Predictive Analysis of the Mortality Rate of Patients with Heart Failure Complicated by Acute Kidney Failure Based on the Fluid Balance: A Retrospective Study Using the MIMIC-IV Database

Background. Heart failure (HF) is a global health issue, and its complication with acute kidney failure (AKF) increases the risk of mortality. This study aimed to investigate the predictive value of fluid balance for mortality in patients with HF complicated by AKF. A retrospective analysis was performed using the MIMIC-IV database to evaluate the relationship between fluid balance and mortality in patients with HF complicated by AKF.Material and methods. Adult patients with HF and AKF and who were listed in the MIMIC-IV database between 2008 and 2019 were included. The patients were divided into survival and non-survival groups. The primary outcome measure was fluid intake and output in the first three days in the intensive care unit (ICU). The main outcome being in-ICU mortality and the secondary outcome being 28‑day mortality after ICU admission. A multivariable Cox proportional hazards model was used to assess the relationship between fluid balance and the risk of death, after adjusting for potential confounding factors.Results. A total of 1433 eligible patients were included. The study found that compared to the death group, patients in the survival group maintained lower positive balance on day 1 (453.51 ml vs 1813.66 ml), negative balance on day 2 (-246.75 ml vs 646.00 ml), and negative balance on day 3 (-350.21 ml vs 312.92 ml). Additionally, fluid balance on the first day predicted ICU mortality rate (AUC 0.658, p<0.01), on the second day it predicted ICU mortality rate (AUC 0.654, p<0.01), and on the third day it also predicted ICU mortality rate (AUC 0.634, p<0.01).Conclusion. Positive fluid balance in patients with HF and AKF is independently associated with higher in-hospital mortality. Monitoring and managing fluid balance may provide clinicians with an important tool to improve patient outcomes.