ECMO Application during Phase 1
Phase1: Adequate resources exist to provide Mechanical Ventilation and ECMO as per existing patient selection guidelines and patients suitable for ECMO support will be cohorted at a specialty site.
The current Alfred ECMO Guideline provides criteria for the application of ECMO for virally triggered lung injury. This guideline takes into account the interaction between disease, age and comorbidities that form an essential component of patient selection and this approach will be applied during the early phase of the pandemic.
Expansion of existing state-wide ECMO capacity during the pandemic will be limited and cohorting of patients to a speciality ECMO centre will occur. Therefore, it is particularly important to discuss the initiation of ECMO with a centralised referral service prior to ECMO initiation.
It is important to recognise severe viral pneumonitis may differ from other (non-viral) ARDS pathologies. Patients with viral ARDS may have earlier and more profound hypoxia, may be more responsive to proning and lung recruitment, and may have a better prognosis relative to the degree of hypoxia without ECMO.
These factors have implications for the utilization of ECMO during a viral pandemic.The Victorian ECMO Service is staffed to receive referrals 24/7 via ARV. In order to maximise any therapeutic effect of ECMO, all decisions regarding the use of ECMO should be made to this service. Referrals may occur in any phase of illness but most commonly will be made after initiation of invasive mechanical ventilation. There will be a strong preference to avoid prolonged NIV support in patients with diagnosed or suspected COVID-19.
Triggers for ECMO Referrals
All patients should receive endotracheal intubation, safe lung ventilation, early paralysis and assessment of circulatory function prior to referral to VES.
Timing of referral will generally be determined by the degree of hypoxia, the ability to deliver adequate ventilation at safe airway pressures, the response to prone ventilation and the degree and trajectory of circulatory support following intubation. Significant clinical concern by senior intensive care specialists is sufficient to trigger referral to the VES.
The following physiological triggers would also justify referral:
- Degree of hypoxia following intubation (early)
- SaO2 <80% (persisting for 3-10 min)
- SaO2 < 88% (persisting for 30-60 min)
- Degree and trajectory of support required for maintenance of MAP and CO
- Vasopressor > 0.5micrograms/kg/min (Noradren equivalent)
- Inotrope > 0.2microgram/Kg/min(milrinone/adrenaline)
- Response to prone ventilation
- P/F < 80 (6 hours following return to supine position)
- P/F <50 (3 hours following return to supine position)
- pCO2 > 60 / pH <7.2 (6 hours following return to supine position)
- Need for proning beyond 3 days
In addition referrals may be triggered at different phases:
- Prior to prone ventilation or in centres untrained in the application of prone ventilation
- Concerns about the response to proning or complications from proning
- Failure to progress days or weeks after initiation of protective lung ventilation
Diagnostic groups for COVID-19
Case Selection Principles
This summary provides guidance of case selection for ECMO according to likelihood of enduring patient benefit from treatment. It is based on
- The form of respiratory failure as per diagnostic COVID category below
- Age and pre-existing comorbidities (see chronic modifier)
- The presence of secondary organ damage (see acute modifier)
Once the diagnostic category is established proceed to the eligibility chart for VV ECMO which includes description of the modifiers.
COVID Group 1
Favourable Diagnostic Category (Score =1):
Higher likelihood of survival and long-term benefit: should receive ECMO if patients fulfil severity criteria and adequate resources are available. Refer early and prepare for ECMO initiation
- Acute severe pneumonitis syndrome features:
- Severe hypoxaemia refractory to prone ventilation and a trial of high PEEP (>15cmH20)
- Rapidly (early after presentation) progressive lung infiltrates (bilateral and symmetrical) typical of ARDS, intubated for <7days
- Poor pulmonary compliance (dynamic compliance TV/(PIP – PEEP) <20ml/cmH2O)
- Acute severe pneumonitis syndrome with early severe acute right heart failure
COVID Group 2
High Risk Diagnostic Category (Score =2)
Uncertain outcome benefit following the application of ECMO: application of ECMO in this group should only occur following detailed patient assessment and discussion with a senior panel of ECMO consultants. Application of ECMO will depend on specific patient and disease factors and ECMO capacity.
- Any of the following ventilatory challenges beyond second week of hospitalisation with persistent infiltrates and concern about ventilator or patient induced lung injury
- Static compliance < 20ml/cmH2O (need to paralyse and test plateau pressure, dynamic compliance may overestimate)
- Requiring neuromuscular blockade (infusion or recurrent boluses e.g. for pCO2 control)
- Patient ventilator dyssynchrony
- Barotrauma as a result of MV
- Acute circulatory and respiratory failure with features of distributive or cardiogenic shock prior to established multiorgan failure and high lactate
- Secondary bacterial superinfection following pneumonitis/ARDS with asymmetrical lung disease
COVID Group 3
Unfavourable Diagnostic Category (Score =3)
Low likelihood of patient benefit with the application of ECMO: application of ECMO where these processes are present should be avoided. Application of ECMO on compassionate grounds MUST involve a senior panel consensus.
- Severe acute circulatory and respiratory failure with established organ failures
- Prolonged MV cases with severe comorbidities or immunosuppression
- ECPR cases
Later phases of pandemic
Additional service design required to adapt to resource constraint in latter phases of the pandemic (beyond VES design):
Phase 2a: ECMO capacity exceeded at specialty site. ICU capacity within the region still exists.
Phase 2b: ICU capacity to provide mechanical ventilation across the region is exceeded.