Acute on Chronic Renal Failure has Worse Postoperative Outcomes than End-Stage Renal Disease Following Cardiac Surgery

Background: Renal failure is a systemic disorder and has destructive effects among all organs including cardiovascular system. The development of postoperative acute kidney injury has been recognized as one of the strongest risk factor for mortality in patients undergoing cardiac surgery. Aim/Objective: To investigate postoperative course of acute on chronic renal failure after cardiac surgery and defi ne perioperativerisk factors for predicting postoperative acute renal failure (ARF) development. Materials and Methods: From January 2006 to December 2014, data of 3038 patients undergone cardiac surgery was retrospectively reviewed. Data of 42 chronic renal failure (CRF) patients who undergone dialysis at early postoperative period (≤30 days after cardiac surgery) were selected and evaluated. Group 1 (n=18) was consisted of patients who have preoperative dialysis dependent CRF and undergone dialysis after cardiac surgery, while Group 2 (n=24) was consisted of patients who have preoperative dialysis nondependent CRF and undergone dialysis after cardiac surgery. Preoperative clinical characteristics and demographics, operational data of patients as well as postoperative outcomes of patient groups were analyzed, hereby a comparison of two groups was performed. Results: There were not statistically difference between groups for neuropsychiatriccomplications, wound infectious complications, septiccomplications, reexploration, duration of ventilation, cardioversion, intraaortic balloon pump support, pleural effusion, pericardial effusion and total drainage amounts. Positive inotropic necessity, signifi cant electrocardiographicchanges, reintubation necessity and transfusion amounts were statistically higher in Group 2. Patients in Group 2 had a signifi cant longer intensive care unit (ICU) stay (mean length of ICU stay was 4 days in Group 1, while 6 days in Group 2, p = 0.01) and total hospital stay (mean length of total hospital stay was 9 days in Group 1, while 15 days in Group 2, p = 0.006). Thirty-day mortality rate was statistically higher in Group 2 (p = 0.044). Conclusion: End stage renal failure is one of the worst preoperative risk factor for cardiac surgery but postoperative ARF development results with worst outcomes even patients had preoperative dialysis non-dependent CRF. So preoperative estimated glomerular fi ltration rate should be calculated to estimate ARF development risk, instead of evaluating with only serum creatinine. Research Article Acute on Chronic Renal Failure has Worse Postoperative Outcomes than End-Stage Renal Disease Following Cardiac Surgery Barış Durgun1, Ahmet Yüksel2*, Gökhan Erol1, Mevlüt Kobuk1 and Suat Doğancı1 1Department of Cardiovascular Surgery, Gulhane Military Medical Academy, Ankara, Turkey 2Department of Cardiovascular Surgery, Bursa State Hospital, Bursa, Turkey Dates: Received: 11 March, 2017; Accepted: 01 April, 2017; Published: 04 April, 2017 *Corresponding author: Ahmet Yüksel, Department of Cardiovascular Surgery, Bursa State Hospital, Tophane Street, 16041, Bursa, Turkey. Tel: +90 505 8460753, Fax: +90 224 2132993. E-mail:


Introduction
Renal failure is a systemic disorder and has destructive effects among all organs including cardiovascular system. Many studies revealed chronic renal failure (CRF) is associated with cardiovascular diseases (CVD) [1,2]. The complex association of CRF with CVD is probably due to clustering of several cardiovascular risk factors including the "traditional factors" such as age, hypertension (HT), diabetes mellitus (DM), and hyperlipidemia (HL) and "nontraditional factors" that are specifi c to CRF such as anemia, volume overload, mineral metabolism abnormalities, proteinuria, malnutrition, oxidative stress and infl ammation in CRF patients [3].
Acute or chronic renal failure which is characterised by elevated serum creatinine concentration or decreased glomerular fi ltration rate (GFR) level may be associated with an increased risk of mortality and morbidity for patients  [4]. In cardiac surgery patients, an increase 25% at the serum creatinine level results with a 15 fold increase at the risk of hospital mortality [5,6]. Thus, deciding the treatment and operative strategy for cardiovascular patients with concomitant CRFis crucial. Despite dialysis-dependent CRF patients have an increased morbidity and mortality risk after cardiac surgery, end-stage renal disease (ESRD) should not be considered as a contraindication to cardiac surgery or cardiopulmonary bypass (CPB) [7]. One of the main problem faced by cardiac surgeons is a lack of consensus on the diagnostic criteria for acute renal failure (ARF) and the optimal time to initiate dialysis theraphy. Currently there is neither consensus nor a guideline to recommend the use of prediction models for acute kidney injury after cardiac surgery in nondialysis dependent CRF patients.
ARF is a possible complication of cardiac surgery, and may develop in patients with CRF or normal renal functions preoperatively. Furthermore, ARF is associated with early and late mortality (up to 15-30% for dialysis non-dependent ARF and 60% for dialysis-dependent ARF), prolonged length of hospital and intensive care unit (ICU) stay, increased infective complications [8][9][10]. In the current literature, there are studies that compare ARF and dialysis dependent CRF patients or non renal failure and dialysis dependent CRF patients [11].
Nevertheless, we couldn't fi nd any study comparing dialysis dependent CRF and ARF on dialysis non-dependent CRF patients.
In this study, we aimed to investigate the postoperative course of acute on chronic renal failure (AonCRF) after cardiac surgery.Therefore, we evaluated the postoperative course by comparing mortality and morbidity parameters. Additionally, this study purposed to defi ne perioperative risk factors for predicting postoperative ARF development.

Renal failure defi nition
ARF was defi ned by using the Acute Kidney Injury Network (AKIN) stage 1-3 criteria -a x1.5 times or more increase in the serum creatinine and/or 25% or more decrease in estimated GFR, from preoperative to peak postoperative serum creatinine level. Preoperative and peak postoperative serum creatinine were defi ned as the creatinine values recorded within two week before the surgery and the highest creatinine level within 10 days after surgery, respectively [12].CRF was defi ned using the National Kidney Foundation Kidney Disease Outcome Quality Initative (NKF-K/DOQI) scale, which suggests estimated GFR below than 60 mL/min [13]. CPB time, number of proximal/distal anastomosis, lowest hematocrit ratio, MAP and body temparature were recorded. Necessity of ultrafi ltration/hemodialysis during CPB and/ or extracorporeal membran oxygenation (ECMO) were the other recorded variables. Postoperative data of patients such as mechanical ventilation time, length of ICU and hospital stay, drainage amount, necessity of transfusion of blood products, inotropic or mechanical support, cardiovertion and/ or antiarrhythmic medication and postoperative reexploration rates were recorded. All recorded preoperative, intraoperative and postoperative data were analyzed, and then a comparison of two groups was performed. Moreover, a cardiologist who was unaware of patients' groupdistribution,evaluated the postoperative daily electocardiograms of all patients. New developed branch blocks, disrythmias, conduction delays, ST depressions/elevations, pardee waves and pathologic Q waves, were considered as signifi cant electrocardiographic(ECG) changes.Mortality prevalances were classifi ed into 2 groups as early (in postoperative fi rst 30 days), andlate (duration between postoperative 30 th day and end of the follow up). Patients telephoned, mortality and medical status searched by questioning after discharged up to 5 years.

Statistical analysis
All statistical analyses were performed using Statistical Package for Social Sciences (SPSS) program (version 15.0, SPSS, Chicago, Illinois, USA).Continuous variables were expressed as mean ± standard deviation. Categorical variables were expressed as frequency and percentages. Differences between groups were analyzed by Fischer's exact test and Pearson's chi-square test for qualitative variables. Student T-test and Mann-Whitney U test werealso conducted out toanalyse the quantitative variables. Mortality rates were analyzed by using Kaplan Meier and log rank tests.A p value of <0.05 was considered as statistically signifi cant with a 95% confi dence interval.

Baseline characteristics and demographics
Preoperative clinical characteristics and demographics of patient groups were summarized in table 1. Basic demographic variables were not statistically signifi cantin both groups except gender, prevelance of DM and level of EuroSCORE. The proportion of female gender and prevelance of DM were higher in Group 2 than in Group 1.In addition to these differences, as expected, eGFR was also signifi cantly higher in Group 2. (mean eGFR was 11.65 in Group 1, while 43.85 in Group 2; p = 0.01). Preoperative level of EuroSCORE of patients were used in order to determine the risk scores of patients. Group 1 had signifi cantly higher risk score compared with Group 2 (p< 0.05). Preoperative medications were shown in table 2. The prevalence of use of preoperative oral antidiatebic and insulin therapy was higher in Group 2 (p=0.01).

Intra operative data
Intraoperative data of patient groups were listed in table 3. CABG was the most common surgery type for both groups.
However, there was not any signifi cant difference between the groups for neither surgery type nor surgical variables.

Post operative outcomes
Postoperativedata of patient groups were listed in table 4.
Various complication rates were found to be higher in Group 2 without statistical signifi cancy (p >0.05). However, positive inotropic necessity, signifi cant ECG changes, reintubation necessity and transfusion amounts were statistically higher in Group 2. Patients in Group 2 had a signifi cant longer ICU stay (mean length of ICU stay was 4 days in Group 1, while 6 days in Group 2, p = 0.01) and total hospital stay (mean length of total hospital stay was 9 days in Group 1, while 15 days in Group 2, p = 0.006). All of patients in Group 1 continued to their dialysis programmes after discharge, while 5 patients in Group 2 continued to dialysis (by questioning up to 5 years).
During a total follow-up period, there were 5 deaths (27.8%) in Group 1, and 9 deaths (37.5%) in Group 2. Cumulative survival     In some studies, a positive correlation between postoperative blood transfusion and drainage amount was reported [21][22][23]. Postoperative blood transfusion usage was reported 17% for no ARF group while33% for ARF stage 1 and 67% for stage 2-3 ARF group [22]. Another study also found out mean: 3.3± 4.6 units for ARF group comparing to mean: 1.4 ± 2.5 for no ARF group (p< 0.05). As corralated to higher usage of blood transfusion, ARF group's drainage were also reported higher for the fi rst 12 hours postoperatively [21]. In our study despite similar drainage amounts for both groups, we found significantly higher blood transfusion rates in Group 2.
Electrolit imbalance such as hyperkalemia is one of the most important reason for mortal arrythmias. Hyperkalemiainduced accelerated idioventricular arrythmias reported before [22]. Some other studies showed the association between increased prevalance of arrythmias of patients with ARF and acute coronary syndromes [24]. In our study, despite atrial hours follow-up of urine output less than 0.5 mL/kg/hour [26].
In our department, dialysis therapy has been starting after a nephrology consultation, without a strict value of urine output, volume overload, electrolit imbalances, etc.
As similar to our study, Bahar et