ACUTE RENAL FAILURE
Epidemiologic Variables
The incidence and outcomes of acute kidney injury (AKI)
in the ICU are highly variable. Reported incidences can be
as high as 35%.147 Renal replacement therapy is the mainstay
of support for these patients, but mortality remains
high. Despite improvements in renal replacement technology
over the years, mortality caused by AKI in the ICU
has remained at higher than 50%.148
Diagnosis
The diagnosis of AKI has not been straightforward. A
recent survey revealed the use of at least 35 definitions
in the literature.149 This state of confusion has given rise
to the wide variation in reported incidence and clinical
significance of ARF. The Acute Dialysis Quality Initiative
(ADQI), which is made up of a group of experts consisting
of nephrologists and intensivists, has proposed new criteria
for describing renal dysfunction. They recognized the
clinical importance of milder forms of renal insufficiency
and that stratifying renal dysfunction (mild to severe)
would better describe the disease. They proposed the RIFLE
criteria (Table 101-4), which stand for risk, injury, failure,
and two outcome classes (loss and end-stage kidney disease).
For each increasing RIFLE class, a stepwise increase
in mortality independent of comorbidity occurs.150 These
data suggest that strategies to prevent even mild AKI may
improve survival, and recovery of renal function in the
ICU should be a specific therapeutic target.