(Wang) Associate Professor of Anesthesia.(Quan) Research Assistant.(Vladimirov, Mok) Instructor in Anesthesia.(Thalhammer) Assistant Professor of Anesthesia.Received from the Department of Anesthesia Research Laboratories, Harvard Medical School and Brigham and Women's Hospital, Boston, Massachusetts. Submitted for publication March 24, 1995. Accepted for publication August 29, 1995. Supported by National Institutes of Health grants GM35401 and GM48090 to Dr. Wang.Address reprint requests to Dr. Wang: Department of Anesthesia, Brigham and Women's Hospital, 75 Francis Street, Boston, Massachusetts 02115.