[1] Johns Hopkins Med Inst, Dept Anesthesiol & Crit Care Med, Baltimore, MD 21205 USA
[2] Johns Hopkins Med Inst, Dept Surg, Baltimore, MD 21205 USA
[3] Johns Hopkins Med Inst, Dept Orthoped Surg, Baltimore, MD 21205 USA
[4] Johns Hopkins Med Inst, Dept Surg Nursing Adm, Baltimore, MD 21205 USA
[5] Johns Hopkins Med Inst, Dept Neurosurg, Baltimore, MD 21205 USA
[6] Int Joint Commiss, Ctr Patient Safety, Joint Commiss Accreditat Healthcare Org, Oak Brook Terrace, IL USA