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Research Into Heat, Bleeding May Help Soldiers, Others

Researchers in Dallas hope their clinical tests will improve care for soldiers in the Middle East and even for construction workers, firefighters and other outdoor workers who sustain bleeding injuries in the Texas summer heat.

Becky Lucas, post doctoral fellow, assists in the set up of the environmental chamber, Antionne Williams, 31, volunteer research subject,  lies in for heat exposure as part of  research at the Institute for Exercise and Environmental Medicine at Presbyterian Hospital in Dallas, Friday September 30, 2011.

DALLAS — It felt like a ton of bricks on his chest, Antionne Williams said, downing a Coke and recovering after 15 minutes secured in a coffinlike box.

Researchers raised his body temperature so it was equal to a low-grade fever. Then, they applied so much suction to the box that the blood in Williams’ torso pooled in his legs.

The point of the exercise? To simulate the effects of hemorrhaging wounds that injured soldiers might experience in the Afghan desert.

Researchers at the Institute for Exercise and Environmental Medicine at Texas Health Presbyterian Hospital Dallas hope the experiment on Williams will help them better understand how heat stress affects the body’s reaction to hemorrhaging wounds. That knowledge could improve care for soldiers in the Middle East and even construction workers, police officers and firefighters who sustain bleeding injuries in the Texas summer heat.

The research, part of a joint venture with the University of Texas Southwestern Medical School, is led by Craig Crandall, a professor at the medical school and a thermoregulation expert.

Crandall and his team have conducted 10 clinical trials during which they have simulated hemorrhaging conditions in about 150 test patients, including Williams, 31. For four years, Crandall’s research has been financed by a National Institutes of Health grant worth about $290,000 annually, but only part of that goes to this study.

The researchers simulate hemorrhaging by using negative pressure to force blood to pool in a test patient’s lower limbs, leaving the chest and torso with less blood temporarily. To create negative pressure, the patient’s lower half is squeezed into a wood box secured at the waist with a harness. The box is sealed and a pump creates suction so strong it pulls blood from the patient’s core to the legs. At the same time, the researchers put the patients in a chamber that maintains their core temperature as high as 102 degrees Fahrenheit.

Williams, who estimated he had been in “the box” five to eight times said this time was particularly unpleasant. “Sometimes I just feel a little warm, but this time I felt like I was trapped, like there were a ton of bricks on my chest,” he said.

After five years of tests, researchers discovered that the body’s natural cooling mechanism, which increases blood flow to a heat-stressed patient’s skin, also contributes to increased blood loss from hemorrhaging wounds. As a result, less blood may flow to the vital organs and the brain.

Doctors have long known the consequences of hypothermia for patients with bleeding injuries; standard emergency-care practices call for warming hemorrhaging patients to avoid shock.

But Crandall’s team found that higher temperatures might also lead to complications for patients with bleeding injuries.

He believes the research will redirect the focus of urgent care for bleeding injured patients in high temperatures and, during those critical moments, increase blood flow to vital organs.

“There’s nothing you can do about the blood on the ground,” he said. But by cooling a patient externally, “you can redirect the blood from the skin back to the vital organs.”

Editor's Note: This story has been corrected to reflect that during the clinical trial, the subject's core temperature is raised before suction is applied. The original story reversed the order of those processes.

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