Updated 04 September 2013

Obese patients present diagnostic challenges

Diagnosing sepsis (a severe blood infection) in obese ICU patients can be very difficult as it is not easy to turn them, an intensive care specialist has warned.


Hospitals and critical care clinicians need to adapt to deal with the global epidemic of obesity with 400 million people already classified as obese and a further one billion classified as overweight.

Dr Mary Pinder of the St Charles Gairdner (CORR) Hospital in Western Australia explored the topic Obesity: A diagnostic Challenge and focused on the risks faced by the obese and the challenges of diagnosing sepsis.

Pinder said obesity was an increasing problem in developed and developing countries.

“Obesity combined with sepsis is a really important topic for those of us in critical care because it is almost a perfect storm - the increase in the incidence of obese patients and sepsis being one of the most prominent issues we have to look out for in the emergency care unit,” Pinder said.

“If you get the diagnosis wrong and over diagnose sepsis when there isn’t sepsis we put that particular patient at risk and we put other patients at risk by increasing the risk presented by anti-microbial resistance.”

“We also put patients at risk by missing a true diagnosis and if we under diagnose sepsis obviously that has a significant impact,” Pinder said.

What's the preferred measure of assessing obesity 

Pinder said there was debate regarding whether calculating BMI or measuring waist circumference was the preferred measure of assessing obesity.

Pinder said in terms of weight classification normal weight was a BMI (Body Mass Index) of between 18,5 and 25, overweight was a BMI above 25 and obesity was classified as a BMI over 30. Using waist circumference assessment, a measurement over 94 cm classified men as overweight, while a measurement 80 applied to women. Men with a waist circumference above 102 and women with a waist circumference over 88 were classified as obese.

Risks that obesity poses

Pinder said obese patients were at higher risk of skin, soft tissue and surgical site infections as well as acute pancreatitis. She said research had also shown obesity was a “significant” risk factor for the 2009 H1N1 influenza outbreak and was associated with poor outcome. Additional risks included maternal sepsis, while obesity was an independent risk factor for future sepsis.

“On the upside, there is the obesity paradox. Although these patients are more at risk of certain infections there is evidence that their outcomes are better,” Pinder said.

“Studies are conflicting but there is evidence that obese patients do better than non-obese patients in some conditions, including heart failure and sepsis.”

Pinder said there was a need for further research because there might be other factors involved such as the over-diagnosis of infection and different mg/kg doses of antibiotics.

However, Pinder said diagnosing sepsis in obese patients could be difficult. She it was hard to complete a thorough examination as it was not easy to turn patients.

“Accessing potential samples to do a sepsis screen can be difficult.  Just obtaining a vein to get blood cultures is tricky. The risk of contamination with skin and any fungal skin infections is high and that makes interpretation of the situation difficult,” Pinder said.

“As this is an increasing problem we need to get better at our examination technique, starting with medical students. They should be focused on practicing examination techniques on patients on all size ranges to get that level of expertise.”

Medical treatment needs to be improved

Pinder added that imaging such as x-rays and scans presented a big problem with the main issues revolving around difficulties with patient transport, scanner weight restrictions, image acquisition and interpretation.

“In our hospital when we tried to transport obese patients to the scanner some of the passageways and doorways weren’t wide enough to get the bed through. Some lifts weren’t big enough to accommodate the beds and once you get down to the scanner some of the little corridors with all the equipment they have stacked there are not very friendly. They don’t have any additional hoists or equipment,” Pinder said. “In areas where there is a significant population of obesity these things need to be planned for and in any expansion or modification or building of new hospitals these things need to be put in place,” Pinder said.

Pinder said a major problem had been scanner tables with 150kg to 200kg weight limits as well as technical difficulties with poor quality images, which made it difficult to make a diagnostic decision.

“Manufacturers have modified the new designs so that current models have a much higher weight threshold, which is realistic with the growing problem of obesity,” Pander said.

She added that solutions could be to take images in sections and to use scanning techniques and modification of the scanners to improve quality.

“Some patients end up needing exploratory surgery to make a diagnosis,” Pinder said.

11th Congress of the World Federation of Societies of Intensive and Critical Care Medicine press release


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