Since 1980, worldwide obesity has more than doubled. In 2008, more than 1.4 billion adults, 20 and older, were overweight. Of these, over 200 million men and nearly 300 million women were obese. Sixty-five percent of the world population resides in countries where overweight and obesity kill more people than underweight. In 2010, more than 40 million children under the age of 5 were overweight.¹

In children, an age- and sex-specific percentile for body mass index (BMI) determines weight status rather than the BMI categories used for adults, because children’s body composition varies as they age and varies between boys and girls.

The Centers for Disease Control and Prevention defines overweight as a BMI at or above the 85th percentile and lower than the 95th percentile for children of the same age and sex.² Obesity is a BMI at or above the 95th percentile for children of the same age and sex.² The World Health Organization definition is as follows: a BMI ≥25 is overweight, whereas a BMI ≥30 is obesity.¹

Obesity is an independent risk factor for acute coronary syndrome, especially in those <40 years old.^3,4 Atypical symptoms may pose a problem with acute coronary syndrome diagnosis.^5,6 About 11% of cases of congestive heart failure are attribuTable to obesity alone.⁷ The physical deconditioning of obesity manifest by orthopnea, dyspnea, and lower extremity swelling is very similar to symptoms of acute congestive heart failure, making diagnosis problematic. Plain chest x-ray findings of congestive heart failure may be obscured by redundant overlying soft tissue and hypoventilation. Brain natriuretic peptide levels are lower in the obese patient than in the nonobese.^8,9 Cardiomyopathy may affect up to 10% of patients with a BMI >40 kg/m² and those with a long duration of significant obesity.¹⁰ Obesity is a risk factor for venous thromboembolism¹¹ and its recurrence once anticoagulation therapy is withdrawn.¹²

The increase in the prevalence of type 2 diabetes is closely linked to the upsurge in obesity. About 90% of type 2 diabetes is attribuTable to excess weight.¹³ Obesity has been strongly associated with insulin resistance in normoglycemic persons and in individuals with type 2 diabetes.¹⁴

The accumulation of fat impairs the function of ventilation in obese children and adults.^15,16,17 Reductions in forced expiratory volume in 1 second, forced vital capacity,^15,16 total lung capacity, functional residual capacity, and expiratory reserve volume are associated with increasing BMI.¹⁸

Obesity is a well-recognized risk factor for obstructive sleep apnea. Forty percent of people who are obese have obstructive sleep apnea, and approximately 70% of people with obstructive sleep apnea are obese.¹⁹

Increased fat deposition in the pharyngeal area along with reduced operating lung volumes associated with obesity reduce upper airway caliber, modifying airway configuration, which in turn increases upper airway collapsibility. Thus, airways are predisposed to repetitive closure during sleep.²⁰ Daytime sleepiness increases and may be associated with accidental trauma.¹⁹

Cor pulmonale and hypercapnic respiratory failure are common. Obesity hypoventilation syndrome (Table 298-1) was first described over 50 years ago.^21,22 The most common symptoms are (1) respiratory failure, (2) severe hypoxemia, (3) hypercapnia, and (4) pulmonary hypertension.^22,23,24

The Broselow tape inaccurately predicts actual weight in one third of children.²⁵ The significance of this inaccuracy has not been studied in depth. A weight-estimation formula based on mid-arm circumference is reliable for use in school-age children and may be an alternative to the Broselow tape.²⁶ The formula is as follows: weight (kg) = (mid-arm circumference [cm] – 10) × 3. When compared to the Argal, Advanced Pediatric Life Support, and Best Guess formulas, Krieser et al²⁷ found that parental estimation of weight was more accurate.²⁷

The concern for equipment weight capacity in the adult patient with obesity is an important determination for imaging. Scales in most EDs have a maximum weight capacity of 150 kg. Mechanized beds that weigh patients are not common in the ED but might be a consideration. Patients with obesity tend to significantly underestimate their own weight. A variety of formulas are available to estimate weight in adults who are obese using height and waist, hip, and arm circumference. The formula developed by Crandall et al²⁸ seems to require the least amount of time and patient manipulation. Two distinct formulas for nonpregnant females and males have been developed as follows:

Improper blood pressure cuff width and circumference will artificially elevate pressure readings. The standard adult blood pressure cuff is too short for patients with an arm circumference of 32 cm or larger. Patients who are overweight or obese will require cuffs larger in size.

The American Heart Association recommends the following cuff widths when evaluating blood pressure in patients who are obese: (1) for arm circumferences ranging from 35 to 44 cm, a bladder measuring 16 cm in width is needed; (2) for circumferences from 45 to 52 cm, the bladder width should be 20 cm; and (3) in patients with short upper arm length, a 16-cm-wide cuff should be used.^29,30

Little evidence-based literature is available for appropriate dosing in obesity, and nearly none is available in the obese child. Fortunately, many drugs used in resuscitation are not lipophilic, and lean body mass is a reasonable dosing guide. Altered physiology is characterized by an increased clearance of hydrophilic drugs, a larger volume of distribution for lipophilic drugs, and a decrease in lean body mass and tissue water content, as compared to their lean counterparts.³¹ Altered mechanics can predispose the morbidly obese to systemic toxicity due to either overdosing or lack of efficacy from underdosing.^32,33

A weight-based medication schedule uses ideal body weight, total body weight, or dosing weight to avoid systemic side effects and lack of clinical efficacy by underdosing. Ideal body weight according to the Devine formula is as follows³⁴:

Dosing weight is an adjusted body weight of overweight or obese patients and is used only for drugs for which there are recommendations specifying that the actual body weight should be adjusted to use in the dose calculation.

Table 298-2 divides select drugs into ideal body weight, total body weight, and dosing weight dosing.³⁵ Fentanyl and the benzodiazepines are lipophilic and have a prolonged half-life in obese patients. With these drugs, the initial dose based on total body weight may be needed, but subsequent doses should be based on ideal body weight.³⁶ It is best to check with a pharmacist for specific dosage regimens.

Vascular access is problematic. Patients who are critically ill and morbidly obese patients require fluid administration often guided by central venous pressure and urine output.³⁷

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