Impact of pre-hospital renal function on the detection of acute kidney injury in acute decompensated heart failure

Background: Acute kidney injury (AKI) is a serious complication in patients hospitalized for decompensated heart failure (HF). Currently, AKI definitions consider creatinine levels at admission as reference of baseline renal function (RF). However, renal impairment may already be present at admission. We aimed to study the impact on AKI detection of considering outpatient RF as reference. Methods: In a cohort of 458 patients hospitalized for decompensated HF, we studied the occurrence of AKI using the standardized KDIGO criteria and grading (stages: 1, 2, 3), and considering two different definitions according to the RF used as reference or baseline: the latest outpatient measurement prior to admission vs. the first measurement at admission. We compared the prevalence, timing and prognostic value for both AKI definitions. Results: The definition based on outpatient RF was associated with an increase in overall AKI detection from 20.1% to 33.8% (p < 0.001), and from 3.1% to 5.0% for advanced stages (2-3) (p < 0.001); additionally, 12.5% of patients already had criteria of AKI at admission (36.8% of AKI cases). Both definitions were associated with longer hospital stay. However, only AKI already present at admission, as based on pre-hospital creatinine, was independently associated with all-cause death, in-hospital and after discharge, and death or HF readmission in the follow-up: 1 stage (HR 2.72, 95%CI 1.83-4.06, p < 0.001) and 2-3 stage (HR 7.29, 95%CI, 3.02-17.64, p < 0.001). Conclusions: Evaluation of AKI in patients admitted with HF should consider pre-hospital RF, since it improves early identification of AKI and has implications for risk assessment.