New guidelines are supposed to protect organ donors in a retrieval procedure that keeps blood flowing through livers, kidneys, lungs and hearts. But bioethicists have troubling questions. Olga Pankova/Getty Images hide caption

Olga Pankova/Getty Images

The U.S. organ transplant system has approved the first national policy for a controversial procedure used to remove organs from hospital patients. The guidelines are designed to protect potential donors. But critics say they do little to improve safety and fail to address deeply troubling ethical concerns.

The procedure is called normothermic regional perfusion, known as NRP . It can be used after a family has decided to withdraw care because there's no hope of meaningful recovery for the person. To perform NRP, doctors attach an external pump to a donor minutes after their circulation has ended and they've been declared dead.…