Home About us Current issue Back issues Submission Instructions Advertise Contact Login   

Search Article 
Advanced search 
Saudi Journal of Kidney Diseases and Transplantation
Users online: 1476 Home Bookmark this page Print this page Email this page Small font sizeDefault font size Increase font size 

ORIGINAL ARTICLE Table of Contents   
Year : 2010  |  Volume : 21  |  Issue : 6  |  Page : 1081-1087
Impact of mild renal impairment on early postoperative mortality after open cardiac surgery

1 Department of Nephrology, Mubarak Al Kabeer Hospital, Kuwait
2 Department of Internal Medicine, Mubarak Al Kabeer Hospital,Ministry of Health, Kuwait
3 Department of Anesthesia, Critical Care-Chest Disease Hospital, Kuwait

Click here for correspondence address and email

Date of Web Publication4-Nov-2010


Preoperative severe renal impairment is included in the risk scores to predict out­come after open cardiac surgery. The purpose of this study was to assess the impact of pre­operative mild renal impairment on the early postoperative mortality after open heart surgery. Data of all cases of open cardiac surgery performed from January 2005 to June 2006 were collec­ted. Cases with preoperative creatinine clearance below 60 mL/min were excluded from the study. Data were retrospectively analyzed to find the impact of renal impairment on short-term outcome. Of the 500 cases studied, 47 had preoperative creatinine clearance between 89-60 mL/min. The overall mortality in the study cases was 6.8%. The mortality was 28.7% in those who developed postoperative ARF, 33.3% in those who required dialysis and 40.8% in those with preoperative mild renal impairment. Binary logistic regression analysis showed that female gender (P = 0.01), preoperative mild renal impairment (P = 0.007) as well as occurrence of multi organ failure (P < 0.001) were the only independent variables determining the early postoperative mortality after cardiac surgeries. Among them, preoperative mild renal impairment was the most significant and the best predictor for early postoperative mortality after cardiac surgery. Our study suggests that renal impairment remains a strong predictor of early mortality even after adjustment for several confounders.

How to cite this article:
Ghani A A, Al Nasar M, Al Shawaf E, Vislocky I. Impact of mild renal impairment on early postoperative mortality after open cardiac surgery. Saudi J Kidney Dis Transpl 2010;21:1081-7

How to cite this URL:
Ghani A A, Al Nasar M, Al Shawaf E, Vislocky I. Impact of mild renal impairment on early postoperative mortality after open cardiac surgery. Saudi J Kidney Dis Transpl [serial online] 2010 [cited 2020 Oct 24];21:1081-7. Available from: https://www.sjkdt.org/text.asp?2010/21/6/1081/72295

   Introduction Top

Cardiovascular disease remains the number one cause of mortality in general population. Renal Impairment (RI), ranging from new onset of mild reversible impairment to irreversible end-stage renal disease (ESRD) requiring renal replacement therapy, has been found to be a significant non-traditional risk factor for car­diovascular death and all cause mortality. [1],[2] Both renal insufficiency and ESRD are impor­tant risk factors for patients undergoing car­diac surgery. [3] The identification of preopera­tive risk factors for adverse outcome after cardiac surgery is an important component of preoperative care. It identifies high-risk-patients requiring special care and in whom, new inter­ventions can be developed to improve out­come. [4] Several studies have assessed the risk associated with mild or moderate RI in pa­tients undergoing coronary artery bypass sur­gery (CABG). [5],[6],[7] In these studies, renal func­tion has been defined based on levels of serum creatinine and not according to calculated creatinine clearance (Cr Cl).

Plasma creatinine level is a highly specific marker of RI. However, it may be insensitive to mild and moderate degrees of RI because it depends on many non-renal factors including muscle mass, gender and metabolism. [8],[9] Recent data demonstrated that estimated Cr Cl is a very powerful predictor of outcome in patients with acute myocardial infarction and is more accurate in this respect than serum creatinine. [10],[11]

The aim of the present study was to assess the impact of mild RI (preoperative estimated Cr Cl 89-60 mL/min) on the short-term out­come (30 days) after open heart surgeries.

   Subjects and Methods Top

A retrospective single center study was con­ducted in the Kuwait chest disease hospital from January 2005 to June 2006. Data from all cases who underwent open cardiac surgery was collected including: age, weight, height, gender, presence of congestive heart failure defined as ejection fraction below 35%, pre­sence of diabetes mellitus (random plasma sugar level more than 7 mmol/dL and/or his­tory of use of hypoglycemic agents), preope­rative estimated Cr Cl using Cockcroft and Gault equation, [12] hypertension, chronic obs­tructive airway disease, and recent myocardial infarction (within one month of surgery). Ope­rative data including type of surgery, extra­corporeal circulation time (ECCT), cross clamp time (C-clamp) and postoperative data inclu­ding the need of vasopressors, prolonged me­chanical ventilation > 48 hours, presence of multi organ failure (MOF) defined as more than two organ/system failure, postoperative hemorrhage and/or infection, development of postoperative acute renal failure (ARF) defined as more than 25% increase of serum creatinine from preoperative levels, the need for dialysis and the early postoperative mortality within the first 30 days post surgery were also collected. Preoperative mild RI was defined as Cr Cl 89­60 mL/min. Patients with Cr Cl less than 60 mL/min, those with ESRD requiring dialysis, those on mechanical ventilator before surgery and patients with missing data were excluded from the study.

   Statistical Methods Top

Data were analyzed using SPSS for windows version 13 (SPSS, Inc, Chicago, IL). Numerical variables were expressed as mean ± SD, whereas categorical variables were expressed as frequencies and percentages. Fisher exact test was used for univariate analysis using risk ratio and 95% confidence interval (CI). Logistic regression analysis was used for multivariate analysis of statistically significant variables in the univariate analysis. Results were consi­dered statistically significant if the P value was < 0.05.

   Results Top

A total of 885 cases underwent open heart surgery from January 2005 to June 2006 of whom, 385 cases had one or more exclusion criteria and were excluded from the study. Five hundred cases with preoperative Cr Cl above 60 mL/sec were enrolled in the study which included 369 males (73.8%) and 131 females (26.2%). The patients' clinical charac­teristics are described in [Table 1]. The overall mortality in the study cases was 6.8%. The mortality was 28.7% in those who developed postoperative ARF, 33.3% in those who re­quired dialysis and 40.8% in those with preoperative mild renal impairment [Figure 1]. Univariate analysis showed that female gender (P = 0.02), hypertension (P = 0.02), COAD (P = 0.01), preoperative renal impairment (P < 0.001), EF below 35% (P < 0.001), ECCT > 100 minutes (P = < 0.001), C-clamp time > 60 minutes (P = 0.004), post operative hemo­rrhage (P < 0.001), postoperative infection (P < 0.001), use of more than two vasopressors (P < 0.001), postoperative ARF (P < 0.001), pro­longed mechanical ventilation (P < 0.001) and the presence of MOF (P < 0.001) as factors contributing to early postoperative mortality [Table 2]. Binary logistic regression analysis showed that female gender (P = 0.01), pre­operative mild RI (P = 0.007), as well as MOF (P < 0.001) were the only independent varia­bles determining the early postoperative mortality after cardiac surgeries; among them, mild RI was the most significant and the best pre­dictor [Table 3].
Table 1 :Clinical characteristics of the study patients.

Click here to view
Table 2 :Univariate analysis for factors determining early postoperative mortality after cardiac surgery. (n = 500).

Click here to view
Table 3 :Binary logistic regression analysis for factors determining early mortality after cardiac surgery (n = 500).

Click here to view
Figure 1 :Short-term outcome in patients undergoing cardiac surgery (n = 500).

Click here to view

   Discussion Top

It has been previously established that pa­tients with severe RI such as those requiring dialysis, have poor short-term outcome follo­wing CABG. [13],[14] The two most common risk stratification scoring systems used to estimate perioperative mortality, give a weighting fac­tor only for advanced renal disease or dialysis dependency. [1],[2] The present study established a strong link between preoperative mild RI and postoperative short-term mortality. Multivariate analysis showed that the preoperative Cr Cl is the most important predictor of early post­operative mortality followed by female gender and the presence of postoperative multi organ failure. This is in accordance with previous studies. [5],[15],[16],[17],[18],[19],[20] Hayashida et al reported that RI was the second most important predictor of operative mortality after poor left ventricular failure. [21] Also, Mageed et al [15] reported RI as the second most important predictor of early postoperative mortality after timing of surgery.

The mechanism by which RI contributes to perioperative mortality is unknown, but pa­tients with mild RI had a high prevalence of traditional cardiovascular risk factors including increased levels of inflammatory mediators, [22] hypercoagulability, [22] endothelial dysfunction, [23] arterial stiffness, [24] calcification [25] and left ven­tricular hypertrophy. [26] Moreover, patients with RI have an increased risk of developing ARF, bleeding, strokes and needing prolonged ven­tilation. [27] They are often considered to be im­munocompromised, [28] which may render them less able to recover quickly and has been asso­ciated with greater mortality after cardiac sur­gery. [29]

Most previous studies assessed the associa­tion between renal function and outcome after cardiac surgery by using the plasma creatinine level, but estimated Cr Cl seems to be a better predictor in these patients. [17],[30] Wang et al [30] confirmed that even if lower values of plasma creatinine were used to define renal dysfunc­tion, estimated Cr Cl would remain a better risk predictor in these patients.

Detection of preoperative renal function is important as the presence of RI makes the kidney more vulnerable to ischemia and drug induced toxicity. [15],[31],[32],[33],[34] Thus, estimated pre­-operative Cr Cl could influence perioperative care by trying to improve renal function before surgery and minimizing the exposure to poten­tially nephrotoxic agents before, during and after surgery. Although the impact of these interventions on outcome is unknown, the in­creased morbidity or mortality associated with postoperative deterioration of renal function probably justifies any attempt to minimize perioperative renal insults in patients with pre­existing renal impairment. [32]

Preoperative mild RI is a strong predictor of early postoperative mortality in patients under­going cardiac surgeries. We suggest that all patients scheduled to undergo CABG should have their renal function carefully assessed by using estimated Cr Cl instead of plasma crea­tinine concentration to better determine the risk of early postoperative death at no extra cost or inconvenience to the patient.

   Limitations of the Study Top

First, the study was conducted at a single center and the results might not be applicable to all other centers performing thoracic sur­geries. Second, although the Cockcroft and Gault equation provides an acceptable estimate of Cr Cl in most stable cardiac patients, it may underestimate the GFR, which in turn over­estimates the risk in obese patients and in pa­tients with very low plasma creatinine levels. [35] Additionally, the formula may overestimate

creatinine clearance in hemodynamically un­stable patients with acute renal failure since plasma creatinine levels may not have time to reach its peak and in turn, may underestimate risk prediction.

   References Top

1.Muntner P, He J, Hamm L, et al. Renal insu­fficiency and subsequent death resulting from cardiovascular disease in the United States. J Am Soc Nephrol 2002;13:745-53.  Back to cited text no. 1
2.Henry RM, Kostense PJ, Bos G, et al. Mild renal insufficiency is associated with increased cardiovascular mortality: the Hoorn study. Kidney Int 2002;62:1402-7.  Back to cited text no. 2
3.Albert A, Walter J, Hassanein W, et al. The impact of renal dysfunction on early mortality after cardiac surgery: Evaluating the threshold for an unfavorable creatinine clearance and the role of co-morbidities. Clin Res Cardiol Supp 2007;2:S22-8.  Back to cited text no. 3
4.Ferguson TB, Bradley GH, Peterson ED, et al. A decade of change: risk profiles and out­comes for isolated coronary artery bypass grafting procedures, 1996-1999: a report from STS national Database Committee and the Duke clinical research institute. Ann Thorac Surg 2002;73:480-90.  Back to cited text no. 4
5.Anderson RJ, O' Brein M, MaWhinney S, et al. Renal failure predisposes patients to adverse outcome after coronary artery bypass surgery. VA cooperative Study #5. Kidney Int 1999;55: 1057-62.  Back to cited text no. 5
6.Nakayama Y, Sakata R, Ura M, et al. Long­term results of coronary artery bypass grafting in patients with renal insufficiency. Ann Thorac Surg 2003;75:496-500.  Back to cited text no. 6
7.Weerasinghe A, Hornick P, Smith P, et al. Coronary artery bypass grafting in non-dialysis dependent mild-to-moderate renal dysfunction. J Thorac Cardiovasc Surg 2001;121:1083-8.  Back to cited text no. 7
8.Newman DJ, Price CP. Renal function and metabolites. In: Burits CA, Ashwood ER, eds. Tietz textbook of clinical chemistry, 3rd ed. Philadelphia, PA: WB Saunders, 1999;1204-70  Back to cited text no. 8
9.Duncan L, Heathcote J, Djurdjev O, et al. Screening for renal diseases using serum creatinine: who are we missing? Nephrol Dial Transplant 2001;16:1042-6.  Back to cited text no. 9
10.Boston AG, Kronenberg F, Ritz E, et al. Pre­dictive performance of renal function equation for patients with chronic kidney disease and normal serum creatinine levels. J Am Soc Nephrol 2002;13:2140-4.  Back to cited text no. 10
11.Anavekar NS, Mc Murray JJ, Velazquez EJ, et al. Relation between renal dysfunction and cardiovascular outcomes after myocardial infarction. N Engl J Med 2004;351:1285-95  Back to cited text no. 11
12.Cockcroft DW, Gault MH. Prediction of creatinine clearance from serum creatinine. Nephron 1976;16:31-41.  Back to cited text no. 12
13.Lui JY, Birkmeyer NJ, Sanders JH, et al. Risks of morbidity and mortality in dialysis patients undergoing coronary artery bypass surgery: Northern New England Cardiovascular Disease Study group. Circulation 2000;102:2973-7.  Back to cited text no. 13
14.Clough RA, Leavitt BJ, Morton RJ, et al. The effect of comorbid illness on mortality out­comes in cardiac surgery. Arch Surg 2002; 137:428-32.  Back to cited text no. 14
15.Mageed NA, El Ghoniemy YF. Is renal dys­function a risk factor in patients undergoing cardiac surgery? Mansoura cardio-Thoracic Unit Experience. Int J Anesthesiol 2007;13(1): 1-7.  Back to cited text no. 15
16.Zakeri R, Freemantle N, Barnett V, et al. Rela­tion between mild renal dysfunction and outcomes after coronary artery bypass grafting. Circulation 2005;112:1-270-5.  Back to cited text no. 16
17.Weerasinghe A, Hornick P, Smith P, et al. Coronary artery bypass grafting in non­dialysis-dependent mild-to-moderate renal dysfunction. J Thorac Cardiovasc Surg 2001; 121:1083-9.  Back to cited text no. 17
18.Lok CE, Austin PC, Wang H, et al. Impact of renal insufficiency a short-and long-term outcomes after cardiac surgery. Am Heart J 2004;148:430-8  Back to cited text no. 18
19.Shroyer AL, Grover FL, Edwards FH, et al. 1995 coronary artery bypass risk model: the Society of Thoracic Surgeons Adult Cardiac National Database. Ann Thorac Surg 1998; 65:879-84.  Back to cited text no. 19
20.Higgins TL, Estafanous FG, Loop FD, et al. Stratification of morbidity and mortality outcome by preoperative risk factors in coro­nary artery bypass patients: a clinical severity score. JAMA 2001;72:2033-7.  Back to cited text no. 20
21.Tuman KJ, Mccarthy RJ, March RJ, et al. Mor­bidity and duration of ICU stay after cardiac surgery: a model for preoperative risk assess­ment. Chest 1992;102:36-44.  Back to cited text no. 21
22.Shlipak MG, Fried LF, Crump C, et al. Ele­vation of inflammatory and procoagulant bio­markers in elderly persons with renal insuf­ficiency. Circulation 2003;92:87-92.  Back to cited text no. 22
23.Blacher J, Safar ME, Guerin AP, et al. Aortic pulse wave velocity index and mortality in end-stage renal disease. Kidney Int 2003;63: 1852-60.  Back to cited text no. 23
24.London GM, Guerin AP, Marchais SJ, et al. Arterial media calcification in end-stage renal disease: impact on all-cause and cardiovascular mortality. Nephrol Dial Transplant 2003;18: 1731-40.  Back to cited text no. 24
25.Raggi P, Boulay A, Chasan-Taber S, et al. Cardiac calcification in the adult hemodialysis patients: a link between end-stage renal disease and cardiovascular disease. J Am Coll Cardiol 2002;39:695-701.  Back to cited text no. 25
26.Levin A, Thompson CR, Ethier J, et al. Left ventricular mass index increase in early renal disease: impact of decline in hemoglobin. Am J Kidney Dis 1999;34:125-34.  Back to cited text no. 26
27.Holzmann MJ, Ahnve S, Hammer N, et al. Creatinine clearance and risk of early mortality in patients undergoing coronary artery bypass grafting. J Thorac Cardiovasc Surg 2005;130: 746-52.  Back to cited text no. 27
28.Vanholder R, Ringoir S. Infectious morbidity and defects of phagocytic function in end-stage renal disease: a review. J Am Soc Nephrol 1993;3:1541-54.  Back to cited text no. 28
29.Sergeant P, Blackstone E, Meyns B, et al. Validation and interdependence with patient­variables of the influence of procedural varia­bles on early and late survival after CABG: KU Leuven Coronary Surgery Program. Eur J Cardiothorac Surg 1997;12:1-19.  Back to cited text no. 29
30.Wang F, Dupuis J, Nathan H, et al. An analysis of the association between preoperative renal dysfunction and outcome in cardiac surgery: estimated creatinine clearance or plasma crea­tinine level as measures of renal function. Chest 2003;124:1852-62.  Back to cited text no. 30
31.Mango CM, Diamondstone LS, Ramsay JG, et al. Renal dysfunction after myocardial revascu­larization: risk factors, adverse outcomes, and hospital resource utilization. Ann Intern Med 1998;128:194-203.  Back to cited text no. 31
32.Ryckwaert F, Boccara G, Frappier JM, et al. Incidence, risk factors, and prognosis of a moderate increase in plasma creatinine early after cardiac surgery. Crit Care Med 2002;30: 1495-8.  Back to cited text no. 32
33.Briguori C, Manganelli F, Scarpato P, et al. Acetylcystiene and contrast agent-associated nephrotoxicity. J Am Coll Cardiol 2002;40: 298-303.  Back to cited text no. 33
34.Cittanova ML, Zubicki A, Savu C, et al. The chronic inhibition of angiotensin-converting enzyme impairs postoperative renal function. Anesth Analg 2001;93:1111-5.  Back to cited text no. 34
35.Spinler SA, Nawarskas JJ, Boyce EG, et al. Predictive performance of ten equations for estimating creatinine clearance in cardiac pa­tients. Ann Pharmacother 1998;32:1275-83.  Back to cited text no. 35

Correspondence Address:
A Abdel Ghani
Nephrology Department, Mubarak Al Kabeer Hospital, P.O. Box 43787
Login to access the Email id

PMID: 21060177

Rights and Permissions


  [Figure 1]

  [Table 1], [Table 2], [Table 3]

This article has been cited by
1 An evaluation of renal functions in pulsatile and non-pulsatile cardiopulmonary bypass in the elderly
Hökenek, F. and Gürsoy, M. and Bakuy, V. and Kavala, A.A. and Demir, T. and Gülcan, F. and Kinoglu, B.
Turkish Journal of Thoracic and Cardiovascular Surgery. 2013; 21(3): 610-615


    Similar in PUBMED
    Search Pubmed for
    Search in Google Scholar for
    Email Alert *
    Add to My List *
* Registration required (free)  

    Subjects and Methods
    Statistical Methods
    Limitations of t...
    Article Figures
    Article Tables

 Article Access Statistics
    PDF Downloaded341    
    Comments [Add]    
    Cited by others 1    

Recommend this journal