Predictors of long-term prognosis in acute kidney injury survivors who require continuous renal replacement therapy after cardiovascular surgery

RESEARCH ARTICLE Predictors of long-term prognosis in acute kidney injury survivors who require continuous renal replacement therapy after cardiovascular surgery Keita Sueyoshi1,2,3, Yusuke Watanabe1,2, Tsutomu Inoue1,2, Yoichi Ohno ID1,2, Hiroyuki Nakajima4, Hirokazu Okada ID1,2* 1 Department of Nephrology, Saitama Medical University, Saitama, Japan, 2 Division of Dialysis Center and Department of Nephrology, Saitama Medical University International Medical Center, Saitama, Japan, 3 Musashiranzan Hospital, Saitama, Japan, 4 Department of Cardiovascular Surgery, Saitama Medical University, International Medical Center, Saitama, Japan a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: Sueyoshi K, Watanabe Y, Inoue T, Ohno Y, Nakajima H, Okada H (2019) Predictors of longterm prognosis in acute kidney injury survivors who require continuous renal replacement therapy after cardiovascular surgery. PLoS ONE 14(1): e0211429. https://doi.org/10.1371/journal. pone.0211429 Editor: Emmanuel A. Burdmann, University of Sao Paulo Medical School, BRAZIL Received: September 13, 2018 Accepted: January 14, 2019 Published: January 31, 2019 Copyright: © 2019 Sueyoshi et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. * Abstract The long-term prognosis of patients with postoperative acute kidney injury (AKI) requiring continuous renal replacement therapy (CRRT) after cardiovascular surgery is unclear. We aimed to investigate long-term renal outcomes and survival in these patients to determine the risk factors for negative outcomes. Long-term prognosis was examined in 144 hospital survivors. All patients were independent and on renal replacement therapy at hospital discharge. The median age at operation was 72.0 years, and the median pre-operative estimated glomerular filtration rate (eGFR) was 39.5 mL/min/1.73 m2. The median follow-up duration was 1075 days. The endpoints were death, chronic maintenance dialysis dependence, and a composite of death and chronic dialysis. Predictors for death and dialysis were evaluated using Fine and Gray’s competing risk analysis. The cumulative incidence of death was 34.9%, and the chronic dialysis rate was 13.3% during the observation period. In the multivariate proportional hazards analysis, eGFR <30 mL/min/1.73 m2 at discharge was associated with the composite endpoint of death and dialysis [hazard ratio (HR), 2.1; 95% confidence interval (CI), 1.1–3.8; P = 0.02]. Hypertension (HR 8.7, 95% CI, 2.2–35.4; P = 0.002) and eGFR <30 mL/min/1.73 m2 at discharge (HR 26.4, 95% CI, 2.6–267.1; P = 0.006) were associated with dialysis. Advanced age (�75 years) was predictive of death. Patients with severe CRRT-requiring AKI after cardiovascular surgery have increased risks of chronic dialysis and death. Patients with eGFR <30 mL/min/1.73 m2 at discharge should be monitored especially carefully by nephrologists due to the risk of chronic dialysis and death. Data Availability Statement: All relevant data are within the manuscript. Funding: The authors received no specific funding for this work. Competing interests: The authors have declared that no competing interests exist. PLOS ONE | https://doi.org/10.1371/journal.pone.0211429 January 31, 2019 1 / 16 Long-term prognosis in AKI survivors required CRRT Introduction Acute kidney injury (AKI) is a common and serious complication in hospitalized patients that increases short-term mortality [1, 2]. Patients with severe forms of AKI need acute dialysis, and the incidence of dialysis-requiring AKI (AKI-D) in the United States has increased rapidly in the past decades [3]. In recent years, several observational studies have reported that patients who survive after AKI are more likely to develop chronic kidney disease (CKD) and end-stage renal disease (ESRD), and have higher long-term mortality than patients without AKI [4–6]. Cardiovascular surgery is also associated with a high risk of postoperative AKI, which leads to poor short-term and long-term prognoses [7]. In the most severe AKI cases, continuous renal replacement therapy (CRRT) is performed if the patients’ hemodynamics are unstable. Cardiovascular surgery is a major cause of CRRT-requiring AKI [8]. However, reports of the longterm prognoses of patients who develop postoperative AKI and receive CRRT after cardiovascular surgery are scarce [9, 10]. Here, we report the long-term outcomes and renal prognoses of patients who developed postoperative AKI and required CRRT after cardiovascular surgery. Furthermore, we investigate the risk factors for death and chronic dialysis dependence using competing risks methods. Materials and methods Study population and data collection A retrospective cohort study was performed at an academic hospital (Saitama Medical University International Medical Center, Japan). Patients who underwent cardiovascular surgery and developed severe AKI requiring CRRT between April 2007 and December 2014 were identified using records from the dialysis center. Patients who underwent renal replacement therapy (RRT) or kidney transplantation before admission were excluded. Individual medical records were reviewed and the following pre-operative clinical and demographic data were collected: age, sex, body weight, body mass index (BMI), serum creatinine (sCr), albumin, hemoglobin, Charlson comorbidity index (CCI) score, and presence or absence of diabetes mellitus and hypertension. The CCI score is a well validated method for estimating the risk of death from comorbid disease and has been used in previous multiple studies [11]. The variables that comprise the CCI score include myocardial infarction, congestive heart failure, peripheral vascular disease, and cerebrovascular disease. Each comorbid disease included in the CCI is assigned a score of 1, 2, 3, or 6 depending on the risk of death associated with each comorbid disease. The individual scores are summed to calculate a total comorbidity score for the prediction of mortality. Pre-operative sCr level was defined as the last recorded sCr value within 1 week before surgery. Estimated glomerular filtration rate (eGFR) was calculated using the formula for Japanese patients [12]: eGFR (mL/min/1.73 m2) = 194×sCr−1.094×age−0.287 (×0.739 for females). Peri-operative data included the need for emergency surgery, operation type (coronary artery bypass grafting [CABG], valve surgery, CABG combined with valve surgery, vascular surgery, and others), and the use and duration of cardio-pulmonary bypass. AKI was diagnosed according to the Kidney Disease Improving Global Outcomes (KDIGO) criteria [13]. In brief, diagnosis was based on an increase in sCr of �0.3 mg/dL within 48 hours, an increase in sCr to �1.5-times the baseline known or presumed to have occurred within the prior 7 (...truncated)