Derivation of urine output thresholds that identify a very high risk of AKI in patients with septic shock

Abstract

Background and objectives To promote early detection of AKI, recently proposed pretest probability models combine sub–Kidney Disease Improving Global Outcomes (KDIGO) AKI criteria with baseline AKI risk. The primary objective of this studywas to determine sub-KDIGOthresholds that identify patientswith septic shock at highest risk for AKI. Design, setting, participants, & measurements This was a retrospective analysis of 390 adult patients admitted to the medical intensive care unit (ICU) of a tertiary, academic medical center with septic shock between January 2008 and December 2010.Hourly urine outputwas collected fromthe time of septic shock recognition (hour 0) to hour 96, urine catheter removal, or ICU discharge (whichever occurred first). All available serum creatinine (SCr) measurements were collected until hour 96. The AKI pretest probability model was assessed during the first 12 hours of resuscitation and included the initial episode of oliguria, increase from baseline to peak SCr level, and Acute Physiology and Chronic Health Evaluation (APACHE) III score in a multivariable receiver-operator characteristic (ROC) analysis. The primary outcome was the incidence of stage II or III (stage II+) AKI defined byKDIGO criteria. Secondary outcomes included the need for RRT and 28-day mortality. Results Ninety-eight (25%) patients developed stage II+ AKI after septic shock recognition. APACHE III score and increase in SCr level in the first 12 hours were not statistically associated with stage II+ AKI inmultivariable ROC analysis. Consecutive oliguria for 3 hours had fair predictive ability for achieving stage II+AKI criteria (area under ROC curve, 0.73; 95% confidence interval [95% CI], 0.68 to 0.78), and oliguria for 5 hours demonstrated optimal accuracy (82%; 95% CI, 79% to 86%). Conclusions Three to 5 hours of consecutive oliguria in patients with septic shock may provide a valuable measure of AKI risk. Further validation to support this finding is needed.