March 31, 2000 (San Francisco) -- An off-the-shelf valve that costs $20, a timer for less than $5, and some transistors might make the difference in engineering an artificial liver that can work for months until a patient's own liver is ready to function properly again.
Experimental artificial liver-assist devices are now used to keep patients whose livers are failing due to acute poisoning alive long enough to find organs that can be used for transplants.
But, Pao Chau, PhD, a professor of chemical engineering at the University of California, San Diego, demonstrated this week how a few changes in a current design might give a patient time for his or her own liver to fight off the poison and function on its own.
"That can take several weeks," says Chau, who spoke here Wednesday at the 219th national meeting of the American Chemical Society. "Right now, the devices being used only work effectively for less than two weeks."
A functioning liver allows a person to lead a normal life, but a transplant patient faces a serious surgery, a long recovery, and a lifelong dependence on medication.
But complicating the development of an artificial liver is the fact that the liver performs numerous duties, including replenishing blood cells. "The liver is a difficult organ to replicate," Chau tells WebMD. The artificial liver devices -- including Chau's revised machine -- work outside the body. The devices are filled with liver cells, either from humans or animals, and perform the tasks of the liver as the patient's blood is routed through the cylinder chambers filled with hollow fibers.
According to Chau, the structure of many of these devices leaves a lot to be desired physiologically. In his machine, he says, the addition of a valve to pinch the hollow fibers shut for about three seconds every minute gives the cells a chance to exchange nutrients better than the present device in clinical trials.
Another artificial liver concept, a type of "bioreactor," is now being tested by VitaGen Inc. of La Jolla, Calif. Chau is working with VitaGen to improve the design of the device.
"This is a promising design," says Vincent Vilker, PhD, bioprocess engineering group leader at the National Institute of Standards and Technology, in Gaithersburg, Md. "But, we are at an early stage of development." Vilker says there are about a dozen different designs of artificial livers being worked on by various scientific groups.
VitaGen uses a patented human liver cell type in its device. The clinical trial at five centers, including one in the United Kingdom, is designed to rescue patients in liver failure until they can receive transplants. Twenty-four patients will be recruited into the study, which is expected to be completed by the end of June. The company has announced plans to begin another trial in August.
- Artificial liver assist devices are used to keep patients waiting for a transplant alive, but one researcher says he believes that these devices could be improved to allow a patient's own liver to heal.
- These devices work outside of the body and are filled with liver cells from animals or humans; the patient's blood is routed through the machine to perform the liver's tasks.
- Making simple changes in the design of these devices, such as adding valves, timers, and transistors, can improve the function.