Association of serum phosphate with the severity and the short-term mortality of acute kidney injury in critically ill patients: a retrospective cohort study

Abstract

Abstract Background: This retrospective cohort study aims to investigate the correlation between serum phosphate levels and the severity of acute kidney injury (AKI) and to assess the impact of serum phosphate levels on short-term mortality in AKI patients. Methods: Utilizing data from the Medical Information Mart for Intensive Care (MIMIC)-IV database, we conducted a comprehensive analysis on patients diagnosed with AKI. Multifactorial logistic regression and Cox proportional hazard models were employed to assess the association between serum phosphate levels, AKI severity, and short-term mortality. Subgroup analyses were performed to ascertain the consistency of this association across different subgroups. Multiple imputation was used to address missing data, and a sensitivity analysis was conducted to ensure the robustness of the results. Results: The study included a total of 15,071 AKI patients. Following adjustments for potential confounders, multifactorial logistic regression demonstrated a significant correlation between the highest quartiles of serum phosphate levels and greater AKI severity (OR, 2.16, 95% CI, 1.90 to 2.46). Additionally, multifactorial Cox regression analysis revealed an independent association between the highest serum phosphate quartiles and elevated 30-day mortality (HR, 1.28, 95% CI, 1.12 to 1.46), 90-day mortality (HR, 1.22, 95% CI, 1.07 to 1.38), as well as overall mortality (HR, 1.22, 95% CI, 1.07 to 1.38). Conclusions: This study establishes a significant link between higher serum phosphate levels, heightened AKI severity, and increased short-term mortality in AKI patients. The findings emphasize the potential clinical importance of monitoring serum phosphate levels and implementing interventions to manage hyperphosphatemia in the context of AKI.