COVID-19 status and intensive care unit burden and mortality: a single-center retrospective cohort study comparing...

Coronavirus disease 2019 (COVID-19) placed substantial pressure on intensive care units (ICUs), but long-period comparisons with non-COVID-19 ICU patients remain useful for distinguishing disease-associated patterns from the general burden of critical illness. We addressed the gap in single-center data linking COVID-19 status with mortality, healthcare-associated infections, admission physiology, and Therapeutic Intervention Scoring System-28 (TISS-28) workload in a mixed tertiary ICU.

This single-center retrospective cohort study included first admissions to the adult ICU of the University Clinical Hospital in Białystok, Poland, between January 1, 2017, and June 1, 2023. Patients were classified as COVID-19-positive (n = 355) or COVID-19-negative (n = 2971) according to reverse transcription-polymerase chain reaction testing. Baseline characteristics, comorbidities, healthcare-associated infections, admission laboratory and arterial blood gas variables, and TISS-28 variables were compared using Welch t-tests, chi-square tests, or Fisher exact tests, as appropriate. Effect sizes are reported with 95% confidence intervals. Logistic regression estimated the association between COVID-19 status and in-hospital mortality in unadjusted, baseline-adjusted, and exploratory complete-case models.

In-hospital mortality was higher in COVID-19-positive patients than in COVID-19-negative patients (227/355 [63.9%] vs. 1320/2971 [44.4%]; odds ratio [OR] 2.22, 95% CI 1.77 to 2.79). This association remained after baseline adjustment (adjusted OR 2.03, 95% CI 1.60 to 2.58) and in the exploratory complete-case model including admission physiology and laboratory markers (adjusted OR 2.73, 95% CI 1.60 to 4.64). Among non-survivors, time to death was shorter in the COVID-19-positive group (10.7 [SD 7.4] vs. 14.3 [SD 20.0] days; mean difference - 3.63 days, 95% CI -5.07 to -2.18). Bacterial bloodstream infection was more frequent in COVID-19-positive patients (22.8% vs. 9.9%; OR 2.70, 95% CI 2.05 to 3.56). At admission, COVID-19-positive patients had lower C-reactive protein, procalcitonin, PaO2, creatinine, and lactate, but higher PaCO2, glucose, sodium, potassium, bicarbonate, and hemoglobin values. TISS-28 profiles differed by COVID-19 status, most notably for respiratory physiotherapy recorded at least once (97.5% vs. 62.0%; OR 23.63, 95% CI 11.76 to 47.52) and longer duration of respiratory physiotherapy (mean difference 4.89 days, 95% CI 3.57 to 6.22).

In this retrospective cohort, COVID-19-positive status was associated with higher in-hospital mortality, shorter time to death among non-survivors, more frequent bacterial bloodstream infection, and a distinct ICU workload profile. These findings should be interpreted as associations rather than causal effects because of the single-center design, long heterogeneous study period, incomplete severity-score data, and lack of shift-level staffing and high-dependency-unit data.