This article from 'Anesthesia and Analgesia' has a lot of useful information about the value of librarians, including references to studies about clinical ones. It also includes an interesting discussion on people’s search behaviour and use of resources.
Difficulties and challenges associated with literature searches in operating room management, complete with recommendations
Wachtel RE1, Dexter F.
Anesth Analg. 2013 Dec;117(6):1460-79. doi: 10.1213/ANE.0b013e3182a6d33b.