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CHAPTER 130: The Obesity Epidemic and Critical Care 1305

• Roujeau JC, Kelly JP, Naldi L, et al. Medication use and the risk of • Atelectasis is common in the extremely obese postoperative patient
Stevens-Johnson syndrome or toxic epidermal necrolysis. N Engl
J Med. 1995;333:1600. and, along with sleep-disordered breathing, may lead to respiratory
failure. The early use of noninvasive ventilation in the high-risk post-
• Ruocco V, Sacerdoti G. Pemphigus and bullous pemphigoid due to operative patient may prevent the development of respiratory failure.
drugs. Int J Dermatol. 1991;30:307. • Intubation of the extremely obese patient may be technically chal-
• Seal DV. Necrotizing fasciitis. Curr Opin Infect Dis. 2001;14:127. lenging because of poor visibility of the glottis and decreased oxy-
• Sharp MT, Horn TD: Graft-versus-host-disease. In:Wolff K, gen stores in alveoli from a reduced functional residual capacity.
Goldsmith LA, Katz SI, et al. eds. Fitzpatrick’s Dermatology in • Extremely obese patients should be ventilated in the upright or
General Medicine. 7th ed. New York:McGraw-Hill, 258-267, 2008. semi-upright position to improve respiratory system compliance
• Shiohara T, Inaoka M, Kano Y. Drug-induced hypersensitivity and reduce the work of breathing. Positive end-expiratory pressure
syndrome (DIHS): a reaction induced by a complex interplay between 8 and 15 cm H O may be necessary to prevent atelectasis.
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among herpesvirus and antiviral and antidrug immune responses. • Because the compliance of the respiratory system is reduced in
Allergol Int. 2006;55:1-8. extreme obesity, a high plateau pressure does not necessarily indicate
• Speeckaert MM, Speeckaert R, Lambert J, Brochez L. Acute alveolar overdistention. When using low tidal volume ventilation in
generalized exanthematous pustulosis: an overview of the clini- the management of the acute respiratory distress syndrome, a plateau
cal, immunological and diagnostic concepts. Eur J Dermatol. pressure of 35 to 40 cm H O may be acceptable in some patients.
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20(4):425-433. Epub 2010 June 14. • Ultrasound guidance may be useful in establishing vascular access
in the extremely obese patient.
• Numerous unpredictable alterations in pharmacokinetics have
REFERENCES been described in obesity. Reference to published guidelines for
individual drugs and close monitoring of clinically available serum
Complete references available online at www.mhprofessional.com/hall drug levels are recommended.
• Nutritional support in the form of carefully balanced hypocaloric
enteral regimens is recommended.

CHAPTER The Obesity Epidemic • Interestingly, while obesity is associated with increased all-cause
mortality, the preponderance of evidence suggests that ICU out-
130 and Critical Care comes are not worse in the obese critically ill patient.

Brian K. Gehlbach
John P. Kress An ever-increasing percentage of the inhabitants of developed countries
is obese or overweight. This trend includes men and women and spans
all age groups, including children. Obesity is associated with diabetes
KEY POINTS mellitus, cardiovascular disease, hypertension, and cancer and confers
a reduced life expectancy, particularly in younger and extremely obese
• Extreme obesity presents unique cardiorespiratory challenges in individuals. Extreme obesity is frequently associated with life-threat-
the intensive care unit and frustrates the delivery of routine care. ening cardiopulmonary disease and presents substantial obstacles to
• Extreme obesity leads to a variety of cardiovascular diseases the delivery of routine care. We present a summary of the challenges
through diverse mechanisms. Therefore, a high index of suspicion involved in caring for the extremely obese critically ill patient and
for their presence is warranted in the critically ill patient. highlight physiological principles important to the care of such patients.
• Many patients with extreme obesity suffer from varying degrees of
pulmonary hypertension. Potential etiologies include the obesity THE OBESITY EPIDEMIC
hypoventilation syndrome, the “overlap syndrome” of coexist-
ing obstructive sleep apnea and chronic obstructive pulmonary ■ DEFINING OBESITY
disease, chronic venous thromboembolic disease, and left heart Due to the impracticality of determining body fat composition in the clini-
failure. Diastolic dysfunction is common and may contribute to cal setting, obesity is typically defined as excessive weight relative to body
this pathology. surface area as determined by calculation of the body mass index (BMI),
• Although simple obesity has relatively minor effects on pulmonary calculated as weight in kilograms divided by height in square meters. The
function, extreme obesity may be associated with reductions in correlation between BMI and obesity in most middle-age adults is very
forced vital capacity, forced expiration volume in 1 second, and good, although using BMI as a proxy for body fat is misleading in individu-
total lung capacity. Arterial hypoxemia may be present, particu- als engaged in weight training who have increased muscle mass, and when
larly in the supine position. significant edema is present. The World Health Organization definition of
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• Unrecognized sleep-disordered breathing in the critically ill overweight is a BMI greater than 25 kg/m but less than 30 kg/m , while
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patient may contribute to cardiopulmonary failure. It may also obesity is defined as a BMI greater than 30 g/m . Obesity has been further
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confer increased sensitivity to sedatives and narcotics. subclassified into mild (class I) obesity with BMI 30 to 34.9 kg/m , moder-
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• An increased risk of venous thromboembolism in obesity merits ate (class II) obesity with BMI 35 to 39.9 kg/m , and extreme/severe/morbid
(class III) obesity with BMI 40.0 kg/m or greater. A relatively new category
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an aggressive approach to prophylaxis. of “super obesity” has been proposed for BMI greater than 50 kg/m .
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• Intraabdominal pressure is elevated in obesity, placing the patient
at increased risk for the abdominal compartment syndrome. ■ THE MAGNITUDE OF THE PROBLEM
• Extreme obesity is associated with a significant increase in the per- The prevalence of obesity in the United States has increased dramatically
centage of oxygen consumption attributable to the work of breath- in both men and women over the past 50 years (Fig. 130-1). In 2007-
ing. This decreased respiratory reserve results in a predisposition 2008 data from the National Health and Nutrition Examination Survey
to the development of respiratory failure even after trivial insults. indicated that approximately 34.2% of all US adults were overweight,
33.8% were obese, and 5.7% were extremely obese. There are racial
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