Characteristics of and Outcomes After Dialysis-Treated Acute Kidney Injury, 2009-2018: A Taiwanese Multicenter Study

Abstract

Rationale & objective: Dialysis-treated acute kidney injury (AKI) is increasingly common in intensive care units (ICUs) and is associated with poor outcomes. Few studies have explored the temporal trends in severity of acute illness at dialysis initiation, indications for dialysis, and their association with patient outcomes.

Study design: Multicenter retrospective cohort study.

Setting & participants: 9,535 adult patients admitted to the ICU who received their first dialysis treatment from Chang Gung Memorial Hospital system in Taiwan from 2009 through 2018.

Exposure: Calendar year.

Outcomes: ICU mortality and dialysis treatment at discharge among hospital survivors.

Analytical approach: The temporal trends during the study period were investigated using test statistics suited for continuous or categorical data. The association between the study year and the risk of mortality was analyzed using multivariable Cox regression with adjustment for relevant clinical variables, including the severity of acute illness, defined by Sequential Organ Failure Assessment (SOFA) score.

Results: The mean SOFA score at dialysis initiation decreased slightly from 14.0 in 2009 to 13.6 in 2018. There was no significant trend in the number of indications for dialysis initiation that were fulfilled over time. Observed ICU mortality decreased over time, and the curve appeared to be reverse J-shaped, with a substantial decrease from 56.1% in 2009 to 46.3% in 2015 and a slight increase afterward. The risk of mortality was significantly reduced from 2013 to 2018 compared with 2009 in adjusted models. The decreasing trend in ICU mortality over time remained significant. There was an increase in dialysis treatment at discharge among survivors, mainly in patients with estimated glomerular filtration rate<60mL/min/1.73m², from 36.8% in 2009 to 43.9% in 2018.

Limitations: Residual confounding from unmeasured factors over time such as severity of comorbidities, detailed medication interventions, and delivered dialysis dose.

Conclusions: We observed reductions in mortality among ICU patients with dialysis-treated acute kidney injury between 2009 and 2018, even after adjusting for dialysis indication and severity of illness at dialysis initiation. However, dialysis treatment at discharge among survivors has increased over time, mainly in patients with preexisting kidney disease.

Plain-language summary: The current medical management of severe acute kidney injury (AKI) is primarily limited to supportive care and kidney replacement therapy if indicated, leading to perceptions that outcomes among intensive care unit (ICU) patients with dialysis-treated AKI have not improved. In this multicenter retrospective study of ICU patients with dialysis-treated AKI between 2009 and 2018 in Taiwan, patient mortality decreased over time despite increasing comorbidities. Moreover, the decreasing linear trends remained significant even when considering severity of acute illness at dialysis initiation, which was based on physiologic and laboratory measurements seldom evaluated in previous studies. Further research should explore the basis for these improvements.

Keywords: Acute kidney injury (AKI); critical illness; dialysis dependence; disease severity; epidemiology; hospital length of stay; intensive care unit (ICU); kidney function; mortality; renal replacement therapy (RRT); secular trend; survival.