Extracorporeal Membrane Oxygenation (ECMO) in the ICU

What is ECMO?

• An inflow cannula that drains venous blood from the patient
• A centrifugal pump to drive flow
• A membrane oxygenator (adds O₂, removes CO₂)
• A heat exchanger to regulate temperature
• An outflow cannula that returns blood to the patient

Two Main Types

1. Veno-Venous (VV) ECMO - Lung Support Only

• Blood drains from a vein and returns to a vein
• Provides gas exchange support (O₂ and CO₂) but no hemodynamic support
• Patient's own heart must still function
• Most common configuration: right femoral vein (inflow) + right internal jugular vein (outflow), with tip of inflow cannula at the IVC-atrial junction

2. Veno-Arterial (VA) ECMO - Heart + Lung Support

• Blood drains from a vein and returns to an artery
• Provides both gas exchange AND hemodynamic/circulatory support
• Common configuration: femoral vein drainage + femoral artery return (peripheral VA ECMO)
• Connected in parallel with the heart and lungs
• Can lead to LV distension and pulmonary edema - often requires additional LV unloading (IABP, Impella, inotropes)

Indications

VV-ECMO Indications (Respiratory)

• ARDS (pneumonia of any etiology, aspiration, inhalation injury, alveolar proteinosis, obstetric pathology)
• Airway obstruction, pulmonary contusion, bronchopleural fistula
• Status asthmaticus refractory to treatment
• Massive pulmonary hemorrhage / massive hemoptysis
• Pulmonary vasculitis
• Bridge to or support during lung transplantation

VA-ECMO Indications (Cardiac)

• Cardiogenic shock refractory to inotropes and vasopressors
• Cardiac arrest - used as extracorporeal CPR (ECPR)
• Bi-ventricular failure
• Acute myocarditis (especially fulminant myocarditis - recent meta-analysis confirms LV unloading improves survival in pediatric fulminant myocarditis on ECMO, PMID 40211564)
• Post-cardiotomy shock (failure to wean from bypass)
• Bridge to VAD implantation or cardiac transplant
• Myocardial stunning with expected recovery
• Massive pulmonary embolism with hemodynamic collapse
• Refractory ventricular arrhythmias
• Drug/toxin-induced cardiac failure

ECPR (Extracorporeal CPR)

Contraindications

Absolute

• Irreversible end-organ damage (brain death, severe pre-existing neurological injury)
• Advanced malignancy or other terminal illness with no realistic recovery
• Uncontrolled bleeding that cannot be managed (relative to anticoagulation requirements)
• Severe aortic regurgitation (VA ECMO contraindicated)

Relative

• Prolonged mechanical ventilation at high pressures (> 7-10 days) - reduces lung recovery potential
• Immunosuppression (relative, context-dependent)
• Advanced age (no absolute cutoff; patient selection-dependent)
• Morbid obesity limiting cannulation
• Peripheral vascular disease limiting femoral access (consider axillary or carotid approach instead)

Procedure in the ICU

Pre-Cannulation Preparation

1. Confirm diagnosis and failure of maximal conventional therapy
2. Airway secured (intubation), central venous access, arterial line
3. Baseline labs: ABG, CBC, coagulation profile, BMP, blood crossmatch
4. Bedside echo to assess cardiac function and guide cannula placement
5. Consent (or emergency waiver)

Cannulation Technique

• Ultrasound-guided access to the right common femoral vein (inflow) with a large-bore multi-orifice cannula (21-25 Fr)
• Seldinger technique: wire → serial dilation → cannula placement
• Outflow cannula placed via right internal jugular vein (15-20 Fr), tip advanced to right atrium/SVC junction
• Position confirmed by fluoroscopy or transesophageal echocardiography (TEE)
• Alternatively, a dual-lumen single cannula (e.g., Avalon cannula) can be placed via the right IJ alone - drains from SVC and IVC, returns to right atrium directed toward tricuspid valve

• Inflow: femoral vein (venous drainage cannula, 21-25 Fr)
• Outflow: femoral artery (arterial return cannula, 15-17 Fr)
• A distal perfusion catheter (5-6 Fr) is inserted into the superficial femoral artery to prevent ipsilateral limb ischemia
• Position confirmed by fluoroscopy or echo

Circuit Initiation and Settings

• Start flow at 2-3 L/min, gradually increase to 4-6 L/min (targeting 60-80 mL/kg/min)
• Sweep gas (gas flow through oxygenator): primarily controls CO₂ removal
• FDO₂ of gas blender: controls oxygenation
• Once on VV-ECMO: institute "lung rest" - reduce ventilator settings (TV 3-4 mL/kg IBW, Pplat < 25 cmH₂O, FiO₂ 0.3-0.4, PEEP 8-10 cmH₂O)
• On VA-ECMO: vasopressors titrated to MAP > 60 mmHg, < 80 mmHg to avoid LV overdistension

Anticoagulation

• Unfractionated heparin infusion is standard (target aPTT 60-80 sec, or ACT 180-220 sec)
• Initiated at cannulation (heparin bolus 50-100 U/kg)
• Platelet monitoring required (target > 50,000-80,000/µL; circuit consumption causes thrombocytopenia)
• Bivalirudin used as alternative when HIT is suspected

Monitoring on ECMO

• Continuous: SpO₂, ETCO₂, circuit pressures (pre/post pump, pre/post oxygenator), flow
• Regular: ABG, ACT/aPTT, CBC, metabolic panel, lactate, CXR
• Echo: assess cardiac function, volume status, cannula position
• Watch for recirculation (VV-ECMO) - blood returns from outflow and is immediately drawn back into inflow cannula; reduces effective oxygen delivery

Weaning and Decannulation

VV-ECMO Weaning

• Gradual reduction of sweep gas flow (reduce to 1-2 L/min)
• Monitor SaO₂ and PCO₂ tolerance
• Trial off sweep gas ("sweep off" trial) with ventilator at moderate settings
• If patient maintains acceptable gas exchange for 1-4 hours: decannulate
• Ventilator settings at wean: FiO₂ ≤ 0.6, Pplat < 30, PEEP 8-10 cmH₂O

VA-ECMO Weaning

• Gradual flow reduction (500 mL/min every 6-12 hours)
• Echo at each step to assess LV/RV contractility, cardiac output
• Minimum flow ~1 L/min before trial off
• Maintain anticoagulation throughout weaning

Decannulation

• Remove cannulas with manual pressure (percutaneous) or surgical closure
• Confirm hemostasis before sedation reversal

Complications

Key Clinical Points for the ICU

• ECMO is a bridge - to recovery, transplant, or a durable device. It is not destination therapy.
• Timing matters: a 2024 National Inpatient Sample analysis showed each 12-hour delay from admission to VA ECMO initiation increased in-hospital mortality by 6%.
• Prone positioning while on VV-ECMO is feasible and safe (2023 PRONECMO trial showed no difference in 60-day ECMO-free survival but confirmed feasibility).
• Lung-protective (ultra-protective) ventilation must be maintained on VV-ECMO to minimize ventilator-induced lung injury.
• ECMO programs require dedicated, well-trained multidisciplinary teams - outcomes are highly institution-dependent.