| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
J Thorac Cardiovasc Surg 2009;137:304-308
© 2009 The American Association for Thoracic Surgery
Acquired Cardiovascular Disease |
a Department of Anesthesiology, Tehran Heart Center, Medical Sciences/University of Tehran, Tehran, Iran
b Department of Cardiothoracic Surgery, Tehran Heart Center, Medical Sciences/University of Tehran, Tehran, Iran
c Department of Clinical Research, Tehran Heart Center, Medical Sciences/University of Tehran, Tehran, Iran
Received for publication May 5, 2008; revisions received June 30, 2008; accepted for publication August 4, 2008. * Address for reprints: Mahdi Najafi, MD, Assistant Professor of Anesthesiology, North Kargar St, 1411713138, Tehran Heart Center, Tehran University of Medical Sciences, Tehran, Iran. (Email: najafik{at}sina.tums.ac.ir).
 |
Abstract |
|---|
 Top Abstract IntroductionMethodsResultsDiscussionLimitationsConclusionReferences |
|---|
Methods: Using our database, we conducted a retrospective review of the records of all 11,884 patients aged 21 years or older undergoing pure bypass grafting who required cardiopulmonary bypass. Preoperative renal function was categorized as normal renal function (serum creatinine 
1.1 mg/dL and creatinine clearance > 60 mL/min), occult renal insufficiency (serum creatinine 1.1 mg/dL and creatinine clearance 60 mL/min), mild renal insufficiency (1.1 mg/dL < serum creatinine 1.5 mg/dL and creatinine clearance 60 mL/min) or moderate renal insufficiency (serum creatinine > 1.5 mg/dL and creatinine clearance 60 mL/min).
Results: Out of 11,884 patients in the sample, 7856 (66.1%) had normal renal function, and 706 (5.9%) had occult renal insufficiency. The rate of postoperative mortality, renal failure, atrial fibrillation, prolonged ventilation, intra-aortic balloon pump usage, and prolonged hospital stay (>7 days) was higher in patients with occult renal insufficiency than in the normal group in univariable analysis. Multivariable logistic regression analysis demonstrated that patients with occult renal insufficiency compared with the group with normal renal function were at higher risk for mortality (odds ratio = 2.59, 95% confidence interval 1.15–5.86; P = .022) and prolonged hospital stay (>7 d) (odds ratio = 1.30, 95% confidence interval 1.08–1.57; P = .005).
Conclusions: To identify higher-risk patients requiring special intensive care, and in whom new interventions can be performed to improve outcome, we recommend the preoperative calculation of creatinine clearance, especially in older women with a lower body mass index.
|
Introduction |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionLimitationsConclusionReferences |
|---|
With the rapid rise in the aged population, more patients with renal insufficiency (RI) are being referred for coronary artery bypass graft (CABG) operations.3 Patients with impaired renal function undergoing CABG surgery present a higher operative risk, a higher incidence of morbidity and need for dialysis, and prolonged hospital length of stay after CABG.4
Elevated serum creatinine (Cr) level is not a reliable screening test for renal impairment because it has important limitations. Serum Cr level varies with factors aside from renal function, such as age, sex, muscle mass, hypertension, and metabolism; therefore, it can remain within the normal range even when renal function is significantly impaired.5 Creatinine clearance (CrCl), as an alternative measure of preoperative renal reserve, is the most useful clinical estimate of glomerular filtration rate. Direct measurement of CrCl is more accurate, but cumbersome, and not a possible option in routine clinical practice or large clinical studies.6 Using prediction formulas that estimate glomerular filtration rate with moderate precision and accuracy would be a practical solution. Among the formulas, the Cockcroft–Gault equation was chosen because it is calculated by readily available clinical data and is reasonably associated with measured CrCl in patients with cardiac disease.7,8
The aims of this study were (1) to define the preoperative demographics as well as intraoperative and postoperative characteristics of patients undergoing CABG who have occult RI (serum Cr 1.1 mg/dL and CrCl 60 mL/min) and (2) to examine the hypothesis whether CABG patients with occult RI incur greater morbidity and mortality than CABG patients with normal renal function (NRF) (serum Cr 1.1 mg/dL and CrCl > 60 mL/min).
|
Methods |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionLimitationsConclusionReferences |
|---|
Because of the retrospective nature of the study, requirement for written informed consent was waived by the ethics committee. All entries were based on definitions of the Society of Thoracic Surgeons. Patients' data included the following variables: age, sex, body mass index (BMI), history of smoking, hypertension, peripheral vascular disease, chronic obstructive pulmonary disease, and cerebrovascular accident, as well as left ventricular ejection fraction, left main coronary artery involvement, and number of significant coronary arteries involved. The operation data, such as aortic crossclamp time and use of intra-aortic balloon pump, and the outcome of CABG, including in-hospital mortality and postoperative complications such as stroke, renal failure, prolonged ventilation, prolonged length of stay (>7 days), and atrial fibrillation, were also gathered.
Postoperative renal failure was defined as acute or worsening renal failure after CABG resulting in one or more of the following: increase of serum Cr more than 2 mg/dL (176.8 µmol/L) or a new requirement for dialysis. Prolonged ventilation was defined as pulmonary insufficiency requiring ventilator support including but not limited to causes such as adult respiratory disease syndrome, pulmonary edema, and/or any patient ventilated more than 24 hours postoperatively. Postoperative atrial fibrillation was defined as new-onset atrial fibrillation necessitating treatment for symptoms or hemodynamic compromise that did not include recurrence of atrial fibrillation that had been present preoperatively. Postoperative stroke was defined as any neurologic deficit of abrupt onset resulting from a disturbance in cerebral blood supply documented by the neurologist on the basis of the brain imaging pictures that did not resolve within 24 hours.
Renal function was assessed by serum Cr, and CrCl was estimated by the Cockcraft–Gault equation.7,8 In all patients, serum Cr level in milligrams per deciliter was determined preoperatively.
The Cockroft–Gault equation was selected as the most consistently favored algorithm to calculate preoperative and postoperative CrCl.9 The following equation was used for men:
.
Units are weight (kg), age (years), and serum Cr (mg/dL).
The proportion of muscle mass on body weight is relatively lower in women than in men. Therefore, the calculated value of CrCl was multiplied by the factor of 0.85 in female patients.
The Cockroft–Gault equation was adjusted for body surface area (BSA) by multiplying by (1.73/BSA) mL · min–1 per 1.73 m2, with BSA calculated by the following DuBois formula: BSA (m2) = (weight [kg]) 0.425 · (height [cm]) 0.725 · 0.007184.10,11
Patients were divided into four categories on the basis of preoperative renal function as follows: NRF (serum Cr 1.1 mg/dL and CrCl > 60 mL/min), occult RI (serum Cr 1.1 mg/dL and CrCl 60 mL/min), mild RI (1.1 mg/dL < serum Cr 1.5 mg/dL and CrCl 60 mL/min), or moderate RI (serum Cr >1.5 mg/dL and CrCl 60 mL/min). Patients with severe preoperative RI, defined as serum Cr greater than 3.4 mg/dL, were excluded.
Statistical Analysis
Numerical variables were presented as mean ± SD, and categorized variables were summarized by absolute frequencies and percentages in parentheses. Continuous variables were compared by the Student's t test and categorized variables were compared by the 
2 test (or Fisher's exact test as required) across two groups (with NRF and with occult RI).
Multivariable logistic regression models were established to compare outcome variables including postoperative renal failure, mortality, and prolonged hospital stay across four groups with the presence of confounders such as age, sex, and BMI. Variables entered into the multivariable model if the P value in the univariable analysis was found to be less than or equal to .15. For each analysis, patients with NRF served as the reference group against which all others were compared. All analyses were conducted with SPSS software (version 13.0; SPSS, Inc, Chicago, Ill) and version 9.1 of the SAS System for Windows (SAS Institute, Inc, Cary, NC). All P values were 2-tailed.
|
Results |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionLimitationsConclusionReferences |
|---|
|
1.1mg/dL) was found to have CrCl of 60 mL/min or less. As shown in Table 1, patients with occult RI were more likely to be women, older, and had a lower BMI than patients with NRF (All P values < .001). Patients with occult RI had also more frequent preoperative comorbidities such as hypertension, peripheral vascular disease, and triple coronary vessel disease, whereas cigarette smoking was less common in the occult RI group than in the NRF group. Operative data are also shown in Table 1. Rate of intra-aortic balloon pump use was significantly higher in the occult RI group than in the NRF group. Patients with NRF had a longer aortic crossclamp time than did the occult RI group (43.3 ± 13.4 vs 41.3 ± 14.0 minutes; P < .001).
Postoperative results are listed in Table 2 . Patients with occult RI had more than threefold increased rate of in-hospital mortality and nearly threefold increased prevalence of postoperative RI as compared with patients with NRF (P < .001 and P = .020, respectively).
|
|
On the basis of conventional methods of postoperative RI definition by using serum Cr cutoff, only patients with moderate RI were at higher risk of postoperative renal failure compared with the group with NRF. However, patients with occult RI or mild RI did not show a significantly higher risk of postoperative renal failure as compared with patients with NRF.
|
Discussion |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionLimitationsConclusionReferences |
|---|
Renal function is an important determinant of in-hospital mortality in cardiac surgery,13 and when it is severe enough to require dialysis, morbidity and mortality are markedly increased despite dialysis and supportive intensive care.14 However, there is modest information on the effects of lesser degrees of renal failure on operative outcome.15,16 Moreover, renal function was mostly detected by checking the serum Cr levels as a diagnostic test.16,17 However, use of serum Cr has been questioned in several reports as it can be normal even when renal function is impaired, and it may underestimate mild-to-moderate degrees of RI.18,19
Browner, Li, and Mangano20 initially suggested impaired renal function as a significant predictor of postoperative mortality after noncardiac surgery. More recently, Mangano and associates1 reported outcomes in more than 2200 patients undergoing CABG with or without valvular surgery, revealing that 14% of their study population had at least some degrees of impaired renal function before myocardial revascularization and that the pre-existing mild renal failure (preoperative serum Cr of 1.4–2.0 mg/dL equivalent to 123.8–176.8 µmol/L) was an independent predictor of developing acute renal failure after CABG surgery.
In contrast to our study, Wijeysundera and associates5 reported that risk of acute renal failure necessitating renal replacement therapy is higher in the group with occult RI (serum Cr 100 µmol/L and CrCl 60 mL/min), and there was no significant difference between the occult and mild RI groups with regard to risk of renal replacement therapy. One reason for that could be the fact that their criteria for RI definition were stricter than ours.
Wijeysundera and associates5 also showed that patients with occult RI were more likely to be elderly women with lower BMI, which was similar to our findings.
Data from our analyses confirm and extend most of these observations.
We suggested that the risk of postoperative mortality and prolonged hospital stay increases when CrCl falls below 60 mL/min, even if serum Cr is in the normal range. In addition, although in our study patients with occult RI experienced a higher rate of acute renal failure than did the NRF group, calculation of CrCl was only related to the outcomes in univariable analysis and not in the adjusted multivariable model. As stated before, it seems that our criteria for definition of post-CABG renal failure should be restricted and even CrCl estimation taken into account.
|
Limitations |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionLimitationsConclusionReferences |
|---|
Finally, out hospital complications and mortality could not be assessed owing to lack of follow-up data in the hospital records. |
Conclusion |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionLimitationsConclusionReferences |
|---|
|
Acknowledgments |
|---|
|
References |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionLimitationsConclusionReferences |
|---|
This article has been cited by other articles:
|
|
 |
|
  A. Miceli, V. D. Bruno, R. Capoun, F. Romeo, G. D. Angelini, and M. Caputo Occult renal dysfunction: a mortality and morbidity risk factor in coronary artery bypass grafting surgery J. Thorac. Cardiovasc. Surg., March 1, 2011; 141(3): 771 - 776. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ANN THORAC SURG | ASIAN CARDIOVASC THORAC ANN | EUR J CARDIOTHORAC SURG |
| J THORAC CARDIOVASC SURG | ICVTS | ALL CTSNet JOURNALS |
