[1] Univ Texas Southwestern, Dept Pediat, Dallas, TX 75390 USA
[2] Vanderbilt Univ, Dept Anesthesiol Pediat Anesthesiol, Nashville, TN 37232 USA
[3] Johns Hopkins Univ, Dept Anesthesiol Crit Care Med, Baltimore, MD 21205 USA
[4] Minist Hlth & Social Welf, POB 10-9009 1000, Monrovia 10, Liberia
[5] Univ Texas Southwestern, Dept Emergency Med, Dallas, TX 75390 USA