Veno-Veno-Arterial ECMO (VVA ECMO): Combined Cardiopulmonary and Respiratory Support Essay

Veno-veno-arterial (VVA) extracorporeal membrane oxygenation (ECMO) is a hybrid form of veno-venous (VV) and veno-arterial (VA) that has been utilized for patients who have experienced cardiorespiratory issues. It is considered a more advanced type of ECMO that is mainly used for post-transplant patients presenting with respiratory failure and circulatory problems or those with extreme cardiac and respiratory insufficiencies. VVA ECMO is indicated for patients with severe right heart failure after lung transplantation, primary graft dysfunction (PGD), and multiple-organ failure.

Indications for VVA ECMO After Lung Transplantation
The indications for using VVA ECMO for post-lung transplant patients include respiratory failure alongside cardiovascular collapse. In addition, the respiratory failure that occurs after lung transplant surgery usually accompanies right heart dysfunction. Thus, VVA ECMO can be used in the following conditions:

Primary Graft Dysfunction (PGD) and Right Heart Failure:
PGD is the major cause of respiratory failure after lung transplantation, and one of the treatment options is VVA ECMO. PGD can result in profound hypoxemia, pulmonary edema, and impaired gas exchange. Besides, this condition can lead to right heart failure due to pulmonary hypertension in cases of graft malfunction, pulmonary vasculature insufficiency, or inadequate response to VV ECMO.

Severe Right Heart Dysfunction
Following lung transplantation, right heart failure could occur due to pulmonary hypertension or pulmonary embolism. Such cases require biventricular support; thus, VA or VVA ECMO should be used. In patients with right ventricular (RV) failure, the venous cannula can reduce RV afterload to facilitate the return of blood to the heart.

Severe Respiratory Failure with Hypoxia
The indication for VVA ECMO can also include severe respiratory failure associated with hypoxia that cannot be managed by standard medical treatment and high-dose mechanical ventilation. One of the common reasons for respiratory failure is acute rejection of allograft, which can also lead to circulatory failure. VVA ECMO can help maintain the oxygenation of the body; at the same time, it can remove carbon dioxide and protect the transplanted lung from the harmful effects of high mechanical ventilation.

Rejection and Infection
One of the major complications following lung transplantation is acute rejection or infection, which can lead to severe respiratory and cardiovascular failure. Such cases require respiratory and circulatory support provided by VVA ECMO, which will allow the medical team to eliminate the cause of the second respiratory failure (acute rejection or infection).

Multi-Organ Failure Following Lung Transplant
Patients who have undergone lung transplantation can also develop multiple-organ failure because of the development of infection, ischemic injury, or severe rejection. In these cases, the indication for using VVA ECMO will be respiratory and circulatory failure associated with lung insufficiency and the inability of the circulatory system to support the functioning of other systems and organs.

Failure to Wean from the Ventilator
Sometimes, transplant recipients fail to wean from the ventilator following lung transplantation, even if their lungs are not severely injured. This situation can occur when patients develop cardiac dysfunction or other diseases that prevent them from being discharged from the intensive care unit. In such cases, VVA ECMO can be used to support the patients’ cardiac and pulmonary functions.

How VVA ECMO Works
In VVA ECMO, cannulas are inserted into a vein and an artery to provide respiratory and circulatory support for the patient. The venous cannula is usually placed in the femoral, internal jugular, or subclavian vein. The venous cannula facilitates blood drainage from the right atrium into the ECMO circuit. The oxygenator in the ECMO circuit oxygenates the blood and removes the carbon dioxide from it, thus, providing respiratory support for the patient.

The arterial cannula is usually inserted into the femoral or subclavian artery to return the oxygenated blood from the ECMO circuit into the patient’s circulation system. Oxygenated blood that has been returned to the circulation system via the arterial cannula provides circulatory support for the patient. The venous circuit of VVA ECMO provides gas exchange, whereas the arterial circuit helps to increase the cardiac output of the patients.

In a hybrid ECMO circuit, the right heart can be supported as long as the right ventricular function is intact, and the pulmonary vascular resistance is decreased. Besides, VVA ECMO can be used in patients with severe right heart failure following lung transplantation.

When using VVA ECMO, the patients still require positive pressure mechanical ventilation with lower tidal volumes and pressures as much as possible. This is essential to avoid ventilator-induced lung injury (VILI) in the transplanted lungs, which cannot withstand the high pressures and volumes of traditional mechanical ventilation. Moreover, the VVA ECMO circuit requires continuous management to ensure the optimal blood circulation and gas exchange in the patient. The gas exchange will depend on the flow rate, oxygenation, and ventilation, so healthcare professionals should constantly monitor the patient’s hemodynamics and lung function. In addition, they should be prepared to wean the patient from the veno-veno-arterial ECMO, if necessary, or re-transplantation, if the patient’s condition does not improve.

Benefits of VVA ECMO for Post-Transplant Patients
Combined Treatment
The main advantage of VVA ECMO is that it provides combined respiratory and circulatory support to the patient. This is of utmost importance for post-lung transplant patients with respiratory failure and right heart dysfunction, those who suffer from PGD or acute rejection of the transplanted lung, as well as those with multiple-organ failure.

Lung and Heart Protection
One of the benefits of VVA ECMO for post-lung transplant patients is that it can provide temporary or short-term respiratory and circulatory support to the patient. In addition, VVA ECMO can prevent VILI, which is especially important for post-lung transplant patients whose lungs are fragile and sensitive to high pressures and volumes.

Besides, VVA ECMO can reduce right ventricular afterload and thus provide circulatory support for post-lung transplant patients with RV failure. The right ventricular support is essential for patients who have undergone lung transplantation to avoid right ventricular dilation.

Bridge to Recovery or Re-transplantation
VVA ECMO can also serve as a bridge to recovery for patients after lung transplantation or a bridge to re-transplantation for patients whose transplanted lungs have failed. In other words, it can be used as temporary circulatory and respiratory support for post-lung transplant patients who have developed acute rejection of the transplanted lung and require a period of immunosuppression.

Increased Chances of Survival Following Lung Transplant
One of the benefits of using VVA ECMO for post-lung transplant patients with respiratory failure is that it significantly increases the chances of survival following lung transplant.

Risks and Disadvantages of VVA ECMO in Post-Transplant Patients
Although VVA ECMO offers substantial benefits for patients who have undergone lung transplant and experience respiratory failure, it is also associated with several risks and disadvantages.

Bleeding
One of the major risks and disadvantages of VVA ECMO post-lung transplant is the development of bleeding after cannulation of the vein and artery in the patient’s upper torso. Severe bleeding can occur in different parts of the body, including cerebral hemorrhage, gastrointestinal bleeding, and bleeding at the sites of cannulation. The risk of developing complications, such as hemorrhage, increases due to the anticoagulant therapy used to prevent clot formation in the ECMO circuit. In addition, post-lung transplant patients are at higher risk of serious adverse outcomes, including severe central nervous system injury following ECMO therapy.

Infection
Post-lung transplant patients who undergo VVA ECMO are also at higher risk of developing infections. The reason for it is multiple immunosuppression, the presence of invasive devices in the bloodstream, and an extended hospital stay. The development of infection can lead to significant morbidity and mortality in patients who are already in fragile health conditions following lung transplantation.

Vascular Complications
Vascular injuries, including vessel trauma, aneurysms, and thrombosis, can also occur in patients who have undergone VVA ECMO. In addition, such patients are at higher risk of experiencing limb ischemia following the catheterization of the vein and artery.

Multi-Organ Failure
Multi-organ failure is another serious and potentially fatal complication of VVA ECMO in post-lung transplant patients. Patients undergoing VVA ECMO are at greater risk for developing acute kidney injury following the procedure. It is especially true for post-lung transplant patients who already suffer from severe kidney dysfunction.

Difficult Weaning from VVA ECMO
Weaning from VVA ECMO can be challenging and time-consuming, especially in patients with severe respiratory failure. A difficult weaning can result in increased health care costs, prolonged hospitalization, and high mortality rates due to the patient’s fragile health.

Prognosis
The prognosis for post-lung transplant patients undergoing VVA ECMO largely depends on whether they will be able to recover from the initial insult and whether they will be successfully weaned from the VVA ECMO. In addition, early intervention and the timely use of VVA ECMO can improve the prognosis for post-lung transplant patients with severe respiratory failure and multiple-organ failure.

Conclusion
VVA ECMO can provide combined respiratory and circulatory support for post-lung transplant patients with severe respiratory failure and cardiovascular compromise. It is an effective method for promoting the recovery of patients with multiple-organ failure, respiratory failure following lung transplantation, and severe acute rejection. Therefore, it can serve as a bridge to recovery or re-transplantation for post-lung transplant patients. However, it is a complicated procedure with serious risks and adverse outcomes, including bleeding, multiple-organ failure, and infection.