[1] Johns Hopkins Univ, Sch Med, Baltimore, MD 21287 USA
[2] Berman Inst Bioeth, Baltimore, MD USA
[3] Duke Univ, Med Ctr, Dept Pediat, Durham, NC 27710 USA
[4] Montefiore Univ Hosp, Dept Palliat Care, Pittsburgh, PA USA
[5] Johns Hopkins Bloomberg Sch Publ Hlth, Dept Populat Family & Reprod Hlth, Baltimore, MD USA