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(Chest. 2001;120:705-710.)
© 2001 American College of Chest Physicians

Relationship Between the Duration of the Preoperative Smoke-Free Period and the Incidence of Postoperative Pulmonary Complications After Pulmonary Surgery*

Masashi Nakagawa, MD; Hideo Tanaka, MD; Hideaki Tsukuma, MD and Yoshihiko Kishi, MD

* From the Departments of Anesthesiology (Drs. Nakagawa and Kishi) and Cancer Control and Statistics (Drs. Tanaka and Tsukuma), Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka City, Japan.

Correspondence to: Masashi Nakagawa, MD, Department of Anesthesiology, Osaka Medical Center for Cancer and Cardiovascular Diseases, 1-3-3 Nakamichi Higashinari, Osaka City, 537-8511, Japan; e-mail: m.h.naka{at}f4.dion.ne.jp


   Abstract
TOP
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 Conclusion
 References
 
Study objective: To examine the relationship between the duration of the preoperative smoke-free period and the development of postoperative pulmonary complications (PPCs) in patients who underwent pulmonary surgery, and the optimal timing of quitting smoking.

Design: Retrospective cohort study.

Setting: Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka, Japan.

Patients: Two hundred eighty-eight consecutive patients who underwent pulmonary surgery between January 1997 and December 1998.

Measurements and results: We collected information on the preoperative characteristics, intraoperative conditions, and occurrence of PPCs by reviewing the medical records. Study subjects were classified into four groups based on their smoking status. A current smoker was defined as one who smoked within 2 weeks prior to the operation. Recent smokers and ex-smokers were defined as those whose duration of abstinence from smoking was 2 to 4 weeks and > 4 weeks prior to the operation, respectively. A never-smoker was defined as one who had never smoked. The incidence of PPCs among the current smokers and recent smokers was 43.6% and 53.8%, respectively, and each was higher than that in the never-smokers (23.9%; p < 0.05). The moving average of the incidence of PPCs gradually decreased in patients whose smoke-free period was 5 to 8 weeks or longer. After controlling for sex, age, results of pulmonary function tests, and duration of surgery, the odds ratios for PPCs developing in current smokers, recent smokers, and ex-smokers in comparison with never-smokers were 2.09 (95% confidence interval [CI], 0.83 to 5.25), 2.44 (95% CI, 0.67 to 8.89), and 1.03 (95% CI, 0.47 to 2.26), respectively.

Conclusions: These findings indicate that preoperative smoking abstinence of at least 4 weeks is necessary for patients who undergo pulmonary surgery, to reduce the incidence of PPCs.

Key Words: postoperative pulmonary complications • preoperative care • pulmonary surgery • smoking cessation.


   Introduction
TOP
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 Conclusion
 References
 
Postoperative pulmonary complications (PPCs) are associated with increased length of hospital stay1 and mortality2 after surgery. It is thought that PPCs occur relatively frequently, although the reported incidence of PPCs has varied due to differ

ences in its definition and study population. PPCs still remain a significant problem in clinical practice, despite recent remarkable advances in anesthesia and surgical care.3

Many studies have identified factors associated with an increased risk for PPCs. The chief risk factors are advanced age,4 5 6 7 cigarette smoke,4 5 8 9 obesity,4 10 type of surgery,1 4 7 8 type of anesthesia,4 7 8 abnormal chest radiographic finding,1 8 chronic cough,1 4 7 8 history of pulmonary disease,1 4 7 8 and history of cardiac disease.8 These factors are helpful in identifying patients at high risk for developing PPCs; however, most of these factors are not helpful in reducing the occurrence of PPCs because the factors are not likely to change in a patient.

Smoking cessation is well-known to be one of the most important preoperative preparations prior to any type of surgery; however, the relationship between the duration of preoperative smoking abstinence and beneficial effect on postoperative complications is not clear. Only a few reports have focused on the relationship between a change in smoking habit and the incidence of PPCs. Warner et al11 examined the relationship between the timing of preoperative smoking cessation and the incidence of PPCs in patients who underwent coronary artery bypass graft surgery and reported that a smoke-free period of > 8 weeks was needed to reduce the incidence of PPCs. Bluman et al8 investigated the effect of improvement in smoking status on the incidence of PPCs; however, they only examined whether preoperative reduction in smoking was associated with a reduced risk for PPCs. Thus, limited information is available on the optimal timing of quitting smoking prior to surgery.

The development of PPCs is influenced by many factors;3 thus, further studies are needed to establish the optimal timing of preoperative quitting. The aims of this study are to clarify the relationship between the duration of the preoperative smoke-free period and the incidence of PPCs, and to determine the optimal time at which patients who will undergo a pulmonary surgical procedure should quit smoking.


   Materials and Methods
TOP
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 Conclusion
 References
 
Design/Subjects
The study subjects were 288 consecutive patients who underwent a pulmonary surgical procedure at our institution between January 1997 and December 1998. By reviewing their medical records, we ascertained the preoperative and intraoperative factors, and whether PPCs occurred in each subject. The relationship between these factors and the incidence of PPCs was examined. This retrospective cohort study was approved by the Ethics Committee at Osaka Medical Center for Cancer and Cardiovascular Diseases.

Assessment of Preoperative Factors and Smoking Behavior
We collected the following information from the medical records of each patient: age at hospital admission, sex, height, weight, American Society of Anesthesiologists (ASA) physical status, and results of spirometry. To assess whether a patient was overweight, the body mass index (BMI) was calculated. Information on the smoking habit was obtained from a self-administered questionnaire on the health status of the patient at the first visit, from the interview at hospital admission by nurses, and from the preoperative interview by the anesthesiologist 1 day or 2 days prior to the surgery. If these three data were conflicting, we used the worst smoking status, because most smokers tended to report a better smoking status

The subjects were classified into four groups based on his or her smoking habits. A current smoker was defined as one who had smoked within 2 weeks prior to the operation (n = 37). Past smokers were classified into two groups according to the duration of the smoke-free period. A recent-smoker was defined as one whose duration of smoke-free period was from 2 to 4 weeks prior to the operation (n = 13), and an ex-smoker was defined as one whose duration of smoke-free period was > 4 weeks prior to the operation (n = 121). A never-smoker was defined as one who had never smoked (n = 117).

Assessment of Surgical Procedures
From the surgery records, we obtained information on the type and duration of the surgical procedure performed on each subject. According to the extent of the pulmonary surgery, the procedures were classified into four categories: tumor enucleation (n = 6), wedge resection (n = 124), lobectomy (n = 146), and pneumonectomy (n = 12).

Assessment of Postoperative Course
One anesthesiologist who was unaware of the subjects’ smoking histories reviewed the medical records of all subjects to determine the occurrence of PPCs up to the time of hospital discharge. According to a previous report,5 we defined PPC as development of one or more of the following events: (1) atelectasis prompting bronchoscopy; (2) pneumonia defined by radiographic infiltrates plus at least two of the following: temperature > 37.7°C, WBC count > 10,500/µL, initiation of antibiotic therapy, and/or demonstration of pathogenic organisms; (3) PaCO2 > 50 mm Hg at 24 h after the surgery; (4) air leak or effusion requiring intercostal tube drainage for > 7 days; (5) bronchopleural fistula with large air leak or infection; (6) empyema; (7) chylothorax; (8) hemothorax requiring drainage or reoperation; (9) tension pneumothorax; (10) pulmonary embolism; (11) lobar gangrene; (12) mechanical ventilation > 72 h for any reason; (13) intercostal tube drainage > 14 days for any reason; (14) required fraction of inspired oxygen > 0.6 or alveolar-arterial oxygen gradient > 300 mm Hg 24-h postoperatively.

Statistical Analysis
Frequency distributions were determined for discriminant variables and categorized by smoking habit. {chi}2 test was used to compare the distribution of sex, ASA physical status, pulmonary function tests, and surgical procedures in the subjects by smoking habit. Continuous data are presented as mean ± SE according to smoking habit. The Bonferroni multiple comparison technique was performed to compare the age, BMI, smoking consumption, and duration of surgery in the subjects by smoking habit. The correlation between stepwise improvement of smoking habit and incidence of PPCs was examined through calculation of Spearman’s correlation coefficient by ranks. Logistic regression analysis was used to estimate the odds ratios (ORs) of PPCs for smoking habit and PPCs, controlling for potential confounders. In these analyses, p < 0.05 was considered to be statistically significant. The statistical analyses were performed using software (SPSS version 7.5; SPSS; Chicago, IL).

The 4-week moving averages were calculated to examine the relationship between the length of the preoperative smoke-free period and the incidence of PPCs. Because the numbers of subjects belonging to each week of abstinence duration were too small and variation of incidences in each week was large, the moving average was employed for smoothing such large variation.


   Results
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 Conclusion
 References
 
Characteristics of the Study Subjects in Each Group According to Smoking Habit
In the four groups, female patients comprised the majority only among the never-smokers. The age, distribution of ASA physical status, BMI, and smoking consumption of the four groups were similar (Table 1 ). The percentages of current smokers and ex-smokers with obstructive pulmonary disease according to the pulmonary function test result (FEV1 < 70%) were higher than the percentage in the never-smokers. The distribution of performed operations was similar among the four groups. The mean length of operation in the ex-smokers was longer than that in the current smokers and never-smokers.


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  		Table 1.. Characteristics of the Study Subjects Categorized According to Smoking Habit*

 
PPCs
The PPCs that developed are shown in Table 2 . The most common PPC was air leak or effusion requiring chest tube drainage for > 7 days in all four groups. Two subjects died of PPCs before hospital discharge. One subject, a never-smoker, died of pulmonary embolism; the second subject, an ex-smoker, died of empyema that developed after bronchopleural fistula.


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  		Table 2.. Incidence and Types of PPCs in the Subjects According to Smoking Habits*

 
PPCs occurred in 43.2%, 53.8%, 34.7%, and 23.9% of the current smokers, recent smokers, ex-smokers, and never-smokers, respectively (Fig 1 ). The incidence of PPCs among the current smokers and recent smokers was each significantly higher than that among the never-smokers (p < 0.05 and p < 0.05, respectively). The p values comparing the incidence of PPCs among current smokers vs recent smokers and these two groups vs ex-smokers are 0.509, 0.346, and 0.173, respectively. Spearman’s correlation coefficient by ranks between stepwise improvement of smoking habit and incidence of PPCs was - 0.166 (p = 0.005).



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  		Figure 1.. Incidence of PPCs in patients who underwent pulmonary surgery. The percentage of patients with PPCs in the four groups is shown. *p < 0.05 in comparison with the never-smokers.

 
Moving Average of the Incidence of PPCs
To examine the relationship between the duration of the smoke-free period and the occurrence of PPCs, 4-week moving averages of the incidence of PPC were calculated according to the length of the smoke-free period (Fig 2 ). Beyond the moving average of the 5- to 8-week smoke-free period, the incidence of PPCs gradually decreased. The incidence of PPCs in patients who had a smoke-free period of 9 to 12 weeks or longer approached the incidence in the never-smokers.



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  		Figure 2.. The 4-week moving averages of the incidence of PPCs among the smokers (current smokers, recent smokers, and ex-smokers). W = week.

 
Assessment of Other Factors Related to the Development of PPCs
Many factors have been reported to increase the incidence of PPCs; thus, univariate analysis was performed to evaluate the effect of each factor on the development of PPCs. The ORs of possible risk factors, their 95% confidence intervals (CIs; lower limit, upper limit), and p values are shown in Table 3 . Five perioperative factors, ie, sex, age, smoking status, pulmonary function test (FEV1/FVC < 70%), and duration of surgery, were identified as risk factors for developing a PPC.


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  		Table 3.. Factors Associated With the Occurrence of PPCs in Patients Who Underwent Pulmonary Surgery According to Univariate and Multivariate Logistic Regression Analyses

 
Multivariate analysis was employed to calculate the OR of smoking status after adjusting for possible confounders (Table 3) . Compared with the never-smokers, current smokers and recent smokers had a higher risk for developing a PPC (OR, 2.09; 95% CI, 0.83 to 5.25 and OR, 2.44; 95% CI, 0.83 to 5.25, respectively), although they did not reach statistical significance. On the contrary, the risk of a PPC developing in the ex-smokers was close to that in the never-smokers (OR, 1.03; 95% CI, 0.47 to 2.26).


   Discussion
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
Conclusion
 References
 
This study revealed that smoking was an independent risk factor for PPCs developing in patients who underwent pulmonary surgery, and that smoking cessation prior to the surgery reduced the risk for PPC development. The moving average analysis indicated that the risk for developing a PPC started to decline in patients who stopped smoking 5 to 8 weeks prior to the surgery, and that the risk for a PPC developing in patients whose preoperative smoke-free period was > 10 weeks was similar to that in the never-smokers. The risk for a PPC developing was higher in the current smokers and recent smokers than in the never-smokers, but the risk in ex-smokers was similar to the risk in never-smokers.

Only limited information on the effect of smoking cessation on the incidence of PPCs has been available. Warner et al11 examined the effect of smoking cessation in coronary artery bypass graft surgery patients and reported that abstinence of > 8 weeks prior to the surgery was needed to reduce the incidence of PPCs. Taking the results of the study by Warner et al11 and the present study into consideration, abstinence from smoking of at least 4 weeks, and ideally > 8 weeks, is recommended as preoperative preparation for elective surgery.

Not only long-term but also short-term smoking cessation seems to provide many benefits: prompt reductions in the carboxyhemoglobin and nicotine blood levels, and gradual improvement of mucociliary function and upper-airway hypersensitivity12 and respiratory symptoms. The finding that the incidence of PPCs decreased as the duration of the preoperative smoke-free period increased may be due to these biological improvements after smoking cessation.

Many perioperative factors have been reported as risk factors for PPCs besides smoking.1 4 5 6 8 10 The results of the univariate analysis were compatible with previous reports. In the present study, we classified study subjects into four groups according to the subject’s smoking status. The baseline demographics and characteristics of the four groups were similar except for sex, results of pulmonary function tests, and duration of surgery. Thus, multivariate analysis was performed to control these differences.

The adjusted ORs of both the current smokers and recent smokers were > 2, which indicates a moderately increased risk13 in comparison with the never-smokers, although neither difference was statistically significant. In this study, the numbers of current smokers and recent smokers were small compared with the numbers of ex-smokers and never-smokers. The power of detecting a difference among groups, therefore, seemed weak in this study.

Cigarette smoking is a risk factor for not only PPCs, but also other complications after surgery. Short-term exposure to cigarette smoke reduces the efficacy of the pulmonary immune defense due to impairment of alveolar macrophage function14 ; it also increases the ST-segment depression due to elevation of the blood carbon monoxide concentration.15 Moreover, cigarette smoking increases the risk for perioperative myocardial infarction in patients undergoing a major nonvascular abdominal operation.16 Therefore, smoking cessation should be encouraged for reducing these complications.

A limitation of this study is the definition of smoking status. We did not confirm the smoking status of the patients using biological monitoring techniques such as expired carbon monoxide concentration or nicotine metabolite monitoring. Some current smokers may have declared their smoking status as recent smokers or ex-smokers to medical practitioners, resulting in misclassification in our study. We consider, however, that this misclassification would have overestimated the risk for PPCs among recent smokers and ex-smokers; in other words, this misclassification would have underestimated the effect of preoperative smoking cessation on the incidence of PPCs in the present analysis.


   Conclusion
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 Conclusion
References
 
Our retrospective cohort study indicated that preoperative smoking cessation reduced the risk of a PPC developing in patients who underwent pulmonary surgery, and that smoking cessation should occur at least 4 weeks prior to the surgery to lower the risk for PPCs. However, many smokers continue to smoke up to the time of surgery despite knowing the disadvantages of doing so. Thus, we urge the development of an effective cessation program for outpatients to obtain the necessary length of smoking abstinence, and to make primary physicians aware of such programs.


   Footnotes
 
Abbreviations: ASA = American Society of Anesthesiologists; BMI = body mass index; CI = confidence interval; OR = odds ratio; PPC = postoperative pulmonary complication

This work was performed at Osaka Medical Center For Cancer and Cardiovascular Diseases.

Received for publication November 13, 2000. Accepted for publication March 21, 2001.


   References
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 Conclusion
 References
 

  1. Vodinh, J, Bonnet, F, Lefloch, JP, et al (1989) Risk factors of postoperative pulmonary complications after vascular surgery. Surgery 105,360-365[ISI][Medline]
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  4. Brooks-Brunn, JA (1997) Predictors of postoperative pulmonary complications following abdominal surgery. Chest 111,564-571[Abstract/Free Full Text]
  5. Dales, RE, Doinne, G, Leech, JA, et al (1993) Preoperative prediction of pulmonary complications following thoracic surgery. Chest 104,155-159[Abstract/Free Full Text]
  6. Wong, DT, Cheng, DCH, Kustra, R, et al (1999) Risk factors of delayed extubation, prolonged length of stay in the intensive care unit, and mortality in patients undergoing coronary artery bypass graft with fast-track cardiac anesthesia. Anesthesiology 91,936-944[CrossRef][ISI][Medline]
  7. Pederson, T, Viby-Mogensen, J, Ringsted, C (1992) Anesthetic practice and postoperative pulmonary complications. Acta Anaesthesiol Scand 36,812-818[ISI][Medline]
  8. Bluman, LG, Mosca, L, Newman, N, et al (1998) Preoperative smoking habits and postoperative pulmonary complications. Chest 113,883-889[Abstract/Free Full Text]
  9. Jayr, C, Matthay, MA, Goldstone, J, et al (1993) Preoperative and intraoperative factors associated with prolonged mechanical ventilation: a study in patients following major abdominal vascular surgery. Chest 103,1231-1236[Abstract/Free Full Text]
  10. Thomas, EJ, Goldman, L, Mangione, CM, et al (1997) Body mass index as a correlate of postoperative complications and resource utilization. Am J Med 103,277-283
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  13. Monson, RR (1980) The interpretation of epidemiologic data. Occupational epidemiology ,93-103 CRC Press Boca Raton, FL.
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  16. Gedebou, TM, Barr, ST, Hunter, G, et al (1997) Risk factors in patients undergoing major nonvascular abdominal operations that predict perioperative myocardial infarction. Am J Surg 174,755-758[CrossRef][ISI][Medline]



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