Surgical and early outcomes for Type A aortic dissection with preoperative renal dysfunction stratified by estimated glomerular filtration rate

Surgical and early outcomes for Type A aortic dissection with preoperative renal dysfunction... Abstract OBJECTIVES The aim of this study was to analyse the effect of preoperative renal dysfunction on surgical and early outcomes for patients with Type A aortic dissection (AAD). METHODS From January 2016 to December 2016, 140 patients with AAD who underwent surgical treatment at our institution were retrospectively analysed. According to the estimated glomerular filtration rate (eGFR), preoperative renal dysfunction was divided into 4 groups: normal (eGFR ≥90 ml/min/1.73 m2, n = 76), mild (eGFR 60–89, n = 40), moderate (eGFR 30–59, n = 20) and severe (eGFR <30, n = 4). RESULTS Major complications included prolonged ventilation requiring tracheotomy in 15 patients, renal replacement therapy (RRT) in 28 patients, stroke in 11 patients and paraplegia in 4 patients. The best cut-off value of the eGFR for predicting postoperative RRT was 70 ml/min/1.73 m2 (area under the receiver operating characteristic curve was 0.809). In-hospital mortality was 9.3% (6.5% in the normal group, 5% in the mild group, 20% in the moderate group and 50% in the severe group). Logistic regression analysis showed that age >60 years, moderate and severe renal dysfunction, coronary malperfusion and peripheral malperfusion were risk factors for in-hospital death. CONCLUSIONS Total arch replacement can be safely performed in patients with AAD and preoperative mild renal dysfunction. Preoperative renal dysfunction is a risk factor for postoperative RRT, and eGFR is useful for predicting the requirement for postoperative RRT. Our surgical strategy for total arch replacement and stented elephant trunk for patients with AAD and mild preoperative renal dysfunction has excellent early outcomes. Renal dysfunction, Estimated glomerular filtration rate, Type A aortic dissection, Renal replacement therapy INTRODUCTION Renal dysfunction is associated with high complication rates and mortality in patients undergoing elective cardiac surgery including coronary artery bypass grafting (CABG) and aortic valve replacement [1, 2]. However, studies concerning the effect of preoperative renal function on early outcomes after surgery for Type A aortic dissection (AAD) are limited. AAD remains a life-threatening situation requiring surgical intervention. Although diagnostics and surgical techniques have substantially improved, morbidity and mortality remain high [3]. Various risk factors, including preoperative renal dysfunction, have been identified for in-hospital death by previous studies [4, 5]. Additionally, the incidence of renal dysfunction after aortic surgery is high and associated with increased early and long-term mortality [5–7]. Therefore, determining the risk factors for postoperative renal dysfunction and in-hospital death is important. Total arch replacement (TAR) combined with stented elephant trunk (SET) implantation is associated with encouraging surgical results and promising outcomes [8, 9]. However, preoperative renal dysfunction was reported to be a strong predictor of worse outcomes after TAR [10]. The requirement for hypothermic circulatory arrest, which may increase the incidence of severe complications, has caused doubt on the safety of this procedure for patients with preoperative renal dysfunction. TAR combined with SET implantation is the primary surgical strategy for most patients with AAD at our institution. The aim of this study was to determine the risk factors for postoperative renal replacement therapy (RRT) and in-hospital mortality after surgery for AAD. We also evaluated the effect of preoperative renal dysfunction on in-hospital and early outcomes. MATERIALS AND METHODS Study population From January 2016 to December 2016, patients who underwent surgical treatment for AAD at our institution were retrospectively reviewed. We excluded patients who underwent an open heart operation previously, and 140 patients were included in this study. The diagnosis of AAD was confirmed using computed tomography angiography (CTA). Dissection was considered acute if it was surgically treated within 2 weeks from the onset of symptoms (126 patients). Fourteen patients who were surgically treated after 2 weeks from the onset of symptoms were considered chronic dissections. The average interval between diagnosis of dissection at our institution and surgical treatment for the whole cohort was 30.3 ± 47.7 h. The study protocol was approved by the Ethics Committee of Zhongshan Hospital of Fudan University and was conducted in accordance with the Declaration of Helsinki. Informed consent was obtained from each patient involved in this study. The glomerular filtration rate at the time of admission was used to assess renal function [11, 12]. In this study, the glomerular filtration rate was estimated from the Chronic Kidney Disease Epidemiology Collaboration equation [13]. According to the estimated glomerular filtration rate (eGFR), preoperative renal function was classified into 4 categories: the normal group (eGFR >90 ml/min/1.73 m2, 76 patients), the mild group (eGFR 60–90 ml/min/1.73 m2, 40 patients), the moderate group (eGFR 30–60 ml/min/1.73 m2, 20 patients) and the severe group (eGFR <30 ml/min/1.73 m2, 4 patients). Preoperative profiles, operative data and postoperative results were retrospectively reviewed and analysed. In-hospital mortality was defined as death occurred during hospital stay or 30 days postoperatively. The indications for postoperative RRT included fluid overload, acidosis and electrolyte disturbances. Operative technique All operations were performed through midline sternotomy. Surgical techniques included TAR in 122 (87%) patients and SET implantation in 115 (82%) patients. Additionally, the Bentall procedure was performed in 25 (18%) patients, David I in 6 (4%) patients and CABG in 6 (4%) patients. TAR combined with SET implantation under circulatory arrest was our primary surgical strategy. For patients who previously underwent thoracic endovascular aortic repair, isolated TAR was performed. For patients with dissection restricted to the ascending aorta, ascending aorta replacement with or without the Bentall procedure was performed. Circulatory arrest was not required in these patients. Standard transcutaneous cerebral oximetry monitoring and transoesophageal echocardiography were applied in all cases. Arterial cannulation sites were the femoral artery and right axillary artery in patients who required circulatory arrest. The femoral artery and right atrial appendage were cannulated for cardiopulmonary bypass. If circulatory arrest was required, surgery was performed with protection of the brain by unilateral selective cerebral perfusion through the right axillary artery. This perfusion was maintained at a perfusion rate of 10 ml/kg/min. Moderate-to-deep hypothermia with a temperature of 22–23°C for the nasopharynx and 25–28°C for the bladder was applied during circulatory arrest. The heart was arrested with cold blood cardioplegia infusing into the coronary ostia after aortic cross-clamping. Retrograde infusion of cardioplegia through the coronary sinus was performed to enhance myocardial protection. A 4-branch prosthetic graft with or without SET implantation was used in TAR. Open distal anastomosis was first completed, and the 4-branch prosthetic graft was cross-clamped. Blood perfusion of the lower body was then started via femoral artery cannulation. Anastomosis of the left common carotid artery, left subclavian artery and innominate artery was completed. After completing anastomosis of the left common carotid artery, bilateral cerebral perfusion and full cardiopulmonary bypass flow were resumed. The Bentall or David I procedure was performed accordingly during the rewarming period. Finally, proximal anastomosis was completed. For patients with severe coronary malperfusion, emergent CABG was performed, and for patients with severe lower limb malperfusion, distal revascularization (the aortic arch-femoral bypass in 4 patients, ascending aorta-femoral bypass in 1 patient, ascending iliac bypass in 1 patient and descending iliac bypass in 1 patient) was performed. Statistical analysis Continuous variables are expressed as mean ± standard deviation, and categorical variables as counts and percentages. One-way analysis of variance and the χ2 test or Fisher’s exact test were used to compare continuous and categorical variables, respectively. For abnormally distributed variables, the Kruskal–Wallis test was used to compare the differences. Logistic regression models were used to identify univariable and multivariable predictors for postoperative RRT and in-hospital mortality. In the logistic regression analysis, potential predictors of in-hospital death and postoperative need for RRT were tested in a univariable fashion, and variables with P-value <0.1 were included into the multivariable analysis. The results of the logistic regression analysis are presented as odds ratios with the corresponding 95% confidence intervals (CIs). Calculation of the area under the receiver operating characteristic curve with a 95% CI was used to assess the most clinically useful level of the eGFR for predicting the requirement for postoperative RRT. Cut-off values for the highest sensitivity and specificity were identified. A P-value <0.05 was considered statistically significant. All statistical analyses were conducted using the SPSS software (Version 22.0. IBM Corp., Armonk, NY, USA). RESULTS Demographic characteristics and surgical details are shown in Table 1. In addition to the eGFR, significant differences were observed in malperfusion syndrome (P = 0.02) and previous chronic kidney disease (P = 0.003) among all of the preoperative demographic characteristics. Table 1: Demographic characteristics and surgical details Variables  Total (n = 140)  Normal group (n = 76)  Mild group (n = 40)  Moderate group (n = 20)  Severe group (n = 4)  P-value  Male, n (%)  107 (76.4)  57 (75)  31 (77.5)  16 (80)  3 (75)  0.97  Age (years), mean ± SD  51.4 ± 12.7  48.9 ± 13.2  54.7 ± 12.2  53.8 ± 11.2  53.8 ± 6.7  0.09  Marfan syndrome, n (%)  19 (13.6)  13 (17.1)  5 (12.5)  1 (5)  0  0.19  Hypertension, n (%)  94 (67.1)  46 (60.5)  28 (70)  16 (80)  4 (100)  0.09  Diabetes, n (%)  3 (2.1)  0 (0)  2 (5)  0  1 (25)  0.04  Stroke, n (%)  11 (7.9)  2 (2.6)  7 (17.5)  2 (10)  0  0.04  Chronic kidney disease, n (%)  5 (3.6)  0  1 (2.5)  2 (10)  2 (50)  0.003  eGFR (ml/min/1.73 m2), mean ± SD  85.1 ± 26.5  105 ± 9.7  76.3 ± 8.6  46.9 ± 9.4  10 ± 8.3  <0.001  Malperfusion syndrome, n (%)  35 (25)  16 (21.1)  7 (17.5)  11 (55)  1 (25)  0.02   Cerebral or spinal, n (%)  13 (9.3)  7 (9.2)  4 (10)  1 (5)  1 (25)  0.71   Coronary, n (%)  5 (3.6)  2 (2.6)  1 (2.5)  1 (5)  1 (25)  0.42   Peripheral, n (%)  18 (12.9)  7 (9.2)  2 (5)  9 (45)  0  0.001   Bowel, n (%)  3 (2.1)  1 (1.3)  1 (2.5)  0  1 (25)  0.21  Emergency operation, n (%)  126 (90)  68 (89.5)  36 (90)  18 (90)  4 (100)  0.83  Previous TEVAR, n (%)  8 (5.7)  3 (3.9)  5 (12.5)  0  0  0.12  Total arch replacement, n (%)  122 (87.1)  64 (84.2)  37 (92.5)  20 (100)  1 (25)  0.002  Hemiarch replacement, n (%)  10 (7.1)  6 (7.9)  1 (2.5)  0  3 (75)  0.001  Stented elephant trunk, n (%)  115 (82.1)  61 (80.3)  33 (82.5)  20 (100)  1 (25)  0.002  Bentall procedure, n (%)  25 (17.9)  19 (25)  6 (15)  0  0  0.02  David I procedure, n (%)  6 (4.3)  4 (5.3)  1 (2.5)  1 (5)  0  0.83  CABG, n (%)  6 (4.3)  3 (3.9)  0  2 (10)  1 (25)  0.08  Circulatory arrest, n (%)  132 (94.3)  70 (92.1)  38 (95)  20 (100)  4 (100)  0.33  Circulatory arrest time (min), mean ± SD  27 ± 9  27 ± 8  29 ± 13  28 ± 7  30 ± 11  0.64  CPB time (min), mean ± SD  199 ± 47  198 ± 49  196 ± 29  204 ± 52  205 ± 56  0.95  Aorta cross-clamp time (min), mean ± SD  113 ± 34  115 ± 36  107 ± 29  109 ± 29  115 ± 38  0.78  Variables  Total (n = 140)  Normal group (n = 76)  Mild group (n = 40)  Moderate group (n = 20)  Severe group (n = 4)  P-value  Male, n (%)  107 (76.4)  57 (75)  31 (77.5)  16 (80)  3 (75)  0.97  Age (years), mean ± SD  51.4 ± 12.7  48.9 ± 13.2  54.7 ± 12.2  53.8 ± 11.2  53.8 ± 6.7  0.09  Marfan syndrome, n (%)  19 (13.6)  13 (17.1)  5 (12.5)  1 (5)  0  0.19  Hypertension, n (%)  94 (67.1)  46 (60.5)  28 (70)  16 (80)  4 (100)  0.09  Diabetes, n (%)  3 (2.1)  0 (0)  2 (5)  0  1 (25)  0.04  Stroke, n (%)  11 (7.9)  2 (2.6)  7 (17.5)  2 (10)  0  0.04  Chronic kidney disease, n (%)  5 (3.6)  0  1 (2.5)  2 (10)  2 (50)  0.003  eGFR (ml/min/1.73 m2), mean ± SD  85.1 ± 26.5  105 ± 9.7  76.3 ± 8.6  46.9 ± 9.4  10 ± 8.3  <0.001  Malperfusion syndrome, n (%)  35 (25)  16 (21.1)  7 (17.5)  11 (55)  1 (25)  0.02   Cerebral or spinal, n (%)  13 (9.3)  7 (9.2)  4 (10)  1 (5)  1 (25)  0.71   Coronary, n (%)  5 (3.6)  2 (2.6)  1 (2.5)  1 (5)  1 (25)  0.42   Peripheral, n (%)  18 (12.9)  7 (9.2)  2 (5)  9 (45)  0  0.001   Bowel, n (%)  3 (2.1)  1 (1.3)  1 (2.5)  0  1 (25)  0.21  Emergency operation, n (%)  126 (90)  68 (89.5)  36 (90)  18 (90)  4 (100)  0.83  Previous TEVAR, n (%)  8 (5.7)  3 (3.9)  5 (12.5)  0  0  0.12  Total arch replacement, n (%)  122 (87.1)  64 (84.2)  37 (92.5)  20 (100)  1 (25)  0.002  Hemiarch replacement, n (%)  10 (7.1)  6 (7.9)  1 (2.5)  0  3 (75)  0.001  Stented elephant trunk, n (%)  115 (82.1)  61 (80.3)  33 (82.5)  20 (100)  1 (25)  0.002  Bentall procedure, n (%)  25 (17.9)  19 (25)  6 (15)  0  0  0.02  David I procedure, n (%)  6 (4.3)  4 (5.3)  1 (2.5)  1 (5)  0  0.83  CABG, n (%)  6 (4.3)  3 (3.9)  0  2 (10)  1 (25)  0.08  Circulatory arrest, n (%)  132 (94.3)  70 (92.1)  38 (95)  20 (100)  4 (100)  0.33  Circulatory arrest time (min), mean ± SD  27 ± 9  27 ± 8  29 ± 13  28 ± 7  30 ± 11  0.64  CPB time (min), mean ± SD  199 ± 47  198 ± 49  196 ± 29  204 ± 52  205 ± 56  0.95  Aorta cross-clamp time (min), mean ± SD  113 ± 34  115 ± 36  107 ± 29  109 ± 29  115 ± 38  0.78  CABG: coronary artery bypass grafting; CPB: cardiopulmonary bypass; eGFR: estimated glomerular filtration rate; SD: standard deviation; TEVAR: thoracic endovascular repair. Table 1: Demographic characteristics and surgical details Variables  Total (n = 140)  Normal group (n = 76)  Mild group (n = 40)  Moderate group (n = 20)  Severe group (n = 4)  P-value  Male, n (%)  107 (76.4)  57 (75)  31 (77.5)  16 (80)  3 (75)  0.97  Age (years), mean ± SD  51.4 ± 12.7  48.9 ± 13.2  54.7 ± 12.2  53.8 ± 11.2  53.8 ± 6.7  0.09  Marfan syndrome, n (%)  19 (13.6)  13 (17.1)  5 (12.5)  1 (5)  0  0.19  Hypertension, n (%)  94 (67.1)  46 (60.5)  28 (70)  16 (80)  4 (100)  0.09  Diabetes, n (%)  3 (2.1)  0 (0)  2 (5)  0  1 (25)  0.04  Stroke, n (%)  11 (7.9)  2 (2.6)  7 (17.5)  2 (10)  0  0.04  Chronic kidney disease, n (%)  5 (3.6)  0  1 (2.5)  2 (10)  2 (50)  0.003  eGFR (ml/min/1.73 m2), mean ± SD  85.1 ± 26.5  105 ± 9.7  76.3 ± 8.6  46.9 ± 9.4  10 ± 8.3  <0.001  Malperfusion syndrome, n (%)  35 (25)  16 (21.1)  7 (17.5)  11 (55)  1 (25)  0.02   Cerebral or spinal, n (%)  13 (9.3)  7 (9.2)  4 (10)  1 (5)  1 (25)  0.71   Coronary, n (%)  5 (3.6)  2 (2.6)  1 (2.5)  1 (5)  1 (25)  0.42   Peripheral, n (%)  18 (12.9)  7 (9.2)  2 (5)  9 (45)  0  0.001   Bowel, n (%)  3 (2.1)  1 (1.3)  1 (2.5)  0  1 (25)  0.21  Emergency operation, n (%)  126 (90)  68 (89.5)  36 (90)  18 (90)  4 (100)  0.83  Previous TEVAR, n (%)  8 (5.7)  3 (3.9)  5 (12.5)  0  0  0.12  Total arch replacement, n (%)  122 (87.1)  64 (84.2)  37 (92.5)  20 (100)  1 (25)  0.002  Hemiarch replacement, n (%)  10 (7.1)  6 (7.9)  1 (2.5)  0  3 (75)  0.001  Stented elephant trunk, n (%)  115 (82.1)  61 (80.3)  33 (82.5)  20 (100)  1 (25)  0.002  Bentall procedure, n (%)  25 (17.9)  19 (25)  6 (15)  0  0  0.02  David I procedure, n (%)  6 (4.3)  4 (5.3)  1 (2.5)  1 (5)  0  0.83  CABG, n (%)  6 (4.3)  3 (3.9)  0  2 (10)  1 (25)  0.08  Circulatory arrest, n (%)  132 (94.3)  70 (92.1)  38 (95)  20 (100)  4 (100)  0.33  Circulatory arrest time (min), mean ± SD  27 ± 9  27 ± 8  29 ± 13  28 ± 7  30 ± 11  0.64  CPB time (min), mean ± SD  199 ± 47  198 ± 49  196 ± 29  204 ± 52  205 ± 56  0.95  Aorta cross-clamp time (min), mean ± SD  113 ± 34  115 ± 36  107 ± 29  109 ± 29  115 ± 38  0.78  Variables  Total (n = 140)  Normal group (n = 76)  Mild group (n = 40)  Moderate group (n = 20)  Severe group (n = 4)  P-value  Male, n (%)  107 (76.4)  57 (75)  31 (77.5)  16 (80)  3 (75)  0.97  Age (years), mean ± SD  51.4 ± 12.7  48.9 ± 13.2  54.7 ± 12.2  53.8 ± 11.2  53.8 ± 6.7  0.09  Marfan syndrome, n (%)  19 (13.6)  13 (17.1)  5 (12.5)  1 (5)  0  0.19  Hypertension, n (%)  94 (67.1)  46 (60.5)  28 (70)  16 (80)  4 (100)  0.09  Diabetes, n (%)  3 (2.1)  0 (0)  2 (5)  0  1 (25)  0.04  Stroke, n (%)  11 (7.9)  2 (2.6)  7 (17.5)  2 (10)  0  0.04  Chronic kidney disease, n (%)  5 (3.6)  0  1 (2.5)  2 (10)  2 (50)  0.003  eGFR (ml/min/1.73 m2), mean ± SD  85.1 ± 26.5  105 ± 9.7  76.3 ± 8.6  46.9 ± 9.4  10 ± 8.3  <0.001  Malperfusion syndrome, n (%)  35 (25)  16 (21.1)  7 (17.5)  11 (55)  1 (25)  0.02   Cerebral or spinal, n (%)  13 (9.3)  7 (9.2)  4 (10)  1 (5)  1 (25)  0.71   Coronary, n (%)  5 (3.6)  2 (2.6)  1 (2.5)  1 (5)  1 (25)  0.42   Peripheral, n (%)  18 (12.9)  7 (9.2)  2 (5)  9 (45)  0  0.001   Bowel, n (%)  3 (2.1)  1 (1.3)  1 (2.5)  0  1 (25)  0.21  Emergency operation, n (%)  126 (90)  68 (89.5)  36 (90)  18 (90)  4 (100)  0.83  Previous TEVAR, n (%)  8 (5.7)  3 (3.9)  5 (12.5)  0  0  0.12  Total arch replacement, n (%)  122 (87.1)  64 (84.2)  37 (92.5)  20 (100)  1 (25)  0.002  Hemiarch replacement, n (%)  10 (7.1)  6 (7.9)  1 (2.5)  0  3 (75)  0.001  Stented elephant trunk, n (%)  115 (82.1)  61 (80.3)  33 (82.5)  20 (100)  1 (25)  0.002  Bentall procedure, n (%)  25 (17.9)  19 (25)  6 (15)  0  0  0.02  David I procedure, n (%)  6 (4.3)  4 (5.3)  1 (2.5)  1 (5)  0  0.83  CABG, n (%)  6 (4.3)  3 (3.9)  0  2 (10)  1 (25)  0.08  Circulatory arrest, n (%)  132 (94.3)  70 (92.1)  38 (95)  20 (100)  4 (100)  0.33  Circulatory arrest time (min), mean ± SD  27 ± 9  27 ± 8  29 ± 13  28 ± 7  30 ± 11  0.64  CPB time (min), mean ± SD  199 ± 47  198 ± 49  196 ± 29  204 ± 52  205 ± 56  0.95  Aorta cross-clamp time (min), mean ± SD  113 ± 34  115 ± 36  107 ± 29  109 ± 29  115 ± 38  0.78  CABG: coronary artery bypass grafting; CPB: cardiopulmonary bypass; eGFR: estimated glomerular filtration rate; SD: standard deviation; TEVAR: thoracic endovascular repair. With regard to surgical details, the Bentall procedure was mainly practiced in patients with normal renal function and mild renal dysfunction. Hemiarch replacement was performed in 75% (3 of 4) of the patients in the severe group. In the other 3 groups, TAR was the primary procedure. Circulatory arrest was used in most of the patients among the groups. Perioperative data are presented in Table 2. In-hospital mortality was 9.3% (13 of 140). Two patients with severe renal dysfunction required preoperative RRT. Major complications included prolonged ventilation requiring tracheotomy in 15 (10.7%) patients, RRT in 28 (20%) patients and central nervous system complications in 18 patients (12.8%, brain injury in 14 patients and spinal cord injury in 4 patients). Table 2: Postoperative complications and in-hospital mortality Variables  Total (n = 140)  Normal group (n = 76)  Mild group (n = 40)  Moderate group (n = 20)  Severe group (n = 4)  P-value  Low cardiac output syndrome, n (%)  6 (4.3)  3 (3.9)  2 (5)  1 (5)  0  0.93  Postoperative stroke, n (%)  11 (7.9)  6 (7.9)  1 (2.5)  4 (20)  0  0.13  Hypoxia, n (%)  27 (19.3)  13 (17.1)  8 (20)  5 (25)  1 (25)  0.87  Prolonged ventilation requiring tracheotomy, n (%)  15 (10.7)  7 (9.2)  3 (7.5)  4 (20)  1 (25)  0.43  RRT, n (%)  28 (20)  7 (9.2)  6 (15)  11 (55)  4 (100)  <0.001a  Intensive care time (days), mean ± SD  8.2 ± 14  8 ± 15.9  6.3 ± 8  12.1 ± 15.9  12.1 ± 14.7  0.46  In-hospital mortality, n (%)  13 (9.3)  5 (6.6)  2 (5)  4 (20)  2 (50)  0.007  Variables  Total (n = 140)  Normal group (n = 76)  Mild group (n = 40)  Moderate group (n = 20)  Severe group (n = 4)  P-value  Low cardiac output syndrome, n (%)  6 (4.3)  3 (3.9)  2 (5)  1 (5)  0  0.93  Postoperative stroke, n (%)  11 (7.9)  6 (7.9)  1 (2.5)  4 (20)  0  0.13  Hypoxia, n (%)  27 (19.3)  13 (17.1)  8 (20)  5 (25)  1 (25)  0.87  Prolonged ventilation requiring tracheotomy, n (%)  15 (10.7)  7 (9.2)  3 (7.5)  4 (20)  1 (25)  0.43  RRT, n (%)  28 (20)  7 (9.2)  6 (15)  11 (55)  4 (100)  <0.001a  Intensive care time (days), mean ± SD  8.2 ± 14  8 ± 15.9  6.3 ± 8  12.1 ± 15.9  12.1 ± 14.7  0.46  In-hospital mortality, n (%)  13 (9.3)  5 (6.6)  2 (5)  4 (20)  2 (50)  0.007  a Compared between groups: the normal group versus the mild group, P = 0.22; the normal group versus the moderate group, P < 0.001; the normal group versus the severe group, P < 0.001; the mild group versus the moderate group, P = 0.03; the mild group versus the severe group, P = 0.02; the moderate group versus the severe group, P = 0.3. RRT: renal replacement therapy; SD: standard deviation. Table 2: Postoperative complications and in-hospital mortality Variables  Total (n = 140)  Normal group (n = 76)  Mild group (n = 40)  Moderate group (n = 20)  Severe group (n = 4)  P-value  Low cardiac output syndrome, n (%)  6 (4.3)  3 (3.9)  2 (5)  1 (5)  0  0.93  Postoperative stroke, n (%)  11 (7.9)  6 (7.9)  1 (2.5)  4 (20)  0  0.13  Hypoxia, n (%)  27 (19.3)  13 (17.1)  8 (20)  5 (25)  1 (25)  0.87  Prolonged ventilation requiring tracheotomy, n (%)  15 (10.7)  7 (9.2)  3 (7.5)  4 (20)  1 (25)  0.43  RRT, n (%)  28 (20)  7 (9.2)  6 (15)  11 (55)  4 (100)  <0.001a  Intensive care time (days), mean ± SD  8.2 ± 14  8 ± 15.9  6.3 ± 8  12.1 ± 15.9  12.1 ± 14.7  0.46  In-hospital mortality, n (%)  13 (9.3)  5 (6.6)  2 (5)  4 (20)  2 (50)  0.007  Variables  Total (n = 140)  Normal group (n = 76)  Mild group (n = 40)  Moderate group (n = 20)  Severe group (n = 4)  P-value  Low cardiac output syndrome, n (%)  6 (4.3)  3 (3.9)  2 (5)  1 (5)  0  0.93  Postoperative stroke, n (%)  11 (7.9)  6 (7.9)  1 (2.5)  4 (20)  0  0.13  Hypoxia, n (%)  27 (19.3)  13 (17.1)  8 (20)  5 (25)  1 (25)  0.87  Prolonged ventilation requiring tracheotomy, n (%)  15 (10.7)  7 (9.2)  3 (7.5)  4 (20)  1 (25)  0.43  RRT, n (%)  28 (20)  7 (9.2)  6 (15)  11 (55)  4 (100)  <0.001a  Intensive care time (days), mean ± SD  8.2 ± 14  8 ± 15.9  6.3 ± 8  12.1 ± 15.9  12.1 ± 14.7  0.46  In-hospital mortality, n (%)  13 (9.3)  5 (6.6)  2 (5)  4 (20)  2 (50)  0.007  a Compared between groups: the normal group versus the mild group, P = 0.22; the normal group versus the moderate group, P < 0.001; the normal group versus the severe group, P < 0.001; the mild group versus the moderate group, P = 0.03; the mild group versus the severe group, P = 0.02; the moderate group versus the severe group, P = 0.3. RRT: renal replacement therapy; SD: standard deviation. Differences in clinical and surgical details are shown in Table 3 between patients who required postoperative RRT and those who did not require RRT. An increased stage of preoperative renal dysfunction was an independent risk factor of postoperative RRT (odds ratio 4.4, 95% CI 2.5–7.8; P < 0.001). After further examination, we found that there was no statistically significant difference in the incidence of postoperative RRT between the mild and normal groups (P > 0.05). Moderate and severe renal dysfunction was associated with an increased incidence of postoperative RRT. In receiver operating characteristic curve analysis for the ability of preoperative eGFR to predict postoperative RRT, the area under the curve was 0.809 (95% CI 0.718–0.900) as presented in Fig. 1. A cut-off value of 70 ml/min/1.73 m2 was the most useful in predicting the requirement for postoperative RRT. Table 3: Differences in preoperative and operative details between patients with and without postoperative RRT Variables  No RRT (n = 112)  RRT (n = 28)  P-value  Male, n (%)  82 (73.2)  25 (89.3)  0.07  Age (years), mean ± SD  50.5 ± 13.2  55 ± 12.7  0.1  Marfan syndrome, n (%)  19 (17)  0  0.04  Hypertension, n (%)  71 (63.4)  23 (82.1)  0.06  Diabetes, n (%)  2 (1.8)  1 (3.6)  1  Stroke, n (%)  8 (7.1)  3 (10.7)  0.81  Chronic kidney disease, n (%)  2 (1.8)  3 (10.7)  0.09  eGFR (ml/min/1.73 m2), mean ± SD  91.9 ± 20.8  59.1 ± 30.2  <0.001  Malperfusion syndrome, n (%)  22 (19.6)  13 (46.4)  0.003  Emergency operation, n (%)  98 (87.5)  28 (100)  0.11  Previous TEVAR, n (%)  8 (7.1)  0  0.32  Total arch replacement, n (%)  98 (87.5)  24 (85.7)  1  Hemiarch replacement, n (%)  6 (5.4)  4 (14.3)  0.22  Stented elephant trunk, n (%)  92 (82.1)  24 (85.7)  0.87  Bentall procedure, n (%)  22 (19.6)  3 (10.7)  0.27  David I procedure, n (%)  6 (5.4)  0  0.47  CABG, n (%)  5 (4.5)  1 (3.6)  1  Circulatory arrest, n (%)  104 (92.9)  28 (100)  0.32  Circulatory arrest time (min), mean ± SD  27 ± 9  29 ± 9  0.36  CPB time (min), mean ± SD  199 ± 50  197 ± 36  0.82  Aorta cross-clamp time (min), mean ± SD  114 ± 36  108 ± 23  0.37  Variables  No RRT (n = 112)  RRT (n = 28)  P-value  Male, n (%)  82 (73.2)  25 (89.3)  0.07  Age (years), mean ± SD  50.5 ± 13.2  55 ± 12.7  0.1  Marfan syndrome, n (%)  19 (17)  0  0.04  Hypertension, n (%)  71 (63.4)  23 (82.1)  0.06  Diabetes, n (%)  2 (1.8)  1 (3.6)  1  Stroke, n (%)  8 (7.1)  3 (10.7)  0.81  Chronic kidney disease, n (%)  2 (1.8)  3 (10.7)  0.09  eGFR (ml/min/1.73 m2), mean ± SD  91.9 ± 20.8  59.1 ± 30.2  <0.001  Malperfusion syndrome, n (%)  22 (19.6)  13 (46.4)  0.003  Emergency operation, n (%)  98 (87.5)  28 (100)  0.11  Previous TEVAR, n (%)  8 (7.1)  0  0.32  Total arch replacement, n (%)  98 (87.5)  24 (85.7)  1  Hemiarch replacement, n (%)  6 (5.4)  4 (14.3)  0.22  Stented elephant trunk, n (%)  92 (82.1)  24 (85.7)  0.87  Bentall procedure, n (%)  22 (19.6)  3 (10.7)  0.27  David I procedure, n (%)  6 (5.4)  0  0.47  CABG, n (%)  5 (4.5)  1 (3.6)  1  Circulatory arrest, n (%)  104 (92.9)  28 (100)  0.32  Circulatory arrest time (min), mean ± SD  27 ± 9  29 ± 9  0.36  CPB time (min), mean ± SD  199 ± 50  197 ± 36  0.82  Aorta cross-clamp time (min), mean ± SD  114 ± 36  108 ± 23  0.37  CABG: coronary artery bypass grafting; CPB: cardiopulmonary bypass; eGFR: estimated glomerular filtration rate; RRT: renal replacement therapy; SD: standard deviation; TEVAR: thoracic endovascular repair. Table 3: Differences in preoperative and operative details between patients with and without postoperative RRT Variables  No RRT (n = 112)  RRT (n = 28)  P-value  Male, n (%)  82 (73.2)  25 (89.3)  0.07  Age (years), mean ± SD  50.5 ± 13.2  55 ± 12.7  0.1  Marfan syndrome, n (%)  19 (17)  0  0.04  Hypertension, n (%)  71 (63.4)  23 (82.1)  0.06  Diabetes, n (%)  2 (1.8)  1 (3.6)  1  Stroke, n (%)  8 (7.1)  3 (10.7)  0.81  Chronic kidney disease, n (%)  2 (1.8)  3 (10.7)  0.09  eGFR (ml/min/1.73 m2), mean ± SD  91.9 ± 20.8  59.1 ± 30.2  <0.001  Malperfusion syndrome, n (%)  22 (19.6)  13 (46.4)  0.003  Emergency operation, n (%)  98 (87.5)  28 (100)  0.11  Previous TEVAR, n (%)  8 (7.1)  0  0.32  Total arch replacement, n (%)  98 (87.5)  24 (85.7)  1  Hemiarch replacement, n (%)  6 (5.4)  4 (14.3)  0.22  Stented elephant trunk, n (%)  92 (82.1)  24 (85.7)  0.87  Bentall procedure, n (%)  22 (19.6)  3 (10.7)  0.27  David I procedure, n (%)  6 (5.4)  0  0.47  CABG, n (%)  5 (4.5)  1 (3.6)  1  Circulatory arrest, n (%)  104 (92.9)  28 (100)  0.32  Circulatory arrest time (min), mean ± SD  27 ± 9  29 ± 9  0.36  CPB time (min), mean ± SD  199 ± 50  197 ± 36  0.82  Aorta cross-clamp time (min), mean ± SD  114 ± 36  108 ± 23  0.37  Variables  No RRT (n = 112)  RRT (n = 28)  P-value  Male, n (%)  82 (73.2)  25 (89.3)  0.07  Age (years), mean ± SD  50.5 ± 13.2  55 ± 12.7  0.1  Marfan syndrome, n (%)  19 (17)  0  0.04  Hypertension, n (%)  71 (63.4)  23 (82.1)  0.06  Diabetes, n (%)  2 (1.8)  1 (3.6)  1  Stroke, n (%)  8 (7.1)  3 (10.7)  0.81  Chronic kidney disease, n (%)  2 (1.8)  3 (10.7)  0.09  eGFR (ml/min/1.73 m2), mean ± SD  91.9 ± 20.8  59.1 ± 30.2  <0.001  Malperfusion syndrome, n (%)  22 (19.6)  13 (46.4)  0.003  Emergency operation, n (%)  98 (87.5)  28 (100)  0.11  Previous TEVAR, n (%)  8 (7.1)  0  0.32  Total arch replacement, n (%)  98 (87.5)  24 (85.7)  1  Hemiarch replacement, n (%)  6 (5.4)  4 (14.3)  0.22  Stented elephant trunk, n (%)  92 (82.1)  24 (85.7)  0.87  Bentall procedure, n (%)  22 (19.6)  3 (10.7)  0.27  David I procedure, n (%)  6 (5.4)  0  0.47  CABG, n (%)  5 (4.5)  1 (3.6)  1  Circulatory arrest, n (%)  104 (92.9)  28 (100)  0.32  Circulatory arrest time (min), mean ± SD  27 ± 9  29 ± 9  0.36  CPB time (min), mean ± SD  199 ± 50  197 ± 36  0.82  Aorta cross-clamp time (min), mean ± SD  114 ± 36  108 ± 23  0.37  CABG: coronary artery bypass grafting; CPB: cardiopulmonary bypass; eGFR: estimated glomerular filtration rate; RRT: renal replacement therapy; SD: standard deviation; TEVAR: thoracic endovascular repair. Figure 1: View largeDownload slide ROC curve for the ability of estimated glomerular filtration rate in predicting postoperative renal replacement therapy; the area under curve was 0.809. ROC: receiver operating characteristic. Figure 1: View largeDownload slide ROC curve for the ability of estimated glomerular filtration rate in predicting postoperative renal replacement therapy; the area under curve was 0.809. ROC: receiver operating characteristic. In-hospital mortality was 6.5% in the normal group (5 of 76), 5% in the mild group (2 of 40), 20% in the moderate group (4 of 20) and 50% in the severe group (2 of 4). In the moderate group, the cause of death was low cardiac output syndrome in 2 patients and central nervous system complications in 2 patients. In the severe group, 2 patients who survived underwent preoperative RRT. The causes of death were abdominal viscera ischaemia due to deteriorative abdominal aortic dissection in 1 patient and multiple organ failure in 1 patient. The logistic regression analysis showed that age >60 years, moderate and severe renal dysfunction, coronary malperfusion and peripheral malperfusion were independent risk factors for in-hospital death (Table 4). Table 4: Preoperative risk factors for in-hospital-death identified by the logistic regression analysis Variables  Univariable analysis   Multivariable analysis   Odds ratio  P-value  Odds ratio  95% CI  P-value  Age >60 years  2.36  0.05  3.13  1.10–8.93  0.03  Coronary malperfusion  20.5  0.003  31.69  2.99–335.87  0.004  Bowel malperfusion  9.42  0.09        Peripheral malperfusion  6.18  0.001  5.78  1.68–19.86  0.005  Moderate/severe renal dysfunction  6.23  <0.001  3.61  1.14–11.46  0.03  Variables  Univariable analysis   Multivariable analysis   Odds ratio  P-value  Odds ratio  95% CI  P-value  Age >60 years  2.36  0.05  3.13  1.10–8.93  0.03  Coronary malperfusion  20.5  0.003  31.69  2.99–335.87  0.004  Bowel malperfusion  9.42  0.09        Peripheral malperfusion  6.18  0.001  5.78  1.68–19.86  0.005  Moderate/severe renal dysfunction  6.23  <0.001  3.61  1.14–11.46  0.03  CI: confidence interval. Table 4: Preoperative risk factors for in-hospital-death identified by the logistic regression analysis Variables  Univariable analysis   Multivariable analysis   Odds ratio  P-value  Odds ratio  95% CI  P-value  Age >60 years  2.36  0.05  3.13  1.10–8.93  0.03  Coronary malperfusion  20.5  0.003  31.69  2.99–335.87  0.004  Bowel malperfusion  9.42  0.09        Peripheral malperfusion  6.18  0.001  5.78  1.68–19.86  0.005  Moderate/severe renal dysfunction  6.23  <0.001  3.61  1.14–11.46  0.03  Variables  Univariable analysis   Multivariable analysis   Odds ratio  P-value  Odds ratio  95% CI  P-value  Age >60 years  2.36  0.05  3.13  1.10–8.93  0.03  Coronary malperfusion  20.5  0.003  31.69  2.99–335.87  0.004  Bowel malperfusion  9.42  0.09        Peripheral malperfusion  6.18  0.001  5.78  1.68–19.86  0.005  Moderate/severe renal dysfunction  6.23  <0.001  3.61  1.14–11.46  0.03  CI: confidence interval. Follow-up was 100%, and the median follow-up time was 10.5 (interquartile range 4.1–12.8) months. During follow-up, 1 patient died due to mediastinal infection. Except for the 2 patients who required RRT preoperatively, de novo RRT was not observed in other patients during the follow-up period. According to follow-up aortic CTA, complete closure or total thrombosis of the false lumen along the stented portion was observed in all patients. Along the distal portion of the descending aorta, complete closure of the false lumen was observed in 31 (24.4%) patients. Among the other patients, patency or partial thrombosis of the false lumen still existed. Both bilateral renal arteries arose from the true lumen in 22 (22.9%) patients and among the remaining patients, only a unilateral renal artery arose from the true lumen. DISCUSSION We found that moderate and severe renal dysfunction was an independent risk factor that predicted the need for postoperative RRT. Additionally, moderate and severe renal dysfunction, together with age >60 years, coronary malperfusion and peripheral malperfusion, were associated with an increased in-hospital mortality. Measurement of serum creatinine levels is a primary test for screening of renal dysfunction. However, because serum creatinine levels are affected by various parameters, including age, sex, muscle mass and metabolic level, their ability to identify renal dysfunction patients is limited [14, 15]. Huynh et al. [16] also found that eGFR is a better parameter than serum creatinine to predict the risk of mortality after thoraco-abdominal aortic surgery. Therefore, we also used the eGFR to evaluate renal function in this study. The Chronic Kidney Disease Epidemiology Collaboration equation was used because of its superior accuracy in categorizing the risk for mortality [17]. Okada et al. [10] found that in elective TAR, patients with a lower eGFR had significantly higher hospital mortality and more morbidity, including postoperative RRT. The cut-off value for the requirement of postoperative RRT was 26.0 ml/min/1.73 m2 in the previous study. However, in another study by Imasaka et al. [18], an eGFR lower than 60.0 ml/min/1.73 m2 predicted postoperative RRT in patients with acute AAD. In this study, mild and severe renal dysfunction was associated with postoperative RRT, and the cut-off value was 70 ml/min/1.73 m2. Aortic dissection only accounted for 10.5% of all patients in the study by Okada et al. [10] and in the study by Imasaka et al. [18], and less than 60% of patients underwent TAR. However, approximately 90% of patients in our AAD cohort underwent TAR. Postoperative acute kidney injury is a common complication in patients who undergo TAR under circulatory arrest [19]. Therefore, patients in this study were more likely to experience renal dysfunction postoperatively. Consequently, the discrepancy concerning cut-off values among studies may be partly caused by the heterogeneity among different patient cohorts. A higher stage of preoperative renal dysfunction was identified as one of the risk factors for in-hospital mortality in our study. Furthermore, we found that in-hospital mortality of patients with mild preoperative renal dysfunction was similar to that in patients in the normal group. Therefore, we suggest that only moderate and severe renal dysfunction increases risk of in-hospital death. We observed that in the severe group, 2 patients who survived underwent preoperative RRT, which might have contributed to the better results compared with the other 2 patients who died. Although emergent operation was intended for acute dissection at our institution, for patients with preoperative chronic kidney disease and extremely low eGFR, delay in operation and preoperative RRT might relieve patients from severe electrolyte disturbance and overload of inflammatory factors, thus increasing the safety of surgery. Ischaemia of the lower limbs and important organs is common in patients with AAD [20]. Malperfusion syndrome was found to be a risk factor for increased mortality by a multicentre registry study [4, 21]. In this study, patients with preoperative malperfusion syndrome were more likely to undergo postoperative RRT. Additionally, coronary malperfusion and peripheral malperfusion were also identified as risk factors for in-hospital death. Coronary ischaemia is a dangerous and insidious condition where concomitant CABG is performed as a salvage technique to prevent intraoperative low cardiac output syndrome. Imasaka et al. [18] suggested that concomitant CABG was useful for preventing postoperative RRT. Rapid restoration of flow in the true lumen can alleviate malperfusion syndrome and decrease postoperative complications [22]. Therefore, surgical revascularization should be considered in patients with preoperative malperfusion syndrome to improve perioperative outcomes. A more conservative strategy with the ascending aorta or hemiarch replacement can be considered to avoid a longer circulatory arrest time and cardiopulmonary bypass (CPB) time resulting from TAR. Previous studies have demonstrated that TAR increases mortality and the incidence of postoperative RRT for patients with acute AAD [18, 20]. Another study suggested that TAR combined with SET implantation could be performed with excellent outcomes [8]. Whether deep hypothermic circulatory arrest in TAR should be performed in patients with preoperative renal dysfunction is unclear. In a previous study, El-Sayed Ahmad et al. [23] suggested that moderate-to-mild (≥28°C) systemic hypothermia combined with selective antegrade cerebral perfusion could provide better protection of visceral organs. In this study, most patients underwent TAR, even in those with moderate renal dysfunction. However, TAR did not increase the incidence of postoperative RRT. Therefore, our strategy for moderate-to-deep hypothermia (rectal temperature 25–28°C) was safe in TAR. The circulatory arrest time in our series was much shorter (<30 min) when compared with previous studies, which may have contributed to the better outcome. However, in patients with severe renal dysfunction, hemiarch replacement instead of TAR was performed in 3 of 4 patients. Although TAR improves the long-term outcome, hemiarch replacement might be more appropriate for patients in an extremely poor condition. Hybrid total arch repair without deep hypothermic circulatory arrest has been shown to reduce the risk of postoperative complications [24]. Therefore, for patients with moderate and severe renal dysfunction, especially for those experiencing pre-existing kidney disease, a hybrid surgical strategy might be considered in future practice. Because most patients in this study underwent TAR, we could not compare its effect on perioperative outcomes with other techniques. Further studies are required to identify the appropriate surgical strategy for patients with preoperative renal dysfunction. We further evaluated early outcomes for patients with preoperative renal dysfunction. Although patients with moderate or severe renal dysfunction had a higher risk of postoperative RRT and in-hospital death, those who survived had excellent early outcomes. Except for the 2 patients who underwent preoperative RRT, no patients required RRT after discharge, even those who experienced moderate preoperative renal dysfunction. In this cohort, the major causes of renal dysfunction were acute mechanism including shock, hypovolaemia, malperfusion and low cardiac output. These results suggested that renal function could recover after the removal of acute factors by operation and generally did not deteriorate after discharge. Follow-up aortic CTA showed that restoration of kidney blood supply was sufficient in most patients. Considering that the average age of patients with AAD in China is younger when compared with patients included in The International Registry of Acute Aortic Dissection (IRAD) [25], TAR combined with SET implantation is reasonable for obliterating a false lumen and improving postoperative results. Further follow-up is required to assess the mid-term and long-term outcomes. Limitations This work is an observational and retrospective study. Therefore, the lack of randomization could have led to bias of our the results. Additionally, our single-centre experience might not apply to other situations. In addition, this study only discussed results of a 1-year cohort, and the number of cases were limited. Limiting the events to malperfusion syndrome, elderly patients and so on might influence the validity of the logistic regression analysis. Furthermore, this study mainly focused on perioperative outcomes. Therefore, further studies are required to evaluate the effect of preoperative renal dysfunction on mid-term and long-term outcomes for patients with AAD. CONCLUSIONS Preoperative renal dysfunction is a risk factor for postoperative RRT, and eGFR is a useful parameter for predicting the requirement for postoperative RRT. Although an increased stage of renal dysfunction is associated with a higher in-hospital mortality, mild renal dysfunction does not reduce the safety of TAR and the use of SET for AAD. 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Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png European Journal of Cardio-Thoracic Surgery Oxford University Press

Surgical and early outcomes for Type A aortic dissection with preoperative renal dysfunction stratified by estimated glomerular filtration rate

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Oxford University Press
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© The Author(s) 2018. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.
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1010-7940
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1873-734X
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10.1093/ejcts/ezy157
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Abstract

Abstract OBJECTIVES The aim of this study was to analyse the effect of preoperative renal dysfunction on surgical and early outcomes for patients with Type A aortic dissection (AAD). METHODS From January 2016 to December 2016, 140 patients with AAD who underwent surgical treatment at our institution were retrospectively analysed. According to the estimated glomerular filtration rate (eGFR), preoperative renal dysfunction was divided into 4 groups: normal (eGFR ≥90 ml/min/1.73 m2, n = 76), mild (eGFR 60–89, n = 40), moderate (eGFR 30–59, n = 20) and severe (eGFR <30, n = 4). RESULTS Major complications included prolonged ventilation requiring tracheotomy in 15 patients, renal replacement therapy (RRT) in 28 patients, stroke in 11 patients and paraplegia in 4 patients. The best cut-off value of the eGFR for predicting postoperative RRT was 70 ml/min/1.73 m2 (area under the receiver operating characteristic curve was 0.809). In-hospital mortality was 9.3% (6.5% in the normal group, 5% in the mild group, 20% in the moderate group and 50% in the severe group). Logistic regression analysis showed that age >60 years, moderate and severe renal dysfunction, coronary malperfusion and peripheral malperfusion were risk factors for in-hospital death. CONCLUSIONS Total arch replacement can be safely performed in patients with AAD and preoperative mild renal dysfunction. Preoperative renal dysfunction is a risk factor for postoperative RRT, and eGFR is useful for predicting the requirement for postoperative RRT. Our surgical strategy for total arch replacement and stented elephant trunk for patients with AAD and mild preoperative renal dysfunction has excellent early outcomes. Renal dysfunction, Estimated glomerular filtration rate, Type A aortic dissection, Renal replacement therapy INTRODUCTION Renal dysfunction is associated with high complication rates and mortality in patients undergoing elective cardiac surgery including coronary artery bypass grafting (CABG) and aortic valve replacement [1, 2]. However, studies concerning the effect of preoperative renal function on early outcomes after surgery for Type A aortic dissection (AAD) are limited. AAD remains a life-threatening situation requiring surgical intervention. Although diagnostics and surgical techniques have substantially improved, morbidity and mortality remain high [3]. Various risk factors, including preoperative renal dysfunction, have been identified for in-hospital death by previous studies [4, 5]. Additionally, the incidence of renal dysfunction after aortic surgery is high and associated with increased early and long-term mortality [5–7]. Therefore, determining the risk factors for postoperative renal dysfunction and in-hospital death is important. Total arch replacement (TAR) combined with stented elephant trunk (SET) implantation is associated with encouraging surgical results and promising outcomes [8, 9]. However, preoperative renal dysfunction was reported to be a strong predictor of worse outcomes after TAR [10]. The requirement for hypothermic circulatory arrest, which may increase the incidence of severe complications, has caused doubt on the safety of this procedure for patients with preoperative renal dysfunction. TAR combined with SET implantation is the primary surgical strategy for most patients with AAD at our institution. The aim of this study was to determine the risk factors for postoperative renal replacement therapy (RRT) and in-hospital mortality after surgery for AAD. We also evaluated the effect of preoperative renal dysfunction on in-hospital and early outcomes. MATERIALS AND METHODS Study population From January 2016 to December 2016, patients who underwent surgical treatment for AAD at our institution were retrospectively reviewed. We excluded patients who underwent an open heart operation previously, and 140 patients were included in this study. The diagnosis of AAD was confirmed using computed tomography angiography (CTA). Dissection was considered acute if it was surgically treated within 2 weeks from the onset of symptoms (126 patients). Fourteen patients who were surgically treated after 2 weeks from the onset of symptoms were considered chronic dissections. The average interval between diagnosis of dissection at our institution and surgical treatment for the whole cohort was 30.3 ± 47.7 h. The study protocol was approved by the Ethics Committee of Zhongshan Hospital of Fudan University and was conducted in accordance with the Declaration of Helsinki. Informed consent was obtained from each patient involved in this study. The glomerular filtration rate at the time of admission was used to assess renal function [11, 12]. In this study, the glomerular filtration rate was estimated from the Chronic Kidney Disease Epidemiology Collaboration equation [13]. According to the estimated glomerular filtration rate (eGFR), preoperative renal function was classified into 4 categories: the normal group (eGFR >90 ml/min/1.73 m2, 76 patients), the mild group (eGFR 60–90 ml/min/1.73 m2, 40 patients), the moderate group (eGFR 30–60 ml/min/1.73 m2, 20 patients) and the severe group (eGFR <30 ml/min/1.73 m2, 4 patients). Preoperative profiles, operative data and postoperative results were retrospectively reviewed and analysed. In-hospital mortality was defined as death occurred during hospital stay or 30 days postoperatively. The indications for postoperative RRT included fluid overload, acidosis and electrolyte disturbances. Operative technique All operations were performed through midline sternotomy. Surgical techniques included TAR in 122 (87%) patients and SET implantation in 115 (82%) patients. Additionally, the Bentall procedure was performed in 25 (18%) patients, David I in 6 (4%) patients and CABG in 6 (4%) patients. TAR combined with SET implantation under circulatory arrest was our primary surgical strategy. For patients who previously underwent thoracic endovascular aortic repair, isolated TAR was performed. For patients with dissection restricted to the ascending aorta, ascending aorta replacement with or without the Bentall procedure was performed. Circulatory arrest was not required in these patients. Standard transcutaneous cerebral oximetry monitoring and transoesophageal echocardiography were applied in all cases. Arterial cannulation sites were the femoral artery and right axillary artery in patients who required circulatory arrest. The femoral artery and right atrial appendage were cannulated for cardiopulmonary bypass. If circulatory arrest was required, surgery was performed with protection of the brain by unilateral selective cerebral perfusion through the right axillary artery. This perfusion was maintained at a perfusion rate of 10 ml/kg/min. Moderate-to-deep hypothermia with a temperature of 22–23°C for the nasopharynx and 25–28°C for the bladder was applied during circulatory arrest. The heart was arrested with cold blood cardioplegia infusing into the coronary ostia after aortic cross-clamping. Retrograde infusion of cardioplegia through the coronary sinus was performed to enhance myocardial protection. A 4-branch prosthetic graft with or without SET implantation was used in TAR. Open distal anastomosis was first completed, and the 4-branch prosthetic graft was cross-clamped. Blood perfusion of the lower body was then started via femoral artery cannulation. Anastomosis of the left common carotid artery, left subclavian artery and innominate artery was completed. After completing anastomosis of the left common carotid artery, bilateral cerebral perfusion and full cardiopulmonary bypass flow were resumed. The Bentall or David I procedure was performed accordingly during the rewarming period. Finally, proximal anastomosis was completed. For patients with severe coronary malperfusion, emergent CABG was performed, and for patients with severe lower limb malperfusion, distal revascularization (the aortic arch-femoral bypass in 4 patients, ascending aorta-femoral bypass in 1 patient, ascending iliac bypass in 1 patient and descending iliac bypass in 1 patient) was performed. Statistical analysis Continuous variables are expressed as mean ± standard deviation, and categorical variables as counts and percentages. One-way analysis of variance and the χ2 test or Fisher’s exact test were used to compare continuous and categorical variables, respectively. For abnormally distributed variables, the Kruskal–Wallis test was used to compare the differences. Logistic regression models were used to identify univariable and multivariable predictors for postoperative RRT and in-hospital mortality. In the logistic regression analysis, potential predictors of in-hospital death and postoperative need for RRT were tested in a univariable fashion, and variables with P-value <0.1 were included into the multivariable analysis. The results of the logistic regression analysis are presented as odds ratios with the corresponding 95% confidence intervals (CIs). Calculation of the area under the receiver operating characteristic curve with a 95% CI was used to assess the most clinically useful level of the eGFR for predicting the requirement for postoperative RRT. Cut-off values for the highest sensitivity and specificity were identified. A P-value <0.05 was considered statistically significant. All statistical analyses were conducted using the SPSS software (Version 22.0. IBM Corp., Armonk, NY, USA). RESULTS Demographic characteristics and surgical details are shown in Table 1. In addition to the eGFR, significant differences were observed in malperfusion syndrome (P = 0.02) and previous chronic kidney disease (P = 0.003) among all of the preoperative demographic characteristics. Table 1: Demographic characteristics and surgical details Variables  Total (n = 140)  Normal group (n = 76)  Mild group (n = 40)  Moderate group (n = 20)  Severe group (n = 4)  P-value  Male, n (%)  107 (76.4)  57 (75)  31 (77.5)  16 (80)  3 (75)  0.97  Age (years), mean ± SD  51.4 ± 12.7  48.9 ± 13.2  54.7 ± 12.2  53.8 ± 11.2  53.8 ± 6.7  0.09  Marfan syndrome, n (%)  19 (13.6)  13 (17.1)  5 (12.5)  1 (5)  0  0.19  Hypertension, n (%)  94 (67.1)  46 (60.5)  28 (70)  16 (80)  4 (100)  0.09  Diabetes, n (%)  3 (2.1)  0 (0)  2 (5)  0  1 (25)  0.04  Stroke, n (%)  11 (7.9)  2 (2.6)  7 (17.5)  2 (10)  0  0.04  Chronic kidney disease, n (%)  5 (3.6)  0  1 (2.5)  2 (10)  2 (50)  0.003  eGFR (ml/min/1.73 m2), mean ± SD  85.1 ± 26.5  105 ± 9.7  76.3 ± 8.6  46.9 ± 9.4  10 ± 8.3  <0.001  Malperfusion syndrome, n (%)  35 (25)  16 (21.1)  7 (17.5)  11 (55)  1 (25)  0.02   Cerebral or spinal, n (%)  13 (9.3)  7 (9.2)  4 (10)  1 (5)  1 (25)  0.71   Coronary, n (%)  5 (3.6)  2 (2.6)  1 (2.5)  1 (5)  1 (25)  0.42   Peripheral, n (%)  18 (12.9)  7 (9.2)  2 (5)  9 (45)  0  0.001   Bowel, n (%)  3 (2.1)  1 (1.3)  1 (2.5)  0  1 (25)  0.21  Emergency operation, n (%)  126 (90)  68 (89.5)  36 (90)  18 (90)  4 (100)  0.83  Previous TEVAR, n (%)  8 (5.7)  3 (3.9)  5 (12.5)  0  0  0.12  Total arch replacement, n (%)  122 (87.1)  64 (84.2)  37 (92.5)  20 (100)  1 (25)  0.002  Hemiarch replacement, n (%)  10 (7.1)  6 (7.9)  1 (2.5)  0  3 (75)  0.001  Stented elephant trunk, n (%)  115 (82.1)  61 (80.3)  33 (82.5)  20 (100)  1 (25)  0.002  Bentall procedure, n (%)  25 (17.9)  19 (25)  6 (15)  0  0  0.02  David I procedure, n (%)  6 (4.3)  4 (5.3)  1 (2.5)  1 (5)  0  0.83  CABG, n (%)  6 (4.3)  3 (3.9)  0  2 (10)  1 (25)  0.08  Circulatory arrest, n (%)  132 (94.3)  70 (92.1)  38 (95)  20 (100)  4 (100)  0.33  Circulatory arrest time (min), mean ± SD  27 ± 9  27 ± 8  29 ± 13  28 ± 7  30 ± 11  0.64  CPB time (min), mean ± SD  199 ± 47  198 ± 49  196 ± 29  204 ± 52  205 ± 56  0.95  Aorta cross-clamp time (min), mean ± SD  113 ± 34  115 ± 36  107 ± 29  109 ± 29  115 ± 38  0.78  Variables  Total (n = 140)  Normal group (n = 76)  Mild group (n = 40)  Moderate group (n = 20)  Severe group (n = 4)  P-value  Male, n (%)  107 (76.4)  57 (75)  31 (77.5)  16 (80)  3 (75)  0.97  Age (years), mean ± SD  51.4 ± 12.7  48.9 ± 13.2  54.7 ± 12.2  53.8 ± 11.2  53.8 ± 6.7  0.09  Marfan syndrome, n (%)  19 (13.6)  13 (17.1)  5 (12.5)  1 (5)  0  0.19  Hypertension, n (%)  94 (67.1)  46 (60.5)  28 (70)  16 (80)  4 (100)  0.09  Diabetes, n (%)  3 (2.1)  0 (0)  2 (5)  0  1 (25)  0.04  Stroke, n (%)  11 (7.9)  2 (2.6)  7 (17.5)  2 (10)  0  0.04  Chronic kidney disease, n (%)  5 (3.6)  0  1 (2.5)  2 (10)  2 (50)  0.003  eGFR (ml/min/1.73 m2), mean ± SD  85.1 ± 26.5  105 ± 9.7  76.3 ± 8.6  46.9 ± 9.4  10 ± 8.3  <0.001  Malperfusion syndrome, n (%)  35 (25)  16 (21.1)  7 (17.5)  11 (55)  1 (25)  0.02   Cerebral or spinal, n (%)  13 (9.3)  7 (9.2)  4 (10)  1 (5)  1 (25)  0.71   Coronary, n (%)  5 (3.6)  2 (2.6)  1 (2.5)  1 (5)  1 (25)  0.42   Peripheral, n (%)  18 (12.9)  7 (9.2)  2 (5)  9 (45)  0  0.001   Bowel, n (%)  3 (2.1)  1 (1.3)  1 (2.5)  0  1 (25)  0.21  Emergency operation, n (%)  126 (90)  68 (89.5)  36 (90)  18 (90)  4 (100)  0.83  Previous TEVAR, n (%)  8 (5.7)  3 (3.9)  5 (12.5)  0  0  0.12  Total arch replacement, n (%)  122 (87.1)  64 (84.2)  37 (92.5)  20 (100)  1 (25)  0.002  Hemiarch replacement, n (%)  10 (7.1)  6 (7.9)  1 (2.5)  0  3 (75)  0.001  Stented elephant trunk, n (%)  115 (82.1)  61 (80.3)  33 (82.5)  20 (100)  1 (25)  0.002  Bentall procedure, n (%)  25 (17.9)  19 (25)  6 (15)  0  0  0.02  David I procedure, n (%)  6 (4.3)  4 (5.3)  1 (2.5)  1 (5)  0  0.83  CABG, n (%)  6 (4.3)  3 (3.9)  0  2 (10)  1 (25)  0.08  Circulatory arrest, n (%)  132 (94.3)  70 (92.1)  38 (95)  20 (100)  4 (100)  0.33  Circulatory arrest time (min), mean ± SD  27 ± 9  27 ± 8  29 ± 13  28 ± 7  30 ± 11  0.64  CPB time (min), mean ± SD  199 ± 47  198 ± 49  196 ± 29  204 ± 52  205 ± 56  0.95  Aorta cross-clamp time (min), mean ± SD  113 ± 34  115 ± 36  107 ± 29  109 ± 29  115 ± 38  0.78  CABG: coronary artery bypass grafting; CPB: cardiopulmonary bypass; eGFR: estimated glomerular filtration rate; SD: standard deviation; TEVAR: thoracic endovascular repair. Table 1: Demographic characteristics and surgical details Variables  Total (n = 140)  Normal group (n = 76)  Mild group (n = 40)  Moderate group (n = 20)  Severe group (n = 4)  P-value  Male, n (%)  107 (76.4)  57 (75)  31 (77.5)  16 (80)  3 (75)  0.97  Age (years), mean ± SD  51.4 ± 12.7  48.9 ± 13.2  54.7 ± 12.2  53.8 ± 11.2  53.8 ± 6.7  0.09  Marfan syndrome, n (%)  19 (13.6)  13 (17.1)  5 (12.5)  1 (5)  0  0.19  Hypertension, n (%)  94 (67.1)  46 (60.5)  28 (70)  16 (80)  4 (100)  0.09  Diabetes, n (%)  3 (2.1)  0 (0)  2 (5)  0  1 (25)  0.04  Stroke, n (%)  11 (7.9)  2 (2.6)  7 (17.5)  2 (10)  0  0.04  Chronic kidney disease, n (%)  5 (3.6)  0  1 (2.5)  2 (10)  2 (50)  0.003  eGFR (ml/min/1.73 m2), mean ± SD  85.1 ± 26.5  105 ± 9.7  76.3 ± 8.6  46.9 ± 9.4  10 ± 8.3  <0.001  Malperfusion syndrome, n (%)  35 (25)  16 (21.1)  7 (17.5)  11 (55)  1 (25)  0.02   Cerebral or spinal, n (%)  13 (9.3)  7 (9.2)  4 (10)  1 (5)  1 (25)  0.71   Coronary, n (%)  5 (3.6)  2 (2.6)  1 (2.5)  1 (5)  1 (25)  0.42   Peripheral, n (%)  18 (12.9)  7 (9.2)  2 (5)  9 (45)  0  0.001   Bowel, n (%)  3 (2.1)  1 (1.3)  1 (2.5)  0  1 (25)  0.21  Emergency operation, n (%)  126 (90)  68 (89.5)  36 (90)  18 (90)  4 (100)  0.83  Previous TEVAR, n (%)  8 (5.7)  3 (3.9)  5 (12.5)  0  0  0.12  Total arch replacement, n (%)  122 (87.1)  64 (84.2)  37 (92.5)  20 (100)  1 (25)  0.002  Hemiarch replacement, n (%)  10 (7.1)  6 (7.9)  1 (2.5)  0  3 (75)  0.001  Stented elephant trunk, n (%)  115 (82.1)  61 (80.3)  33 (82.5)  20 (100)  1 (25)  0.002  Bentall procedure, n (%)  25 (17.9)  19 (25)  6 (15)  0  0  0.02  David I procedure, n (%)  6 (4.3)  4 (5.3)  1 (2.5)  1 (5)  0  0.83  CABG, n (%)  6 (4.3)  3 (3.9)  0  2 (10)  1 (25)  0.08  Circulatory arrest, n (%)  132 (94.3)  70 (92.1)  38 (95)  20 (100)  4 (100)  0.33  Circulatory arrest time (min), mean ± SD  27 ± 9  27 ± 8  29 ± 13  28 ± 7  30 ± 11  0.64  CPB time (min), mean ± SD  199 ± 47  198 ± 49  196 ± 29  204 ± 52  205 ± 56  0.95  Aorta cross-clamp time (min), mean ± SD  113 ± 34  115 ± 36  107 ± 29  109 ± 29  115 ± 38  0.78  Variables  Total (n = 140)  Normal group (n = 76)  Mild group (n = 40)  Moderate group (n = 20)  Severe group (n = 4)  P-value  Male, n (%)  107 (76.4)  57 (75)  31 (77.5)  16 (80)  3 (75)  0.97  Age (years), mean ± SD  51.4 ± 12.7  48.9 ± 13.2  54.7 ± 12.2  53.8 ± 11.2  53.8 ± 6.7  0.09  Marfan syndrome, n (%)  19 (13.6)  13 (17.1)  5 (12.5)  1 (5)  0  0.19  Hypertension, n (%)  94 (67.1)  46 (60.5)  28 (70)  16 (80)  4 (100)  0.09  Diabetes, n (%)  3 (2.1)  0 (0)  2 (5)  0  1 (25)  0.04  Stroke, n (%)  11 (7.9)  2 (2.6)  7 (17.5)  2 (10)  0  0.04  Chronic kidney disease, n (%)  5 (3.6)  0  1 (2.5)  2 (10)  2 (50)  0.003  eGFR (ml/min/1.73 m2), mean ± SD  85.1 ± 26.5  105 ± 9.7  76.3 ± 8.6  46.9 ± 9.4  10 ± 8.3  <0.001  Malperfusion syndrome, n (%)  35 (25)  16 (21.1)  7 (17.5)  11 (55)  1 (25)  0.02   Cerebral or spinal, n (%)  13 (9.3)  7 (9.2)  4 (10)  1 (5)  1 (25)  0.71   Coronary, n (%)  5 (3.6)  2 (2.6)  1 (2.5)  1 (5)  1 (25)  0.42   Peripheral, n (%)  18 (12.9)  7 (9.2)  2 (5)  9 (45)  0  0.001   Bowel, n (%)  3 (2.1)  1 (1.3)  1 (2.5)  0  1 (25)  0.21  Emergency operation, n (%)  126 (90)  68 (89.5)  36 (90)  18 (90)  4 (100)  0.83  Previous TEVAR, n (%)  8 (5.7)  3 (3.9)  5 (12.5)  0  0  0.12  Total arch replacement, n (%)  122 (87.1)  64 (84.2)  37 (92.5)  20 (100)  1 (25)  0.002  Hemiarch replacement, n (%)  10 (7.1)  6 (7.9)  1 (2.5)  0  3 (75)  0.001  Stented elephant trunk, n (%)  115 (82.1)  61 (80.3)  33 (82.5)  20 (100)  1 (25)  0.002  Bentall procedure, n (%)  25 (17.9)  19 (25)  6 (15)  0  0  0.02  David I procedure, n (%)  6 (4.3)  4 (5.3)  1 (2.5)  1 (5)  0  0.83  CABG, n (%)  6 (4.3)  3 (3.9)  0  2 (10)  1 (25)  0.08  Circulatory arrest, n (%)  132 (94.3)  70 (92.1)  38 (95)  20 (100)  4 (100)  0.33  Circulatory arrest time (min), mean ± SD  27 ± 9  27 ± 8  29 ± 13  28 ± 7  30 ± 11  0.64  CPB time (min), mean ± SD  199 ± 47  198 ± 49  196 ± 29  204 ± 52  205 ± 56  0.95  Aorta cross-clamp time (min), mean ± SD  113 ± 34  115 ± 36  107 ± 29  109 ± 29  115 ± 38  0.78  CABG: coronary artery bypass grafting; CPB: cardiopulmonary bypass; eGFR: estimated glomerular filtration rate; SD: standard deviation; TEVAR: thoracic endovascular repair. With regard to surgical details, the Bentall procedure was mainly practiced in patients with normal renal function and mild renal dysfunction. Hemiarch replacement was performed in 75% (3 of 4) of the patients in the severe group. In the other 3 groups, TAR was the primary procedure. Circulatory arrest was used in most of the patients among the groups. Perioperative data are presented in Table 2. In-hospital mortality was 9.3% (13 of 140). Two patients with severe renal dysfunction required preoperative RRT. Major complications included prolonged ventilation requiring tracheotomy in 15 (10.7%) patients, RRT in 28 (20%) patients and central nervous system complications in 18 patients (12.8%, brain injury in 14 patients and spinal cord injury in 4 patients). Table 2: Postoperative complications and in-hospital mortality Variables  Total (n = 140)  Normal group (n = 76)  Mild group (n = 40)  Moderate group (n = 20)  Severe group (n = 4)  P-value  Low cardiac output syndrome, n (%)  6 (4.3)  3 (3.9)  2 (5)  1 (5)  0  0.93  Postoperative stroke, n (%)  11 (7.9)  6 (7.9)  1 (2.5)  4 (20)  0  0.13  Hypoxia, n (%)  27 (19.3)  13 (17.1)  8 (20)  5 (25)  1 (25)  0.87  Prolonged ventilation requiring tracheotomy, n (%)  15 (10.7)  7 (9.2)  3 (7.5)  4 (20)  1 (25)  0.43  RRT, n (%)  28 (20)  7 (9.2)  6 (15)  11 (55)  4 (100)  <0.001a  Intensive care time (days), mean ± SD  8.2 ± 14  8 ± 15.9  6.3 ± 8  12.1 ± 15.9  12.1 ± 14.7  0.46  In-hospital mortality, n (%)  13 (9.3)  5 (6.6)  2 (5)  4 (20)  2 (50)  0.007  Variables  Total (n = 140)  Normal group (n = 76)  Mild group (n = 40)  Moderate group (n = 20)  Severe group (n = 4)  P-value  Low cardiac output syndrome, n (%)  6 (4.3)  3 (3.9)  2 (5)  1 (5)  0  0.93  Postoperative stroke, n (%)  11 (7.9)  6 (7.9)  1 (2.5)  4 (20)  0  0.13  Hypoxia, n (%)  27 (19.3)  13 (17.1)  8 (20)  5 (25)  1 (25)  0.87  Prolonged ventilation requiring tracheotomy, n (%)  15 (10.7)  7 (9.2)  3 (7.5)  4 (20)  1 (25)  0.43  RRT, n (%)  28 (20)  7 (9.2)  6 (15)  11 (55)  4 (100)  <0.001a  Intensive care time (days), mean ± SD  8.2 ± 14  8 ± 15.9  6.3 ± 8  12.1 ± 15.9  12.1 ± 14.7  0.46  In-hospital mortality, n (%)  13 (9.3)  5 (6.6)  2 (5)  4 (20)  2 (50)  0.007  a Compared between groups: the normal group versus the mild group, P = 0.22; the normal group versus the moderate group, P < 0.001; the normal group versus the severe group, P < 0.001; the mild group versus the moderate group, P = 0.03; the mild group versus the severe group, P = 0.02; the moderate group versus the severe group, P = 0.3. RRT: renal replacement therapy; SD: standard deviation. Table 2: Postoperative complications and in-hospital mortality Variables  Total (n = 140)  Normal group (n = 76)  Mild group (n = 40)  Moderate group (n = 20)  Severe group (n = 4)  P-value  Low cardiac output syndrome, n (%)  6 (4.3)  3 (3.9)  2 (5)  1 (5)  0  0.93  Postoperative stroke, n (%)  11 (7.9)  6 (7.9)  1 (2.5)  4 (20)  0  0.13  Hypoxia, n (%)  27 (19.3)  13 (17.1)  8 (20)  5 (25)  1 (25)  0.87  Prolonged ventilation requiring tracheotomy, n (%)  15 (10.7)  7 (9.2)  3 (7.5)  4 (20)  1 (25)  0.43  RRT, n (%)  28 (20)  7 (9.2)  6 (15)  11 (55)  4 (100)  <0.001a  Intensive care time (days), mean ± SD  8.2 ± 14  8 ± 15.9  6.3 ± 8  12.1 ± 15.9  12.1 ± 14.7  0.46  In-hospital mortality, n (%)  13 (9.3)  5 (6.6)  2 (5)  4 (20)  2 (50)  0.007  Variables  Total (n = 140)  Normal group (n = 76)  Mild group (n = 40)  Moderate group (n = 20)  Severe group (n = 4)  P-value  Low cardiac output syndrome, n (%)  6 (4.3)  3 (3.9)  2 (5)  1 (5)  0  0.93  Postoperative stroke, n (%)  11 (7.9)  6 (7.9)  1 (2.5)  4 (20)  0  0.13  Hypoxia, n (%)  27 (19.3)  13 (17.1)  8 (20)  5 (25)  1 (25)  0.87  Prolonged ventilation requiring tracheotomy, n (%)  15 (10.7)  7 (9.2)  3 (7.5)  4 (20)  1 (25)  0.43  RRT, n (%)  28 (20)  7 (9.2)  6 (15)  11 (55)  4 (100)  <0.001a  Intensive care time (days), mean ± SD  8.2 ± 14  8 ± 15.9  6.3 ± 8  12.1 ± 15.9  12.1 ± 14.7  0.46  In-hospital mortality, n (%)  13 (9.3)  5 (6.6)  2 (5)  4 (20)  2 (50)  0.007  a Compared between groups: the normal group versus the mild group, P = 0.22; the normal group versus the moderate group, P < 0.001; the normal group versus the severe group, P < 0.001; the mild group versus the moderate group, P = 0.03; the mild group versus the severe group, P = 0.02; the moderate group versus the severe group, P = 0.3. RRT: renal replacement therapy; SD: standard deviation. Differences in clinical and surgical details are shown in Table 3 between patients who required postoperative RRT and those who did not require RRT. An increased stage of preoperative renal dysfunction was an independent risk factor of postoperative RRT (odds ratio 4.4, 95% CI 2.5–7.8; P < 0.001). After further examination, we found that there was no statistically significant difference in the incidence of postoperative RRT between the mild and normal groups (P > 0.05). Moderate and severe renal dysfunction was associated with an increased incidence of postoperative RRT. In receiver operating characteristic curve analysis for the ability of preoperative eGFR to predict postoperative RRT, the area under the curve was 0.809 (95% CI 0.718–0.900) as presented in Fig. 1. A cut-off value of 70 ml/min/1.73 m2 was the most useful in predicting the requirement for postoperative RRT. Table 3: Differences in preoperative and operative details between patients with and without postoperative RRT Variables  No RRT (n = 112)  RRT (n = 28)  P-value  Male, n (%)  82 (73.2)  25 (89.3)  0.07  Age (years), mean ± SD  50.5 ± 13.2  55 ± 12.7  0.1  Marfan syndrome, n (%)  19 (17)  0  0.04  Hypertension, n (%)  71 (63.4)  23 (82.1)  0.06  Diabetes, n (%)  2 (1.8)  1 (3.6)  1  Stroke, n (%)  8 (7.1)  3 (10.7)  0.81  Chronic kidney disease, n (%)  2 (1.8)  3 (10.7)  0.09  eGFR (ml/min/1.73 m2), mean ± SD  91.9 ± 20.8  59.1 ± 30.2  <0.001  Malperfusion syndrome, n (%)  22 (19.6)  13 (46.4)  0.003  Emergency operation, n (%)  98 (87.5)  28 (100)  0.11  Previous TEVAR, n (%)  8 (7.1)  0  0.32  Total arch replacement, n (%)  98 (87.5)  24 (85.7)  1  Hemiarch replacement, n (%)  6 (5.4)  4 (14.3)  0.22  Stented elephant trunk, n (%)  92 (82.1)  24 (85.7)  0.87  Bentall procedure, n (%)  22 (19.6)  3 (10.7)  0.27  David I procedure, n (%)  6 (5.4)  0  0.47  CABG, n (%)  5 (4.5)  1 (3.6)  1  Circulatory arrest, n (%)  104 (92.9)  28 (100)  0.32  Circulatory arrest time (min), mean ± SD  27 ± 9  29 ± 9  0.36  CPB time (min), mean ± SD  199 ± 50  197 ± 36  0.82  Aorta cross-clamp time (min), mean ± SD  114 ± 36  108 ± 23  0.37  Variables  No RRT (n = 112)  RRT (n = 28)  P-value  Male, n (%)  82 (73.2)  25 (89.3)  0.07  Age (years), mean ± SD  50.5 ± 13.2  55 ± 12.7  0.1  Marfan syndrome, n (%)  19 (17)  0  0.04  Hypertension, n (%)  71 (63.4)  23 (82.1)  0.06  Diabetes, n (%)  2 (1.8)  1 (3.6)  1  Stroke, n (%)  8 (7.1)  3 (10.7)  0.81  Chronic kidney disease, n (%)  2 (1.8)  3 (10.7)  0.09  eGFR (ml/min/1.73 m2), mean ± SD  91.9 ± 20.8  59.1 ± 30.2  <0.001  Malperfusion syndrome, n (%)  22 (19.6)  13 (46.4)  0.003  Emergency operation, n (%)  98 (87.5)  28 (100)  0.11  Previous TEVAR, n (%)  8 (7.1)  0  0.32  Total arch replacement, n (%)  98 (87.5)  24 (85.7)  1  Hemiarch replacement, n (%)  6 (5.4)  4 (14.3)  0.22  Stented elephant trunk, n (%)  92 (82.1)  24 (85.7)  0.87  Bentall procedure, n (%)  22 (19.6)  3 (10.7)  0.27  David I procedure, n (%)  6 (5.4)  0  0.47  CABG, n (%)  5 (4.5)  1 (3.6)  1  Circulatory arrest, n (%)  104 (92.9)  28 (100)  0.32  Circulatory arrest time (min), mean ± SD  27 ± 9  29 ± 9  0.36  CPB time (min), mean ± SD  199 ± 50  197 ± 36  0.82  Aorta cross-clamp time (min), mean ± SD  114 ± 36  108 ± 23  0.37  CABG: coronary artery bypass grafting; CPB: cardiopulmonary bypass; eGFR: estimated glomerular filtration rate; RRT: renal replacement therapy; SD: standard deviation; TEVAR: thoracic endovascular repair. Table 3: Differences in preoperative and operative details between patients with and without postoperative RRT Variables  No RRT (n = 112)  RRT (n = 28)  P-value  Male, n (%)  82 (73.2)  25 (89.3)  0.07  Age (years), mean ± SD  50.5 ± 13.2  55 ± 12.7  0.1  Marfan syndrome, n (%)  19 (17)  0  0.04  Hypertension, n (%)  71 (63.4)  23 (82.1)  0.06  Diabetes, n (%)  2 (1.8)  1 (3.6)  1  Stroke, n (%)  8 (7.1)  3 (10.7)  0.81  Chronic kidney disease, n (%)  2 (1.8)  3 (10.7)  0.09  eGFR (ml/min/1.73 m2), mean ± SD  91.9 ± 20.8  59.1 ± 30.2  <0.001  Malperfusion syndrome, n (%)  22 (19.6)  13 (46.4)  0.003  Emergency operation, n (%)  98 (87.5)  28 (100)  0.11  Previous TEVAR, n (%)  8 (7.1)  0  0.32  Total arch replacement, n (%)  98 (87.5)  24 (85.7)  1  Hemiarch replacement, n (%)  6 (5.4)  4 (14.3)  0.22  Stented elephant trunk, n (%)  92 (82.1)  24 (85.7)  0.87  Bentall procedure, n (%)  22 (19.6)  3 (10.7)  0.27  David I procedure, n (%)  6 (5.4)  0  0.47  CABG, n (%)  5 (4.5)  1 (3.6)  1  Circulatory arrest, n (%)  104 (92.9)  28 (100)  0.32  Circulatory arrest time (min), mean ± SD  27 ± 9  29 ± 9  0.36  CPB time (min), mean ± SD  199 ± 50  197 ± 36  0.82  Aorta cross-clamp time (min), mean ± SD  114 ± 36  108 ± 23  0.37  Variables  No RRT (n = 112)  RRT (n = 28)  P-value  Male, n (%)  82 (73.2)  25 (89.3)  0.07  Age (years), mean ± SD  50.5 ± 13.2  55 ± 12.7  0.1  Marfan syndrome, n (%)  19 (17)  0  0.04  Hypertension, n (%)  71 (63.4)  23 (82.1)  0.06  Diabetes, n (%)  2 (1.8)  1 (3.6)  1  Stroke, n (%)  8 (7.1)  3 (10.7)  0.81  Chronic kidney disease, n (%)  2 (1.8)  3 (10.7)  0.09  eGFR (ml/min/1.73 m2), mean ± SD  91.9 ± 20.8  59.1 ± 30.2  <0.001  Malperfusion syndrome, n (%)  22 (19.6)  13 (46.4)  0.003  Emergency operation, n (%)  98 (87.5)  28 (100)  0.11  Previous TEVAR, n (%)  8 (7.1)  0  0.32  Total arch replacement, n (%)  98 (87.5)  24 (85.7)  1  Hemiarch replacement, n (%)  6 (5.4)  4 (14.3)  0.22  Stented elephant trunk, n (%)  92 (82.1)  24 (85.7)  0.87  Bentall procedure, n (%)  22 (19.6)  3 (10.7)  0.27  David I procedure, n (%)  6 (5.4)  0  0.47  CABG, n (%)  5 (4.5)  1 (3.6)  1  Circulatory arrest, n (%)  104 (92.9)  28 (100)  0.32  Circulatory arrest time (min), mean ± SD  27 ± 9  29 ± 9  0.36  CPB time (min), mean ± SD  199 ± 50  197 ± 36  0.82  Aorta cross-clamp time (min), mean ± SD  114 ± 36  108 ± 23  0.37  CABG: coronary artery bypass grafting; CPB: cardiopulmonary bypass; eGFR: estimated glomerular filtration rate; RRT: renal replacement therapy; SD: standard deviation; TEVAR: thoracic endovascular repair. Figure 1: View largeDownload slide ROC curve for the ability of estimated glomerular filtration rate in predicting postoperative renal replacement therapy; the area under curve was 0.809. ROC: receiver operating characteristic. Figure 1: View largeDownload slide ROC curve for the ability of estimated glomerular filtration rate in predicting postoperative renal replacement therapy; the area under curve was 0.809. ROC: receiver operating characteristic. In-hospital mortality was 6.5% in the normal group (5 of 76), 5% in the mild group (2 of 40), 20% in the moderate group (4 of 20) and 50% in the severe group (2 of 4). In the moderate group, the cause of death was low cardiac output syndrome in 2 patients and central nervous system complications in 2 patients. In the severe group, 2 patients who survived underwent preoperative RRT. The causes of death were abdominal viscera ischaemia due to deteriorative abdominal aortic dissection in 1 patient and multiple organ failure in 1 patient. The logistic regression analysis showed that age >60 years, moderate and severe renal dysfunction, coronary malperfusion and peripheral malperfusion were independent risk factors for in-hospital death (Table 4). Table 4: Preoperative risk factors for in-hospital-death identified by the logistic regression analysis Variables  Univariable analysis   Multivariable analysis   Odds ratio  P-value  Odds ratio  95% CI  P-value  Age >60 years  2.36  0.05  3.13  1.10–8.93  0.03  Coronary malperfusion  20.5  0.003  31.69  2.99–335.87  0.004  Bowel malperfusion  9.42  0.09        Peripheral malperfusion  6.18  0.001  5.78  1.68–19.86  0.005  Moderate/severe renal dysfunction  6.23  <0.001  3.61  1.14–11.46  0.03  Variables  Univariable analysis   Multivariable analysis   Odds ratio  P-value  Odds ratio  95% CI  P-value  Age >60 years  2.36  0.05  3.13  1.10–8.93  0.03  Coronary malperfusion  20.5  0.003  31.69  2.99–335.87  0.004  Bowel malperfusion  9.42  0.09        Peripheral malperfusion  6.18  0.001  5.78  1.68–19.86  0.005  Moderate/severe renal dysfunction  6.23  <0.001  3.61  1.14–11.46  0.03  CI: confidence interval. Table 4: Preoperative risk factors for in-hospital-death identified by the logistic regression analysis Variables  Univariable analysis   Multivariable analysis   Odds ratio  P-value  Odds ratio  95% CI  P-value  Age >60 years  2.36  0.05  3.13  1.10–8.93  0.03  Coronary malperfusion  20.5  0.003  31.69  2.99–335.87  0.004  Bowel malperfusion  9.42  0.09        Peripheral malperfusion  6.18  0.001  5.78  1.68–19.86  0.005  Moderate/severe renal dysfunction  6.23  <0.001  3.61  1.14–11.46  0.03  Variables  Univariable analysis   Multivariable analysis   Odds ratio  P-value  Odds ratio  95% CI  P-value  Age >60 years  2.36  0.05  3.13  1.10–8.93  0.03  Coronary malperfusion  20.5  0.003  31.69  2.99–335.87  0.004  Bowel malperfusion  9.42  0.09        Peripheral malperfusion  6.18  0.001  5.78  1.68–19.86  0.005  Moderate/severe renal dysfunction  6.23  <0.001  3.61  1.14–11.46  0.03  CI: confidence interval. Follow-up was 100%, and the median follow-up time was 10.5 (interquartile range 4.1–12.8) months. During follow-up, 1 patient died due to mediastinal infection. Except for the 2 patients who required RRT preoperatively, de novo RRT was not observed in other patients during the follow-up period. According to follow-up aortic CTA, complete closure or total thrombosis of the false lumen along the stented portion was observed in all patients. Along the distal portion of the descending aorta, complete closure of the false lumen was observed in 31 (24.4%) patients. Among the other patients, patency or partial thrombosis of the false lumen still existed. Both bilateral renal arteries arose from the true lumen in 22 (22.9%) patients and among the remaining patients, only a unilateral renal artery arose from the true lumen. DISCUSSION We found that moderate and severe renal dysfunction was an independent risk factor that predicted the need for postoperative RRT. Additionally, moderate and severe renal dysfunction, together with age >60 years, coronary malperfusion and peripheral malperfusion, were associated with an increased in-hospital mortality. Measurement of serum creatinine levels is a primary test for screening of renal dysfunction. However, because serum creatinine levels are affected by various parameters, including age, sex, muscle mass and metabolic level, their ability to identify renal dysfunction patients is limited [14, 15]. Huynh et al. [16] also found that eGFR is a better parameter than serum creatinine to predict the risk of mortality after thoraco-abdominal aortic surgery. Therefore, we also used the eGFR to evaluate renal function in this study. The Chronic Kidney Disease Epidemiology Collaboration equation was used because of its superior accuracy in categorizing the risk for mortality [17]. Okada et al. [10] found that in elective TAR, patients with a lower eGFR had significantly higher hospital mortality and more morbidity, including postoperative RRT. The cut-off value for the requirement of postoperative RRT was 26.0 ml/min/1.73 m2 in the previous study. However, in another study by Imasaka et al. [18], an eGFR lower than 60.0 ml/min/1.73 m2 predicted postoperative RRT in patients with acute AAD. In this study, mild and severe renal dysfunction was associated with postoperative RRT, and the cut-off value was 70 ml/min/1.73 m2. Aortic dissection only accounted for 10.5% of all patients in the study by Okada et al. [10] and in the study by Imasaka et al. [18], and less than 60% of patients underwent TAR. However, approximately 90% of patients in our AAD cohort underwent TAR. Postoperative acute kidney injury is a common complication in patients who undergo TAR under circulatory arrest [19]. Therefore, patients in this study were more likely to experience renal dysfunction postoperatively. Consequently, the discrepancy concerning cut-off values among studies may be partly caused by the heterogeneity among different patient cohorts. A higher stage of preoperative renal dysfunction was identified as one of the risk factors for in-hospital mortality in our study. Furthermore, we found that in-hospital mortality of patients with mild preoperative renal dysfunction was similar to that in patients in the normal group. Therefore, we suggest that only moderate and severe renal dysfunction increases risk of in-hospital death. We observed that in the severe group, 2 patients who survived underwent preoperative RRT, which might have contributed to the better results compared with the other 2 patients who died. Although emergent operation was intended for acute dissection at our institution, for patients with preoperative chronic kidney disease and extremely low eGFR, delay in operation and preoperative RRT might relieve patients from severe electrolyte disturbance and overload of inflammatory factors, thus increasing the safety of surgery. Ischaemia of the lower limbs and important organs is common in patients with AAD [20]. Malperfusion syndrome was found to be a risk factor for increased mortality by a multicentre registry study [4, 21]. In this study, patients with preoperative malperfusion syndrome were more likely to undergo postoperative RRT. Additionally, coronary malperfusion and peripheral malperfusion were also identified as risk factors for in-hospital death. Coronary ischaemia is a dangerous and insidious condition where concomitant CABG is performed as a salvage technique to prevent intraoperative low cardiac output syndrome. Imasaka et al. [18] suggested that concomitant CABG was useful for preventing postoperative RRT. Rapid restoration of flow in the true lumen can alleviate malperfusion syndrome and decrease postoperative complications [22]. Therefore, surgical revascularization should be considered in patients with preoperative malperfusion syndrome to improve perioperative outcomes. A more conservative strategy with the ascending aorta or hemiarch replacement can be considered to avoid a longer circulatory arrest time and cardiopulmonary bypass (CPB) time resulting from TAR. Previous studies have demonstrated that TAR increases mortality and the incidence of postoperative RRT for patients with acute AAD [18, 20]. Another study suggested that TAR combined with SET implantation could be performed with excellent outcomes [8]. Whether deep hypothermic circulatory arrest in TAR should be performed in patients with preoperative renal dysfunction is unclear. In a previous study, El-Sayed Ahmad et al. [23] suggested that moderate-to-mild (≥28°C) systemic hypothermia combined with selective antegrade cerebral perfusion could provide better protection of visceral organs. In this study, most patients underwent TAR, even in those with moderate renal dysfunction. However, TAR did not increase the incidence of postoperative RRT. Therefore, our strategy for moderate-to-deep hypothermia (rectal temperature 25–28°C) was safe in TAR. The circulatory arrest time in our series was much shorter (<30 min) when compared with previous studies, which may have contributed to the better outcome. However, in patients with severe renal dysfunction, hemiarch replacement instead of TAR was performed in 3 of 4 patients. Although TAR improves the long-term outcome, hemiarch replacement might be more appropriate for patients in an extremely poor condition. Hybrid total arch repair without deep hypothermic circulatory arrest has been shown to reduce the risk of postoperative complications [24]. Therefore, for patients with moderate and severe renal dysfunction, especially for those experiencing pre-existing kidney disease, a hybrid surgical strategy might be considered in future practice. Because most patients in this study underwent TAR, we could not compare its effect on perioperative outcomes with other techniques. Further studies are required to identify the appropriate surgical strategy for patients with preoperative renal dysfunction. We further evaluated early outcomes for patients with preoperative renal dysfunction. Although patients with moderate or severe renal dysfunction had a higher risk of postoperative RRT and in-hospital death, those who survived had excellent early outcomes. Except for the 2 patients who underwent preoperative RRT, no patients required RRT after discharge, even those who experienced moderate preoperative renal dysfunction. In this cohort, the major causes of renal dysfunction were acute mechanism including shock, hypovolaemia, malperfusion and low cardiac output. These results suggested that renal function could recover after the removal of acute factors by operation and generally did not deteriorate after discharge. Follow-up aortic CTA showed that restoration of kidney blood supply was sufficient in most patients. Considering that the average age of patients with AAD in China is younger when compared with patients included in The International Registry of Acute Aortic Dissection (IRAD) [25], TAR combined with SET implantation is reasonable for obliterating a false lumen and improving postoperative results. Further follow-up is required to assess the mid-term and long-term outcomes. Limitations This work is an observational and retrospective study. Therefore, the lack of randomization could have led to bias of our the results. Additionally, our single-centre experience might not apply to other situations. In addition, this study only discussed results of a 1-year cohort, and the number of cases were limited. Limiting the events to malperfusion syndrome, elderly patients and so on might influence the validity of the logistic regression analysis. Furthermore, this study mainly focused on perioperative outcomes. Therefore, further studies are required to evaluate the effect of preoperative renal dysfunction on mid-term and long-term outcomes for patients with AAD. CONCLUSIONS Preoperative renal dysfunction is a risk factor for postoperative RRT, and eGFR is a useful parameter for predicting the requirement for postoperative RRT. Although an increased stage of renal dysfunction is associated with a higher in-hospital mortality, mild renal dysfunction does not reduce the safety of TAR and the use of SET for AAD. In addition to renal dysfunction, age >60 years, coronary malperfusion and peripheral malperfusion are also risk factors for in-hospital death. Our surgical strategy for patients with AAD and mild preoperative renal dysfunction is associated with excellent early outcomes. Funding This work was supported by Major Disease Joint Project of Shanghai Municipal Health system [2014ZYJB0402]. Conflict ofinterest: none declared. REFERENCES 1 Hillis GS, Croal BL, Buchan KG, Ei-Shafei H, Gibson G, Jeffrey RR et al.   Renal function and outcome from coronary artery bypass grafting: impact on mortality after a 2.3-year follow-up. Circulation  2006; 113: 1056– 62. Google Scholar CrossRef Search ADS PubMed  2 Thourani VH, Chowdhury R, Gunter RL, Kilgo PD, Chen EP, Puskas JD et al.   The impact of specific preoperative organ dysfunction in patients undergoing aortic valve replacement. Ann Thorac Surg  2013; 95: 838– 45. 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Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)

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European Journal of Cardio-Thoracic SurgeryOxford University Press

Published: Apr 17, 2018

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