Title:incidence and Outcomes of Acute Kidney Injury after Cardiac Surgery Using Either Criteria of the Rifle Classification Reviewer: Linda Rydén

was modified accordingly. Only the results of the multivariate model were described. «Heavier» was changed by «higher BMI». Introduction: Line 16-17: Authors state they look for “...the preoperative risk factors...”. However they state in the abstract (background) “. Pre and per-operative risk factors...”. Please state what is the correct aim of this particular part of the study. Introduction was corrected accordingly. «Preoperative risk factors» was replaced by «preand per-operative risk factors» since this is indeed the aim of our study. Methods: State why authors use sCr 7 days before surgery or if this is arbitrary. Please state what kind of Kaplan-Meier test authors used. A question: Why any patient was staged on Loss(L) or End(E) of the RIFLE classification? (I presume no patient fulfill those criteria). Were the patients treated with diuretics? What is the policy regarding diuretic treatment and RRT at your institution and does it influence RIFLE staging? The baseline serum creatinine was systematically assessed at the time of preoperative consultation of anaesthesia, i.e. 7 days before surgery. The Cox proportional hazard method was used for the Kaplan-Meier test and specified in text. No patient fulfilled “Loss” or “End” stage kidney disease in our cohort. This was stated in text. The use of diuretic and/or renal replacement therapies was at the discretion of the physicians in charge. This was stated in text. Discussion: Please explain briefly why you choose RIFLE for evaluating AKI (see Crit Care. 2013 Dec 13;17(6):R293. doi: 10.1186/cc13159 and Crit Care. 2011;15(1):R16. doi: 10.1186/cc9960). The main original contribution is to compare the different AKI incidence by means of UO or sCr. Please emphasize that. Please show results and statistical analysis regarding the sentence “Patients presenting with impaired kidney function before surgery were significantly older”. Two references were added in the discussion to support our choice of RIFLE classification: Englberger L, Suri RM, Li Z, Casey ET, Daly RC, Dearani JA, Schaff HV: Clinical accuracy of RIFLE and Acute Kidney Injury Network (AKIN) criteria for acute kidney injury in patients undergoing cardiac surgery. Crit Care 2011, 15:R16. Lopez-Delgado JC, Esteve F, Torrado H, Rodriguez-Castro D, Carrio ML, Farrero E, Javierre C, Ventura JL, Manez R: Influence of acute kidney injury on shortand longterm outcomes in patients undergoing cardiac surgery: risk factors and prognostic value of a modified RIFLE classification. Crit Care Lond Engl 2013, 17. We’ve emphasized that the original contribution of our study was to compare AKI incidence and outcomes according to SCr versus UO RIFLE criteria. We’ve added results and statictical analysis to the sentence concerning the age of patients presenting with or without preoperative impaired kidney function. Minor Essential Revisions: Results: Please, report in results section the % 1-year mortality rate and the P between survivors and non-survivors. Delete isolate valve surgery OR since does not add anything relevant (line 25). Table 4: Change “Sexe” for “male or female gender”. Please do the same within all the tables. Figure 1: Please add survival of non-AKI patients. Please, report the % 1-year mortality rate. Corrections were made accordingly in text, tables and figures. Discretionary Revisions: Results: If possible, it would add good value to the manuscript to know the cause of in-hospital and long-term mortality. It would be interesting if authors can report mean UO and mean sCr with Standard deviation during the 7 days in all the population We’ve listed the causes of in-hospital mortality. Unfortunately, we were unable to consistently establish the causes of long-term mortality. On the basis of available data for our study, we could not reliably report on mean UO and mean SCr with Standard deviation during the 7 days in all the population.