1. Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, Maryland, USA.
2. R Adams Cowley Shock Trauma Center, University of Maryland School of Medicine, Baltimore, Maryland, USA.
3. Department of Epidemiology and Public Health, University of Maryland School of Medicine, Baltimore, Maryland, USA.
4. Maryland Institute for EMS Systems, Baltimore, Maryland, USA.
5. Northeast Ohio Medical University, Rootstown, Ohio, USA.