On COVID-19 and the critically ill patient

Abstract

This thesis investigates COVID-19 related critical illness across pandemic phases, focusing on cardiac injury, intensive care unit-acquired infections, and predictors of severe outcomes. We conducted four studies using retrospective, prospective, and registry-based designs. The first study evaluated whether chloroquine phosphate treatment was associated with cardiac injury, finding no significant differences in cardiac biomarkers between treated and untreated patients. The second study assessed cardiac function in critically ill patients with COVID-19 and demonstrated that right ventricular dysfunction and elevated pulmonary artery pressure were independently associated with increased mortality. The third study compared intensive care unit-acquired infections in patients with COVID-19 and influenza, showing higher rates of ventilator-associated lower respiratory tract and bloodstream infections in COVID-19, with corticosteroid therapy and male sex as risk factors. The fourth study analyzed temporal trends, revealing advanced age as the strongest predictor of adverse outcomes in COVID-19 and influenza, while incomplete vaccination and male sex also increased risk of severe COVID-19. Hospitalization rates remained higher for COVID-19 than for influenza, but clinical and demographic profiles converged during the Omicron period, reflecting reduced severity and fewer intensive care admissions. These findings underscore the dynamic nature of COVID-19, the prognostic significance of right ventricular dysfunction, the need for infection control and tailored therapies, and the protective role of vaccination, particularly in the elderly. They highlight how evolving immunity, viral adaptation, and public health measures have shaped disease severity, informing preparedness for future viral pandemics.