Redefining renal dysfunction in trauma: implementation of the Acute Kidney Injury Network staging system.
BACKGROUND
Acute renal failure (ARF) in trauma patients is associated with high mortality rates. There is currently no consensus definition for renal failure, however, the American College of Surgeons' Committee on Trauma (ACSCOT) defines ARF as a serum creatinine > or =3.5, blood urea nitrogen > 100, or renal replacement therapy. We hypothesize that by using the Acute Kidney Injury Network (AKIN) staging system we would identify smaller changes in renal function that may impact outcome, and may serve as a marker for mortality and other organ dysfunction.


METHODS
We retrospectively identified all trauma patients admitted to the surgical intensive care unit (SICU) for >48 hours during a 3-year period ending December 2007. Hourly urine output, serum creatinine, demographic data, trauma scores, admission vital signs, ICU and hospital length of stay, need for renal replacement therapy, organ failure, and death were collected and were stratified according to AKIN and ACSCOT renal dysfunction criteria. Trauma patients admitted to the SICU who did not develop renal dysfunction were used as controls.


RESULTS
A total of 571 patients were studied. Of those, only 17 patients (3.0%) were classified as having ARF by the ACSCOT criteria, whereas 170 (29.8%) had kidney injury using the AKIN criteria (146, stage 1; 15, stage 2; 9, stage 3). Compared with patients admitted to the ICU for > or =48 hours with normal renal function, patients meeting AKIN criteria had longer hospital and ICU length of stay (p < 0.001). Patients meeting AKIN criteria also had an increased incidence of multiple organ failure and death (p < 0.03).


CONCLUSIONS
Stratification using the AKIN criteria for acute kidney injury identifies an increased number of patients with renal dysfunction compared with the current ACSCOT criteria. Importantly, these patients have an increased risk of multiple organ failure and death. Inclusion into the AKIN criteria may be a marker for later morbidity and mortality.