The AP has a fairly dramatic story of an American heart surgeon who was operating on a charity mission at Benjamin Bloom Children's Hospital in San Salvador:
A heart surgeon had to take a break from a mercy-mission operation in El Salvador so he could donate his own rare-type blood for his 8-year-old patient.
Dr. Samuel Weinstein said he had his blood drawn, ate a Pop-Tart, returned to the operating table and watched as his blood helped the boy survive the complex surgery....
The 43-year-old Weinstein was on a charity trip with Heart Care International when he did the surgery at Bloom Hospital in San Salvador.
In the May 11 operation, which had begun 12 hours earlier, the boy's failing aortic valve was replaced with his pulmonary valve and the pulmonary valve was replaced with an artificial valve.
"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.
They were running out of blood to give the boy, Weinstein said. When he asked the boy's blood type, he discovered they were both B-negative.
Weinstein, who said he was an occasional blood donor - "but never like this" - said the interruption to donate a pint lasted about 20 minutes. more.