Red Cell Microparticles (RMP) Correct Factor Deficiencies and Hemodilution: Evaluation by Thromboelastography (TEG)
Authors: Johansen Max E , Jy Wenche , Horstman Lawrence L , Bidot Carlos , Ahn Yeon S 
Published: October 2019

Abstract
Abstract 2254

Introduction:
We have recently reported that RMP are active in correcting a wide range of clotting defects, and suggested that RMP could be useful as a hemostatic agent for treating bleeding conditions. In this report, we investigate the effect of RMP on factor-deficient plasmas, and hemodilution in whole blood, by TEG. We tested varying levels of factor-deficient plasmas, and several degrees of hemodilution. Factor deficiency can range from mild (∼50%) to severe (∼99%), abrogating fibrin formation. Similarly, infusions of IV fluids in management of patients with trauma after massive hemorrhage resulting in hemodilution, leading to complex coagulopathy. This includes dilution of coagulation factors and release of inhibitors that can lead to a prothrombotic state, which can then result in factor exhaustion, exacerbating hemorrhagic diathesis. The effects of RMP on this complex coagulopathy is investigated.

Methods:
(i) RMP were prepared by high-pressure extrusion of washed packed RBCs. (ii) Factor deficient plasmas (FII, FV, FVII, FVIII, FIX, FX, FXI, FXII, FXIII) were mixed with pooled normal plasma to achieve deficiencies ranging from 75%-95% depletion, in 5% increments, incubated with kaolin for 2 min, then assayed by TEG +/− RMP. (iii) For hemodilution experiments, whole citrated blood from healthy controls was mixed with increasing volume percentages of saline, then subjected to TEG +/− RMP.

Results:
(1) Factor Deficiency: RMP effectively shortened R (lag to reaction) and k (clotting rate) in all deficient plasmas, most prominently in FII, FVIII, FIX, and FX. While in other factors the RMP effect disappeared at >85% deficiency, these factors (II, VIII, IX, X) were significantly corrected even at 90% and 95% deficiency. The CI (coagulation index) was also consistently higher in presence of RMP, suggesting a global correction of coagulation profile, but MA (maximum amplitude) and G (shear elastic modulus) were unaffected by RMP at all levels of deficiency. (2) Hemodilution: Addition of RMP improved R time by 50% and k time by 40% on average, both at p<0.01. Angle ‘a’ was increased by 30–50% (p=0.01), although this effect was pronounced only at milder levels of dilution. Again, MA and G were not significantly affected, except for modest improvement (10–15%) in the least diluted samples. However, CI consistently reflected an improved coagulation profile in presence of RMP (p<0.03). Counter-intuitively, R time initially decreased as dilution increased, but at >50% dilution this trend reversed and R times became longer with more dilution.

Conclusions:
(1) With regard to the use of RMP in therapy for bleeding, these results suggest efficacy of RMP in the treatment or prevention of coagulopathies due to hemodilution, and for factor deficiencies, especially of FII, FVIII, FIX, and FX. (2) With regard to mechanism, the absence of an effect of RMP on MA or G, which depend strongly on platelets, indicates that RMP cannot substitute for all aspects of platelet function. (Platelets were essentially absent from the deficient plasmas.) We surmise that the main activity of RMP in these experiments is to provide procoagulant phospholipids, especially for the tenase complex, but they may contribute other activities as well. In summary, these data further support the potential for RMP to correct a wide variety of coagulopathies resulting from single or multiple factor deficiencies, and may be an effective treatment for conditions including hemophilia, thrombocytopenia, and coagulopathy from hemodilution.

Disclosures:
No relevant conflicts of interest to declare.