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. Hong, A, Varshney, V, Hare, GM, Mazer, CD. CMAJ. 2021;193 (1):E30-E33. doi: 10.1503/cmaj.200229-f. PubMed PMID:33397640 PubMed Central PMC7774481.
  2. Alli, A, Hare, GMT. Kanga cloths to smartphones: how should we measure blood loss in the operating room?. Can J Anaesth. 2021;68 (2):175-179. doi: 10.1007/s12630-020-01858-3. PubMed PMID:33205266 .
  3. Chin, K, Cazorla-Bak, MP, Liu, E, Nghiem, L, Zhang, Y, Yu, J et al.. Renal microvascular oxygen tension during hyperoxia and acute hemodilution assessed by phosphorescence quenching and excitation with blue and red light. Can J Anaesth. 2021;68 (2):214-225. doi: 10.1007/s12630-020-01848-5. PubMed PMID:33174162 .
  4. Hong, A, Varshney, V, Hare, GMT, Mazer, CD. Spinal cord stimulation: a nonopioid alternative for chronic pain management. CMAJ. 2020;192 (42):E1264-E1267. doi: 10.1503/cmaj.200229. PubMed PMID:33077521 PubMed Central PMC7588206.
  5. Hare, GMT, Cazorla-Bak, MP, Ku, SFM, Chin, K, Mistry, N, Sklar, MC et al.. When to transfuse your acute care patient? A narrative review of the risk of anemia and red blood cell transfusion based on clinical trial outcomes. Can J Anaesth. 2020;67 (11):1576-1594. doi: 10.1007/s12630-020-01763-9. PubMed PMID:32770311 .
  6. Rigamonti, A, Ma, K, Garavaglia, MM, Hare, GMT, Mazer, CD. In reply: Bilateral scalp blocks help reduce postoperative pain and opioid requirement, but the impact cannot be so huge. Can J Anaesth. 2020;67 (9):1296-1297. doi: 10.1007/s12630-020-01712-6. PubMed PMID:32436151 .
  7. Abrahamson, JR, Read, A, Chin, K, Mistry, N, Joo, H, Desjardins, JF et al.. Renal tissue Po2 sensing during acute hemodilution is dependent on the diluent. Am J Physiol Regul Integr Comp Physiol. 2020;318 (4):R799-R812. doi: 10.1152/ajpregu.00323.2019. PubMed PMID:32130021 .
  8. Baron Shahaf, D, Hare, GMT, Shahaf, G. The Effects of Anesthetics on the Cortex-Lessons From Event-Related Potentials. Front Syst Neurosci. 2020;14 :2. doi: 10.3389/fnsys.2020.00002. PubMed PMID:32116577 PubMed Central PMC7026482.
  9. Rigamonti, A, Garavaglia, MM, Ma, K, Crescini, C, Mistry, N, Thorpe, K et al.. Effect of bilateral scalp nerve blocks on postoperative pain and discharge times in patients undergoing supratentorial craniotomy and general anesthesia: a randomized-controlled trial. Can J Anaesth. 2020;67 (4):452-461. doi: 10.1007/s12630-019-01558-7. PubMed PMID:31879855 .
  10. Duffin, J, Hare, GMT, Fisher, JA. A mathematical model of cerebral blood flow control in anaemia and hypoxia. J Physiol. 2020;598 (4):717-730. doi: 10.1113/JP279237. PubMed PMID:31823369 .
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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