(Van, Horrow) Professor and Vice Chair, Anesthesiology.(Riper, Parmet) Assistant Professor, Anesthesiology.(Strong) Associate Professor, Cardiothoracic Surgery.(Grunewald) Instructor, Cardiothoracic Surgery.Received from the Departments of Anesthesiology and Cardiothoracic Surgery. The Medical College of Pennsylvania and Hahnemann University, Philadelphia, Pennsylvania. Submitted for publication December 20, 1993. Accepted for publication October 21, 1994. Supported by a grant from The Mary L. Smith Charitable Lead Trust.Address correspondence and reprint requests to Dr. Horrow: Department of Anesthesiology. Mail Stop 310, Broad and Vine streets, Philadelphia, Pennsylvania 19102–1192.