Methods and Materials:
A retrospective cohort review was performed on all entries in the
Extracorporeal Life Support Organization (ELSO) registry from November
1, 2010 to July 31, 2017 at the Massachusetts General Hospital (MGH),
Boston, Massachusetts (USA). Patients who were undergoing CPR in
hospital at the time of ECMO initiation as documented in the procedural
report were included. Patients who underwent ECMO cannulation but for
whom immediate durable flow through the ECMO circuit could not be
initiated were excluded. Baseline characteristics were extracted from
the medical record. The study was approved by the Partners Institutional
Review Board.
This study’s primary outcome was survival to hospital discharge.
Etiology of cardiac arrest was adjudicated by two reviewers (NM & LXM)
and categorized by cardiac origin (defined as an etiology of acute
coronary syndrome, primary arrhythmia in the absence of overlapping
etiology, acute heart failure, and tamponade) or non-cardiac origin
(defined as pulmonary embolism, drug toxicity, sepsis, perioperative
shock, or air embolism). When multiple potential etiologies were
present, the primary cause as adjudicated by the care team was selected.
Cardiac arrest rhythm was ascertained from the procedural report and
categorized as either pulseless ventricular tachycardia/ventricular
fibrillation (VT/VF) or pulseless electrical activity (PEA). CCPR time,
defined as duration of chest compressions immediately prior to ECMO
initiation, was reported when available.
At our institution, absolute contraindications to ECMO support include
acute intracranial hemorrhage or massive stroke, contraindication to
anticoagulation or refusal to receive blood products, active bleeding,
and severe aortic insufficiency. Relative contraindications included age
greater than 70 years, active cancer, suicide attempt, chronic
hemodialysis, lack of social support or healthcare proxy, CCPR greater
than 45 minutes, aortic dissection, end stage liver disease, and
body-mass index greater than 45 kg/m2.
ECMO-related complications were assessed. Major bleeding was defined as
Bleeding Academic Research Consortium category 3-527.
Additional outcomes assessed included de novo renal replacement therapy,
cerebrovascular events, limb ischemia, and cerebral performance category
(CPC). CPC scores 1 through 5 correlated to good cerebral performance
(able to work, minor deficits), moderate cerebral disability (persistent
deficits but mostly independent), severe cerebral disability (dependent
on others), coma or vegetative state, and brain death, respectively28.
Descriptive statistics were used to quantify baseline patient
characteristics, clinical features, ECMO utilization, and survival
rates. Categorical variables were reported as counts and percentages and
compared using the Fisher’s exact test. Continuous variables were
reported as medians with interquartile range (IQR) and compared with the
Wilcoxon two-sample test. Statistical significance was assessed at a
nominal α level of 0.05. All reported P values were 2-sided. Analysis
was performed in R 4.0.0 (R Core Team, 2020).