Spotlight Case March 2005

The Hidden Mystery

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Source and Credits• This presentation is based on the March 2005

AHRQ WebM&M Spotlight Case in Hospital Medicine • See the full article at http://webmm.ahrq.gov • CME credit is available through the Web site

– Commentary by: Douglas D. Brunette, MD, Hennepin County Medical Center

– Editor, AHRQ WebM&M: Robert Wachter, MD– Spotlight Editor: Tracy Minichiello, MD– Managing Editor: Erin Hartman, MS

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Objectives

At the conclusion of this educational activity, participants should be able to:

• Appreciate the challenges of caring for morbidly obese patients

• List specific interventions that can be implemented when caring for obese patients

• Develop a rational approach to medication dosing in obese patients

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Case: The Hidden Mystery

A 45-year-old morbidly obese woman with diabetes mellitus was transferred to a tertiary care center for management of abdominal pain, vomiting, and subjective fevers. Upon transfer, the patient complained of diffuse abdominal pain. She was febrile with stable vital signs. Exam revealed a diffusely tender abdomen with chronic erythematous changes extending over her pannus.

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Case (cont.): The Hidden Mystery

Empiric broad-spectrum antibiotics were started. The consulting surgeon recommended abdominal imaging, but the patient was unable to fit in the CT scanner or MRI due to her obesity. She was observed, and her abdominal pain was treated with narcotics.

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Obesity in the United States

• Is defined as having a very high amount of body fat in relation to lean body mass

• Is a major health care problem in the U.S.• Has increased dramatically in recent years• Contributes to numerous negative health

consequences

Source: CDC web site. Flegal KM, et al. Int J Obes Relat Metab Disord. 1998;22:39-47. NIH. Obes Res. 1998;6 Suppl 2:51S-209S

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Body Mass Index

• Body Mass Index (BMI) calculator: – A measure of an adult’s weight in relation to height;

specifically weight in kilograms divided by the square of height in meters

• Overweight: BMI > 25 kg/m2• Obese: BMI > 30 kg/m2• Morbidly obese: BMI > 40 kg/m2

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1991

No Data <10% 10%-14% 15%-19% 20%-24% 25%

1996

(*BMI 30)

Source: Behavioral Risk Factor Surveillance System, CDC.

2003

Obesity* Trends Among U.S. Adults

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Leading Causes of Death the U.S. 2000

Source: Mokdad AH, et al. JAMA. 2004;291:1238-45.

0 100 200 300 400 500

# (thousands)

Tobacco

Poor Diet and Physical Inactivity

Alcohol

Motor Vehicle CollisionCa

us

e o

f D

ea

th

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Challenges in Caring for Obese Patients

• Transportation• Physical exam• Diagnostic imaging• Nursing care• Airway management • Venous access• Medication dosing

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Transportation Challenges

• Need to recruit more personnel• Need multiple slide boards• Requires use of specially designed soft

stretchers, operating room tables, hospital beds

• Must provide special commodes, mechanical lifts, and larger wheel chairs

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Physical Exam Challenges• Pannus and increased thickness of

subcutaneous fat interferes with auscultation, palpation, and inspection

• Positioning the patient is difficult due to decreased mobility

• Blood pressure readings may be inaccurate when wrong size cuff used

• Pain threshold in obese patients may be higher, further diminishing accuracy of exam

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Imaging Challenges

• Standard radiographs—often cannot fit entire field of image into single film

• CT and MRI hindered by weight and circumference restrictions of typically 300-350 lbs

• Ultrasound imaging technically difficult

Source: Varon J, Marik P. Crit Care Clin. 2001;17:187-200; Boulanger BR, et al. J Trauma.1988;45:52-56; Melanson SW, Heller M. Emerg Med Clin North Am. 1998;16:165-89; McKenney KL. Radiologic Clin North Am. 1999;37:879-93.

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Nursing Care Challenges

• Cardiac and pulse ox monitoring less reliable• Wound care technically difficult• Blood draws and IV access hard to establish• Skin care and pressure sore prevention

challenging due to need to move patient often

Source: Hahler B. Medsurg Nurs. 2002;11:85-90; Davidson JE, et al. Crit Care Nurs Q. 2003;26:105-18.

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Airway Management Issues

• Bag-valve mask ventilation more difficult – reduced pulmonary compliance– increased chest wall resistance– increased airway resistance– abnormal diaphragmatic positioning

• Increased aspiration risk– Larger volume of gastric fluid– Increased intra-abdominal pressure– Higher incidence of reflux

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Airway Management Issues

• Obesity limits physicians view of laryngeal structures during intubation – Australian study of 85 difficult intubations: obesity,

limited neck mobility, or mouth opening accounted for two thirds

• Interventions to consider in morbidly obese– Intubate in the semierect position– Use the Intubating Laryngeal Mask Airway or

Combitube

Williamson JA, et al. Anaesth Intensive Care. 1993;21:602-7;

Rocke DA, et al. Anesthesiology. 1992;77:67-73.

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Intubation Laryngeal Mask Airway

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Venous Access Challenges

• Greater number of skin punctures during catheter placement

• Delayed catheter changes with increased infection and thrombosis

• Additional personnel needed for positioning and pannus retraction

Boulanger BR, et al. Crit Care Clin. 1994;10:613-95.

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Medication Dosing Issues

• Marked alteration in pharmacokinetics due to altered volume of distribution

• Volume of distribution is correlated with drug lipophilicity—drugs with higher affinity for adipose have a larger volume of distribution

• Ideally base dosing on results of clinical research data

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Medication Dosing Issues

• When dosing guidelines not provided, base loading doses on drug’s hydrophilic or lipophilic properties, and ideal body weight (IBW) or total body weight (TBW)

• Hydrophilic: – Dosing Weight = IBW + 0.3(TBW-IBW)

• Lipophilic: use TBW• Maintenance dose should be based on IBW if

metabolic clearance is not known

Brunette DD. Am J Emerg Med. 2004;22:40-7.

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Case (cont.): The Hidden Mystery

Six days later, the patient developed fevers, hypotension, and leukocytosis. Exam showed newly identified gangrenous pannus in the deep skin folds. She was taken to the OR for presumed necrotizing fasciitis. Surgical exploration revealed a colocutaneous fistula arising from perforated sigmoid diverticula. The patient died of multiorgan failure after a complex several-month hospital course.

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Quality of Care for Obese Patients

• Documented delays in medical care• Less likely to receive preventative care• Negative physician attitudes and

discrimination• Reported feeling mistreated and

misunderstood by medical personnel• Surgeons possibly more reluctant to operate

Source: Schwilk B. Anasthesiol Intensivmed Norfallmed Schmerzther. 1995;30:99-107; Heinzelmann M. Am J Surg. 2002;183:179-90.

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Obesity and Perioperative Mortality

• Longer operative times• Increased surgical wound infection rate• Higher risk of sepsis

Cruse PJ, Foord R. Surg Clin North Am. 1980;60:27-40;

Reference 29.

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Postoperative Complication Rates by Weight

Schwilk B. Anasthesiol Intensivmed Norfallmed Schmerzther. 1995;30:99-107

0

5

10

15

20

25

30

35

40

%

Normal Obese Morbidly Obese

Weight

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Obesity and Medical Education

• Rotations on bariatric surgery service have improved student’s knowledge base

• Interventions in medical school using video audio and written components have lead to improved attitudes towards obese patients

Source: Nanasiak M, Murr MM. Obes Surg. 2001;11:677-9;Wiese HJ, et al. Int J Obes Relat Metab Disord. 1992;16:859-68.

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Take-Home Points

• Obesity is an epidemic in the US and an increasing percentage of patients will be classified as obese

• Providing excellent care to this population is challenging and requires special attention and often the use of customized equipment

• Airway management is particularly risky and care givers should be prepared to use rescue techniques

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Take-Home Points

• Medication dosing must often be customized to this population

• Care givers must be mindful of potential biases that can influence interactions with patients and the quality of care

• Efforts should be made to increase curriculum at the medical school level focusing on the care of the obese patient