal pumps?
Roller pumps
Which pump is dependent on afterload?
Centrifugal pumps. Roller pumps are independent of afterload.
Which type of pump is more likely to cause trauma to bypass tubing, roller or centrifugal?
Roller pumps
If the power goes out, which type of pump can you hand crank?
Roller pumps
Which type of pump is capable of reverse flow, roller or centrifugal?
Centrifugal
Which type of pump involves an increased risk of air embolism?
Roller pump
Where are some areas of CPB that filters are located?
Blood reservoir Priming fluids Blood from blood bank Cardioplegia Between oxygen and oxygenator Arterial filter for gas exchange
T/F: Patient’s lungs are considered a filter.
True
T/F: Hypothermia further causes complications during cerebral ischemia.
False; hyperthermia does
What are some benefits to hypothermia during cerebral ischemia?
Favorable balance between O2 supply and demand
Decrease in excitotoxic NT release
Decrease in BBB permeability
Decreased inflammatory response
What are some harms regarding hyperthermia during cerebral ischemia?
Imbalance between O2 supply and demand
Increases excitotoxic NT release
Increased BBB permeability
Increased inflammatory response, free radical production, intracellular acidosis; destabilized cytoskeleton
What is the characteristic EKG change during hypothermia?
Osborn wave; J-wave
Where do J-waves appear on the EKG?
It is a positive deflection at the junction of the QRS complex and the initial portion of the ST-segment.
What do J-waves signify?
Hypothermia
Where are J-waves most prominently seen?
In mid-precordial leads and inferior leads
What are the seven principle things to monitor during CPB?
1) ECG
2) BP: ONLY MAP during ECC from A-line or transducer in bypass circuit
3) Blood volume/flow: look to CVP
4) Oximetry: flow is non-pulsatile, so oximetry isn’t great
5) Temperature
6) Urine output
7) ETCO2: during periods of lung ventilation
What types of oximetry do we monitor during CPB?
Cerebral (rSO2), MvO2, Tissue (StO2)
What temperature measurement should we get during CPB?
Core: nasopharynx, rectal, bladder, etc.
During full CPB, does CVP rise or fall?
Falls to 0.
During full CPB, does pump flow rise or fall?
Rises to peak at full CPB.
Which measurement of temperature cools and rewarms most rapidly during CPB?
Esophageal, followed by nasopharynx; best to measure rectal and bladder as well
If you have to identify the different rates of temperature return on different parts of the body, the open circles represent:
Nasopharynx
If you have to identify the different rates of temperature return on different parts of the body, the solid circles represent:
Esophageal
If you have to identify the different rates of temperature return on different parts of the body, the solid triangles represent:
Bladder
Does coming off of bypass leave patients warmer or colder than they were at baseline?
Warmer
What type of bypass for a supracommissural bypass in the aorta?
LHB
What type of bypass for a hemiarch replacement in the aorta?
LHB
What type of bypass for a total arch replacement in the aorta?
LHB
What type of bypass for a trifurcated graft in the aorta/aortic arteries?
LHB
What type of bypass for a frozen elephant trunk surgery in the aorta?
LHB
Simple LHB involves:
LA –> cone –> femoral artery
Complex LHB involves:
Oxygenator, heat exchanger, reservoir, pump
What is purpose of VV ECMO?
Supplies O2
What is the purpose of VA ECMO?
Oxygenation + increases pressures
What does ECMO stand for?
Extracorporeal membrane oxygenation
Two primary indications for ECMO?
Respiratory failure + cardiac failure
Two major differences between CPB and ECMO?
Site of cannulation
Lack of venous reservoir in ECMO
Structurally speaking, what are the three primary ways that CPB and ECMO are similar?
They both include a cannula, a pump, and a gas exchange unit
Most common sites of venous cannulation in ECMO?
Femoral or jugular
Pumps used in ECMO?
Centrifugal or roller pumps
What type of ECMO support is most common in respiratory failure patients?
Venovenous (VV)
Drainage site in VV ECMO?
Return site in VV ECMO?
Drainage site = right IJ
Return site = femoral vein
Normal flow rate in VV ECMO?
80-100 mL/kg/min
Most common type of ECMO for patients with cardiopulmonary failure?
Venoarterial (VA)
Venous cannulation sites in VA ECMO?
Femoral vein
Jugular vein
Atrium
Fast entry ECMO?
PaO2 < 50 mmHg for > 2 hours at FiO2 = 1.0
PEEP > 5 cmH2O
Slow entry ECMO?
PaO2 < 50 mmHg for > 12 hours at FiO2 = 0.6
PEEP > 5 cmH2O
Diameter of cannula using during VV ECMO?
13F
By what means is oxygenated blood returned to the body in VV ECMO?
IJV
By what means is oxygenated blood returned to the body in VA ECMO?
Femoral artery
IABP stands for:
Intra-aortic balloon pump
When does inflation of IABP occur? Result?
Balloon inflation occurs early in diastole and results in an increase in diastolic pressure and improvement in cerebral and coronary blood flows
Why are IABPs beneficial?
Their inflation in late diastole causes an increase in diastolic pressure, improving cerebral and coronary blood flows
Result of balloon deflation prior to ventricular systole?
It enhances left ventricular ejection.
When does the IABP deflate?
Just prior to ventricular systole
Effect of balloon deflation of LV ejection?
Enhances it
Pathway of IABP insertion?
A catheter is inserted via femoral artery to the iliac artery. Once inserted, a balloon with a radiopaque marker continues the trip up the descending thoracic aorta and into the subclavian artery.
How large is the catheter used to insert an IABP?
14-18 French
Primary means by which we correctly position IABPs?
Via guidewire
Diameter of IABP?
7.5 French
An IABP has two lumens: name them. Which is larger?
The helium lumen is much larger than the blood lumen.
Volume of IABP?
20-30 ml
What mechanism allows post-insertion adjustment of the catheter position?
Sterile plastic sheath
What portion of an IABP sits between the balloon and the sutures?
Internal catheter
What triggers inflation of IABP with He?
It can trigger off of any waveform with a dicrotic notch (EKG/A-line), but preferably, it triggers off the EKG.
What are the two principle contraindications to IABP counterpulsations?
1) Aortic valvular insufficiency
2) Aortic disease, such as a dissection or an aneurysm
What is the benefit to He as a drive gas in IABP?
Its low density causes rapid inflation.
In what circumstances would inflation of IABP balloon cause aortic distension?
If the balloon were too large
Effect of IABP on coronary perfusion?
Increases it by increasing DBP
Effect of IABP on afterload in the LV?
Decreases it by decreasing aortic diastolic pressure
Effect of IABP on LVEDP + PCWP?
Decreases it
Effect of IABP on CO + EF?
Increases it
Effect of IABP on HR?
Decreases it
During systole, is the IABP balloon inflated or deflated? Effects?
Deflated
Increased CO, decreased afterload, decreased cardiac work, decreased myocardial O2 consumption
During diastole, is the IABP balloon inflated or deflated? Effects?
Inflated
Augmentation of diastolic pressure
Increased coronary perfusion
If balloon inflation occurred later in diastole, how would the pressure that balloon generates be different?
It would be lower because the amount of blood in the aorta would not be maximal. A non-maximal amount naturally generates lower amounts of pressure when it is displaced than maximal amounts do.
How does IABP inflation affect coronary collateral circulation?
It is potentially increased from the increased CPP.
How does IABP inflation affect systemic perfusion pressure?
Increased
By what means does IABP deflation decrease myocardial oxygen requirements?
The IVC phase is shortened and afterload is decreased.
Effect of IABP balloon deflation on peak pressures during systole?
They decrease
Effect of IABP balloon deflation on SV?
There is reduced afterload that allows the LV to empty much more effectively, so SV is increased.
IVC =
isovolemic contraction
What point on the EKG triggers balloon inflation?
Midpoint of the T-wave
What point of the EKG triggers balloon deflation?
Peak of the R-wave
Under what circumstances would the dicrotic notch on an A-line be apparent before diastolic augmentation?
The inflation of the balloon occured after the AV valve closed (too late).
Main physiological effect of late balloon closure?
Sub-optimal coronary artery perfusion
T/F: compartment syndrome is a vascular risk of IABP.
True
Which artery specifically risks occlusion w/ IABP?
Left internal mammary artery
What type of VAD is a MicroMed DeBakey VAD?
Axial flow device
The Jarvik 2000 VAD is distinguishable because of its
belt.
In the TandemHeart VAD, which pump is inside the body? Which is taped to the thigh?
LVAD is inside the body, RVAD is taped to the thigh.
VAD patients who can’t use a BP cuff d/t lack of pulsatile flow?
HeartMate II
What is the definining characteristic of a VAD?
Prosthetic LV
Describe the parts of a total artificial heart.
Wireless energy transfer system External battery pack Internal battery Controller Replacement heart
Do total artificial hearts generate pulsatile blood flow?
Yes, somewhat.
Which has a higher rate of infection, TAH or BiVAD?
TAH
Which has a higher rate of success as a bridge to transplantation, TAH or BiVAD?
TAH (90 days vs. 30 days length of support, 3x longer)
Which lowers incidence of stroke, BiVAD or TAH?
TAH
Which is more likely to require reoperation, BiVAD or TAH?
BiVAD
