Department of Anesthesi-ology and Perioperative Medicine,UMass Memorial Healthcare;
Department of Anesthesiology,Hospital for Special Surgery,Weill Cornell Medical Center;
Department of Anesthesiology,PerioperativeMedicine and Intensive Care Medicine,Paracelsus Medical University;
Department of Orthopedic Surgery,Hospital for Special Surgery,Weill Cornell Medical Center;
Department of Quantitative Health Sciences,University of Massachusetts Medical School;
Transfusion; Complex; spine; surgery; Near; infrared; spectroscopy; Microvascular; blood; flow; Hemodynamic; monitoring;