For decades, donated organs have been submerged in a cold solution simply called "UW liquid" — because it was developed at the University of Wisconsin — while en route to a recipient. It's been the gold standard for organ transportation for years.

Now, a new method of preserving organs is being studied, and an organ recipient recently became the first in the country to receive a liver preserved at body temperature instead of cold storage. Coincidentally, the procedure was conducted at the UW Hospital in Madison.

The transplant was part of a study that compares the two methods of organ preservation. Across the country, 14 other transplant centers are participating the study, and the results will be published in the coming months.

The alternative to cold storage is called warm perfusion, using a machine developed by OrganOx, based in Oxford, England.. Organs are pumped with blood and nutrients at or just below body temperature. The process actually keeps organs working while in transit to a recipient.

"The ability to potentially optimize the condition of donated organs through normothermic preservation may not only increase the number of organs available for transplant but may also allow transplant professionals to identify and exclude nonviable organs before subjecting patients to the risk of surgery," Dr. Tony D’Alessandro, a UW transplant surgeon and principal investigator of the study, said in a statement.

Another study in 2014 also looked at warm perfusion, which was developed by Massachusetts General Hospital (MGH) Center for Engineering in Medicine. It was a laboratory study, not a clinical trial.

"By the time a donated organ is transplanted, it has sustained significant injury through lack of a blood supply," said Bote Bruinsma, MSc, of the MGH-CEM and Department of Surgery, lead author of the 2014 report.

"By supporting metabolic function, we can give the liver time to recover, preconditioning it before transplantation. The hope is that, in the near future, livers that currently are considered unsuitable for transplantation will be recovered by more advanced preservation techniques, significantly increasing the number of organs available for transplantation."

Indeed, warm perfusion does seem to have clear advantages to cold solution. The mean bile production using perfusion over 24 hours is closer to normal bile production than that of livers kept in cold storage. ALT and AST levels were also closer to levels expected in normally functioning livers than those in cold storage.

Using perfusion, the liver can be kept alive much longer than those using cold storage, which only allow livers to stay viable for 10-12 hours outside the body. Perfusion allows livers to remain viable for three days.

"Demonstrating the feasibility of this approach in human livers is an enormous step forward in bringing this technology to clinical application," Bruinsma explains. "We expect that perfusion systems will revolutionize the way the liver is preserved outside the body, significantly increasing the number of livers available for transplants and saving the lives of potentially thousands of patients."