Comparison of dexmedetomidine and fentanyl to prevent haemodynamic response to skull pin application in neurosurgery: double blind randomized controlled trial - Thongrong, Cattleya; Sirikannarat, Pannawat; Kasemsiri, Pornthep; Duangthongphon, Pichayen (Anestezjologia Intensywna Terapia, 2017)