Cardiopulmonary Bypass

Question 1

What is CBP?

Answer 1

Blood from the R atrium goes through a venous cannula into the oxygenator where blood is oxygenated and CO2 is removed.

Blood is then returned to the aorta through an arterial cannula where it then circulates through the rest of the body.

Filter: used to trap air, bubbles, clots, debris

Roller Pump: used to maintain adequate flow

Question 2

CBP Initiation

Answer 2

-median sternotomy is performed
-pump is primed with fluid. Hct>25%
-Heparin 3-4mg/kg to achieve ACT>400
-Cannulas are placed
-Roller pump adjusted to keep flow >2L/min
-the L ventricle is vented with a cannula to aspirate intracardiac blood to avoid overdistention of chamber
-pulmonary artery is vented to prevent blood return to the heart
-heart is arrested
-the aorta is cross-clamped
-cold and hyperkalemic solution is inserted directly into the aortic root
-body temp is decreased to 25-28C which decreases O2 demand by 50%

Question 3

CBP Discontinuation

Answer 3

-acid-base, temp, H&H is corrected
-anesthetic agents d/c and vent with 100% O2
-Once BP and heart function are confirmed, venous outflow is slowed and stopped
-cannulas are clamped and heart is difibrillated
-AV wires and MCT placed
-protamine sulfate given
-sternum is wired and incision is closed

Question 4

Types of Grafts

Answer 4

1. Saphenous vein graft (SVG)
2. Radial artery (RA)
   may allow for two grafts
   arterial and venous punctures are prohibited in the affected arm both pre and post-op
   can’t take BP on affected arm for 3mos
3. Internal mammary artery (IMA)
   suitable for RCA and LAD
   most susceptible to sternal wound infection

Question 5

Types of Valves:

Answer 5

mechanical, bioprosthetic, and hemografts

-no turning for 4 hours
-FiO2 100% for 4 hours
-recovery process same as CABG

complications: higher risk of 3* AV block

Question 6

Mechanical valve

Answer 6

age group >70
durable life performance
requires anticoagulation
PT/INR monitoring

Question 7

Bioprosthetic valve

Answer 7

low thromboembolic rate
degeneration will require replacement
mitral valve (7-10yrs), aortic (10-15yrs)
risk of calcification

Question 8

Homograft valve

Answer 8

superior hemodynamics
no need for anticoagulation
moderate durability