Guardian ad litem

A guardian ad litem is a person appointed by a court to represent the interests of an incapacitated person, usually when they have no next of kin. In a medical context, the guardian ad litem has the power to grant informed consent on the patient's behalf. 
*In Love Hurts, when Harvey Park falls unconscious after refusing surgery, House attempts to have a guardian ad litem appointed for him.
*In Finding Judas, Lisa Cuddy is appointed guardian ad litem for Alice Hartman when her parents can't agree about her treatment.
Also see medical proxy