Incidence and outcomes of acute kidney injury in intensive care units: A Veterans Administration study

Objectives: To examine the effect of severity of acute kidney injury or renal recovery on risk-adjusted mortality across different intensive care unit settings. Acute kidney injury in intensive care unit patients is associated with significant mortality. Design. Retrospective observational study. Setting. There were 325,395 of 617,927 consecutive admissions to all 191 Veterans Affairs ICUs across the country. Patients: Large national cohort of patients admitted to Veterans Affairs ICUs and who developed acute kidney injury during their intensive care unit stay. Measurements and Main Results. Outcome measures were hospital mortality, and length of stay. Acute kidney injury was defined as a 0.3-mg/dL increase in creatinine relative to intensive care unit admission and categorized into Stage 1 (0.3 mg/dL to <2 times increase), Stage 11 (>= 2 and <3 times increase), and Stage III (>= 3 times increase or dialysis requirement). Association of mortality and length of stay with acute kidney injury stages and renal recovery was examined. Overall, 22% (n = 71,486) of patients developed acute kidney injury (Stage 1: 17.5%; Stage 11: 2.4%; Stage 111: 2%); 16.3% patients met acute kidney injury criteria within 48 hrs, with an additional 5.7% after 48 hrs of intensive care unit admission. Acute kidney injury frequency varied between 9% and 30% across intensive care unit admission diagnoses. After adjusting for severity of illness in a model that included urea and creatinine on admission, odds Of death increased with increasing severity of acute kidney injury. Stage I odds ratio 2.2 (95% confidence interval, 2.17-230); Stage 11 odds ratio 6.1 (95% confidence interval, 5.74, 6.44.); and Stage III odds ratio = 8.6 (95% confidence interval, 8.07-9.15). Acute kidney injury patients with sustained elevation of creatinine experienced higher mortality risk than those who recovered. Interventions. None. Conclusions: Admission diagnosis and severity Of illness influence frequency and severity of acute kidney injury. Small elevations in creatinine in the intensive care unit are associated with increased risk-adjusted mortality across all intensive care unit settings, whereas renal recovery was associated with a protective effect. Strategies to prevent even mild acute kidney injury or promote renal recovery may improve survival. (Crit Care Med 2009; 37:2552-2558)