Prognostic Impact of AKI in the Respiratory Intensive Care Unit and the Diagnostic Utility of the Integrated Osmotic Response Index (IORI) for Early-Stage AKI and Prerenal AKI

Objectives: Acute kidney injury (AKI) is a frequent complication in critically ill patients in the respiratory intensive care unit (RICU), significantly impacting prognosis. Early recognition of prerenal and early-stage AKI is vital for improving outcomes. This study aimed to evaluate the prognostic significance of AKI according to the KDIGO classification and assess the diagnostic utility of the Integrated Osmotic Response Index (IORI) in identifying early-stage and prerenal AKI. Methods: A retrospective cohort of 437 adult patients admitted to the RICU with respiratory failure was analyzed. Demographics, laboratory parameters, and clinical outcomes were recorded. AKI was defined and staged per KDIGO 2012 criteria. Prerenal AKI was identified using the BUN/creatinine ratio. IORI values were calculated and analyzed in relation to AKI stages and outcomes. ROC curves and DeLong tests were employed to compare IORI with serum creatinine. Results: AKI developed in 103 patients (23.6%): 91 had stage 1, 9 stage 2, and 3 stage 3 AKI. IORI values were significantly lower in patients with AKI, particularly in early stages (p < 0.001). Prerenal AKI patients had lower IORI than non-prerenal AKI (p = 0.007). The optimal IORI cut-off for AKI was 40.34 (sensitivity 62.1%, specificity 70.1%); for prerenal AKI, it was 43.30. No significant survival difference was found between patients without AKI and those with stage 1 AKI, but ad-vanced-stage AKI was associated with reduced survival. Conclusion: IORI appears to be a prom-ising marker for detecting early-stage and prerenal AKI in respiratory failure. Further prospective studies are needed to validate its diagnostic and prognostic value.