Predictors of In-Hospital Mortality Among Hospitalized Colistin-Treated Patients at a Tertiary Urology–Nephrology Referral Center

Background/Objectives: Colistin is a last-resort agent against multidrug-resistant Gram-negative infections and is administered predominantly to complex, comorbid inpatients in whom mortality is high. We aimed to identify independent baseline predictors of in-hospital mortality in colistin-treated patients and to characterize temporal changes in mortality over 15 years. Methods: We conducted a retrospective cohort study of 1225 consecutive patients receiving systemic colistin between November 2009 and November 2024 at Parhon Hospital, a tertiary urology–nephrology center in Iași, Romania; independent predictors of death were identified using multivariable logistic regression restricted to variables fixed at the time of colistin initiation, reported as adjusted odds ratios (aOR) with 95% confidence intervals (CI). Results: Patients were predominantly male (60.2%), with a mean age of 65.1 ± 14.4 years; 85.6% were admitted to urology or nephrology. In-hospital mortality was 27.6%. Mortality was independently associated with acute kidney injury (aOR 3.72, 95% CI 2.76–5.01), sepsis (aOR 2.79, 95% CI 2.11–3.70), emergency admission (aOR 1.91, 95% CI 1.40–2.61), Charlson comorbidity index (aOR 1.13 per point, 95% CI 1.05–1.22), and older age (aOR 1.03 per year, 95% CI 1.02–1.04); sex was not associated. Crude mortality increased across the study period (odds ratio 1.16 per year, 95% CI 1.13–1.20) and remained elevated after adjustment for case-mix (adjusted odds ratio 1.13 per year, 95% CI 1.09–1.17). Conclusions: Acute kidney injury, sepsis, emergency admission, comorbidity burden, and age were independently associated with in-hospital death. Mortality rose progressively over 15 years, only partly explained by an increasingly severe case-mix, supporting early risk stratification of colistin recipients.