Prognostic Value of the Diuretic Response to Low-Dose Furosemide for Predicting Progression from Acute Kidney Injury Stage 1 in Critically Ill Patients: A Retrospective Cohort Study

Purpose The furosemide stress test is useful for predicting acute kidney injury (AKI) progression, but its widespread use is limited by concerns regarding adverse events associated with high-dose administration (1-1.5 mg/kg). Furosemide responsiveness (FR) to lower doses seems to have high predictive value while reducing such risks, but its utility in early-stage AKI (stage 1) is unclear. We thus investigated the predictive value of FR in early-stage AKI. Methods We retrospectively reviewed adult intensive-care unit patients (≥18 years old) admitted between January 2021 and June 2024 who received a furosemide bolus dose during stage 1 of AKI. FR was assessed using the FR index (FRI; 2-h urine output per furosemide dose), body weight-adjusted FRI (mFRI), and body weight-adjusted 2-h urine output (UO/BW). The indices were compared by the Mann–Whitney U test between progression (stage ≥2 within 7 days) and non-progression groups, and predictive ability was assessed by a receiver operating characteristic (ROC) analysis. Results Among 50 patients, 12 progressed and 38 did not. The mean furosemide dose was 0.29 mg/kg. FRI, mFRI, and UO/BW were significantly lower in the progression group ( P < .001), with respective areas under the ROC curve of 0.945 (95% confidence interval, 0.887-1.000), 0.921 (0.831-1.000), and 0.919 (0.842-0.996). No hypotension requiring a rescue fluid bolus or other clinically overt hemodynamic instability was observed. Conclusion FR to lower doses was associated with subsequent progression from AKI stage 1 without evident hemodynamic instability in this cohort. These findings suggest that FR may provide a potentially safe and clinically useful indicator for early risk stratification in critically ill patients.