Comparison of clinical outcomes in critically ill COVID-19 patients on mechanical ventilation with nosocomial pneumonia between Alpha and Omicron variants

Abstract

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease 2019 (COVID-19), a pandemic that has resulted in millions of deaths worldwide. Critically ill COVID-19 patients who require intubation and develop nosocomial pneumonia, commonly caused by gram-negative bacilli, have a higher mortality rate than those without nosocomial pneumonia.

Objectives: The aim of this study is to compare the clinical characteristics and outcomes and associated risk factors of Alpha and Omicron SARS-CoV-2 variants in critically ill patients on mechanical ventilation (MV) with nosocomial pneumonia.

Design: This is a retrospective single-center cohort study.

Methods: This observational study was conducted at Taipei Veterans General Hospital, Taiwan from May 2021 to September 2022. Critically ill patients who had confirmed SARS-CoV-2 infection and intubated on a MV with bacterial pneumonia were enrolled. Demographic data, laboratory results, and treatment information were collected and analyzed. In addition, clinical outcomes among different SARS-CoV-2 variants were examined.

Results: This study included 94 critically ill COVID-19 patients who required intubation and intensive care unit (ICU) admission. The Alpha group had a longer duration of SARS-CoV-2 viral shedding, MV days, and ICU stay, while the Omicron group had older age, more comorbidities, higher APACHE II scores, and higher in-hospital mortality (47.0% versus 25.0%, p = 0.047). However, independent risk factors for in-hospital mortality included malignancy, lower serum albumin levels, and lack of Remdesivir treatment, except for the SARS-CoV-2 variant.

Conclusion: Our study discovered a higher in-hospital mortality rate in severe COVID-19 patients with MV and secondary pneumonia infected with the Omicron variant compared to the Alpha variant; however, real independent risk factors for in-hospital mortality are malignancy, lower serum albumin level, and lack of Remdesivir treatment.

Keywords: coronavirus disease 2019; hospital-acquired pneumonia; severe acute respiratory syndrome coronavirus 2 variants; ventilator-associated pneumonia.

Figure 1.

Study flowchart. COVID-19, coronavirus disease 2019; CPAP, continuous positive airway pressure; MV, mechanical ventilator; OSA, obstructive sleep apnea.

Figure 2.

Distribution of bacterial cultures obtained from respiratory specimens, including sputum and endotracheal aspirate. There were 139 instances of positive culture in the Alpha group and 239 instances of positive culture in the Omicron group.

Figure 3.

The multivariate Cox proportional hazards models between each independent risk factor. (a) The cancer group has a significantly higher in-hospital mortality rate (p = 0.003). (b) Patients with lower serum level of albumin has higher in-hospital mortality (p = 0.030). (c) The administration of RDV has significantly lower in-hospital mortality (p = 0.005). RDV, Remdesivir; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.