Ultrasound prevents blood loss in surgery.

Surgeons have always had a hard time treating wounds or excising tumors in the liver. Designed to filter blood, the organ's spongy, fragile tissue is difficult to close with sutures, so doctors have trouble controlling the bleeding.

Now researchers at the University of Washington in Seattle report success using preoperative ultrasound to prevent internal bleeding in laboratory animals during surgery. They presented their results at this week's joint meeting in Seattle of the Acoustical Society of America and the International Congress on Acoustics. They plan to apply their findings to human patients within a few years.

Over the years, researchers have tested various techniques to stop bleeding in the liver, including cauterization by electric heaters and lasers, says physicist Lawrence Crum of the University of Washington. These methods generally can control bleeding only at the surface of the organ.

Ultrasound, which routinely provides images of internal organs, is being tailored for new uses by researchers (SN: 8/12/95, p. 100). Groups are both administering pretreatment ultrasound and looking for methods to be used during surgery.

Scientists can focus ultrasound inside an organ, heating only the hemorrhaging blood vessels until clots form that close them off. The method could also prove useful in other blood-rich organs such as the spleen and, ultimately, the brain, say the researchers.

"We don't know how well it will work in humans.... So far, the results [in laboratory animals] are good," says Kullervo Hynynen of Brigham and Women's Hospital in Boston. He has used ultrasound to seal bleeding arteries in laboratory animals.

Washington bioengineer Roy Martin reports that his team used ultrasound treatments of 4 minutes or less to heat the livers of four rabbits and six pigs, creating regions of tissue walled off to blood flow The team then surgically removed tissue from those regions.

This pretreatment prevented bleeding in the remaining liver tissue from vessels smaller than 3 millimeters in diameter, Martin reported. The group had less success avoiding blood loss from larger vessels, but those are more amenable to suturing. The researchers plan to track the health and life span of treated animals.

The team employed ultrasound of the same wavelength as is used for diagnostic purposes, but with 20,000 times the intensity, Martin says. At the point of action, the ultrasound reached 2,000 watts per square centimeter.

Success with the method could reduce hospitals' dependence on scarce blood supplies and also shorten operations, Martin notes. It could provide options for patients concerned about contaminated blood or others who oppose transfusions on religious grounds.

The Defense Advanced Research Projects Agency contributed $10 million to the University of Washington research. The defense agency hopes that medics might someday use portable ultrasound devices to stop internal bleeding in wounded soldiers before they reach a hospital, Crum says. Untreated, internal bleeding can lead to death within minutes.

Researchers need to learn how to use ultrasound Imaging to more precisely locate internal bleeding from wounds, Martin adds. The University of Washington scientists hope ultimately to develop a portable ultrasound device--something like the exotic medical devices on Star Trek--that medics could hold outside the patient's skin to both find and treat wounds.