Issue 9: ECMO in COVID-19 patients (MAY 1, 2020)
EXTRACORPOREAL MEMBRANE OXYGENATION IN COVID-19 PATIENTS
- Venovenous (VV) extracorporeal membrane oxygenation (ECMO) is the exchange of venous oxygen and carbon dioxide within an extracorporeal circuit that includes a pump, membrane oxygenator plus percutaneous venous drainage and return cannulae1.
- ECMO (if available) may be an option for COVID-19 patients with refractory respiratory failure unresponsive to conventional management2. Use of VV-ECMO in ARDS has reportedly helped to reduce mortality in many patients (e.g., MERS vs. those not receiving ECMO3,4. ECMO may provide improved oxygenation where other approached have failed, and could facilitate “rest ventilation5,6.
- Since patient prognosis is worse with time on invasive mechanical ventilation >7 days, these should be excluded. However, these general guidelines may not apply to specific COVID-19 patients depending on local circumstances2,7. Notably, a BMI>40 may be considered a relative contraindication for VV-ECMO. Reports suggest venoarterial (VA) ECMO may be beneficial for eligible COVID-19 patients who develop myocarditis and eventually refractory cardiogenic shock8-10.
PHENOTYPES OF HYPOXEMIC RESPIRATORY FAILURE
- Two type are known: Hypoxemic respiratory failure with normal or high compliance, and those with low compliance and severe hypoxia1. ECMO may be more appropriate for cases of the latter.
- Also, patients with >1 known risk factors for poor outcomes (e.g., age >65 years; co-morbidities; extrapulmonary organ failures; hyperinflammation; hypercoagulability; leukopenia; and myocardial injury) are less likely to be successfully supported with VV-ECMO11.
- VA-ECMO may be better suited for COVID-19 patients with myocarditis-related cardiogenic shock.
FIRST EXPERIENCES WITH ECMO
- A multi‐institutional collaborative in Pennsylvania for COVID‐19 patients was utilized to obtain clinical data on the first 10 critically ill COVID‐19 patients (ages: 31-62) who developed acute hypoxic respiratory failure secondary to ARDS requiring emergent salvage VVECMO12. From the onset of symptoms, the median time to hospital admission, intubation, and ECMO was 4, 8, and 11 days, respectively. One patient required RRT the day before cannulation. Initial ECMO flows were 3.5 to 5.8 L/min, and six patients required initial vasopressors for hemodynamic stabilization on ECMO. 40% of patients received remdesivir, 100% received hydroxychloroquine, and 30% of patients received IL‐6 inhibitors for cytokine storm. One mortality occurred, two patients were successfully weaned, and one patient is on a weaning course.
- In a multi-state study performed over 24 days, 32 patients from 9 different hospitals (largest cohort to date) were placed on VV-ECMO. The median time on ECMO was ~175 for survivors vs. ~135 hrs for non-survivors13. Of those, 17 remain on ECMO, 10 died prior to or shortly after decannulation, and 5 are alive following discontinuation of ECMO. Four of five survivors received intravenous steroids, 3 of 5 survivors received (Remdesivir, 2 of 5 got IL-6R monoclonal antibodies (Tocilizumab or Sarilumab), and 1 of 5 survivors received hydroxychloroquine.
A European perspective
Details from 333 patients treated ECMO (90 clinical, 17 countries) found a mortality rate was 17.1% 95%CI: 13.1-21.1%). VV-ECMO was used in 93.7%14. There was no association with gender (p=0.788), but a significant association was found patients >60 years of age (OR: 4.80 [95% CI: 1.64-14.04], p=0.004).
- A retrospective review of 12 cases reported a mean duration on ECMO of 11.3 day (range: 3-28). Expected survival is 7/12 (two in a coma); five are not expected to survive15.
- Zhen et al. applied an aggressive strategy to 8/16 COVID-19 patients: FiO2<40%, tidal volume: 2-4 mL/kg, plateau pressure <25 cmH2O, and respiratory rate: 8-10 times/min, not exceeding 1416. ECMO goals included maintaining patient’s hemoglobin level >11g/dL through support; and continuously monitor peripheral arterial oxygenation, ECMO premembrane/postmembrane oxygenation, percutaneous oxygenation, and mixed venous oxygenation monitored. Gastrointestinal dysfunction and increased abdominal pressure may directly affect ECMO flow and cause instability. Outcomes reported were 50% mortality; 37.5% weaned (22, 40, 47 days); and one still on ECMO. Authors suggest that “ensuring effective, timely, and safe ECMO support in COVID-19 is key to improving clinical outcomes.”
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