Commentary: Come in from the cold.

Central MessageTransfusion following aortic surgery using hypothermia is associated with negative outcomes. Adjuncts to avoid transfusion should include rewarming the patient.See Article page 544. Transfusion following aortic surgery using hypothermia is associated with negative outcomes. Adjuncts to avoid transfusion should include rewarming the patient. See Article page 544. Perioperative bleeding is a recognized complication of cardiac procedures, with increased risks associated with cases performed on cardiopulmonary bypass and those requiring hypothermia. This complication is further compounded by evidence demonstrating that blood transfusions negatively impact both short- and long-term morbidity and mortality.1LaPar D.J. Hawkins R.B. McMurry T.L. Isbell J.M. Rich J.B. Speir A.M. et al.Preoperative anemia versus blood transfusion: which is the culprit for worse outcomes in cardiac surgery?.J Thorac Cardiovasc Surg. 2018; 156: 66-74.e2Abstract Full Text Full Text PDF PubMed Scopus (71) Google Scholar, 2Koch C.G. Li L. Duncan A.I. Mihaljevic T. Loop F.D. Starr N.J. et al.Transfusion in coronary artery bypass grafting is associated with reduced long-term survival.Ann Thorac Surg. 2006; 81: 1650-1657Abstract Full Text Full Text PDF PubMed Scopus (423) Google Scholar, 3Velasquez C.A. Singh M. Bin Mahmoud S.U. Brownstein A.J. Zafar M.A. Saeyeldin A. et al.The effect of blood transfusion on outcomes in aortic surgery.Int J Angiol. 2017; 26: 135-145Crossref PubMed Scopus (18) Google Scholar, 4Engoren M.C. Habib R.H. Zacharias A. Schwann T.A. Riordan C.J. Durham S.J. Effect of blood transfusion on long-term survival after cardiac operation.Ann Thorac Surg. 2002; 74: 1180-1186Abstract Full Text Full Text PDF PubMed Scopus (539) Google Scholar Sultan and colleagues5Sultan I. Bianco V. Aranda-Michel E. Kilic A. Serna-Gallegos D. Navid F. et al.The use of blood and blood products in aortic surgery is associated with adverse outcomes.J Thorac Cardiovasc Surg. 2023; 165: 544-551.e3Abstract Full Text Full Text PDF Scopus (5) Google Scholar have reported their institution's experience with blood product use in aortic surgery and resultant postoperative outcomes. Although this study is not the first to evaluate this issue, it is one of the largest to date, with the authors assessing 824 patients undergoing aortic surgery requiring circulatory arrest and comparing propensity-matched cohorts separated based on the need for transfusion. Ultimately, the authors found that longer procedure times and greater surgical complexity corresponded with increased blood component transfusions, with greater mortality rates demonstrated in those receiving transfusions. Although it is generally accepted that aortic procedures associated with deep hypothermic circulatory arrest (DHCA) often use more blood products, Sultan and colleagues suggest that DHCA coupled with blood component transfusion results in significantly worse outcomes. The hemostatic system functions optimally at normothermia (ie, ∼37°C), with alterations in the function of pro- and anticoagulant proteins, pro- and antifibrinolytics proteins, and platelets at progressively lower temperatures.6Rohrer M.J. Natale A.M. Effect of hypothermia on the coagulation cascade.Crit Care Med. 1992; 20: 1402-1405Crossref PubMed Scopus (582) Google Scholar, 7Whelihan M.F. Kiankhooy A. Brummel-Ziedins K.E. Thrombin generation and fibrin clot formation under hypothermic conditions: an in vitro evaluation of tissue factor initiated whole blood coagulation.J Crit Care. 2014; 29: 24-30Crossref PubMed Scopus (15) Google Scholar, 8Wallner B. Schenk B. Hermann M. Paal P. Falk M. Strapazzon G. et al.Hypothermia-associated coagulopathy: a comparison of viscoelastic monitoring, platelet function and real time live confocal microscopy at low blood temperatures, an in-vitro experimental study.Front Physiol. 2020; 11: 843Crossref PubMed Scopus (15) Google Scholar Accordingly, the temperature associated with DHCA is frequently among the usual suspects blamed for coagulopathy and the resultant postoperative bleeding. However, hypothermia-associated coagulopathy is not irreversible, and the best goal-directed therapy aimed at correcting this coagulopathy begins with rewarming the patient to a normal core temperature rather than the transfusion of blood components.9Reed II, R.L. Johnson T.D. Hudson J.D. Fischer R.P. The disparity between hypothermic coagulopathy and clotting studies.J Trauma. 1992; 33: 465-470Crossref PubMed Scopus (191) Google Scholar,10Michelson A.D. MacGregor H. Barnard M.R. Kestin A.S. Rohrer M.J. Valeri C.R. Reversible inhibition of human platelet activation by hypothermia in vivo and in vitro.Thromb Haemost. 1994; 71: 633-640Crossref PubMed Scopus (343) Google Scholar No universally accepted temperature to separate from cardiopulmonary bypass exists, with authors of a recent guideline cautioning against hyperthermia and acknowledging that they could not make temperature recommendations for separation due to a paucity of published evidence.11Engelman R. Bailer R.A. Likosky D.S. Grigore A. Dickinson T.A. Shore-Lesserson L. et al.The Society of Thoracic Surgeons, the Society of Cardiovascular Anesthesiologists, and the American Society of Extracorporeal Technology: clinical practice guidelines for cardiopulmonary bypass—temperature management during cardiopulmonary bypass.Ann Thorac Surg. 2015; 100: 748-757Abstract Full Text Full Text PDF PubMed Scopus (71) Google Scholar Moreover, in a previous study, one of us (A.D.) considered that the nadir temperature achieved during DHCA is not what influences bleeding; rather, bleeding was associated with the proximity to normal body temperature reached at the time the patient left the operating room.12Stein L.H. Rubinfeld G. Balsam L.B. Ursomanno P. DeAnda Jr., A. Too cold to clot? Does intraoperative hypothermia contribute to bleeding after aortic surgery?.Aorta (Stamford). 2017; 5: 106-116Crossref PubMed Google Scholar While patient blood-management programs can work in association with even complex aortic surgeries,13Smith D. Grossi E.A. Balsam L.B. Ursomanno P. Rabinovich A. Galloway A.C. et al.The impact of a blood conservation program in complex aortic surgery.Aorta (Stamford). 2013; 1: 219-226Crossref PubMed Scopus (15) Google Scholar these initiatives' success should not rely solely on altering transfusion thresholds or addressing preoperative anemia; instead, they should also include aggressive measures to mitigate bleeding in the first place. Although this often entails an additional suture or the use of a prothrombotic mechanical or flowable adjunct intraoperatively, consideration should also be given to a device readily available in every cardiac operating room and is uniquely capable of rewarming the patient, as opposed to a cooling blanket or raising the ambient temperature—the cardiopulmonary bypass machine. Sultan and colleagues have reminded us that transfusion is a double-edge sword, and avoidance of the need for blood and blood products includes optimizing hemostasis. Warming the patient to normothermia should be part of the algorithm. The use of blood and blood products in aortic surgery is associated with adverse outcomesThe Journal of Thoracic and Cardiovascular SurgeryVol. 165Issue 2PreviewTo report long-term outcomes after deep hypothermic circulatory arrest (DHCA) with or without perioperative blood or blood products. Full-Text PDF