Extracorporeal Membrane Oxygenation — temporary mechanical life support for severe cardiac and/or respiratory failure refractory to conventional therapy
Core Concept
ECMO bypasses the heart and/or lungs by circulating blood through an external circuit containing a membrane oxygenator (artificial lung) and a centrifugal pump. It provides gas exchange and/or haemodynamic support while allowing the native organs time to recover, or as a bridge to transplantation or a ventricular assist device (LVAD).
VV-ECMO — Veno-Venous
Purpose: Respiratory support only
Blood drained from venous system → oxygenated → returned to venous system
Native heart must maintain circulation
Drainage: Right femoral vein
Return: Right internal jugular vein
SpO2 target: 85–95% (acceptable in severe ARDS)
Recirculation is a key concern
VA-ECMO — Veno-Arterial
Purpose: Cardiac + respiratory support
Blood drained from venous system → returned to arterial system
Unloads the heart — reduces preload
Peripheral: Femoral vein → femoral artery
Central: Right atrium → ascending aorta
Provides 60–80% of cardiac output
Higher risk of thromboembolism and stroke
Indications for ECMO
🫁 VV-ECMO Indications
PaO₂/FiO₂ ratio <80 mmHg despite optimal mechanical ventilation
pH <7.2 with PaCO₂ >80 mmHg (hypercapnic respiratory failure)
Severe ARDS (Berlin definition — severe)
MERS-CoV pneumonia / SARS-CoV-2 ARDS (highly relevant in GCC)
Murray Score / RESP Score
Use the Murray Lung Injury Score (>3.0) or RESP Score to predict ECMO survival benefit. ELSO guidelines recommend ECMO referral when these thresholds are met before patient deteriorates further.
Contraindications
🚫 Absolute Contraindications
Irreversible condition with no plan for transplant or LVAD (futile)
Severe irreversible CNS damage (anoxic brain injury, massive stroke)
Metastatic/advanced malignancy with poor prognosis
Uncontrolled systemic bleeding with absolute anticoagulation contraindication
Prolonged CPR without ECMO initiation (>60 min without return of perfusion)
⚡ Relative Contraindications
Severe aortic regurgitation (VA-ECMO — increases afterload)
Aortic dissection
Immunocompromised with no reversible cause
Morbid obesity (technical challenges)
Advanced age with multiple organ failure
Heparin-induced thrombocytopenia (HIT) — alternative anticoagulation needed
ECMO Team Structure
👩⚕️ ECMO Specialist Nurse
Primary bedside ECMO management
Circuit monitoring and troubleshooting
Patient assessment and safety
Documentation and handover
Family education and support
Highest ICU Pay Grade
🩺 Perfusionist
Circuit priming and setup
Technical troubleshooting
Circuit changes and emergencies
Liaison with surgical team
👨⚕️ Intensivist / Cardiac Surgeon
Intensivist: medical management, weaning decisions
Saudi Arabia documented the world's largest experience with ECMO for MERS-CoV ARDS following the 2012 outbreak and subsequent cases. KFSH Riyadh published landmark data on VV-ECMO survival in MERS patients. This positioned Saudi Arabia and GCC as global leaders in respiratory ECMO for viral pneumonia — a skill set that became critical again during COVID-19. Nurses trained in GCC ECMO centres carry internationally recognised experience.
ECMO Circuit Components
Understanding every component of the circuit is essential for safe bedside management
🔵 Cannulas
Venous drainage cannula: Removes deoxygenated blood from the patient. Large bore (21–25 Fr) to optimise flow
Return cannula: Returns oxygenated blood to the patient. Smaller (15–21 Fr)
Placed under echo and fluoroscopic guidance
Secured with sutures and dressing — nurse checks security q1h
Air bubbles in cannula = emergency
⚙️ Centrifugal Pump
Magnetically driven impeller — no rollers (less haemolysis)
Harlequin Syndrome (North-South / Differential Hypoxia) — VA-ECMO
In peripheral VA-ECMO, oxygenated blood from ECMO enters femoral artery and travels retrograde. Native heart ejects blood from left ventricle (potentially poorly oxygenated due to lung failure). These two streams meet in the aorta — coronary arteries and brain may receive desaturated native heart blood. Sign: right hand SpO₂ LOWER than lower limb SpO₂. Action: optimise mechanical ventilation, consider switching to central cannulation or adding VV component (VAV-ECMO).
Aortic valve opening: Must open at least intermittently; failure to open = LV distension risk → unloading strategy (IABP, Impella, surgical vent)
LV distension: Sign of afterload mismatch — can cause pulmonary oedema and LV clot
Cannula positions: Confirm tip positions with each echo
Pericardial effusion: Post-cardiac surgery — tamponade risk
RVOT obstruction: Can cause suction alarms in VV-ECMO (septal shift)
Nurse role: Assist with echo (patient positioning, connection of pads), document findings, escalate LV distension signs
ECMO Complications Overview
Complications are common — early recognition by the bedside nurse is critical. Average incidence in ELSO registry: major bleeding 30%, thrombosis 18%, neurological 8%
🚨
Emergency Situations — Know These Responses
Accidental decannulation: apply direct pressure immediately, call for help, prepare clamping. Circuit failure: clamp both limbs, initiate manual ventilation/CPR as appropriate. Air embolism: clamp lines, position patient left lateral Trendelenburg, call ECMO team stat.
Trial off: Stop sweep gas entirely (or clamp gas tubing). Blood still flows through circuit but no gas exchange — pure native lung trial. Continue 1–4 hours.
Pass criteria: SpO₂ >92%, PaO₂ >60 mmHg, pH >7.3 on ventilator settings of FiO₂ <0.6, PEEP ≤10
Fail criteria: SpO₂ <85%, rising CO₂, haemodynamic compromise — resume full ECMO support
Renal function: acute tubular necrosis common post-ECMO
Liver function: hepatic congestion in VA-ECMO
ECMO Rehabilitation
🏃 Early Mobilisation on ECMO — Growing Evidence
Awake ECMO (avoiding sedation + mechanical ventilation) and early physiotherapy is increasingly practiced, particularly in lung transplant bridge patients
Evidence-Based Practice
Passive range of motion: start day 1
Sitting to chair: possible with dual-lumen VV cannula (RIJ only)
Ambulation: achieved in select patients on ECMO bridge to transplant
Reduces ICU-acquired weakness
Improves patient outcomes and transplant candidacy
Safety Requirements for Mobilisation
ECMO flow stable ≥ target during activity
No arrhythmias at rest
Cannulas well secured — extra skin sutures if mobilising
Stop activity: SpO₂ fall >5%, haemodynamic instability
ECMO Withdrawal — Ethical Considerations
💛
When Recovery Does Not Occur
If ECMO fails to achieve weaning despite optimal management and no viable bridge option (transplant/LVAD not feasible), the ECMO team together with patient/family and ethics committee may consider compassionate withdrawal. The nurse plays a key role in: family communication and support, ensuring comfort care is maximised, coordinating palliative care team, supporting staff wellbeing during withdrawal. This is one of the most emotionally demanding situations in critical care nursing.