Indications for CPB?
Open heart procedures; Unstable hearts that do not tolerate mechanical manipulation (e.g. valve repair); transplants; Distal airway reconstruction
Describe the bypass circuit
Drain venous blood, collect in a reservoir, pump it through a device, oxygenate and filter, return via aorta
Why does the CPB tubing use biosurface/biopassive coating/heparin coating?
To reduce protein denaturation and platelet adhesion (Notes in the ppt: Inflammation on CPB- Why, blood on plastic interface.For decades, the blood-tubing interface was untreated PVC. Collectively, the coating reduce markers of subclinical coagulation, attenuate elev of cytokines and other inflammatory markers and shorten postop Ventilation times)
Why is hard shell reservoir better than soft shell ones?
stable blood level and high visibility scale
Compare the roller pump and centrifugal pump
Positive Displacement Pump- Roller Pump, in raceway. milks the fluid ahead. Afterload independent, Flow is- RPM, Tubing size; Disadvantages- Spalling, hemolysis, can pump air. Roller pumps, by virtue of their occlusive nature, are capable of generating extremely high positive and negative pressure and are also able to pump massive quantities of air.
Centrifugal pump: Low priming volume, Low heat, Low shear, low hemolysis.CF Pump-constrained vortex that propels fluid through the opening on the side of the cone while drawing fluid into the point of the cone. Flow output is a complex function of rpm, torque and back pressure – centrifugal pumps, being nonocclusive, are unable to generate extremely high or low pressure. Additionally, if a large bolus of air is introduced into the disposable cone, the pump will deprime, rendering it unable to pump large volumes of air.
Compare the oxygenator and the natural lung
What do we use for anticoagulation during CPB, what's the dose and how to we monitor the effect?
Unfractionated heparin; 300 units/kg; use Activated Clotting Time (ACT)>400 sec, yet maintain stable heparin levels through automated protamine titration rather than stable ACTs
What are some hemodynamic values we can get from CPB machine?
Cardiac output; SvO2; SVR; ABG; Temp; UOP
Criteria for weaning off the CPB
Confirmed by Echocardiography
Appropriate Gas exchange
What should be checked post CPB?
Protamine to reverse UFH (aware of Heparin Rebound);
Follow up Hematology Studies: ACT, TEG, PT/INR/PTT, Fibrinogen, Thrombin Time
Complications from CPB?
Graft Failure, Thrombosis, Coronary Spasm
Left/ Right heart failure