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Comparative Study
. 2015 Sep;26(9):2231-8.
doi: 10.1681/ASN.2014070724. Epub 2015 Jan 7.

Classifying AKI by Urine Output versus Serum Creatinine Level

John A Kellum  1 , Florentina E Sileanu  2 , Raghavan Murugan  3 , Nicole Lucko  3 , Andrew D Shaw  4 , Gilles Clermont  3
Affiliations
Comparative Study

Classifying AKI by Urine Output versus Serum Creatinine Level

John A Kellum et al. J Am Soc Nephrol. 2015 Sep.

Abstract

Severity of AKI is determined by the magnitude of increase in serum creatinine level or decrease in urine output. However, patients manifesting both oliguria and azotemia and those in which these impairments are persistent are more likely to have worse disease. Thus, we investigated the relationship of AKI severity and duration across creatinine and urine output domains with the risk for RRT and likelihood of renal recovery and survival using a large, academic medical center database of critically ill patients. We analyzed electronic records from 32,045 patients treated between 2000 and 2008, of which 23,866 (74.5%) developed AKI. We classified patients by levels of serum creatinine and/or urine output according to Kidney Disease Improving Global Outcomes staging criteria for AKI. In-hospital mortality and RRT rates increased from 4.3% and 0%, respectively, for no AKI to 51.1% and 55.3%, respectively, when serum creatinine level and urine output both indicated stage 3 AKI. Both short- and long-term outcomes were worse when patients had any stage of AKI defined by both criteria. Duration of AKI was also a significant predictor of long-term outcomes irrespective of severity. We conclude that short- and long-term risk of death or RRT is greatest when patients meet both the serum creatinine level and urine output criteria for AKI and when these abnormalities persist.

Keywords: ARF; dialysis; mortality.

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Figures

Figure 1.
Figure 1.
Age-adjusted survival and RRT rates by AKI severity. Groups refer to combinations of UO and creatinine criteria depicted in Table 3 and Supplemental Table 5. Group 1 (green), no AKI by either criterion; group 2 (blue), stages 1–2 by UO criteria but no AKI by SC or stage 1 by SC and no AKI by UO; group 3 (yellow), stages 1–2 by UO plus stage 1 by SC or stages 2–3 by SC alone; group 4 (orange), stages 1–2 by UO plus stage 2 by SC or stage 3 by UO alone; group 5 (red), stage 3 by UO plus stages 1–2 by SC or stage 3 by SC plus stages 1–2 by UO; and group 6 (dark red), stage 3 by both criteria. The top panel shows age-adjusted 1-year survival for all patients (10 patients had missing age). The bottom panel shows age-adjusted 1-year dialysis rates for patients that entered the USRDS before 1 year. Patients who died before 1 year are excluded. Overall differences by groups are significant for both sets (P<0.001).
Figure 2.
Figure 2.
Age-adjusted 1-year risk for death or RRT for AKI staging based solely on UO or creatinine criteria. Shown are death or RRT rates over 1 year (includes in-hospital events) for patients with AKI staging based solely on UO (no AKI by SC; 7 patients had missing age) (top) and those with AKI based solely on SC (no AKI by UO; 8 patients had missing age) (bottom). Overall differences by stage are significant for both sets (P<0.001).
Figure 3.
Figure 3.
Relationship between duration of AKI and death or dialysis at 1 year after ICU admission. (A) Duration of AKI by SC criteria (in all patients with or without AKI by UO) and likelihood of death or dialysis at 1 year. Likelihood of death or dialysis is significantly different by stage and also by time (P<0.001 and P=0.02, respectively) and the interaction between time and stage is significant (P<0.001). (B) Duration of AKI by SC criteria and likelihood of death or dialysis at 1 year (excludes death or RRT during the index hospitalization). Likelihood of death or dialysis is significantly different by stage and also by time (P=0.01 and P<0.001, respectively). (C) Duration of AKI by UO criteria (in all patients with or without AKI by SC) and likelihood of death or dialysis at 1 year. Likelihood of death or dialysis is significantly different by stage and also by time (analysis limited to only patients with stages 2–3) (P<0.001). (D) Duration of AKI by UO criteria and likelihood of death or dialysis at 1 year (excludes death or RRT during the index hospitalization). Likelihood of death or dialysis is significantly different by stage and also by time (analysis limited to only patients with stages 2–3) (P<0.001).
Figure 4.
Figure 4.
The source population included all patients cared for in an ICU over the 8-year study period. The study population included 32,045 patients (70.2% of the source population) after excluding missing data (mainly urine output) and ESRD.
See this image and copyright information in PMC

References

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