Microactuated Rheometer for Point of Care Coagulopathy Applications

Univ Of North Carolina Chapel Hill, Chapel Hill NC

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Abstract

DESCRIPTION (provided by applicant): We propose development of a new technology that addresses the need for quantitative and sensitive point of care (POC) viscoelastic hemostatic assay (VHA) capability to characterize coagulation parameters that are crucial to guiding therapies for traumatic hemorrhage. Our proposed technique employs an array of magnetically actuated microscopic surface attached posts (SAPs), whose dynamic mechanical response to fluid conditions provides a quantitative measure of rheological parameters. The SAPs resemble biological cilia in size and aspect ratio and can be beat at large amplitudes in the Hz to 10s of Hz frequency range. The SAPs are arranged in an array on the device's active surface; they are actuated with an external magnetic field and their amplitude is monitored optically. The temporal progression of the clotting process, from clotting time to clot lysis, can be monitored. In recent years increasing evidence has pointed to trauma induced coagulopathy (TIC) as a major factor in complications leading to hemorrhage related death; 25-35% of trauma cases involve TIC. Mechanisms of TIC are still an active area of research, but it is clear that trauma can compromise healthy coagulation both by inhibiting clotting and amplifying lysis. Diagnostic tests that can rapidly evaluate hemostasis-related parameters from clotting to lysis are critical in developing effective therapeutic strategies for TIC. It is also crucial that these diagnostics are available where the need is greatest: near the accident prior to and during movement of the patient. Traditional laboratory coagulation tests such as prothrombin time (PT) and activated partial thromboplastin time (APTT) are both impractical and ineffective at providing these diagnostics. These plasma-based tests assess only the very beginning of the coagulation process (no information on lysis), require blood processing, and provide no mechanical information (clot strength). Within the context of this project, we will validate the ability the SP based viscoelastic measurements to provide information relevant to medical decisions. We will focus on developing a new approach to the underserved TIC problem in the field and during transportation of patients. We have successfully developed a fabrication protocol for SAPs, demonstrated their actuation in fluids, and have preliminary data demonstrating their ability to measure clot properties during coagulation. In the first year of this project we will characterize our system using reference viscous and viscoelastic fluids. In the second year we will demonstrate reproducible blood clotting measurements using the SAP system and validation by correlating these measurements with standard clinical and laboratory tests (using laboratory-based TEG instruments). Measurements on normal and factor deficient canine plasmas and whole blood will be performed including clotting time, clot stiffness, and clot lysis time.