1. From the Departments of Anesthesiology/Critical Care Medicine (I.H., A.B., A.B.S., A.C.D., P.D.H., R.J.T., J.R.K.) and Neurology (A.B., J.R.K.), Johns Hopkins University School of Medicine, Baltimore, Md, and National Institute on Drug Abuse (E.D.L.), Baltimore, Md.