Dr. Samuel Weinstein is the chief of pediatric cardio-thoracic surgery for the Children's Hospital at Montefiore Medical Center in the Bronx, New York. In May of 2006, he traveled to El Salvador with Heart Care International in order to provide life-saving operations for less-fortunate children. However, it would take more than his expertise and advanced equipment to save the life of 8-year-old Francisco Calderon Anthony Fernandez.

Dr. Weinstein and his team began operating on Francisco's heart shortly before noon. Twelve hours later, the procedure took a deadly turn. "The surgery had been going well, everything was working great, but he was bleeding a lot and they didn't have a lot of the medicines we would use to stop the bleeding," Weinstein said. "After a while, they said they couldn't give him blood because they were running out and he had a rare type.'' In fact, Francisco's blood type was B-negative, which—according to the American Red Cross—is present in only 2 percent of the population.

As it was, the only other person in the room with a blood type of B-negative was Dr. Weinstein. Knowing what he had to do, he stepped down from the operating table. As his colleagues continued their precision work, Dr. Weinstein set aside his scalpel, took off his gloves, and began washing his hands and forearm. Then, in the corner of an unfamiliar operating room, the prestigious doctor from one of the most advanced hospitals in the world sat down to give away his own blood.

When he had given his pint, Dr. Weinstein drank some bottled water and ate a Pop-Tart. Then—20 minutes after stepping away from the table—he rejoined his colleagues. After watching his own blood begin circulating into the boy's small veins, Dr. Weinstein completed the operation that saved Francisco's heart—and his life.