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 study was to determine sub-KDIGO thresholds that identify patients with 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 output was collected from the 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 by KDIGO 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 in multivariable 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.

The clinical utility of kinetic glomerular filtration rate

“…The authors appreciate that hourly urine output can be a predictor of AKI or of impending requirement for acute RRT [26, 27]. It has variable sensitivity however, and the most encouraging of previous studies has suggested decreasing urinary output has an ROC of 0.7 for detecting AKI [28]. Thus, while urine output compares favourably to kGFR it has the disadvantage of requiring more intensive nursing and urine monitoring and with an intrinsic degree of unreliability in measurement.…”

Oliguria and Biomarkers of Acute Kidney Injury: Star Struck Lovers or Strangers in the Night?

“…Moreover, the prediction of AKI by urinary output varied by the patient cohort with the performance being better in medical than in surgical patients. In septic shock, a duration of at least 5 h, however, appears to be a good predictor of AKI [15]. Finally, Md Ralib et al [16] found a correlation between the volume of urinary output and duration of oliguria which suggested that a lower threshold of 0.3 ml/kg/h should be used, if the 6-hour observation interval is used as a minimum for the definition of stage of AKI.…”

Innovative Use of Novel Biomarkers to Improve the Safety of Renally Eliminated and Nephrotoxic Medications

“…In the setting of AKI, decreases in urine output often precede increases in S cr . However, urine output still remains a less than ideal surrogate of renal function . Decreased urine flow rate may reflect hypovolemia without a corresponding decrease in GFR.…”