The role of an episode of
acute kidney injury (AKI) in long-term mortality among initial survivors
of critical illness is controversial. We aimed to determine whether AKI
is independently associated with decreased survival at 3 years among
30-day survivors of intensive care.

We included 2336 30-day
survivors of intensive care enrolled in the FINNAKI study conducted in
seventeen medical–surgical ICUs in Finland during a 5-month period in
2011–2012. The incidence of AKI, defined by the Kidney Disease:
Improving Global Outcomes criteria, was 34.6%, and 192 (8.3%) commenced
RRT. The 3-year mortality among AKI patients was 23.5% (95% CI
20.6–26.4%) compared to 18.9% (17.0–20.9%) of patients without AKI, p = 0.01.
However, after adjustments using Cox proportional hazards regression,
AKI was not associated with decreased 3-year survival (HR 1.05; CI 95%
0.86–1.27), whereas advanced age, poor pre-morbid functional
performance, and presence of several comorbidities were. Additionally,
we matched AKI patients to non-AKI patients 1:1 according to age,
gender, presence of severe sepsis, and a propensity score to develop
AKI. In the well-balanced matched cohort, 3-year mortality among AKI
patients was 136 of 662 (20.5%; 17.5–23.6%) and among matched non-AKI
patients 143 of 662 (21.6%; 18.5–24.7%), p = 0.687.
Neither AKI nor RRT was associated with decreased survival at 3 years
in the sensitivity analyses that excluded patients (1) with chronic
kidney disease, (2) with AKI not commenced renal replacement therapy
(RRT), and (3) with estimated pre-admission creatinine, chronic kidney
disease, or AKI stage 1.

AKI was not an independent
risk factor for 3-year mortality among 30-day survivors. Increased
3-year mortality among patients with AKI who survive critical illness
may not be related to AKI per se, but rather to advanced age and
pre-existing comorbidities.