Cardiac Surgery Concepts Flashcards
the name of the procedure that restores normal blood flow to an area of the heart by creating new routes around obstructive coronary arteries
coronary artery bypass graft (CABG)
what are the 3 blood vessels that can be harvested from the body for a CABG?
- Left internal mammary artery (LIMA)
- saphenous vein
- radial artery
Where is the graft for the CABG sewn in relationship to the atherosclerotic coronary artery?
Proximal and distal to the atherosclerotic coronary artery
Where is the proximal anastomosis of the CABG graft located?
on the aorta
Where is the distal anastomosis of the CABG graft located?
on the coronary artery; distal to the obstruction
in a triple bypass, how many distal anastomoses and proximal anastomoses will there be?
3 distal and one proximal
in a CABG, the amount of distal anastomoses will always be _____ (higher/lower) than the amount of proximal anastomoses
higher
in a CABG procedure, which anastomoses does the surgeon usually sew on first?
proximal or distal
distal; so when the surgeon is done sewing the distal anastomoses the procedure will be done soon because there are usually less proximals to do
which vessel is the most commonly used graft for CABG?
LIMA ( Left Internal Mammary Artery)
Which vessel is the LIMA most commonly anastomosed with?
LAD ( left anterior descending)
During CABG (arterial/venous) grafts are preferred over (arterial/venous) grafts.
Why?
arterial
venous
- the grafted vessel has to carry arterial blood and not venous blood
-coronary arterial pressure will damage the saphenous endothelium more quickly
LIMA patency rates are 90%, saphenous patency rates are 60%, and radial artery patency rates are lower than LIMA over a period of 10 years. Why does LIMA have the highest?
LIMA is a “live” graft which means that its proximal origin from the subclavian is left intact
What does the acronym PCI stand for?
Percutaneous Coronary Intervention
-Balloon Angioplasty and Cardiac Stenting
What procedure is used as an alternative to CABG, is less invasive, and is used for less severe cases of coronary artery disease?
Cardiac stenting
(CABG/Cardiac stenting) tends to show better 5 year survival and patency rates?
CABG
(CABG/ Cardiac stenting) carries a higher risk of stroke after 5 years
CABG
Newer stents are called “____- ______” stents
What do these stents do?
drug-eluting
-they slowly release a drug in order to slow the narrowing process
A cardiopulmonary bypass machine (CBM) functions as both the _____ and ______
heart
lungs
What are the 4 ways the cardiopulmonary bypass machine acts as the heart and lungs?
- drains deoxygenated blood from the body
- Oxygenates the blood
- Removes the CO2
- Pumps oxygenated blood back into the body
What are the 2 primary reasons a surgeon would use the cardiopulmonary bypass machine?
- Stop the heart
- so the surgeon can work on a heart that isn’t moving - Drain the blood out of the heart
- so the patient will not bleed out as the heart is opened
Name a surgery where the heart would need to be drained of blood and cardiopulmonary bypass would have to be used
open valve repair
Is it mandatory for the heart to be arrested during cardiac surgery?
no
-some operations do not require it, however surgeons will do it anyway because it is easier to operate on a non-moving target
Is it mandatory for the heart to be arrested during cardiopulmonary bypass?
no
-it is most common, however it is possible for the heart to remain beating
what solution do surgeons inject into the heart to arrest the heart?
Cardioplegia
What is Cardioplegia made up of?
potassium rich solution
-can contain additives such as glucose, magnesium, calcium, bicarb, buffers, and free radical scavengers ( mannitol)
What is another way cardioplegia can be administered
mixed and injected with blood
the most common way of arresting the heart is to inject cardioplegia into the _____ ______ through the ______ ______
coronary arteries coronary ostia (os)
When cardioplegia is injected into the coronary arteries, it is referred to as “_______ ______”
antegrade cardioplegia
most commonly antegrade cardioplegia is injected into the _____ ______
aortic root through a cardioplegia cannula
What is necessary to put on the ascending aorta during antegrade cardioplegia?
What is its purpose?
cross clamp
prevents the cardioplegia from washing out into the body and contains it in the heart
What is the least common method of antegrade cardioplegia?
direct cannulation of the coronary os (coronary artery)
The cross clamp keeps cardioplegia in the coronary arteries, but prevents the heart from being perfused.
How is the heart perfused while its arrested and has the cross clamp on it?
the cardioplegia cannula can also infuse blood into the coronary arteries so that the heart can receive oxygen
What is the only way the heart can get sufficient oxygen in cases where:
- the ascending aortic cross clamp must be placed
- the heart needs to be arrested
Cardioplegia cannula
the cardioplegia cannula provides sufficient oxygen to the heart in which two circumstances?
- the ascending aortic cross clamp must be placed
2. the heart needs to be arrested
Where is “retrograde” cardioplegia injected?
retrograde through the coronary sinus
when cardioplegia is injected through the coronary sinus it is referred to as “_____” cardioplegia
retrograde
Why does the surgeon have to be careful with pressure when injecting retrograde cardioplegia?
because the coronary sinus is a vein and is more likely to rupture
What does the AA do in order to prevent coronary sinus damage during retrograde cardioplegia?
measures the pressure within the coronary sinus as cardioplegia is injected via a non-compliant transducer tubing
What are the 3 steps of monitoring retrograde cardioplegia?
- surgeon throws over a sterile non-compliant tubing over the drape
- other end is connected to the retrograde cardioplegia line - The anesthetist hooks the other end of the tubing to either the CVP or PAP stopcock on the triple transducer
- When the heart is arrested, the stopcock will be turned on to the retrograde line
Are CVP and PAP monitored during bypass?
no
cannot simultaneously monitor retrograde cardioplegia and CVP/ PAP
When the heart Is arrested during retrograde cardioplegia, the stopcock at the transducer is turned (on/off) to the patient, and (on/off) to the retrograde line
off
on
When the stopcock is turned to the side (normal) during retrograde cardioplegia, what pressure is measured?
CVP and PAP
When the stopcock is up (to the patient) during retrograde cardioplegia, what pressure is been measured?
retrograde cardioplegia
List 2 indications for retrograde cardioplegia
- helps arrest areas of the heart distal to high grade obstructions
- helps arrest the heart in situations where antegrade cardioplegia would wash out
- when the ascending aorta is opened
- – ascending aorta repair
- –open aortic valve repair
The 6 steps of how the Cardiopulmonary Bypass Machine works
- De-oxygenated blood is drawn away from the heart using a venous cannula
- the venous blood is stored in a venous reservoir
- the venous blood is sent through an oxygenator, heat exchanger, and arterial filter
- oxygenated blood is re-infused into the body via a “main pump”
- the “main pump” pumps the blood into the aorta through an “arterial cannula”
- an aortic cross clamp is placed on the ascending aorta
how is deoxygenated blood drawn away from the heart on a cardiopulmonary bypass machine?
through a venous cannula
Where is the most common venous cannulation usually placed to drain blood away from the heart during cardiopulmonary bypass?
right atrium
Name the 3 other locations the venous cannula can be placed to draw blood away from the heart during cardiopulmonary bypass?
- SVC
- IVC
- femoral vein
What are the 2 purposes of the venous reservoir on the cardiopulmonary bypass machine?
- stores a surplus of blood
- 1 to 3 Liters
- serves as the circuits holding tank and acts as a buffer for imbalances between venous return and arterial flow - help to remove any air that entered the bypass circuit
what are the 4 purposes of the oxygenator, heat exchanger, and arterial filter on the cardiopulmonary bypass machine?
- fat globules/ air particles are filtered
- temperature of the blood is controlled
- the blood is oxygenated
- CO2 is removed
What are the 2 purposes for the aortic cross clamp during cardiopulmonary bypass?
- prevent blood from the arterial cannula from backing up into the heart
- allows the heart to stay arrested by keeping the injected cardioplegia in the heart
When is the only situation a right atrium venous cannulation would not work?
during right sided heart operations
-blood would gush out
if we need to do a traditional open right sided heart operation; where would the venous cannula be placed?
the inferior and superior vena cavas
where would the venous cannula be placed in situations where the chest does not need to be opened?
through the femoral vein and threaded up into the right atrium
Where would an arterial cannula be placed in situations where the chest does not need to be opened?
through the femoral artery and threaded into the aorta to perfuse the entire body
When cardiopulmonary bypass must be issued emergently, where should the venous and arterial cannulations be placed?
the femoral vein and artery
The _____ pump pumps blood to the body via the arterial cannula and has the option of pulsatile flow or non-pulsatile flow
main pump
This type of flow is more common through the main pump and uses a “centrifugal pump”
non-pulsatile
This type of flow is a newer technique and is less common through the main pump and uses a “roller” pump or “diagonal pump”
pulsatile
what type of pump does non-pulsatile flow through the main pump use?
centrifugal
what type of pump does pulsatile flow use through the main pump?
roller or diagonal pump
Two advantages of using pulsatile flow through the main pump
- better diastolic run-off
2. stimulation of the endothelium
Perfusion is (better/worse) with pulsatile flow through the main pump
better; more physiologic
2 disadvantages to pulsatile blood flow through the main pump
- achieving pulsatile flow through a non-compliant cardiopulmonary bypass machine is difficult
- high flows and shear stress can result in more damage to blood elements
This element of the cardiopulmonary bypass machine COOLS and HEATS the blood and allows the perfusionist to control the patient’s temperature during cardiopulmonary bypass
heat exchanger
what temperature is implemented while the patient is on cardiopulmonary bypass for organ protection?
modest hypothermia ~ 34 degrees Celsius
List 2 advantages of modest hypothermia during cardiopulmonary bypass
- decreases oxygen requirements
- decreases anesthetic requirements
- hypothermia acts as an anesthetic
a decrease in body temperature by 1 degree Celsius will decrease cerebral O2 consumption by _____%
5%
a decrease in body temperature by 10 degrees Celsius will decrease cerebral O2 consumption by _____%
50%
List 2 disadvantages to modest hypothermia during cardiopulmonary bypass
- increases the chances of coagulopathy
- increases the bleeding risk - increases blood viscosity, which can decrease perfusion
list the 3 functions of the oxygenator on the cardiopulmonary bypass machine
- oxygenates the blood
- removes CO2
- site of volatile agent into the bypass machine
- controlled by the perfusionist
List the 2 types of oxygenators
- Bubble oxygenator
2. membrane oxygenator
this type of oxygenator is more simple and is of lower cost
bubble oxygenator
this type of oxygenator causes more trauma to the blood
bubble oxygenator
this type of oxygenator is rarely used in the current era
bubble oxygenator
this type of oxygenator is associated with less blood trauma
membrane oxygenator
this type of oxygenator has increased complexity and is higher in cost
membrane oxygenator
this type of oxygenator is the standard used today
membrane oxygenator
what is the main problem with the oxygenator?
damages the blood
- leukocyte activation, inflammatory response, organ dysfunction
- decrease in circulating white blood cells and platelets and an increase in pulmonary artery pressure
What is the main function of the arterial filter in the cardiopulmonary bypass machine?
removes fat globules and air bubbles from the bypass circuit
what is the purpose of the ultrafilter on the cardiopulmonary bypass circuit?
aka hemoconcentrator, removes excess water and electrolytes from the circulating volume and concentrates the blood in a patient with a low hematocrit
List the two types of suction used in cardiopulmonary bypass
- Standard
- regular operating room suction - Blood salvage
List the 3 types of blood salvage suction used in cardiopulmonary bypass during cardiac surgery
- cardiotomy suction
- cell saver suction
- left ventricular vent
this type of suction refers to suctioned blood that will eventually be returned to the patient ; a blood preservation technique that decreases the chances of the patient needing a donor transfusion
blood salvage
this type of suction takes blood from the field and returns it to the cardiotomy reservoir before eventually ending up into the venous reservoir
cardiotomy suction
will blood from cardiotomy suction run through the bypass machine?
yes
cardiotomy suction and left ventricular vent suction is used (before/after) the patient is heparinized and (should/ should not) be used after the patient comes off bypass
after
should not
What is the main advantage of cardiotomy and left ventricular vent suction?
- it is WHOLE blood which includes clotting factors, platelets, and PRBCs
What are the 2 disadvantages of cardiotomy AND left ventricular vent suction?
- the blood going through cardiotomy suction is damaged by the bypass machine
- associated with a more pronounced systemic inflammatory response and resulting coagulopathy - significant contributor to hemolysis and particulate emboli that occur during bypass
- room air is aspirated with the blood
this type of suction the blood from the field is washed and then centrifuged, which separates PRBCs from the plasma, platelets, and particulate matter
The RBCs are then moved to an infusion bag and transferred back to the patient
cell saver
what is the hematocrit of cell saver blood
50-70%
List 2 advantages of cell saver blood
- Particles such as fat, air, and tissue are filtered out o the blood
- since the blood does not run through the bypass machine it is less damaged when it gets returned to the patient
does cell saver suction blood run through the bypass machine?
no
list 2 disadvantages to cell saver suction
- it is NOT whole blood
- only PRBCs - takes longer before it can be reinfused into the patient
left ventricular vent suction is inserted into the left ventricle through the ______ vein
pulmonary
this type of suction removes all the venous blood that was not picked up by the venous reservoir (blood that comes from bronchial and thespian veins) and returns it to the venous reservoir to prevent left ventricular distention
left ventricular vent
What is the risk of using left ventricular vent suction?
risk of introducing air into the left heart leading to an air embolism
-need to use TEE to assess air before taking the clamp off the heart
in left ventricular vent suction, does the blood go through the bypass machine?
yes
Where should the aortic cross clamp be placed in relation to the arterial cannula?
why?
proximal
-the only way perfusion to the head and the rest of the body is possible
Where should the aortic cross clamp be placed in order for the arterial cannula to perfuse all 3 aortic arch vessels?
the ascending aorta
What are the 3 steps in sequence to arresting the heart and placing a patient on bypass
- drain the blood from the heart via the venous cannula
- place the aortic cross clamp while the heart is still beating
- arrest the heart by injecting cardioplegia
when is it OK for the aortic cross clamp to be placed while the heart is beating?
ONLY when the heart is drained of blood
List 2 ways the heart can be arrested without an aortic cross clamp
- retrograde cardioplegia
2. direct cannulation of the coronary arteries for cardioplegia
List 3 advantages of the aortic cross clamp
- It is easier to arrest the heart
- keeps cardioplegia in the heart and prevents it from washing out to the rest of the body - prevents air inside the heart from entering the circulation
- air can enter the heart when the aorta or hear is opened (valve repair) - prevents re-infused blood from (from the arterial cannula) from backing up into the heart
what are 2 disadvantages to the aortic cross clamp?
- physiologic perfusion to the heart is not possible
2. increases the risk of stroke from a possible dislodging of emboli
how does the heart get perfused during bypass with the aortic cross clamp placed?
the bypass machine through the cardioplegia cannula proximal to the clamp
-usually non-pulsatile
what is the purpose of a partial aortic cross clamp?
allows a hole to be made in order for a graft to be sewn into the aorta without blood shooting everywhere
-once the graft is sewn in, the clamp can be removed
“think of pinching of a balloon to create a hole without it popping”
what is the disadvantage of partial aortic cross clamp?
associated with air emboli and stroke
list 2 advantages to the cardiopulmonary bypass machine
- the surgery is “easier” for the surgeon
2. more hemodynamic stability
list 7 disadvantages to the cardiopulmonary bypass machine
- the priming fluid causes hemodilution ( hematocrit decreases)
- an aortic cross clamp must be placed
- there may be difficulty coming off the pump
- re-establishing an effective heart beat and contractility - pulmonary complications are more likely
- pulmonary edema
- reduces the effects of natural surfactant - Tissue perfusion is less effective
- non-pulsatile
- renal and hepatic perfusion is decreased and drugs are not cleared well - the patient’s blood is damaged from the bypass machine
- hemolysis
- platelet and clotting factors are reduced
- intense inflammatory response occurs - large volume shifts can occur with possible cerebral edema
how many mL of fluid is the bypass machine primed with? What percent of hemodilutional bolus does this usually equate to a patient’s circulating blood volume?
2,000 mL
50-70%
in pediatrics, what is the bypass machine usually primed with in order to prevent hemodilution?
blood
What two types of bypass systems are there depending on the type of venous reservoir used
open or closed
the more common type of bypass system where the venous drainage flows freely by gravity into a venous reservoir that is open to the atmosphere
open aka “hard-shell reservoir”
-air is vented but blood is in direct contact to the air
type of bypass system where the venous reservoir has been removed from the system, or is in the system but closed to the atmosphere
closed aka “collapsible bag”
the advantage of an open bypass system
it is easier to manage for the perfusionist
-more precise monitoring of the venous reservoir (air is automatically purged)
the disadvantage of an open bypass system
there is more blood-air contact resulting in more blood damage
2 advantages of a closed bypass system
- less blood damage
- less air-blood contact
- decreased inflammatory response - less hemodilution
- smaller priming volume
3 disadvantages of a closed bypass system
- less precise visual monitoring of venous return
- the venous reservoir is harder to manage for the perfusionist
- requires an additional system to purge the air
- more distracting for the perfusionist - has less filters and may lead to more microemboli exiting the reservoir
minimal extracorporeal circulation ( mini ECC) is a type of ____ _____ bypass
mini-cardiopulmonary
what is the main advantage of mini-ECC?
the reduction of tubing length/ priming length
what is the priming tube length of mini-ECC?
600 mL
is the mini-ECC a closed or open bypass system?
closed
-limits blood-air contact
what are the 4 components of a mini-cardiopulmonary bypass system?
- pump
- oxygenator
- reduced tubing length
- an arterial filter
what are the 3 components that a mini-cardiopulmonary bypass system does NOT have
- heat exchanger
- venous reservoir
- cardiotomy suction
what are 4 advantages of mini-cardiopulmonary bypass system
- all the advantages of a closed bypass system
- improves myocardial protection
- less defibrillation to restore normal sinus rhythm
- less post-op atrial fibrillation
- consistent coronary blood flow - less blood transfusion
- lower priming volume and less hemodilution - earlier recovery times and reduced ICU and total hospitalization time
disadvantage to mini-cardiopulmonary bypass
demanding for the perfusionist
- cell salvage which delays the return of blood to the circuclation
- air entrapment stops the flow of blood and must be removed by the perfusionist
What is the benefit of “off pump” heart surgery and how does it work?
the patient will not be exposed to all the negative effects of the bypass machine
- suction cups are applied to the heart to limit the the amount of motion while the heart is beating and being operated on
what is the main complication with “off pump” heart surgery?
significant hypotension and arrhythmias due to the suction cups on the heart that reduce cardiac output
this type of bypass refers to only draining a portion of the venous blood from the patient’s body, while the rest of the blood stays in the heart and travels to the body
partial cardiopulmonary bypass
With partial bypass (some/all) the blood is removed from the ____ _____ via the venous cannula. This blood travels through the bypass machine and perfuses the body through the _____ _____
some
right atrium
arterial cannula
with partial bypass (some/all) the blood stays in the heart and goes to the lungs before being pumped into the left ventricle and out of the aorta
some
When a surgeon attempts to do a heart surgery “off pump” but the patient cannot tolerate it- the hypotension is too severe- the surgeon has what 2 options?
- place the patient on full bypass; the heart will be arrested and perfusion will be non-physiologic
- place the patient on partial cardiopulmonary bypass; the heart can still beat and perfusion can stay physiologic
why would the surgeon consider a partial pulmonary bypass technique?
When the patient cannot tolerate an “off pump” a partial bypass technique allows the surgeon to keep the heart beating without the patient getting hypotensive
List 3 surgical considerations of partial bypass?
- the heart must stay beating
- the patient will need to be ventilated and the anesthetist will need to deliver volatile agent
- an ascending aortic clamp does not need to be placed
with left heart partial bypass, blood travels through the (right/left) heart and lungs as normal
right
in left heart partial bypass, how is the blood removed from the left atrium and where does it travel?
blood is removed from the left atrium through a venous cannula
the blood then goes to the bypass machine and enters the arterial cannula where it perfuses the lower extremities
in left heart partial bypass where does the blood that stays in the left atrium end up?
goes out the aorta to perfuse the head
is the right side of the heart perfused and bypassed during left heart partial bypass?
no, ONLY the left side is bypassed
the right side of the heart and lungs are perfused and are NOT bypassed
in left heart partial bypass, does the machine require an oxygenator?
no, all the blood flowing to the bypass machine is already oxygenated
during left heart partial bypass, does the heart need to stay beating and lungs ventilated?
yes
the right side of the heart still needs to pump blood to the left side
in left heart partial bypass, what are the 3 components that are NOT needed on the machine?
- oxygenator
- reservoir
- heat exchanger
what is the only indication for left heart partial bypass repair?
open descending thoracic aorta aneurysm repair
-clamps are on the descending aorta
in left heart bypass for descending aorta repair:
some blood is removed from the left atrium by a reservoir cannula and goes through the bypass machine and perfuses the ______ _______ through an arterial cannula (distal/proximal) to the clamp on the descending aorta
lower extremities
distal
in left heart bypass for descending aorta repair:
some blood stays in the left atrium and is pumped into the aorta to perfuse the _____ and ______ ______ that is (distal/proximal) to the clamp on the descending aorta
head
upper extremities
proximal
List 5 advantages to left heart partial bypass
- the heart stays beating and does not need to be restarted
- physiologic perfusion - lower circuit priming volume
- less hemodilution
- less blood damage from bypass circuit
- less heparinization needed - decreased chance of postoperative renal failure
- only 4% incidence (9-11% with CBP and clamps) - blood pressure can be controlled by the perfusionist
- amount of blood flowing from left atrium to aorta can be controlled - there is no direct blood-air contact in the circuit= less blood damage
- no venous reservoir= closed circuit
what is the target ACT for left heart partial bypass
150-200 seconds
3 disadvantages to left heart bypass
a reservoir, heat exchanger, and oxygenator are not used
- no blood or fluid can be added to the bypass system
- the patient cannot be warmed or cooled by the bypass machine
- without the reservoir, systemic air embolization may be more likely
with right heart bypass where are the venous cannulas placed?
in the superior and inferior vena cava
with right heart bypass, venous cannulas remove (oxygenated/deoxygenated) blood from the (right/left) side of the heart and send it to the bypass machine
deoxygenated
right
in right heart bypass, blood is re-infused into the ______ ______ through an arterial cannula
pulmonary artery
the arterial cannula is placed (distal/proximal) to the aortic cross clamp on the pulmonary artery
distal
is the aorta cross clamped during right heart bypass?
no; results in lower stroke risk
in right heart bypass, only the (right/left) side of the heart is bypassed and the blood from the bypass machine goes to the _____
right
lungs
is an oxygenator necessary in right heart bypass?
no; blood from the machine goes into the pulmonary artery and to the lungs
is the heart arrested during right heart bypass?
no; the machine gets blood to the left side of the heart so the heart must stay beating and the lungs ventilated to pump blood to the rest of the body
3 types of right sided heart operations that use right heart bypass
- tricuspid valve repair
- pulmonic valve repair
- right ventricular assist device (RVAD) placement
What are 3 advantages of right heart bypass for the surgeon?
- the heart can stay beating
- the aorta does not need to be clamped
- the oxygenator does not need to be used on the bypass machine
what are the only two ways that we can repair aneurysms on the ascending aorta or the aortic arch if the distal clamps need to be placed on the aortic arch or the descending aorta
- add another perfusion cannula
- in addition to the regular arterial cannula - make the patient so cold that their metabolic requirements would be low enough to allow them to survive a short period of time with no perfusion
What are 3 options to protect the brain during the operation IF total body perfusion is not feasible with the arterial cannula due to the location of the clamps
- Deep hypothermic circulatory arrest (DHCA)
- retrograde cerebral perfusion with an additional perfusion cannula
- antegrade cerebral perfusion with an additional perfusion cannula
(these can be used in combo or in single)
what is the name of the strategy where the perfusionist puts the patient on bypass, makes the patient profoundly hypothermic, and then turns the bypass machine off and stops circulation throughout the patients body
Deep Hypothermic Circulatory Arrest (DHCA)
-allows certain lesions to be repaired in situations where attempts at perfusion would have been unsafe or hard to achieve
What does DHCA do to blood flow and oxygen requirements?
stops the blood flow through the surgical site which allows the surgeon to complete the operation
AND
oxygen requirements are lowered from the intense hypothermia so the patient can survive a short period of time of having no perfusion
2 of the most common indications for DHCA
- ascending aortic repair
2. aortic arch repair
2 other indications for DHCA
- descending aorta repair
2. clipping of certain complex brain aneurysms
List the 4 steps of placing the patient on DHCA
- the patient is put on cardiopulmonary bypass
- the heat exchanger from the bypass machine profoundly decreases the patients 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
where is the arterial cannula usually placed during DHCA?
what is the other option?
femoral artery
axillary artery
what can you do to help speed up the patient’s cooling process and further protect the brain during DHCA?
ice packs on the head
-can delay brain re-warming and increase ischemic tolerance
What is the typical temperature just prior to circulatory arrest?
15-17 degrees celsius
-the longer the operations takes, the colder the patient will need to be
what are 2 sensors that can be used to monitor the depth of hypothermia and ensure electrical silence during DHCA?
- BIS monitor
2. EEG
at what temperature does the EEG become isoelectric?
between 15-20 degrees celsius at the nasopharyngeal temperature
how long after the EEG becomes isoelectric must you wait before DHCA is initiated?
10 more minutes of cooling to ensure adequate homogeneous cooling of the brain
what is the safe amount of time that DHCA can be performed?
30-45 minutes
DHCA should not be performed for longer than ___ minutes
60
DHCA of less than ___ minutes shows no neurologic complications
30
DHCA of greater than ___ minutes shows an increased incidence of brain injury
40
DHCA of greater than ___ minutes commonly results from some irreversible brain injury
60
what patient population can tolerate LONGER periods of circulatory arrest?
neonates and children
List 3 complications of DHCA
- any general complications of hypothermia
- coagulopathy and profuse bleeding are the biggest - potential neurologic complications
- from bypass, aortic cross clamp, or lack of perfusion time during circulatory arrest - neurologic complications from cooling or warming the patient too rapidly
What timeframe is considered rapid cooling and what does it do to the brain
<20 minutes
lower neurodevelopmental outcome scores
what 4 things does rapid warming after DHCA do to the patient?
- promotes systemic gas bubble formation
- solubility of gas in a liquid decreases as the liquid temperature increases - cerebral oxygen desaturation
- uneven warming
- organ damage
Rewarming should not exceed ___ degree(s) celsius core temperature rise per ___ minutes of bypass time
1
3
termination of rewarming should occur when the nasopharyngeal temperature reaches ____ degrees celsius
35
which type of temperature probe should be used in all DHCA cases?
nasal
why is a nasopharyngeal temperature probe used during hypothalamic cardiac arrest procedures?
provides an accurate reflection of brain temperature during cardiopulmonary bypass
what are 5 additional intervention for brain protection from DHCA?
- preoperative steroids
- hyper oxygenation before DHCA
- allow at least 20 minutes for cooling
- packing the head in ice
- intermittent cerebral perfusion between 15 and 20 minute periods of DHCA
the name of the technique where the surgeon places an EXTRA perfusion line in the SVC in order to deliver cold blood to the head during circulatory arrest
retrograde cerebral perfusion
retrograde cerebral perfusion allows the perfusionist to deliver cold blood to the head through the (veins/arteries) instead of the (veins/arteries)
veins
arteries
what is the purpose of retrograde cerebral perfusion during circulatory arrest?
to provide some blood flow to the head and keep the head cold and oxygenated
when would you use retrograde cerebral perfusion?
during circulatory arrest
the name of the technique where the surgeon places an EXTRA perfusion line in the right axillary artery to perfuse the head and lower extremities during ascending aorta and aortic arch repair
Normothermic Antegrade cerebral perfusion
in retrograde cerebral perfusion, where is the extra perfusion line placed?
SVC
in normothermic antegrade cerebral perfusion, where is the extra perfusion line placed?
right axillary artery
in what circumstance is a normothermic antegrade cerebral perfusion technique used?
during ascending aorta and aortic arch repairs
in normothermic antegrade cerebral perfusion, the perfusionist can can perfuse both the ____ _____ with the regular arterial cannula, and the _____ with the extra perfusion line
lower extremities
head
what does “normothermia” refer to in antegrade cerebral perfusion?
we can repair the ascending aorta and aortic arch under NORMOTHERMIA= without hypothermic circulatory arrest
can antegrade cerebral perfusion be used in conjunction with circulatory arrest?
yes, can provide some head perfusion just like with retrograde cerebral perfusion
what is the disadvantage of using normothermic antegrade perfusion vs. hypothermic circulatory arrest?
placement of the extra perfusion line and manipulations of the arch-vessel cannulation may increase the incidence of stroke
the name of a monitoring device straps to the head and uses “near-infrared spectroscopy” (NIRS) technology to measure oxygen saturation in cerebral vessels
cerebral oximeter
instead of SpO2, a cerebral oximeter displays the saturation of oxygen in the head as ____
rSO2
regional cerebral oxygenation
what is a normal cerebral oxygenation saturation (rSO2) value?
60-80%
the cerebral vascular bed is 75% venous and 25% arterial
what does cerebral oximetry ultimately indicate?
cerebral perfusion
if cerebral blood flow decreases, cerebral oxygen saturation will ( increase/decrease)
decrease
-there will be less arterial/oxygenated blood in the head
a low rSO2 value indicates that cerebral perfusion has (increased/decreased)
decreased
-anesthetist need to increase blood flow and oxygen to the head
What are 2 circumstances where an anesthetist would use a cerebral oximeter?
- Heart surgery
- carries a high risk of stroke intraoperativly and this would alert the anesthetist immediately if cerebral perfusion is disrupted - sitting position/ beach chair surgery
- BP in the head can be uncertain
Triggering points for when an anesthetist should intervene with rSO2 monitoring:
- an rSO2 value less than ____%
- a greater than _____% drop from the individual baseline rSO2
- a difference of ____% from the left and right hemispheres
- rSO2 value less than 50%
- a greater than 20% drop from the individual baseline rSO2
- a different of >30% from the left and right hemispheres
4 factors that can decrease rSO2 values
- decrease in cerebral blood flow
- hypotension/ decreased cardiac output
- hyperventilation (hypocarbia) - hypoxemia
- decreased SaO2 - anemia
- when there are less RBCs, a higher portion of oxygen will be taken off of each RBC= lower rSO2 - mechanical disturbances
- vascular occlusion or compression, embolic events, clamping dissection, malposition of cannulas or balloon pump, clamping
6 ways to increase cerebral SpO2
- increase cerebral perfusion pressure
- increase MAP if patient is hypotensive
- fluids, pressers, trendelenburg - decrease ICP
- mannitol: decreases CSF production
- placement of a lumbar drain
- increase MAP if patient is hypotensive
- increase cerebral blood flow (cerebral dilation)
- increase PaCO2 (decrease patient’s minute vent.)
- Nitroglycerin
- increase FiO2
- Increase cardiac output
- increase hematocrit
- decrease cerebral metabolism
- increase the anesthetic or decrease temperature
the three tests for standard anticoagulation tests
PTT, PT, INR
this anticoagulation test examines the extrinsic pathway of the coagulation cascade
PT (prothrombin time)
normal value of a PT test
12-15 seconds
the anticoagulation test that examines the intrinsic pathway of the coagulation cascade
PTT (partial thromboplastin time)
normal value of a PTT test
25-40 seconds
normal value of INR
0.9-1.1
a “standardized” PT result that corrects for variations in PT from different labs
international normalized ratio (INR)
this drug works by binding and enhancing the activity of antithrombin III 1000 fold
unfractioned heparin
heparin more readily affects the (intrinsic/extrinsic) coagulation pathway and effects the (PTT, PT, INR) coagulation test
intrinsic
PTT
the effects of heparin can be reversed by a drug called _____
protamine
in what type of line should heparin only be given in?
central line
the standard anticoagulant drug used during cardiac surgery and the drug of choice for anticoagulation prior to cardiac surgery
heparin
-prevents blood from clotting in the bypass machine
what is the heparin dose for standard cardiopulmonary bypass cases and when is it dosed?
300-400 units/kg
dosed just prior to aortic cannulation
a clotting time test (obtained from a blood sample) that is used to assess coagulation in the cardiac operating room whenever heparin is given
ACT ( Activated Clotting Time)
a normal ACT time
100-150 seconds
the goal ACT required prior to going on pump for cardiac surgery
> 450 seconds
occurs when a patient’s immune system develops antibodies against heparin
Heparin Induced Thrombocytopenia (HIT)
- thrombocytopenia (low platelet count)
- thrombosis
usually occurs with standard heparin
When a patient has a hx of heparin induced thrombocytopenia and needs to have cardiac surgery, what drug can be used as a direct thrombin inhibitor for anticoagulation?
argatroban
-dosing guidelines are unclear and it is more difficult to control post-op bleeding
patients with this deficiency will show resistance to heparin
antithrombin III
- deficiency can be inherited or acquired from previous heparin administration
2 ways to manage antithrombin III deficiency
- Replace the antithrombin III
- concentrates are available and pre-operative replacement should be 100% before cardiac surgery - Administer FFP
- if antithrombin III concentrates are not available, transfusion of plasma will replace antithrombin III but has a higher degree of viral transmission
what is the most common version of low molecular weight or fractioned heparin?
lovenox (enoxaparin)
4 ways fractioned (LMW) heparin is different from standard heparin
- it is dosed subcutaneously
- longer lasting (12-24 hours)
- Doesn’t prolong PTT as much
- not reversed as reliably with protamine
Standard heparin:
- only administered IV
- has a half life of 1 hour
what is the better anticoagulation test that is used for lovenox?
anti-Xa assay
a vitamin K antagonist that effects the extrinsic coagulation pathway
Coumadin (warfarin)
Coumadin (warfarin) is dosed (PO/IV) and affects the ____ and ____ coagulation tests
PT and INR
2 ways the effects of Coumadin can be reversed
- FFP
2. vitamin K
a PO antiplatelet drug similar to aspirin
Plavix (clopidogrel)
how long does Plavix last and how is it reversed?
5-7 days
platelet transfusion. Half life of plavix is long so platelets need to be administer over a prolonged period of time
how long should aspirin be discontinued prior to elective surgeries?
7 days
patients who have recently had a coronary balloon angioplasty and/or stent are at risk for coronary thrombosis and are commonly treated with 2 antiplatelet drugs known as?
what are the 2 drugs used?
Dual antiplatelet therapy
aspirin and plavix
if a patient needs to have surgery but is on dual antiplatelet therapy, why is it a risk to discontinue the antiplatelet agents?
coronary occulution
if a patient needs to have surgery but is on dual antiplatelet therapy, why is it a risk to continue the antiplatelet agents?
major intraoperative bleeding that could lead to fatality
Managing Dual antiplatelet therapy in surgery:
patient underwent balloon angioplasty; dual antiplatelet therapy is required for _____
14 days
Managing Dual antiplatelet therapy in surgery:
Patient received a bare metal stent, non-urgently;
dual antiplatelet therapy is required for _____
elective surgery should be delayed for _____
one month
one month
Managing Dual antiplatelet therapy in surgery:
patient received a bare metal stent, urgently (acute coronary syndrome);
dual antiplatelet therapy is required for _____
elective surgery should be delayed for ____
one year
one year
Managing Dual antiplatelet therapy in surgery:
a patient received a drug-eluting stent, non-urgently;
dual antiplatelet therapy is required for _____
elective surgery should be delayed ____
6 months
one month
Managing Dual antiplatelet therapy in surgery:
patient received a drug-eluting stent, urgently (acute coronary syndrome)
dual antiplatelet therapy is required for _____
elective surgery should be delayed _____
one year
one year
Managing Dual antiplatelet therapy in surgery:
urgent surgery may be continued with (aspirin/plavix) but not (aspirin/ plavix)
aspirin
plavix
2 drugs that are direct factor Xa inhibitors
Xarelto (rivaroxiban) : taken PO
Eliquis (Apixaban)
how long should Xarelto be discontinued prior to surgery?
24 hours
the drug that is an inactivated from of Xa and binds to Xarelto and Eliquis to inhibit their activity
Andexxa
how long should Eliquis (Apixaban) be discontinued prior to surgery?
48 hours
patients that have had a thrombolytic agent (rtPA, streptokinase, urokinase) should not have elective surgery for at least ______
10 days
this drug is derived from salmon sperm and reverses anticoagulation caused by heparin (brings the patient’s ACT back to normal)
Protamine
when is Protamine dosed in cardiac surgery?
After the patient is taken off cardiopulmonary bypass
-give slowly peripherally
what is the Protamine dose
1 mg Protamine per 100 units Heparin
what is the mechanism of Protmamine
binds to Heparin directly and heparin is no longer able to work by binding antithrombin III
-Protamine has anticoagulation properties and excess protamine may therefore potentially increase bleeding
3 adverse affects of Protamine
- Hypotension
- more likely with rapid/central administration - anaphylactoid reactions
- more likely with rapid/central administration, prior exposure to Protamine, patient’s allergic to fish, male patients who have had a vasectomy, and diabetics exposed to Protamine through insulin - possible catastrophic pulmonary vasoconstriction
a concentrated extract from fresh-frozen plasma (factors are at 25 fold higher concentration than FFP) and can be given as part of a massive hemorrhage protocol in replacement of FFP
contains the vitamin K dependent clotting factors (II, VII, IX, and X), is used to treat life threatening hemorrhagein unstable patients onanticoagulants, and can be used to reverse the effects of Vitamin K antagonists
Prothrombin Complex Concentrates (PCC)
4 advantages of PCC
- 2X as fast as FFP in coagulopathy reversal
- single dose every 24 hours (less volume required)
- half the adverse effects (transfusion reactions) as FFP
- Faster prep time than FFP (does not require thawing)
2 disadvantages of PCC
- up to 20X more expensive than FFP
2. shorter acting than FFP (lasts for less than a day)
what vitamin should PCC be concurrently administered with because of it short acting nature
vitamin K
