[1] Mem Hermann Hlth Syst, 6411 Fannin St,Robertson 585-3, Houston, TX 77030 USA
[2] Univ Texas Hlth Sci Ctr Houston, Dept Internal Med, McGovern Med Sch, Houston, TX USA
[3] Univ Texas Hlth Sci Ctr Houston, Dept Anesthesiol, McGovern Med Sch, Houston, TX USA