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Obesity is a prevalent medical comorbid condition and its incidence has tripled worldwide since 1975. In 2018, an estimated 42% of Americans were considered obese, with 9.2% being classified as severely obese.1 Obesity accounted for 480 billion dollars in U.S. Healthcare spending in 2016 and more recent estimates are considerably higher.2 The Body Mass Index (BMI), a person’s weight in kilograms divided by the square of height in meters, is the most commonly accepted measure of obesity. In general, morbid obesity is defined as a condition that results from an abnormally high body mass that is diagnosed by having a BMI greater than 40 kg/m², a BMI of greater than 35 kg/m² with at least one serious obesity-related condition, or being more than 100 pounds over ideal body weight (IBW). See Table 29-1 for BMI and obesity classifications.

TABLE 29-1Classification and Definitions – BMI/Obesity


During the properative evaluation of an obese patient, it must be recognized that targeted/goal-directed weight loss will be a challenge. Only those patients who are extremely motivated and have time to achieve significant weight loss will benefit from delaying surgery to lose weight. For most patients, the perioperative clinician should focus on recognizing and if possible, optimizing comorbid medical issues.

As the patient’s BMI increases, the risk of comorbid medical conditions increases. Most of these comorbid conditions and their properative evaluation and optimization are addressed in detail in other chapters.

Cardiac Risk Assessment

While the ACC-AHA guidelines (see Chapter 10 on CAD) do not consider obesity alone as an independent risk factor for postoperative complications, obesity is associated with other cardiac and pulmonary comorbidities that do predict complications and influence preoperative assessment and management.3 These include atherosclerotic cardiovascular disease, heart failure, arrhythmias, hypertension, poor exercise capacity, pulmonary hypertension, obstructive sleep apnea/hypoventilation, and history of venous thromboembolism.

An electrocardiogram (ECG) is commonly done preoperatively but should not be routinely requested for obesity per se without other risk factors. A study of 1029 obese patients found that repolarization, ST segment, and T wave abnormalities were common, as were prolonged PR, QRS, and QTc intervals and a higher degree of left axis deviation.4 However, these ECG findings typically are not independent predictors of postoperative cardiac complications and do not usually change management.

Additional diagnostic testing for coronary artery disease may be limited in obese patients. ...

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