Long-term survival comparison between the first and second waves among 265 critical COVID-19 patients admitted to the ICU: A retrospective cohort study.

Backgroud: Management of severe COVID-19 patients admitted to ICU considerably evolved during the first months of the pandemic. It is unclear, however, whether these changes improved long-term survival of these critically ill patients.

Methods: We conducted a retrospective cohort study in adults with COVID-19 pneumonia admitted to a French ICU between February 2020 and January 2021, a timeframe that covered the first two waves of the pandemic. Primary outcome was to compare long-term survival between the first and second waves. Survival predictor were identified using a Cox proportional-hazards model.

Results: We included 265 patients in the cohort: 140 (52.8 %) and 125 (47.2 %) belonging to the first and second waves, respectively. Baseline characteristics of the patients were similar between the two waves. During W2, use of early corticotherapy increased (86.4% vs. 17.8 %; p <0.001), as well as high-flow oxygen therapy use (68.5% vs. 37.4 %; p<0.001). Need for invasive mechanical ventilation decreased (49.6% vs. 72.9 %; p <0.001) and ICU length of stay was shorter (11 [6-22] vs 19 [8-32]days; p = 0.008). ICU mortality was 32.8 % without significant difference between waves. Survival analysis revealed that 3 variables were independently associated with a worse long-term prognosis: a higher SAPS II score (1.05 [1.04-1.06]; p<0.001), a higher age (1.05 [1.01-1.08]; p = 0.005) and admission during W2 (2.22 [1.15-4.28]; p = 0.017).

Discussion: Despite substantial changes on management of severe COVID-19 patients, we observed a decreased long-term survival among patients admitted during the second wave. We also noted a shorter ICU length of stay.