GREY'S ANATOMY - "Bad Blood" - As Derek and April work around the clock to find a solution for the hospital, Cristina struggles to respect the wishes of a family whose son is dying. Meanwhile, Arizona empathizes with a teenager who faces problems similar to her own, on "Grey's Anatomy," THURSDAY, JANUARY 31 (9:00-10:02 p.m., ET) on the ABC Television Network. (ABC/KELSEY MCNEAL) KEVIN MCKIDD, CONSTANCE ZIMMER