Impact of an Elevated Fluid Accumulation Index in Septic Patients With HFrEF: A MIMIC-IV Analysis

Introduction: Guidelines support fluid resuscitation (30ml/kg over 3 hours) in all patients presenting with sepsis. Despite this, clinicians are hesitant to comply with aggressive fluid resuscitation in patients with heart failure with reduced ejection fraction (HFrEF). Significant practice variation also occurs in fluid management during the later phases of sepsis. The Fluid Accumulation Index [FAI=(fluid intake–fluid output)/fluid intake] quantifies a patient’s ability to excrete fluids under varying fluid loads. FAI values >0.42 are associated with poor outcomes in an older dataset (Medical information Mart for Intensive Care, MIMIC III, 2001-2012). This retrospective cohort study evaluated the influence of the FAI on clinical outcomes during sepsis management in those with HFrEF using more contemporary data.


Methods: Data was extracted from MIMIC IV (2008-2019) using SQL/BigQuery. Subjects with a prior history of HFrEF who presented with sepsis, severe sepsis, or septic shock (requiring an ICU stay >48 hours) were included. The FAI for the first 48 hours of sepsis management was calculated and split into two study groups based on FAI (>0.42 vs <=0.42). The primary outcome was in-hospital mortality. Secondary outcomes included ICU length of stay, development of acute kidney injury (AKI), and the need for dialysis support. Standard univariate statistics compared the nominal outcomes between the groups.


Results: Among the 206 patients included, 163 (79%) had an elevated FAI >0.42 and 43 (21%) had a FAI of <=0.42. Of those with an elevated FAI, 42.9% experienced in-hospital mortality compared to 9.3% in the low-FAI group (p < 0.001). The elevated FAI group also experienced a longer ICU length of stay (7.6 vs 4.9 days, p< 0.001), a similar incidence of AKI (58% vs 70%, p=0.232), but when AKI occurred the elevated FAI group required dialysis more frequently (20% vs 0%, p< 0.001).


Conclusions: In the MIMIC IV dataset, a FAI >0.42 remains significantly associated with higher in-hospital mortality, longer ICU length of stay, and higher likelihood of requiring dialysis among those with a history of HFrEF who presented with sepsis. Further clinical trials evaluating individualized fluid resuscitation and de-escalation strategies guided by the FAI are warranted.