C. K. Rozean1, M. J. George1, K. R. Aroom1, M. A. Skibber1, T. Sharma1, C. E. Wade1, C. S. Cox1, B. S. Gill1 1University Of Texas Health Science Center At Houston,Houston, TX, USA
Introduction: Thromboelastography (TEG) demonstrates clinical utility in multiple surgical fields including general, trauma, hepatic and cardiac surgery. Current TEG devices are limited to use within clinical laboratory settings due, in part, to size constraints. We describe a novel linear thromboelastometry device (LTD) driven by a microelectromechanical system (MEMS) with the potential for scaling to portability. We hypothesize that this device will demonstrate similar coefficients of variation to TEG when tested in normal human control subjects, and will demonstrate the effects of hemodilution on clot formation metrics with greater sensitivity than TEG.
Methods: Venous blood was collected from healthy adult volunteers into citrate tubes. Recalcified blood is injected into a well mounted on a MEMS driven translational stage. A flexible paddle probe fixed as a cantilever beam is lowered into the blood sample. As the blood clots, and a platelet/fibrin mesh forms, translation of the stage causes an increasing force to act on the unfixed end of the paddle probe. This force is measured optically as deflection of the probe. Clot formation metrics were defined as follows: maximum amplitude of paddle probe deflection (MA), time to first evidence of probe deflection (clot formation, or R), time to reach an established amplitude value (K), and angle formed by the horizontal and a line plotted from R to K on a graph of deflection over time (Angle). To test single person variability of the device, blood from a single individual was tested in triplicate for 3 consecutive days. To test population variability of the device, blood from four individuals was tested in duplicate. To test the sensitivity of the device, blood samples were diluted with phosphate buffered saline (PBS). 6 solutions ranging from 95% PBS with 5% blood to 100% citrated recalcified blood were prepared. TEG was performed on separate aliquots of all samples analyzed in the LTD.
Results:Coefficient of variation (CV) is smaller in the LVD for R and K in single person variability and MA in population variability (Table 1). Hemodilution with PBS demonstrated a strong correlation between platelet count and MA in the new device (R2 = 0.978), and LVD MA correlated strongly with TEG MA (R2 = 0.934). The new device was able to detect a signal in as little as 5% blood by volume, while TEG was able to detect a signal at 15% blood by volume.
Conclusion:This preliminary study compares CV of the LTD to TEG and demonstrates its superiority in certain metrics. The LTD accurately detects hemodilution of a blood sample. The device is also able to detect a clotting signal in more dilute blood than TEG, suggesting it is more sensitive.
