Trends in ICU Mortality From Coronavirus Disease 2019: A Tale of Three Surges

Abstract

Objectives: To determine the association between time period of hospitalization and hospital mortality among critically ill adults with coronavirus disease 2019.

Design: Observational cohort study from March 6, 2020, to January 31, 2021.

Setting: ICUs at four hospitals within an academic health center network in Atlanta, GA.

Patients: Adults greater than or equal to 18 years with coronavirus disease 2019 admitted to an ICU during the study period (i.e., Surge 1: March to April, Lull 1: May to June, Surge 2: July to August, Lull 2: September to November, Surge 3: December to January).

Measurements and main results: Among 1,686 patients with coronavirus disease 2019 admitted to an ICU during the study period, all-cause hospital mortality was 29.7%. Mortality differed significantly over time: 28.7% in Surge 1, 21.3% in Lull 1, 25.2% in Surge 2, 30.2% in Lull 2, 34.7% in Surge 3 (p = 0.007). Mortality was significantly associated with 1) preexisting risk factors (older age, race, ethnicity, lower body mass index, higher Elixhauser Comorbidity Index, admission from a nursing home); 2) clinical status at ICU admission (higher Sequential Organ Failure Assessment score, higher d-dimer, higher C-reactive protein); and 3) ICU interventions (receipt of mechanical ventilation, vasopressors, renal replacement therapy, inhaled vasodilators). After adjusting for baseline and clinical variables, there was a significantly increased risk of mortality associated with admission during Lull 2 (relative risk, 1.37 [95% CI = 1.03-1.81]) and Surge 3 (relative risk, 1.35 [95% CI = 1.04-1.77]) as compared to Surge 1.

Conclusions: Despite increased experience and evidence-based treatments, the risk of death for patients admitted to the ICU with coronavirus disease 2019 was highest during the fall and winter of 2020. Reasons for this increased mortality are not clear.

Figure 1.

Distribution of age (A), baseline comorbidities (B), and ICU interventions (C) over the study time periods (i.e., surges and lulls) for all patients admitted to the ICU with coronavirus disease 2019 (n = 1,686). CAD = coronary artery disease, CHF = congestive heart failure, CKD = chronic kidney disease, COPD = chronic obstructive pulmonary disease, CRRT = continuous renal replacement therapy, DM = diabetes mellitus, ECMO = extracorporeal membrane oxygenation, ESRD = end-stage renal disease, HD = hemodialysis, HTN = hypertension, Vent = ventilator.

Figure 2.

All-cause, in-hospital mortality over time for patients admitted to the ICU with coronavirus disease 2019 (n = 1,686). A, Crude daily in-hospital mortality (black solid line) with 70% and 90% CIs in gray and daily ICU census (red dashed line) over the study time periods. B, Relative risk of death across study time periods in unadjusted, baseline, and complete models. The baseline model is adjusted for age, race, ethnicity, Elixhauser Comorbidity Index, and admission from a nursing home. The complete model is adjusted for all variables in the baseline model in addition to d-dimer, C-reactive protein, Sequential Organ Failure Assessment score, mechanical ventilation, vasopressors, remdesivir, steroids, renal replacement therapy, bacteremia, bacterial pneumonia, and ICU length of stay.