A federal judge intervened Thursday to improve the odds that a second dying child could get a lung transplant from an adult donor in a fast-moving drama that has tugged at the public's heartstrings while raising concerns among ethicists.

Just a day earlier, lawyers had persuaded U.S. District Judge Michael M. Baylson to suspend rules they said discriminated against children like Sarah Murnaghan of Newtown Square, a 10-year-old with end-stage cystic fibrosis. They returned to federal court Thursday and successfully argued for Javier Acosta, 11, of New York City, who suffers from the same progressive disease. He has been waiting for lungs since 2010, the lawsuit said.

Both patients are at Children's Hospital of Philadelphia.

Baylson issued a temporary restraining order that prevents the U.S. Department of Health and Human Services from enforcing its so-called under-12 rule for Sarah and Javier.

That rule says children on the waiting list cannot be considered for adult lungs until the organs have been offered to all wait-listed adults in the region, including adults in less dire need.

The judge's order does not guarantee either child a transplant, or placement at the top of the adult waiting list. It requires that in addition to being on the pediatric wait list, Sarah and Javier be added to the adult list and ranked, like adults, based on the severity of their medical needs.

Sarah's case, publicized by her family through a media campaign and online petitions, has prompted an official review of the rules. The Organ Procurement and Transplantation Network, which sets transplant allocation policy, announced that it will meet Monday to analyze data on waiting time, organ offers, organ transplants, and wait list mortality.

John Roberts, president of the network board, said it "would be able to approve an interim policy change" if warranted by the facts.

While experts applaud that review, they question the judicial intervention. They worry that ordering special treatment could undermine the complex national organ allocation system, which balances desperate need with a shortage of donated organs.

"We believe it would be unwise to change current policy without the deliberative approach mandated" by law, the American Society of Transplant Surgeons said in a statement.

Scott D. Halpern, a University of Pennsylvania critical care physician who studies the ethics of transplant policies, said he fears Baylson's ruling sets a precedent "where judges are getting involved in the allocation of scarce resources."

"An activist judicial system that promotes the interests of one person without time to carefully consider the consequences is highly likely to circumvent the justice it's trying to enforce," Halpern said.

A system that fairly rations organs is "not discrimination," he said. "It considers the interests of all patients, not just those who have the resources to draw the most attention to themselves through the media."

If strong parents can influence the system, "then you have chaos," echoed George Mallory, a pulmonologist who is medical director of the lung transplant program at Texas Children's Hospital. "I think there has been a scrupulous desire to make the system as fair as possible."

Studies show current lung allocation rules, revised in 2004, have reduced waiting-list deaths for both children and adults.

The judge's ruling applies only to Sarah, who is in intensive care, and Javier, who is not. The latest lawsuit, filed by Javier's mother, Milagros Martinez of the Bronx, N.Y., said the boy's older brother, Jovan, died of cystic fibrosis two years ago in New York while awaiting a lung and liver transplant at age 11.

"If Milagros Martinez is to lose another son, it should not be because of the Under 12 rule," said the suit, filed by lawyers from Pepper Hamilton.

If either child receives an adult lung, it would have to be cut down to fit - a more complex procedure than a standard transplant.

Currently, there are five children ages 6 to 10 and two ages 11 to 17 awaiting donor lungs nationwide, according to the United Network for Organ Sharing. That presumably includes Javier and Sarah, who went on the wait list 18 months ago and has been hospitalized since February.

UNOS records show that children's lungs sometimes go to adults. From 2008 through February 2012, 69 lungs from children were transplanted into older recipients. In the same period, only one lung from a 12- to 17-year-old was transplanted to a younger child, and no children under 12 received adult lungs.

Transplanting adult lungs into children is rare in the United States. Nine such transplants were performed between 1992 and 2006, and none since then.

Stephen Harvey, a lawyer for the two families, said Children's Hospital surgeons have performed adult-to-child transplants before, but UNOS records show only one such procedure at the hospital, in 1997. Children's officials have declined to answer even general questions about transplants.

Position on the waiting lists is based on a formula that assesses risk of death and likelihood of transplant success, but children under 12 are categorized as either Priority 1 or 2, while adults get a Lung Allocation Score.

Four Priority 1 children are awaiting transplants in the region - eastern Pennsylvania, South Jersey, and Delaware - as are six adults with scores above 50, the sickest adult category, records show.

Rick Hasz, vice president of clinical services of the regional Gift of Life Donor Program, said there is no way to know exactly where Sarah and Javier rank because an updated list is generated each time a donor lung becomes available.

Hasz said the best solution is for more people to become donors: "It's really about families saying yes to donation at the time of death."

Contact Marie McCullough at 215-854-2720 or mmccullough@phillynews.com.