TRANSFUSION MEDICINE AND IMMUNOHEMATOLOGY: Edited by Karina YazdanbakhshHyperviscosity syndromes; hemorheology for physicians and the use of microfluidic devicesMusick, Jamie O.a; Fibben, Kirby S.b; Lam, Wilbur A.a,b Author Information aDepartment of Pediatrics, Aflac Cancer and Blood Disorders Center of Children's Healthcare of Atlanta, Emory University School of Medicine bWallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia, USA Correspondence to Wilbur A. Lam, MD, PhD, Emory Children's Center, 2015 Uppergate Drive, Atlanta, GA 30322, USA . Tel: +1 404 727 7473; e-mail: [email protected] Current Opinion in Hematology 29(6):p 290-296, November 2022. | DOI: 10.1097/MOH.0000000000000735 Buy Metrics Abstract Purpose of review Hyperviscosity syndromes can lead to significant morbidity and mortality. Existing methods to measure microcirculatory rheology are not readily available and limited in relevance and accuracy at this level. In this review, we review selected hyperviscosity syndromes and the advancement of their knowledge using microfluidic platforms. Recent findings Viscosity changes drastically at the microvascular level as the physical properties of the cells themselves become the major determinants of resistance to blood flow. Current, outdated viscosity measurements only quantify whole blood or serum. Changes in blood composition, cell number, or the physical properties themselves lead to increased blood viscosity. Given the significant morbidity and mortality from hyperviscosity syndromes, new biophysical tools are needed and being developed to study microvascular biophysical and hemodynamic conditions at this microvascular level to help predict those at risk and guide therapeutic treatment. Summary The use of ‘lab-on-a-chip’ technology continues to rise to relevance with point of care, personalized testing and medicine as customizable microfluidic platforms enable independent control of many in vivo factors and are a powerful tool to study microcirculatory hemorheology. Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.