Gregory Hare




Dr. Gregory Hare is a Staff Anesthesiologist at St. Michael’s Hospital and a Professor in the Department of Anesthesia at the University of Toronto. His clinical focus is to develop multimodal and inter-professional approaches to optimize patient outcomes through patient blood management strategies. His long term research goal is to define mechanisms of anemia-induced morbidity and mortality; and to design novel treatment strategies to prevent these adverse outcomes.

Dr. Hare’s research is focused on defining adaptive, and maladaptive, cardiovascular mechanisms in experimental models of acute anemia using integrative whole animal models. These translational studies have defined mechanism of anemia-induced tissue hypoxia and mortality. His laboratory has identified integrative adaptive cellular (nNOS and HIF) and physiological mechanisms which promote organism survival during acute anemia. In addition, their laboratory has demonstrated that acute beta-blockade interferes with adaptive cardiovascular mechanisms, which sustain cerebral oxygen delivery during anemia. This could possibly explain the negative interaction between acute anemia and beta-blockade and the increased incidence of stroke in perioperative patients.

The laboratory is currently focused on translational approaches to identify patient specific biomarkers of anemia-induced tissue hypoxia in order to identify when patients are at risk of anemia induced morbidity and mortality; and to derive patient specific therapies which can reduce morbidity and mortality associated with both anemia and red blood cell transfusion. The overall clinical goal is to reduce morbidity and mortality associated with acute and chronic anemia in perioperative patients.

Recent Publications

  1. Hibino, M, Peterson, MD, Tachibana, R, Chu, MWA, Bozinovski, J, Dagenais, F et al.. Association of Cerebral Oximetry with Brain Ischemic Lesions and Functional Outcomes in Arch Repair. Ann Thorac Surg. 2023; :. doi: 10.1016/j.athoracsur.2023.09.026. PubMed PMID:37777147 .
  2. Mistry, N, Jiang, H, Chin, K, Hare, GMT, Verma, S, Mazer, CD et al.. Transfusion thresholds in acute coronary syndromes. Curr Opin Cardiol. 2023; :. doi: 10.1097/HCO.0000000000001085. PubMed PMID:37610413 .
  3. Mistry, N, Hare, GMT, Shehata, N, Kramer, RS, Fawzy, HF, Baker, RA et al.. Methemoglobin as a marker of acute anemic stress in cardiac surgery. iScience. 2023;26 (8):107429. doi: 10.1016/j.isci.2023.107429. PubMed PMID:37575193 PubMed Central PMC10415918.
  4. Mistry, N, Hare, GMT, Shehata, N, Belley-Cote, E, Papa, F, Kramer, RS et al.. Transfusion Thresholds for Acute Coronary Syndromes-Insights From the TRICS-III Randomized Controlled Trial, Systematic Review, and Meta-Analysis. J Am Heart Assoc. 2023;12 (1):e028497. doi: 10.1161/JAHA.122.028497. PubMed PMID:36565203 PubMed Central PMC9973586.
  5. Chin, K, Joo, H, Jiang, H, Lin, C, Savinova, I, Joo, S et al.. Importance of assessing biomarkers and physiological parameters of anemia-induced tissue hypoxia in the perioperative period. Braz J Anesthesiol. 2023;73 (2):186-197. doi: 10.1016/j.bjane.2022.10.004. PubMed PMID:36377057 PubMed Central PMC10068554.
  6. Forté, S, Sobczyk, O, Poublanc, J, Duffin, J, Hare, GMT, Fisher, JA et al.. Sickle cell cerebrovascular reactivity to a CO2 stimulus: Too little, too slow. Front Physiol. 2022;13 :886807. doi: 10.3389/fphys.2022.886807. PubMed PMID:36060689 PubMed Central PMC9437621.
  7. Patel, PA, Wyrobek, JA, Butwick, AJ, Pivalizza, EG, Hare, GMT, Mazer, CD et al.. Update on Applications and Limitations of Perioperative Tranexamic Acid. Anesth Analg. 2022;135 (3):460-473. doi: 10.1213/ANE.0000000000006039. PubMed PMID:35977357 .
  8. Pavenski, K, Howell, A, Mazer, CD, Hare, GMT, Freedman, J. ONTraC: A 20-Year History of a Successfully Coordinated Provincewide Patient Blood Management Program: Lessons Learned and Goals Achieved. Anesth Analg. 2022;135 (3):448-458. doi: 10.1213/ANE.0000000000006065. PubMed PMID:35977355 .
  9. Pollard, BA, Meschino, C, Teja, B, Hare, GMT, Jobaneh, YS, Butler, C et al.. Continuous peripheral nerve blocks for outpatient orthopedic surgery: improving patient care and hospital efficiency through knowledge translation. Can J Anaesth. 2022;69 (6):794-796. doi: 10.1007/s12630-022-02245-w. PubMed PMID:35478084 PubMed Central PMC9045469.
  10. Chan, B, Ward, S, Abdallah, FW, Jones, C, Papachristos, A, Chin, K et al.. Opioid prescribing and utilization patterns in patients having elective hip and knee arthroplasty: association between prescription patterns and opioid consumption. Can J Anaesth. 2022;69 (8):953-962. doi: 10.1007/s12630-021-02145-5. PubMed PMID:34873641 .
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Affiliations & Other Activities


  • Staff Anesthesiologist, Department of Anesthesia, St. Michael’s Hospital
  • Professor, Department of Anesthesia, University of Toronto
  • Professor, Physiology, University of Toronto
  • Associate Member, Institute of Medical Science, University of Toronto