"Organ donation in Jewish law is one classic example of the obligation to violate a commandment because of pikuach nefesh." (source)

"For example, a sick person or a pregnant woman is obligated to eat on Yom Kippur when others fast because of pikuach nefesh. An Orthodox Jew might drive his car on Shabbat if he needs to get his sick child to the hospital." (JPS)

"Get this man to the hospital right away—it's pikuach nefesh!" (Glinert)