Procoagulant Assessment of Topical Battlefield Hemostats Using a Novel Semi-Automated Whole Blood Clotting Assay System.
Authors: Moskowitz Keith A. 
Published: October 2019

A new granular smectite hemostatic agent (WoundStat™ [WS]) is capable of producing hemostasis during high pressure arterial bleeding (Ward et al., J Trauma, 63:276–284, 2007). The mechanism by which WS and other topical hemostatic agents help achieve clotting has not been investigated. In this study, the procoagulant and hemo-compatibility functions of WS were assessed using a novel whole blood clotting time assay, and its performance compared to current hemostatic agents QuikClot® zeolite granules (QC); CELOX™ marine biopolymer hemostatic granules (CX); sterile gauze bandage (SG); and to glass beads (GB). A modified whole blood recalcified clotting time assay was developed using the Actalyke® Mini II activated clotting time (ACT) analyzer and empty G-ACT tubes devoid of contact phase activating reagents. Whole citrated blood recalcified to 10 mM with CaCl2 yielded clot times (CT) of 217+/−6 sec, 212+/−11 sec, and 236+/−5 sec, respectively, for three normal donors. Addition of WS resulted in a time and dose-dependent biphasic decrease in CT. At 0.5 mg/ml, WS lowered CT by over 40% to 124+/−7 sec, 133+/− 9 sec, and 126+/−5 sec, p <0.001. Equal concentrations of QC also diminished CT ∼ 30% to 146+/−15 sec, 139+/−18 sec, and 184+/−22 sec, p< 0.02. Differences in CT between WS and QC were not significant. Surprisingly, 0.5 mg/ml CX did not exhibit procoagulant activity, as CT were on average 8% higher than controls (234+/−4 sec, 227+/−8 sec and 256+/−5 sec). SG and GB gave results within 5% of untreated samples. WS at ≥1.5 mg/ml clotted all samples in <90 sec, (the ACT instrument detection limit) and also significantly diminished CT of heparinized blood from 790 to 135 sec. All agents were hemocompatible as judged by the lack of change in hematocrit and hemoglobin complete blood count values after 45 min incubation. However, citrated blood incubated for <45 min with QC consistently demonstrated a drop in baseline platelet counts by >50,000 /μl while platelet counts in WS-treated specimens were similar to untreated controls (214,000/μl versus 219,000/μl) and clumped granules, presumably platelet-mediated, were visually apparent in the QC-treated bloods. Blood incubated with CX for up to 45 min also exhibited a drop in platelets from 204,000/μl to 150,000/μl. When QC, CX and WS were incubated in blood for 3 hours, corresponding to the maximal times recommended during field application prior to reapplication or surgical debridement, all hemostats resulted in an ∼ 50% reduction in platelet counts from 258,000/μl to 132,000/μl; 158,000/μl and 155,000 /μl, respectively. In summary, the data suggest that WS is hemocompatible, is moderately capable of inducing in vitro platelet aggregates, and may assist in the arrest of high-pressure arterial bleeding, at least in part by promoting the intrinsic contact phase of blood coagulation. Additional studies are required to further elucidate the potential platelet- and plasma-mediated mechanisms by which WS may help achieve hemostasis during severe arterial traumatic injury.