Quasi‐static acoustic tweezing thromboelastometry

Abstract

Summary Background Thromboelastography is widely used as a tool to assess the coagulation status of surgical patients. It allows observation of changes in material properties of whole blood, beginning with early stages of clot formation and ending with clot lysis. However, the contact activation of the coagulation cascade at surfaces of thromboelastographic systems leads to inherent variability and unreliability in predicting bleeding or thrombosis risks. Objectives To develop acoustic tweezing thromboelastometry as a noncontact method for perioperative assessment of blood coagulation. Methods Acoustic tweezing is used to levitate microliter drops of biopolymer and human blood samples. By quasi-statically changing the acoustic pressure we control the sample drop location and deformation. Sample size, deformation and location are determined by digital imaging at each pressure. Results Simple Newtonian liquid solutions maintain a constant, reversible location vs deformation curve. In contrast, the deformation/location curves for gelatin, alginate, whole blood, and blood plasma uniquely change as the samples solidify. Increasing elasticity causes the sample to deform less, leading to steeper stress/strain curves. By extracting a linear regime slope, we show that whole blood or blood plasma exhibits a unique slope profile as it begins to clot. By exposing blood samples to pro- or anti-thrombotic agents, the slope profile changes, allowing detection of hyper- or hypo-coagulable states. Conclusions We demonstrate that quasi-static acoustic tweezing can yield information about clotting onset, maturation, and strength. The advantages of small sample size, non-contact and rapid measurement make this technique desirable for real-time monitoring of blood coagulation.

Shape oscillations of single blood drops: applications to human blood and sickle cell disease

“…Holt et al . 42 utilized acoustic levitation to study the hemostasis of drops of whole blood. Using acoustic levitation coupled with Raman spectroscopy, Puskar et al .…”

Drop-of-sample rheometry of biological fluids by noncontact acoustic tweezing spectroscopy

“…Eqn (6) were used to generate the viscosity calibration curves. By applying the calibration curves to experimental data, we measured the viscosities of the following polymer solutions: dextran solutions, which are Newtonian fluids (no elasticity 35 ), xanthan gum solutions, which show timeindependent viscoelasticity, 42 and gelatin solutions whose viscoelastic properties change during gelation 43 (Fig. 4).…”

Monitoring of blood coagulation with non‐contact drop oscillation rheometry

“…On comparison with TEG, DOR is able to reproduce the results of TEG, while also providing information about dissipative effects ( G ″) and their evolution during clotting. DOR, like its previously reported static counterpart QATT, requires only a single drop of blood, which is 1/30 of the standard sample size.…”

“…A method allowing both non‐contact containment and manipulation in coagulation measurement was introduced by Holt et al This method, referred to as quasi‐static acoustic tweezing thromboelastometry (QATT), inferred changes in tensile elasticity (elastic modulus or firmness) of a coagulating drop of blood by employing imaging to measure its static deformation during acoustic levitation. Hosseinzadeh et al added an optical scattering diagnostic in order to measure the viscosity of normal and sickled blood.…”