I Want to Drink Your Blood

 refers to an unmarked and repeatable quest in Fallout 3.

After finishing Blood Ties, Vance will happily pay you for Blood Packs (15 caps each), although you mention "donating" in your conversation. No Karma bonus is granted. Also if you go back to Vance after the Blood Ties quest, he can teach you the Hematophagy perk, which will make Blood Packs heal 20 HPs instead of 1 HP.