Background:
Extracorporeal support has improved survival in select neonatal and
pediatric patients for over forty years. Over the last two decades,
extracorporeal membrane oxygenation (ECMO) has emerged as an acceptable
and potentially beneficial rescue modality in select adult populations.
In severe respiratory failure, ECMO provides time for the lungs to rest
and recover by augmenting gas exchange with the extracorporeal circuit.
A review of the outcomes in patients with Middle East Respiratory
Syndrome Coronavirus (MERS-CoV) treated with ECMO demonstrated a
decrease in hospital mortality rate and length of intensive care unit
(ICU) stay compared to those managed with conventional therapy alone
(1). Early reports regarding the use of ECMO in patients with Severe
Acute Respiratory Distress Syndrome Coronavirus 2 (SARS-COV-2 or
Covid-19) pneumonia have been mixed. Despite the similarities of
MERS-CoV and the current novel coronavirus disease, recent reports have
raised concerns regarding the high mortality rates observed in an early
series of ECMO supported Covid-19 patients (2, 3). Similarly, a pooled
analysis of five recent studies (4, 5, 6, 7, 8) suggested ECMO produced
neither harm nor benefit in Covid-19 patients with ARDS. The authors of
these analysis compared mortality in patients supported with ECMO for
both MERS and Covid-19 and concluded Covid-19 patients had a
significantly higher mortality than MERS (94.1% vs. 65.0%) when
treated with ECMO. The authors further state that this data raises
“questions about the real utility of ECMO in this outbreak” (8).
Initial reports from United States hospital systems that had been both
surprised and overrun with critically ill Covid-19 patients,
demonstrated unfavorable results with supporting patients with ECMO,
leading centers to abandon this support modality for these patients (9).
We present a single-center analysis and preliminary outcomes regarding
the use of ECMO in 15 patients with severe respiratory failure due to
Covid-19 all of which had failed maximal conventional ventilatory
management and interventions as presented. These initial promising
results prompted communication of our experience, despite its
preliminary nature.
Methods :
All patients placed on ECMO due to COVID-19 pneumonia from March
10th, 2020 to April 30th, 2020 were
identified. Data was manually extracted from the medical records of all
fifteen patients into the ECMO registry. All patients were admitted to
either the medical surgical intensive care unit (MSICU) or
cardiovascular intensive care unit (CVICU) between March
15th, 2020, and April 27th, 2020.
This study was approved by the Institutional review board.
Patients were managed by the ECMO team, which consisted of an
experienced ECMO physician, cardiac surgeon, ECMO nurse, ECMO specialist
and respiratory therapist. Prior to the Covid-19 pandemic, ECMO patients
had only been cared for in the CVICU. Do to overwhelming number and
severity of the respiratory failure, extension into the MSICU was
necessary. Placement and care of ECMO patients within the MSICU was a
new practice and required sharing of resources from the CVICU and
included CVICU ECMO nurses, physicians and ECMO specialists to care for
the ECMO patients. The CVICU nurse were additionally tasked with
training the MSICU nurses.
Patient Selection for Extracorporeal Support -
Extensive discussions with a multidisciplinary team composed of ECMO
physicians, cardiac surgeons, medical intensivists, and senior ECMO
providers led to more restrictive criteria than is usually utilized for
respiratory ECMO patient selection. The experiences in Asia, Europe and
early United States were considered while preparing for this global
pandemic.
Specific criteria for patients to be considered and accepted for VV ECMO
include (Figure 1):
A) Ventilated less than 10 days with no additional serious comorbidities
B) Patients less than 60 years of age
C) PaO2/FiO2 ratio < 100
and/or patients that were not adequately supported despite:
1. Lung protective ventilation:
(Tidal Volume (Vt) < 6ml/kg Ideal body weight (IBW), Plateau
Pressure (PPlat) < 30mmHg*)
2. Neuromuscular blockade (NMB)
3. Prone positioning
D) Hypercapnic acidosis compromising perfusion with failed above
interventions
The term “serious comorbidities” refers to the fact that patients with
chronic organ dysfunction due to co-morbidities outside of diabetes
mellitus (DM), hypertension (HTN), and hyperlipidemia (HLD) were
excluded. As indicated, an age less than 60 years was initially utilized
as the upper limit for ECMO candidacy. This age limit was further
reduced to patients <55 years as ECMO resources became
limited. If the P/F ratio was >100 and lung protective
ventilation was not providing adequate gas exchange (compatible with
perfusing vital organs), the patient was considered for ECMO. For the
purposes of defining the above criteria: Failure of adequate gas
exchange was defined as an oxygen saturation less than 85%,
PaO2 < 50mmHg, or an acidosis compromising
perfusion (pH < 7.2 with hypercarbia) for more than 3 hours.
Perfusion compromise was defined as a mean arterial pressure less than
65mmHg. Failure of lung protective ventilation is defined as the
requirement of a PPlat > 30mmHg and/or a Vt
> 6ml/kg IBW for more than 3 hours to achieve adequate gas
exchange. Pulmonary vasodilator therapy with inhaled epoprostenol or
inhaled nitric oxide were used as adjunctive measures in addition to
lung protective ventilation.
Covid-19 patients with concomitant hemodynamic instability due to a
reversible cause were evaluated for Veno-Arterial (VA)-ECMO on a case by
case basis. An example of a potentially reversible cause would be acute
right heart failure. When VA-ECMO is initiated, the family is informed
that 5-7 days of support will be provided. If there is no improvement
after this allotted time, goals of care and discontinuation of ECMO will
be discussed. The ECMO team decided that extracorporeal CPR (eCPR) will
not be offered for this patient population.
The decision to place patients on ECMO was made by a multidisciplinary
team approach that included an experienced ECMO physician, cardiac
surgeon, and intensivist. For patients that were borderline or at higher
risk, additional ECMO intensivists and cardiac surgeons were consulted.
In anticipation of limited resources, ECMO was deployed for patients
with the perceived highest chance of survival based on their age and
prior level of health.