1. Harborview Anesthesiology Research Center, University of Washington, Seattle, Washington.
2. Department of Anesthesiology, University of Washington, Seattle, Washington.
3. Department of Anesthesiology and Critical Care, University of Pennsylvania, Philadelphia, Pennsylvania.
4. Department of Pediatrics, University of Washington, Seattle, Washington.
5. Department of Neurological Surgery, University of Washington, Seattle, Washington.
6. Harborview Injury Prevention and Research Center, Seattle, Washington.