Abstract
A best evidence topic was written according to a structured protocol. The question addressed was whether smoking cessation prior to cardiac surgery would result in a greater freedom from postoperative complications. A total of 564 papers were found using the reported searches, of which five represented the best evidence to answer the clinical question. The authors, date, journal, study type, population, main outcome measures and results are tabulated. Reported measures were operative mortality, pulmonary complications, infective complications, neurological complications, transfusion requirements, duration of ventilation, intensive care unit and hospital stay, intensive care unit re-admission, postoperative gas exchange parameters and postoperative pulmonary function. The largest of the best evidence studies demonstrated a significant reduction in pulmonary complications in non-smokers (P < 0.001); however, there was an increased requirement for transfusion in this cohort (P = 0.002). There were non-significant reductions in neurological complications, infective complications and re-admissions to intensive care. Another large cohort study demonstrated significant reductions in non-smokers in mortality (P < 0.0001), pulmonary complications (P = 0.0002), infection (P < 0.0007), intensive care unit re-admission (P = 0.0002), duration of mechanical ventilation (P = 0.026) and intensive care unit stay (P = 0.002). A larger cohort study again demonstrated significant reductions in non-smokers in pulmonary complications (P < 0.002), duration of mechanical ventilation (P < 0.012) and intensive care unit stay (P < 0.005). A smaller prospective cohort study reported significantly raised PaO2 (P = 0.0091) and reduced PaCO2 (P < 0.0001) levels in the non-smokers as well as improved FVC and FEV1 (P < 0.0001). There were also reductions in duration of intubation (P < 0.0001), intensive care unit stay (P < 0.0001) and hospital stay (P < 0.0013). Another small cohort study reporting outcomes of heart transplantation demonstrated significant improvement in non-smokers in terms of survival (P = 0.031), duration of intubation (P = 0.05) and intensive care unit stay (P = 0.021). We conclude that there is strong evidence demonstrating superior outcomes in non-smokers following cardiac surgery and advocate the necessity of smoking cessation as soon as possible prior to cardiac surgery.
Keywords: Smoking, Smoking cessation, Cardiac surgery
INTRODUCTION
A best evidence topic was constructed according to a structured protocol. This protocol is fully described in ICVTS [1].
CLINICAL SCENARIO
An asymptomatic 67-year-old man with a significant three-vessel disease on coronary angiography is referred for consideration of a coronary artery bypass surgery (CABG). He has been a life-long smoker with a 20-pack-year smoking history. However, his pulmonary function tests are within acceptable limits. He has no other respiratory comorbidities. You advise him regarding smoking cessation and consider whether to delay his operation until he has quit smoking.
THREE-PART QUESTION
In [patients undergoing elective cardiac surgery] does [smoking cessation preoperatively] result in [greater freedom from postoperative complications]?
SEARCH STRATEGY
Medline from 1948 to December 2011 using the PubMed interface (‘smoking cessation’ [MeSH Terms] OR (‘smoking’ AND ‘cessation’) OR (‘smoking cessation’) AND (‘thoracic surgery’) [MeSH Terms] OR (‘thoracic’ AND ‘surgery’) OR (‘thoracic surgery’) OR (‘cardiac’ AND ‘surgery’) OR (‘cardiac surgery’) OR (‘cardiac surgical procedures’) [MeSH Terms] OR (‘cardiac’ AND ‘surgical’ AND ‘procedures’) OR (‘cardiac surgical procedures’) OR (‘cardiac’ AND ‘surgery’). Related articles and references were screened for suitable articles.
SEARCH OUTCOME
Five hundred and sixty-four articles were found using the reported search strategy. From these, five articles were identified that provided the best evidence to answer the question. These are presented in Table 1.
Table 1:
Best evidence papers
| Author, date and country Study type (level of evidence) |
Patient group | Outcomes | Key results | Comments |
|---|---|---|---|---|
| Al-Sarraf et al. (2008) Ann Thorac Surg, UK Retrospective cohort study (level 3 evidence) [2] |
2587 consecutive patients undergoing isolated CABG between 2000 and 2007 | Operative mortality | Current smokers: 14 (2.9%); OR 0.84 (0.44–1.63) Former smokers: 29 (2.1%); OR 0.60 (0.35–1.03) Non-smokers: 26 (3.5%); OR 1.0 (−) P = 0.168 |
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 this study seem to have better prognosis than current smokers |
| All operations performed through median sternotomy and use of CPB | Re-exploration | Current smokers: 23 (4.8); OR 1.07 (0.62–1.84) Former smokers: 66 (4.8); OR 1.07 (0.70–1.63) Non-smokers: 34 (4.5%); OR 1.0 (−) P = 0.950 |
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| Patients stratified into three groups: Current smokers (n = 473) Former smokers (n = 1346) (cessation >4 weeks pre-op) Non-smokers (n = 748) |
IABP and inotropic support required | Current smokers: 30 (6.3%); OR 1.02 (0.63–1.66) Former smokers: 64 (4.7%); OR 0.78 (0.52–1.16) Non-smokers: 44 (5.9%); OR 1.0 (−) P = 0.354 |
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| Ventilation >24 h | Current smokers: 22 (4.6%); OR 0.96 (0.56–1.65) Former smokers: 62 (4.5%); OR 0.94 (0.62–1.43) Non-smokers: 36 (4.8%); OR 1.0 (−) P = 0.962 |
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| Pulmonary complications | Current smokers: 143 (30.1%); OR 1.73 (1.33–2.26) Former smokers: 318 (23.3%); OR 1.22 (0.98–1.52) Non-smokers: 149 (19.9%); OR 1.0 (−) P < 0.001 |
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| Neurological complications | Current smokers: 34 (7.2%); OR 1.40 (0.88–2.25) Former smokers: 83 (6.1%); OR 1.18 (0.80–1.74) Non-smokers: 39 (5.2%); OR 1.0 (−) P = 0.377 |
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| Infective complications | Current smokers: 45 (9.5%); OR 1.27 (0.84–1.91) Former smokers: 122 (8.9%); OR 1.19 (0.86–1.65) Non-smokers: 57 (7.6%); OR 1.0 (−) P = 0.459 |
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| Renal complications (requirement for dialysis) | Current smokers: 9 (1.9%); OR 0.89 (0.55–1.44) Former smokers: 34 (2.5%); OR 1.13 (0.79–1.61) Non-smokers: 23 (3.1%); OR 1.0 (−) P = 0.417 |
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| Gastrointestinal complications | Current smokers: 18 (3.8%); OR 1.69 (0.86–3.32) Former smokers: 50 (3.7%); OR 1.64 (0.94–2.86) Non-smokers: 17 (2.3%); OR 1.0 (−) P = 0.181 |
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| Readmission to ICU | Current smokers: 19 (4.0%); OR 1.91 (0.97–3.75) Former smokers: 43 (3.2%); OR 1.49 (0.83–2.66) Non-smokers: 16 (2.1%); OR 1.0 (−) P = 0.163 |
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| Mean ICU stay (days) | Current smokers: 1.8 ± 3.2 Former smokers: 2.0 ± 4.6 Non-smokers: 2.3 ± 5.0 P = 0.144 |
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| Mean postoperative stay (days) | Current smokers: 8.9 ± 10.5 Former smokers: 9.2 ± 11.9 Non-smokers: 9.9 ± 16.5 P = 0.078 |
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| Blood transfusion | Current smokers: 166 (34.9%); OR 0.68 (0.54–0.86) Former smokers: 511 (37.5%); OR 0.76 (0.63–0.91) Non-smokers: 330 (44.1%); OR 1.0 (−) P = 0.002 |
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| Jones et al. (2011) Interact CardioVasc Thorac Surg, UK [3] Retrospective cohort study (level 3 evidence) |
1108 patients undergoing cardiac surgery between 2002 and 2007 | Overall population: Operative mortality |
Current smokers: 24 (4.3%) Never smokers: 13 (2.3%) P = 0.067 |
The current data strengthen the observation that preoperative smoking is predictive of adverse outcomes of cardiac surgery in the elderly, and pulmonary complications may exert a significant effect on outcome |
| CABG: 63.4% Valve: 23.1% CABG + valve: 10.1% Other procedures: 3.4% |
Pulmonary complication | Current smokers: 60 (11.0%) Never smokers: 37 (6.8%) P = 0.01 |
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| Patients stratified into two groups: Current smokers (n = 554) Never smokers (n = 554) |
ICU re-admission | Current smokers: 38 (6.9%) Never smokers: 22 (4.0%) P = 0.03 |
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| The two groups were sub-stratified Current smokers: ≤70 years (n = 473) >70 years (n = 81) Never smokers: ≤70 years (n = 360) >70 years (n = 194) |
Infection | Current smokers: 176 (31.8%) Never smokers: 122 (22.0%) P < 0.001 |
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| New renal replacement | Current smokers: 31 (5.6%) Never smokers: 23 (4.2%) P = NS |
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| Blood transfusion | Current smokers: 336 (60.1%) Never smokers: 360 (65.1%) P = NS |
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| Re-exploration | Current smokers: 30 (5.4%) Never smokers: 35 (6.3%) P = NS |
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| Stroke | Current smokers: 13 (2.4%) Never smokers: 6 (1.1%) P = NS |
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| Mean ventilation, h (range) | Current smokers: 8.9 (0–640) Never smokers: 8.2 (0–46) P = NS |
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| Mean ICU stay, days (range) | Current smokers: 3.6 (0–60) Never smokers: 2.5 (0–75) P = NS |
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| >70 years cohort: Operative mortality |
Current smokers: 12 (14.8%) Never smokers: 4 (2.1%) P < 0.0001 |
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| Pulmonary complication | Current smokers: 20 (24.7%) Never smokers: 16 (8.2%) P = 0.0002 |
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| ICU re-admission | Current smokers: 16 (19.8%) Never smokers: 10 (5.2%) P = 0.0002 |
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| Infection | Current smokers: 36 (44.4%) Never smokers: 46 (23.8%) P < 0.0007 |
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| New renal replacement | Current smokers: 14 (17.3%) Never smokers: 6 (3.1%) P < 0.0001 |
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| Blood transfusion | Current smokers: 57 (70.4%) Never smokers: 139 (71.6%) P = NS |
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| Re-exploration | Current smokers: 4 (4.9%) Never smokers: 14 (7.2%) P = NS |
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| Stroke | Current smokers: 4 (4.9%) Never smokers: 5 (2.6%) P = NS |
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| Mean ventilation (h) (range) | Current smokers: 76.1 (0–22) Never smokers: 37.5 (0–46) P = 0.026 |
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| Mean ICU stay, days (range) | Current smokers: 6.2 (1–60) Never smokers: 2.8 (0–66) P = 0.002 |
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| Ngaage et al. (2002) Cardiovasc Surg, UK [4] Retrospective cohort study (level 3 evidence) |
2163 patients undergoing elective cardiac surgery between 1993 and 1999 |
Operative mortality | Smokers: 4.2% Ex-smokers: 3.2% Non-smokers: 2.8% |
Active smokers have a comparatively poor postoperative respiratory outcome after cardiac surgery. The duration of mechanical ventilation has a direct impact on the risk of postoperative pulmonary complications |
| CABG: 1579 (73%) Valve: 372 (17.2%) CABG + valve: 212 (9.8%) |
Mean ICU stay (h) | Smokers: 60 Ex-smokers: 34 Non-smokers: 31 P < 0.005 |
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| Patients stratified into three groups: Smokers (n = 207) Ex-smokers (n = 1075) (cessation >3 months pre-op) Non-smokers (n = 881) |
Postoperative pulmonary complications: | Smokers: 29.5% Ex-smokers: 14.7% Non-smokers: 13.6% P < 0.002 |
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| Atelectasis | Smokers: 10.6% Ex-smokers: 5.2% Non-smokers: 4.8% |
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| Chest infection | Smokers: 7.2% Ex-smokers: 1.9% Non-smokers: 2.1% |
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| Pleural effusion | Smokers: 3.9% Ex-smokers: 4% Non-smokers: 3.9% |
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| ARDS | Smokers: 3.4% Ex-smokers: 1.3% Non-smokers: 1.4% |
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| Mean duration of mechanical ventilation, h | Smokers: 16 Ex-smokers: 7.9 Non-smokers: 8.3 P < 0.012 |
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| Sternal wound infection | Smokers: 15% Ex-smokers: 11% Non-smokers: 15% |
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| Mediastinitis | Smokers: 2.4% Ex-smokers: 1.4% Non-smokers: 1% |
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| Arabaci et al. (2003) Jpn Heart J, Turkey [5] Prospective cohort study (level 3 evidence) |
213 consecutive patients undergoing elective isolated CABG |
Postoperative arterial blood gas analysis: PaO2 (mmHg) |
Smokers: 66.1 ± 8.0 Non-smokers: 69.1 ± 8.9 P = 0.0091 |
Preoperative evaluation of the pulmonary status of patients with a history of smoking who are scheduled for elective revascularization surgery is important, and that smoking cessation should be strongly encouraged performed preoperatively as early as possible in order to minimize postoperative respiratory complications |
| All operations performed through median sternotomy and use of CPB |
PaCO2 (mmHg) | Smokers: 38.6 ± 3.6 Non-smokers: 32.0 ± 4.7 P < 0.0001 |
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| Patients stratified into two groups: Smokers (n = 117) Non-smokers (n = 96) (cessation >20 years pre-op) |
pH | Smokers: 7.4 ± 0.1 Non-smokers: 7.4 ± 0.1 P = NS |
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| Postoperative pulmonary function tests: VC (L) |
Smokers: 2.3 ± 0.4 Non-smokers: 2.7 ± 0.4 P < 0.0001 |
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| FVC (L) | Smokers: 2.4 ± 0.5 Non-smokers: 2.8 ± 0.4 P < 0.0001 |
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| FEV1 (L) | Smokers: 1.7 ± 0.4 Non-smokers: 2.1 ± 0.2 P < 0.0001 |
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| FEV1/FVC | Smokers: 72.2 ± 11.5 Non-smokers: 76.0 ± 9.8 P = 0.0110 |
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| Intubation period (h) | Smokers: 19.9 ± 11.5 Non-smokers: 14.1 ± 4.3 P < 0.0001 |
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| ICU stay (days) | Smokers: 3.2 ± 1.3 Non-smokers: 2.4 ± 0.6 P < 0.0001 |
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| Hospitalization period (days) | Smokers: 14.1 ± 4.4 Non-smokers: 12.5 ± 2.4 P < 0.0013 |
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| Pulmonary complications: Atelectasis |
Smokers: 5 (4.3%) Non-smokers: 2 (2.1%) |
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| Pleural effusion | Smokers: 11 (9.4%) Non-smokers: 4 (4.2%) |
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| Chest infection | Smokers: 8 (6.8%) Non-smokers: 4 (4.2%) |
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| Total | Smokers: 24 (20.5%) Non-smokers: 10 (10.4%) |
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| Sanchez-Lazaro et al. (2007) Transplant Proc, Spain [6] Retrospective cohort study (level 3 evidence) |
288 patients undergoing heart transplantation between 1987 and 2006 | Survival rate | Smokers: 81.63% Ex-smokers: 92.11% Non-smokers: 89.57% P = 0.031 |
Patients who smoke or have smoked until shortly before heart transplantation show a poorer prognosis and a higher rate of early pulmonary complications after heart transplantation The deleterious effects of smoking are progressively reduced as the interval between smoking cessation and transplantation increases |
| Patients stratified into three groups: Smokers (n = 49) Ex-smokers (n = 76) (cessation < 1 year pre-op) Non-smokers (n = 163) (cessation >1 year pre-op) |
Mean intubation time, h | Smokers: 14.2 ± 7.3 Ex-smokers: 33.4 ± 44.6 Non-smokers: 17.9 ± 19.2 P = 0.05 |
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| Mean ICU stay, days | Smokers: 4.4 ± 1.88 Ex-smokers: 7.9 ± 10.5 Non-smokers: 4.84 ± 3.49 P = 0.021 |
RESULTS
Al-Sarraf et al. [2] conducted a retrospective cohort study of 2587 consecutive patients undergoing isolated CABG. The patients were stratified into three groups of current smokers (n = 473); former smokers, having stopped >4 weeks preoperatively (n = 1346); and non-smokers (n = 748). Significant reductions in pulmonary complications were observed between the groups, with incidences of 30.1, 23.3 and 19.9% in the current smokers, former smokers and non-smokers, respectively (P < 0.001). An inverse relationship in blood transfusion requirements was observed, with incidences of 34.9, 37.5 and 44.1% in the current smokers, former smokers and non-smokers, respectively (P = 0.002). Statistically non-significant reductions were observed in neurological complications (7.2, 6.1 and 5.2%, respectively, P = 0.377), infective complications (9.5, 8.9 and 7.6%, respectively, P = 0.459) and re-admissions to the intensive care unit (4.0, 3.2 and 2.1%, respectively, P = 0.163).
Jones et al. [3] conducted a retrospective cohort study of 1108 patients undergoing cardiac surgery, stratified into two groups, current smokers (n = 554) and never smokers (n = 554). A further subgroup analysis was carried out on patients above and below 70 years of age. There was a non-significant reduction in operative mortality in the never smokers (2.3 vs 4.3%, P = 0.067). There were significant reductions in the never smokers in terms of pulmonary complications (6.8 vs 11%, P = 0.01), intensive care unit re-admission (4.0 vs 6.9%, P = 0.03) and infection (22.0 vs 31.8%, P < 0.001). In the subgroup analysis of the >70-year old patients, there were significant reductions in the never smokers in terms of operative mortality (2.1 vs 14.8%, P < 0.0001), pulmonary complications (8.2 vs 24.7%, P = 0.0002), intensive care unit re-admission (5.2 vs 19.8%, P = 0.0002), infection (23.8 vs 44.4%, P < 0.0007), new renal replacement (3.1 vs 17.3%, P < 0.0001), mean mechanical ventilation hours (37.5 vs 76.1, P = 0.026) and mean intensive care unit days (2.8 vs 6.2, P = 0.002).
Ngaage et al. [4] conducted a retrospective cohort study of 2163 patients undergoing elective cardiac surgery, stratified into three groups: smokers (n = 207), ex-smokers (n = 1075) and non-smokers (n = 881). Significant reductions in favour of the non-smoking groups were observed in terms of mean intensive care unit hours (60, 34 and 31 in the smokers, ex-smokers and non-smokers, respectively, P < 0.005), pulmonary complications (29.5, 14.7 and 13.6%, respectively, P < 0.002) and mean mechanical ventilation hours (16, 7.9 and 8.3, respectively, P < 0.012).
Arabaci et al. [5] conducted a prospective cohort study of 213 consecutive patients undergoing elective isolated CABG. Patients were stratified into two groups: smokers (n = 117) and non-smokers, having stopped >20 years preoperatively (n = 96). Postoperative arterial blood gas analysis demonstrated significantly superior results for the non-smokers in PaO2 (mmHg) (69.1 vs 66.1, P = 0.0091) and PaCO2 (mmHg) (32.0 vs 38.6, P < 0.0001). Postoperative pulmonary function tests demonstrated significant increases in the non-smokers in vital capacity (VC, L) (2.7 vs 2.3, P < 0.0001), forced vital capacity (FVC, L) (2.8 vs 2.4, P < 0.0001), forced expiratory volume (FEV1, L) (2.1 vs 1.7, P < 0.0001) and FEV1/FVC ratio (76.0 vs 72.2, P = 0.0110). There were also significant reductions in intubation hours (14.1 vs 19.9, P < 0.0001), intensive care unit days (2.4 vs 3.2, P < 0.0001) and hospitalization days (12.5 vs 14.1, P < 0.0013) in favour of the non-smokers.
Sanchez-Lazaro et al. [6] conducted a retrospective cohort study of 288 patients undergoing heart transplantation, who were stratified into three groups: smokers (n = 49), ex-smokers, having stopped <1 year preoperatively (n = 76), and non-smokers, having stopped >1 year preoperatively (n = 163). Significant improvement in survival was observed in the non-smoking groups with the rates of 81.63, 92.11 and 89.57% in the smokers, ex-smokers and non-smokers, respectively (P = 0.031). Similar improvements were observed in terms of mean intubation hours (14.2, 33.4 and 17.9, respectively, P = 0.05) and mean intensive care unit days (4.4, 7.9 and 4.84, respectively, P = 0.021).
CLINICAL BOTTOM LINE
There is convincing evidence presented that patients who are not active smokers at the time of cardiac surgery have improved outcomes postoperatively in comparison with smokers. This is evident in terms of a reduction in mortality, pulmonary complications, infective complications, duration of mechanical ventilation, intensive care unit stay and re-admission and overall hospital stay. There are also improvements observed in postoperative gas exchange and pulmonary function. There is a great variation observed in the duration of smoking cessation required to achieve these outcomes; however, it is widely accepted that the longer the duration preoperatively, the greater the benefit to the patient. These findings support the necessity of smoking cessation as soon as possible prior to cardiac surgery.
Conflict of interest: none declared.
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