A Retrospective Evaluation of the Effects of Cumulative Fluid Balance on Mortality and Morbidity in Critically Ill Patients in a Tertiary Intensive Care Unit (ICU) in Brisbane, Australia

Introduction The administration of fluid therapy and fluid management is common in the intensive care unit (ICU). There is an increasing trend toward an association between fluid balance and patient outcomes, including mortality. Despite extensive research, the best approach to fluid management remains uncertain. In this study, we tested the hypothesis that a more positive cumulative fluid balance (CFB) is associated with increased hospital mortality in ICU patients. Design and setting This is a single-center retrospective cohort study conducted at a tertiary ICU (PAH; Brisbane, Australia) from January 2015 to June 2021. Fourteen thousand three hundred thirty-nine admissions were screened, from which 2,392 individual patient admissions were analyzed. Main outcome measures Patients were grouped into quintiles based on 120 hours of CFB. This time frame was defined a priori. Actual mortality (Intensive Care Unit and Hospital) was compared to predicted mortality (Acute Physiology and Chronic Health Evaluation (APACHE III) and Australian and New Zealand Risk of Death (ANZROD)). Results Hospital mortality increased progressively from 13.5% in the least fluid positive group to 38.8% in the most fluid positive group. When adjusted for disease severity scores, the actual mortality when compared to predicted outcomes was lowest in the less fluid positive quintiles and increased progressively to become greater than predicted in the most fluid positive quintile. The more fluid positive patients had higher APACHE III scores, were more likely to require higher doses of vasopressors, had more severe kidney injury, more requirement for dialysis and invasive mechanical ventilation, were more likely to be postoperative, and had a trauma diagnosis. The less fluid positive patients required lower doses of vasopressors, less invasive mandatory ventilation, and had longer ICU and hospital stays, and more furosemide use, with the diagnosis of sepsis over-represented in this group. Conclusions A higher CFB at 120 hours of ICU admission was associated with increased hospital mortality, even after adjustment for illness severity. These findings support the need for prospective studies to define optimal fluid strategies in critically ill patients.