Impact on Outcomes across KDIGO-2012 AKI Criteria According to Baseline Renal Function

Abstract

Acute kidney injury (AKI) and Chronic Kidney Disease (CKD) are global health problems. The pathophysiology of acute-on-chronic kidney disease (AoCKD) is not well understood. We aimed to study clinical outcomes in patients with previous normal (pure acute kidney injury; P-AKI) or impaired kidney function (AoCKD) across the 2012 Kidney Disease Improving Global Outcomes (KDIGO) AKI classification. We performed a retrospective study of patients with AKI, divided into P-AKI and AoCKD groups, evaluating clinical and epidemiological features, distribution across KDIGO-2012 criteria, in-hospital mortality and need for dialysis. One thousand, two hundred and sixty-nine subjects were included. AoCKD individuals were older and had higher comorbidity. P-AKI individuals fulfilled more often the serum creatinine (SCr) ≥ 3.0× criterion in AKI-Stage3, AoCKD subjects reached SCr ≥ 4.0 mg/dL criterion more frequently. AKI severity was associated with in-hospital mortality independently of baseline renal function. AoCKD subjects presented higher mortality when fulfilling AKI-Stage1 criteria or SCr ≥ 3.0× criterion within AKI-Stage3. The relationship between mortality and associated risk factors, such as the net increase of SCr or AoCKD status, fluctuated depending on AKI stage and stage criteria sub-strata. AoCKD patients that fulfil SCr increment rate criteria may be exposed to more severe insults, possibly explaining the higher mortality. AoCKD may constitute a unique clinical syndrome. Adequate staging criteria may help prompt diagnosis and administration of appropriate therapy.

Keywords: AKI staging; acute kidney injury; chronic kidney disease.

Figure 1

Study flow chart for inclusion and exclusion criteria. RRT: Renal replacement therapy; SOT: Solid organ transplantation; Tb: Times baseline. SCr: Serum creatinine; eGFR: Estimated glomerular filtration rate; P-AKI: Pure acute kidney injury; AoCKD: Acute on chronic kidney disease.

Figure 2

Kaplan-Meier curves. In-hospital survival curves stratified by baseline renal function and AKI severity. P-AKI: Pure Acute kidney injury. AoCKD: Acute-on-chronic kidney disease. AKI: Acute kidney injury. ST1: AKI stage 1. ST2: AKI stage 2. ST3: AKI stage 3.

Figure 3

Unadjusted and adjusted hazard ratios (95% confidence interval) for death. P-AKI: Pure acute kidney injury. AoCKD: Acute-on-chronic kidney disease. AKI: Acute kidney injury. ST1: AKI stage 1. ST2: AKI stage 2. ST3: AKI stage 3. SCr: Serum creatinine. Tb: Times baseline. RRT: Renal replacement therapy. α: Models including P-AKI/AoCKD status, age, intensive care unit admission (considered as time-dependent variables), gender, Charlson Index, and comorbidity (hypertension, diabetes, coronary artery disease, chronic heart failure, peripheral arterial disease and chronic hepatic disease). * p < 0.05; ** p < 0.01; *** p < 0.001.

Figure 4

Adjusted hazard ratios (95% confidence interval) for death. NI: Net increase. SCr: Serum creatinine. eGFR: Estimated glomerular filtration rate. P-AKI: Pure acute kidney injury. AoCKD: Acute-on-chronic kidney disease. Tb: Times baseline. a: Models including SCr NI, baseline eGFR, age, Intensive care unit admission (considered as time-dependent variables), gender, Charlson Index, and comorbidity (hypertension, diabetes, coronary artery disease, chronic heart failure, peripheral arterial disease and chronic hepatic disease. b: Models including SCr NI, P-AKI/AoCKD status, age, intensive care unit admission (considered as time-dependent variables), gender, Charlson Index, and comorbidity (hypertension, diabetes, coronary artery disease, chronic heart failure, peripheral arterial disease and chronic hepatic disease. * p < 0.05; ** p < 0.01; *** p < 001.

Figure 5

Mean in-hospital survival time (days) by baseline renal function and KDIGO AKI stage and criteria. P-AKI: Pure acute kidney injury. AoCKD: Acute-on-chronic kidney disease. AKI: Acute kidney injury. ST1: AKI stage 1. ST2: AKI stage 2. ST3: AKI stage 3. SCr: Serum creatinine. RRT: Renal replacement therapy. * p < 0.05; ** p < 0.01.