Ann Thorac Surg 2008;86:517-523. doi:10.1016/j.athoracsur.2008.03.070
© 2008 The Society of Thoracic Surgeons
Original Articles: Adult Cardiac
Effect of Smoking on Short-Term Outcome of Patients Undergoing Coronary Artery Bypass Surgery
Nael Al-Sarraf, MRCSIa,b,*,
Lukman Thalib, PhDc,
Anne Hughes, MSa,
Michael Tolan, FRCSCtha,
Vincent Young, MDa,
Eillish McGovern, FRCSIa
a Department of Cardiothoracic Surgery, St. James's Hospital, Dublin, Ireland
b Department of Cardiothoracic Surgery, Chest Hospital, Kuwait University, Kuwait
c Department of Community Medicine (Biostatistics), Faculty of Medicine, Kuwait University, Kuwait
Accepted for publication March 28, 2008.
* Address correspondence to Dr Al-Sarraf, Al-Deya, PO Box 15179, Kuwait 35452 (Email: trinityq8{at}hotmail.com).
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Abstract
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Background: Data on the effect of smoking on short-term outcome in patients undergoing coronary artery bypass graft (CABG) surgery are limited. We sought to assess the morbidity and in-hospital mortality of smokers and former smokers compared with nonsmokers undergoing CABG.
Methods: This is a retrospective review of prospectively collected departmental data base. In all, 2,587 consecutive patients underwent isolated CABG between February 2000 and June 2007. Of these, 475 patients were current smokers, 1,364 were former smokers of more than 4 weeks, and 748 were nonsmokers.
Results: Current smokers had higher rates of postoperative pulmonary complications than former smokers and nonsmokers (30.1% versus 23.3% versus 19.9%, p < 0.001). Blood transfusion requirement was lower for current smokers group than for the other two groups (34.9% versus 37.5% versus 44.1%, p = 0.02). Adjusted odd ratios (OR) for early clinical outcomes showed that current smokers had 59% higher risk of developing pulmonary complications (OR 1.59) than nonsmokers, with former smokers showing an intermediate pattern (OR 1.17). Current smokers had 36% lower risk of postoperative blood transfusion than nonsmokers (OR 0.64), with former smokers showing an intermediate pattern (OR 0.94). Rates of other postoperative complications, intensive care unit readmission, postoperative length of stay, and mortality did not differ among the three groups.
Conclusions: Smoking is associated with significant pulmonary complications after CABG. In-hospital mortality is not influenced by smoking. Smokers should be encouraged to quit before undergoing CABG, and a period of 1 month may be beneficial, given that former smokers in our study seem to have better prognosis than current smokers.
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Introduction
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Smoking is a major risk factor for coronary heart disease. Over the past 2 decades there has been a steady decline in deaths from coronary disease in United States [1]. Half of this observed decline is attributable to reductions in risk factors and the other half is attributable to evidence based medical therapies [1]. Reduction of smoking prevalence alone accounted for 12% of the overall observed effect [1]. The impact of smoking on both short- and long-term outcome in patients undergoing percutaneous coronary revascularization [2, 3] has been well recognized. In addition, several studies have examined the effect of smoking on the outcome of patients admitted with unstable angina or acute myocardial infarction (MI) [4, 5]. From a surgical point of view, the impact of smoking on morbidity and mortality has been reported in some surgical procedures including transplantation [6], vascular surgery [7], and thoracic resections [8]. However, data on the effect of smoking on short-term outcome in patients undergoing cardiac surgery remain scarce [9, 10] even though, more than a decade ago, some cardiac surgeons have debated whether active smokers should undergo cardiac surgery [11] and whether those who stopped smoking should wait for a certain period of time before undergoing surgery [12]. Furthermore, physicians in United States were shown to be less likely to recommend coronary artery bypass graft surgery (CABG) for patients who smoked [13]. In this paper, we analyzed a large cohort of patients undergoing CABG in a single center, adding more to our understanding of the effect of smoking both on mortality and postoperative complications.
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Patients and Methods
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Patients
This is a retrospective review of a prospectively collected electronic departmental database (Patient Analysis and Tracking System, Dendrite Clinical, United Kingdom). All data were collected prospectively in the departmental database through the input of a dedicated database manager. Patients were stratified (based on their smoking status) into three groups. Current smokers group (n = 473) included all patients who were active smokers and those who quit smoking within 4 weeks of surgery. Former smokers group (n = 1,346) included all patients who quit smoking more than 4 weeks before surgery. Nonsmokers (n = 748) included all patients who had never smoked in their lives before surgery. Smoking refers to consumption of cigarettes, cigars, or pipes. Outcome measures studied included in-hospital mortality, postoperative morbidities, length of hospital stay, and length of intensive care unit (ICU) stay. This study and the departmental database were both approved by our Institutional Review Board. Individual patient consent was obtained for entry into the database. However, our Institutional Review Board waived the need for individual patient consent for this study.
Cardiopulmonary Bypass and Definitions
All CABGs were performed through a median sternotomy with cardiopulmonary bypass as we previously reported [14]. Operative priority was determined by cardiothoracic surgeons according to standard criteria and was previously reported [14]. In-hospital mortality refers to all deaths within the same admission post cardiac surgery regardless of their length of stay. Renal complications refer to postoperative renal failure that required dialysis or managed conservatively in patients with no prior history of same or patients with preexisting renal impairment that worsened after the surgery requiring dialysis. Neurologic complications refer to the incidence of transient ischemic attacks or permanent strokes. Gastrointestinal complications refer to gastrointestinal bleed, pancreatitis, and bowel ischemia and obstruction. Infective complications refer to sternal/leg wound infections (requiring antibiotics or surgical intervention) and sepsis. Pulmonary complications refer to postoperative chest infection, tracheostomy insertion, pleural effusion requiring drainage, adult respiratory distress syndrome, respiratory arrest, and reintubation. Blood transfusion requirement refers to the need of transfusion of packed red blood cells and excluding the need of isolated platelet or fresh frozen plasma transfusion.
Data Analysis
Data analysis began by exploring the differences between smoking, ex-smoking, and nonsmoking groups for clinical, admission, and outcome variables. Categorical variables were compared between the groups using the 
2 test, and continuous variables were compared using analysis of variance or nonparametric Kruskal-Wallis test based on the satisfaction of the normal assumption (Table 1). The effect of smoking on the outcome variables was further analyzed using multiple logistic regression methods (Table 2). Effect size of smoking on each individual outcome variables was quantified by crude odds ratios (OR [Table 3]), followed by adjusted odds ratios after accounting for potential confounding variables (Table 4). Odds ratios, 95% confidence intervals (CI) as well as exact p values are reported. Statistical analysis was performed using SPSS version 15 (SPSS, Chicago, Illinois). The p values were considered statistically significant when less than 0.05.
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Table 1 Sociodemographic and Clinical History at Admission Classified According to Smoking Status for Those Who Underwent Coronary Artery Bypass Graft Surgery (n = 2,587)
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Table 3 Crude Odds Ratios (OR) for Early Clinical Outcomes of Current Smokers, Former Smokers, and Nonsmokers (n = 2,587)
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Table 4 Adjusted Odds Ratios (OR) Related to Early Clinical Outcomes in Current Smokers, Former Smokers, and Nonsmokers After Adjusting for Potential Confounders Using Multiple Logistic Regression (n = 2,587)
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Results
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Our cohort (n = 2,587) consisted of 531 female and 2,056 male patients. Age ranged from 18 to 86 years old with a mean (± 1 SD) of 63.4 (± 10.1) years old. In-hospital mortality overall was 2.7% (69 patients). Preoperative factors and patient characteristics that showed significant differences among the three groups are summarized in Table 1. Factors that were not statistically significant are included as a footnote in Table 1.
Current smokers were more likely to be male, younger age, with higher (class III/IV) preoperative dyspnea score than nonsmokers, with former smokers showing an intermediate pattern between the two groups (Table 1). Current smokers had a higher incidence of preoperative MI than nonsmokers, with former smokers showing an intermediate pattern. In addition, current smokers were more likely to have CABG performed within 90 days of the onset of MI than nonsmokers (29.3% versus 23.4%, respectively), with former smokers being least likely to have CABG performed within this duration (17.1%, p < 0.001). Incidence of hypertension was lower among current smokers than among both former smokers and nonsmokers (50.1% versus 58.6% versus 60%, p < 0.001). As expected, current smokers had a higher incidence of chronic obstructive pulmonary disease than nonsmokers, with the risk declining in former smokers (7.4% versus 5.2% versus 1.1%, respectively, p < 0.001). Nonsmokers required more intra-aortic balloon pump support before surgery than current smokers (2.1% versus 1.7%), with former smokers requiring the least support (0.8%, p = 0.032). Current smokers were more likely to have urgent CABG than nonsmokers (68.2% versus 57%), with former smokers being the least among the three groups (52.3%, p < 0.001). Paradoxically, nonsmokers required more emergency and salvage CABG than the other two groups. Current smokers had the lowest mean body mass index compared with the other two groups (Table 1). Table 2 summarizes the postoperative complication profile and in-hospital mortality among the three groups with their relevant p-values.
The crude ORs for early clinical outcome among the three groups are depicted in Table 3. The adjusted ORs for early clinical outcomes among the three groups are summarized in Table 4. These ORs were calculated after adjustment of potential confounding factors using multiple logistic regression analysis. Such factors include age, sex, body mass index, diabetes mellitus, hypertension, chronic obstructive pulmonary disease, ejection fraction, extent of coronary disease, operative priority, number of previous MI, interval between MI and surgery, angina status, dyspnea score, congestive cardiac failure, intra-aortic balloon pump, extracardiac arteriopathy, peripheral vascular disease, hypercholesterolemia, left main stem stenosis, cardiopulmonary bypass time, and aortic cross-clamp time.
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Comment
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The smoker's paradox whereby smokers have an increased risk of acute MI and angina compared with nonsmokers but have lower mortality and more favorable outcome after percutaneous coronary revascularization has been previously signalled [2, 15]. While this phenomenon seems to be applicable to percutaneous intervention, its applicability to cardiac surgery remains unknown. In our work, in which a large group of patients was analyzed, such a phenomenon does not seem to operate among smokers undergoing CABG. We have not seen a protective effect of smoking in terms of in-hospital mortality nor a significantly reduced postoperative complications.
The deleterious effect of smoking on pulmonary function after CABG has been previously signalled. Arabaci and colleagues [16] examined the effect of smoking on pulmonary function of 213 patients undergoing elective CABG. They showed that smoking negatively affects the pulmonary function by causing an obstructive type respiratory problem and by worsening the existing restrictive respiratory problems. This was evident from the degree of hypoxemia and the restrictive ventilatory defect which were significantly higher in smokers than nonsmokers. Smokers had higher rates of reduction in forced expiratory volume in 1 second and forced vital capacity (FEV1/FVC) than nonsmokers that explain the obstructive pattern [16]. Furthermore, smokers in general tend to have lower baseline FEV1 values [8] and a higher incidence of chronic obstructive pulmonary disease than former smokers or nonsmokers (Table 1), causing a further deleterious effect on pulmonary function postoperatively. Former smokers have lower pulmonary complication rate than current smokers (OR 1.17 versus 1.59, respectively). This is expected, as smoking cessation can result in a decrease in postoperative pulmonary complications through physiologic improvement in ciliary action, macrophage activity, and small airway function as well as a decrease in sputum production [8]. Certainly, our data remain consistent with previously reported studies. Warner and colleagues studied 200 patients undergoing CABG at Mayo Clinic and reported that patients who had quit smoking 8 weeks before undergoing surgery had 15% rate of pulmonary complications compared with 33% in current smokers [9].
Some previous studies [17] have reported that smokers have a higher hemoglobin and higher packed cell volume than nonsmokers, with former smokers somewhere in between. In addition, smokers are more likely to have higher fibrinogen concentration and increased blood viscosity than nonsmokers [17]. Moreover, smoking has been shown to impair endothelial function, exacerbate platelet adhesiveness and aggregation, increase fibrinogen levels, and alter the coagulation-fibrinolysis cascade, leading to an increase in thrombus formation [18]. The overall balance will then potentially be in the favor of clot formation than clot dissolution and blood thinning. This may, in part, explain the lower bleeding tendency and low blood transfusion requirements seen in smokers compared with nonsmokers. In addition, it has been previously demonstrated that smoking increases carboxyhemoglobin concentration, leading to decrease oxygen delivery to tissues, stimulating hemoglobin synthesis and leading to a higher hemoglobin concentration among smokers compared with nonsmokers [19]. This finding was supported by Green and Harari [20], who showed a drop in mean hemoglobin concentration of 3.7 g/L in males who quit smoking compared with never smokers over a follow-up period of 1 to 4 years. Furthermore, a positive dose-response relationship has been shown to exist between mean hemoglobin concentration and number of cigarettes smoked per day [19, 21]. All these observations do enforce a difference in the hemoglobin concentration between smokers and nonsmokers. In our unit, one of the determinants of postoperative blood transfusion requirement is the postoperative hemoglobin concentration (in addition to other factors such as hemodynamic instability, and so forth). This in part can explain the observed decrease in the requirement of blood transfusion among smokers compared with nonsmokers.
An interesting finding in our work was the lack of correlation between the smoking status and the risk of death after CABG. Data on mortality after percutaneous coronary revascularization have been rather conflicting. Some studies have suggested a more favorable outcome seen in smokers than nonsmokers [2, 17] whereas others have shown the opposite, namely, a higher mortality rate among smokers than nonsmokers [4]. Such an association remains unknown in cardiac surgery where the risk of cardiopulmonary bypass is taken into account. In our analysis, smoking does not seem to have bearing on in-hospital mortality. This in part might be due to lack of increased postoperative complications (other than pulmonary) among smokers compared with nonsmokers (Table 2). It should also be noted that given an overall lower death rate after CABG nowadays and in our own database, for significant differences to occur, larger samples may be needed, particularly if the effect size of smoking on in-hospital mortality is smaller. Furthermore, the preoperative characteristics among the three groups showed no significant difference in the incidence of cardiovascular risk factors including diabetes mellitus and hypercholesterolemia. In addition, factors influencing the short-term prognosis after CABG (namely, peripheral vascular disease, extracardiac arteriopathy, congestive cardiac failure, extent of coronary vessel disease, left main stem stenosis, and the preoperative ejection fraction) showed no significant difference among the three groups (Table 1).
All of these factors (whether preoperatively or postoperatively) put together dictate the overall survival rate, which is similar among current smokers and former smokers to nonsmokers. Van Domburg and colleagues [10] have reported a similar in-hospital mortality rate among smokers and nonsmokers. They reviewed data on 985 patients undergoing CABG but only considered two separate groups of patients (smokers versus nonsmokers) and did not take into account the range of postoperative complications after CABG or the behavior pattern among patients who stopped smoking before CABG (former smoker group) [10]. However, they did show a decrease in long-term survival and a higher need for revascularization among patients who continued to smoke after CABG versus patients who quit after the procedure in a mean follow-up of 20 years [10]. A similar trend has also been reported elsewhere in vascular surgery whereby smokers undergoing endovascular abdominal aortic aneurysm repair have been reported to have an in-hospital mortality rate similar to that of nonsmokers [7], taking cardiovascular risk factors into account.
The effect of smoking on long-term survival after CABG has been reported previously [10, 22, 23]. These studies have shown a higher rate of death and higher rate of revascularization in patients actively smoking after CABG. These findings coupled with our observed effect of increased postoperative pulmonary complications should encourage clinicians to continue encouraging patients to quit smoking both before and after CABG. Smoking cessation programs should start in the preoperative period and continue postoperatively to achieve the maximum desired potential.
Although all data were prospectively collected, there are few limitations in our work. Firstly, the smoking status was determined on the basis of self-report with no biochemical proof of the patients' smoking habits. However, self-reported smoking habits have been found to be accurate in studies of different population [24]. Secondly, we did not record the number of cigarette smoked per day or the number of pack-years smoked. Thirdly, our electronic database did not record the preoperative hemoglobin values for all CABG patients. However, within these acceptable limitations, we believe our work will shed more light into the subject.
In conclusion, smoking increases the risk of postoperative pulmonary complications after CABG but does not affect the overall short-term mortality after the procedure. Quitting smoking in the preoperative period should be emphasized, and active smoking cessation counseling should be continued postoperatively. A cessation period of 1 month before CABG may be beneficial, given that former smokers in our study seem to have a lower postoperative pulmonary complication rate than do current smokers.
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References
|
|---|
- Ford ES, Ajani UA, Croft JB, et al. Explaining the decrease in U.S. deaths from coronary disease, 1980–2000 N Engl J Med 2007;356:2388-2398.[Abstract/Free Full Text]
- Weisz G, Cox DA, Garcia E, et al. Impact of smoking status on outcomes of primary coronary intervention for acute myocardial infarction—the smoker's paradox revisited Am Heart J 2005;150:358-364.[Medline]
- Cohen DJ, Doucet M, Cutlip DE, Ho KKL, Popma JJ, Kuntz RE. Impact of smoking on clinical and angiographic restenosis after percutaneous coronary intervention: another smoker's paradox? Circulation 2001;104:773-778.[Abstract/Free Full Text]
- Wilson K, Gibson N, Willan A, Cook D. Effect of smoking cessation on mortality after myocardial infarction: meta-analysis of cohort studies Arch Intern Med 2000;160:939-944.[Abstract/Free Full Text]
- Kinjo K, Sato H, Sakata Y, et al. Impact of smoking status on long-term mortality in patients with acute myocardial infarction Circ J 2005;69:7-12.[Medline]
- Pungpapong S, Manzarbeitia Ortiz J, et al. Cigarette smoking is associated with an increased incidence of vascular complications after liver transplantation Liver Transplant 2002;8:582-587.[Medline]
- Lottman PEM, Van Marrewijk CJ, Fransen GAJ, Laheij RJF, Buth J. Impact of smoking on endovascular abdominal aortic aneurysm surgery outcome Eur J Vasc Endovasc Surg 2004;27:512-518.[Medline]
- Barrera R, Shi W, Amar D, et al. Smoking and timing of cessation: impact on pulmonary complications after thoracotomy Chest 2005;127:1977-1983.[Medline]
- Warner MA, Offord KP, Warner ME, Lennon RL, Conover MA, Jansson- Schumacher U. Role of preoperative cessation of smoking and other factors in postoperative pulmonary complications: a blinded prospective study of coronary artery bypass patients Mayo Clin Proc 1989;64:609-616.[Medline]
- Van Domburg RT, Meeter K, Van Berkel DFM, Veldkamp RF, Van Herwerden LA, Bogers AJJC. Smoking cessation reduces mortality after coronary artery bypass surgery: a 20-year follow-up study J Am Coll Cardiol 2000;36:878-883.[Abstract/Free Full Text]
- Underwood MJ, Bailey JS. Coronary bypass surgery should not be offered to smokers Br Med J 1993;306:1047-1050.[Free Full Text]
- Odom NJ, Ashraf SS, Sharif MH, Akhtar K. Access to heart surgery for smokers: persuade smokers to give up before surgery Br Med J 1993;307:128.[Free Full Text]
- Mogielnicki RP, Bell J, Fowler FJ. The influence of patient smoking status on therapeutic decisions J Gen Intern Med 1992;7:165-169.[Medline]
- Doddakula K, Al-Sarraf N, Gately K, et al. Predictors of acute renal failure requiring renal replacement therapy post cardiac surgery in patients with preoperatively normal renal function Interact Cardiovasc Thorac Surg 2007;6:314-318.[Abstract/Free Full Text]
- Hasdai D, Garratt KN, Grill DE, Lerman A, Holmes DR. Effect of smoking status on the long-term outcome after successful percutaneous coronary revascularization N Engl J Med 1997;336:755-761.[Abstract/Free Full Text]
- Arabaci U, Akdur H, Yigit Z. Effects of smoking on pulmonary functions and arterial blood gases following coronary artery surgery in Turkish patients Jpn Heart J 2003;44:61-72.[Medline]
- Violaris AG, Thury A, Reger E, Melkert R, Serruys PW. Influence of a history of smoking on short term (six months) clinical and angiographic outcome after successful coronary angioplasty Heart 2000;84:299-306.[Abstract/Free Full Text]
- Leone A. Smoking, haemostatic factors, and cardiovascular risk Curr Pharm Des 2007;13:1661-1667.[Medline]
- Nordenberg D, Yip R, Binkin NJ. The effect of cigarette smoking on hemoglobin levels and anemia screening JAMA 1990;264:1556-155926.[Abstract/Free Full Text]
- Green MS, Harari G. A prospective study of the effects of changes in smoking habits on blood count, serum lipids and lipoproteins, body weight and blood pressure in occupationally active men. The Israeli CORDIS Study. J Clin Epidemiol 1995;48:1159-1166.[Medline]
- Skjelbakken T, Dahl IM, Wilsgaard T, Langbakk B, Løchen ML. Changes in haemoglobin levels according to changes in body mass index and smoking habits, a 20-year follow-up of a male cohort: the Tromsø Study 1974–1995 Eur J Epidemiol 2006;21:493-499.[Medline]
- Cavender JB, Rogers WJ, Fisher LD, Gersh BJ, Coggin CJ, Myers WO, CASS Investigators Effects of smoking on survival and morbidity in patients randomized to medical or surgical therapy in the Coronary Artery Surgery Study (CASS): 10-year follow-up J Am Coll Cardiol 1992;20:287-294.[Abstract]
- Papathanasiou A, Milionis H, Toumpoulis L, et al. Smoking cessation is associated with reduced long-term mortality and the need for repeat interventions after coronary artery bypass grafting Eur J Cardiovasc Prev Rehabil 2007;14:448-450.[Medline]
- Patrick DL, Thompson DC, Diehr P, Koepsell T, Kinne S. The validity of self- reported smoking: a review and meta analysis Am J Public Health 1994;84:1086-1093.[Abstract/Free Full Text]
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Abstract
Introduction
