Post-Injury Treatment with Rapid Intraosseous Injection of Lyophilized Synthetic Platelets Enhances Survival, Hemostasis, and Hemodynamics in a Rat Model of Liver Laceration

Introduction

Trauma is the leading cause of death for individuals under 45 years old, with uncontrolled bleeding being a significant contributor to preventable death. Our previous study demonstrated the effectiveness of a bioinspired synthetic platelet (SP) administered intravenously before injury in reducing blood loss in a rabbit liver laceration model (Srinivasan et al., 2024). Building on this, recent development efforts have successfully generated a shelf-stable lyophilized formulation of the synthetic platelets (Lyo-SP). Furthermore, intraosseous (IO) injection is commonly used in pre-hospital and combat medicine due to its ease and high success rate. However, to our knowledge, liposomal hemostatic particles have never been tested in IO infusion, and testing the impact of Lyo-SP in hemostasis via IO delivery would add a high degree of clinical relevance to SP resuscitation. We hypothesized that administering Lyo-SP IO immediately post-injury would decrease blood loss, increase survival, and improve hemodynamics in a rat model of liver laceration.

Methods

Lyophilized particles were reconstituted 15 minutes prior to injection. A pilot safety study was conducted with 6 rats (Wistar outbred rats, 12 weeks old, Envigo). For the efficacy study, 36 rats were randomly assigned to receive either 0.5 mg/kg Lyo-SP, 0.5 mg/kg Lyophilized Control Particles (Lyo-CP), or Vehicle. Under general anesthesia, a catheter was placed in the left femoral artery for vital monitoring. A 22G needle was drilled and inserted into the right tibia. A laparotomy was performed, and the liver was packed posteriorly with 0.5 g of gauze. The liver was lacerated with a 15-blade perpendicularly at the center 4 times per lobe across 3 lobes followed by immediate bolus administration of 1 ml of either Lyo-SP, Lyo-CP, or Vehicle through the 22G needle to the osseous cavity of the right tibia. Mean arterial pressure (MAP) was recorded pre-injury and every minute thereafter. After 30 minutes, the abdominal cavity was swept with another 0.5 g of gauze, and both gauzes were weighed to determine blood loss. The animals were then sacrificed. Blood samples were collected via cardiac puncture. Continuous data were represented as mean ± standard error of the mean, and all other data as mean ± standard deviation. Data analysis was performed using one-way ANOVA with multiple comparisons (significance level of α = 0.05).

Results

The pilot safety study showed that IO injection of Lyo-SP rapidly entered circulation and was safe at doses up to 40 times the effective dosage. In the efficacy study, IO injection of 0.5 mg/kg Lyo-SP immediately post-injury significantly reduced blood loss by approximately 50% compared to the vehicle and Lyo-CP treated groups (p < 0.0001). While Lyo-CP and vehicle-treated rats exhibited lethality (25% and 16.7%, respectively) potentially due to hemorrhagic shock, no deaths were observed in the Lyo-SP treated group. Lyo-SP treated rats maintained significantly higher MAP immediately after injury and throughout the study (30 minutes) when quantified with AUC compared to Lyo-CP (p < 0.01) and Vehicle (p < 0.001) treated groups. Correlational analysis revealed that while Lyo-CP and vehicle-treated groups showed a correlation between higher blood loss and lower final MAP (R² = 0.5317 and 0.7957, respectively), this correlation was absent in the Lyo-SP group (R² = 0.1260), demonstrating resistance to pressure drops under higher blood loss. Lyo-SP treated rats also spent significantly less time in hypotension (p < 0.01 to Vehicle and p < 0.001 to Lyo-CP) and demonstrated faster recovery of MAP following the injury (p < 0.05 to Lyo-CP).

Conclusion

To our knowledge, this is the first study to demonstrate the administration of shelf-stable Lyo-SP via IO injection to reduce hemorrhage after trauma in rats. This is significant for pre-hospital and combat settings where resources are limited, and rapid hemostasis is critical. Our findings indicate that Lyo-SP not only reduces blood loss and improves hemodynamics but also enhances survival. The observed higher MAP, resistance to pressure drops under high blood loss, reduced time in hypotension, and faster MAP recovery highlight the potential of Lyo-SP as a possible effective future treatment in emergency trauma care. Our current findings could potentially improve the management of traumatic hemorrhage and enhance patient outcomes in both civilian and military trauma cases.