Impact of PReOperative Midazolam on OuTcome of Elderly patients (I-PROMOTE): study protocol for a multicentre randomised controlled trial oleh Ana Kowark, Rolf Rossaint, András P. Keszei, Petra Bischoff, Michael Czaplik, Berthold Drexler, Peter Kienbaum, Moritz Kretzschmar, Christopher Rex, Thomas Saller, Gerhard Schneider, Martin Soehle, Mark Coburn, I-PROMOTE study group