Time-related association between fluid balance and mortality in sepsis patients: interaction between fluid balance and haemodynamics

This study aimed to investigate the time-related association between cumulative fluid balance (FB) and mortality. Data were extracted from the Medical Information Mart for Intensive Care (MIMIC) III. FB data on 8584 patients at the first (FB-fir24hr) and second (FB-sec24hr) 24 hours after intensive care unit admission were analysed. Compared to the combination of FB-fir24hr ≤ 0 and FB-sec24 hr ≤ 0, the combination of FB-fir24hr > 0 and FB-sec24hr ≤ 0 had significantly higher FB, with an insignificant odds ratio (OR) for mortality. However, the mortality ORs of two other combinations (FB-fir24hr ≤ 0 and FB-sec24hr > 0; FB-fir24hr > 0 and FB-sec24hr > 0) were significantly high. Furthermore, multivariable logistic analysis showed a significant stepwise increase ORs for mortality with increasing FB-sec24hr quartiles, with no significant increase in FB-fir24hr quartiles aside from quartile 4. In patients with negative FB, a stepwise decrease in mortality ORs with increasing FB-sec24hr quartiles was found with no significant difference in FB-fir24hr quartiles. In conclusion, the positive FB during the second but not the first 24 hours was associated with increased mortality in sepsis. Achieving more negative FB was associated with decreased mortality only in the second 24 hours.