Acute Kidney Injury Network definition of contrast-induced nephropathy in the critically ill: incidence and outcome.

INTRODUCTION: Contrast-induced nephropathy (CIN) has been extensively studied in the ward but only scarcely in intensive care unit (ICU) patients, even if they may be particularly prone to develop or to worsen acute kidney insufficiency. We aimed to measure the incidence of CIN in a large ICU population using the Acute Kidney Injury Network (AKIN) definition and to investigate its impact on patients' outcome.

METHODS: In this 3-year retrospective study, we included all patients undergoing, during their stay in our medical ICU, a contrast media-enhanced computed tomographic scan. Change in serum creatinine between baseline (24 hours before to 12 hours after contrast media injection) and its maximum value over the 96 hours after contrast media injection was recorded. Contrast-induced nephropathy was defined as a 44.2-μmol/L absolute or a 25% relative minimal increase in serum creatinine over 48, 72, or 96 hours and according to the stage 1 of the AKIN classification (at least 26.4 μmol/L or 50% increase over 48 hours).

RESULTS: A total of 398 contrast-enhanced computed tomographic scans performed among 299 patients were analyzed. Incidence of CIN was 14% according to the AKIN definition and ranged from 8% (48-hour absolute definition) to 23% (96-hour relative definition). The need for renal replacement therapy and ICU mortality were significantly higher in case of CIN. After adjusting for other variables associated with ICU mortality, the occurrence of at least 1 CIN episode during the ICU stay (AKIN criteria) was independently associated with ICU mortality (odds ratio, 3.85; 95% confidence interval, 1.85-8.00).

CONCLUSIONS: Even if incidence varied greatly depending on the definition, CIN appeared frequent in our critically ill patients. The AKIN definition, independently associated with ICU mortality, may allow unifying diagnostic criteria to further evaluate this condition that impacts morbidity and mortality.