Methods
Adult patients positive for COVID-19 who underwent ECMO at our institution from April 1, 2020 to June 11, 2020 were included in this study. Patients were identified by an IRB-approved, prospectively maintained ECMO database (IRB approval # 11D.185). The data from these patients was retrospectively extracted and details were further studied by reviewing medical records. Inclusion criteria included a positive COVID-19 test and a diagnosis of ARDS. ECMO placement was determined by a multidisciplinary team that included a cardiac surgeon, a pulmonary critical care physician, and a cardiovascular intensivist.
The indications for ECMO placement were the same as our previous paper,(18) and contraindications for ECMO placement in treating COVID-19 patients are listed in Table 1. The exclusion criteria may be more restricted than in non-COVID-19 patients, due to the limitations of resources during this pandemic.
The primary mode of ECMO in COVID-19 ARDS was veno-venous ECMO (VV-ECMO) using the femoral and internal jugular veins (Figure 1). All cannulation was performed in the ICU without transport to either the operating room or catheterization lab unless an issue occurred during bedside cannulation. Since Avalon dual lumen ECMO cannula placement always requires fluoroscopy and echocardiography, which requires additional personnel including radiology technicians and an echocardiography technician, the utilization of the Avalon cannula was discouraged.(18) Veno-arterial ECMO (VA-ECMO) should be reserved for only those who had severe but reversible cardiac dysfunction, such as COVID-19 related myocarditis. ECMO assisted cardiopulmonary resuscitation (ECPR) for patients with COVID-19 was discouraged due to its known poor outcomes.
Due to the COVID-19 pandemic, we no longer offer a mobile ECMO program outside of our institutional network due to the concern of exposure of required personnel including the ECMO surgeon, perfusionist, and transfer nurses at the local site. Instead of activating mobile ECMO cannulation teams, we encouraged local cardiac surgeons to place ECMO at their institutions and then transport the patient to our facility.
The general management of ECMO has been described in one of our prior papers.(19) Briefly, after placement of ECMO, the ventilator was set to the ARDSnet protocol. The typical setting was pressure controlled ventilation, rate 15, PEEP 15, delta P 15 until recovery of the respiratory function. Paralytics were discontinued within 24 hours of ECMO initiation, unless respiratory function was deetiolated. Sedatives were used if a RAS score was negative 1-2. Blood pressure was maintained at least mean arterial pressure of 60 mm Hg with vasopressors and/or fluid as appropriate. A heparin drip was started once PTT fell below 50 seconds after cannulation and maintained at an anti-Xa level of 0.3-0.5. If bleeding complications were observed, the anticoagulation was held and then restarted at a lower anti-Xa goal of 0.1-0.3.
Timing of the decannulation was determined by chest x-ray findings and lung mechanics. Before decannulation, the sweep gas was discontinued for at least 24 hours to ensure the lungs were able to exchange oxygen and carbon dioxide appropriately. For COVID-19 cases, we encourage bed-side decannulation rather than transporting to operating room to limit exposure to COVID-19.
The primary endpoints of this study were ECMO survival and hospital survival. ECMO survival was defined by withdrawal of care or death within 24 hours of decannulation. All patients who survived to hospital discharge were classified as “Survivors” and all patients who did not survive to hospital discharge were classified as “Non-Survivors.” The baseline characteristics, clinical characteristics, and outcomes were calculated and compared between the two groups.
Data was expressed as the number with percentage, mean +/- standard deviation, or median (quantile) as appropriate. Two groups were compared using chi-squared tests for categorical variables and standard t-tests for continuous variables as appropriate. Significance was accepted at a P-value less than 0.05.