Abstract The role of eosinophils (eos) in COVID is not well studied, although eosinopenia has been widely described. Recovery of eosinophil counts has been associated with clinical improvement in COVID. Anecdotally, we have observed hypereosinophilia in patients after veno-venous (V-V) extracorporeal membrane oxygenation (ECMO) cannulation for acute respiratory distress syndrome (ARDS) secondary to COVID. ECMO has been associated with lymphopenia, raising the question of whether it also influences eosinophil dynamics. These observations led us to systematically investigate eosinophilia and its clinical significance in patients on V-V ECMO at our institution.We retrospectively reviewed 281 patients placed on V-V ECMO from 1/1/2016 to 7/30/2025. Of these, 88 (31%) had eosinophil counts 1000/µL and 69 (24.5%) 1500/µL; hypereosinophilia (absolute eos 1500) was recognized by a clinician in 79.7% (55/69) of cases. Hypereosinophilia (1500) was significantly (p 0.001) higher in patients with COVID-19 (39.3%, 37/94) compared to patients without COVID (17.1%, 32/187). Demographics, laboratory data, ECMO duration, eosinophilic workup (infectious, medication exposure, etc) and treatment (steroid tx, etc), organ dysfunction, and outcomes were collected for patients with Eos 1500.The clinician recognized cohort with hypereosinophilia (n = 55) had a mean age of 45.5±11 years and was predominantly male (80%). COVID was the etiology of respiratory failure in 67% of cases. The median (IQR) time from cannulation to first hypereosinophilia was 18±13 days. Peak eosinophil count averaged 4.7±7.4 ×10³/µL, lasting a mean (SD) of 13.9±12.5days. Corticosteroids were administered in 80% of patients (although not all due to hypereosinophilia). Medication exposures associated with hypereosinophilia included antibiotics (beta lactams, sulfonamides, glycopeptides) (100%), proton pump inhibitors (91%), and diuretics (92%). Positive hypereosinophilia workup included Aspergillus (33%), Cytomegalovirus (25%), Strongyloidiasis (9%), and Anti-Nuclear Antibody (11%). Organ dysfunction was common: abnormal liver enzymes (66%), elevated pancreatic enzymes (35%), elevated troponin (54%), and impaired renal function (GFR 60 in 29%, creatinine 1.5 in 45%, CRRT in 34.5%). BAL eosinophilia 10% occurred in 22% of patients. Overall, 45% (25/55) of patients with hypereosinophilia survived hospital discharge. In this single-center study, hypereosinophilia is relatively common in patients on V-V ECMO, particularly in COVID, and may correlate with prolonged ECMO support and worse outcomes. These findings highlight a potential interaction between ECMO, eosinophil dynamics, and COVID. Further studies are needed to clarify the mechanisms and prognostic implications of eosinophilia in this population. This abstract is funded by: None
Tavakoli et al. (Fri,) studied this question.