IntroductionThe development of acute kidney injury (AKI) is associated with poor outcome. The modified RIFLE (risk, injury, failure, loss of kidney function, and end-stage renal failure) classification for AKI, which classifies patients with renal replacement therapy needs according to RIFLE failure class, improves the predictive value of AKI in patients undergoing cardiac surgery. Our aim was to assess risk factors for post-operative AKI and the impact of renal function on short- and long-term survival among all AKI subgroups using the modified RIFLE classification.MethodsWe prospectively studied 2,940 consecutive cardiosurgical patients between January 2004 and July 2009. AKI was defined according to the modified RIFLE system. Pre-operative, operative and post-operative variables usually measured on and during admission, which included main outcomes, were recorded together with cardiac surgery scores and ICU scores. These data were evaluated for association with AKI and staging in the different RIFLE groups by means of multivariable analyses. Survival was analyzed via Kaplan-Meier and a risk-adjusted Cox proportional hazards regression model. A complete follow-up (mean 6.9 ± 4.3 years) was performed in 2,840 patients up to April 2013.ResultsOf those patients studied, 14% (n = 409) were diagnosed with AKI. We identified one intra-operative (higher cardiopulmonary bypass time) and two post-operative (a longer need for vasoactive drugs and higher arterial lactate 24 hours after admission) predictors of AKI. The worst outcomes, including in-hospital mortality, were associated with the worst RIFLE class. Kaplan-Meier analysis showed survival of 74.9% in the RIFLE risk group, 42.9% in the RIFLE injury group and 22.3% in the RIFLE failure group (P <0.001). Classification at RIFLE injury (Hazard ratio (HR) = 2.347, 95% confidence interval (CI) 1.122 to 4.907, P = 0.023) and RIFLE failure (HR = 3.093, 95% CI 1.460 to 6.550, P = 0.003) were independent predictors for long-term patient mortality.ConclusionsAKI development after cardiac surgery is associated mainly with post-operative variables, which ultimately could lead to a worst RIFLE class. Staging at the RIFLE injury and RIFLE failure class is associated with higher short- and long-term mortality in our population.

Background: The prognostic role of low postoperative serum albumin levels (SAL) after cardiac surgery (CS) remains unclear in patients with normal preoperative SAL. Our aim was to evaluate the influence of SAL on the outcome of CS. Methods: Prospective observational study. Patients undergoing CS with normal preoperative SAL and nutritional status were included and classified into different subgroups based on SAL at 24 h after CS. We assessed outcomes (i.e., in-hospital mortality, postoperative complications and long-term survival) and results were analyzed among the different subgroups of SAL. Results: We included 2818 patients. Mean age was 64.5 ± 11.6 years and body mass index 28.0 ± 4.3Kg•m − 2. 5.8%(n = 162) of the patients had normal SAL levels(≥35 g•L − 1), 32.8%(n = 924) low deficit (30-34.9 g•L − 1), 44.3%(n = 1249) moderate deficit (25-29.9 g•L − 1), and 17.1%(n = 483) severe deficit(< 25 g•L − 1). Higher SAL after CS was associated with reduced in-hospital (OR:0.84;95% CI:0.80-0.84; P = 0.007) and long-term mortality (HR: 0.85;95% CI:0.82-0.87;P < 0.001). Subgroups of patients with lower SAL showed worst long-term survival (5-year mortality:94.3% normal subgroup, 87.4% low, 83.1% moderate and 72.4% severe;P < 0.001). Multivariable analysis showed higher in-hospital mortality, sepsis, hemorrhage related complications, and ICU stay in subgroups of patients with lower SAL. Predictors of moderate and severe hypoalbuminemia were preoperative chronic kidney disease, previous CS, and longer cardiopulmonary bypass time. Conclusions: The presence of postoperative hypoalbuminemia after CS is frequent and the degree of hypoalbuminemia may be associated with worst outcomes, even in the long-term scenario.

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