Mechanical Circulatory Support

Question 1

ECMO RPMs should be titrated to what goal index?

Answer 1

CI 2.2 - 2.4

Question 2

What are some relative contraindications to mechanical circulatory support?

Answer 2

Known severe PVD that precludes access.

Devastating neurological injury.
DNR.

Question 3

Relative to the inguinal ligament, where should you stick for a femoral cannula?

Answer 3

Below it.
If you access above, you may damage strictures in the canal.
Also, you can cause bleeding that would be difficult to hold pressure on and access.

Question 4

In an ARDS/respiratory failure patient being considered for ECMO, what is a reasonable cutoff for initiation?

Answer 4

Failure of conventional care w/ PaO2/FiO2 <70. Refer in an early course of the disease.
Earlier may be better. Try not to limp along without it for too long.

Question 5

In cardiac failure patients requiring HD, or have advanced HF, or have recovered from ARDS, compare ECMO to conventional therapy?

Answer 5

Long-term survivors of ECMO performed for cardiogenic shock have better general health, physical health, and social functioning than patients on conventional therapy who require chronic hemodialysis, have advanced heart failure, or have recovered from ARDS

Question 6

Compare ECMO to conventional cardiopulmonary resuscitation for cardiac arrest.

Answer 6

Increased survival.

Question 7

What would be a pH threshold to initiate ECMO in a patient with hypercapnic respiratory failure?

Answer 7

pH < 7.2.

Question 8

Can ECMO be utilized for massive PE?

Answer 8

Yes

Question 9

Can ECMO be used as a bridge to lung or heart transplant?

Answer 9

Yes

Question 10

Outcomes for ECMO in patients with respiratory failure are better if initiated within how many days of intubation?

Answer 10

7 days

Question 11

Describe the ECMO circuit.

Answer 11

Blood is drained from the vascular system, circulated outside the body via a mechanical heat pump, passes through an oxygenator (that also removes CO2) and heat exchanger, and reinfused into the circulation.

Question 12

How is blood oxygenation and CO2 removal adjusted in an ECMO circuit?

Answer 12

Oxygenation is determined by flow rate.
CO2 is determined by the countercurrent gas flow (sweep).

Question 13

What is VV ECMO used for? Where are the cannula?
How big are the cannula?

Answer 13

VV ECMO is used for respiratory failure in a patient that does not need circulatory support.
Drainage cannula is usually inserted into the CFV and the tip resides in the IVC or RA (ideally at the junction).
The infusion cannula has to be distal (deeper towards the RA) or else you will just be draining what you infuse. Usually inserted into the RIJ with the tip just distal to the SVC/RA junction.
Usually 31 Fr - accommodates most adults.

Question 14

What is the main risk for VA ECMO (ie why don’t we always use VA and forego VV)?
What is the most common complication?
How do you prevent/tx this?

Answer 14

VA ECMO has arterial complications - ischemia of the LE is the main one. Dissection can also happen.
Prevent ischemia with distal infusion catheter.

Question 15

What are the drawbacks and benefits of the different peripheral arterial cannulation sites for VA ECMO?

Answer 15

CFA, right common carotid, or subclavian artery can be used.
Femoral is usually favored since the cannulation is easiest.
R CCA or SCA are used when the femoral is not amenable (severe occlusive PAD, prior femoral recon).
SCA is advantageous because it allows patients to walk.

Question 16

What is the ACT goal for ECMO?

Answer 16

180-210 w/ heparin.
(PTT >1,5x normal)

Question 17

What are the ABG/lab goals for ECMO?

Answer 17

On VA ECMO, PAO2 should be >90%.
On VV ECMO, PAO2 should be >70%.
Venous O2 sat should be 20-25% lower than arterial. Lowest should be 50%.
Lactate should be normal.

Question 18

What lab can be checked, if a high amount of heparin is being infused without much response in the ACT/PTT/anti-Xa?

Answer 18

AT3 levels. If <50% normal, give FFP or AT3 back.

Question 19

What is the role of measure the platelet level during ECMO?

Answer 19

ECMO continuously activates platelets d/t exposure to the foreign surface.
It should be maintained >50K.

Question 20

What is the ideal Hgb in patients on ECMO?

Answer 20

12 g/dL
ECMO circuit is often the only source of oxygen in patients with complete cardiac or pulmonary failure. Oxygen delivery depends on the amount of hemoglobin and blood flow. The risks of high blood flow outweigh the risk of transfusion.
Transfuse liberally in order to reduce flows.

Question 21

How do you manage the vent in ECMO patients?

Answer 21

Ventilator settings are reduced during ECMO in order to avoid barotrauma, volutrauma (ie, ventilator-induced lung injury), and oxygen toxicity. Plateau airway pressures should be maintained less than 20 cm H2O and FiO2 less than 0.5. Reduction of ventilator support is usually accompanied by increased venous return, which improves cardiac output.

Question 22

How do you make decision for trach in ECMO patients?

Answer 22

Early tracheostomy to reduce dead space and improve patient comfort.

Question 23

How do you manage sedation in ECMO patients?

Answer 23

Patients typically require light sedation during ECMO, although it is preferred to maintain patients awake, extubated, and breathing spontaneously.

Question 24

How do you manage the blood flow during ECMO? Are there different ideals for VV vs VA?

Answer 24

Near-maximum flow rates are usually desired during VV ECMO to optimize oxygen delivery.

In contrast, the flow rate used during VA ECMO must be high enough to provide adequate perfusion pressure and venous oxyhemoglobin saturation (measured on drainage blood), but low enough to provide sufficient preload to maintain left ventricular output.

I.e. maintain pulsatility so LV doesn’t clot off.

Question 25

How do you manage diuresis during ECMO?
What if they are not making much urine despite diuresis?

Answer 25

Since most patients are fluid overloaded when ECMO is initiated, aggressive diuresis is warranted once the patient is stable on ECMO. Ultrafiltration can be easily added to the ECMO circuit if patients are unable to produce sufficient urine for diuresis.

Question 26

How do you monitor and manage LV contractility during ECMO?
Why is this important?

Answer 26

LV output must be monitored during VA ECMO LVEF may worsen.
The cause is multifactorial - insufficient unloading of the distended left ventricle due to ongoing blood flow to the LV from the bronchial circulation and RV.
LV output can be closely monitored - identify pulsatility in the arterial line’s waveform and frequent echo.
Interventions - inotropes (eg, dobutamine, milrinone) to increase contractility, IABP to reduce afterload and facilitate left ventricular output.
Immediate LV decompression is essential to avoid pulmonary hemorrhage if LVEF cannot be maintained despite IABP and inotropes - percutaneous transatrial balloon septostomy or LV/LA drainage catheter.

Question 27

How do you wean from VV ECMO?

Answer 27

One or more trials of taking the patient off ECMO should be performed prior to discontinuing ECMO permanently.

VV ECMO trials are performed by eliminating all countercurrent sweep gas through the oxygenator. Extracorporeal blood flow remains constant, but gas transfer does not occur. Patients are observed for several hours, during which the ventilator settings that are necessary to maintain adequate oxygenation and ventilation off ECMO are determined.

Question 28

How do you wean from VA ECMO?

Answer 28

One or more trials of taking the patient off ECMO should be performed prior to discontinuing ECMO permanently.

VA ECMO trials require temporary clamping of both the drainage and infusion lines, while allowing the ECMO circuit to circulate through a bridge between the arterial and venous limbs. This prevents thrombosis of stagnant blood within the ECMO circuit. In addition, the arterial and venous lines should be flushed continuously with heparinized saline or intermittently with heparinized blood from the circuit. VA ECMO trials are generally shorter in duration than VV ECMO trials because of the higher risk of thrombus formation.

Once the decision has been made to discontinue ECMO, the cannulas are removed. Hemostasis is achieved by compressing the insertion site. For patients who received VA ECMO, at least thirty minutes of compression is required for the arterial site.

Question 29

How do you reduce likelihood of bleeding complications on ECMO?

Answer 29

Meticulous surgical technique, maintaining platelet counts greater than 50,000/mm3, and maintaining the target activated clotting time (ACT) reduce the likelihood of bleeding.

Question 30

What are some interventions when bleeding on ECMO?

Answer 30

Bleeding from surgical wounds often requires prompt exploration with liberal use of electrocautery. Hemorrhage into body cavities (eg, abdomen, pleural space) may require surgical exploration to achieve hemostasis, after which vacuum-assisted closure is recommended because it allows removal and measurement of the blood. Plasminogen inhibitors (eg, aminocaproic acid) can be infused or heparin can be discontinued for several hours, but these actions may increase the risk of circuit thrombosis.
Factor VII is a last resort.

Question 31

What ECMO configuration predisposes the most to thromboembolism?
Is VA or VV ECMO affected more by this complication?

Answer 31

femorofemoral cannulae
impact is greater with venoarterial (VA) ECMO than venovenous (VV) ECMO because infusion is into the systemic circulation

Question 32

How do you manage HIT in ECMO?

Answer 32

if suspicious, send off the anti-PF4 lab; heparin infusion should be replaced by a non-heparin anticoagulant, usually argatroban

Question 33

For VA ECMO, what complication is the pt at risk of if LVEF is poor and LA pressure is high?
How do you manage?

Answer 33

Pulmonary edema and hemorrhage can occur in patients who have no left ventricular (LV) emptying during VA ECMO. Edema occurs when the left atrial (LA) pressure exceeds 25 mmHg. It is treated by venting the LA or LV.

Question 34

What is another complication of poor LVEF during VA ECMO?
What is the pathogenesis of this complication?

Answer 34

Cardiac thrombosis – There is retrograde blood flow in the ascending aorta whenever the femoral artery and vein are used for VA ECMO. Stasis of the blood can occur if left ventricular output is not maintained, which may result in thrombosis.

Question 35

Is it possible to have coronary ischemia in VA ECMO? How?
How do you monitor and manage this?

Answer 35

Coronary or cerebral hypoxia – During VA ECMO, fully saturated blood infused into the femoral artery from the ECMO circuit will preferentially perfuse the lower extremities and the abdominal viscera. Blood ejected from the heart will selectively perfuse the heart, brain, and upper extremities. As a result, the oxyhemoglobin saturation of the blood perfusing the lower extremities and abdominal viscera may be substantially higher than that perfusing the heart, brain, and upper extremities.

Cardiac and cerebral hypoxia could exist and be unrecognized if oxygenation is monitored using only blood from the lower extremity.

To avoid this complication, arterial oxyhemoglobin saturation should be monitored in the right upper extremity. Poor arterial oxyhemoglobin saturation measured from the upper extremity is corrected by infusing some oxygenated blood into the right atrium (called VA-V access).

Question 36

Describe the different types of multi-cannula ECMO circuit configurations (femoral arterial return). What scenarios might they be useful?

Answer 36

VVA - bicaval drainage into femoral infusion (use if single cannula not providing drainage to the other system; superior or inferior congestion).
VAV - RA drainage with more distal RA infusion in addition femoral infusion (send some oxygenated blood through to the LVOT in pts w/ low radial arterial oxygenation despite good femoral infusion flow and lower body oxygenation).
VVAV - SVC and femoral drainage with femoral and RA infusion (VAV circuit causes poor SVC drainage, so you drain SVC and infuse RA via femoral, but now IVC has poor drainage, so the contralateral CFV is cannulated and drained).
VVVA - SVC, IVC, contralateral CFV drainage with femoral infusion (your VVA setup causes poor contralateral CFV drainage, so you insert another cannula to drain it).

Question 37

You go on VA ECMO via femorals, but notice head and arm swelling. Saturations to the arm and lower extremity are fine. What do you do?

Answer 37

VVA - add RIJ in addition to the CFV for drainage of the SVC and IVC. Continue femoral infusion since the saturations in the upper and lower arterial systems are fine.

Question 38

You go on VA ECMO via femorals, but poor saturations to the arm despite lower extremity saturations being ok. What do you do?

Answer 38

VAV - RA drainage with more distal RA infusion in addition to femoral infusion (send some oxygenated blood through to the LVOT in pts w/ low radial arterial oxygenation despite good femoral infusion flow and lower body oxygenation).

Question 39

You go on VA ECMO via femorals, but poor saturations to the arm despite lower extremity saturations being ok.
You then go on VAV with CFV drainage into RIJ RA infusion and CFA infusion. Head and arms start to swell. What do you do?

Answer 39

VVAV - SVC and femoral drainage with femoral and RA infusion. You have to improve SVC drainage (treat head swelling) in addition to IVC drainage, but you still need LVOT to get oxygenated blood (known mismatch in measured radial and femoral oxygenation).

Question 40

You go on VA ECMO via RIJ and CFA, but notice lower extremity swelling and rising LFTs, saturations to the arm and lower extremity are fine.
You start VVA ECMO to improve drainage via RIJ and CFV (now added) for drainage, and CFA infusion.
The contralateral lower extremity remains swollen, and there are not DVTs.
What can you do?

Answer 40

VVVA - SVC, IVC, contralateral CFV drainage with femoral infusion (your VVA setup causes poor contralateral CFV drainage, so you insert another cannula to drain it).

Question 41

You go on VA ECMO via femorals, but poor saturations to the arm despite lower extremity saturations being ok.
You then go on VAV with CFV drainage into RIJ RA infusion and CFA infusion. Head and arms start to swell. What do you do?

Answer 41

VVAV - SVC and femoral drainage with femoral and RA infusion. You have to improve SVC drainage (treat head swelling) in addition to IVC drainage, but you still need LVOT to get oxygenated blood (known mismatch in measured radial and femoral oxygenation).

Question 42

In general, what is the principle for cannula sizing for VA ECMO?

Answer 42

use the smallest catheter for adequate CO for a given BSA
15 Fr arterial and 25F venous are usually minimum for adults

Question 43

If chugging occurs during ECMO, what is usually the next step?

Answer 43

add volume

Question 44

If you need to decrease flow or MAP for a patient on ECMO, what can you do to help them tolerate this lower flow state?

Answer 44

cool to mild hypothermia (32 - 34 C)

Question 45

What should you evaluate on the ipsilateral side of an SFA cannula for VA ECMO?
What if the evaluation is concerning?

Answer 45

DP/PT signal - may need 6 Fr distal perfusion cannula if no signal.

Question 46

What should an ECHO look like on ECMO?

Answer 46

heart should be fairly full, CVP and PAP should be normal or slightly elevated

Question 47

After initiating VA ECMO, forward flows seem good w/ lactate decreasing, but echo shows an LVEF that is poor with a distended and poorly kinetic LV. What should be considered?

Answer 47

The ventricle isn’t decompressing, and the heart is not ejecting.
Maximize ECMO drainage. Give inotropes. Use echo to eval for MR and pulm edema.
Can try IABP.
Place an LV vent. Can also use Impella to vent.
Can also use a tran-septal atrial puncture from the venous side or a passive 8Fr suction catheter trans-apically placed across the AV.

Question 48

In general, what do you need to wean from ECMO?
How do you do this?

Answer 48

Warmth, pulsatility, stable and perfusing rhythm, ventilating/oxygenating well
Echo should show EF >25% ideally.
Slowly wean to decrease flow by ~0.5L/min every 30 mins.
Min ECMO support achieved at 2L/min.
Afebrile, euvolemic, metabolic disturbances resolved.
Pulsatile waveform ~24 hrs.
MAPS >65 in absence of pressors/inotropes.
Wean sweep, adjust vent settings (if intubated).

Question 49

A patient has an ischemic limb following ECMO cannulation. It requires amputation. What is the likely mortality?

Answer 49

Near 100% in some series.
Do not wait on placing a distal perfusion catheter.

Question 50

What is the outer diameter of a 15 Fr ECMO cannula?

Answer 50

5mm.

Question 51

What is the workup for destination VAD therapy?

Answer 51

LHC and RHC (or CTA EKG gated coronary protocol if s/p CABG)
Echo
CT chest
Blood cultures, MRSA swab
Replace lines
Psych eval (for destination or transplant)
Op notes

Question 52

How do you manage oral heart failure meds preoperatively before LVAD placement?

Answer 52

Hold for 72 hrs.
ACE/ARBs cause vasoplegia intraoperatively.
Hold long acting beta blocker.