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Current estimates of the prevalence of obesity are that a quarter of adult Canadians and one third of Americans are considered obese with approximately 3% being morbidly obese. With the proportion of patients with a BMI>30 growing every year, you’re likely to manage at least one obese patient on every ED shift. Obese patients are at high risk of developing a host of medical complications including diabetes, hypertension, coronary artery disease, peripheral vascular disease, biliary disease, sleep apnea, cardiomyopathy, pulmonary embolism and depression, and are less likely compared to non-obese adults to receive timely care in the ED.

Not only are these patients at higher risk for morbidity and mortality, but obesity emergency management is complicated by the patient’s altered cardiopulmonary physiology and drug metabolism. This can make their acute management much more challenging and dangerous. To help us gain a deeper understanding of the challenges of managing obese patients and elucidate a number of important differences as well as practical approaches to obesity emergency management, we welcome Dr. Andrew Sloas, the founder and creator of the fantastic pediatric EM podcast PEM ED, Dr. Richard Levitan, a world-famous airway management educator and innovator and Dr. David Barbic a prominent Canadian researcher in obesity in emergency medicine from University of British Columbia....

 

Written Summary and blog post prepared by Dr. Michael Kilian, edited by Dr. Anton Helman, Sept 2015

Obese patients are not just large adults!

Vital Signs in Obesity Emergency Management

Blood pressure readings can be falsely reassuring in obese patients as the cuff often overestimates BP. A 'borderline' BP could represent a shock state in an obese adult. If you recognize that a blood pressure within the normal range does not rule out shock in an obese patient who appears unwell, you are more likely to begin early resuscitation and initiate appropriate treatment. In order to obtain a more accurate reading, consider placing an early arterial line to obtain and trend accurate BP readings over time.

The Shock Index can be a helpful tool in making a diagnosis of occult shock in obese and non-obese patients. The calculation requires accurate readings for prognostication.

Shock Index = HR/SBP

Any number > 1 suggests occult shock
Shock index calculator interpretation and references at MDCalc

 
ECG Alterations in Obesity Emergency Management

The ECG in obese patients also differs from the average adult. The ECG of an obese patient is more likely to show:

1. Low voltages - due to the size of their chest wall; note that it is important to rule out a pericardial effusion when you see low voltages, before attributing these findings to adipose tissue alone

2. Longer QT intervals - rarely >500ms as a result of obesity alone

3. Signs of Left Ventricular Hypertrophy (LVH) - consider an echocardiogram to rule out obesity-associated cardiomyopathy

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Low Voltage ECG. Courtesy of Lifeinthefastlane.com
 
Important Pathophysiologic Considerations in Obesity Emergency Management

* Decreased respiratory reserve is secondary to diminished total lung capacity and functional residual capacity. The decreased reserve compromises an obese patient’s ability to tolerate respiratory insults such as pneumonia
* Increased airway pressures are a result of increased airway resistance (heavier chest walls, increased abdominal girth, atelactatic lung bases). The increased pressures lead to:

* Smaller oxygen reserves at baseline
* Increased work of breathing
* Shorter time to desaturation during induction and a shorter Safe Apnea Time

* Higher incidence of hypoxemia and hypercapnia at baseline