Medical Student Notebook: Smoking-associated Postoperative Complications of Bariatric Surgery: A Review

| October 1, 2018 | 0 Comments

by Hemen Muleta, BA

Column editor

Daniel B. Jones, MD, MS, FASMBS
Professor of Surgery, Harvard Medical School, Vice Chair, Beth Israel Deaconess Medical Center, Boston, Massachusetts

Featured student

Hemen Muleta, BA
Medical Student, Harvard Medical School, Boston, Massachusetts

Funding: No funding was provided for this article.

Disclosures: The author reports no conflicts of interest relevant to the content of this article.

Bariatric Times. 2018;15(10):22–23.

AbstractAs obesity and tobacco use persist as leading causes of morbidity and mortality in the United States, the effects of smoking on outcomes of bariatric surgery remains an interesting and relevant area of study. This article summarizes the literature on smoking and bariatric surgery focusing on the top two most popular surgical options, sleeve gastrectomy (SG) and Roux-en-y gastric bypass (RYGB). It will also outline the gaps that remain in the literature and areas that remain unknown. Overall, smoking is associated with both early and long-term complications after bariatric surgery. Although these early complications seem to apply to all bariatric surgeries, smoking appears to be significantly associated with long-term complications of Roux-en-y gastric bypass.


Globally, cigarette smoking is one of the leading causes of morbidity and mortality. It is estimated that cigarette smoking is responsible for more than 480,000 deaths annually in the United States alone and over 6 million deaths annually across the world.1 It is also well established that obesity leads to an increase in all-cause mortality and an increase in diseases such as type 2 diabetes mellitus (T2DM), obstructive sleep apnea (OSA), coronary heart disease, and hypertension.2 Currently, bariatric surgery is the best known treatment for the reversal of obesity related outcomes.3 As such, the intersection between bariatric surgery and tobacco use is an interesting field of study. This article will outline the proposed pathophysiology by which cigarette smoking influences postoperative outcomes, review the literature on what is known regarding the impact of smoking on postoperative complications of bariatric surgery, and comment on the future areas of research for bariatric surgery.

The impact of smoking on postoperative outcomes has been described as far back as 1944.4 There are several mechanisms by which smoking is proposed to increase risk of postoperative complications that relate to both the acute effects of smoking on the human body and the long-term disease processes related to smoking. In the acute setting, smoking leads to altered wound healing through several mechanisms. Smoking damages endothelial cells, leading to an increase in the permeability of the vascular system, which can cause increased swelling and vasospasms. Due to the activation of the sympathetic nervous system, platelet aggregation increases and prostaglandins decrease, which leads to further breakdown of tissue barriers. An increase in the availability of carbon monoxide binding to hemoglobin also decreases the oxygen carrying capacity of blood, therefore interfering with normal tissue healing. The nicotine in tobacco has also been known to contribute to states of hypercoagulability and hypoxia.5 Additionally, the effects of smoking on the pulmonary system include an increase in airway inflammation and overall blunting of the pulmonary immune system by inhibiting alveolar macrophages and ciliary clearance.6

Numerous studies also describe how these effects of smoking may directly impact bariatric surgery outcomes. In a study of 41,445 patients who had undergone both open and laparoscopic bariatric surgeries, excluding adjustable gastric band, between 2005 and 2010, smoking was associated with an increase in several postoperative outcomes. Compared to nonsmokers, patients with a history of smoking within one year prior to surgery had an increased risk of prolonged intubation, pneumonia, sepsis, and longer hospital stays. For those who underwent open operations, there was also an increase in organ space infection.5 Interestingly, this study did not show any 30-day mortality differences between smokers and nonsmokers. Other studies have established similar conclusions. In a study of 49,772 patients who underwent either Roux-en-y gastric bypass (RYGB) or laparoscopic sleeve gastrectomy (LSG),7 an increase in 30-day postoperative complications was seen in recent smokers (defined as quitting history within 3 months to 1 year prior to surgery) as opposed to never smokers and former smokers (defined as those who quit at least one year prior to surgery). In the category of recent smokers, the odds ratio for severe complications following RYGB was 1.34 (confidence interval [CI]: 1.01–1.77) as compared to never smokers. Interestingly, there were no significant differences in 30-day complications between former smokers and never smokers following RYGB, perhaps linking active tobacco use with postoperative outcomes. The study also concluded that there were no significant differences in complication rates in the three arms for those who had a LSG.7

Not surprisingly, tobacco use also seems to be directly related to specific pulmonary postoperative complications in bariatric surgery patients. Among 32,889 patients who underwent bariatric surgery, including open and laparoscopic RYGB, laparoscopic adjustable gastric banding (LAGB), biliopancreatic diversion with duodenal switch (BPD-DS), and vertical banded gastroplasty (VBG), researchers observed that smoking within one year prior to surgery increased the risk of postoperative pneumonia (adjusted odds ratio [AOR]: 1.56; CI: 1.06–2.29).8 Postoperative pneumonia, in turn, carried a 6.4 percent 30-day morbidity and 4.3 percent mortality rate. It should be noted, however, that this study did not include patients who underwent LSG.8

Nonetheless, other studies have found significant differences in the rates of early postoperative complications of LSG. In a study of nearly 34,000 patients who underwent LSG,9 a smoking history within one year pre-operatively increased their risk of composite and serious 30-day morbidity compared to nonsmokers. These composite (4.3% vs. 3.7%) and serious outcomes (0.9 vs. 0.6%) for smokers and nonsmokers, respectively, included reintubation, stroke, cardiac arrest, myocardial infarction, sepsis, acute kidney injury (AKI), pulmonary embolism (PE), and 30-day mortality. However, it should be noted that the mortality rates for both the smoking and nonsmoking groups were small, 0.2 percent and 0.1 percent, respectively.This study also found that the length of stay and readmission rate were comparable among the two groups.9 

While most studies focus on immediate and 30-day postoperative complications related to smoking, the most significant long-term complication in the literature seems to be the development of marginal ulcers. Smoking is a well-established risk factor for the development of marginal ulcers, particularly at anastomotic sites, and can lead to further complications, such as perforations. For example, in one study that evaluated 350 patients at least two years postoperatively from laparoscopic RYGB,10 6.6 percent presented with symptomatic marginal ulcers. For these patients, active smoking, corticosteroid use, and use of nonsteroidal anti-inflammatory drugs (NSAIDs) were each independently associated with the development of symptomatic marginal ulcers.10 Several other studies have reported similar findings, including a 2006 study which found that among patients presenting with upper gastrointestinal symptoms within 12 months of RYGB, current smoking status had a significantly large association with the discovery of a marginal ulcer (AOR: 30.6; CI: 6.4–146).11 This was significantly higher than the association of NSAID use with marginal ulcers (AOR: 11.5; CI: 4.8–28).11 A prospective study of 3,430 patients also found that while the overall rate of perforation of marginal ulcers was low at one percent of the total study population, more than half of those who presented with a marginal ulcer (18/35) were current active smokers.12 This evidence suggests that smoking might be the leading risk factor for the development of marginal ulcers and subsequent complications among patients who undergo RYGB.

As LSG becomes more popular, further investigations are needed to understand the long-term effects of smoking on those who undergo this procedure. Currently, this discussion is limited to research on weight loss outcomes. In one study that compared nonsmokers, former smokers, and current smokers six-year after undergoing LSG, postsurgical weight loss was independent of smoking status.13 Further research is also needed to better identify the optimal amount of time to implement smoking cessation prior to undergoing bariatric surgeries. While various studies have shown significant differences in immediate postoperative complications in those who quit smoking one year and even 30 days prior to surgery, there is currently no consensus. At the moment, the standard of care recommended for bariatric patients is six weeks of smoking cessation prior to surgery, a guideline that comes out of a meta-analysis of general surgery patients.14 However, given the health complications unique to bariatric patients, a more tailored timeline for cessation may be beneficial.

Finally, as the practice and legalization of cannabis evolve, the impact of cannabis use on bariatric surgery opens an interesting and unexplored field of study. Currently, cannabis is often categorized under “illicit drugs” and may actually hurt patients’ eligibility for bariatric surgery in some centers. Some also argue that, given the literature on the increased risk of substance abuse post bariatric surgery, cannabis may serve as a “gateway” to other substances.15 However, the first step in clearly delineating such a relationship would be to document cannabis use more specifically in order to prevent the disqualification of otherwise eligible patients and to facilitate the study of postoperative complications that might be associated with cannabis. 

As bariatric surgeries expand nationally and become well established as one of the most effective treatments for obesity, the impact of tobacco use in this population is an important area of focus. Smoking is also correlated with both respiratory and nonrespiratory complications post bariatric surgery. While most of the complications post-bariatric surgery described in the literature focus on 30-day early complications, smoking also poses a risk for the development of marginal ulcers past this 30-day period, particularly for those who undergo RYGB. Given this risk, providing patients with smoking cessation counseling and support prior to an operation might be beneficial. Overall, bariatric surgery presents a field of study with many unanswered questions, including the optimal timing of smoking cessation as well as the systematic documentation, management, and outcome of patients who use cannabis.


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