Hemorrhagic shock and tissue injury provoke distinct components of trauma-induced coagulopathy in a swine model

Abstract

Introduction: Tissue injury (TI) and hemorrhagic shock (HS) are the major contributors to trauma-induced coagulopathy (TIC). However, the individual contributions of these insults are difficult to discern clinically because they typically coexist. TI has been reported to release procoagulants, while HS has been associated with bleeding. We developed a large animal model to isolate TI and HS and characterize their individual mechanistic pathways. We hypothesized that while TI and HS are both drivers of TIC, they provoke different pathways; specifically, TI reduces time to clotting, whereas, HS decreases clot strength stimulates hyperfibrinolysis.

Methods: After induction of general anesthesia, 50 kg male, Yorkshire swine underwent isolated TI (bilateral muscle cutdown of quadriceps, bilateral femur fractures) or isolated HS (controlled bleeding to a base excess target of - 5 mmol/l) and observed for 240 min. Thrombelastography (TEG), calcium levels, thrombin activatable fibrinolysis inhibitor (TAFI), protein C, plasminogen activator inhibitor 1 (PAI-1), and plasminogen activator inhibitor 1/tissue-type plasminogen activator complex (PAI-1-tPA) were analyzed at pre-selected timepoints. Linear mixed models for repeated measures were used to compare results throughout the model.

Results: TI resulted in elevated histone release which peaked at 120 min (p = 0.02), and this was associated with reduced time to clot formation (R time) by 240 min (p = 0.006). HS decreased clot strength at time 30 min (p = 0.003), with a significant decline in calcium (p = 0.001). At study completion, HS animals had elevated PAI-1 (p = 0.01) and PAI-1-tPA (p = 0.04), showing a trend toward hyperfibrinolysis, while TI animals had suppressed fibrinolysis. Protein C, TAFI and skeletal myosin were not different among the groups.

Conclusion: Isolated injury in animal models can help elucidate the mechanistic pathways leading to TIC. Our results suggest that isolated TI leads to early histone release and a hypercoagulable state, with suppressed fibrinolysis. In contrast, HS promotes poor clot strength and hyperfibrinolysis resulting in hypocoagulability.

Keywords: Fibrinolysis; Hemorrhagic shock animal models; Tissue injury; Trauma-induced coagulopathy.

Fig. 1

Changes in mean arterial pressure (MAP, Panel A), heart rate (Panel B), end tidal carbon dioxide (EtCO₂, Panel C), and ionized calcium (Panel D) through the experiment. Statistical significance is only shown in Panel D, where *significant difference in HS compared to other groups (TI and SHAM); †significant change from baseline in HS group; (HS Hemorrhagic Shock, TI tissue injury);

Fig. 2

Native thromboelastography as a function of time. R-Time, time to clot formation (Panel A). Angle, rate of clot propagation (Panel B). Maximum amplitude, clot strength (Panel C). LY30, percentage of clot of lysis at 30 min (Panel D); *significant change from baseline in TI group; †significant change from baseline in HS group; (HS Hemorrhagic Shock, TI tissue injury)

Fig. 3

Thrombin activatable fibrinolysis inhibitor (TAFI, Panel A), Protein C (Panel B), Plasminogen activator inhibitor 1 (PAI-1, Panel C), and plasminogen activator inhibitor 1/tissue-type plasminogen activator complex (PAI-1-tPA, Panel D). *significant change from baseline in HS group; †significant difference between HS group compared to SHAM and TI groups. (HS Hemorrhagic Shock, TI tissue injury; SHAM: control)

Fig. 4

Relative abundance of myosin levels trended downward in the 250 kDa Heavy chains (Panel A) in the HS and TI groups. For the 160 kDa chain levels (Panel B), all groups showed a slight (nonsignificant) decrease in the relative abundance of this chain 30 min following the injury phase. No significant changes were detected in the 100 kDa chains in any group (Panel C). The TI group had increased histone levels (Panel D) following injury. *significant change from baseline in TI group; †significant difference compared to SHAM. (HS Hemorrhagic Shock, TI tissue injury)