Abstract
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 whole blood coagulation.
Methods: Acoustic tweezing is used to levitate microliter drops of biopolymer and whole 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 and whole blood 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 exhibits a unique slope profile as it begins to clot. By exposing blood samples to pro- or anti-coagulants, the slope profile changes, allowing detection of hyper- or hypo-coagulable states.