Smokers who quit a year or more prior to major surgery had a reduced risk of life-threatening postop complications, researchers found.
Compared with former smokers, odds of postoperative mortality were significantly elevated in current smokers who underwent major surgery by 17% (95% CI 1.10-1.24) but were not significant in those who had quit, according to Faek Jamali, MD, of the American University of Beirut Medical Center in Lebanon, and colleagues.
Risks of 30-day postoperative arterial (OR 1.28, 95% CI 1.17-1.40) and respiratory events (OR 1.21, 95% CI 1.17-1.27) were still elevated in past smokers, but less so compared with current smokers (OR 1.78, 95% CI 1.63-1.93 and OR 1.53, 95% CI 1.47-1.58), they wrote online in the June 19 issue of JAMA Surgery.
The authors noted that little prior research has evaluated the effects of smoking on patients' post-surgical outcomes, though adverse effects of smoking on surgical outcomes has been established.
One of the primary problems of smoking in patients undergoing surgery is getting the patient to quit, noted Barbara Forbes, director of the Dayani Institute for Smoking Cessation and Prevention at Vanderbilt University.
"A lot of research has been done showing the benefits of quitting," she told MedPage Today, adding that "It's the how to get a patient to quit that hasn't been addressed in our current healthcare environment."
"There are a lot of inpatients who don't have tobacco use addressed and those that do are just told to quit, but there's a methodology to getting a patient to quit. There's a lot to be said for coaching and behavioral changes -- those are hard to do, those are time consuming, but that's where the research needs to head," Forbes noted.
The researchers evaluated associations between current and past smoking with risks of postoperative mortality and vascular and respiratory events through a nested cohort of 607,558 adult patients undergoing major surgery in non-Veterans Affairs hospitals in the U.S., Canada, Lebanon, and the United Arab Emirates.
Smoking history data were acquired through preoperative risk assessments and allowed patients to be categorized as current smokers who had smoked or used chewing tobacco within a year prior to surgery, past smokers who had a record of pack-years of smoking but did not currently smoke, and nonsmokers who had never smoked.
Outcomes included 30-day postoperative mortality, arterial events such as myocardial infarction (MI) or cerebrovascular accident, venous events such as deep vein thrombosis or pulmonary embolism, and respiratory events such as pneumonia or unplanned intubation.
Mortality and morbidity for current and past smokers were compared with never smokers. Odds were adjusted in two models -- one that included confounders but not mediating factors and another that included mediating factors, such as diseases that may have been caused by smoking that would cause a patient to stop smoking.
Another logistic regression model also divided patients into smoking quintiles based on pack-years of smoking.
Patients were mostly women (57.3%), most had never smoked (66.4%), and had a mean age of 55.7. Around 20% were current smokers (20.6%) and 13% were past smokers.
After adjusting for confounders in model one, "only current smokers had increased odds of mortality after surgery" by 21% (95% CI 1.14-1.28). This risk dropped to 17% after adjustment for mediators (95% CI 1.10-1.24).
Compared with nonsmokers, current and past smokers had a significantly increased risk of arterial and respiratory events after adjusting for confounders. These risks remained significant when adjusted for mediators. In the second model, risks of arterial events were increased by 65% in current smokers (95% CI 1.51-1.81) and by 20% in past smokers (95% CI 1.09-1.31), while risks of respiratory events were increased by 45% in current smokers (95% CI 1.40-1.51) and 13% in past smokers (95% CI 1.08-1.18).
Adjusted odds of mortality and adverse events were "noted across all age groups, in both sexes, in inpatients and outpatients, in those who underwent surgery with general or other types of anesthesia, in elective and emergency cases, and in various surgical subspecialties."
This was compared with past smokers, who "did not have increased odds of mortality even with a cigarette smoking history of at least 50 pack-years," while arterial and respiratory events were only noted in past smokers who had smoking histories of 50 pack-years or greater and 20 pack-years or greater, respectively, they wrote.
A systematic review of present and past smoking on adverse effects on neurosurgical outcomes by John Maa, MD, of the University of California San Francisco, and colleagues, supported the findings of Jamali and co-authors.
In the Journal of Neurosurgery, the authors noted that smoking can cause perioperative complications through tissue hypoxia, thrombogenesis, and vasoconstriction. Additionally, microvascular dysfunction resulting from smoking can impair wound healing.
These findings were coupled with similar cardiopulmonary effects as seen in the research by Jamali and colleagues.
The authors also reached a similar conclusion as the prior study, noting that "accumulating evidence indicates that smoking cessation can reduce the higher perioperative complications risk seen in active smokers and possibly improve long-term outcomes." However, they also noted that additional research should look in further depth at neurosurgical outcomes in present and past smokers.
Jamali and co-authors noted that their study was limited by excluding patients who had quit smoking less than a year before surgery from the past smoking group, as well as hospital effects that could not be controlled for.