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发表于 2004-7-17 19:41
[B]New Possibilities for a New Millennium [/B]
Frederick Daniel Watanabe, MD, FAAP
Cedars-Sinai Medical Center
Modern medicine has learned to support many failing organs with machines: dialysis for kidney failure, respirators for breathing and pacemakers for the heart. However, when the liver becomes too damaged to sustain life, the only medical recourse is transplantation. For over 50 years, physicians and scientists have been attempting to develop an artificial liver. This article focuses upon current devices made to provide artificial liver support.
There are two basic types of artificial liver devices: filter-based and living cell-based. The devices presently being used or tested in humans are summarized in Table 1.
Filter devices have never been shown to change patient outcome in a large clinical trial, though there has been sporadic evidence of success. The HemoTherapies System (HemoCleanse, Inc, West Lafayette, Ind.) and the MARS dialysis device (Teraklin AG, Rostock, Germany) are "modified" dialysis machines. Confusion frequently arises with the HemoTherapies System because it has "FDA approval." FDA rules permit using this kidney dialysis machine for liver disease as long as it is safe. Thus the "FDA approval" is for safely, not effectiveness.
Most liver experts agree that living cells are needed in addition to filters: a living liver cell does something to make humans healthy. Scientists refer to these machines that contain living cells as a bioartificial liver. Three devices are undergoing initial safety trials (Phase I). Two contain liver cells from a pig while the VitaGen machine uses human cancer cells.
The HepatAssist (Lexington, Mass) - originally tested in Southern California at Cedars-Sinai Medical Center - is the only device that is beyond the safety trials. Currently, the HepatAssist is being studied in critically ill liver patients with less than a 20% chance of surviving. If the HepatAssist is proven to work, it will be the first bioartificial liver certified by the FDA. Final results of the study are anticipated this year.
Today, the future is as bright as ever for artificial liver support. No less than six different systems should be in use or clinical trials this year. Filter-based products are commercially available; however, the published data does not indicate that these machines will significantly help patients. Fortunately, cell-based therapies are now in clinical trials. Most of the cell-based systems are still in safety studies. However, the HepatAssist is close to completing the final steps toward FDA approval. All these devices represent tangible evidence that artificial liver support will provide new treatment possibilities for the new millennium.
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