Extracorporeal Membrane Oxygenation, often called ECMO, is a specialized form of life support. It functions like an external heart and lung system, taking over the work of these organs when they are too damaged or weak to function independently. This temporary support allows the patient’s own heart and lungs to rest and potentially heal, serving as a bridge to recovery or further medical interventions.
Understanding the Heart-Lung Machine
A heart-lung machine, or ECMO, is employed when a patient’s heart or lungs are failing severely, making it impossible for them to oxygenate blood or pump it effectively. Conditions necessitating its use include severe heart failure, acute respiratory distress syndrome (ARDS), severe lung infections like influenza or COVID-19, and complications after heart surgery or cardiac arrest. It also serves as a bridge for patients awaiting heart or lung transplants.
There are two primary types of ECMO: Venoarterial (VA) ECMO and Venovenous (VV) ECMO. VA ECMO supports both the heart and lungs by drawing deoxygenated blood from a vein and returning oxygenated blood to an artery, managing both blood oxygenation and circulation. VV ECMO, conversely, supports only the lungs, drawing blood from a vein and returning oxygenated blood to another vein, relying on the patient’s own heart to pump the blood throughout the body. In both types, blood flows through tubing to an artificial lung within the machine, where oxygen is added and carbon dioxide is removed, before being warmed and returned to the patient.
How Long Can Support Last?
The duration a person remains on a heart-lung machine varies considerably, influenced by several factors. The underlying medical condition is a primary determinant; for instance, patients with acute respiratory failure might require support for a different period than those with severe heart failure. The severity of the illness and the patient’s individual response to treatment, including whether their organs show signs of recovery, also play a substantial role in determining the length of ECMO therapy.
The type of ECMO used also impacts duration. VV ECMO, which supports only lung function, allows for longer periods of support, sometimes weeks or even months. VA ECMO, which supports both heart and lung function, typically has a shorter duration, often ranging from a few days to a couple of weeks, with a median duration of about 4 to 8 days. The decision to continue or discontinue ECMO support is made by a multidisciplinary medical team based on continuous evaluation of the patient’s potential for recovery and associated risks.
Risks of Extended Support
Being on a heart-lung machine carries several potential risks, which tend to increase with the duration of support. Bleeding is a common concern because blood thinners, such as heparin, are administered to prevent clots from forming within the ECMO circuit. This necessary anticoagulation can lead to bleeding at cannula insertion sites, surgical sites, or internally, including intracranial hemorrhage.
Infections are a significant risk, as invasive lines and a weakened immune system increase susceptibility to hospital-acquired infections, including bloodstream infections and ventilator-associated pneumonia. Blood clots can also form in the ECMO circuit or within the patient, potentially leading to complications like stroke.
Other potential complications include acute kidney injury requiring dialysis, liver dysfunction, or limb ischemia (reduced blood flow to the limbs where cannulas are inserted). Prolonged immobility while on ECMO can also result in muscle weakness and wasting.
The Path to Recovery
Once a patient’s heart and/or lungs show signs of improvement, the medical team begins the process of gradually reducing ECMO support, known as weaning. This involves carefully decreasing the machine’s assistance while closely monitoring the patient’s physiological response, including their heart function, oxygen levels, and carbon dioxide clearance. If the patient can maintain stable organ function with minimal machine support, the ECMO cannulas are then removed, either at the bedside or in an operating room.
The period following ECMO decannulation often involves extensive rehabilitation to address the effects of prolonged critical illness and immobility. Patients commonly experience muscle weakness, fatigue, and sometimes cognitive impairment, requiring physical, occupational, and potentially speech therapy. Recovery can be a long and challenging journey, with some lingering symptoms persisting for months, but many patients do achieve a good recovery with ongoing support from medical teams and family.