3 of 37

ECMO stands for ExtraCorpeal Membrane Oxygenation. Another name for ECMO is ExtraCorpeal Life Support (ECLS). ECMO is used for respiratory and/ or cardiac failure when conventional management is unsuccessful. Not only is ECMO used for hemodynamic support, but it keeps blood moving through the body as a mechanism for blood gas exchange.

ECMO is an advanced form of temporary life support that decreases the workload of the lungs and heart when they are unable to adequately support the body with oxygenation and perfusion. Think of ECMO as an external lung, heart, or both.

ECMO not only is used as medical therapy for cardiac and respiratory recovery, but as a bridge to further treatment (i.e., LVAD and heart/ lung transplant).

Since ECMO is a closed system, air, clots, and disconnections are emergencies.

4 of 37

Types of ECMO

5 of 37

TRADITIONAL CONFIGURATIONS:

Veno-arterial (VA) ECMO

Blood is drained from a large vein and returns to an artery
Provides cardio-respiratory support
VA-ECMO requires two cannulas to be placed in either the neck or groin(s)
Indicated in cardiogenic shock, obstructive shock, severe cardiac failure, post-cardiotomy failure, graft failure, severe drug or cardiotoxic medication intoxication, refractory arrhythmias, right ventricular heart failure, and cardiac arrest
If patient codes, there is no need to perform CPR if perfusion is adequate. It is okay to perform defibrillation.

Veno-venous (VV) ECMO

Blood is drained from a large vein and returned to the venous system
Provides respiratory support by providing O2 and removing CO2
Must have enough cardiac function to meet physiologic needs because the patient’s own heart will pump blood throughout the body
With VV-ECMO, the operator has the option to use a special dual-lumen cannula allowing blood to leave and return to the body in one place, or it may use two regular cannulas
Indicated in patients with severe respiratory failure, ARDS, severe hypoxia, severe hypercapnia/ acidosis, respiratory refractory status, and severe airway or pulmonary crisis
If patient codes, CPR and defibrillation are okay to perform

6 of 37

(Image from Springer Nature)

7 of 37

Hybrid ECMO refers to combining or modifying traditional VV and VA ECMO modes by connected multiple cannulas to one pump and oxygenator. Hybrid ECMO is used to manage complex cardiac and respiratory failure.

Parallel ECMO refers to when there are two separate ECMO circuits running at the same time to provide extra support. Sometimes this is necessary in patients with refractory hypoxemia, high cardiac output, and severe habitus or metabolic stress.

Parallel VV + VV ECMO = two respiratory support circuits
Parallel VV + VA ECMO = one respiratory circuit plus and additional circuit for cardiopulmonary support
Two oxygenators in parallel within one circuit = greater membrane surface area and reduced resistance through each oxygenator

ECPELLA is when VA-ECMO is combined with an Impella for left-ventricular unloading.

ADDITIONAL CONFIGURATIONS:

(Image from JTCVS Techniques)

8 of 37

(Image from Wiley Online Library)

9 of 37

How does ECMO work?

10 of 37

Deoxygenated blood flows from the venous drainage cannula and is drawn into the pump via negative pressure.��The mechanical centrifugal pump rapidly spins using positive pressure to drive blood forward towards the membrane oxygenator (external lung).��A mixture of medical grade air and oxygen is delivered through the porous, hollow-fiber membrane within the oxygenator for gas exchange to occur. Oxygen is moved into the blood while carbon dioxide is swept away and vented out of the machine. ��Attached to the oxygenator is the thermometer and heat exchanger to warm or cool the blood.��Oxygenated blood, warmed to normal body temperature, then exits the membrane oxygenator and is returned to the body via the venous or arterial return cannula.��There are multiple pressure/ flow monitors, access ports, and an ultrasonic bubble detector along the system. ��

(Image from Springer Nature)

11 of 37

ECMO Circuit Components

12 of 37

COMPONENT	DESCRIPTION
CANNULAS	Large-bore tubes placed into vein and/or artery Used for blood drainage and return
CIRCUIT TUBING	Made of a clear, flexible polyvinylchloride (PVC) plastic compound Vary from simple to complex To run properly, there must be no kinking in the tubing Bio-line coated (blend of albumin and heparin) for clot prevention and inflammation reduction Connect wet-to-wet
BLOOD PUMP	Mechanical, external circuit Pulls blood from the body and provides propulsion generating forward flow Regulated by the setting RPM (revolutions per minute)
MEMBRANE OXYGENATOR	Artificial lung Performs gas exchange by adding oxygen and removing carbon dioxide Oxygenation (O2) is controlled primarily by the blood flow rate (adjusted by the pump’s RPM) and the patient’s hemoglobin concentration Ventilation (CO2 removal) is controlled by the sweep gas flow rate Has thousands of tiny, porous, hollow-fiber membranes for diffusion to occur Regulates blood temperature with a heat exchanger
HEAT EXCHANGER	Attached to the oxygenator Warms or cools the blood circulating outside of the body to maintain normal core body temperature
GAS BLENDER	Connects directly to the oxygenator Blend of medical-grade air and oxygen Controls delivered oxygen concentration and the rate of gas flow (sweep gas) to the oxygenator Sweep Gas Flow Moves through the membrane oxygenator to facilitate diffusion Since there is a lower concentration of CO2 in the sweep gas than the drained patient’s blood, CO2 will diffuse across the semipermeable membrane Controls CO2 removal while assisting with oxygenation Controlled by a flow rate (speed)

13 of 37

COMPONENT	DESCRIPTION
PRESSURE SENSORS	Monitors blood resistance and mechanic forces to detect clots and blockages Placed before the pump Named P1, P-venous pressure, and inflow pressure Measures the negative suctioning pressure applied to pull blood via the drainage cannula Normally -15 to -50 mmHg If too negative, it indicates a “chattering” or a “suck-down” event Common causes = patient hypovolemia, patient movement, or catheter malposition against a vessel wall Placed after the pump Named P2, P Pre-membrane, or P-internal pressure Measures the positive pressure propelling blood after the pump and through the oxygenator Normally 100-250 mmHg A sudden spike in this pressure indicates that the pump is pushing against an obstruction Most commonly due to thrombosis within the oxygenator Placed after the oxygenator Named P3, P Post-membrane, P-arterial pressure, and outflow pressure Measures the positive pressure after passing through the oxygenator, prior to returning to the patient Will be lower than P2 pressure because the blood loses pressure as it flows through the resistance of the oxygenator A spike in pressure may be due to an arterial blood clot or kinked return cannula A sudden drop in pressure might be indicative of a line disconnection
FLOW SENSORS/ BUBBLE DETECTORS	Measures blood flow rate Blood flow rate = pump RPM Determines fractional delivered O2 (FdO2) and PaO2 Ultrasonic bubble detector will alarm if bubbles are detected within the tubing
SVO2 MONITORS	Continuously monitors mixed venous oxygen saturation assessing global tissue perfusion and cardiac output Provides information on the balance between systemic oxygen delivery (DO2) and oxygen consumption (VO2) Measures the amount of oxygen leftover after tissue extraction Less reliable during VV-ECMO, but in VA-ECMO it provides information on native cardiac output and overall systemic perfusion
BRIDGE	Short segment of tubing with a clamp Connects the drainage and infusion limbs during specific emergencies or circuit changes

14 of 37

(Image from Anesthesia Key)

(Cabrera, 2017)

15 of 37

ECMO Settings

16 of 37

ECMO Setting		Purpose
Blood flow	L/min	The volume of blood pumped through the circuit per minute Controlled by adjusting the centrifugal pump speed (RPM) Typically, 4.0 – 6.0 L/min or 50 to 70 mL/ kg/ min Low flow may increase thrombosis risk High flow can cause hemolysis, shear-induced platelet surface receptor shedding, and loss of von Willebrand multimers Generally, must stay above 2.0 L/min to prevent stasis or retrograde flow Targets: VV-EMCO 🡪 ECMO flow ≥ 60% of the estimated cardiac output VA-ECMO 🡪 LV or biventricular failure: approximately 80% of cardiac output Isolated RV failure: approximately 60-80% of cardiac output MAP target 🡪 > 65 mmHg
Pump speed	RPM	The revolutions per minute of the centrifugal pump Adjustments to RPM are made to target blood flow rate
Sweep gas flow	L/min	The rate of gas flowing through the oxygenator Usually started at 2 L/ min and titrated per PaCO2 levels Increased sweep gas flow Increases CO2 removal Lowers patient’s pCO2 level Decreases pH Decreased sweep gas flow Decreases CO2 removal Increases patient’s pCO2 level Increases pH
Fraction of inspired oxygen	FiO2	The concentration of oxygen delivered to the sweep gas by the blender Typically started at 100% and titrated down based on targeted ABGs PaCO2 🡪 target 35 – 45 mm Hg SaO2 VV-ECMO SaO2 target 🡪 85 – 92% VA-ECMO SaO2 target 🡪 > 95%

17 of 37

Common Indications

18 of 37

Acute respiratory distress syndrome (ARDS)
Pneumonia
Influenza
Hantavirus pulmonary syndrome
Acute cor pulmonale from massive pulmonary embolism
Pulmonary hypertension
Sepsis
Respiratory failure
Toxic ingestions
Arrhythmic Storm

Acute myocardial infarction
Cardiogenic shock
Postcardiotomy failure
Massive pulmonary embolism
Extracorporeal CPR
Cardiomyopathy
Myocarditis
Trauma
Acute exacerbation of heart failure
Primary transplant graft failure
Hypothermia with cardiac instability

19 of 37

Patient and Circuit Monitoring

20 of 37

Patient Monitoring
Hemodynamics	Continuous ECG monitoring Invasive arterial blood pressure Central venous pressure
Oxygenation and Perfusion	Pulse oximetry Pre-ductal: Reflects oxygen level in blood going to the brain and heart before it passes the ductus arteriosus Right hand Post-ductal: Reflects oxygen level in blood going to the lower body after mixing with blood coming from the ductus arteriosus Left hand or either foot Daily or serial ABGs Pertinent for adjusting: Sweep gas flow 🡪 controls how much CO2 is removed; based on PaCO2 levels FiO2 🡪 controls the percentage of oxygen delivered to the machine; based on PaO2 levels Lactate levels assess tissue perfusion and track prognosis and recovery
Anticoagulation Status	ACT, aPTT, or Anti-Factor Xa levels
Neurological and Neurovascular Checks	Limp perfusion Distal pulses Neuro status assessments
Urine Output	Indicator of organ perfusion Guides fluid balance Detects kidney injury
Cannula Position	Monitor to prevent recirculation in VV-ECMO and flow obstruction Detects dislodgement Helps avoid kinking and vessel injury
Circuit Pressures	Monitors mechanical functioning, detects blood clots, prevents hemolysis, and ensures safe blood flow

21 of 37

Clinical Significance of Pressure Monitoring

22 of 37

Anticoagulation and Laboratory Monitoring

23 of 37

Primary Anticoagulation

Anticoagulant	Purpose
Unfractionated Heparin (UFH)	Standard choice for ECMO Has a reversal agent Protamine sulfate
Direct Thrombin Inhibitors (DTIs)	Used if patient develops heparin-induced thrombocytopenia (HIT) Includes Bivalirudin or Argatroban

24 of 37

Laboratory and POC Monitoring Tests

Lab Test	Purpose
Activated Clotting Time (ACT)	Measures whole blood clotting time Used to manage blood-thinners to ensure adequate anticoagulation Target range 180 to 220 seconds
Activated Partial Thromboplastin Time (aPTT)	Measures the time it takes for blood to form a clot Used to measure adequate anticoagulation Target range of 1/5 to 2.5 times the patient’s normal baseline Primary lab test to titrate DTIs (direct thrombin inhibitors) such as Bivalirudin and Argatroban.
Anti-Factor Xa (Anti-Xa) Assay	Measures direct activity of heparin to prevent clotting and minimize severe bleeding Ranges 0.2 to 0.35 IU/ mL Recent guidelines suggest Anti-Factor Xa levels are a better guide to monitoring unfractionated heparin efficacy compared to ACTs and aPTT level.
Viscoelastic Hemostatic Assays (TEG/ ROTEM)	Analyzes overall clot strength and breakdown Shows bleeding and clotting risks immediately
Anti-thrombin Levels (AT)	Crucial to ECMO because it is the primary cofactor required for unfractionated heparin to prevent clots in the external circuit When anti-thrombin levels drop, heparin will not work as effectively Target AT between 50-80%
Platelet Counts	Monitored to balance the risk of severe bleeding vs. blood clots Usually kept above 100,000 / μL
Fibrinogen Level	Ensures adequate clotting potential Monitored to balance the risk of severe bleeding vs. blood clots Usually kept above 100 mg/dL but target of >150 mg/dL if active hemorrhage is present

25 of 37

Complications

26 of 37

Major Complications

Complication
Bleeding	Most common risk and complication Most often occurs at cannula insertion sites or surgical wounds Driven by blood-thinning medications
Thrombosis and Embolism	Clots can form within the ECMO circuit or within the patient’s blood vessels Clots will increase risk of stroke, organ damage, and circuit blockage
Neurological Injury	Both ischemic and hemorrhagic stroke can occur Seizures can also result from clots of bleeding within the brain
Infection	Infection may occur at cannula entry points Patient may have localized infection or develop systemic sepsis
Hemolysis	Can be caused by high pump speeds or high circuit resistance, thrombosis formation within the pump or membrane oxygenator, and/ or cannula issues (i.e., undersized cannulae or high negative P1) Monitor for pink or red-tinged urine, chattering pump, and plasma-free hemoglobin for elevated levels
Left Ventricular Thrombosis/ Dilation	VA-ECMO increases afterload and when mixed with a poor squeeze, blood will pool and become stagnant leading to left ventricular stretching and formation of dangerous blood clots
Acute Kidney Injury (AKI)	Hypoperfusion, circuit inflammation, non-pulsatile flow, hemolysis, and sepsis can lead to AKI Occurs in 50 – 70% of ECMO patients Approximately 40 – 50% of those patients will need CRRT or dialysis

27 of 37

Major Complications

Complication
Vascular and Limb Complications	Acute limb ischemia can be caused by reduced blood flow to cannulated limbs Compartment syndrome (more commonly occurs in peripheral VA-ECMO) can happen due to reperfusion injury or fluid overload. Monitor the antegrade ECMO sidearm sheath for kinks/ clots and avoid placing heavy blankets over the antegrade sheath Cannula placement can cause vessel tearing and perforation.
Mechanical Failures	Pump malfunction, membrane oxygenator failure, tubing breaks, or air entering the circuit (air embolus)
Differential Hypoxia (Also called Harlequin Syndrome or North-South Syndrome)	Specific to VA-ECMO and may lead to cerebral hypoxia, myocardial ischemia, and severe organ failure Although dangerous, it is a sign that cardiac muscle is getting stronger and improving Oxygenated blood is pumped retrograde up the aorta. When the native heart starts ejecting blood, but the lungs are still failing, the left ventricle will eject poorly-oxygenated blood. This blood will mix with the ECMO blood in the aorta causing a mixing point to form in the aorta. The arteries that are supplied first will suffer the effects of the hypoxia (i.e., coronary arteries, brachiocephalic artery, right subclavian artery, left common carotid artery, and left subclavian artery) Monitoring: Right radial or right brachial arterial line to monitor PaO2 Pulse oximeter to the right ear or right hand as well as left side of body for comparison May consider Near-Infrared Spectroscopy (NIRS) monitor for cerebral oximetry Treatment: Optimize lung function with diuretics or fluid restriction and increase PEEP Adjust ECMO settings by increasing total blood flow Modify configuration from VA-ECMO to a hybrid VAV-ECMO Manage cardiac output with an ECPELLA setup

28 of 37

(Hoyler et al., 2020)

(Image from Lego)

Harlequin Syndrome

29 of 37

Weaning, Decannulation, and Key Takeaways

30 of 37

With VV-ECMO, weaning occurs once there are signs of recovery such as improved native lung compliance, stable arterial oxygenation, and clear radiographic images. Weaning starts with reducing the sweep gas flow and FiO2 on the oxygenator. Blood flow is generally maintained > 2.5 L/ min to prevent circuit thrombosis. Once sweep gas in completely turned off, the patient must pass a trial monitoring for respiratory distress.

VA-ECMO patients show signs of recovery with return of native cardiac pulsatility, lowering lactate levels, resolving metabolic acidosis, and minimal requirements for inotropic and vasopressors.

Unlike VV-ECMO, VA-ECMO requires a stepwise reduction in blood flow rates. The patient will receive frequent echocardiograms to evaluation left ventricular ejection fraction, left ventricular outflow tract velocity time integral, and aortic valve opening. Trials are performed to confirm hemodynamic independence before decannulation occurs.

Decannulation readiness is determined by a multidisciplinary approach, which the team evaluates neurological integrity, coagulation profile, and renal & fluid balance.

Once the patient passes their weaning trials, decannulation planning can be initiated with consideration to reduce device-related infection, limb ischemia, or thrombotic events. Decannulation can be performed surgically or with percutaneous bedside closure. Once removed, ultrasound is frequently used to assess vascular patency. Patients will remain under close observation for post-cannulation monitoring. Patients are monitored for cardiac/ pulmonary decompensation, local site bleeding, and signs of retroperitoneal bleeding.

Evidence shows that early mobilization strategies reduces hospital stay, speeds up recovery, prevents severe muscle loss, and improves survival. Rehabilitation is best started while on ECMO and continues post-ECMO, subacute, and outpatient.

31 of 37

ECMO During TAVR

32 of 37

Emergency VA-ECMO may provide temporary cardiopulmonary support during refractory cardiac arrest or shock caused by complications such as coronary obstruction, annular or aortic rupture, tamponade, severe aortic regurgitation or valve embolization.

During an emergency TAVR complication, standard peripheral VA-ECMO is usually the initial configuration. Conversion to a hybrid V-VA ECMO support may be considered if severe pulmonary dysfunction produces persistent upper-body hypoxemia while cardiac function and native ejection begin to recover.

It is important to understand that ECMO stabilizes perfusion, but it does not correct the underlying mechanical complication. Definitive treatment must occur simultaneously.

(Image from The Cureus Journal of Medical Science)

1 of 37

2 of 37