RESUMO
BACKGROUND: Acute kidney injury (AKI) is an independent risk factor for mortality in adults and children. Generally, urine output (UO) < 1 mL/kg/h is accepted as oliguria in neonates, although it has not been systematically studied. pRIFLE criteria suggest UO cut-offs similar to those of the adult population (0.3 and 0.5 mL/kg/h). The aim of the present study was to investigate UO in correlation with mortality in critically ill neonates and suggest changes in the pRIFLE definition of reduced diuresis. METHODS: A retrospective cohort study was performed in an eight-bed neonatal intensive care unit (NICU). UO was systematically measured by diaper weight each 3 h. Discriminatory capacity to predict mortality of UO was measured and patients were divided according to UO ranges: G1 > 1.5 mL/kg/h; G2 1.0-1.5 mL/kg/h; G3 0.7-1.0 mL/kg/h and G4 < 0.7 mL/kg/h. These ranges were incorporated to pRIFLEGFR criteria and its performance was evaluated. RESULTS: Of 384 patients admitted at the NICU during the study period, 72 were excluded and overall mortality was 12.8%. UO showed good performance for mortality prediction (area under the curve 0.789, P < 0.001). There was a stepwise increase in hospital mortality according to UO groups after controlling for SNAPPE-II and diuretic use. Using these UO ranges with pRIFLE improves its discriminatory capacity (area under the receiver operating characteristic curve 0.882 versus 0.693, P < 0.05). CONCLUSIONS: UO is a predictor of mortality in NICU. An association between a UO threshold < 1.5 mL/kg/h and mortality was observed, which is higher than the previously published pRIFLE thresholds. Adopting higher values of UO in pRIFLE criteria can improve its capacity to detect AKI severity in neonates.
Assuntos
Injúria Renal Aguda/classificação , Injúria Renal Aguda/mortalidade , Mortalidade Hospitalar , Unidades de Terapia Intensiva , Oligúria/mortalidade , Micção/fisiologia , Injúria Renal Aguda/urina , Adulto , Estado Terminal , Feminino , Humanos , Recém-Nascido , Masculino , Oligúria/etiologia , Prognóstico , Curva ROC , Estudos Retrospectivos , Fatores de Risco , Taxa de SobrevidaRESUMO
Oliguria is a valuable marker of kidney function and a criterion for diagnosing and staging acute kidney injury (AKI). However, the utility of urine output as a specific metric for renal dysfunction is somewhat controversial. To study this issue further we tested whether urine output is a sensitive, specific, and early measure for diagnosing and staging AKI in 317 critically ill patients in a prospective observational study. Urine output was assessed every hour and serum creatinine every 12 to 24 h. The sensitivity and specificity of different definitions of oliguria for the diagnosis of AKI were compared with the Acute Kidney Injury Network serum creatinine criterion. The incidence of AKI increased from 24%, based solely on serum creatinine, to 52% by adding the urine output as a diagnostic criterion. Oliguric patients without a change in serum creatinine had an intensive care unit mortality rate (8.8%) significantly higher than patients without AKI (1.3%), and similar to oliguric patients with an increase in serum creatinine (10.4%). The diagnosis of AKI occurred earlier in oliguric than in non-oliguric patients. Oliguria of more than 12 h and oliguria of 3 or more episodes were associated with an increased mortality rate. Thus, urine output is a sensitive and early marker for AKI and is associated with adverse outcomes in intensive care unit patients.