Clinical Scenarios in Cardiac Surgery

Question 1

What are the optimal management of porcelain aorta in the setting of CABG?

Answer 1

1. Axillary artery cannulation, circulatory arrest, ascending aorta replacement
2. Off-pump CABG using bilateral mammaries +/- Y grafts (radial or RIMA or SVG) or Heartstring device or SVG with proximal anastomosis to carotids, innominate, subclavian, right axillary, descending thoracic aorta etc or gastroepiploic
3. Hybrid CABG with LIMA-LAD and stents to other vessels
4. Pump-assisted CABG if off-pump not tolerated

Question 2

What are the ABCs of cannulation?

Answer 2

A - anticoagulate
B - be sure you are high enough on the ascending aorta
C - check for calcifications

Question 3

What are the ABCs prior to initiation of CPB?

Answer 3

A - ACT > 480s
B - Breathing (hold ventilation)
C - Circulation (forward flow and drainage, PAPs, CVP should be low)

Question 4

Weaning from CPB mnemonic?

Answer 4

A - Anastomosis
B - Beat of the heart, Breathing
C - Circulation (MAPs)
D - Degrees (36C)
E - Electrolytes, Echo 
F - Flows (gradually reduce while observing heart and hemodynamics)
G - Gases (ABG)
H - Hypertension (vasodilate)
I - Inotropes
J - Juices (u/o)

Question 5

You release the cross clamp and the heart begins to distend without contraction, what do you do?

Answer 5

Two considerations - 1. there is AI 2. The heart is not ejecting

First step is to squeeze the heart to decompress it starting from the apex to the LVOT. You can also try to pace or tap the heart to encourage ejection.

If this does not work you may need to place an LV vent or re-clamp the aorta. Check the echo for AI and check for electrolytes. You may need to bring down the potassium, or fix moderate-severe AI.

Question 6

You release the cross clamp after MV repair and the heart begins to fibrillate, what is your approach to fibrillation?

Answer 6

Get the paddles and set to 10-20J and shock the patient. If you cannot convert give IV lidocaine or amio or esmolol and try again. The issues that can cause difficulty with cardioversion include distension, air, low systemic pressures, electrolyte abnormalities, poor oxygenation and hypothermia as well as coronary ischemia or valve incompetence.

If the heart is distended, you can try squeezing the heart or putting in an LV vent. Make sure your root vent is on to evacuate any air. Increase perfusion pressures to >75mmHg to flush out any embolized air. Check to make sure mitral stitches did not catch the non-coronary leaflet of the AV and check to make sure there are no ST changes or regional wall motion abnormalities. These issues may need repair or bypass respectively.

Question 7

What are the components of the CPB machine?

Answer 7

Venous cannula -> venous tubing -> venous reservoir -> membrane oxygenator -> heater/cooler -> centrifugal pump -> air sensor -> aortic tubing -> aortic cannula

Question 8

What do you do when your ACT is not adequate for bypass after giving heparin?

Answer 8

There is concern for ATIII deficiency. Give another full dose of heparin. If the ACT does not rise, then consider FFP or recombinant ATIII factor.

Question 9

What is your checklist for high aortic line pressure?

Answer 9

Obstruction of the arterial line (kink or clamp on the line)
Malposition of the aortic cannula
Cannula too small for CPB
Evidence of aortic dissection: systemic pressure will be low and the ascending aorta will be abnormal

Question 10

What is your checklist for poor venous return?

Answer 10

Check for venous air lock
Ensure good position of the venous cannula
Elevate the level of the patient in relation to the reservoir (if relying on gravity)
Use suction drainage
Increase cannula size
Reduce flows
Exclude other sources of blood flow into the heart especially in the setting of distension (AI - vent, azygous vein - adjust snares, left sided SVC - snare or cannulate)
Consider other sites of volume loss (retroperitoneal or peritoneal hemorrhage)

Question 11

What is your checklist for vasoplegia on pump?

Answer 11

Can be seen when patients are on anti-hypertensives pre-op, particular ACE-I. Give phenylephrine, levophed, vasopressin or methylene blue

Question 12

What is your checklist if the retrograde cardioplegia line pressure is low?

Answer 12

Catheter displaced in the RA
Rupture of the coronary sinus
Balloon rupture
PLSVC

Question 13

What do you do when the RV distends when weaning the patient off bypass and ST elevations are present on the EKG along with hypotension and you suspect air embolism down the RCA?

Answer 13

Re-institute CPB at a high perfusion pressure to push the air through the coronary artery. De-airing the heart through an aortic root vent will prevent further migration into the coronaries. Consider evacuating air through the apex with a large bore needle if there is a large collection of air at the apex.

Question 14

What do you do if you notice an iatrogenic aortic dissection?

Answer 14

1. Establish arterial access through the true lumen (axillary, femoral or direct AAo/Arch if confident)
2. Establish venous access (femoral, RA)
3. Cool to 18C
4. Circ arrest
5. Replace the ascending aorta
6. Resume flow

Question 15

What do you do when you notice massive air embolism in the aortic line?

Answer 15

1. Stop CPB
2. Decannulate the aortic line, ask perfusion to clamp arterial and venous lines and de-air the circuit
3. Steep trendelenburg
4. Aspirate air from the aortic root
5. Cannulate the SVC to initiate retrograde cerebral perfusion at 300mL/min
6. Ask anesthesia to give 100% O2, Steroids/barbituates/mannitol and pressors to support circulation
7. Watch for air bubbles coming into the root vent once RCP initiated
8. Reinstitute CPB and cool the patient to 28C for brain protection
9. Massage coronaries to displace air
10. Complete surgical procedure and de-air the heart in the usual fashion
11. Keep sedated post-operatively and consider hyperbaric chamber post-operatively

Question 16

What is the target MAP on CPB?

Answer 16

Roughly equivalent to the patient’s age

Question 17

During a redo AVR after previous CABG, what myocardial protection strategy would you pursue and what factors would you consider?

Answer 17

Use cold blood cardioplegia 4:1 blood to crystalloid at 4C and intermittently perfuse q15-20min.
Use antegrade and retrograde cardioplegia
Identify the LIMA and clamp it

Question 18

What would you do if in a redo AVR after CABG, your retrograde cardioplegia becomes dislodged?

Answer 18

Open the aorta and give antegrade cardioplegia directly down the vein grafts, cool to moderate hypothermia
Snare the cavas and try to directly insert the retrograde catheter to get perfusion of the LAD distribution
If you cannot, cool to 20C and leave the LIMA-LAD open

Question 19

What is the target coronary sinus pressure upper limit? What is the target coronary sinus line pressure limit?

Answer 19

<40mmHg sinus pressure, <200 line pressure

Question 20

How would you insert a direct retrograde cannula?

Answer 20

Usually done when aorta is cross clamped. Requires bicaval cannulation, caval snares for atrial isolation, small atriotomy, hand held retractor, identification of the ostium and purse strong and direct placement of the coronary catheter.

Question 21

What should you check if after unclamping the aorta during a case with retrograde cardioplegia and the myocardium is slow to regain electrical activity?

Answer 21

Check to make sure the retrograde catheter is either removed or the balloon is down so that it does not occlude the coronary sinus and prevent flow.

Question 22

When sewing the distal coronary anastomosis during a CABG, you notice increased bleeding from the coronary arteriotomy? What do you do next?

Answer 22

First concern is myocardium is being perfused:

1. check the aortic cross clamp is occlusive
2. check the aortic root vent is on
3. could be from collateral circulation
4. monitor for signs of electrical activity and consider cold topical saline, cooling the patient to 32C, reducing flows as tolerated or more frequent administration of cardioplegia solution

Question 23

When performing a redo sternotomy, you encounter a significant amount of dark blood from the sternomanubrial junction, what do you do?

Answer 23

1. Pack the area and have the sternum re-approximated to tamponade the bleeding
2. Cannulate in the groin and initiate CPB
3. Dissect out the innominate vein and achieve adequate length without tension
4. Repair with a bovine or autologous pericardial patch using 5-0 or 6-0 prolene suture or primary repair transversely to avoid narrowing the vein
5. If irreparable, it is safe to divide and oversew both ends of the vein
6. If injury too lateral, may need to ligate the innominate vein down the middle to relieve tension and repair the tear or consider trapdoor incision

Question 24

When dissecting for SVC cannulation, you create a large hole before you place your purse string sutures, what do you do?

Answer 24

1. Tamponade the SVC injury
2. Cannulate the IVC and aorta and initiate CPB with vacuum assisted drainage to avoid air lock
3. Try to identify tear and see if it is reparable
4. If not visible, may need to tourniquet the proximal SVC and/or place a pump sucker or ligate the azygos vein to drain upstream of the injury.
5. Repair with either a pericardial patch or primarily.

Question 25

After inserting a retrograde cardioplegia catheter, you notice dark red blood coming from behind the heart, what do you do?

Answer 25

1. Remove the retrograde cardioplegia and use antegrade cardioplegia, the coronary sinus is likely perforated
2. May need to place a few horizontal sutures to stop the bleeding
3. Inspect after the procedure and may need to use a pericardial patch

Question 26

While cannulating for bicaval cannulation in a frail elderly woman, you tear the IVC past the diaphragm, what do you do?

Answer 26

1. Insert the cannula past the tear
2. Inspect the defect and repair primarily or with patch if possible.
3. Otherwise, go on bypass with SVC cannula and sucker bypass and cannulate the femoral vein, with femoral bypass you drain inferior to the tear
4. Incise the diaphragm and inspect the tear, may need to extend incision into the abdomen and along the right subcostal margin to expose and mobilize the liver infero-medially to repair

Question 27

You are called to the cath lab due to a RV perforation during RV ablation, the pericardial drain inserted shows significant bloody drainage, what do you do?

Answer 27

1. Transfer to the OR, median sternotomy, place on CPB, arrest the heart and identify the puncture
2. Even if small, perform a wide patch repair over the defect

Question 28

After performing an AAo replacement and coming off pump, you notice continuous drainage from the left of the aorta, you identify a 3mm hole in the right PA, what do you do?

Answer 28

1. You can attempt a small figure of 8 or purse string suture but be prepared to go on pump.

Question 29

You are ready to go on CPB for an AVR. After cross clamping and beginning antegrade cardioplegia you notice some bleeding under the arch of the aorta but cannot find a source. You dissect along the posterior backside of the aorta and find bleeding opposite to your cannulation site, what do you do?

Answer 29

1. This is likely an injury to the backwall of the aortic wall during cannulation. Cool to 20C, If bleeding is under control and forward flow is good, cool with your current cannula, otherwise consider weaning down on CPB and cannulating the axillary artery.
2. Obtain a TEE to rule out dissection
3. Make a small aortotomy and complete a primary repair with a horizontal mattress prolene stitch from the inside.
4. Resume bypass, rewarm and resume your procedure