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J Thorac Cardiovasc Surg 2008;135:915-922
© 2008 The American Association for Thoracic Surgery
Surgery for Acquired Cardiovascular Disease |
a Department of Cardiothoracic Surgery, Mount Sinai School of Medicine, New York, NY
b Division of Nephrology, Mount Sinai School of Medicine, New York, NY
Received for publication June 19, 2007; revisions received August 22, 2007; accepted for publication September 12, 2007. * Address for reprints: Farzan Filsoufi, MD, Department of Cardiothoracic Surgery, Mount Sinai School of Medicine, 1190 Fifth Ave, Box 1028, New York, NY 10029. (Email: Farzan.filsoufi{at}mountsinai.org).
| Abstract |
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Methods: This is a retrospective analysis of prospectively collected data for 6694 patients, including 245 (3.7%) patients with end-stage kidney failure requiring dialysis who underwent cardiac surgery between January 1998 and September 2006. Potential predictors of hospital mortality, complications, and late survival were retrospectively analyzed by using multivariate regression models.
Results: Patients with end-stage kidney failure requiring dialysis had a 3.9-times higher hospital mortality rate compared with other cardiac surgery patients (12.7% vs 3.6%, P < .001). Patients with end-stage kidney failure requiring dialysis were younger but presented with more comorbidities and more severe cardiac disease than the control group. After adjusting for potential confounding factors, end-stage kidney failure requiring dialysis was identified as a predictor of hospital mortality (odds ratio, 3.1; P < .001). Patients with end-stage kidney failure requiring dialysis also had an increased risk of postoperative sepsis (odds ratio, 2.7; P < .001) and respiratory failure (odds ratio, 2.0; P < .001). Peripheral vascular disease was an independent predictor of hospital mortality in patients with end-stage kidney failure requiring dialysis (odds ratio, 2.5; P = .001). Long-term survival was significantly decreased in patients with end-stage kidney failure requiring dialysis compared with that seen in the control group (1-year and 5-year survival: 72.3% ± 3.3% and 39.0% ± 4.5% vs 94.2% ± 0.3% and 83.2% ± 0.6%, P < .001). Peripheral vascular disease (odds ratio, 2.69; P = .008) and previous stroke (odds ratio, 4.37; P < .001) were independent risk factors of late mortality in the subgroup of patients with end-stage kidney failure requiring dialysis.
Conclusions: Preoperative renal failure requiring dialysis is associated with a significant increase in hospital mortality, postoperative sepsis, and respiratory failure in patients undergoing cardiac surgery. In these patients long-term survival is particularly reduced in the presence of advanced atherosclerotic disease.
| Introduction |
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| Materials and Methods |
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Data Collection
Clinical variables were prospectively entered into the New York State Department of Health (State Cardiac Advisory Committee) data registry. The New York State Department of Health data registry represents a mandatory, verified, peer-reviewed data collection system including all adult cardiac surgery procedures in the state of New York and records and analyzes data in a strictly supervised and widely reported fashion.4
Patient demographics and risk factors, operative information, and postoperative outcome data were retrospectively analyzed. Additional information was obtained from patient charts when necessary. Appendix 1 shows preoperative variables and their definitions. In addition, the logistic EuroSCORE was used for risk stratification.5
The EuroSCORE is a risk-stratification system using multiple preoperative risk factors to predict operative mortality. Patients were stratified according to EuroSCORE as follows: EuroSCORE of 9% or less, low to moderate risk; EuroSCORE of greater than 9% to 25%, high risk; and EuroSCORE of greater than 25%, very high risk.5
Outcome measures in this study included hospital mortality, major postoperative complications, and length of stay in the hospital (Appendix 1). Follow-up survival information was obtained by cross-matching the patient's social security number with the Web-based social security death index.
Operative Procedures and Perioperative Management
Hemodialysis was performed in all patients in the ESRD group 12 to 24 hours before surgical intervention. All procedures were performed by using standard anesthetic and surgical techniques. A small skin incision and a full or partial sternotomy were performed in patients undergoing valve, CABG, or aortic surgery procedures involving the ascending aorta or the aortic arch. Descending thoracic aortic surgery was performed through a left thoracotomy approach. After systemic heparinization, cardiopulmonary bypass (CPB) was instituted between the ascending aorta and either the right atrium by using a 2-stage cannula or both venae cavae. During CPB, a minimum flow of 2.5 L · min–1 · m–2 and mean arterial pressures of approximately 60 mm Hg (70 mm Hg in patients with peripheral vascular disease [PVD]) were maintained. Cardioplegia with high-potassium cold blood was administered in an antegrade fashion, a retrograde fashion, or both for myocardial protection. In patients undergoing valve surgery, further myocardial protection was obtained with mild-to-moderate systemic cooling (28°C–30°C). Procedures involving the aortic arch were performed during deep hypothermic circulatory arrest. After the completion of CPB, protamine was administered based on the heparin level. Intraoperative variables used in this study are reported in Appendix 1. Patients with ESRD underwent postoperative hemodialysis routinely on the second day after surgical intervention or earlier if volume overload or hyperkalemia was present.
Statistical Analysis
Normally distributed continuous variables are presented as means ± standard deviations and otherwise as medians and interquartile ranges. Categorical variables are shown as the percentage of the sample. The
2 test was used to evaluate potential confounders of the relationship between ESRD and hospital mortality and morbidities in the entire patient population. Stepwise multivariate logistic regression was then performed to assess the influence of ESRD as an independent risk factor for hospital mortality and postoperative morbidities.6
The potential confounders included age, sex, obesity (body mass index >30 kg/m2), ejection fraction, congestive heart failure, previous cardiac procedure, history of diabetes mellitus, hypertension, history of myocardial infarction, acute myocardial infarction, chronic obstructive pulmonary disease, PVD, hemodynamic instability, and type of operative procedure (isolated CABG, valvular surgery, combined valve/CABG, and aortic procedures). Long-term survival was analyzed by using Kaplan–Meier survival curves. Differences in patient characteristics were controlled with Cox proportional hazard analysis. The statistical analyses were performed with SPSS 15 (SPSS, Inc, Chicago, Ill).
| Results |
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Morbidity
In univariate analysis patients with ESRD presented significantly more often with respiratory failure (P < .001), sepsis (P < .001), and gastrointestinal complications (P < .001) compared with the control group. Variables associated with postoperative morbidities in univariate analysis were introduced into stepwise logistic regression analysis. In this multivariate analysis the correlation between ESRD and the occurrence of respiratory failure and sepsis remained statistically significant. However, the correlation between dialysis-dependent renal failure and gastrointestinal complications disappeared (
Table 3). The mean length of stay in the hospital among surviving patients was 13 ± 18 days. The mean length of stay among patients with ESRD was 25 ± 34 days compared with 12 ± 17 days in the control group (P < .001).
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| Discussion |
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Mortality
Previous studies have identified ESRD as a major risk factor for postoperative morbidity and mortality. In 2000 Horst and coworkers12
published a review of the literature including 20 studies with a total of 863 dialysis-dependent patients who underwent all types of cardiac procedures. In this review the overall operative mortality was 12.5%. In their multicenter study among patients undergoing CABG from northern New England, Liu and colleagues9
reported a 3-times higher adjusted mortality rate in dialysis-dependent patients (9.6%) compared with those with normal renal function (3.1%). Our experience confirmed these findings: the adjusted risk of hospital mortality was more than 3-times higher in patients with ESRD. Hospital mortality rate was increased regardless of the underlying procedure. The highest mortality rate, however, was observed in patients undergoing valvular surgery and combined valve/CABG procedures. This finding supports 2 small previous studies that focused primarily on operative mortality in patients who underwent valve surgery.3,12
In these 2 studies crude mortality was 3- to 4-times higher in patients undergoing valvular surgery compared with values in those who underwent isolated CABG. One possible explanation for the poorer outcome in these patients is a delay in surgical intervention because of an underestimation of valvular heart disease.12
In patients with ESRD, typical presentations of valvular heart disease caused by volume overload, such as shortness of breath, effusions, and other symptoms of congestive heart failure, can be concealed by dialysis, making accurate diagnosis difficult.12,13
In addition, because of known high operative risk, some of these patients might be referred late for cardiac surgery with advanced valvular lesions, including extensive calcification and impaired left ventricular function. While performing multivariate analysis in the ESRD subgroup, we were able to identify PVD as a predictor of hospital mortality. Dialysis-dependent patients with PVD were 2.5-times more likely to experience hospital mortality compared with patients with ESRD without PVD. This is probably a manifestation of the extent of atherosclerotic disease in these patients affecting multiple organs. These findings suggest that earlier detection of cardiac disease, as well as other associated atherosclerotic diseases, might lead to an earlier referral and potentially improve operative outcome in this high-risk population.
Morbidity
A number of previous studies reported an association of ESRD with major postoperative complications, such as reoperation for bleeding and coagulation disorders, stroke, respiratory failure, mediastinitis, and sepsis.9,12,14
We identified ESRD as an independent predictor of respiratory failure (OR, 2.0; 95% CI, 1.4–2.8; P < .001) and sepsis (OR, 2.7; 95% CI, 1.6–4.3; P < .001). Gastrointestinal complications showed an association with ESRD in univariate analysis, but this association disappeared in multivariate analysis. The increased risk for perioperative infectious complications in patients with ESRD might be explained by an immune-compromised state caused by uremia, frequent dialysis, diabetes, or steroid therapy for autoimmune causes of renal failure. However, despite the increased risk of postoperative septic complications, we did not observe a significant difference in the rate of mediastinitis between patients undergoing dialysis and our general patient population. This might be explained by a large number of patients who underwent valvular or aortic surgery in our series, which usually carries a lower risk of postoperative mediastinitis compared with that of CABG.15
In contrast to previous studies,9,16
we were not able to show an association between ESRD and postoperative stroke (3.3% in patients with ESRD vs 2.5% in the control group, P = .273). The risk of stroke in patients with dialysis undergoing cardiac surgery is related to the burden of atherosclerotic disease, which predisposes patients with ESRD to thrombembolic events and ischemic injury from low perfusion pressure during CPB.16
Our finding of a relatively low stroke rate (3.3%) in this patient population compared with previous reports (6% to 7%) is probably related to the fact that we routinely apply epiaortic scanning before manipulation and cannulation of the ascending aorta in all patients, use the axillary artery instead of the femoral artery as an inflow for arterial cannulation in patients undergoing complex aortic surgery, and perform off-pump procedures in patients undergoing CABG at risk.17
Another important adjunct is that we maintain high perfusion pressure (>70 mm Hg) during CPB in all patients with PVD or patients older than 70 years.
In contrast to some previous studies, we did not observe an association between ESRD and postoperative bleeding complications. Previous studies have reported a rate of postoperative bleeding in the range of 3% to 11% and associated this event with platelet dysfunction and coagulation defects caused by uremia and mechanical alterations of blood cells during dialysis.18
Although this study was not designed to determine the cause of reduced postoperative bleeding, the low rate of bleeding complications might be explained by the use of antifibrinolytic agents, such as
-aminocaproic acid during CPB. In addition, we currently perform a thromboelastogram in these patients at the completion of CPB, with a low threshold for the transfusion of platelets in patients with abnormal findings and clinical signs of bleeding.
Long-term Survival
Few data exist with respect to long-term survival of patients with ESRD after cardiac surgery. In their review of the literature, Frenken and Krian3
were able to identify 5 case series with a total of 97 patients and reported a 5-year survival between 39% and 67%. In the subgroup of patients undergoing valve procedures, the 5-year survival was only 39%. Franga and coworkers,19
in their series of 44 patients, reported a 3-year and 5-year survival of 64% and 32%, respectively. Finally, Jault and colleagues20
followed 99 patients who underwent cardiac surgery between 1980 and 1998 and observed a survival of 47% at 6 years. In our series of 214 discharged patients, we observed 1-year, 3-year, and 5-year survivals of 72.3% ± 3.3%, 53.3% ± 4.0%, and 39.0% ± 4.5% respectively. Late survival was not different when patients were stratified by underlying procedure. The importance of PVD and history of stroke for the outcome of patients with ESRD after cardiac surgery has not previously been demonstrated. In our study previous stroke and PVD were strong independent predictors of late mortality. Three-year survival was 14.1% ± 7.2% and 32.8% ± 7.8% for patients with previous stroke and PVD, respectively. These observations were confirmed when patients were stratified by predicted mortality by using EuroSCORE. These findings confirm that end-stage renal failure and associated atherosclerotic disease negatively affect late outcome after cardiac surgery. Therefore systematic preoperative work-up for detection of coexisting atherosclerotic disease is crucial to optimize patient selection to improve early and late outcome of patients with ESRD undergoing cardiac surgery.
| Limitations |
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| Appendix 1 |
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CABG, Coronary artery bypass grafting.
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