The predictive value of early acute kidney injury for long-term survival and quality of life of critically ill patients

Background: Prognostic factors for the combination of long-term survival and health-related quality of life (HRQoL) after intensive care unit (ICU) stay have not yet been studied. Our aim was to assess whether early acute kidney injury (eAKI), AKI occurring on the first day of ICU admission, is an independent predictor of this combined one-year outcome.

Methods: We included all patients admitted to the mixed ICU of the University Medical Centre Utrecht between July 2009 and April 2013, excluding patients with chronic dialysis, cardiac surgery, and length of stay shorter than 24 hours. eAKI was defined using the risk, injury, failure, loss, end-stage renal failure (RIFLE) classification, using a newly developed algorithm to classify AKI based on routinely collected patient data. In one-year survivors, HRQoL was measured using the EuroQoL 5D-3L™ (EQ-5D) questionnaire. The primary outcome measure was "poor outcome", defined as an EQ-5D index score <0.4 or death after one year follow up. A multivariable Poisson regression model was performed to adjust for age, comorbidities, admission type and severity of disease factors.

Results: We enrolled 2,420 patients, of whom 871 (36.0 %) died within one year. An additional 286 of 1549 one-year survivors (11.8 %) experienced low HRQoL. The respective incidence of the RIFLE classes, risk, injury and failure, were 456 (18.8 %), 253 (10.5 %) and 123 (5.1 %). After adjustment for other covariates, the RIFLE classes, injury and failure, were independently associated with poor outcome (adjusted relative risk 1.14, 95 % CI 1.01, 1.29; p = 0.03, and 1.25, 95 % CI 1.01, 1.55; p = 0.04), when compared to no eAKI patients . The constituents of this composite outcome were also analysed separately. In a Cox regression model the RIFLE classes, injury and failure, were significantly associated with mortality (adjusted hazard ratio 1.35, 95 % CI 1.11, 1.65; p <0.01, and 1.78, 95 % CI 1.38, 2.30; p <0.01). In one-year survivors specifically, none of the RIFLE classes were significantly associated with low HRQoL.

Conclusions: ICU patients with moderate or severe AKI during the first 24 hours have a higher probability of mortality or low HRQoL (combined poor outcome), one year after ICU admission. Together with other available early prognostic factors, information on early acute kidney injury could improve informed decision-making on the continuation or withdrawal of treatment in ICU patients.