ECMO is a complex procedure performed on critically ill patients, thus have high potential for complication.
Large negative pressure generated with the centrifugal pumps can lead to air entrainment and significant air embolism. A major obstruction in the circuit can also force the gas out solution causing gas embolism. This complication, though life threatening, is rare and occurs in fewer than 2% of adult ECMO runs.16
Blood clots: Blood clots can occur at multiple sites in the ECMO circuit. Clot in the pump head usually results in change in sound of the pump and rising plasma hemoglobin. A clot in the oxygenator can result in increasing pressure gradient along with fall in post oxygenator PO2 and increasing sweep gas needed to maintain PaCO2. Other markers such as increasing d-dimers or fibrin degradation products can also suggest clot formation.
Loss of circuit flow: Loss or reduced flow is most commonly caused by hypovolemia. Other causes such obstructive shock from cardiac tamponade or tension pneumothorax and malpositioned cannula can also decrease the flow. With a roller pump, a decreased flow can lead to slowing or stopping of the pump. In ECMO devices with a centrifugal pump, a decreased flow can lead to increased negative which can progress to suck down at the drainage cannula eventually causing loss of circuit flow.
Circuit failure or breakage: As the name sounds, this complication may lead to a catastrophic complication. Bedside staff trained to check circuit integrity and to react promptly in the case of acute failure can prevent this problem.
Hemodynamic instability: Circuit flows above 7 L/min are rarely possible even with the optimal cannula. In patients on ECMO support, severe sepsis can lead to significant hypotension as it normally would lead to increase in cardiac output. Left ventricular (LV) distension can occur in patients on VA ECMO especially in patients with mitral or aortic regurgitation, which can lead to pulmonary edema. Increasing pump flow may be helpful in such situations.
Hypoxemia: Upper body hypoxemia can occur in VA ECMO patients with significant LV ejection and impaired lung function. This situation typically occurs when return cannula is placed in lower extremity arteries. Detecting higher saturation in lower extremity compared to upper extremity diagnosis this problem.
Infections: Infective complications related to access sites, indwelling lines or primary pathology can occur. Of note, signs of sepsis may be completely evident; in particular, fever may be absent due to control of temperature via heat exchanger. Thus, any evidence of deteriorating hemodynamics or rising white cell count should be taken seriously. Strict aseptic precautions need to be taken during this process.
Bleeding: Bleeding, in particular from the surgical site, is common during ECMO. In one series, approximately 31.4% patients developed cannulation site bleeding and 26.7% developed surgical site bleeding.17 Other less common but potentially more serious bleedings could be gastrointestinal and intracranial bleeding which were 7% and just fewer than 3% in same series respectively. Most important mechanism of dealing with this complication is prevention. All unnecessary procedures should be avoided as much as possible while patient is on ECMO.