1. Departments of Anesthesiology and Pediatrics, Columbia University, New York, New York. lss4@columbia.edu.
2. Departments of Anesthesiology and Epidemiology.
3. School of Nursing.
4. Department of Population and Family Health, School of Public Health.
5. Teachers' College and Department of Pediatrics.
6. Department of Anesthesiology, Columbia University.
7. Departments of Internal Medicine and Pharmacology, Vanderbilt University, Nashville, Tennessee; Department of Internal Medicine and Department of Pharmacology, Weil Cornell Medical College, New York, New York. ††See appendix.