In the Wings: A Game Changer for Lung Transplantation
Date: April 1, 2013
Selecting “organ donor” on your driver’s license application is still a long way off from transplantation. Even after an organ donor dies and the organs become available, they must still meet the criteria for acceptance. And, in the case of lung donations, only 40 percent pass muster.
The rest are discarded, says cardiothoracic transplant surgeon Ashish Shah, usually for somewhat rudimentary reasons, based more on assumption than on quantifiable proof—how the lungs look, how stiff they are or how easily they exchange gas, for instance. But in some cases, Shah says, those lungs could actually be viable. Now, he continues, a procedure called ex vivo perfusion is giving transplant surgeons a chance to determine whether those potentially wasted lungs could actually be put to use. Meanwhile, Shah and his colleagues are studying whether the procedure holds other lung-saving and lifesaving opportunities—possibilities they believe could even negate surgery in some cases.
In the procedure, the lungs are removed from the donor body (hence the term ex vivo) and connected to a special system—a circuit, Shah calls it—that reanimates the lungs by refilling the tissues with blood (perfusion) to see how they respond and whether they improve over the course of time, usually about two hours. The circuit includes a ventilator, a pump and an oxygenator, along with other components that help with filtering and modifying temperature. “In practice,” Shah says, “we can take those rejected organs, put them on a circuit, and some percentage of them will turn out to be usable.”
For now, ex vivo perfusion is clinically available only in parts of Europe and Canada. However, clinical trials in the United States have proven that the procedure is successful, and FDA approval is pending. If it is granted, Shah says, the possibilities created by ex vivo perfusion dramatically expand. In some cases, the procedure could negate transplantation altogether. For instance, he explains, some therapeutics could heal an injured lung, but would be toxic to other parts of the body. But if the lungs could be removed, those drugs could be used to promote healing without placing other organs at risk. Then the lungs could be placed back inside the patients, who in some cases could be safely kept on a ventilator for several days, even a week, while physicians work to repair their lungs.
Shah is also examining the potential of stem cell therapy and linking steroids to nanoparticles. Another possibility, Shah says, is that ex vivo perfusion could increase the geographic distribution of donor lungs. “If you have a recipient in California and a donor in Baltimore, you could put those lungs on the circuit,” he says, “and it would buy you time to get the lungs to a patient who is a closer immunologic match.”
Still, once FDA approval comes through, ex vivo perfusion will only be allowed for assessing lungs for transplantation, at least for the time being. “But we’re keeping an eye on the future potential of repairing people’s lungs,” Shah says, “so that maybe they won’t need transplanted lungs at all.”