IABP/ECMO

Question 1

What are the major functions of an IABP?

Answer 1

Improve myocardial O2 supply + decrease O2 demand + increased CO + improve coronary perfusion

Question 2

Does the IABP balloon completely occlude the aorta with inflation?

Answer 2

No, it should only be 85-90% occlusive

Question 3

What are the indications for IABPs?

Answer 3

Acute cardiogenic shock + prior to high-risk CABG or PCI + inability to separate from CPB + unstable angina

Question 4

What are contraindications for IABPs?

Answer 4

Aortic regurgitation + aortic dissection + aortic aneurysm + severe sepsis + vascular access issues

Question 5

When does inflation occur for an IABP?

Answer 5

During diastole (triggered by the dicrotic notch/AV closure or middle of the T wave)

Question 6

What are the physiologic effects of an IABP?

Answer 6

Decreased LV afterload/LVEDP/wall tension

Question 7

What are complications of IABPs?

Answer 7

Limb ischemia + hemorrhage + atheromatous emboli (CVA) + thrombocytopenia + hemolysis + helium embolization

Question 8

What is synchronized counter-pulsation?

Answer 8

The mechanism by which IABPs work: inflates during diastole and deflates during systole

Question 9

What’s the only parameter you can change on an ECMO circuit?

Answer 9

The RPMs

Question 10

What does the pump inlet pressure or venous pressure measure? What is it affected by?

Answer 10

The amount of pressure needed to drain blood; affected by cannula size, length, patient volume status, venous resistance

Question 11

What does an increasing negative venous pressure indicate?

Answer 11

Can indicate that the patient is volume down (more pressure needed to drain the required blood)

Question 12

What is the delta pressure or pressure drop in ECMO?

Answer 12

The pressure gradient across the membrane/oxygenator

Question 13

What does an increasing pressure drop or delta P indicate?

Answer 13

Might be due to thrombosis in the oxygenator

Question 14

What 4 factors affect the ECMO flows?

Answer 14

1. Pump speed 2. Drainage cannula size 3. Preload 4. Afterload

Question 15

What are the key differences between ECMO and CPB?

Answer 15

ECMO can be used for days to months + No venous reservoir or blood/air interface + no arterial filter + lower heparin dose + only centrifugal pump + less hemodilution

Question 16

How are lipophilic anesthetic meds affected by ECMO?

Answer 16

ECMO circuit adds about 400-800cc of blood so volume of distribution is increased; highly lipid soluble agents require higer doses

Question 17

What drugs do you need a higher amount while on ECMO?

Answer 17

Propofol + benzos + precedex + ketamine + opioids (particularly fentanyl) + volatile anesthetics

Question 18

How are NMBs and succinylcholine affected while on ECMO?

Answer 18

NMBs may require a higher initial dose but you might see prolonged effects; succinylcholine will have a prolonged effect (pseudocholinesterase levels are lower in critically ill patients)

Question 19

Where are the cannulas located for fem-fem VV ECMO?

Answer 19

The drainage cannula is in the mid IVC and the return cannula is in the RA

Question 20

What is ultra-protective ventilation?

Answer 20

The type of ventilation that should be used while on ECMO: Low driving pressures (10-15 cmH2O) + low RR (<12) + low plateau pressures (<25 cmH2O); these values are lower than the standard ARDS protective ventilation

Question 21

What are the determinants of O2 sats while on VV ECMO?

Answer 21

ECMO flow + O2 fraction of circuit + ratio of ECMO flow to native cardiac output + recirculation + metabolic demand + native lung function

Question 22

What is recirculation while on VV ECMO?

Answer 22

Post oxygenator blood is sent out the return cannula but then taken back into the drainage cannula

Question 23

What should you worry about if you see a decrease in O2 sats with increasing VV ECMO flows?

Answer 23

Recirculation

Question 24

What are the steps for weaning off VV ECMO?

Answer 24

1. Reduces FiO2 2. Reduce sweep gas 3. Off-sweep gas challenge 4. Prepare for decannulation

Question 25

What is North-South syndrome?

Answer 25

AKA Harlequin syndrome: Only seen with peripheral VA ECMO: patient’s native heart function recovers but lung function has not -> heart pumps deoxygenated blood into the body normally -> mixing zone present

Question 26

Where should the arterial line be while on VA ECMO?

Answer 26

Right upper extremity: this is to diagnose North-South or Harlequin syndrome (mixing zone)

Question 27

How do you treat North-South Syndrome?

Answer 27

Decrease inotropes (make the heart do less) + optimize vent settings + increased VA ECMO flows to move mixing zone closer to the aortic root + VAV ECMO

Question 28

What is the only clinical predictor of weaning success from VA ECMO?

Answer 28

Pulse pressure (other things that can be looked at include aortic VTI + LV EF + lateral mitral TDI + >10% improvement in TV annular velocity (RV function))

Question 29

What is VAV ECMO?

Answer 29

Blood is drained from the IVC (femoral venous cannula) and returned to the femoral artery and the RA (usually via the RIJ)