Veno-Venous Extracorporeal Membrane Oxygenation Essay

Veno-Venous Extracorporeal Membrane Oxygenation (VV ECMO), or Extracorporeal Membrane Oxygenation (ECMO), is a method that was established for the treatment of severe cases of acute respiratory distress syndrome. In general, Acute respiratory distress syndrome (ARDS) is “a severe clinical syndrome of hypoxemia, respiratory failure, and pulmonary edema that develops after pneumonia, sepsis, trauma, or aspiration.” Thus, VV ECMO is indicated as a supportive therapy in patients with acute respiratory distress syndrome whose treatment did not lead to an improvement in the level of oxygenation and ventilation. Veno-venous extracorporeal membrane oxygenation helps offload the circulation through the lungs, so the lungs can rest. VV ECMO is indicated for patients with acute respiratory distress syndrome. The purpose of this paper is to discuss the use of Veno-Venous Extracorporeal Membrane Oxygenation for the treatment of patients with ARDS.

VV ECMO for ARDS: Why and when is it used?

VV ECMO for ARDS is indicated for patients whose treatment “failed to provide the required level of oxygenation and ventilation,” which determines the indications for VV ECMO. Therefore, the indications for patients with ARDS include refractory hypoxemia, hypercapnic respiratory failure, lung protective ventilation strategies, persistent respiratory acidosis, and failure of conventional treatment. Refractory hypoxemia is hypoxemia that is resistant to treatment; hypoxemia is a condition characterized by oxygen deficiency in tissues. Refractory hypoxemia may be presented by PaO2/FiO2 <100 despite optimal mechanical ventilation, for example, higher than the positive end-expiratory pressure (PEEP) or an inability to achieve oxygenation with FiO2 >0,9 and PaO2 <60 mmHg. Hypercapnic respiratory failure presentation includes failure of mechanical ventilation to offload the lungs resulting in CO2 retention and respiratory acidosis. Lung protective ventilation strategies are indicated for patients with ARDS when conventional methods of high PEEP and low tidal volume mechanical ventilation strategies fail; high PEEP and low tidal volume mechanical ventilation strategies are indicated for patients with ARDS to reduce the risk of ventilator-induced lung injury (VILI). Another indication for using VV ECMO includes persistent respiratory acidosis that is resistant to a standard treatment; respiratory acidosis is a condition characterized by decreased pH due to increased CO2 levels; persistent respiratory acidosis refers to respiratory acidosis that is resistant to treatment. Finally, the indication for VV ECMO for ARDS includes the failure of conventional treatment such as high-flow nasal cannula oxygen therapy, non-invasive positive pressure ventilation, intubation, and mechanical ventilation. Thus, VV ECMO is indicated for ARDS patients when the etiology of the condition can be regarded as reversible. Consequently, VV ECMO should be considered in the case of ARDS caused by pneumonia, sepsis, and aspiration pneumonitis as these etiologies can be effectively treated.

How does VV ECMO work?

VV ECMO differs from Veno-Arterial ECMO (VA) because it provides respiratory support rather than circulatory support; It is used to offload the patient’s lungs thereby allowing the lungs to rest by oxygenating the patient’s blood and removing the carbon dioxide from the patient’s blood. A VV ECMO circuit includes a venous cannula, an oxygenator, and a venous return cannula. The venous cannula is placed in the venous system to withdraw blood and divert it to the oxygenator, which oxygenates the blood and removes the carbon dioxide from the blood. Then, the venous return cannula returns the oxygenated blood into the venous circulation from which the oxygenated blood is distributed to the rest of the patient’s body.

VV ECMO Benefits for ARDS

Lung rest and healing

VV ECMO benefits patients with ARDS by allowing the lungs to rest and heal because the machine oxygenates the blood and removes the carbon dioxide from the blood; this is critical for the patients with ARDS because the alveoli in their lungs are inflamed and, therefore, unable to perform their function.

Prevention of ventilator-associated pneumonia and ventilator-induced lung injury

Another benefit of VV ECMO is the prevention of ventilator-associated pneumonia (VAP) and ventilator-induced lung injury (VILI). VAP and VILI are preventable causes of morbidity and mortality that can develop as a result of mechanical ventilation.

Improved oxygenation

VV ECMO can benefit patients with ARDS by improving oxygenation, for instance, by providing patients with severe hypoxemia that is resistant to conventional treatment with an opportunity to receive adequate oxygenation.

Bridge to recovery for patients with reversible ARDS

VV ECMO can serve as a bridge to recovery for patients with reversible ARDS; in other words, the VV ECMO machine can give time for the lungs of the patients with reversible ARDS to heal.

Allows for protective mechanical ventilation

Finally, a major benefit of VV ECMO is allowing for protective mechanical ventilation that minimizes the risk of ventilator-induced lung injury (VILI) by using low tidal volumes and low PEEP. Protective mechanical ventilation is essential for patients with ARDS because it minimizes the risk of VILI.

VV ECMO Challenges and risks for ARDS patients

Bleeding

One of the major risks and challenges associated with VV ECMO is the possibility of bleeding due to anticoagulation required to prevent the clotting of the machine; the risk of bleeding can lead to various adverse outcomes such as stroke and gastrointestinal hemorrhage with negative prognosis.

Infection

Another risk associated with the use of VV ECMO is the possibility of infection that can lead to multiple-organ dysfunction syndromes; the risk of infection is especially high among the patients who are placed on ECMO for an extended period of time.

Vascular complications

Vascular complications such as bleeding, thrombosis, and ischemia can also occur as a result of VV ECMO due to the need for large-caliber vessel cannulation.

Organ dysfunction

Organ dysfunction such as kidney and liver dysfunction is another risk and challenge associated with the use of VV ECMO. The patients who undergo VV ECMO are also at particularly high risk of developing ARDS and respiratory failure.

Technical challenges

A technical challenge associated with Veno-venous ECMO is the possibility of pump malfunction and circuit clotting that can lead to various adverse events such as hypoxia and circulatory collapse.

The duration of VV ECMO use is limited

The duration of the use of VV ECMO is limited due to the associated vascular and renal complications that can develop in the patients who undergo it for an extended period of time.

Outcomes and prognosis

The outcome of VV ECMO for the treatment of ARDS depends on various factors such as the severity of the condition, the etiology of ARDS, and the timing of the intervention. Patients with severe ARDS who underwent VV ECMO have a better prognosis than the patients who received conventional treatment. Prognosis is also better for the patients who received VV ECMO earlier in the course of the disease than for those who received it later. Overall, the prognosis of VV ECMO for the treatment of ARDS is good, especially in the cases of ARDS with reversible etiology.

Conclusion

VV ECMO is an effective treatment option for the patients with severe acute respiratory distress syndrome (ARDS) who failed to respond to conventional respiratory support measures. VV ECMO for ARDS can benefit such patients by giving them an opportunity to receive respiratory support while their lungs rest and heal. VV ECMO can be an essential part of treatment for patients with ARDS, including those with reversible ARDS, because it allows such patients to receive adequate oxygenation. However, this life-saving procedure is associated with various risks and, therefore, should be used with caution.