ECMO Podcast

Space: StayCurrentMD Published: 2019-10-18

Topic overview

This episode is a review of pediatric ECMO with Dr. Samir Gadepalli, Dr. Alejandra Casar Berazaluce, and Dr. Todd Ponsky.

Intro and outro tracks are adapted from "I dunno" by grapes, featuring J Lang, Morusque. Artist URL: ccmixter.org/files/grapes/16626

Indications for ECMO:

Respiratory

Increasing ventilatory requirements that risk barotrauma
P to F ratio: how much PaO2 you get for an amount of FiO2 delivered
Oxygen Index = (Mean Airway Pressure * FiO2 * 100) / PaO2

OI 4-8: Mild lung injury
OI 8-16: Moderate
OI >16: Severe, with around 40% mortality

OI >25: Strongly consider ECMO
OI >40: ECMO

Consider heart function and adjunct therapies like prone positioning and oscillator or other ventilator settings.

In pulmonary hypertension, a trial of NO may be used.

Considerations:

Circuit availability
ECMO capabilities
Transport capabilities

If I am a trainee in the middle of the night, what do I need to know for a respiratory ECMO consult?

OI
Echo

To evaluate hemodynamics, what the underlying heart function is.

If heart function is only affected due to high ventilator requirements, different story.
RV dilation: may trial NO to see if it reduces pressures.
LV dilation: more concerning, maybe VV ECMO would be insufficient, even if first choice for respiratory failure ECMO.

Primarily looking for: adequate ventilation on both lung fields, pneumothorax.

If there's a collapsed segment, bronchoscopy may be useful getting rid of mucus plugs.

Pressors

To decide how advanced their disease process is.

Underlying disease

Pneumonia, aspiration, sepsis?

Location of central access

Where am I going to cannulate?

Head ultrasound?

If there is time, it may be useful for prognostic value, especially if young enough. Hemorrhage grade 2 or lower, not a contraindication, ok to go on ECMO. If sutures are already

Grade 3 intracerebral hemorrhage would not be a great candidate for ECMO

Other contraindications:

Active bleeding would be a consideration.
Historically, long ECMO runs (longer than a week or two) would be strong consideration against ECMO. Now, it is considered higher risk but still performed if it is a reasonable option. Lungs may take longer to recover, but we are seeing success in long remodeling for respiratory ECMO.
Extreme prematurity, or prematurity under 30 weeks.
Patient under 1,200 grams.
Adequate size cannula not available.
Previous ECMO at that site may make it challenging.
Good time to set up arterial lines or other procedures before heparinization (chest tubes, Foleys, etc).

Sepsis

ECMO does a fantastic job for oxygenation and ventilation (functions of the lung); however, it is not great at maintaining vascular resistance.
In patients with low pressures, especially low diastolic, you may require flows over 150 per kilo, larger cannulas (including considering central cannulation), and consideration of VA ECMO.
More hesitation to go on ECMO for sepsis, attempt other therapies. Although you can replace the pump function, it is hard to replace tone.

eCPR

Adjunct to bystander CPR.
It's an evolving field.
Great neurologic outcomes in centers with established experience.
Michigan does cardiac eCPR for known patients after cardiac surgery, hypothermic patients put in VA during rewarming.
Pre-hospital is too challenging at this time, although adult pre-hospital is more advanced.

PODCAST: Congenital Diaphragmatic Hernia with Dr. Charlie Stolar. Stay Current in Pediatric Surgery. GlobalCastMD. January 13, 2017.

http://bit.ly/2OWPJ8m

ECMO Modalities:

VV is more than adequate for respiratory failure.
VA in left sided heart disfunction, poor cardiac function with high dose pressors.

VA is an alternative for inadequate VV.

ELSO neurologic injury:

Stroke, death, seizures, brain death.

Highest rate in neonates, who have the highest rate of VA use.

Rate of neurologic injury decreases with age.

Risk of neuro injury 21% with VA and 16% with VV.
Risk of stroke is 5.1% for VA and 3.5% for VV.

Cannulation strategies:

Neonate with respiratory failure and adequate cardiac function:

VV modality
Right neck approach
Cut down open technique, ligate the internal jugular vein, and place an OriGen cannula.

Adolescent with respiratory failure and adequate cardiac function:

VV modality
Avalon cannula under fluoroscopy AND echocardiography guidance.

Can do bedside but prefer OR due to availability of rescue resources.

Use ultrasound to access internal jugular vein, use a micropuncture needle to place a straight wire and then exchange for a longer wire from the Avalon kit. If unable to advance to IVC, place KMP catheter with a bend in the end to thread it. The stiffest possible wire will prevent it from flipping out as advancing the Avalon. Dilate over the wire and place the catheter.

As soon as catheter in IVC, heparinize at 100 per kilo.

In position, use contrast through the reinfusion limb to place in RA above the diaphragm, above the IVC/RA junction, so that even when edema pulls catheter up it remains in position.

On fluoroscopy, the middle hepatic vein and IVC overlay; echo may help delineate this better.

Percutaneous vs open approach:

Percutaneous is acceptable; the problem is you have to know where the tip of your dilator is at all times.
Since the dilators don't come with good markers, you are at a higher risk for perforation if doing it blindly.
Ultrasound and/or fluoroscopy are needed to track appropriately, so an open approach may be simpler in this population.
Percutaneous also has the disadvantage of snug fit of the cannulas with tiny neonatal veins

OriGen vs Avalon cannulas:

OriGen has two lumens and both end in SVC or RA junction. Distal lumen (reperfusion) is about RA, around the tricuspid; proximal at SVC. This is likely adequate venous return for someone who doesn't walk, or under 30 kilos. Capturing the most deoxygenated blood is the goal, and someone not walking and NPO has most of their blood flow from the brain and heart through the SVC; IVC contribution is quite low.
Avalon cannulas have a bicaval pathway with three holes. One in SVC and one in IVC for venous return, and a middle hole in the right atrium for reperfusion.

In long cannulas, the holes are further apart, which mismatches for neonates. Under 19Fr, the distances are very short and the likelihood of flipping out of position is greater. Flipping from the retrohepatic vena cava in neonates to the right atrium causes recirculation of flow, leading to complications in ECMO.

Jarboe MD, et al, Avalon catheters in pediatric patients requiring ECMO: Placement and migration problems, J Pediatr Surg (2017).

http://bit.ly/2LwsboL

For adolescents, you do want to capture the IVC blood. Avalon gives a secure placement to have patients move around, this allows for early mobility. Longer segments and reinforcements help the cannula stay in place and patent.

Single vs dual site cannulation:

Dual is typically femoral and internal jugular, which means to open cutdowns in an emergency situation.
Femoral access is difficult in the neonate.

Cannulation for VA ECMO:

Going away from femoral access due to risks:

16% risk of limb loss or lower extremity injury

Reperfusion cannula:

Antegrade catheter

May flip into the profunda and not have adequate perfusion to SFA

Catheter to PT

If diseased segment of outflow vessels, compromise due to PT in use.

As heart function recovers, North-South syndrome develops, where less oxygenated blood enters the brain and more oxygenated blood is delivered to the lower extremities.

Most people end up replacing an IJ catheter to reperfuse in this scenario.

Downside for percutaneous cannulation is risk of shear injury to intima and media and thromboembolism.
Michigan not repairing carotids after decannulation, as it is associated with increased risk of stroke and neurologic injury.

Other hardware for ECMO:

Centrifugal pumps preferred; some centers still using rollers in neonates.

Roller pump associated to higher negative pressures for drainage and need to place the patient higher for gravity aid; require bladder to avoid cavitation (pulling air out of blood). Roller pumps tend to be less efficient.
Centrifugal pumps have been associated with hemolysis; this is related to RPM. As long as they are kept lower, the risk is minimized.

Suggestion: add a low dose pressor instead of increasing RPM.

Daily monitoring:

Flow:

Neonate on full support (VA), approx. 100 per kilo.
If well above, check SVO2 to see if too much.
Sepsis may require higher.
On VV ECMO, closer to 120 per kilo.

Sweep:

This means the sweep gas; it means how quickly it removes CO2.
On someone ready to come off, sweep is close to 0.1 per kilo.
Helps determine how much ventilation is provided by ECMO circuit vs lungs.

Heparin level:

Still the mainstay but likely to switch to direct thrombin inhibitors.
Michigan uses ACT, some use anti-Xa.

With bleeding concern, keep lower at 170-180.
No concern for bleeding, keep at 210-230.

If heparin drip requirements are high without reaching high ACT, this could be antithrombin-3 deficiency.

Replacement is expensive.
If early and volume depleted, use plasma.

If heparin is turned down and ACT remains high, likely not representative = get anti-Xa.

Routine blood cultures (debated):

Signs of sepsis may be masked well on ECMO.

Head ultrasounds:

2-3x per week in neonates, less frequently in children; not useful with closed suture lines.

CXR:

Ventilator on rest settings until signs of lung aeration.

When is the patient ready to come off of ECMO?

CXR looks good.

Adequate lung volumes, ventilating at 4-6cc per kilo.
Modest ventilator settings: peak pressures below 30, low concern for lung injury.

If no rush due to complications, be conservative coming off.

VV makes it easy to trial every day by removing sweep gas.
VA is harder to trial as it requires clamping of circuit and blood gases.

Usually less than 4hrs to reduce circuit injury and clotting with systemic embolization.

When resting lungs, FiO2 is close to room air.

If you turn to 100 really fast and O2 sat hits 100%, likely ready to come off.

Dropping flows down to 15 per kilo and measuring oxygenation also helps see how you are doing.

How do you come off of ECMO?

You can run heparin through the cannulas but leave them in place if high concern for failure.

Remove sweep and reassess function.

Clamping trials (VA):

Reassess every 15min to 1hr to evaluate native function.
Flash (unclamp and reclamp) to avoid clots.

Decannulation:

Percutaneous: pull out cannula and hold pressure; typically, silk purse-string suture at skin level.
Open: requires cutdown and ligation of distal vessel.

Procedures on ECMO:

Avoid at all costs: IVs, chest tubes, etc.

Close to coming off it may be a good time to try.
Chest tube placements: close to intercostal.

Bronchoscopy: useful for mucus plugging and blood suctioning from airway.

Outcomes:

What is the tradeoff?

Consider inherent mortality before being put on ECMO.

ARDS and progressive respiratory failure:

ECMO is a good option.

Take home messages:

If somebody is sick, don't be afraid to put them on ECMO.
Call for help early.
Oxygenation Index (OI) is a good measure of respiratory failure.
Be careful using Avalon catheters, ensure adequate visualization of the tip using fluoroscopy and echocardiography.