Hemoglobin variability predicts mortality in acute kidney injury patients undergoing continuous renal replacement therapy: a multi-database cohort study

Short-term hemoglobin variability (Hb-ARV) during continuous renal replacement therapy (CRRT) may reflect blood volume instability in acute kidney injury (AKI), yet its mortality implications remain unclear. This multi-database study analyzed adult AKI patients receiving CRRT &gt;24 h from the Medical Information Mart for Intensive Care (MIMIC)-IV, eICU Collaborative Research Database (eICU), Amsterdam University Medical Center (AmsterdamUMC) database, and Jiangsu Province Hospital (JSPH) CRRT database. Hb-ARV, quantifying hemoglobin fluctuations during CRRT, was assessed <i>via</i> Cox regression and restricted cubic splines for associations with in-hospital and 1-year mortality. The MIMIC-IV, eICU, AmsterdamUMC, and JSPH cohorts included 1,321, 437, 631, and 488 patients, respectively, with median (IQR) Hb-ARVs of 5.1 (3.9–6.6) g/L, 5.8 (4.1–8.2) g/L, 5.0 (3.9–6.8) g/L, and 6.3 (5.1–8.0) g/L. In-hospital mortality rates were 48.2%, 41.2%, 43.7%, and 44.9%. Restricted cubic splines revealed J-shaped/linear mortality trends with Hb-ARV. Compared to the second quartile of Hb-ARV, the highest quartile was significantly associated with increased in-hospital mortality in MIMIC-IV (adjusted HR 1.32, 95% CI: 1.05–1.66), AmsterdamUMC (adjusted HR 1.74, 95% CI: 1.23–2.46), and JSPH (adjusted HR 1.96, 95% CI: 1.31–2.93) cohorts. In the eICU cohort, where a linear trend was observed, each 1 g/L increase in Hb-ARV was associated with an adjusted HR of 1.07 (95% CI: 1.03–1.11) for in-hospital mortality. Highest quartile of Hb-ARV was also associated with increased 1-year mortality in MIMIC-IV and AmsterdamUMC cohorts. Excessive Hb-ARV during CRRT predict higher short- and long-term mortality in patients with AKI.