Acceptable preservation times vary with the organ. Presently, the time between organ recovery from the donor and transplant recipient is very short and limits the distance that can be traveled to recover donor organs.
Most surgeons prefer to transplant the heart within 5 hours of its removal; the kidney can safely be stored for 40-50 hours, but earlier transplantation is preferred. Most pancreas transplants are performed after 5-15 hours of preservation. Liver transplantations usually are performed within 6-12 hours. The maximal safe interval for the lung to remain ischemic has not been defined. Based on empiric observation, 6 hours is the selected limit (Although laboratory data and isolated clinical reports suggest that good results may be expected with storage times of 8 hours or longer with the use of the newer preservation solutions, increased ischemic time remains a strong and important independent risk factor for poor recipient outcome.)
By Lesley Ciarula Taylor Healthzone.ca
A pig’s heart that started beating again 10 days after it was put in a jar of chemicals could revolutionize organ transplants and rescue thousands who die waiting, a Harvard scientist says.
“We were amazed,” Dr. Hemant Thatte told the Star on Tuesday. “We didn’t expect it to start after 24 hours. When the heart started beating . . . it still gives me goose bumps.”
Thatte, an assistant professor of cardiothoracic surgery at Harvard, and his team soaked the heart in Somah, a mixture of 21 chemicals they have developed to prolong the time organs can spend between removal and transplant.
The limit now is between four and 24 hours, depending on the organ. And hearts are among the trickiest transplants.
“I think this has tremendous potential to help people. I just want to see it succeed with the proper scientific scrutiny,” said Thatte. “It has the potential to cause a paradigm shift in the way transplant surgery is performed.”
Somah, which is Sanskrit for “elixir of immortality,” blends chemicals already approved by the U.S. Federal Drug Administration or, in some cases, already commonly available. In the mix is citrulline malate, currently sold as a performance-enhancing dietary supplement for athletes and based on watermelon rind.
The solution not only preserved organs taken from live pigs, but also kept organs working that came from cadavers, said Thatte.
Ontario is one of four Canadian provinces that allows organ donations after cardiac death. The other provinces and the United States allows donations only after brain death.
So far this year, 323 people in Ontario have received transplants; another 1,615 are on waiting lists, according to the Trillium Gift of Life Network. Organ donations rose by more than 25 per cent in Canada from 1999 to 2008, according to the Canadian Institute for Health Information — but still fell short of demand.
In 2008, about 215 Canadians died while waiting for an organ transplant, CIHI statistics said.
“We don’t have enough donors and organs,” said Thatte. “A major, major point of Somah is that it is able to revive hearts from cadavers. We believe this could be a major source of donated organs.”
Despite his enthusiasm for Somah’s potential, Thatte is aware of its controversy.
In series of articles a few years ago, the prestigious New England Journal of Medicine questioned whether heart transplants after cardiac death are unethical. Because the donated heart is restarted in another body, it raises the question of whether it could have been restarted in the original body.
“We try to do our best in terms of science and then let nature take its course,” said Thatte of the ethical debate.
Thatte’s laboratory, part of the V.A. Boston Health Care System, has worked on transplant research for 10 years. An earlier discovery pioneered Gala, a solution that preserves blood vessels and formed the basis for Somah.
Thatte reported on his work in an article in the journal Circulation late last year.
“It involves a lot of staring at metabolic charts,” said Thatte of his work. Those charts, laced with multi-photon imaging, revealed Somah hearts functioned with minimal decay and damage, particularly compared with the existing organ solution, Celsior.
Transport organs are vulnerable to damage from many sources, including too much oxygen and the creation of ammonia. Somah, said Thatte, counteracted both of these.
The next stage of research would be transplanting the Somah-preserved hearts back into pigs. If that works, human trials would start, said Thatte.
A group of Harvard Business School students excited by the discovery have created a business plan for Somah and created a start-up, called Hibergenica, to raise funding to continue the research.
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