Kidney failure trajectories and sub phenotypes in severe burn patients

Acute kidney injury (AKI) is a common and severe complication in burn patients, significantly increasing morbidity and mortality. Recent classifications distinguish acute kidney disease (AKD) as persistent kidney dysfunction beyond seven days; however, its trajectory in burn patients remains poorly understood. This study aimed to identify renal injury phenotypes in critically ill burn patients and assess their associations with clinical outcomes.

We conducted a single-center retrospective cohort study from 2013 to 2023 of adult (>18 years) ICU burn patients with total burn surface area >15%. Renal injury was classified using KDIGO serum creatinine criteria and renal replacement therapy needs. AKI was defined as occurring within 7 days of injury, secondary AKI as occurring beyond day 7 but lasting <7 days, and AKD as dysfunction persisting >7 days. Phenotype classification was supported by stepwise logistic regression, XGBoost, and random forest analyses.

Among 733 patients, 158 (21.6%) developed primary AKI, and overall mortality in this group was 95/158 (60.1%). Of the 121 primary AKI survivors, 58 (45.7%) developed further renal injury: secondary AKI alone (16.5%), AKD alone (10.7%), or both (20.7%). Secondary AKI and AKD were associated with mortality rates of 39% and 41%, and were independently linked to increased mortality. Primary AKI was mainly driven by baseline patient vulnerability (dementia, smoke inhalation, chronic alcohol use, age) and burn severity (TBSA full thickness, SAPS II), with dementia, hydroxocobalamin treatment, and smoke inhalation showing the strongest associations. In contrast, secondary AKI and AKD were characterized by complications occurring during ICU stay, particularly infection, cardiovascular support, digestive bleeding, and organ failures, with infection emerging as the dominant predictor across both phenotypes.

Primary AKI represents the most severe renal complication post-burn, while secondary injuries reflect later complications such as infection, hemorrhagic complications, or ARDS.