Introduction
Cigarette smoking is the most important avoidable cause of mortality in the United States. The long-term effects of cigarette smoking in causing cardiac disease, vascular disease, pulmonary disease, and a variety of cancers has been recognized for many years now. The benefits of smoking cessation in reducing future risk of these diseases compared with those who continue to smoke are also well documented. Despite this body of knowledge and its wide dissemination, approximately 20% of the adult population continue to smoke. Thus the anesthesiologist is faced with providing preoperative advice and perioperative care to many current smokers. The questions that then arise are whether the smoker is at increased risk of perioperative complications and whether cessation of smoking in the short-term before surgery influences these risks.
There are short-term effects of inhaling cigarette smoke that could cause intraoperative complications. Nicotine causes dose-related increases in heart rate and both systolic and diastolic blood pressure, is a peripheral vasoconstrictor, and increases coronary artery resistance in diseased vessels. Carbon monoxide (CO) inhaled in cigarette smoke combines with hemoglobin to form carboxyhemoglobin (COHb); levels of COHb in smokers’ blood are reported from 5% up to a peak of 20% depending on smoking practice. Smokers under anesthesia have been demonstrated to have higher CO concentrations than nonsmokers. The high affinity of CO for hemoglobin interferes with the oxygen carrying capacity of hemoglobin and moves the oxygen dissociation curve to the left, thus decreasing overall oxygen content and oxygen availability to tissues.
The long-term effects of smoking on the cardiovascular and respiratory systems might also cause perioperative problems. Cigarette smoking is a leading cause of atherosclerotic disease and a major risk factor for coronary artery disease. It is also the leading cause of chronic obstructive pulmonary disease. In addition, of particular relevance to anesthesia, smokers have a significantly greater upper airway sensitivity than nonsmokers.
Evidence
Relationship between Smoking and Perioperative Complications
This section will provide an overview of the literature linking smoking with perioperative complications. These studies are almost exclusively observational in nature. The literature pertaining to smoking cessation in the perioperative period is addressed in the subsequent section. Smoking is an important contributor to perioperative morbidity: In 2003 Moller and colleagues identified smoking as the single most important risk factor for cardiopulmonary and wound-related complications after arthroplasty. Two large database studies have confirmed current smoking as a risk factor for adverse perioperative events. Using a propensity matched analysis of 520,242 patients undergoing noncardiac surgery, Turan and colleagues found that current smokers had significantly greater odds of pneumonia, unplanned intubation and mechanical ventilation, cardiac arrest, myocardial infarction, and stroke. Wound infections, organ space infections, and septic shock were also increased. In a similar study of 393,741 surgeries using a Veterans Affairs database, Hawn and colleagues found that although current smokers were younger and healthier than nonsmokers, they experienced significantly more postoperative pneumonia, surgical site infections, and death.
Pulmonary Complications
An increased incidence of postoperative pulmonary complications in smokers has been recognized since 1944 when Morton reported in a prospective series of 1257 patients undergoing abdominal surgeries that the incidence of pulmonary complications was approximately 60% in smokers versus 10% in nonsmokers. In the subsequent years the finding of increased pulmonary complications in smokers has been replicated in numerous studies, although the reported rates are lower. Smokers have an increased rate of all pulmonary complications, infective pulmonary complications, a higher rate of admission to the intensive care unit after surgery, and a higher rate of prolonged mechanical ventilation. The mechanism behind these increased complication rates is suggested by the multivariate analysis carried out by Mitchell and colleagues on 40 patients undergoing nonthoracic procedures. They found that although smokers had a higher rate of pulmonary complications, smoking per se was not an independent predictor of these complications but that sputum production was. A similar finding was reported by Dilworth and White, who found that the risk of postoperative chest infection in a prospective study of 127 patients undergoing abdominal surgery was markedly higher at 83% if a smoker had evidence of chronic bronchitis compared with 21% in its absence. Nonsmokers had a 7% rate of chest infection.
Airway Complications
Schwilk and colleagues reviewed the occurrence of perioperative airway and respiratory events (re-intubation, laryngospasm, bronchospasm, hypoventilation) in 26,961 anesthesia procedures. They found an incidence of 5.5% in smokers compared with 3.1% in nonsmokers. Interestingly, the risk of all such events was higher in smokers younger than 35 years and particularly in such patients with chronic bronchitis. Smoking was also identified as an independent predictor of bronchospasm in an analysis of a randomized trial of anesthetic agents involving 17, 201 patients.
Cardiovascular Complications
John and colleagues, in an analysis of a database of 19, 224 patients who underwent coronary artery bypass graft (CABG) surgery, identified smoking as an independent predictor of stroke. Smoking was also identified as an independent predictor of operative mortality in patients undergoing internal mammary artery grafting. In patients undergoing abdominal aortic surgery, smoking was found to be an independent predictor of postoperative complications, of which the most common was a deterioration in renal function. In a prospective investigation of the short-term effects of smoking, Woehlck and colleagues reported that patients younger than 65 years with no history of ischemic heart disease undergoing noncardiac, nonvascular surgery who smoked shortly before surgery had a higher rate of ST segment depression than those who did not; however, postoperative outcomes were not reported.
Surgical Complications
Smoking has been identified as a significant risk factor for a number of postoperative surgical complications. Postoperative smoking has been identified as increasing not only the nonunion rate after spinal fusion in orthopedic surgery and the need for reoperation after ankle arthrodesis but also the infection rate after amputation and resource consumption after joint replacement, despite the smokers being younger and with less identified comorbidities than the nonsmokers. Anastomotic leaks after colorectal surgery are more common in smokers than in nonsmokers, and smokers have more complications after plastic surgery to the extent that it has been suggested that plastic surgeons refuse to operate on those who fail to abstain.
Smoking Cessation and Perioperative Complications
The influence of preoperative smoking cessation on perioperative outcomes had been addressed in a number of observational studies, randomized controlled trials (RCTs), and systematic reviews or meta-analyses. These are discussed now.
Observational Studies
In 1984 Warner and colleagues reported a retrospective analysis of 500 randomly selected patients who had undergone CABG in one year. A history of smoking was noted for 456 patients. The rates of perioperative respiratory complications were reported in relation to the reported period of smoking cessation before surgery. Those who continued to smoke up to the time of surgery had a complication rate of 48%; nonsmokers had a rate of 11%. Smokers who reported stopping 8 weeks or more before surgery had a complication rate of approximately 17%, which was not statistically different from that of nonsmokers. Those who stopped smoking for less than 8 weeks before surgery had complication rates not statistically different from those who continued to smoke. When analyzed in 2-week blocks, the rate of complications rose slightly for those who stopped up to 4 weeks before surgery before falling toward that of nonsmokers.
A prospective study followed up 200 consecutive patients undergoing CABG of whom 150 were current or ex-smokers. The findings were similar to the previous study: respiratory complications occurred in 33% of continuing smokers and in 11% of nonsmokers. Of those who had ceased smoking, complications occurred in 57% of those who stopped 8 weeks or less before surgery but in only 15% of those who stopped more than 8 weeks before surgery. Those who had stopped smoking for more than 6 months had a complication rate similar to that of those who had never smoked.
Brooks-Brunn reported on the development of a predictive model for postoperative pulmonary complications after abdominal surgery using a prospective sample of 400 patients. Previously reported risk factors for postoperative pulmonary complications were collected, including length of smoking cessation before surgery. A history of smoking in the 8 weeks before surgery was one of six risk factors in the final model.
A further prospective series reported postoperative pulmonary complications in 410 patients undergoing noncardiac surgery. This group again reported that current smokers had a higher complication rate (odds ratio [OR], 5.5) than nonsmokers or past smokers (OR, 2.9) and that smoking was an independent risk factor.
Nakagawa and colleagues reported similar findings in a retrospective study of 288 patients undergoing thoracic surgery, again focusing on pulmonary complications. The incidence of complications was 24% in nonsmokers, 43% in current smokers (here including those who smoked within 2 weeks of surgery), 54% in those who stopped smoking between 2 and 4 weeks preoperatively, and 35% in those who stopped more than 4 weeks before surgery. These differences persisted with the same ranking when the results were corrected for possible confounding factors. Four-week moving averages showed that the rate of complications in smokers who stopped before surgery reached approximate equivalence with that of nonsmokers at an abstinence period around 8 weeks.
The results of the aforementioned articles raised concerns that pulmonary complications may be increased if patients were to undergo surgery within 4 weeks of quitting; however, subsequent studies indicate that this is not the case. Reporting on pulmonary complications in 300 patients undergoing thoracotomy, Barrera and colleagues found more complications for smokers versus nonsmokers but no significant difference between groups of smokers (quit > 2 months, quit < 2 months and ongoing) nor an increase in recent quitters. Similar findings were reported by Groth and colleagues in 213 patients undergoing pulmonary resection; no difference was seen in overall or specific postoperative complications, including pulmonary complications, among current, recent (quit < 1 month), and distant (quit > 1 month) smokers. In a similar study of 7990 patients from a thoracic surgery database, Mason and colleagues reported that smokers had a 6.2% rate of major pulmonary complications compared with 2.5% in those who had never smoked. ORs for smoking categorized by timing of preoperative quitting (versus never-smokers) were 1.8 for current smokers, 1.62 for those who had quit 14 days to 1 month prior, 1.51 for those who had quit 1 month to 12 months before surgery, and 1.29 for those who had quit more than 12 months prior.
The influence of smoking cessation on wound complications was investigated by Kuri and colleagues in a retrospective study of 188 patients who underwent reconstructive head and neck surgery. They divided patients into five groups based on preoperative smoking history: smokers (smoked within 7 days of surgery), late quitters (abstinence 8 to 21 days before surgery), intermediate quitters (abstinence 22 to 42 days before surgery), early quitters (abstinence 43 days or longer), and nonsmokers. Impaired wound healing was assessed by the need for subsequent surgical intervention. Impaired wound healing was significantly less frequent in the intermediate quitters (55%), early quitters (59%), and nonsmokers (47%) than in the smokers (85%). After multivariate analysis to control for other factors known to influence wound healing, intermediate and early quitters and nonsmokers continued to have a significantly lower risk of impaired healing than smokers. Late quitters had a lower incidence of impaired wound healing (68%) than smokers and a lower risk on multivariate analysis, but these changes were not statistically significant. The authors’ conclusion was that 3 weeks of abstinence is required to reduce wound complications, but a moving average of impaired wound healing incidence they present suggests that this begins declining with 1 week of abstinence.
Taken together, these studies indicate that the risk of complications declines the longer the period of preoperative abstinence. All of the studies can be criticized for being observational in nature and for relying on patient-reported information. In none of the studies is it clear whether any advice to cease smoking was given to the patients involved or whether the observed changes in smoking behavior reflected the patients’ own assessment of the appropriate course of action, which could potentially result in a self-selected patient group. The clinician is then left asking whether advice and interventions to quit smoking before surgery would, firstly, be effective and, secondly, result in fewer complications.
Randomized Studies
Several RCTs have addressed these issues. In an experimental study, Sorensen and colleagues compared wound healing in never-smokers and smokers randomly assigned to either continued smoking or abstinence (with nicotine patch or placebo). Sacral wounds were made at 1, 4, 8, and 12 weeks after randomization. Continued smokers had greater rates of infection than abstinent smokers (and never-smokers) in wounds made 4 or more weeks after randomization. The use of a nicotine patch did not affect outcome.
In a clinical trial, Moller and colleagues performed a multicenter study randomly assigning 120 smokers scheduled for elective hip or knee arthroplasty 6 to 8 weeks preoperatively to either a standard care group or a smoking intervention group. Those in the smoking intervention group were offered weekly meetings with a nurse where they were strongly encouraged to stop smoking. Nicotine replacement was provided along with smoking cessation education. Results were analyzed on an intention-to-treat basis. Thirty-six of the intervention group stopped smoking, and 14 reduced consumption. In the control group only four patients stopped smoking. Postoperative complications were significantly less frequent in the intervention group (18% versus 52%), and the largest effect was seen for wound-related complications. Cardiovascular complications were also more common in the control group (10% versus 0%), but this was not statistically significant. In a comparison of those who reduced their consumption versus those who stopped smoking, the reduction in complications was significant only for those who stopped; those who reduced consumption had the same complication rate as those who continued smoking.
In a similar study, also conducted in Denmark, Sorensen and Jorgensen investigated the influence of a preoperative smoking intervention in patients undergoing colorectal surgery. Sixty patients were randomly assigned to 2 to 3 weeks of either continued smoking or a smoking intervention program similar to that just described. The intervention was successful in decreasing preoperative smoking (89% in the intervention group either quit or decreased consumption versus 13% in the control group). However, no difference in any postoperative complication rates was found.
Lindstrom and colleagues randomly assigned 117 patients scheduled for orthopedic or general surgery to either an intervention group (counseling and nicotine replacement) or standard care 4 weeks preoperatively. The intervention group had significantly less postoperative complications overall.
In a study of brief preoperative intervention (one counseling session 2 to 10 days before surgery) in 130 patients scheduled for breast cancer surgery, randomization to the intervention group had no effect on perioperative complications.
Overall, these studies suggest that smoking intervention in the preoperative period is effective in reducing tobacco consumption and can reduce complications, although possibly only if initiated early enough and if it is of sufficient intensity. One caveat is that, in reported studies, approximately 25% of patients who were invited to participate refused, which may influence the generalizability of the findings.
Systematic Reviews and Meta-Analyses
Five systematic reviews or meta-analyses surveying the literature on smoking cessation in the perioperative period have been published. These are summarized in Table 9-1 . Despite differences in methodology, similar findings are reported. Quitting smoking before surgery decreases total postoperative complications, and complication rates decrease with longer periods of abstinence. Quitting within 4 weeks of surgery did not increase pulmonary complications. Regarding interventions to promote preoperative cessation, the most recent meta-analysis reports that both intensive and brief interventions are effective.
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