BACKGROUND: Although the Kidney Disease: Improving Global Outcomes (KDIGO) criteria are used to define acute kidney injury, the criteria have limitations for including two different serum creatinine criteria in stage 1. We hypothesized that there are differences in clinical outcomes between the two subgroups of stage 1 acute kidney injury in patients undergoing cardiac or thoracic aortic surgery.
METHODS: We reviewed 2510 cases. The KDIGO stage 1 were divided into two subgroups (stage 1a: ≥0.3 mg/dL of absolute increase in serum creatinine, n=376; stage 1b: ≥50% relative increase, n=365). Propensity score analysis was performed between stage 1a and 1b groups, yielding 240 pairs. We compared the length of hospital stay, the incidence of cardiovascular complications, five-year all-cause mortality between these subgroups. Overall survival was compared between the subgroups after propensity score matching. Sensitivity analysis for Acute Kidney Injury Network (AKIN) criteria was performed.
RESULTS: Length of hospital stay and five-year all-cause mortality was significantly worse in patients with KDIGO stage 1b compared to stage 1a. Five-year patient survival was significantly worse in patients with stage 1b compared to stage 1a after matching (Log-rank test P=0.002). We found similar results regarding AKIN criteria. Subgroup analysis showed that the significant difference in survival exists only when baseline serum creatinine ≥0.8mg/dL.
CONCLUSIONS: The KDIGO or AKIN criteria for stage 1 acute kidney injury could be further divided into two substages with different severity of clinical outcomes. This modified criteria could give additional prognostic information in patients undergoing cardiac or thoracic aortic surgery.