Extracorporeal Membrane Oxygenation

OVERVIEW

• ECMO = extracorporeal membrane oxygenation
• extracorporeal life support (ECLS) may be a better term
• The extracorporeal circuit allows for the oxygenation and removal of carbon dioxide from blood
• used as a supportive strategy in patients who have a high risk of death despite conventional therapy

HISTORY

Neonates

• 1974 – used in the setting of meconium aspiration with severe hypoxaemia
• first RCT (Bartlett) – benefit shown but methodology was highly criticized
• 1993-1995, UK: ECMO vs conventional care -> trial stopped early due to benefit (NNT 3)

Adults

• 1972 – first survivor (NEJM) – young patient with post-traumatic respiratory failure
• 1979 – VA ECMO (ECMO with ventilation) vs ventilation alone -> high mortality in ECMO group
• 1986 — Gattinoni’s case series, VV, used for CO2 removal, increased survival but large blood loss/day

TYPES

• VV = veno-venous
• VA = veno-arterial: peripheral or central
• Veno-pulmonary artery ECMO (provides short-term right ventricular and respiratory support following LVAD insertion)
• high (2 venous cannulae) vs low flow (1 venous cannula)

INDICATIONS

acute, severe REVERSIBLE respiratory or cardiac failure with a high risk of death that is refractory to conventional management

• poor gas exchange
• compliance < 0.5mL/cmH2O/kg
• P:F ratio < 100
• shunt fraction > 30%

GENERAL CONTRAINDICATIONS

Absolute

• progressive non-recoverable cardiac disease (not transplant candidate)
• progressive and non-recoverable respiratory disease (irrespective of transplant status)
• chronic severe pulmonary hypertension
• advanced malignancy
• GVHD
• >120kg
• unwitnessed cardiac arrest

Relative

• age > 75
• multi-trauma with multiple bleeding sites
• CPR > 60 minutes
• multiple organ failure
• CNS injury

VV ECMO

• most common mode
• venous drainage from large central veins -> oxygenator -> venous system near RA
• support for severe respiratory failure (no cardiac dysfunction)
• pathology:

-> pneumonia
-> ARDS
-> acute GVHD
-> pulmonary contusion
-> smoke inhalation
-> status asthmaticus
-> airway obstruction
-> aspiration
-> bridge to lung transplant
-> drowning

• specific contraindications:
  — unsupportable cardiac failure
  — severe pulmonary hypertension
  — cardiac arrest
  — immunosuppression (severe)

• oxygenated blood returned to right side of heart so oxygen loss can take place through the lungs

Advantages

• normal lung blood flow
• oxygenated lung blood
• pulsatile blood pressure
• oxygenated blood delivered to root of aorta
• must be used when native cardiac output is high

Disadvantages

• no cardiac support
• local recirculation though oxygenator at high flows
• reverse gas exchange in lung if FiO2 low
• limited power to create high systemic arterial oxygen tension

Ventilation

• no need to ventilate at normal level
• must maintain alveolar volume and oxygenation
• RR 8-10, PEEP 15, TV 3-4mL/kg, PIP < 30, FiO2 0.4
• mandatory bronchoscopy and normal ventilation before decannulation

DETERMINATES OF FLOW WITH VENOUS LINES

• cannula size
• patency of vein
• suck down and kicking of line (vein collapsing around cannula)
  -> fluid load
  -> check intra-abdominal pressure
  -> add a second drainage line
  -> return cannula advanced into right ventricle (rare)

VA ECMO

• venous drainage from large central veins -> oxygenator -> arterial system in aorta
• support for cardiac failure (+/- respiratory failure)
• pathology:

-> graft failure post heart or heart lung transplant
-> non-ischaemic cardiogenic shock
-> failure to wean post CPB
-> bridge to LVAD
-> drug OD
-> sepsis
-> PE
-> cardiac or major vessel trauma
-> massive pulmonary haemorrhage
-> pulmonary trauma
-> acute anaphylaxis

• specific contraindications:
  — aortic dissection and severe AR

Peripheral VA ECMO

• back flow cannula used to prevent limb ischaemia
• oxygenated blood returned to aorta so lungs get little O2 rich blood -> may exacerbate lung ischaemia
• lower body receives better perfusion

Advantages

• good Q
• can create high oxygen tensions

Disadvantages

• relative lung ischaemia
• non-pulsatile blood flow
• possible poor perfusion of coronaries and cerebral vessels
• distal limb ischaemia
• risk of lung overventilation -> tissue alkalosis (monitor with ETCO2)

Central VA ECMO

• cannula into the ascending aorta or subclavian artery (needs back flow cannula)

Advantages

• no preferential perfusion to lower body
• no possibility of hypoxic perfusion of cerebral vessels
• can use very large cannulae (high flows)

Disadvantages

• need sternotomy and tissue dissection
• predisposes to severe bleeding

CIRCUIT

• cannulae
• tubing
• pump
• membrane oxygenator and heat exchanger
• gas blender

Cannulae

• 15-23 Fr
• arterial
• venous
• back flow
• bicaval cannulae (available)

Tubing

• therapeutic anticoagulation required (ACT 180-200)
• all tubing is heparin bonded
• blood must be kept flowing

Pump

• centrifugal or roller
• patients on VV don’t require a pump as patients heart is working

Oxygenator

• large surface area
• integrated heat exchange

MANAGEMENT

Patient

• assessment if ECMO is no longer required:

VA

• PAC to assess pulmonary pressures
• TOE
• increasing pulsatility visible on arterial trace or increased MVO2
• turn down gas flow to oxygenator to assess respiratory function

VV

• CXR
• improved compliance
• reduced PaCO2
• turn off gas flow to oxygenator and increase ventilation
• minimise lung injury: ventilate to recruit but minimize VALI, measure ETCO2 to assess native lung recovery

ECMO

• optimise circuit function: pressure measurement before and after oxygenator
• optimise ‘gas exchange’: set flow to provide adequate O2 delivery and CO2 elimination, mixed venous saturation monitoring, adjust blood volume to influence MAP
• anticoagulation: Hb 120-130, ACT 140-180, platelets > 80
• removal of cannulae: surgical or compression depending on type of insertion

Mechanical ventilation initial seeting for VV-ECMO (consensus guidelines and expert opinion)

• Tidal volume: < 4 ml/kg predicted body weight
• Plateau pressure: < 25 cmH₂O
• PEEP: 10-15 cmH₂O
• F_iO₂: titrated to maintain sats > 85%
• RR: 4 to 6 breaths per minute

COMPLICATIONS

• clot formation
• haemolysis (plasma free Hb < 0.1g/L)
• suck down and kicking (due to vessel collapse around access cannulae)
• air embolism
• bleeding
• pump failure
• decannulation
• circuit rupture
• cardiac arrest
• oxygenator failure
• VA: left ventricular overdistension -> APO, cardiac damage, pulmonary haemorrhage, pulmonary infarction, aortic thrombosis, cardiac or cerebral hypoxia, CVA 15%
• VV: cardiac arrest -> perform CPR

SUMMARY

• well established in neonates
• adults and VV:
  -> CESAR trial showed improved survival @ 6 months (63% vs 47%) in adults with severe acute respiratory failure
  -> ANZ ECMO Influenza investigators showed a mortality rate of 21% (lower than previous published studies)
  -> Systematic review on ECMO in H1N1 pandemic (Crit Care Med, 2010) found insufficient evidence for ECMO use among patients with H1N1

• adults and VA: little evidence so far
• CPR: used successfully in cardiac arrest
• retrieval: used successfully in retrieval medicine

-> established treatment
-> can decrease mortality
-> patient selection paramount
-> should be used in centres with appropriate expertise, experience and resources.

References and Links

LITFL

• CCC – Everything ECMO
• CCC – ECMO troubleshooting
• CCC – Pharmacokinetics and ECMO

Journal articles

• Bartlett RH, Gattinoni L. Current status of extracorporeal life support (ECMO) for cardiopulmonary failure. Minerva Anestesiol. 2010 Jul;76(7):534-40. PubMed PMID: 20613694. [Free Full Text]
• Baud FJ, Megarbane B, Deye N, Leprince P. Clinical review: aggressive management and extracorporeal support for drug-induced cardiotoxicity. Crit Care. 2007;11(2):207. Review. PubMed PMID: 17367544; PubMed Central PMCID: PMC2206443.
• Chauhan S, Subin S. Extracorporeal membrane oxygenation, an anesthesiologist’s perspective: physiology and principles. Part 1. Ann Card Anaesth. 2011 Sep-Dec;14(3):218-29. doi: 10.4103/0971-9784.84030. Review. PubMed PMID: 21860197. [Free Fulltext]
• Chauhan S, Subin S. Extracorporeal membrane oxygenation–an anaesthesiologist’s perspective–Part II: clinical and technical consideration. Ann Card Anaesth. 2012 Jan-Mar;15(1):69-82. doi: 10.4103/0971-9784.91485. Review. PubMed PMID: 22234027. [Free Fulltext]
• Ensminger SL, et al. The role of extracorporeal mechanical assists. (ECLS et al.) Applied Cardiopulmonary Pathophysiology 16: 192-201, 2012 [Free Fulltext]
• Gattinoni L, Carlesso E, Langer T. Clinical review: Extracorporeal membrane oxygenation. Crit Care. 2011;15(6):243. doi: 10.1186/cc10490. Epub 2011 Dec 8. Review. PubMed PMID: 22188792; PubMed Central PMCID: PMC3388693.
• Lindstrom SJ, Pellegrino VA, Butt WW. Extracorporeal membrane oxygenation. Med J Aust. 2009 Aug 3;191(3):178-82. Review. PubMed PMID: 19645652. [Free Fulltext]
• Pellegrino VA, Davies AR. CESAR: deliverance or just the beginning? Crit Care Resusc. 2010 Jun;12(2):75-7. PubMed PMID: 20513213. [Free Fulltext]
• Schmidt M, et al. Mechanical ventilation during extracorporeal membrane oxygenation. Crit Care 2014;18:203.

FOAM and web resources

• ECMO.ICU – Alfred ICU ECMO guidelines available as a free-to-access website.
• INTENSIVE – Intro to ECMO for New ICU Staff (Ken Hoffman, 2023)
• INTENSIVE – ECMO (collated ECMO resources)