Complications and Troubleshooting

Several complications of ECLS and ECPR can occur during the process of initiating, maintaining, and weaning bypass. However, one should keep in mind that the alternative to ECPR is death. Complications that occur during, or after, ECPR can be broken down into:

Primary complications: those that occur during the process of initiating bypass, and
Secondary complications: those that develop in response to the pathophysiology of extracorporeal circulation. Complications are outlined here:

Primary complications

typically involve issues with cannulation of the femoral vessels. The most common issue experienced in the ED is difficulty in cannulating the femoral artery in a pulseless patient. During cardiac arrest, the pressure in the venous and arterial systems equalizes, and the femoral vein becomes very large in comparison to the artery. Even under ultrasound guidance, cannulation of the femoral artery presents a challenge, especially with ongoing chest compressions. For this reason, we try to anticipate a potential ECPR candidate before full arrest occurs and establish early arterial access.

Perforations, tears, and rupture of the femoral vessels, vena cava, and aorta have all been reported. In patients who survive, those vessels often require surgical repair. Bleeding from cannulas that are in the correct position can also occur. Kurusz reported cannula-related bleeding rates of 4% to 14%. Explanations include multiple punctures of the vessels during attempted cannulation, anticoagulation with heparin, decreased platelet function, and hepatic dysfunction.

Secondary complications

Secondary complications are those that develop after successful establishment of bypass. The main cannula-related secondary complication is ischemia of the limb ipsilateral to the arterial cannula. This is remedied by placement of an additional, smaller femoral artery catheter, which allows perfusion of the limb distal to the ECLS cannula.

Anticoagulation is necessary to prevent clotting associated with large caliber cannulation of the great vessels but may lead to hemorrhage complications. Hemorrhage in the gastrointestinal tract or brain is particularly problematic.

The effect of ECLS on the right and left ventricle is worth discussion. The ECLS circuit efficiently offloads the right ventricle as blood is drawn from the right atrial inlet and into the pump. However, retrograde flow of blood towards the left ventricle may cause increased left ventricular afterload, especially if ventricular ejection is unable to overcome this pressure gradient. If uncorrected, this results in progressive left ventricular dilation, increased pulmonary venous congestion, and hemorrhagic pulmonary edema. To mitigate this, inotropic support is useful, intra-aortic balloon pumps may be beneficial, and any ventricular dysrhythmias should be cardioverted. When these measures fail, it may be necessary to surgically decompress the left ventricle (via several possible techniques) to preserve function.

Common Problems and Specific Fixes:

1. Pump Chatter

Chatter, or rattling, of the circuit and ECLS lines and can occur at any time after the pump is running. This is typically caused by a mismatch between circuit volume and pump circuit pressure resulting in turbulence in the system. Oversimplified, think of this like your household plumbing rattling when you first turn on a faucet “full blast” before there is enough water pressure in the system. The pipes rattle. You are demanding a higher pressure than can be delivered with the volume in the system and you get “chatter.”

Fix: temporarily lower the RPMs (by turning the dial on the pump head) until chattering is minimized. Then, volume replete your patient, either with crystalloid or blood depending on the situation. Oh, and make sure your patient isn’t losing volume somewhere – like hemorrhage from one of those fat femoral lines in the groin! Usually administration of 500-1000 ml of volume de jour will fix the problem.

Pump chatter can also be caused by cannula malposition and kinking. Running the length of the circuit and cannulae to make sure all is intact should be a first step.

2. Differential Hypoxemia during VA ECMO

A combination of a femoral return catheter, retained native heart function, but poor pulmonary status can lead to this condition. Blood from the patients native circulation will be pumped into the aortic arch and it will be poorly oxygenated because of the patients pulmonary issues. Obviously brain perfusion is our foremost goal in a critically ill patient, so this situation obviates the benefits of ECMO. The pulse ox probe should be on right arm or forehead to assess whether the patient’s poor native lung function in combination with good native cardiac function is leading to hypoxemia of brain. One solution is to place a venous return catheter in the IJ to allow oxygenated blood to flow through the heart (VAV ECMO)

3. Left Ventricular Overload

This is a complex problem that occurs as a secondary complication. This typically occurs with aortic valve dysfunction or when a patient is on pump for a prolonged period of time. The retrograde flow of the ECLS pump can overwhelm a failing left ventricle (LV). A poorly functioning LV becomes a conduit for retrograde flow and fluid backs up into the LA. Increased LV pressure will allow retrograde flow into the pulmonary veins resulting in pulmonary hemorrhage. This is bad. Urgent intervention is needed. You need to offload the left ventricle:

Fixes: