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Obesity protects from respiratory distress, death after surgery

Kathleen Blanchard's picture
Obesity and ARDS

Being obese doesn’t have a down side when it comes to respiratory complications that can lead to death after surgery. Understanding why obesity protects from respiratory insufficiency (RI) and adult respiratory distress syndrome (ARDS) post operatively could lead to interventions that help normal weight patients undergoing surgery.

Researchers aren’t sure how obesity helps the lungs after surgery

One theory is that being obese protects patients because they simply have more energy stores to recover from acute illness

Researchers aren’t sure why being obese offers protection from life-threatening post-operative complication of ARDS, but it may also be that fat cells act as a depository for inflammatory cytokines.

Stavros G. Memtsoudis, M.D., Ph.D., an anesthesiologist at Hospital for Special Surgery, who led the study said:

"Some of the inflammatory proteins may adhere to fatty tissue and thus be removed from the circulatory system. This in turn may reduce the inflammatory process. There is some laboratory evidence that suggests that." A third hypothesis is that doctors are often more vigilant with obese patients, because they worry they will have more health problems, and this extra vigilance could be the cause of the "obesity paradox.

When the condition develops, inflammatory molecules are released in the lung tissue. The result is poor exchange of oxygen from swelling and fluid buildup that can lead to the need for ventilator support and death.

The study

For the study, researchers looked at a large database sponsored by the Agency for Healthcare Research and Quality that included patients undergoing surgeries that put them at high risk for RI/ARDS.

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Among 9 million patients identified who underwent open abdominal surgeries, hip and knee replacement, spine, heart, chest, complex vascular, and surgeries of the head and neck, 5.48% of had a diagnosis of obesity.

Compared to 2.01 percent of non-obese patients who developed adult respiratory distress syndrome post-operatively, just 1.82 percent of obese had lung complications.

Patients that were obese and developed RI/ARDS also had lower death rates, compared to non-obese, which were 5.45% versus 18.72% respectively. They were also less likely to need mechanical ventilation than non-obese patients with respiratory complications after surgery, but if they did, they were less likely to die.

Dr. Memtsoudis said, if just being vigilant is how obese patients fare better when it comes to respiratory complications from surgery, "extending…use of resources to monitor non-obese similarly to obese patients” might be enough.

"In order to develop an intervention to prevent or treat a disease, you have to be able to understand the mechanism," Dr. Memtsoudis said. "Maybe developing an intervention that mimics the physiological process that seems to offer natural protection to obese patients, such as the binding of cytokines and other inflammatory mediators to fat could have a protective effect."

Respiratory distress after surgery has remained a problem for the last two to three decades.

“Although the assumption is that patients with obesity have worse perioperative and long-term outcomes, this study clearly shows that in the setting of RI/ARDS, this is not the case and obesity might actually be protective in this setting", explains Memtsoudis.

The authors hope understanding the ‘obesity paradox’ when it comes to post-operative RI/ARDS, which has a high mortality rate, can lead to new research that can improve care. Adult respiratory distress syndrome can cause long-lasting lung damage and cognitive problems for those who experience critical illness.

Image is patient with ARDS
Credit: Wikimedia Commons



I wonder if the results are due to a smoking habit as the causative factor by the individuals with low BMI's.
Dr. J, Good question! You would think that would be controlled for though, in any well-designed research, right?