Self-Propelled Dressings Containing Thrombin and Tranexamic Acid Improve Short-Term Survival in a Swine Model of Lethal Junctional Hemorrhage

Thrombin and Thrombin-Incorporated Biomaterials for Disease Treatments

Thrombin, a coagulation-inducing protease, has long been used in the hemostatic field. During the past decades, many other therapeutic uses of thrombin have been developed. For instance, burn treatment, pseudoaneurysm therapy, wound management, and tumor vascular infarction (or tumor vasculature blockade therapy) can all utilize the unique and powerful function of thrombin. Based on their therapeutic effects, many thrombin-associated products have been certificated by the Food and Drug Administration, including bovine thrombin, human thrombin, recombinant thrombin, fibrin glue, etc. Besides, several thrombin-based drugs are currently undergoing clinical trials. In this article, the therapeutic uses of thrombin (from the initial hemostasis to the latest cancer therapy), the commercially available drugs associated with thrombin, and the pros and cons of thrombin-based therapeutics (e.g., adverse immune responses related to bovine thrombin, thromboinflammation, and vasculogenic "rebounds") are summarized. Further, the current challenges and possible future research directions of thrombin-incorporated biomaterials and therapies are discussed. It is hoped that this review may provide a valuable reference for researchers in this field and help them to design safer and more effective thrombin-based drugs for fighting against various intractable diseases.

Recent Developments in Metallic Degradable Micromotors for Biomedical and Environmental Remediation Applications

Synthetic micromotor has gained substantial attention in biomedicine and environmental remediation. Metal-based degradable micromotor composed of magnesium (Mg), zinc (Zn), and iron (Fe) have promise due to their nontoxic fuel-free propulsion, favorable biocompatibility, and safe excretion of degradation products Recent advances in degradable metallic micromotor have shown their fast movement in complex biological media, efficient cargo delivery and favorable biocompatibility. A noteworthy number of degradable metal-based micromotors employ bubble propulsion, utilizing water as fuel to generate hydrogen bubbles. This novel feature has projected degradable metallic micromotors for active in vivo drug delivery applications. In addition, understanding the degradation mechanism of these micromotors is also a key parameter for their design and performance. Its propulsion efficiency and life span govern the overall performance of a degradable metallic micromotor. Here we review the design and recent advancements of metallic degradable micromotors. Furthermore, we describe the controlled degradation, efficient in vivo drug delivery, and built-in acid neutralization capabilities of degradable micromotors with versatile biomedical applications. Moreover, we discuss micromotors' efficacy in detecting and destroying environmental pollutants. Finally, we address the limitations and future research directions of degradable metallic micromotors.

Ruggedized Self-Propelling Hemostatic Gauze Delivers Low Dose of Thrombin and Systemic Tranexamic Acid and Achieves High Survival in Swine With Junctional Hemorrhage

INTRODUCTION

Hemorrhage is responsible for 91% of preventable prehospital deaths in combat. Bleeding from anatomic junctions such as the groin, neck, and axillae make up 19% of these deaths, and reports estimate that effective control of junctional hemorrhage could have prevented 5% of fatalities in Afghanistan. Hemostatic dressings are effective but are time-consuming to apply and are limited when proper packing and manual pressure are not feasible, such as during care under fire. CounterFlow-Gauze is a hemostatic dressing that is effective without compression and delivers thrombin and tranexamic acid into wounds. Here, an advanced prototype of CounterFlow-Gauze, containing a range of low thrombin doses, was tested in a lethal swine model of junctional hemorrhage. Outcomes were compared with those of Combat Gauze, the current dressing recommended by Tactical Combat Casualty Care.

MATERIALS AND METHODS

CounterFlow-Gauze containing thrombin doses of 0, 20, 200, and 500 IU was prepared. Swine received femoral arteriotomies, and CounterFlow-Gauze was packed into wounds without additional manual compression. In a separate study using a similar model of junctional hemorrhage without additional compression, CounterFlow-Gauze containing 500 IU thrombin was tested and compared with Combat Gauze. In both studies, the primary outcomes were survival to 3 h and volume of blood loss.

RESULTS

CounterFlow-Gauze with 200 and 500 IU had the highest 3-h survival, achieving 70 and 75% survival, respectively. CounterFlow-Gauze resulted in mean peak plasma tranexamic acid concentrations of 9.6 ± 1.0 µg/mL (mean ± SEM) within 3 h. In a separate study with smaller injury, CounterFlow-Gauze with 500 IU achieved 100% survival to 3 h compared with 92% in Combat Gauze animals.

CONCLUSIONS

An advanced preclinical prototype of CounterFlow-Gauze formulated with a minimized thrombin dose is highly effective at managing junctional hemorrhage without compression. These results demonstrate that CounterFlow-Gauze could be developed into a feasible alternative to Combat Gauze for hemorrhage control on the battlefield.

Efficacy and safety of CounterFlow in animal models of hemorrhage

LAY SUMMARY

The efficacy of current hemostatic technologies is limited by several factors. Outward blood flow washes hemostatic drugs away from the wound, and hemostatic drugs often require focus, training, and time to use correctly, are highly specific to one type of injury, or pose severe safety risks. CounterFlow is a novel product that could potentially save military and civilian lives by stopping heavy bleeding from a variety of organs and other bodily locations that current technology cannot easily treat. Upon contact with blood, CounterFlow releases bursts of gas to safely self-propel bio-degradable clot-forming and clot-stabilizing drugs against blood flow, delivering them to the source of bleeding. This unique mechanism allows CounterFlow to be applied quickly to a wide assortment of wounds and to act effectively with little management after application. CounterFlow was tested in multiple animal models representing common and deadly bleeding scenarios, including internal bleeding, care under fire without compression, and surgical bleeding, and it was found to outperform current care options by stopping bleeds faster and increasing survival times. CounterFlow is also safe to use and biocompatible. This narrative review summarizes studies testing the effectiveness and safety of CounterFlow, discusses useful applications, and describes future plans for the product.

Platelet-Inspired Intravenous Nanomedicine for Injury-Targeted Direct Delivery of Thrombin to Augment Hemostasis in Coagulopathies

Severe hemorrhage associated with trauma, surgery, and congenital or drug-induced coagulopathies can be life-threatening and requires rapid hemostatic management via topical, intracavitary, or intravenous routes. For injuries that are not easily accessible externally, intravenous hemostatic approaches are needed. The clinical gold standard for this is transfusion of blood products, but due to donor dependence, specialized storage requirements, high risk of contamination, and short shelf life, blood product use faces significant challenges. Consequently, recent research efforts are being focused on designing biosynthetic intravenous hemostats, using intravenous nanoparticles and polymer systems. Here we report on the design and evaluation of thrombin-loaded injury-site-targeted lipid nanoparticles (t-TLNPs) that can specifically localize at an injury site via platelet-mimetic anchorage to the von Willebrand factor (vWF) and collagen and directly release thrombin via diffusion and phospholipase-triggered particle destabilization, which can locally augment fibrin generation from fibrinogen for hemostatic action. We evaluated t-TLNPs in vitro in human blood and plasma, where hemostatic defects were created by platelet depletion and anticoagulation. Spectrophotometric studies of fibrin generation, rotational thromboelastometry (ROTEM)-based studies of clot viscoelasticity, and BioFlux-based real-time imaging of fibrin generation under simulated vascular flow conditions confirmed that t-TLNPs can restore fibrin in hemostatic dysfunction settings. Finally, the in vivo feasibility of t-TLNPs was tested by prophylactic administration in a tail-clip model and emergency administration in a liver-laceration model in mice with induced hemostatic defects. Treatment with t-TLNPs was able to significantly reduce bleeding in both models. Our studies demonstrate an intravenous nanomedicine approach for injury-site-targeted direct delivery of thrombin to augment hemostasis.

Hemostatic powders for gastrointestinal bleeding: a review of old, new, and emerging agents in a rapidly advancing field

Background and study aims  Hemostatic powders are increasingly used to address limitations in conventional endoscopic techniques for gastrointestinal bleeding. Various agents exist with different compositions, characteristics, efficacy, and adverse events (AEs). We sought to review existing hemostatic powders, from preclinical to established agents. Methods  A literature review on hemostatic powders for gastrointestinal bleeding was undertaken through a MEDLINE search from 2000-2021 and hand searching of articles. Relevant literature was critically appraised and reviewed for mechanism of action, hemostasis and rebleeding rate, factors associated with hemostatic failure, and AEs. Results  The most established agents are TC-325 (Hemospray), EndoClot, and Ankaferd Blood Stopper (ABS). These agents have been successfully applied to a variety of upper and lower gastrointestinal bleeding etiologies, in the form of primary, combination, salvage, and bridging therapy. Few AEs have been reported, including visceral perforation, venous embolism, and self-limited abdominal pain. Newer agents include CEGP-003 and UI-EWD, which have shown results similar to those for the older agents in initial clinical studies. All aforementioned powders have high immediate hemostasis rates, particularly in scenarios not amenable to conventional endoscopic methods, but are limited by significant rates of rebleeding. Other treatments include TDM-621 (PuraStat) consisting of a liquid hemostatic agent newly applied to endoscopy and self-propelling thrombin powder (CounterFlow Powder), a preclinical but promising agent. Conclusions  Rapid development of hemostatic powders and growing clinical expertise has established these agents as a valuable strategy in gastrointestinal bleeding. Further research will continue to refine the efficacy and applicability of these agents.

Percutaneous delivery of self-propelling thrombin-containing powder increases survival from non-compressible truncal hemorrhage in a swine model of coagulopathy and hypothermia

BACKGROUND

Non-compressible truncal hemorrhage (NCTH) remains a leading cause of preventable death on the battlefield. Definitively managing severe NCTH requires surgery within the first hour after injury, which is difficult when evacuating casualties from remote and austere environments. During delays to surgery, hemostatic interventions that are performed prehospital can prevent coagulopathy and hemorrhagic shock and increase the likelihood that casualties survive to receive definitive care. We previously reported that a self-propelling thrombin-containing powder (SPTP) can be delivered percutaneously into the abdomen as a minimally invasive intervention and can self-disperse through pooled blood to deliver the hemostatic agents thrombin and tranexamic acid (TXA) locally to noncompressible intracavitary wounds. We hypothesized that in swine with massive NCTH, dilutional coagulopathy and hypothermia, delivering SPTP could extend survival times.

METHODS

Ten swine (n = 5 per group) underwent NCTH from a Grade V liver injury following a midline laparotomy. The laparotomy was closed with sutures afterwards, creating a hemoperitoneum, and animals were managed with crystalloid fluid resuscitation, or crystalloid resuscitation and SPTP. SPTP was delivered into the closed abdomen using a CO2-powered spray device and a catheter placed into the hemoperitoneum, entering through the upper right quadrant using the Seldinger technique. Survival to one and three hours was recorded. In an additional animal, hemorrhage was created laparoscopically and SPTP was imaged in-situ within the abdomen to visually track dispersion of the particles.

RESULTS

SPTP dispersed as far as 35 +/- 5.0 cm within the abdomen. SPTP increased survival to one and three hours (Kaplan-Meier p = 0.007 for both). The median survival time was 61 minutes with SPTP and 31 minutes without (p = 0.016).

CONCLUSION

SPTP effectively disperses medications throughout a hemoperitoneum and increases survival in a model of NCTH. SPTP is a promising strategy for nonsurgical management of NCTH, warranting further testing of its safety and efficacy.

LEVEL OF EVIDENCE

Basic Science, N/A.

Percutaneous delivery of self-propelling hemostatic powder for managing non-compressible abdominal hemorrhage: a proof-of-concept study in swine

INTRODUCTION

Non-compressible intra-abdominal hemorrhage (NCIAH) is a major cause of preventable death on the battlefield and in civilian trauma. Currently, it can only be definitively managed with surgery, as there are limited strategies for controlling ongoing NCIAH in the prehospital environment. We hypothesized that a self-propelling thrombin-containing powder (SPTP) could increase survival in a swine model of NCIAH when delivered percutaneously into the closed abdomen using an engineered spray system.

MATERIALS AND METHODS

Nineteen swine underwent surgical laparotomy followed by a Grade V liver injury that created massive hemorrhage, before closing the abdomen with sutures. Animals either received treatment with standard of care fluid resuscitation (n=9) or the SPTP spray system (n=10), which consisted of a spray device and a 14 Fr catheter. Using the spray system, SPTP was delivered into a hemoperitoneum identified using a focused assessment with sonography in trauma (FAST) exam. Lactated Ringer's solution was administered to all animals to maintain a mean arterial pressure (MAP) of >50 mmHg. The primary outcome was percentage of animals surviving at three hours following injury.

RESULTS

In the swine model of NCIAH, a greater percentage of animals receiving SPTP survived to three hours, although differences were not significant. The SPTP spray system increased the median survival of animals from 1.6 hr in the fluid resuscitation group to 4.3 hr. The SPTP spray system delivered a total mass of 18.5 ± 1.0 g of SPTP. The mean change in intra-abdominal pressure following SPTP delivery was 5.2 ± 1.8 mmHg (mean ± SEM). The intervention time was 6.7 ± 1.7 min. No adverse effects related to the SPTP formulation or the spray system were observed. SPTP was especially beneficial in animals that had either severely elevated lactate concentrations or low mean arterial pressure of <35 mmHg shortly after injury.

CONCLUSIONS

This demonstrates proof-of-concept for use of a new minimally invasive procedure for managing NCIAH, which could extend survival time to enable patients to reach definitive surgical care.

Facile fabrication of soy protein isolate-functionalized nanofibers with enhanced biocompatibility and hemostatic effect on full-thickness skin injury

Extensive full-thickness skin defect lacks self-healing ability. Tissue engineering wound dressing is considered as the most promising approach to promote wound healing. In this study, a series of biocompatible and hemostatic nanofiber dressings were fabricated. Soy protein isolate (SPI) and poly(L-lactic acid) (PLLA) solutions were mixed in certain proportions for high-voltage electrospinning. The obtained products were coded as SPNF-n (n = 100, 80, 60 and 40, corresponding to the weight percentage of PLLA solution). We found that SPNF-n (n = 100, 80, 60 and 40) could facilitate the adhesion and spread of L929 cells. In particular, SPNF-80 was capable of promoting fibroblast proliferation and diminishing inflammation. Compared with the neat PLLA film (SPNF-100), the biosafety and hemostatic effect of SPNF-80 got significantly improved. The hemostatic effect of SPNF-80 was comparable with that of a commercial gelatin sponge. In vivo wound healing assay demonstrated that SPNF-80 could accelerate the wound healing process by enhancing vascularization, re-epithelization and collagen formation. In conclusion, our results reveal that SPNF-n has good biocompatibility and hemostatic effect, and exhibits great application potential in wound healing.

Emerging approaches to pre-hospital hemorrhage control: a narrative review

In the United States, trauma claims the lives of over 150,000 civilians each year. In military settings, trauma and exsanguination result in 50% of combat related deaths. The majority of these deaths result from uncontrolled non-compressible hemorrhage. Non-compressible hemorrhage often results from deep vascular injuries within the torso, however can also occur secondary to penetrating injuries that involve the extremities. Given the high mortality rates for non-compressible hemorrhage, rapid and effective management of patients suffering from hemorrhage is essential to good patient outcomes. Consequently, there has been increasing interest in solutions for point-of-injury hemorrhage control in trauma and military medicine. Undoubtedly there is a great need for prehospital hemostatic interventions that can be deployed by trained and untrained personnel. Since 2001, various hemostatic agents have been developed, each with its advantages based upon the type and severity of injury, wound size, wound location, accessibility to injury site, and the coagulation status of the patient. These agents are often used in the military setting as a temporizing measure prior to definitive therapy and include techniques such as resuscitative endovascular balloon occlusion of the aorta (REBOA) and bioengineered agents including ResQFoam, RevMedx’s XSTAT, Tranexamic acid (TXA), and QuikClot Combat Gauze (QCG). Here, we review the indications, composition, technique, efficacy, and outcomes of these hemostatic agents.

Hemostatic and Histopathological Effects of Local Mineral Zeolite and Tranexamic Acid in Experimental Femoral Artery Bleeding Model

Background/Aim: This study aimed to evaluate the effect of local zeolite and tranexamic acid application on hemostasis duration and histopathological changes in the experimental bleeding model, created by puncturing femoral arteries in rats.

Material and Methods: A total of 36 Sprague Dawley female rats weighing an average of 240 ± 20 g were used in the study. The three main study groups were the zeolite, zeolite+tranexamic acid, and control groups. Each group was sacrificed on the seventh and fourteenth days of the study, using subgroups for histopathological findings. After piercing the femoral artery of each rat, one gram of the material assigned to the group was applied to the bleeding site after which a 100-gram scale weight was placed on the site for 30 sec intervals, during which temperature was measured. The same sequence of procedures was repeated for the control group, using only standard compression. Statistical analysis was performed using IBM Statistical Package for Social Sciences (SPSS) 15 statistical software. Significance was evaluated at the level of p< 0.05.

Results: The bleeding stop time of the control group was significantly longer than the zeolite and zeolite+tranexamic groups (p< 0.05). There was no statistically significant difference between the zeolite and zeolite+tranexamic groups’ bleeding stop times (p> 0.05) or between the mean wound temperatures of the control and zeolite+tranexamic acid groups when bleeding stopped (p> 0.05).

Conclusions: The effectiveness of the zeolite group and zeolite+tranexamic acid mixture is more than the control group in ensuring bleeding control. Their efficacy has been clearly observed in providing hemostasis. In addition, it has been determined that zeolite tranexamic acid mixture causes less exothermic reaction than zeolite group. We believe that this new formula should be developed and used to guide new studies.

Severe upper gastrointestinal bleeding is halted by endoscopically delivered self-propelling thrombin powder: A porcine pilot study

Background and study aims  Hemostatic powders have emerged recently to treat upper gastrointestinal bleeding (UGIB). Previously, we developed a novel self-propelling thrombin powder (SPTP) that effectively manages external pulsatile arterial bleed without compression, by effervescing and carrying thrombin into the wound. Here, we tested if SPTP, sprayed endoscopically, can manage severe UGIB in a live porcine model. Materials and methods  Anesthetized pigs underwent laparotomy to insert the gastroepiploic vascular bundles into the stomach lumen via a gastrotomy. Bleeding was initiated endoscopically in the stomach by needle knife. SPTP was delivered to the site of bleeding from a CO ₂ -powered spray device using a 7 FR catheter. Successful primary hemostasis, time to hemostasis, and the mass of SPTP delivered were measured. Results  Hemostasis was achieved at all bleeding sites using SPTP. Mean time to hemostasis was 4.2 ± 0.9 minutes (mean ± standard error of the mean, n = 12). The average mass of SPTP delivered was 2.4 ± 0.6 g. Conclusions  In this pilot study, SPTP successfully stopped 12 cases of severe UGIB, demonstrating early promise asa novel hemostatic powder.

Medical Micro/Nanorobots in Precision Medicine

Advances in medical robots promise to improve modern medicine and the quality of life. Miniaturization of these robotic platforms has led to numerous applications that leverages precision medicine. In this review, the current trends of medical micro and nanorobotics for therapy, surgery, diagnosis, and medical imaging are discussed. The use of micro and nanorobots in precision medicine still faces technical, regulatory, and market challenges for their widespread use in clinical settings. Nevertheless, recent translations from proof of concept to in vivo studies demonstrate their potential toward precision medicine.

Topical tranexamic acid inhibits fibrinolysis more effectively when formulated with self-propelling particles

BACKGROUND

Endogenous fibrinolytic activation contributes to coagulopathy and mortality after trauma. Administering tranexamic acid (TXA), an antifibrinolytic agent, is one strategy to reduce bleeding; however, it must be given soon after injury to be effective and minimize adverse effects. Administering TXA topically to a wound site would decrease the time to treatment and could enable both local and systemic delivery if a suitable formulation existed to deliver the drug deep into wounds adequately.

OBJECTIVES

To determine whether self-propelling particles could increase the efficacy of TXA.

METHODS

Using previously developed self-propelling particles, which consist of calcium carbonate and generate CO2 gas, TXA was formulated to disperse in blood and wounds. The antifibrinolytic properties were assessed in vitro and in a murine tail bleeding assay. Self-propelled TXA was also tested in a swine model of junctional hemorrhage consisting of femoral arteriotomy without compression.

RESULTS

Self-propelled TXA was more effective than non-propelled formulations in stabilizing clots from lysis in vitro and reducing blood loss in mice. It was well tolerated when administered subcutaneously in mice up to 300 to 1000 mg/kg. When it was incorporated in gauze, four of six pigs treated after a femoral arteriotomy and without compression survived, and systemic concentrations of TXA reached approximately 6 mg/L within the first hour.

CONCLUSIONS

A formulation of TXA that disperses the drug in blood and wounds was effective in several models. It may have several advantages, including supporting local clot stabilization, reducing blood loss from wounds, and providing systemic delivery of TXA. This approach could both improve and simplify prehospital trauma care for penetrating injury.

Development of biomimetic antimicrobial platelet-like particles comprised of microgel nanogold composites

A blood clot is formed in response to bleeding by platelet aggregation and adherence to fibrin fibers. Platelets contract over time, stabilizing the clot, which contributes to wound healing. We have developed platelet-like particles (PLPs) that augment clotting and induce clot retraction by mimicking the fibrin-binding capabilities and morphology of native platelets. Wound repair following hemostasis can be complicated by infection; therefore, we aim to augment wound healing by combining PLPs with antimicrobial gold to develop nanogold composites (NGCs). PLPs were synthesized with N-isopropylacrylamide (NIPAm)/co-acrylic acid in a precipitation polymerization reaction and conjugated to a fibrin-specific antibody. Two methods were employed to create NGCs: 1) noncovalent swelling with aqueous gold nanospheres, and 2) covalent seeding and growth. Since the ability of PLPs to mimic platelet morphology and clot retraction requires a high degree of particle deformability, we investigated how PLPs created from NGCs affected these properties. Cryogenic Scanning Electron Microscopy (cryoSEM) and atomic force microscopy (AFM) demonstrated that particle deformability, platelet-mimetic morphology and clot retraction were maintained in NGC-based PLPs. The effect of NGCs on bacterial adhesion and growth was assessed with antimicrobial assays. These results demonstrate NGCs fabricated through noncovalent and covalent methods retain deformability necessary for clot collapse and exhibit some antimicrobial potential. Therefore, NGCs are promising materials for preventing hemorrhage and infection following trauma.

Tranexamic acid-loaded starch hemostatic microspheres

Efficacious hemostatics have significant potential for use in rapid exsanguinating hemorrhage control by emergency medical technicians or military medics nowadays. Current hemostatics focus primarily on speeding up the formation of blood clots, but inhibiting fibrinolysis is also critical for promoting coagulation and improving survival rates. Here we report a drug-loaded cross-linked microporous starch (TACMS) fabricated by loading tranexamic acid (TA) with antifibrinolytic properties into cross-linked microporous starch (CMS). The results showed that the cross-linking modification improved the mechanical properties and the particle density. The introduction of TA had no influence on water absorption of CMS. TACMS retained good physical hemostatic capacity and excellent biocompatibility. The prothrombin time (PT), activated partial thromboplastin time (APTT) and thrombin time (TT) of TACMS with 20 mg g⁻¹ of TA were shortened greatly, indicating the chemical hemostasis of TACMS. TACMS demonstrated a 70% reduction in clotting time in vitro compared to CMS, which effectively inhibited the dissolution of fibrin and increased the strength of blood clots. Importantly, TACMS presented excellent hemostatic performance in rabbit ear artery injury and rabbit liver injury and even better hemostatic ability than Arista®. In conclusion, cross-linking, enzyme hydrolysis and modification of starch greatly improved absorption speed, blood uptake capacity and mechanical strength, and the introduction of TA simultaneously amplified the physical hemostasis and inhibited the dissolution of fibrin. The potent hemostatic ability of TACMS resulted from the synergistic role of physical hemostasis and drug hemostasis. The results of the present study put forward TACMS as a safe and effective hemostatic system and present a platform for further optimization studies of materials with enhanced hemostatic capabilities for specific injury types.

Efficacious hemostatics have significant potential for use in rapid exsanguinating hemorrhage control by emergency medical technicians or military medics nowadays.

Engineering Intravenously Administered Nanoparticles to Reduce Infusion Reaction and Stop Bleeding in a Large Animal Model of Trauma

Bleeding from traumatic injury is the leading cause of death for young people across the world, but interventions are lacking. While many agents have shown promise in small animal models, translating the work to large animal models has been exceptionally difficult in great part because of infusion-associated complement activation to nanomaterials that leads to cardiopulmonary complications. Unfortunately, this reaction is seen in at least 10% of the population. We developed intravenously infusible hemostatic nanoparticles that were effective in stopping bleeding and improving survival in rodent models of trauma. To translate this work, we developed a porcine liver injury model. Infusion of the first generation of hemostatic nanoparticles and controls 5 min after injury led to massive vasodilation and exsanguination even at extremely low doses. In naïve animals, the physiological changes were consistent with a complement-associated infusion reaction. By tailoring the zeta potential, we were able to engineer a second generation of hemostatic nanoparticles and controls that did not exhibit the complement response at low and moderate doses but did at the highest doses. These second-generation nanoparticles led to cessation of bleeding within 10 min of administration even though some signs of vasodilation were still seen. While the complement response is still a challenge, this work is extremely encouraging in that it demonstrates that when the infusion-associated complement response is managed, hemostatic nanoparticles are capable of rapidly stopping bleeding in a large animal model of trauma.

Rapid hemostasis in a sheep model using particles that propel thrombin and tranexamic acid

OBJECTIVES/HYPOTHESIS

Bleeding during endoscopic sinus surgery and open surgeries can easily obstruct the surgeons' field of view and increase morbidity and risk of intraoperative complications. Intraoperative bleeding could potentially be addressed by a hemostatic agent that safely disperses itself through the escaping blood. We tested the safety and efficacy of a self-propelling formulation of thrombin and tranexamic acid (SPTT) in stopping bleeding in a paranasal sinus injury and in an open surgical carotid injury sheep model.

STUDY DESIGN

Interventional animal study.

METHODS

SPTT was tested in the sinonasal space following endoscopic injury to the inferior turbinate of six sheep, and to the common carotid artery following open surgical injury in eight sheep. In the nasal cavity, bleeding time and local inflammation were measured and compared to plain gauze. Following carotid arteriotomy, successful hemostasis and markers of thrombosis and coagulopathy were compared to Floseal.

RESULTS

SPTT significantly decreased bleeding times in the sinonasal space compared to plain gauze (mean difference = 3.8 minutes, P = .002). All of the carotid bleeds (100%) were successfully controlled with SPTT after 10 minutes of application under pressure, compared to 25% with Floseal. No adverse events were noted, and there was no evidence of thromboembolism.

CONCLUSIONS

SPTT significantly reduced bleeding time in a sheep model of surgical sinus bleeding and successfully stopped bleeding following catastrophic carotid artery injury, with no adverse events observed.

LEVEL OF EVIDENCE

NA Laryngoscope, 127:787-793, 2017.