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Effect of Whole Blood Viscosity and Red Cell Mass on Canine Thromboelastographic

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Effect of Whole Blood Viscosity and Red Cell Mass on Canine Thromboelastographic Effect of whole blood viscosity and red cell mass on canine thromboelastographic tracings THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Aimee C. Brooks Graduate Program in Comparative and Veterinary Medicine The Ohio State University 2014 Master's Examination Committee: Dr. Edward Cooper, Advisor Dr. Julien Guillaumin Dr. Andrea Monnig Copyrighted by Aimee C. Brooks 2014 Abstract Abnormalities in hemostasis can result in life-threatening bleeding or thrombotic disorders. Whole blood viscoelastic methodologies including thromboelastography (TEG) have become increasingly popular in human and veterinary research and clinical medicine as a means of assessing coagulation. However, the properties of blood that influence these methodologies must be understood to accurately interpret the results, especially when in vitro findings do not match what is expected in vivo. It is well established that the hematocrit (Hct) of a sample influences the TEG tracing. While, clinically, anemia has been shown to result in an increased risk of bleeding, anemic TEG tracings typically have a hypercoagulable appearance. The opposite is also seen, as TEG tracings of samples with high Hct appear hypocoagulable. The reason for this effect of Hct on TEG tracings is unknown. However, as Hct is the main determinant of whole blood viscosity, it is possible the influence of red blood cells on the TEG is truly the effect of viscosity. In order to elucidate this difference, whole blood viscosity must be manipulated separately from Hct. We hypothesized that the effect of Hct on TEG tracings may be due to a mechanical bias of the methodology due to the effect of Hct on blood viscosity, rather than the red blood cells themselves. ii To test this hypothesis, three experiments were performed. The first used alginate (ALG) to normalize blood viscosity independent of red cell mass at varying hematocrits (45%, 20%, and 10%) and compared to control samples diluted in saline. The second experiment had a similar design, but used a different agent, carboxymethylcellulose (CMC) to modify viscosity at Hcts of 20% and 10% compared to saline-diluted controls. Finally, TEG tracings and whole blood viscosity of naturally anemic dogs were compared immediately before and after red blood cell transfusion. These three experiments demonstrate that increasing the whole blood viscosity of a sample does make TEG tracings appear less hypercoagulable than anemic saline controls, independent of Hct. However, this effect appears to be relatively small, and the Hct has additional effects shifting the TEG tracing towards decreased hypercoagulability, independent of viscosity. The influence of the agent used to alter viscosity demonstrates that ALG may have additional properties that alter coagulation that have not been previously reported. To rule out an artifact of calcium binding, we demonstrate that the effect of CMC-altered viscosity on TEG tracings is preserved even with the addition of extra calcium. Finally, increasing Hct with RBC transfusion in clinically anemic dogs correlates with mildly decreased MA and G TEG values and increased whole blood viscosity. However, these alterations towards decreased hypercoagulability are relatively small compared to the global coagulation status of the animal. Overall, this data indicates that whole blood viscosity does have a small impact on TEG tracings independent of Hct, the effect of RBC mass on TEG tracings is greater than what can be explained by the iii impact of viscosity alone, and that these changes are relatively small in dogs with clinically significant anemia requiring red blood cell transfusion. iv Acknowledgments I am tremendously grateful for the support and guidance provided by my committee members Drs. Edward Cooper, Julien Guillaumin, and Andrea Monnig for their help and guidance throughout my residency in this project and in my growth towards becoming a critical care specialist. I cannot express enough how much their help and insight have impacted me as a doctor and a human being, and am so indebted to them for their time and effort in my training. I would also like to express deep gratitude to Dr. Guillermo Couto and the staff of the OSU blood bank, Dr. Cristina Iazbik and Technicians Dawn Hudson and Amanda Simons for assistance with project development, equipment training, sample acquisition, and technical support. Completion of the clinical transfusion phase of this project would not have been possible without the help of the OSU small animal intern classes of 2013 and 2014 and the incredible technicians of the OSU ICU and ER services, and I thank them for their support of this project and excellent phlebotomy skills. Finally, I would like to thank my husband David Taggart, and my family, friends, and resident mates Steve Friedenberg, Kristen Datte, and Christine Culler for all of their support throughout this residency program. v Vita May 2000 .......................................................Luke M. Powers Catholic High School 2004................................................................B.S. Zoology, Michigan State University 2008................................................................DVM, Michigan State University 2011-2014 .....................................................Graduate Research Associate, The Ohio State University Publications 1. Brooks AC, Guillaumin J, Cooper ES, Couto CG. Effects of hematocrit and red blood cell-independent viscosity on canine thromboelastographic tracings. Transfusion 2013, Article published online Jul 31 2. Friedenberg SG, Brooks AC, Monnig AA, Cooper ES. Successful treatment of a dog with massive 5-fluorouracil toxicosis. Journal of Veterinary Emergency and Critical Care 2013, 23(6), 643–647 3. Brooks AC, Hardie R. Use of the PleuralPort device for management of pleural effusion in six dogs and four cats. Vet Surg 2011, 40(8), 935-941 4. Crystallization of the Oct-1/SNAP190 peptide/DNA complex. Hovde S, Brooks A, Strong K, Geiger JH. Acta Crystallogr D Biol Crystallogr 2002, 58(Pt 3), 511- vi 5. Activator recruitment by the general transcriptional machinery: X-ray structural analysis of the Oct-1 POU domain/human U1 octamer/SNAP190 peptide ternary complex. Hovde S, Hinkley CS, Strong K, Brooks A, Gu L, Henry RW, Geiger J. Genes and Development 2002, 16(21), 2772-7 Fields of Study Major Field: Comparative and Veterinary Medicine vii Table of Contents Abstract ............................................................................................................................... ii Acknowledgments............................................................................................................... v Vita ..................................................................................................................................... vi Table of Contents ............................................................................................................. viii List of Tables ...................................................................................................................... x List of Figures .................................................................................................................... xi Chapter 1: INTRODUCTION............................................................................................ 1 1.1 The cell based model of coagulation ............................................................................ 1 1.2 Thromboelastography (TEG) ........................................................................................ 9 1.3 Whole blood viscosity measurement .......................................................................... 29 1.4 Study rationale ............................................................................................................ 31 1.5 References ................................................................................................................... 33 Chapter 2: ALGINATE..................................................................................................... 55 2.1 Introduction ................................................................................................................. 55 2.2 Materials and Methods ................................................................................................ 57 2.3 Results ......................................................................................................................... 61 viii 2.4 Conclusions ................................................................................................................. 63 2.5 References ................................................................................................................... 67 CHAPTER 3: CARBOXYMETHYLCELLULOSE ........................................................ 77 3.1 Introduction ................................................................................................................. 77 3.2 Materials and Methods. ............................................................................................... 79 3.3 Results. ........................................................................................................................ 82 3.4 Discussion ................................................................................................................... 84 3.5 References ..................................................................................................................
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