ECMO (Extracorporeal Membrane Oxygenation) 

ECMO (Extracorporeal Membrane Oxygenation): A Bridge to the Heart and Lung Transplant Essay

ECMO (Extracorporeal Membrane Oxygenation) is a lifesaving procedure, which can temporarily replace the function of the patient’s heart and/or lungs. It can be indicated as a bridge to the heart and lung transplant for patients with extensive cardiac and pulmonary dysfunction who require a transplant of both organs but cannot survive waiting for a transplant.

ECMO indications as a bridge to the heart and lung transplant are determined by patients’ conditions;

they require transplant of both organs with no time for surviving waiting for a transplant.

ECMO (Extracorporeal Membrane Oxygenation): What Is It?

ECMO is a machine, which can partially replace functions of the heart and/or lungs, depending on the indications:

VA-ECMO (Veno-Arterial):

VA-ECMO is indicated when there is a need to provide support of both the heart and the lungs. The machine pumps the blood from the venous system (typically, from a large vein in the leg or in the neck) through the oxygenator (where it is oxygenated) and returns it to the arterial system (typically, in a large artery in the leg or in the neck). It is indicated for patients with both cardiac and pulmonary insufficiency, for instance, as a bridge to the heart and lung transplant.

VV-ECMO (Veno-Venous):

VV-ECMO is indicated for patients, who require oxygenation but not for those requiring a transplant. The machine pumps venous blood (typically, from the femoral vein or the jugular vein), oxygenates it, and returns it into the venous system. It is indicated for patients with pulmonary insufficiency only. Nevertheless, for patients who require transplant of both lungs and the heart, VA-ECMO is indicated to provide temporary support of circulation and oxygenation.

Clinical indications for using ECMO as a bridge to heart and lung transplant

ECMO indications for bridging to heart and lung transplant include support for patients presenting with acute or end-stage failure of both the heart and the lungs, with depressed respiratory and cardiac functions, resulting in the inability to adequately oxygenate the organs; those patients would not survive without mechanical support before the heart and lung transplant. Therefore, ECMO indications as a bridge to the heart and lung transplant include patients with:

End-stage heart and respiratory failure:

Patients presenting with cardiogenic shock or end-stage heart failure complicated by severe respiratory failure may require assistance from the ECMO machine as a bridge to the heart and lung transplant. It can be indicated for patients with dilated cardiomyopathy, pulmonary hypertension, or insufficiency of the heart valves.

Myocardial infarction and Acute Respiratory Distress Syndrome:

Patients presenting with myocardial infarction complicated by Acute Respiratory Distress Syndrome may benefit from the use of ECMO as a bridge to the heart and lung transplant. Acute Respiratory Distress Syndrome is characterized by pulmonary edema with accumulation of fluid in the interstitial space or alveoli, leading to severe respiratory distress.

Post-cardiopulmonary bypass:

Some patients presenting with post-cardiopulmonary bypass syndrome may require the use of the ECMO machine as a bridge to heart and lung transplant. It can develop following certain cardiac surgeries, for instance, the coronary artery bypass grafting or valve replacement surgery. Patients with post-cardiopulmonary bypass syndrome can present with acute respiratory distress syndrome or cardiogenic shock.

Pulmonary hypertension and right heart failure:

Pulmonary hypertension often leads to right heart failure with decreased saturation; such patients can require bridging to heart and lung transplant with the use of the ECMO machine.

Pulmonary diseases with the development of right heart failure:

Chronic obstructive pulmonary disease, lung fibrosis or emphysema presenting with right heart failure may benefit from the use of ECMO as a bridge to heart and lung transplant.

Multiple system failure:

Multiple system failure presenting with pulmonary and cardiac involvement can require bridging to heart and lung transplant with the use of the ECMO machine.

ECMO for the Heart and Lung Transplant: How Does It Work?

For patients who require transplant of both the heart and the lungs, the ECMO machine will help them until the donor organs become available; it is typically placed via large-caliber catheters in the femoral vein, femoral artery, and/or jugular vein. Following its placement, the patient’s blood is pumped through the machine, where it is oxygenated and returned to the patient’s circulation.

Therefore, VA-ECMO (Veno-Arterial) is indicated for patients who require support of both the heart and the lungs; the machine takes over their functions, partially. The VA-ECMO machine essentially circulates oxygenated blood around the body, thus “replacing” the work of the heart and the lungs, partially.

Heart and Lung Support

The VA-ECMO machine replaces the work of the heart and the lungs, thus “allowing” them to rest. In case of heart failure, it is “allowed” to rest; the same goes for the lungs when they are unable to oxygenate the blood sufficiently.

Monitoring and adjusting the ECMO

Patients who require the ECMO machine typically need close monitoring and adjustment of it in order to ensure that the oxygenation and circulation are adequate. The health care providers will also administer various medications to the patient in order to prevent potential complications related to the use of the machine.

Anticoagulation Therapy

Typically, patients who are placed on the ECMO machine are placed on anticoagulation therapy in order to prevent clot formation; however, this therapy might contribute to the development of hemorrhagic complications,

Benefits of using ECMO as a bridge to heart and lung transplant

Life support:

ECMO will typically help sustain patients who would not survive otherwise.

Time for the patient to stabilize:

ECMO provides temporary support, which allows the patient to stabilize and become an optimal candidate for further treatment, including the heart and lung transplant.

Protection of organs:

ECMO helps to ensure that the patient’s organs receive an adequate oxygenation and blood circulation; that way, it protects the vital organs from hypoxia.

Lung and Heart rest:

ECMO gives rest to the heart and lungs, thus helping them to recover partially during the period of hospitalization if the underlying disease allows it.

A bridge to transplant:

As described above, ECMO can be indicated as a bridge to the heart and lung transplant; thus, it gives an additional chance for those patients who need both organs transplantation.

Risks and complications of using ECMO

Despite being a vital intervention, the use of the ECMO machine is associated with numerous risks and potential complications, among which the most common are:

Infection:

Due to its invasiveness and close supervision, there is a risk of developing nosocomial infections; hence, one should be aware that the procedure might lead to bacteremia or pneumonia.

Bleeding:

Since the patients on ECMO are typically placed on anticoagulation therapy, there is a risk of bleeding both at the cannula sites and systemically.

Organ dysfunction:

Prolonged use of the machine might lead to renal, hepatic or neurological dysfunction.

Blood clots:

The formation of clots within the machine might lead to its malfunction.

Vascular trauma or malfunctions:

Both vascular trauma and malfunction of the cannulas might lead to bleeding or malfunction of the ECMO machine.

Right heart failure:

Sometimes, the patients on VA-ECMO can present with complications associated with the right heart failure.

Complications associated with the machine:

Due to its complexity, the machine might malfunction and require immediate intervention.

Post-ECMO and Heart-Lung Transplant Surgery

When the donor heart and lungs become available, the patient will undergo heart and lung transplant surgery. Following the transplant, the patient will be discharged from the hospital with post-transplant follow-up care. Furthermore, following the transplant, the patients typically enter a rehabilitation facility in order to adjust to their new life with the donor heart and lungs.

Prognosis and survival rates

Although both ECMO and heart-lung transplant surgery interventions are associated with considerable mortality risks, the survival rates for patients who survive both are positive. The survival rates depend on the patients’ general condition before the transplant, their age, and the functionality of the transplanted organs after the surgery.

Survival to transplant: Survival rates to transplant are relatively high, meaning that the majority of patients who are placed on the ECMO machine as a bridge to heart and lung transplant survive to actually undergo the surgery.

Generally, the one-year survival rate after heart-lung transplant surgery is 70-80%, while the five-year survival rate is 50-60%.

Conclusion

ECMO is a procedure, which is crucial for patients who need a heart and lung transplant, but cannot survive without mechanical support before receiving a transplant. The machine can be indicated as a bridge to the heart and lung transplant for patients with extensive cardiac and pulmonary dysfunction; it takes over the functions of the heart and lungs thus, giving them a rest and helping the patient to stabilize before the transplant. Nevertheless, despite the numerous benefits of the procedure, it is essential to remember that ECMO is associated with numerous risks and complications. Overall, the machine provides temporary circulatory and respiratory support for patients with severe pulmonary and cardiac failure, and sustains their vital organs until the transplant can be performed.