A Single Center Experience with Early Initiation of ECMO Prior to Mechanical Ventilation in COVID-19 Patients with Severe ARDS

ABSTRACT

Background: Coronavirus disease 2019 (COVID-19) is an ongoing global pandemic that results in a viral pneumonia caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Prognosis is poor among those that develop acute respiratory distress syndrome and progress to mechanical ventilation. Due to the high mortality associated with mechanical ventilation and the unique physiology associated with COVID-19, we compared outcomes in COVID-19 patients placed on ECMO prior to initiation of mechanical ventilation (early group) to patients treated with ECMO after mechanical ventilation (conventional group). Methods: This is a single center retrospective analysis of COVID-19 patients placed on veno-venous (VV) ECMO between 04/06/2020 and 01/15/2021 in a tertiary high-volume ECMO center. Patients between 18 - 70 years of age with a diagnosis of SARS-CoV-2 and diagnosed with ARDS. Patients were considered for ECMO if they had a P/F ratio of less than 50 mmHg for at least three hours, a P/F ratio of less than 80 mmHg for at least 6 hours or an arterial blood pH of less than 7.25 with a pCO2 greater than or equal to 60 mmHg for at least six hours despite optimized ventilator settings (RR> 35 breaths/minute, plateau pressure ≤ 32, tidal volume of 6ml/kg of predicted body weight, FiO2 ≥ 80% and PEEP ≥ 10 cm water). A subset of patients with a rapid deterioration (rapid escalation of O2 requirements, tachypnea RR > 30, tachycardia HR >100) or with clinical signs consistent with poor tolerance to positive pressure ventilation such as a pneumothorax or pneumomediastinum were considered for ECMO prior to mechanical ventilation if they had a P/F <80 despite selfproning with either HFNC 40L/100% in addition to a nonrebreather mask with 15L/100% or non-invasive positive pressure ventilation (NIPPV) with an FiO2 100%. The primary outcome was survival to discharge assessed as a binary outcome of survived or non-survived. Secondary outcomes evaluated included discharge location, length of stay, and incidence of adverse events such as bleeding events, infection, CVA, and pneumothorax requiring chest tube placement. Results: A total of 100 patients were reviewed, including 24 early ECMO patients and 76 conventional ECMO patients. The mean age of the cohort was 48.9 + 11.5 years, 28% were female, and 74% were Hispanic. At baseline, the mean BMI was 31.6 + 5.8, 55% had a history of hypertension, 36% were diabetic and 9% had a history of asthma. Overall, 57% of patients survived to discharge with a median of 23.3 (7.8-40.6) days on ECMO. There were no significant differences in age, gender, BMI, comorbidities, or APACHE scores between the two groups. Prior to ECMO, the early group had lower P/F ratios (52.7 + 11.5 vs. 71.1 + 20.7, p <0.0001), higher pH (7.4 + 0.0 vs. 7.3 + 0.1, p <0.0001), and lower CO2 (36.1 + 6.8 vs 50.9 + 19.1, p <0.0001) than the conventional cohort. Though not significant, there was a trend towards survival in the early ECMO group compared to the conventional group (71% survival vs. 53%, p= .12). Of the early cohort, 15 patients required intubation at some point after cannulation for a median time of 2.5 days (0- 27.0 days). Of the nine patients never intubated, two patients expired, two received a lung transplant, three were discharged home, one discharged to rehab and one to an LTAC facility. There was no difference in adverse events between the two groups. Conclusions: Certain patients with severe ARDS due to COVID-19 may benefit from VV-ECMO cannulation prior to mechanical ventilation with similar outcomes and a trend towards improved mortality.