Abstract
BackgroundThe 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.ResultsWe 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.ConclusionAKI 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.Electronic supplementary materialThe online version of this article (doi:10.1186/s13613-016-0218-5) contains supplementary material, which is available to authorized users.
Highlights
The role of an episode of acute kidney injury (AKI) in long-term mortality among initial survivors of criti‐ cal illness is controversial
A large cohort study revealed the 1-year mortality of 30-day survivors of AKI defined by RIFLE creatinine
The crude 3-year mortality was 54/146 (37.0%; 95% CI 29.2–44.8%) among AKI patients to whom we could not find a matched pair and 146/866 (16.9%; 95% CI 14.4–19.4%) among unmatched patients without AKI
Summary
The role of an episode of acute kidney injury (AKI) in long-term mortality among initial survivors of criti‐ cal 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. AKI has been significantly associated with increased short-term mortality [3, 4, 6, 8], but results about its impact on increased long-term mortality among initial survivors of AKI and critical illness are few and conflicting. 30-day survivors commenced renal replacement therapy (RRT) did not have worse 3-year outcome compared to their propensity-matched control group of hospitalized patients without AKI [10]. Among all ICU patients, the short-term mortality has been related mostly to the type and severity of acute illness, whereas long-term mortality among initial survivors has been primarily determined by patient age and comorbidities [11], which are well-known predisposing factors for the development of AKI [1]
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