ECMO is briefly covered in a short summary elsewhere on this site. One of these days, a more detailed exploration of this fascinating modality will become available. In the meantime, an excellent troubleshooting guide is offered by LITFL, and brilliant videos accompany a practical guide based at the venerable merylandccproject.org. This page does not touch on the delicate art of manipulating the gas exchange via the ECMO circuit, because that is another vastly different topic area.
ECMO problems can be arbitrarily divided into two categories:
Routine ECMO problems
Catastrophic ECMO problems
With VA ECMO:
Troubleshooting the circuit
Troubleshooting the patient
In contrast to the "routine" problems, which are also potentially lifethreatening, catastrophic ECMO problems are those which typically result in death within seconds or minutes, in some sort of highly visually effective way (eg. whole blood volume emptying out of the patient and onto the floor, or entire venous circulation filling with air). Obviously, it would be helpful to have an immediate response to these problems all ready to go inside your head, just waiting for the opportunity.
By a more forgiving general definition, "pump failure" is the failure of the circuit pump to generate an adequate amount of flow though the circuit. Usually the pump is not at fault; rather, the venous access is to blame.
By a more specific definition, "pump failure" is what happens when the pump suddenly stops.
There are three ways this can happen:
One's first signs of this may be cardiac arrest (on VA ECMO) or profound hypoxia (on VV ECMO).
the Vinnies protocol mentions that this will be accompanied by "an unusual grinding noise and vibration of the pump head". This happens when the pump head is improperly inserted into the pump. The grinding noise is the sound of the centrifugal rota rapidly destroying itself, and this usually calls for urgent circuit replacement. Not only will there be poor flow or no flow, but whatever flow remains may be enriched by shredded red cells and little particles of the disintegrating rota.
How does one react to this?
This the complete obstruction of flow through the venous access circuit, resulting from the sudden collapse of the central vein around the access cannula tip. The result of this is a massively negative pressure in the access line, and failure of forward flow. Cardiac arrest or hypoxia may ensue.
The major contributor to this problem is actually the suction produced by the centrifugal pump.
Thus, you need to decrease the pump speed to decrease the suction (to about 1000 RPM).
Some flow should be restored by this manoeuvre.
One can then administer some fluid boluses to try to recondition the venous circulation, so as to prevent this from happening. The placement of an additional cannula may be called for on this occasion.
The accidental disconnection of the venous access cannula.
Immediate consequences of this:
Management consists of several simultanous measures:
That is easier said than done. While everything is being organised, the VV ECMO patient will be trying to oxygenate via their own faulty lungs (and clearly that wasn't working for them, otherwise they wouldn't be on ECMO). The VA patient will be substantially worse off, being in a state of cardiac arrest with CPR being their only means for forward flow.
The accidental disconnection of the arterial return cannula.
For the VA patient, this means cardiac arrest; for the VV patient, this means a sudden return to anaerobic metabolism. The disconnected cannula will also continue to empty the the patient's blood volume into the ambient bed space, at a rate equivalent to their cardiac output.
Thus, the immediate consequences are:
Management consists of several simultanous measures:
This term describes the breakdown of some random circuit component, be it tubing, oxygenator, pump head or what have you.
Depending on where this rupture is in relation to the pump, the circuit will either suck air into itself (resulting ultimately in mechanical pump failure and air embolism) or spray blood in a comically Pythonesque fashion from the fracture site (which is actually less rapidly lethal, and more obvious).
The solution, predictably, is to replace the circuit.
Management strategy suggested by the Vinnies protocol:
This tends to happen with circuit rupture or accidental access decannulation.
Again, either arrest (VA) or profound hypoxia (VV) will be the overall result.
Additionally, air embolism into the patient's circulation may still occur.
Unless the whole circuit is clotted up due to the blood-air interface, one might be able to de-air and reprime it. The arterial part of the circuit is clamped, and air is aspirated from the lines using a 60ml Luer lock syringe (the air can be guided to the three-way tap by manipulating the tubing, allowing to bubbles to percolate to the site of aspiration). The clamp can be taken off and pump restarted when the circuit is again full of blood.
This, in the VA ECMO patient, is a non issue. The circuit has already excluded the myocardium from any meaningful participation in the circulatory process. The monitor will be interesting to look at (VF, asystole, etc) but the VA circuit should provide enough flow to maintain organ perfusion. One can relax, have a coffee, and work out what caused the arrest in a calm and reflective fashion. The major risk from a totally immobile ventricle on VA ECMO is LV distension (see below) which takes a little while to develop.
In a VV patient, the sudden cessation of cardiac function will be rather disastrous, as venous access pressure will fail in the absence of cardiac output.
One should commence CPR according to the normal algorithm.
There is one notable difference with advanced life support in a VV ECMO patient. If ECMO flow can be established, the "A" and "B" parts of the algorithm can be safely neglected. The airway, as a conduit for gases, is superfluous if oxygenation is provided by the circuit. Additinally, the patient probably has some sort of massively gas-exchange-disabling lung problem, and trying to oxygenate them in a coventional fashion will probably meet with failure.
Thus, to get oxygen into the patient, one must reestablish satisfactory venous return to the access cannula. This can only be accomplished by CPR. Once good quality CPR is in progress, venous pressure should increase, allowing at least a low flow VV ECMO to continue (set the pump to 1000 RMP initially, and titrate up).
With a motionless arrested left venricle, the VA ECMO circuit acts as a total bypass of the pulmonary circulation. Under ideal circumstances, this means there is no flow in the pulmonary circulation.
However, that is not always the case; thus any pulmonary blood flow ends up distending this useless immobile ventricle.
If the LV is not ejecting blood into the aorta, pressure builds up in it, distending the mitral annulus and left atriu, and backfilling the pulmonary circulation until severe pulmonary oedema develops.
Not only that, but permanent LV damage can occur with such overdistension.
There is no conventient management strategy for this.
Options include the following:
This is the unfortunate consequence of having a motionless chamber with blood stasis within it.
Frequent TTE surveillance is recommended to detect this complication.
Unfortunately, there is little that can be done about it once it forms. Certainly, the presence of a large LV thrombus will frustrate any attempts to wean from VA ECMO once the reversible LV failure resolves. If the LV failure is irreversible, and ECMO is a bridge to transplant, then we can safely say that the LV thrombus is less of an issue, as the thrombus and the heart are both going in the bin.
Sidebotham, David. "Troubleshooting adult ECMO." The Journal of extra-corporeal technology 43.1 (2011): P27-32.
St Vincents Hospital, the House of ECMO, have an ECMO protocol for house staff. So does Westmead Hospital. These are not freely available online, and one must rely on friendly locals to supply them.
These protocols are particularly helpful, and much of the practical information included above is derived from these evidence-based guidelines.
The Royal Adelaide Hospital ICU ECMO Guidelines are also an excellent resource, and very much available online. I have used them more for the routine care of the ECMO patient.
Allen, Steve, et al. "A review of the fundamental principles and evidence base in the use of extracorporeal membrane oxygenation (ECMO) in critically ill adult patients." Journal of intensive care medicine 26.1 (2011): 13-26.
Foley, Paul J., et al. "Limb ischemia during femoral cannulation for cardiopulmonary support." Journal of vascular surgery 52.4 (2010): 850-853.
Oliver, William C. "Anticoagulation and coagulation management for ECMO."Seminars in cardiothoracic and vascular anesthesia. Vol. 13. No. 3. SAGE Publications, 2009.
Davies, Andrew, et al. "Extracorporeal membrane oxygenation for 2009 influenza A (H1N1) acute respiratory distress syndrome." JAMA: the journal of the American Medical Association 302.17 (2009): 1888-1895.
Eugene, J., et al. "Cardiac assist by extracorporeal membrane oxygenation with in-line left ventricular venting." ASAIO Journal 30.1 (1984): 98-102.
Seib, Paul M., et al. "Blade and balloon atrial septostomy for left heart decompression in patients with severe ventricular dysfunction on extracorporeal membrane oxygenation." Catheterization and Cardiovascular Interventions 46.2 (1999): 179-186.
Russo, Claudio F., et al. "Veno-arterial extracorporeal membrane oxygenation using Levitronix centrifugal pump as bridge to decision for refractory cardiogenic shock." The Journal of thoracic and cardiovascular surgery 140.6 (2010): 1416-1421.
Platts, David Gerard, et al. "The role of echocardiography in the management of patients supported by extracorporeal membrane oxygenation." Journal of the American Society of Echocardiography 25.2 (2012): 131-141.