Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
sedation [sɪˈdeɪʃən] n
to be under sedationнаходи́ться*(impf) под возде́йствием седати́вных or успокои́тельных сре́дств
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.