Perhaps the most important step of the preoperative process is patient selection. Certainly, a significant outcomes shift in bariatric surgery can be made by optimizing preoperative selection of patients. The old adage that “the sickest people need our services the most” may be true. However, is the risk that the patient is being exposed to truly going to be returned in benefit? Ideally, patient selection is a dynamic process, rather than a single point-in-time decision. In other words, during an initial evaluation, a surgeon should consider if a patient has any hard contraindications for surgery based on history or physical exam. If a patient is acceptable at that point, that only means they are acceptable to continue the workup for surgery. This workup should be conservative and data informed. Upon closer inspection during the workup process, new information will be added and the benefit-risk equation needs to be adjusted. As with any surgery, the benefits must outweigh the risks, or the person should be informed that they are not a good candidate for surgery. Ultimately, the dramatic increase in the acceptance of weight loss surgery by the public as well as the medical community is likely based on improved outcomes. These outcomes are partially based on improved understanding of the true risks and benefits of weight loss surgery and the informed consent process.

The foundation of bariatric surgery patient selection has traditionally been the National Institute of Health (NIH) Consensus Statement on Gastrointestinal Surgery for Severe Obesity from 1991 [1]. This basically stated that patients with a body mass index (BMI) of 40 or greater, or patients with a BMI of 35 or greater with a weight-related comorbidity, will likely benefit from gastrointestinal surgery as a management of their obesity to a degree that validates assumption of the risk of such surgery. Looking closer at this first step document, if you examine the NIH Website today, you are first met with the following statement: “This statement is more than 5 years old and is provided solely for historical purposes. Due to the cumulative nature of medical research, new knowledge has inevitably accumulated in this subject area in the time since the statement was initially prepared. Thus some of the material is likely to be out of date, and at worst simply wrong” [1]. A new panel was convened a few years ago, and a new consensus statement was scheduled for release in 2013.

Recall that this consensus statement is now more than 20 years old and was based upon data available in 1991; thus data likely accrued in the 1980s—an era where much data was single surgeon or single institution data based on personal practices rather than data-driven practice and often reflected an era where fewer cases were performed with a laparoscopic approach. The data were also reflective of the procedures of the time, some of which are no longer used. Lastly, hospital care and surgery, in general, are both likely safer in all aspects than they were in the 1980s. While this statement remains a reasonable starting point, there are many more data to consider when evaluating patients and when choosing to offer them a bariatric operation. There are multiple factors that make someone who meets the minimum threshold for surgery a less desirable candidate for surgery. While many of these issues are integral to obesity, they must be considered. For starters, multiple studies have shown that increasing body mass index (BMI) and/or weight increases the overall risk factor for both complications and death following bariatric surgery. Livingston et al. showed a BMI >50 kg/m² or weight >350 lb to be predictive of postoperative complications [2] in Veterans Administration (VA) patients, and Gupta et al. found a BMI >60 kg/m² to also be predictive in 11,023 National Surgical Quality Improvement Program (NSQIP) patients [3]. Flum found the same association at “extremes” of BMI over 70 kg/m² [4]. While it seems nonintuitive to consider extreme weight an exclusion criterion for weight loss surgery, it should raise concern in higher BMI patients that these are not average-risk patients. Multiple studies have also shown the association of male gender and hypertension as two additional factors that increase risk of complications and death [3, 5–7].

While gender, BMI, and hypertension seem less avoidable, two selection factors that can be modulated are age and mobility [5]. Someone greater than 50 years old, or possibly as low as 45 years old, not only has a greater risk of developing postoperative complications but also has increased risk of mortality [5, 6]. Intuitively, these patients will also have a less than average chance of enjoying all the benefits of surgery, specifically longevity. While the argument for “physiologic age” versus calendar age is sometimes made, the negative data is based on calendar age. In an era of increasing age of patients through the Medicare National Coverage Decision, many surgeons are asking themselves the question of “how old is too old?” Regardless of their personal answer, an older patient must be educated that they are unlikely to reap the increased longevity that a 40-year-old will, so the additional risk of complications may be less worth it. Additionally, multiple studies have shown that patients with mobility limitations are more likely to have perioperative complications [3–5]. Again intuitively, if mobility issues incapacitate patients from being metabolically active through exercise, they would suffer the same fate as those who do not exercise; specifically they are less likely to achieve a good weight loss result. While the remainder of this chapter describes more individual-patient-specific evaluations, the questions of age and mobility limitations can be determined at the programmatic level. Should there be an age cutoff in your practice? Should you refuse to even consider surgery on someone who cannot ambulate? The literature would support an affirmative answer should you choose that path or at least an informed discussion for the patient regarding these issues should you choose not to enforce cutoffs. Other elements of medical history also predispose patients to being at increased risk. Perhaps the greatest and most consistent throughout studies is history of pulmonary embolism (PE) and/or venous thromboembolism (VTE) [4–7]. This has been found to be predictive of complications and death, thus implying that VTE risk assessment is essential for preoperative selection.

Recently, the Michigan Bariatric Surgery Collaborative published a large multicenter study, which revealed that complications were increased if the following factors were present: prior venous thromboembolism, mobility limitations, age greater than 50, coronary artery disease, pulmonary disease, male gender, and personal history of smoking [5]. Other studies have supported similar findings. Flum et al. using the Longitudinal Assessment of Bariatric Surgery (LABS) data noted that extremes of BMI, inability to walk 200 ft prior to surgery, history of venous embolism, or obstructive sleep apnea were related to the increased risk of adverse events, and the predicted probability of an adverse event for a patient with a previous VTE, sleep apnea, and a BMI of 70 kg/m² was as high as 10 % [4]. In 2007, DeMaria developed the Obesity Surgery Mortality Risk Score (OS-MRS) for bariatric surgery [6]. This utilizes four independent variables found on multivariate analysis to be associated with increased risk of death: male gender, hypertension, BMI greater than 50, and an increased risk of pulmonary embolism to assess mortality risk. An additional factor significant on univariate analysis, age greater than 45, was also used. Presence of each variable gives a patient one point. Risk is then stratified into three levels depending on the presence of 0–1 (A = low), 2–3 (B = intermediate), or 4–5 (C = high) of these variables. The morality risk went from 0.31 % class A to 1.9 % for class B to 7.6 % for class C. This scoring system was then validated in a multi-institutional study [8] and has been replicated at additional single centers [9, 10]. The limitation of this study is that it reflects data generated in primarily open approach bariatric surgical patients and is less applicable to the era when over 96 % of cases are done with a laparoscopic approach.

Ultimately, a surgeon must first decide whether a high-risk patient will be offered surgery. The benefit-to-risk ratio does change for patients who are advanced in years, have mobility limitations, or have other medical issues. Each surgeon has to determine where their comfort zone and cutoff line is. Then it is the duty of a bariatric surgeon to address these issues with the patients who may be borderline candidates for weight loss surgery. The patient should be involved in that discussion. While we want to believe that we can help every morbidly obese patient with surgery, data would imply that many times we are offering more help by not offering the patient surgery.

One of the essential elements of promoting safety in any surgical patient, but especially morbidly obese patients, is adequate evaluation of their cardiac status and cardiac risk preoperatively. It is well known that obesity is associated with multiple comorbidities including hypertension, diabetes, dyslipidemia, and obstructive sleep apnea and all of these diseases can augment cardiovascular risk to the obese person and can contribute to severe cardiovascular diseases such as coronary artery disease, heart failure, sudden cardiac death, as well as arrhythmias. Obesity also increases the total cardiac output and cardiac workload by increasing sympathetic tone and heart rate as well as filling pressure [11]. While multiple studies have discussed a paradoxical protective effect of obesity in terms of cardiovascular events, one should not be pacified into the concept that the morbidly obese patient is a low cardiac risk patient for surgery. Increased BMI is steadily shown to predict increased cardiovascular mortality and that increase can in some cases be two to four times higher than normal weight individuals [12].

Bariatric patients need a focused cardiac history and physical, which should include history of coronary artery disease (CAD), coronary symptoms, and coronary risk factors (hypertension, diabetes, hyperlipidemia, smoking, stress, sedentary lifestyle, etc.). Certainly anyone over the age of 50 years requires extensive evaluation. However, this does not exempt those patients who are less than 50 years old from evaluation.

After obtaining cardiac history and physical, electrocardiogram (ECG) should be obtained universally. The patient under 50 with no cardiac-specific history, no cardiac risk factors other than obesity, and a normal ECG reading will fall into low-risk stratification for a perioperative coronary event. One note on ECG interpretation is to assess QT interval, as obesity is associated with an increased QT and a prolonged QT interval is associated with an increased risk of arrhythmias, Torsade de pointes, and sudden cardiac death. Since many of the medications used in gastrointestinal surgery or psychiatry actually exacerbate, or cause, prolonged QT interval, it is good to know which patients have a long QTi as a baseline.

Any incremental increase in cardiac history or symptoms merits incremental increases in workup. Patients with the presence of compensated ischemic heart disease, prior heart failure, history of cerebral vascular disease, diabetes, or renal insufficiency should likely undergo noninvasive stress testing to accurately determine left ventricular function, according to the American College of Cardiology and American Heart Association guidelines. Obviously, the patient with any unstable coronary symptoms or heart failure, significant arrhythmias, or valvular disease requires an extensive workup, and postponing their bariatric surgery is appropriate until these are worked out. In general, invasive cardiac interventions are only recommended on patients who would otherwise need such interventions regardless of their intention to have surgery, and interventional modalities are not necessarily indicated based only on the fact that the patient is having bariatric surgery. Occasionally, bariatric surgery patients will already have had an interventional cardiac therapy and be on antiplatelet therapy. It is important to recall that the current recommendation for patients who have undergone cardiac stenting, and are on antiplatelet therapy are for the stents, is to remain on that antiplatelet therapy through their operation. Therefore aspirin and possibly even other antiplatelet therapy should not be stopped.

We recommend that accurately assessing cardiac risk may be best left in the purview of a board-certified cardiologist. Bariatric surgeons should collaborate with cardiologists who will provide evidence-driven risk stratification and be available for postoperative care if needed. A prescription stating “cleared for surgery” clearly is not adequate and specific test results should be available to anesthesia and the managing perioperative team when they exist.

Pulmonary embolism (PE) is the second leading cause of death after leaks in patients undergoing bariatric surgery and is responsible for approximately 40–50 % of the fatalities. Rates of venous thromboembolism (VTE), which includes PE and deep venous thrombosis (DVT), vary between 0.2 and 3.5 %. Up to 97 % of patients have a predicted risk of less than 1 % for developing VTE, but identifying the other 3 % of the patients who are at higher risk is critical. Common factors thought to predispose patients to higher risk of VTE are male gender, higher BMI, predicted operative time more than 3 h, older age, and procedure type such as biliopancreatic diversion with duodenal switch (BPD-DS) [13]. In the past, patients thought to be very high risk—such as those with high BMI (>55 kg/m²) and documented to have pulmonary hypertension or obesity hypoventilation syndrome—were recommended preoperative vena cava filter placement [14]. Recently, vena cava filters have been found to be associated with a high chance of complications including filter migration, thrombosis of the vena cava, or fatal pulmonary embolism, and in no group of patients was preoperative placement of a vena cava filter found to be beneficial [15

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