Veno-Venous Extracorporeal Membrane Oxygenation (VV ECMO): Therapeutic Option for Patients with COVID-19 Essay

Venous-venous extracorporeal membrane oxygenation (VV ECMO) is one of the therapeutic options for patients with respiratory insufficiency secondary to coronavirus disease 2019 (COVID-19). VV ECMO provides extracorporeal respiratory support; thus, the lungs are allowed to rest and heal. VV ECMO was indicated for patients with acute respiratory distress syndrome (ARDS) caused by hypoxemia due to COVID-19.

Why VV ECMO For COVID-19?

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can lead to COVID-19, which can present with severe SARS-CoV-2-associated acute respiratory distress syndrome (ARDS). Older people with comorbidity and severe pneumonia are more vulnerable to the virus, leading to hypoxemia and hypercapnea due to impaired gas exchange in the lungs. There is an indication for VV ECMO for patients with COVID-19 who developed protective mechanical ventilation strategies failure to improve oxygenation. Furthermore, VV ECMO can be indicated for COVID-19 patients presenting with severe hypoxemia that is resistant to positive pressure mechanical ventilation (PPMV) and prone positioning. The use of VV ECMO can be considered for patients with COVID-19 and hypoxemic respiratory failure who do not respond to conventional treatments.

VV ECMO Indications For COVID-19

Refractory Hypoxemia

Hypoxemia with PaO2/FiO2 <100 despite optimized strategies for positive-pressure mechanical ventilation [PPMV] or high-flow nasal cannula [HFNC] or non-invasive positive pressure ventilation [NIPPV] with FiO2>0.9 is also an indication for VV ECMO. This might present when there is an inability to achieve the desired oxygenation level even while using high positive end-expiratory pressure (PEEP) in prone positioning.

Inability to Tolerate High Ventilator Settings

PPMV with high pressure settings can cause ventilator-induced lung injury [VILI]. Inability to tolerate high ventilator settings is an indication for VV ECMO.

Hypercapnic Respiratory Failure

Hypercapnia and respiratory acidosis despite optimized ventilatory support can also indicate the need for VV ECMO.

Failure of Non-Invasive Ventilation

Failure of non-invasive positive pressure ventilation [NIPPV] or intubation with mechanical ventilation can also be an indication for VV ECMO.

Severe ARDS with Reversible Etiology

Severe acute respiratory distress syndrome with reversible etiology such as COVID-19 can also be an indication for VV ECMO.

Absence of Contraindications for ECMO

Contraindications for extracorporeal membrane oxygenation (ECMO) include severe multi-system organ failure, irreversible central nervous system damage, and other factors preventing survival; patients who are unlikely to benefit from ECMO should also be excluded. For similar reasons, patients with COVID-19 should also be excluded from VV ECMO if there are other preexisting conditions that are unlikely to improve.

How VV ECMO Works For COVID-19

VV ECMO can provide extracorporeal respiratory support for patients with COVID-19 by draining the venous blood via cannula, oxygenating and removing CO2 in the machine, and returning the blood to the circulation. VV ECMO involves cannulating a large vein, usually the cannula, where blood is diverted to the circuit for oxygenation. Although VV ECMO provides extracorporeal oxygenation and CO2 removal, patients can be placed on a ventilator with protective lung settings. Thus, VV ECMO allows the lungs to heal.

Benefits of VV ECMO in Patients with COVID-19

Improved Oxygenation and CO2 Removal

VV ECMO can help improve oxygenation and CO2 removal, which can help maintain the normal functioning of the body.

Lung Rest and Protection

VV ECMO can help the lungs to rest and recover as it provides extracorporeal oxygenation and CO2 removal. This can help reduce ventilator-induced lung injury (VILI) that can occur with positive-pressure mechanical ventilation.

Reduced Risk of VILI

By reducing the need for PPMV and allowing the lungs to rest and recover, VV ECMO can help reduce the risk of ventilator-induced lung injury (VILI).

Bridge to Recovery

VV ECMO can serve as a bridge to recovery for patients with COVID-19 who developed ARDS. This is because the lungs are allowed to heal while the extracorporeal membrane oxygenation (ECMO) provides oxygenation and CO2 removal. Consequently, VV ECMO can be beneficial in bridging such patients to recovery as the infection clears and the inflammation subsides.

Avoidance of Intubation-Associated Damage

In some situations, VV ECMO can be considered as an alternative to intubation or invasive positive-pressure mechanical ventilation. This can help avoid intubation-associated damage to the airways or lung injury due to VILI.

Risks and Challenges of VV ECMO in Patients with COVID-19

Bleeding

VV ECMO requires the use of anti-coagulants to prevent clotting of the circuit; thus, bleeding can occur at the cannulation site or central nervous system. Patients with COVID-19 also have an increased risk of bleeding due to the coagulopathy.

Infection

The use of VV ECMO can increase the risk of infection due to the multiple catheters placed in the patients and the long duration of use. The infection can lead to hospital-acquired infections, infections at the cannulation site, or infection of the circuit.

Vascular Injury

Vascular injury can occur due to cannulation of subclavian, femoral, or internal jugular vein. Thrombosis can also occur, thereby affecting the flow of blood in the vein.

Multi-Organ Failure

In patients with COVID-19, VV ECMO use can contribute to multi-organ failure, especially in those at higher risk.

Technical Difficulties

Technical difficulties can occur with VV ECMO, such as clotting of the circuit or malfunctioning of the oxygenator that requires intervention to manage the problem.

Lengthy Weaning Process

The process of weaning patients from VV ECMO can be prolonged; therefore, careful management is required. Furthermore, patients who are placed on VV ECMO for a long time can experience various complications associated with its use. Thus, early weaning from the VV ECMO is essential to improve patient outcome.

Considerations for ECMO in Patients with COVID-19

Timely Initiation of ECMO

Timely initiation of VV ECMO is critical for patients with COVID-19. Early initiation of VV ECMO prior to the development of multi-system organ failure is essential to improve the patient’s outcome. However, VV ECMO should only be initiated when conventional treatment modalities have failed.

Patient Eligibility

VV ECMO should only be initiated for patients with hypoxemia or hypercapnia that cannot be managed by conventional positive-pressure mechanical ventilation (PPMV). Patients with irreversible damage or those that would not benefit from VV ECMO should be excluded.

Multidisciplinary Approach

The management of patients with COVID-19 who require VV ECMO requires a multidisciplinary approach. This includes intensivists, ECMO specialists, respiratory therapists, and cardiologists, among others.

Outcomes and Prognosis

The outcome and prognosis of VV ECMO use in patients with COVID-19 largely depend on the severity of the disease, the patient’s general health status, and timely initiation. It has been reported that survival following VV ECMO for patients with COVID-19 ranges between 50-70%. Patients that survive are usually able to make a complete recovery; however, some may require lung transplant due to the inability of the lungs to recover.