Hospital-associated acute kidney injury (HA-AKI) is associated with increased inpatient mortality. Our objective was to categorize HA-AKI based on the timing of minimum and peak inpatient serum creatinine (sCr) and describe the association with inpatient mortality. Materials and Methods: This study is a retrospective analysis of an administrative data set for adults admitted to a single medical center for over 4 years. Changes and timing of the minimum and peak sCr were used to define HA-AKI categories. Results: Peak creatinine followed minimum creatinine for HA-AKI, and preceded the minimum value for transient HA-AKI (THA-AKI). A subset of patients developed HA-AKI after recovering from THA-AKI. Multivariable Cox regression analyses examined the association between these categories and 28-day inpatient mortality, adjusting for age, sex, race, Charlson comorbidity index, baseline kidney function, AKI recovery and renal replacement therapy. There were 50,601 patients included in the analyses, and 29,996 (59%) did not have AKI. There were 2,440 deaths; HA-AKI had a 2.24-fold (95% CI 1.99-2.51) increased risk, while THA-AKI group (12,101) had a 1.23-fold (95% CI 1.09-1.40) increased risk for inpatient mortality. THA-AKI patients who recovered and then developed HA-AKI had the same mortality risk as THA-AKI (1.27-fold [95% CI 1.07-1.51]) but longer hospitalization and less recovery from AKI. Conclusions: Risk of short-term inpatient mortality is associated with AKI, and this risk is attenuated with recovery of kidney function in the hospital. Systematic surveillance with repeated inpatient sCr values is needed to assess the short- and long-term consequences of HA-AKI.

Keywords:
Serum creatinine, Epidemiology, Multivariable regression models
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