Technology that allows organs to work outside the body

Perfusion keeps the donor organ alive outside the body, giving surgeons extra time and increasing the number of possible transplants.

In a sense, the human liver in the operating room at Northwestern Memorial Hospital in Chicago was alive. Blood circulating through its tissues delivered oxygen and removed waste, and the organ produced bile and proteins needed by the body.

But the donor had died the day before, and the liver lay in a plastic device. The organ owed its vitality to this machine, which preserved it for transplantation to a patient in need.

“It's a little like science fiction,” says Dr. Daniel Borja-Cacho, a transplant surgeon at the hospital.

Surgeons are experimenting with organs from genetically modified animals, hinting at a future where they could become a source for transplants. But the field is already undergoing a paradigm shift, driven by widespread technology that allows doctors to temporarily store organs outside the body.

Perfusion, as it is called, is changing every aspect of the organ transplant process—the way surgeons work, the types of patients who can donate organs, and the outcomes for recipients.

Most importantly, surgical programs that have adopted perfusion have enabled the transplantation of more organs.

Since 2020, the volume of liver transplants at Northwestern University has increased by 30 percent. In 2023, the number of lung, liver and heart transplants in the country increased by more than 10 percent, one of the largest annual increases in recent decades.

Without blood flow, organs quickly deteriorate. This is why doctors have long considered the ideal organ donor to be someone who died under circumstances that stopped brain activity, but whose heart continued to beat, keeping the organs viable until they were matched to recipients.

To minimize trauma to organs after they are removed from donor blood and before they are connected to recipient blood, surgeons cool them to just above freezing, significantly slowing metabolic processes.

This extends the period when organs can be transplanted, but only for a short time. The liver remains viable for no more than 12 hours, and the lungs and heart – no more than six.

Scientists have long experimented with methods of preserving organs under more dynamic conditions, at higher temperatures and perfusion with blood or other oxygenated solutions. After years of development, the first perfusion-assisted lung preservation device received FDA approval in 2019. Heart and liver perfusion devices were approved in late 2021.

The devices essentially pump blood or oxygenated fluid through tubes into the blood vessels of the donor organ. Because the cells in the perfused organ continue to function, doctors can better assess whether the organ will survive in the recipient's body.

Based on this information, transplant surgeons have begun using organs from older or more severely ill donors that they might otherwise discard, said Dr. Chris Croom, a professor of surgery at the Mayo Clinic in Florida. “We're using organs that we would never have taken before, and we're seeing good results,” he says.

Perfusion also eases the grueling process of organ removal and transplantation, hours-long operations that doctors often perform at speed, starting work in the middle of the night and moving on to the next one as soon as the previous one is completed.

Surgical teams can now remove the organ, perfuse it overnight, sleep peacefully, and complete the transplant in the morning without fear that a delay in transplantation will damage the organ.

Perhaps most importantly, perfusion opened up the possibility of organ donation for comatose patients whose families had withdrawn life support, allowing their hearts to eventually stop. Every year, tens of thousands of people die this way after their circulation stops, but they rarely become donor candidates because their organs are deprived of oxygen during the dying process.

Surgeons now perfuse these organs, either by transferring them into a machine or, less technologically, by recirculating the blood to that area of ​​the donor's body. This makes them much more attractive for transplantation.

Since 2020, the number of liver transplants performed after a donor's death has doubled, according to an analysis of data from the United Network for Organ Sharing, the nonprofit organization that governs the transplant system in the United States.

Once upon a time, surgeons never used the hearts of such donors due to the sensitivity of this organ to oxygen deprivation; in 2023, thanks to perfusion, they have transplanted more than 600 hearts.

By tapping into this new pool of donors, transplant centers say they will be able to quickly find organs for the large number of patients who need them urgently. Dr. Shimul Shah says the organ transplant program he directs at the University of Cincinnati has virtually eliminated the waiting list for liver transplants. “I never thought in my entire career I would be able to say that,” he said.

One barrier to technology adoption can be cost. At the rates device manufacturers currently charge, perfusion of an organ outside the body can add more than $65,000 to the cost of a transplant; smaller hospitals may not be able to prepay for this procedure.

One leading company, TransMedics, raised prices significantly after regulators approved its device, prompting a damning letter from Rep. Paul Gosar, an Arizona Republican, who wrote: “What started out as a promising medical device innovation and opportunity to scale up transplants across the country, is now being held hostage by a public company that has lost its bearings.”

However, some surgeons said the technology could save money because patients who receive perfused organs tend to leave the hospital faster with fewer complications and have better mid- and long-term outcomes.

Surgeons are still exploring the upper limits of how long perfused organs can survive outside the body, and while technology is already changing transplantation significantly, some say this is just the beginning.

Dr. Shaf Keshavjee, a surgeon at the University of Toronto whose laboratory pioneered the development of technologies for preserving lungs outside the body, says these devices could eventually allow doctors to remove, repair and return them to sick patients instead of replacing lungs. “I think we can create organs that will outlive the recipient you put them in,” he said.
Dr. Ashish Shah, chairman of the department of cardiac surgery at Vanderbilt University, which has one of the busiest heart transplant programs in the country, agreed, calling it the “holy grail.”

“You have a defective heart,” he said. “I take it out. I put it in my machine. While you don't have a heart, I can keep you alive for a while with an artificial heart. Then I take your heart and fix it – cells, mitochondria, gene therapy, whatever, — and then I sew it back in. Your own heart. That's what we're striving for.”