Transfusion guidelines in adult spine surgery: a systematic review and critical summary of currently available evidence. - Barrie U; Youssef CA; Pernik MN; Adeyemo E; Elguindy M; Johnson ZD; Ahmadieh TYE; Akbik OS; Bagley CA; Aoun SG (The spine journal : official journal of the North American Spine Society, 2022)