Overview
Definition:
Extracorporeal Membrane Oxygenation (ECMO) is a life-support technology that provides prolonged cardiac and/or respiratory support to patients whose hearts and/or lungs are so severely diseased or injured that they cannot function adequately
It acts as an artificial heart and lung, allowing these organs to rest and recover.
Epidemiology:
Pediatric ECMO use varies by indication and region, with neonates representing the largest patient group
Common indications include persistent pulmonary hypertension of the newborn (PPHN), congenital diaphragmatic hernia (CDH), meconium aspiration syndrome (MAS), and severe congenital heart disease
The incidence of ECMO use in neonates is estimated to be between 1-4 per 100,000 live births annually.
Clinical Significance:
ECMO is a salvage therapy for critically ill pediatric patients with reversible respiratory or cardiac failure, offering a bridge to recovery, transplant, or other definitive therapies
Its appropriate and timely application can significantly improve survival rates in otherwise fatal conditions
Understanding its indications and the principles of cannulation is paramount for pediatric intensivists and surgeons.
Indications
Respiratory Failure:
Severe, life-threatening respiratory failure unresponsive to maximal conventional therapy
This includes conditions like PPHN, MAS, severe pneumonia, ARDS, severe viral bronchiolitis, and CDH.
Cardiac Failure:
Severe, life-threatening cardiac failure unresponsive to maximal medical and mechanical support
Indications include congenital heart disease with biventricular failure, myocarditis, and post-cardiac surgery failure.
Bridge To Transplant:
ECMO can serve as a bridge to cardiac or lung transplantation for patients with end-stage organ disease.
Contraindications:
Absolute contraindications are rare and include irreversible central nervous system damage, unrepaired congenital anomalies incompatible with survival, and terminal illness
Relative contraindications include prematurity (especially very low birth weight infants), prolonged mechanical ventilation prior to ECMO, and severe coagulopathy.
Ecmo Modes And Cannulation Basics
Ecmo Types:
Veno-arterial (VA) ECMO provides both cardiac and respiratory support by draining venous blood, oxygenating it, and returning it to the arterial system
Veno-venous (VV) ECMO provides primarily respiratory support by draining venous blood, oxygenating it, and returning it to the venous system.
Cannula Placement Venovenous:
For VV ECMO, typically two cannulas are used: an inflow cannula draining deoxygenated blood from a large vein (e.g., right atrium via superior vena cava or inferior vena cava) and an outflow cannula returning oxygenated blood to the right atrium.
Cannula Placement Venoarterial:
For VA ECMO, an outflow cannula is usually placed in a major artery (e.g., carotid artery or femoral artery) to return oxygenated blood to the systemic circulation, and an inflow cannula drains venous blood from a major vein (e.g., right atrium via superior vena cava or inferior vena cava).
Cannula Sizes And Selection:
Cannula size is critical and is determined by patient weight and desired blood flow
For neonates and infants, smaller gauges (e.g., 8-14 Fr) are used
For older children, larger gauges are employed
Cannula material and tip design are important to minimize trauma and thrombosis.
Cannulation Procedure Considerations:
Cannulation is typically performed surgically or percutaneously by experienced teams
Site selection depends on the ECMO mode, patient anatomy, and surgeon preference
Careful attention to anatomical landmarks, secure fixation, and sterile technique is essential.
Patient Selection And Preparation
Patient Assessment:
A multidisciplinary team (intensivist, surgeon, perfusionist, nursing) assesses the patient for suitability for ECMO
This involves reviewing hemodynamics, respiratory status, neurological function, and potential reversibility of the underlying disease.
Optimization Prior To Ecmo:
While ECMO is an urgent therapy, attempts are made to optimize the patient beforehand, including mechanical ventilation, inotropic support, and fluid management, if time permits.
Team And Equipment Readiness:
Ensuring a trained ECMO team is available 24/7 and that all necessary equipment (ECMO circuit, pumps, oxygenators, monitoring devices) is readily accessible and functional is crucial.
Informed Consent:
When possible, informed consent from parents or guardians is obtained, discussing the risks, benefits, and alternatives to ECMO.
Monitoring And Management On Ecmo
Circuit Monitoring:
Continuous monitoring of blood flow, sweep gas flow, temperature, and oxygenator performance is essential
Regular checks for circuit thrombosis or membrane fouling are performed.
Hemodynamic Monitoring:
Close monitoring of arterial blood pressure, central venous pressure, and cardiac output (if measurable) is vital
Echocardiography is frequently used to assess cardiac function and cannula position.
Respiratory Monitoring:
Arterial blood gases (ABGs) are used to guide ventilator settings (if applicable) and sweep gas flow to maintain adequate oxygenation and ventilation
Chest X-rays are obtained to assess lung status and cannula position.
Anticoagulation Strategy:
Heparin is the cornerstone of anticoagulation on ECMO to prevent circuit thrombosis
Activated Clotting Time (ACT) is monitored frequently (e.g., every 1-2 hours) to maintain a therapeutic range (typically 180-220 seconds, but varies by center).
Complication Management:
Vigilance for complications such as bleeding, thrombosis, infection, and neurological events is paramount
Prompt recognition and management are critical for patient outcomes.
Complications Of Ecmo
Bleeding Complications:
Hemorrhage is common, especially due to anticoagulation
It can occur at cannulation sites, intracranial, or within organ systems.
Thrombosis And Embolism:
Formation of clots within the ECMO circuit or on cannulas can lead to impaired function or embolization to vital organs.
Neurological Complications:
Stroke, intracranial hemorrhage, and seizures can occur, particularly in neonates with underlying risk factors.
Infection:
Central line infections, bloodstream infections, and pneumonia are risks associated with prolonged critical illness and invasive support.
Organ Dysfunction:
Prolonged ECMO can be associated with multi-organ failure, including renal, hepatic, and gastrointestinal dysfunction.
Key Points
Exam Focus:
Understand the difference between VV and VA ECMO and their primary indications
Know the key cannulation sites and general principles of size selection
Recognize major complications and their management principles.
Clinical Pearls:
ECMO is a team sport
effective communication and coordination between all disciplines are vital
Always consider reversibility of the underlying condition before initiating ECMO
Prompt recognition of circuit issues or patient deterioration is crucial.
Common Mistakes:
Inadequate anticoagulation leading to circuit thrombosis or excessive anticoagulation leading to hemorrhage
Failure to recognize early signs of circuit failure or patient decompensation
Inappropriate patient selection or delayed initiation of therapy.