Pilot Study of Frozen Platelet Extracellular Vesicles as a Therapeutic Agent in Hemorrhagic Shock in Rats.

BACKGROUND: Hemorrhage accounts for the most preventable deaths after trauma. Resuscitation is guided by studies that demonstrate improved outcomes in patients receiving whole blood or balanced administration of blood products. Platelets present a logistical challenge due to short shelf life and need for refrigeration. Platelet derived extracellular vesicles (PEVs) are a possible platelet alternative. PEVs are secreted from platelets, have hemostatic effects and mitigate inflammation and vascular injury, similar to platelets. This pilot study aimed to elucidate the therapeutic effects of PEVs in a rat model of uncontrolled hemorrhage.

METHODS: Male rats were anesthetized and femoral vessels cannulated. Vital signs (MAP, HR, and RR) were monitored. Electrolytes, lactate and ABG were obtained at baseline, 1-hour and 3-hours post injury. Laparotomy was performed, 50% of the middle hepatic lobe excised and the abdomen packed with gauze. Rats received 2 mL PEVs or lactated Ringers (LR) over 6 minutes immediately after injury. Peritoneal blood loss was quantified using pre-weighed gauze at 5, 15, 30, 45 and 60 minutes. Laparotomy was closed 1-hour post-injury. Animals were monitored for 3-hours post-injury then euthanized. Generalized Linear Mixed Effects models were performed to assess effects of treatment and time on lactate and MAP.

RESULTS: 21 rats were included (11 LR, 10 PEV). Overall blood loss was between 6-10 mL and not significantly different between groups. There was a 36% mortality rate in the LR group and 0% mortality in the PEV group (p = 0.03). The LR group had significantly higher lactates at 1 hour (p = 0.025). At 15, 45, 60, and 180 minutes the MAP of the PEV group was significantly higher than the LR group.

CONCLUSION: Early studies are encouraging regarding the potential use of PEVs in uncontrolled hemorrhagic shock based on improved survival and hemodynamics.