Temporary Mechanical Circulatory Support Flashcards
What is the incidence of requirement for temporary MCS after cardiac surgery?
0.2-0.6%
Who invented the IABP and in which year?
Adrian Kantrowitz 1967
What is the major effect of IABP? What are the minor/secondary effects?
Decreased afterload (15%) and increased coronary perfusion (21% increase in flow to ischemic areas)
Decreased LV wall tension, decreased O2 consumption, reduced LVEDV, LVESV, reduced preload
What is the IABP timed to activate towards?
ECG R wave and arterial pressure tracing
What are the 3 major indications for IABP?
Bonus: name 5 more indications for IABP
Cardiogenic shock, post-pericardiotomy low cardiac output, uncontrolled myocardial ischemic pain
Bonus: high risk/failed PCI, high grade left main, poorly controlled ventricular arrhythmias before or after operation, post-MI VSDs or post-MI acute MR
What is the landmark for puncture of the femoral artery? What are the access sites for IABP?
1-2 cm below the mid-inguinal point (mid point of the ASIS and pubic symphysis not to be confused with the mid point of the inguinal ligament which is the landmark for the femoral nerve) or 1-2cm above the inguinal fold (not always accurate)
Femoral (most common), abdominal aorta, iliac arteries, axillary arteries, direct insertion into ascending aorta (intra-op)
What size is the IABP?
7 Fr (1 Fr = 0.33mm)
What is the complicate rate associated with IABP? What are the complications?
20%
Leg ischemia, balloon rupture, balloon thrombosis, pseudoaneurysm, lymphocele, lymphatic fistula, AV fistula, infection, septicemia, femoral neuropathy
How can you tell if a balloon ruptures and what do you do if the balloon ruptures?
Blood will be seen in the balloon catheter and an alarm may go off
Deflate the balloon forcibly and remove the balloon
What do you do if pain, decreased sensation and compromised circulation occur in a IABP?
Promptly remove the balloon and if the patient is balloon dependent, place an IABP in the contralateral groin
What is the IABP SHOCK II trial and what did it show?
This trial randomized 600 patients with acute MI and cardiogenic shock who were planned to undergo revascularization to either IABP or medical therapy. There was no difference in the 30 day mortality and no difference in adverse advents
What is the average overall survival for patients put on temporary MCS?
21-41%
What are the criteria for cardiogenic shock?
Cardiac index < 2.2L/m2, sBP <90, mean PCWP or CVP >20mmHg and concomitant use of high doses of 2 or more inotropes
What are three drugs commonly used in RV failure?
Milrinone, NO and vasopressin
What are the differences between CPB and ECLS?
ECLS is a continuous flow circuit, without areas for stasis like the venous reservoir or cardiotomy suction reservoir, which means lower doses of heparin are required and less activation of the inflammatory response and coagulopathy. ECLS provides partial cardiorespiratory support. ECLS has a diffusion membrane instead of a microporous membrane. There is no way to de-air in the ECMO circuit, there is no blood air interface.
What are the components of the ECMO circuit?
Venous cannula, Membrane oxygenator, Centrifugal pump, Heat exchanger, Arterial cannula
What are the cannulation sites for central and peripheral ECMO?
Central: ascending aorta and right atrium
Peripheral: axillary, femoral
What size cannula are typically used?
Arterial 16-20Fr
Venous 18-25Fr
What must you be concerned about with axillary artery cannulation?
Progressive arm edema. Treatment is partial occlusion of distal axillary artery with vessel loop. Make sure you have a right radial artery arterial line to ensure you know the right arm is perfused when you cannulate the right axillary.
What does ECLS do to the heart in terms of preload/afterload to the right/left hearts? What can be done to fix this?
ECLS can unload the RV, but will not unload a compromised LV. It can reduce LV preload but will increase LV afterload slightly. A poorly contractile LV may not be able to eject and can remain dilated, which increases myocardial O2 consumption. A LV vent can be inserted to decompress a dilated LV.
What are the complications of ECMO?
Bleeding, renal failure requiring dialysis (47%), stroke (10%), bacteremia or mediastinitis (23%), leg ischemia (70%), oxygenator failure requiring change (43%) and pump change (13%)
What do you do when you find clot in the pump head?
What do you do when there is leakage of plasma across the membrane?
Pump head change
Monitor, but this may cause increased resistance to flows and necessitate oxygenator change
How do you do central VA ECMO
The eopa cannula is inserted into the ascending aorta. The cannula is the same size as the regular cannula 20Fr.
The venous cannula is a single stage Bard cannula, large diameter (38Fr) and it is inserted to sit in the middle of the RA. The purse string is made halfway between the RAA and the IVC. The Bard cannula does not sit too deeply. They must be secured with double plegeted (bovine pericardium) sutures. Use special VAD tourniquets. Tunnel the cannula through the skin, the aortic cannula through near the left costal margin, the venous cannula through the right costal margin.
How do you vent the LV?
IAS via balloon atrial septostomy, or LV via RSPV or LV via apex or Impella.
Hook up your vent to 1/4 inch tubing then use a 1/4 to 3/8ths connector, Y that into a 3/8-3/8-3/8ths connector. The benefit of this approach is reduced risk of stasis of the vent drainage and you can put a flow probe on the tubing.
