Intraoperative Hypothermia and Blood Loss: Are Antifibrinolytic Exposure and Variations in Anesthetic Technique Possible Confounders?
Augoustides, John G. T. M.D., F.A.S.E.
To the Editor:—
I read with great interest the excellent article by Dr. Rajagopalan et al.1
detailing their meta-analysis to investigate the relation between mild perioperative hypothermia, blood loss, and transfusion. Their analysis demonstrated that mild hypothermia increases blood loss by approximately 16% and increases the risk for transfusion by approximately 22%.
My first question to the authors is whether perioperative antifibrinolytic exposure has confounded the results of the meta-analysis. For example, tranexamic acid was used in the one cardiac study that did not show increased blood loss or transfusion due to hypothermia.2
Was antifibrinolytic therapy a major confounder across studies included in the meta-analysis? Does antifibrinolytic exposure explain the studies that documented no increased bleeding or transfusion risk due to mild hypothermia?
My second question to the authors is whether these negative studies are confounded by hemostatic variations in anesthetic technique, such as induced hypotension and/or regional anesthesia.3,4
I congratulate Dr. Rajagopalan et al. on their excellent article that has further highlighted the importance of perioperative euthermia. I look forward to their comments.
John G. T. Augoustides, M.D., F.A.S.E.
Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania. firstname.lastname@example.org
1. Rajagopalan S, Mascha E, Na J, Sessler DI: The effects of mild perioperative hypothermia on blood loss and transfusion requirement. Anesthesiology 2008; 108:71–7
2. Nathan HJ, Parica L, Dupuis JY, Hendry P, Williams KA, Rubens FD, Wells GA: Safety of deliberate intraoperative and postoperative hypothermia for patients undergoing coronary artery surgery: A randomized trial. J Thorac Cardiovasc Surg 2004; 127:1270–5
3. Paul JE, Ling E, Lalonde C, Thabane L: Deliberate hypotension in orthopedic surgery reduces blood loss and transfusion requirements: A meta-analysis of randomized trials. Can J Anaesth 2007; 54:799–810
4. Richman JM, Rowlingson AJ, Maine DN, Courpas GE, Weller JE, Wu CL: Does neuraxial anesthesia reduce intraoperative blood loss? A meta-analysis. J Clin Anesth 2006; 18:427–35
© 2008 American Society of Anesthesiologists, Inc.