Cardiac Surgery Concepts Flashcards
Lance Carter, AA-C
What are the basic steps of a CABG?
- Blood vessel(s) from the body are removed (harvested)
- The harvested vessels (grafts) are sewn proximal and distal to an atherosclerotic coronary artery
- Blood now flows through the harvested vessel and “bypasses” the blocked coronary artery
In a CABG, where is the proximal anastomosis?
Aorta
In a CABG, the distal anastamosis is ________ to the blockage?
distal
Are the distal or proximal anastamoses sewn first?
Distal, because there are less proximal to do and it ensures that the anastomose is correctly placed. Usually, when the surgeon is done with the distal anastomoses the surgery is about to be finished.
What is the most commonly used graft, especially in the LAD?
When is a percutaneous coronary intervention (PCI) indicated?
Cardiac stenting is a much less invasive procedure is an alternative to coronary artery bypass grafting, and it used for less severe cases of coronary artery disease
What are the two different types of stents commonly used?
What is in cardioplegic solution?
Cardioplegia is a potassium rich solution that can also contain many different additives, such as glucose, magnesium, calcium, bicarb, buffers, and free radical scavengers (Mannitol)
What is a surgery where cardiopulmonary bypass would be needed?
Traditional open valve replacement
Coronary bypass procedures
How does cardiopulmonary bypass work?
- De-oxygenated blood is drawn away from the heart through a “venous cannula”
- The venous blood is stored in a venous reservoir (holding tank…)
- The venous blood is sent through a oxygenator, heat exchanger, and arterial filter
4/5. The oxygenated blood is reinfused into the body via a “main pump” (4) that pumps the blood into the aorta through an “arterial cannula” (5)
- An aortic cross clamp is usually placed on the ascending aorta in order to:
What are the main components of the bypass machine?
What is the most common method for removing deoxygenated blood from the patient during bypass?
Placing the venous cannula in the right atrium is the most common method for removing deoxygenated blood from the patient during cardiac bypass
When could you not use a right atrial cannula?
Where are the venous cannulas placed during a right heart surgery?
Can you place a venous cannula in the right atrium without opening the chest?
Yes, you can thread it through the femoral vein; likewise for the femoral artery
What are the two main purposes for the venous reservoir?
- The venous cannula can remove any air that inadvertently enters the venous drainage line
- It also stores a surplus of blood in the bypass circuit
As much as _____L of blood may need to be translocated from the patient to the ECC when full CPB begins
1-3 L
The “main pump” pumps blood to the body via the arterial cannula, and it has the option of pulsatile flow or non-pulsatile flow. Since 2016, which one is more common?
Non-pulsatile
Pulsatile flow is a newer technique (is less common as of 2016), and is possible with a “_____” pump, or a “________” pump
“Roller pump” or “Diagonal pump”
What is the advantage to pulsatile flow?
It is more physiological, so perfusion is often better
What are disadvantages to pulsatile flow?
- “Achieving pulsatile flow from a noncompliant high resistance CPB circuit is difficult”
- “The higher flows and resultant shear stresses necessary to obtain an efficient pulsatile flow are a disadvantage to the technique, because they can result in more damage to blood elements”
What is the function of the heat exchanger?
Modest hypothermia is around ___°C
34°C
What are advantages to modest hypothermia?
- *1. Decreases oxygen requirements** (Clinical Anesthesia in Neurosurgery, 2nd edition, page 34)
- A decrease in body temperature 1°C decreases cerebral O2 consumption by 5%
- A decrease in body temperature 10°C decreases cerebral O2 consumption by 50%
- *2. Decreases anesthetic requirements**
- Hypothermia acts as anesthetic
What are disadvantages to modest hypothermia?
- More likely coagulopathy (increases bleeding)
- Increased blood viscosity, which can decrease perfusion
Three main functions of the oxygenator?
- Oxygenates the blood (Cardiac Anesthesia: Principles and Clinical Practice, 2ndedition, page 353)
- Removes CO2 (Cardiac Anesthesia: Principles and Clinical Practice, 2ndedition, page 353)
- This is also the site of volatile agent entry into the bypass machine
- Therefore, the perfusionist controls the volatile agent concentration while the patient is on bypass
What are the two types of oxygenators?
- *1. Bubble oxygenator**
- More simple & lower cost
- More trauma to the blood
- Rarely used in the current era
- *2. Membrane oxygenator**
- Less blood trauma
- Increased complexity and cost
- The standard oxygenator used today
What is the disadvantage to the oxygenator?
- Damages the blood
- Increases leukocyte activation, inflammatory response, and organ dysfunction
- Decrease in circulating WBC and platelets, and increases pulmonary artery pressure
What is the purpose of the arterial filter?
The arterial filter removes fat globules & air bubbles from the bypass circuit
What is the purpose of an ultrafilter?
“A hemoconcentrator (ultrafilter) is sometimes added to the circuit to remove excess water and electrolytes from the circulating volume, thus concentrating the blood in a patient with an undesirably low hematocrit.”
What are the two types of suction used in cardiopulmonary bypass?
- Standard (“regular” operating room suction)
- “Blood salvage” suction
What are the three types of blood salvage suction in cardiac surgery?
- Cardiotomy suction
- Cell saver suction
- Left ventricular vent
Cardiotomy advantage is?
- Cardiotomy suction is whole blood, which includes clotting factors, platelets, and PRBCs!
Disadvantages to cardiotomy?
- The blood going through cardiotomy suction is damaged by the bypass machine, and therefore cardiotomy suction use is associated with a more pronounced systemic inflammatory response (and resulting coagulopathy)
What are the steps to cell saver?
- With cell saver, the suctioned blood from the field is washed & then centrifuged, which separates RBCs from the plasma, platelets and particulate matter
- The RBC’s are then moved to an infusion bag and transfused back to the patient
What is the hematocrit level of cell saver blood?
The hematocrit of cell saver blood is ≈ 50-70%
Advantages to cell saver technique?
- Particles such as fat, air, and tissue are also filtered out of the blood
- And since this blood does not run through the bypass machine, it is “less damaged” when it gets returned to the patient
Disadvantages to cell saver?
- It is not whole blood (contains mostly PRBCs)
- It takes longer before it can be reinfused into the patient
Purpose of the left ventricular vent?
It removes all of the venous blood that was not picked up by the venous reservoir (blood that comes from the bronchial and Thebesian veins) and returns it to the venous reservoir, thus preventing left ventricular distention.
Concern is air entrapment
Heart surgery suction summary
What is the most common way of arresting the heart during bypass?
Antegrade Cardioplegia
Cardioplegia soln is injected into the coronary arteries through the coronary ostia (coronary os)
What keeps the cardioplegia solution from washing out into the body?
A cross clamp on the ascending aorta is necessary to prevent the CP from washing out into the body (keeps the CP in the heart)
A less common way of cannulating antegrade cardioplegia solution is by direct cannulation of the _______________.
coronary os
Cardioplegia lines are the only way the heart can get sufficient oxygen in cases where:
- An ascending aortic cross clamp must be placed
- The heart needs to be arrested
Retrograde cardioplegia is defined as
Cardioplegia being injected retrograde through the coronary sinus
In order to prevent coronary sinus damage, the anesthetist and surgeon will measure the pressure within the coronary sinus as cardioplegia is injected
How does the anesthetist monitor pressure with retrograde cardioplegia?
- The surgeon throws sterile, non-compliant tubing over the drape
- This tubing is connected to the retrograde CP line on the surgical field - The anesthetist hooks this tubing up to either the CVP or PAP stopcock on the triple transducer
- Either one is fine, since CVP and PAP don’t need to be measured during bypass
- In this picture, I hooked up the retrograde line to the CVP transducer
How do you coordinate with the surgeon in order to monitor retrograde cardioplegia during injection?
During the arrest portion of the surgery, which direction would you want the stopcock to be facing when connected to the retrograde cardioplegia line?
- During the phase when the heart is arrested, the stopcock at that transducer will be turned off to the patient, and open to the retrograde line
–In other words, the anesthetist will not be able to simultaneously monitor CVP when the surgeon is monitoring retrograde cardioplegia
What could be monitored in this picture?
When the stopcock is to the side (normal position), CVP/PAP can be monitored
What can be monitored in this picture?
When the stopcock is up (toward the patient), retrograde cardioplegia pressure can be monitored
What are indications for retrograde cardioplegia?
- Retrograde cardioplegia helps arrest areas of the heart distal to high grade obstructions
- It helps arrest the heart in situations where antegrade CP would easily wash out (i.e., when the ascending aorta is opened)
- Ascending aorta repair
- Open aortic valve repair
Which picture is the correct placement of the aortic crossclamp?
As illustrated by the pictures to the left, another reason that the clamp has to be placed PROXIMAL to the arterial cannula is that it is the only way that perfusion to the head and the rest of the body is possible!
If a cross clamp will be used to initiate cardiopulmonary bypass, it has to be placed on the _____________.
ascending aorta
The sequence for arresting the heart and going on bypass is?
- Drain the blood from the heart via the venous cannula
- Place the aortic cross clamp (while the heart is still beating)
- THEN arrest the heart by injecting cardioplegia
The heart can be arrested without a clamp, if the surgeon does what?
- Uses retrograde cardioplegia
- Directly cannulates the coronary arteries for cardioplegia
What are advantages to the aortic crossclamp? (3)
What are disadvantages to the aortic crossclamp? (2)
-
Physiologic perfusion to the heart is not possible
- Therefore, the heart gets perfused with the bypass machine through the cardioplegia cannulas (which is usually non-pulsatile) - The cross clamp increases the risk of stroke from a possible dislodging of emboli
What are the two ways for a graft to be sewn into the aorta?
When is cardiopulmonary bypass necessary, and what are the advantages (2)?
What are the main disadvantages to CPBP? (7)
- The priming fluid causes hemodilution (Hct decreases)
- An aortic cross clamp is usually placed, which can lead to possible dislodging of fat emboli
- There may be possible difficulty coming off pump
- Pulmonary complications are more likely
- Tissue perfusion is less effective (and it is usually non-pulsatile)
- The patient’s blood gets damaged by the bypass machine
- Large volume shifts can occur, with possible transient cerebral edema
What happens when a patients blood is damaged by the CPBP machine?
What is the difference between “open” and “closed” bypass machines?
The collapsible-bagconfiguration is often referred to as a “______” system, in that the blood volume in the bag is not exposed to room air surrounding the device
closed
The hardshell-reservoir configuration is often referred to as an“____”system, since the blood in the reservoir is exposed to air surrounding the device…”
open
Is the primary system used today open or closed bypass? Why, what is the advantage?
What are advantages to clsoed bypass systems? (3)
What are disadvantages to closed bypass? (3)
What are the components of the Mini-Cardiopulmonary Bypass Circuit? What does it not have compared to a normal bypass circuit?
What is the priming fluid volume of mini-ECC?
600mL
Advantages of Mini-Cardiopulmonary Bypass? (4)
- All the advantages of a “closed” bypass system
- Some studies show that it improves myocardial protection
- Is associated with less blood transfusion
- Has been associated with earlier recovery times and reduced ICU and total hospitalization time
What are disadvantages of Mini-Cardiopulmonary Bypass? (2)
What are some possible risks associated with doing a heart surgery “off-pump”?
Explain partial cardiopulmonary bypass
Why the heck would we consider partial CPB?
What are Implications of Partial Cardiopulmonary Bypass? (3)
Explain Left Heart Partial Bypass
What are other implications of a Left Heart Partial Bypass? (3)
Indication for Left Heart Partial Bypass?
Left heart bypass can be used for open descending thoracic aortic aneurysm repair
How the eff you gonna perfuse the body if you need to cross clamp the descending aorta?
Left Heart Bypass advantages? (5)
- The heart stays beating (is not arrested) and thus doesn’t need to be restarted
- The lower circuit prime volume (due to the absence of an oxygenator & heat exchanger & reservoir)
- There is a lower chance of postoperative renal failure (4% incidence with left heart bypass (compared with 9 and 11% with simple cross-clamping and CPB, respectively)
- The blood pressure can be controlled by the perfusionist
- There is no direct blood-air contact in the circuit, which means there is less blood damage
The lower circuit prime volume (due to the absence of an oxygenator & heat exchanger & reservoir) leads to: (3)
What is the target ACT?
Disadvantages to Left Heart Bypass? (3)
Explain Right Heart Bypass
What are two implications of Right Heart Bypass?
What are indications for Partial Right Heart Bypass? (3)
Right Heart Bypass Advantages & Disadvantages
In situations where total body perfusion isn’t feasible with the arterial cannula due to the location of the clamp, there are three options to protect the brain while the operation is completed:
What is Deep Hypothermic Circulatory Arrest (DHCA)?
What are indications for circulatory arrest?
How the circulatory arrest process works?
- The patient is put on cardiopulmonary bypass
- The heat exchanger from the bypass machine profoundly decreases patient’s temperature
- The heart is arrested, and circulation through the bypass machine is slowed to a near standstill
- The profound decrease in oxygen consumption allows the patient to survive the operation with minimal blood flowing through the body
What is the typical target temperature for circulatory arrest?
The BIS monitor and the EEG can be used to monitor the depth of hypothermia and ensure electrical silence during DHCA, what temperature is the EEG isoelectric? What temperature technique would you use?
How long is circulatory arrest safe?
15-20ºC (nasopharyngeal)
How long is circulatory arrest safe? Can adults or neonates/children sustain circulatory arrest longer?
What are complications to DHCA?
- Any of complications of hypothermia in general
- Potential neurologic complications
- Potential neurologic complications from cooling the patient too rapidly or rewarming the patient too rapidly
DHCA Anesthetic Management (2)
- Use of a nasal temperature probe (should be used in all DHCA cases)
- Additional brain protection (hyperoxygenation before DHCA, allowing at least 20 minutes of cooling to ensure adequate cerebral protection, packing the head in ice, [and] intermittent cerebral perfusion between 15 and 20 minute periods of DHCA )
What is Retrograde Cerebral Perfusion During Circulatory Arrest?
What is Normothermic Antegrade Cerebral Perfusion?
What is Antegrade Cerebral Perfusion?
What is Cerebral Oximetry?
How do you read a Cerebral Oximeter, and what are normal values?
What is the value of rSO2?
Name some Applications For Cerebral Oximetry
- Heart surgery
- Sitting/beach chair position surgery
When should an anesthetist intervene with cerebral oximetery?
What are Factors That Can Decrease rSO2 Values? (4)
What are Ways To Increase Cerebral SpO2? (6)
- Increase cerebral perfusion pressure (MAP-ICP)
- Fluids/pressors/trendelenburg
- Mannitol administration
- Placement of lumbar drain - Increase cerebral blood flow (cerebral dilation)
- Decrease minute ventilation
- NTG? - Increase FiO2
- Increase cardiac output
- Increase hematocrit
- Decrease cerebral metabolism
- Increase anesthetic or decrease temperature
What is PT time and normal values?
What is PTT time and normal values?
Intrinsic NOT extrinsic
What is INR and normal range?
What does INR standardize?
What is the standard heparin, how does it work, and what pathway does it inhibit? How do you reverse it?
Does heparin affect PT, PTT, or INR more?
What is different about low molecular weight (fractionated) heparin or Lovenox (enoxaparin)?
Does Coumadin (Warfarin) affect extrinsic or intrinsic pathway more? How can you reverse it? (2)
What is plavix? Can it be reversed?
If a patient is on dual anti-platelet therapy, how should you proceed?
–At least 14 days if the patient just had a balloon angioplasty
–At least 6 weeks if the patient had a regular metal stent placed
–At least a year if the patient had a drug-eluting stent placed
What is Xarelto?
What is Eliquis?
What is the standard heparin dose for a CABG?
What is Heparin Induced Thrombocytopenia (HIT)?
What do you use in a surgery if someone has a history of HIT?
In patients with HIT, direct thrombin inhibitors [ex: Argatroban] are used for anticoagulation in cardiac surgery instead of heparin
What are considerations of Antithrombin III Deficiency?
How do Manage anesthesia of Antithrombin III Deficiency?
What is the reversal/dose for heparin?
What is the mechanism of protamine?
What are Adverse Effects of Protamine?
What reverses the effect of warfarin?
What are Prothrombin Complex Concentrates (PCC)? What are they an alternative to?
PCC is concentrated extract from fresh-frozen plasma (factors are at 25 fold higher concentration than FFP)
–Each vial contains the same amount of Factor IX that would be found in 2 units of FFP
What are the Advantages & Disadvantages Of PCC?
