anxiety
"I was given Ativan before having an MRI done. I have extreme claustrophobia and was unable to get the MRI done even the open MRI type machine. I took 2mg. one hour before the test. Right up until the test I was terrified. However, within five minutes, being in the MRI machine, I was out! I mean out, in a different world. It was scarey. I had an IV placed and didn't feel a thing. The whole test (an hour or longer) went perfectly. 
Here is the really scarey part. I came home and went about my usual business. At supper, read the paper, even drove in town. The next day I had absolutely no memory of the previous day. The Ativan caused severe amnesia."