Acute Kidney Injury Among Patients Undergoing Orthopedic Surgery and Admitted to the ICU: A Retrospective Analysis of Nonoperative Risk Factors

BACKGROUND Acute kidney injury (AKI) is a critical complication following orthopedic surgery, yet patient-specific and perioperative non-surgical risk factors remain insufficiently characterized. We hypothesized that AKI is primarily influenced by pre-existing conditions interacting with perioperative stressors. This study aimed to evaluate AKI incidence and identify its clinical and laboratory predictors in post-orthopedic ICU patients. MATERIAL AND METHODS We conducted a retrospective cohort study using the Medical Information Mart for Intensive Care IV database (2008-2019), including 1791 orthopedic patients admitted to the ICU of a tertiary hospital in the United States. Multivariable logistic regression, Kaplan-Meier analysis, and ROC curves were used to assess risk factors and predictive performance. RESULTS AKI incidence was 71.0%. Kaplan-Meier analysis showed significantly worse survival in AKI patients compared with non-AKI patients. The AKI group had higher illness severity scores and longer ICU and hospital stays. Multivariate analysis identified 7 independent risk factors: weight (OR=1.03), ICU stay (OR=1.42), OASIS (OR=1.05), SOFA (OR=1.13), SAPS II (OR=1.03), and age (OR=1.02). ROC analysis showed SOFA score (AUC=0.764) and ICU stay (AUC=0.764) had the highest predictive value, followed by OASIS (AUC=0.707), SAPS II (AUC=0.709), and weight (AUC=0.635). Optimal thresholds were 3.5 points for SOFA (sensitivity=0.670, specificity=0.726) and 2.77 days for ICU stay (sensitivity=0.540, specificity=0.838). CONCLUSIONS AKI is common in postoperative orthopedic surgery ICU patients and associated with worse outcomes. Key predictors include illness severity, ICU stay length, and patient-specific factors. Early risk stratification may improve postoperative care and patient outcomes.