Can a patient designate his doctor as his proxy decision maker?

Most lawyers and bioethicists recommend that patients enact a durable power of attorney for health care designating somebody as their proxy decision maker should they become unable to make decisions. Most people choose family members as their agent. But what if a patient wants his or her doctor to be his or her proxy decision maker? Can the doctor be both physician and surrogate decision maker? Or should those roles necessarily be kept separate? We present a case in which those issues arose, and sought comments from Sabrina Derrington, a pediatric palliative care physician; Arthur Derse, an emergency department physician and lawyer; and Phil Black, a pulmonologist.