Heat May Prevent Wound Infection
Gently warming a patient’s skin before an operation could reduce the risk of surgical wound infection by more than 60%, new research suggests.
As bacteria that commonly infect surgical wounds become increasingly immune to antibiotics--and therefore more life-threatening--experts say the heating technique could be a valuable, simple alternative to giving antibiotics before surgery.
The idea behind the approach, described this week in the Lancet medical journal, is that warming the body before cutting into it improves the distribution of oxygen, enabling the immune system to fight off bacteria that might gather around a wound.
“It’s the first really good demonstration in humans that oxygen affects infections,” said Dr. Thomas Hunt, a wound healing expert and professor emeritus at UC San Francisco, who was not involved in the research.
“The effect of the warmth is equivalent to the effect of prophylactic antibiotics,” he said. “Where postoperative patients are concerned, this is as big a finding as penicillin. I think we’re going to find that this effect is going to save a lot of lives and a lot of cost.”
White blood cells--key components of the immune system--kill bacteria in wounds by swallowing them and bathing them in highly reactive oxygen. To produce this super oxygen, the blood cells need about 50 times more oxygen than they normally do, Hunt said.
Under normal conditions, when tissue is injured by a cut, the blood vessels constrict and the oxygen level in the area drops to a level that hampers the killing of bacteria.
Cold also makes the blood vessels constrict. Anesthetics also cool the body. The body’s normal core temperature is about 98 degrees, but the skin is normally about three degrees cooler.
When the body is cold, such as in an operating room, blood vessels near the skin constrict to direct heat to the core of the body.
The idea is to raise the skin temperature to the normal core body temperature of about 98 degrees. Making it much hotter could be problematic because that speeds the metabolism and could burn the skin.
In the study of 416 surgery patients, one-third were given a perforated plastic quilt that blew warm air onto their bodies, another third were treated with heat where the surgical cut was to be made and the rest got no heat treatment.
To warm the incision site, doctors used an inch-high foam doughnut the size of the incision, with a metal card that radiated heat resting on top.
Nineteen of the 139 people who received no heat treatment, or 14%, got an infection in their wounds. That compared with 13 infections among the 277 in the two heating groups combined, or 5%. That equates to a 64% reduction in the rate of infection.
The study, conducted by scientists at the University Hospital of North Tees in England, found no significant difference between the two heating methods.
Dr. Harriet Hopf, associate professor of anesthesia and surgery at UC San Francisco, said she envisions the warming technique working for nearly all types of surgery.
