• assess CIN
• shared decision making with patient and family
• ensure failure of "conventional" therapy
  • Recruitment manoeuvres
  • Prone positioning
  • NO / inhaled prostacylin
  • Diuresis
  • Fluid resuscitation and ⬇PEEP to improve V/Q mismatch

• VA ECMO = arterial return
• VV ECMO = venous return

• acute reversible severe cardiopulmonary failure (predicted mortality 80%)
• B = respiratory = VV
  • O2 = hypoxia / hypoxaemia / hypoxic respiratory failure
    • despite optimisation of O2
    • PaO2 / FiO2 (P:F ratio) < 100
    • Shunt fraction > 30%
    • FiO2 > 0.8
  • CO2 = hypercapnia / hypercarbia / hypercapnic respiratory failure
    • pH < 7.25
    • PaCO2 > 60 mmHg
  • Ventilation
    • compliance < 0.5 mL/cmH2O/kg
    • Pplat > 30 cm H2O
    • Vt < 6 mL/kg predicted body weight
    • air leaks / bronchopleural fistula (eg. trauma)
• C = cardiovascular = VA
  • BP = hypotension
    • SBP < 90 mmHg on inotropes
  • Lactate > 5 mmol/L
  • Echo
    • confirmation of low CO
    • LVEF < 25%
  • Malperfusion
    • skin = mottling
    • renal = oliguria > 4 hr

• progressive / non-recoverable / irreversible disease
  • C = cardiac disease (not transplant candidate)
  • B = respiratory disease
  • C = chronic severe PHTN
  • I = advanced malignancy
  • I = GVHD
• CIN to anticoagulation
  • recent surgery
  • uncontrolled bleeding
  • ICH

• Recirculation

  • Cannula tips are too close together
  • Oxygenated blood will return through cannula with less oxygenated blood reaching systemic circulation

• 7-14 days = cannulae / circuit issues

• Major = bleeding and thromboembolism

• C = Bleeding = 30-50%

  • large bore vascular access
  • due to continuous ACT and platelet dysfunction

• C = Differential hypoxia = Harlequin syndrome = North-South

  • concerns = cardiac and cerebral ischaemia
  • poorly oxygenated blood enters the coronary and carotid As
  • prerequisites
    • 1: Peripheral VA-ECMO
    • 2: Coexistent respiratory failure, causing poor oxygenation
      • The blood entering LA/LV is poorly oxygenated
    • 3: Significant intrinsic CO = good pulsatile BQ on arterial trace
      • Adequate native (anterograde) CO to compete against ECMO (retrograde) BQ
      • Hypoxaemic blood leaves heart, first to BCT (right arm, and RCCA), then LSCA (left arm and LCCA), then Ao (legs)
    • North-South phenomenon = marked SpO2 differential
      • right arm (lower SpO2) >> left arm / lower limbs (higher SpO2)
    • will not occur on CENTRAL VA-ECMO because return cannula is sutured into proximal Ao

• C = Lower limb ischaemia

  • Femoral ischaemia = occlusion by cannula and retrograde flow
  • Can use reperfusion distal cannula

• C = LV distension and ⬆AL

• H = Thromboembolism

  • Thrombus formation within ECMO circuit
    • And subsequent thromboembolism
  • greater impact with VA-ECMO > VV-ECMO (due to site of embolism)

• Complications of VA-ECMO

• C = ⬆LV afterload and LV dilatation

• VV-ECMO
  • oxygenator
  • Configurations
    • Femoral-jugular
      • Drainage = femoral V
      • Return = IJV
      • Most used, easiest configuration, minimal recirculation
    • Femoral-femoral
      • Drainage = femoral V, advanced to mid-IVC
      • Return = Femoral Vein, usually contraL femoral V, but more proximal / RA
      • Allows head movement, some recirculation
    • Jugular-femoral
      • Drainage = jugular
      • Return = femoral Vein
      • Significant recirculation
• VA-ECMO
  • oxygenator + PUMP
  • Configuration
    • Peripheral
      • Drainage = femoral vein, advanced to mid-IVC
      • Return = arterial
        • Femoral A, advanced to proximal Aorta
        • Axillary A
        • Carotid (infants)
        • Competes with native anterograde circulation from heart = the cause of Harlequin syndrome, femoral ischaemia, and LV distension (see above)
      • Central
        • Sternotomy and surgical cannulation of RA and Aorta
        • Drainage = RA
        • Return = Aorta
        • Vent
          • to allow control of LV decompression
          • usually via Right superior pulmonary V / LV apex
• VVA-ECMO
  • Second cannula for venous drainage
    • Usually IJV
    • Further ⬇preload to LV, minimising risk of distension
• Anticoagulation
  • Heparin
  • ACT 180-210

• 1: Drainage cannula = venous cannula
• 2: reservoir
• 3: pump
• 4: membrane oxygenator / heat exchanger
• 5: filter
• 6: Return cannula = arterial / venous

• centrifugal or roller
• micro-filter bubble trap added to arterial outflow

• large surface area
• integrated heat exchange
• Oxygenation
  • controlled by blood flow rate
• CO2 removal
  • controlled by countercurrent flow of fresh gas

Weaning off ECMO

• VV-ECMO
  • Gas sweep turned off
  • No fresh gas passes through oxygenator
  • Observe native lung function
  • Turn off pump and return blood
• VA-ECMO
  • Clamp drainage and infusion lines
  • Observe native circulatory function

https://litfl.com/ecmo-extra-corporeal-membrane-oxygenation/

https://www.aci.health.nsw.gov.au/__data/assets/pdf_file/0003/624279/ACI-ECMO-Adult-Clinical-Practice-Guide.pdf

https://www.uptodate.com/contents/extracorporeal-membrane-oxygenation-ecmo-in-adults#H15

https://intensiveblog.com/different-hypoxia-va-ecmo/

Cannulation techniques for extracorporeal life support, 2017