|Extracorporeal membrane oxygenation|
|Other names||Extracorporeal life support (ECLS)|
Extracorporeal membrane oxygenation (ECMO), also known as extracorporeal life support (ECLS), is an extracorporeal technique of providing prolonged cardiac and respiratory support to persons whose heart and lungs are unable to provide an adequate amount of gas exchange or perfusion to sustain life. The technology for ECMO is largely derived from cardiopulmonary bypass, which provides shorter-term support with arrested native circulation. The device used is a membrane oxygenator, also known as an artificial lung.
ECMO works by temporarily drawing blood from the body to allow artificial oxygenation of the red blood cells and removal of carbon dioxide. Generally, it is used either post-cardiopulmonary bypass or in late-stage treatment of a person with profound heart and/or lung failure, although it is now seeing use as a treatment for cardiac arrest in certain centers, allowing treatment of the underlying cause of arrest while circulation and oxygenation are supported. ECMO is also used to support patients with the acute viral pneumonia associated with COVID-19 in cases where artificial ventilation alone is not sufficient to sustain blood oxygenation levels.
Guidelines that describe the indications and practice of ECMO are published by the Extracorporeal Life Support Organization (ELSO). Criteria for the initiation of ECMO vary by institution, but generally include acute severe cardiac or pulmonary failure that is potentially reversible and unresponsive to conventional management. Examples of clinical situations that may prompt the initiation of ECMO include the following:
In those with cardiac arrest or cardiogenic shock, it appears to improve survival and good outcomes.
Beginning in early February 2020, doctors in China have increasingly been using ECMO as an adjunct support for patients presenting with acute viral pneumonia associated with SARS-CoV-2 infection (COVID-19) when, with ventilation alone, the blood oxygenation levels still remain too low to sustain the patient.The initial reports indicate that it is assisting in restoring patients' blood oxygen saturation and reducing fatalities among the approximately 3% of severe cases where it has been utilized. For critically ill patients, the mortality rate reduces from around 59–71% with conventional therapy to approximately 46% with extracorporeal membrane oxygenation. A March 2021 Los Angeles Times cover story illustrated the efficacy of ECMO in an extremely challenging COVID patient. In February 2021, three pregnant Israeli women who had "very serious" cases of COVID-19 were given ECMO treatment and it seemed this treatment option would continue.
Early studies had shown survival benefit with use of ECMO for people in acute respiratory failure especially in the setting of acute respiratory distress syndrome.A registry maintained by ELSO of nearly 51,000 people that have received ECMO has reported outcomes with 75% survival for neonatal respiratory failure, 56% survival for pediatric respiratory failure, and 55% survival for adult respiratory failure. Other observational and uncontrolled clinical trials have reported survival rates from 50 to 70%. These reported survival rates are better than historical survival rates. Even though ECMO is used for a range of conditions with varying mortality rates, early detection is key to prevent the progression of deterioration and increase survival outcomes.
In the United Kingdom, veno-venous ECMO deployment is concentrated in designated ECMO centers to potentially improve care and promote better outcomes.
Most contraindications are relative, balancing the risks of the procedure versus the potential benefits. The relative contraindications are:
A common consequence in ECMO-treated adults is neurological injury, which may include intracerebral hemorrhage, subarachnoid hemorrhage, ischemic infarctions in susceptible areas of the brain, hypoxic-ischemic encephalopathy, unexplained coma, and brain death. [ citation needed ]Bleeding occurs in 30 to 40% of those receiving ECMO and can be life-threatening. It is due to both the necessary continuous heparin infusion and platelet dysfunction. Meticulous surgical technique, maintaining platelet counts greater than 100,000/mm3, and maintaining the target activated clotting time reduce the likelihood of bleeding.
Heparin-induced thrombocytopenia (HIT) is increasingly common among people receiving ECMO. When HIT is suspected, the heparin infusion is usually replaced by a non-heparin anticoagulant.
There is retrograde blood flow in the descending aorta whenever the femoral artery and vein are used for VA (Veno-Arterial) ECMO. Stasis of the blood can occur if left ventricular output is not maintained, which may result in thrombosis.[ citation needed ]
In VA ECMO, those whose cardiac function does not recover sufficiently to be weaned from ECMO may be bridged to a ventricular assist device (VAD) or transplant. A variety of complications can occur during cannulation, including vessel perforation with bleeding, arterial dissection, distal ischemia, and incorrect location (e.g., venous cannula placed within the artery), but these events occur highly infrequently.[ citation needed ]
Preterm infants are at unacceptably high risk for intraventricular hemorrhage (IVH) if administered ECMO at a gestational age less than 32 weeks.
The prevalence of hospital-acquired infections during ECMO is 10-12% (higher compared to other critically ill patients). Coagulase-negative staphylococci, Candida spp., Enterobacteriaceae and Pseudomonas aeruginosa are the most frequently involved pathogens. ECMO patients display a high incidence of ventilator-associated pneumonia (24.4 cases/1000 ECMO days), with a major role played by Enterobacteriaceae. The infectious risk was shown to increase along the duration of the ECMO run, which is the most important risk factor for the development of infections. Other ECMO-specific factors predisposing to infections include the severity of illness in ECMO patients, the high risk of bacterial translocation from the gut and ECMO-related impairment of the immune system. Another important issue is the microbial colonisation of catheters, ECMO cannulae and the oxygenator.
There are several forms of ECMO; the two most common are veno-arterial (VA) ECMO and veno-venous (VV) ECMO. In both modalities, blood drained from the venous system is oxygenated outside of the body. In VA ECMO, this blood is returned to the arterial system and in VV ECMO the blood is returned to the venous system. In VV ECMO, no cardiac support is provided.
In veno-arterial (VA) ECMO, a venous cannula is usually placed in the right or left common femoral vein for extraction, and an arterial cannula is usually placed into the right or left femoral artery for infusion.The tip of the femoral venous cannula should be maintained near the junction of the inferior vena cava and right atrium, while the tip of the femoral arterial cannula is maintained in the iliac artery. In adults, accessing the femoral artery is preferred because the insertion is simpler. Central VA ECMO may be used if cardiopulmonary bypass has already been established or emergency re-sternotomy has been performed (with cannulae in the right atrium (or SVC/IVC for tricuspid repair) and ascending aorta).
VA ECMO is typically reserved when native cardiac function is minimal to mitigate increased cardiac stroke work associated with pumping against retrograde flow delivered by the aortic cannula.
In veno-venous (VV) ECMO, cannulae are usually placed in the right common femoral vein for drainage and right internal jugular vein for infusion.Alternatively, a dual-lumen catheter is inserted into the right internal jugular vein, draining blood from the superior and inferior vena cavae and returning it to the right atrium.
ECMO should be performed only by clinicians with training and experience in its initiation, maintenance, and discontinuation. ECMO insertion is typically performed in the operating room setting by a cardiothoracic surgeon. ECMO management is commonly performed by a registered nurse, respiratory therapist, or a perfusionist. Once it has been decided to inititiate ECMO, the patient is anticoagulated with intravenous heparin to prevent thrombus formation from clotting off the oxygenator. Prior to initiation, an IV bolus of heparin is given and measured to ensure that the activated clotting time (ACT) is between 300 and 350 seconds. Once the ACT is between this range, ECMO can be initiated and a heparin drip will be started after as a maintenance dose.
Cannulae can be placed percutaneously by the Seldinger technique, a relatively straightforward and common method for obtaining access to blood vessels, or via surgical cutdown. The largest cannulae that can be placed in the vessels are used in order to maximize flow and minimize shear stress.
ECMO required for complications post-cardiac surgery can be placed directly into the appropriate chambers of the heart or great vessels. Central cannulation via lateral thoracotomy allows patients awaiting lung transplantation to remain unsedated and ambulatory.
Following cannulation and connection to the ECMO circuit, the appropriate amount of blood flow through the ECMO circuit is determined using hemodynamic parameters and physical exam. Goals of maintaining end-organ perfusion via ECMO circuit are balanced with sufficient physiologic blood flow through the heart to prevent stasis and subsequent formation of blood clot.
Once the initial respiratory and hemodynamic goals have been achieved, the blood flow is maintained at that rate. Frequent assessment and adjustments are facilitated by continuous venous oximetry, which directly measures the oxyhemoglobin saturation of the blood in the venous limb of the ECMO circuit.
VV ECMO is typically used for respiratory failure, while VA ECMO is used for cardiac failure. There are unique considerations for each type of ECMO, which influence management.
Near-maximum flow rates are usually desired during VV ECMO to optimize oxygen delivery. In contrast, the flow rate used during VA ECMO must be high enough to provide adequate perfusion pressure and venous oxyhemoglobin saturation (measured on drainage blood) but low enough to provide sufficient preload to maintain left ventricular output.
Since most people are fluid-overloaded when ECMO is initiated, aggressive diuresis is warranted once the patient is stable on ECMO. Ultrafiltration can be easily added to the ECMO circuit if the patient has inadequate urine output. ECMO "chatter", or instability of ECMO waveforms, represents under-resuscitation and would support cessation of aggressive diuresis or ultrafiltration.
Left ventricular output is rigorously monitored during VA ECMO because left ventricular function can be impaired from increased afterload, which can in turn lead to formation of thrombus within the heart.
For those with respiratory failure, improvements in radiographic appearance, pulmonary compliance, and arterial oxyhemoglobin saturation indicate that the person may be ready to be taken off ECMO support. For those with cardiac failure, enhanced aortic pulsatility correlates with improved left ventricular output and indicates that they may be ready to be taken off ECMO support. If all markers are in good status, the blood flows on the ECMO will be slowly decreased and the patients parameters will be observed during this time to ensure that the patient can tolerate the changes. When the flows are below 2 liters per minute, permanent removal is attempted and the patient is continued to be monitored during this time until the cannulae can be removed.
VV ECMO trials are performed by eliminating all countercurrent sweep gas through the oxygenator. Extracorporeal blood flow remains constant, but gas transfer does not occur. They are then observed for several hours, during which the ventilator settings that are necessary to maintain adequate oxygenation and ventilation off ECMO are determined as indicated by arterial and venous blood gas results.
VA ECMO trials require temporary clamping of both the drainage and infusion lines, while allowing the ECMO circuit to circulate through a bridge between the arterial and venous limbs. This prevents thrombosis of stagnant blood within the ECMO circuit. In addition, the arterial and venous lines should be flushed continuously with heparinized saline or intermittently with heparinized blood from the circuit. In general, VA ECMO trials are shorter in duration than VV ECMO trials because of the higher risk of thrombus formation.
ECMO was developed in the 1950s by John Gibbon, and then by C. Walton Lillehei. The first use for neonates was in 1965.
Banning Gray Laryfirst demonstrated that intravenous oxygen could maintain life. His results were published in Surgical Forum in November 1951. Lary commented on his initial work in a 2007 presentation wherein he writes, "Our research began by assembling an apparatus that, for the first time, kept animals alive while breathing pure nitrogen. This was accomplished with very small bubbles of oxygen injected into the blood stream. These bubbles were made by adding a 'wetting agent' to oxygen being forced through a porcelain filter into the venous blood stream. Shortly after its initial presentation to the American College of Surgeons, this apparatus was reviewed by Walton Lillehei who with DeWall made the first practical heart lung machine that employed a bubble oxygenator. With variations such machines were used for the next twenty years."
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|United States||North America||264 (in 2019)|
|Canada||North America||19 (in 2020)|
|Australia||Oceania||146 (in 2020)|
|Brazil||South America||21 (in 2021)|
|England and Wales||Europe||5 (in 2020)||15 (in 2020)|
|Northern Ireland||Europe||0 (in 2020)||0 (in 2020)|
|Scotland||Europe||1 (in 2020)||6 (in 2020)|
|Germany||Europe||214 (in 2020)||755 (in 2020)|
|Poland||Europe||47 (in 2020)|
|Sweden||Europe||7 or more (in 2020)|
|Albania||Europe||0 (in 2020)||0 (in 2020)|
|Russia||Europe||124 + 17 (in 2020)|
|Moscow||Europe||16 (in 2020)|
|Saint Petersburg||Europe||7||19 (in 2020)|
|Japan||Asia||2208 (in 2020)|
|Mainland China||Asia||400 (approx. in 2020)|
|Taiwan||Asia||51 (in 2016)||105 (in 2016)|
A 2014 study showed that a factor XIIa inhibitory antibody provides thromboprotection in extracorporeal circulation without increasing bleeding risk.Experiments on neonatal animals showed that ECMO treatment can lead to apoptosis of enterocytes, damage of the intestinal mucosal barrier and bacterial translocation. This might explain greater severity of systemic inflammatory response syndrome in neonates. ECMO has also seen its use on cadavers as being able to increase the viability rate of transplanted organs.
A respiratory therapist is a specialized healthcare practitioner trained in critical care and cardio-pulmonary medicine in order to work therapeutically with people suffering from acute critical conditions, cardiac and pulmonary disease. Respiratory therapists graduate from a college or university with a degree in respiratory therapy and have passed a national board certifying examination. The NBRC is the not-for-profit organization responsible for credentialing the seven areas of Respiratory Therapy in the United States.
Cardiac output (CO), also known as heart output denoted by the symbols , or , is a term used in cardiac physiology that describes the volume of blood being pumped by the heart, by the left and right ventricle, per unit time. Cardiac output (CO) is the product of the heart rate (HR), i.e. the number of heartbeats per minute (bpm), and the stroke volume (SV), which is the volume of blood pumped from the ventricle per beat; thus, CO = HR × SV. Values for cardiac output are usually denoted as L/min. For a healthy person weighing 70 kg, the cardiac output at rest averages about 5 L/min; assuming a heart rate of 70 beats/min, the stroke volume would be approximately 70 ml.
Cardiopulmonary bypass (CPB) is a technique in which a machine temporarily takes over the function of the heart and lungs during surgery, maintaining the circulation of blood and the oxygen content of the patient's body. The CPB pump itself is often referred to as a heart–lung machine or "the pump". Cardiopulmonary bypass pumps are operated by perfusionists. CPB is a form of extracorporeal circulation. Extracorporeal membrane oxygenation is generally used for longer-term treatment.
Acute respiratory distress syndrome (ARDS) is a type of respiratory failure characterized by rapid onset of widespread inflammation in the lungs. Symptoms include shortness of breath (dyspnea), rapid breathing (tachypnea), and bluish skin coloration (cyanosis). For those who survive, a decreased quality of life is common.
A cardiovascular perfusionist, clinical perfusionist or perfusiologist, and occasionally a cardiopulmonary bypass doctor or clinical perfusion scientist, is a healthcare professional who operates the cardiopulmonary bypass machine during cardiac surgery and other surgeries that require cardiopulmonary bypass to manage the patient's physiological status. As a member of the cardiovascular surgical team, the perfusionist also known as the clinical perfusionist helps maintain blood flow to the body's tissues as well as regulate levels of oxygen and carbon dioxide in the blood, using a heart–lung machine.
Hypoxemia is an abnormally low level of oxygen in the blood. More specifically, it is oxygen deficiency in arterial blood. Hypoxemia has many causes, and often causes hypoxia as the blood is not supplying enough oxygen to the tissues of the body.
Alveolar lung diseases, are a group of diseases that mainly affect the alveoli of the lungs.
The Alveolar–arterial gradient, is a measure of the difference between the alveolar concentration (A) of oxygen and the arterial (a) concentration of oxygen. It is an useful parameter for narrowing the differential diagnosis of hypoxemia.
An oxygenator is a medical device that is capable of exchanging oxygen and carbon dioxide in the blood of human patient during surgical procedures that may necessitate the interruption or cessation of blood flow in the body, a critical organ or great blood vessel. These organs can be the heart, lungs or liver, while the great vessels can be the aorta, pulmonary artery, pulmonary veins or vena cava.
Cardiothoracic anesthesiology is a subspeciality of the medical practice of anesthesiology, devoted to the preoperative, intraoperative, and postoperative care of adult and pediatric patients undergoing cardiothoracic surgery and related invasive procedures.
Persistent fetal circulation is a condition caused by a failure in the systemic circulation and pulmonary circulation to convert from the antenatal circulation pattern to the "normal" pattern. Infants experience a high mean arterial pulmonary artery pressure and a high afterload at the right ventricle. This means that the heart is working against higher pressures, which makes it more difficult for the heart to pump blood.
Impella is a family of medical devices used for temporary ventricular support in patients with depressed heart function. Some versions of the device can provide left heart support during other forms of mechanical circulatory support including ECMO and Centrimag.
Heated humidified high-flow (HHHF) therapy, often also high flow nasal cannula(e) (HFNC) or high flow nasal oxygen (HFNO), is a type of respiratory support method that delivers a high flow of medical gas to a patient through an interface intended to create a wash-out of the upper airway. The applied gas is heated to best match human body temperature (37 °C) and humidified targeting ideal body saturation vapor pressure. It is used in acute and chronic breathing problems, and is a suitable choice for treatment of patients with severe or critical COVID-19.
The Senning procedure is an atrial switch heart operation performed to treat transposition of the great arteries. It is named after its inventor, the Swedish cardiac surgeon Åke Senning (1915–2000), also known for implanting the first permanent cardiac pacemaker in 1958.
The Extracorporeal Life Support Organization (ELSO) is a non profit organization established in 1989 supporting health care professionals and scientists who are involved in extracorporeal membrane oxygenation (ECMO). ELSO maintains a registry of both facilities and specialists trained to provide ECMO services. ELSO also maintains registry information that is used to support clinical research, support regulatory agencies, and support individual ELSO centers. ELSO provides educational programs for active centers as well as for facilities who may be involved in the transfer of patients to higher levels of care.
Extracorporeal cardiopulmonary resuscitation is a method of cardiopulmonary resuscitation (CPR) that passes the patient's blood through a machine in a process to oxygenate the blood supply. A portable extracorporeal membrane oxygenation (ECMO) device is used as an adjunct to standard CPR. A patient who is deemed to be in cardiac arrest refractory to CPR has percutaneous catheters inserted into the femoral vein and artery. Theoretically, the application of ECPR allows for the return of cerebral perfusion in a more sustainable manner than with external compressions alone. By attaching an ECMO device to a person who has acutely undergone cardiovascular collapse, practitioners can maintain end-organ perfusion whilst assessing the potential reversal of causal pathology, with the goal of improving long-term survival and neurological outcomes.
Bridge therapy is therapy intended, in transportation metaphor, to serve as a figurative bridge to another stage of therapy or health, carrying a patient past a challenging period of some kind. There are various types of bridge therapy, such as bridge to transplant, bridge to candidacy, bridge to decision, bridge to recovery, and anticoagulation bridge. Bridge therapy exists in contrast to destination therapy, which is the figurative destination rather than a bridge to something else.
Retrograde autologous priming (RAP) is a means to effectively and safely restrict the hemodilution caused by the direct homologous blood transfusion and reduce the blood transfusion requirements during cardiac surgery. It is also generally considered a blood conservation method used in most patients during the cardiopulmonary bypass (CPB). The processing of RAP includes three main steps, and the entire procedure of RAP could be completed within 5 to 8 minutes. This technique is proposed by Panico in 1960 for the first time and restated by Rosengart in 1998 to eliminate or reduce the risk of hemodilution during CPB. Moreover, to precisely determine the clinical efficacy of RAP, many related studies were conducted. Most results of researches indicate that RAP is available to provide some benefits to reducing the requirements for red blood cell transfusion. However, there are still some studies showing a failure of RAP to limit the hemodilution after the open heart operation.
There is no specific, effective treatment or cure for coronavirus disease 2019 (COVID-19), the disease caused by the SARS-CoV-2 virus. One year into the pandemic, highly effective vaccines have now been introduced and are beginning to slow the spread of SARS-CoV-2; however, for those awaiting vaccination, as well as for the estimated millions of immunocompromised persons who are unlikely to respond robustly to vaccination, treatment remains important. Thus, the lack of progress developing effective treatments means that the cornerstone of management of COVID-19 has been supportive care, which includes treatment to relieve symptoms, fluid therapy, oxygen support and prone positioning as needed, and medications or devices to support other affected vital organs.
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