Incidence and Outcomes of Acute Kidney Injury Requiring Renal Replacement Therapy: A Retrospective Cohort Study

Abstract

Background: Incidence of acute kidney injury (AKI), requiring dialysis, is on the rise globally and is associated with high mortality and morbidity. Aim: This study is aimed at examining the incidence of AKI requiring renal replacement therapy (RRT) in the Tayside region of Scotland and the impact of RRT for AKI on morbidity, mortality and length of hospital stay. Methods: One hundred seventy eight patients (>18 years of age) who received acute RRT between January 1, 2012 and December 31, 2012 were retrospectively selected for inclusion in the longitudinal cohort study. Incidence rate was calculated. Length of hospital stay, likely cause of AKI, renal recovery and mortality data were collected for a follow-up period of 1 year or until death. Chi-square test was used to compare the morbidity and mortality data between subgroups. RRT-free survival and time-until-event (death or RRT) analysis was performed using Kaplan-Meier plots. Cox-regression was used to examine the relationship between age, sex, diabetes and chronic kidney disease (CKD) on survival. Results: Incidence of AKI requiring RRT was 430 per million population per year. Median length of hospital stay was 21 days. In-patient mortality was 36%, mortality at 90 days was 44% and at 1 year 54%. Median time from start of RRT until death or chronic RRT was 90 days (95% CI 14-166). One-year cumulative RRT-free survival was 26% in the ward, 36% in high dependency units and 48% in intensive care unit subgroups. Diabetes, gender and CKD at baseline did not affect RRT-free survival in the cohort being studied. A quarter of the cohort regained full renal function and 15% of survivors were on a chronic dialysis programme at 1 year. Conclusions: This study gives a comprehensive summary of renal outcomes and mortality after a single episode of AKI requiring RRT. The findings of the study confirm that dialysis-dependent AKI is associated with increased length of hospital stay, high mortality and loss of renal function long term, emphasizing the importance of recognition, classification and prevention of AKI.