Reproducibility of an animal model simulating complex combat-related injury in a multiple-institution format

A Novel Pre-Clinical Modeling of Massive Hemorrhagic Shock in Non-Human Primate: A Safe and Reproducible Method (Macaca fascicularis)

BACKGROUND

Although non-human primates are the closest animals to humans to simulate physiological and metabolic responses, there is a paucity of primate hemorrhagic shock models that are standardized and reproducible. Herein, we describe a model that is a clinical replica of extreme class IV hemorrhagic shock with a step-by-step description of the procedure in cynomolgus macaque monkeys.

METHODS

The physiological changes that occurred during the process were evaluated using hemodynamic parameters, echocardiogram, and laboratory values. Five female monkeys were subjected to trauma laparotomy, followed by cannulation of the abdominal aorta to achieve graded hemorrhage. A central line was placed in the right internal jugular vein, which was subsequently used for laboratory sampling and volume resuscitation. The withdrawal of blood was ceased when a predefined cardiac endpoint with cardiac arrhythmia or bradycardia was reached. The animals were then immediately resuscitated with transfusion. The primary cardiac endpoint was consistently reached in all 5 animals during the fourth hemorrhage when more than 70% of the estimated total blood volume was lost.

RESULTS

No mortality occurred during the process. The blood pressure, cardiac output measured from an echocardiogram, and hemoglobin correlated well with increasing loss of circulating volume, whereas the pulse pressure variation did not. The echocardiogram was also a useful predictor for urgent volume replacement.

CONCLUSION

This model offers a safe and reproducible surgical hemorrhagic model in non-human primates and simulates clinical practice. This could provide a useful platform on which further studies can be carried out to address unanswered questions in trauma management.

Transforming research to improve therapies for trauma in the twenty-first century

Improvements have been made in optimizing initial care of trauma patients, both in prehospital systems as well as in the emergency department, and these have also favorably affected longer term outcomes. However, as specific treatments for bleeding are largely lacking, many patients continue to die from hemorrhage. Also, major knowledge gaps remain on the impact of tissue injury on the host immune and coagulation response, which hampers the development of interventions to treat or prevent organ failure, thrombosis, infections or other complications of trauma. Thereby, trauma remains a challenge for intensivists. This review describes the most pressing research questions in trauma, as well as new approaches to trauma research, with the aim to bring improved therapies to the bedside within the twenty-first century.

A combat casualty relevant dismounted complex blast injury model in swine

BACKGROUND

Improvised explosive devices have resulted in a unique polytrauma injury pattern termed dismounted complex blast injury (DCBI), which is frequent in the modern military theater. Dismounted complex blast injury is characterized by extremity amputations, junctional vascular injury, and blast traumatic brain injury (bTBI). We developed a combat casualty relevant DCBI swine model, which combines hemorrhagic shock (HS) and tissue injury (TI) with a bTBI, to study interventions in this unique and devastating military injury pattern.

METHODS

A 50-kg male Yorkshire swine were randomized to the DCBI or SHAM group (instrumentation only). Those in the DCBI group were subjected to HS, TI, and bTBI. The blast injury was applied using a 55-psi shock tube wave. Tissue injury was created with bilateral open femur fractures. Hemorrhagic shock was induced by bleeding from femoral arteries to target pressure. A resuscitation protocol modified from the Tactical Combat Casualty Care guidelines simulated battlefield resuscitation for 240 minutes.

RESULTS

Eight swine underwent the DCBI model and five were allocated to the SHAM group. In the DCBI model the mean base excess achieved at the end of the HS shock was -8.57 ± 5.13 mmol·L -1 . A significant coagulopathy was detected in the DCBI model as measured by prothrombin time (15.8 seconds DCBI vs. 12.86 seconds SHAM; p = 0.02) and thromboelastography maximum amplitude (68.5 mm DCBI vs. 78.3 mm in SHAM; p = 0.0003). For the DCBI models, intracranial pressure (ICP) increased by a mean of 13 mm Hg, reaching a final ICP of 24 ± 7.7 mm Hg.

CONCLUSION

We created a reproducible large animal model to study the combined effects of severe HS, TI, and bTBI on coagulation and ICP in the setting of DCBI, with significant translational applications for the care of military warfighters. Within the 4-hour observational period, the swine developed a consistent coagulopathy with a concurrent brain injury evidenced by increasing ICP.

Blast polytrauma with hemodynamic shock, hypothermia, hypoventilation and systemic inflammatory response: description of a new porcine model

PURPOSE

In the past decade blast injuries have become more prevalent. Blast trauma may cause extensive injuries requiring improved early resuscitation and prevention of haemorrhage. Randomized prospective trials are logistically and ethically challenging, and large animal models are important for further research efforts. Few severe blast trauma models have been described, which is why we aimed to establish a comprehensive polytrauma model in accordance with the criteria of the Berlin definition of polytrauma and with a survival time of > 2 h. Multiple blast injuries to the groin and abdomen were combined with hypoperfusion, respiratory and metabolic acidosis, hypoventilation, hypothermia and inflammatory response. The model was compared to lung contusion and haemorrhage.

METHODS

16 landrace swine (mean weight 60.5 kg) were randomized to "control" (n = 5), "chest trauma/hem" by lung contusion and class II haemorrhage (n = 5), and "blast polytrauma" caused by multiple blast injuries to the groin and abdomen, class II haemorrhage, lipopolysaccharide (LPS) infusion and hypothermia 32 °C (n = 6).

RESULTS

The blast polytrauma group had an Injury Severity Score of 57 which resulted in haemodynamic shock, hypothermia, respiratory and metabolic acidosis and inflammatory response. The chest trauma/hem group had an Injury Severity Score of 9 and less profound physiologic effects. Physiologic parameters presented a dose-response relationship corresponding to the trauma levels.

CONCLUSION

A comprehensive blast polytrauma model fulfilling the Berlin polytrauma criteria, with a high trauma load and a survival time of > 2 h was established. A severe, but consistent, injury profile was accomplished enabling the addition of experimental interventions in future studies, particularly of immediate resuscitation efforts including whole blood administration, trauma packing and haemostasis.

A Multifunctional, Low-Volume Resuscitation Cocktail Improves Vital Organ Blood Flow and Hemostasis in a Pig Model of Polytrauma with Traumatic Brain Injury

The resuscitation of polytrauma with hemorrhagic shock and traumatic brain injury (TBI) is a balance between permissive hypotension and maintaining vital organ perfusion. There is no current optimal solution. This study tested whether a multifunctional resuscitation cocktail supporting hemostasis and perfusion could mitigate blood loss while improving vital organ blood flow during prolonged limited resuscitation. Anesthetized Yorkshire swine were subjected to fluid percussion TBI, femur fracture, catheter hemorrhage, and aortic tear. Fluid resuscitation was started when lactate concentration reached 3–4 mmol/L. Animals were randomized to one of five groups. All groups received hydroxyethyl starch solution and vasopressin. Low- and high-dose fibrinogen (FBG) groups additionally received 100 and 200 mg/kg FBG, respectively. A third group received TXA and low-dose FBG. Two control groups received albumin, with one also including TXA. Animals were monitored for up to 6 h. Blood loss was decreased and vital organ blood flow was improved with low- and high-dose fibrinogen compared to albumin controls, but survival was not improved. There was no additional benefit of high- vs. low-dose FBG on blood loss or survival. TXA alone decreased blood loss but had no effect on survival, and combining TXA with FBG provided no additional benefit. Pooled analysis of all groups containing fibrinogen vs. albumin controls found improved survival, decreased blood loss, and improved vital organ blood flow with fibrinogen delivery. In conclusion, a low-volume resuscitation cocktail consisting of hydroxyethyl starch, vasopressin, and fibrinogen concentrate improved outcomes compare to controls during limited resuscitation of polytrauma.

Metabolic Profiling of a Porcine Combat Trauma-Injury Model Using NMR and Multi-Mode LC-MS Metabolomics-A Preliminary Study

Profiles of combat injuries worldwide have shown that penetrating trauma is one of the most common injuries sustained during battle. This is usually accompanied by severe bleeding or hemorrhage. If the soldier does not bleed to death, he may eventually succumb to complications arising from trauma hemorrhagic shock (THS). THS occurs when there is a deficiency of oxygen reaching the organs due to excessive blood loss. It can trigger massive metabolic derangements and an overwhelming inflammatory response, which can subsequently lead to the failure of organs and possibly death. A better understanding of the acute metabolic changes occurring after THS can help in the development of interventional strategies, as well as lead to the identification of potential biomarkers for rapid diagnosis of hemorrhagic shock and organ failure. In this preliminary study, a metabolomic approach using the complementary platforms of nuclear magnetic resonance (NMR) spectroscopy and liquid chromatography coupled with mass spectrometry (LC-MS) was used to determine the metabolic changes occurring in a porcine model of combat trauma injury comprising of penetrating trauma to a limb with hemorrhagic shock. Several metabolites associated with the acute-phase reaction, inflammation, energy depletion, oxidative stress, and possible renal dysfunction were identified to be significantly changed after a thirty-minute shock period.

Differentiation of Antemortem and Postmortem Appendicular Fractures Using Magnetic Resonance Imaging Signal Intensity Changes in Bone and Soft Tissues

Intraosseous T1-weighted (T1W) and short-tau inversion recovery (STIR) magnetic resonance imaging (MRI) signal intensity changes-so-called bone marrow edema-may be able to differentiate antemortem and postmortem fractures in human forensic imaging. The primary objective of this study was to investigate this hypothesis using an animal model. Three juvenile Landrace pigs were anesthetized and underwent MRI of both tibiae and both radii using a 1.5 T magnet. T1W, T2-weighted (T2W), STIR, and T2* sequences were included. Antemortem fractures were induced in both tibiae and postmortem fractures in both radii, and MRI was repeated. Two board-certified radiologists blinded to fracture group jointly evaluated the images for intraosseous and soft tissue signal intensity changes. Sensitivity (Se) and specificity (Sp) in identifying antemortem fractures were calculated based on intraosseous, soft tissue, and combined intraosseous and soft tissue signal intensity changes. Intraosseous and soft tissue signal intensity changes, when present, were hyperintense in all sequences. Intraosseous hyperintensity in T1W and T2W sequences yielded Sp of 100% for antemortem fractures. Regardless of sequence, soft tissue hyperintensity was comparatively more sensitive than intraosseous hyperintensity. Sensitivity for each sequence could be maximized by assessment of soft tissue and intraosseous hyperintense signals together; for the T1W sequence, such assessment optimized diagnostic utility yielding a Se of 100% and Sp of 83%. In summary, MRI-particularly the T1W sequence-can differentiate antemortem and postmortem fractures and may be a useful adjunct to the forensic analyses of fractures.

A systematic review of large animal models of combined traumatic brain injury and hemorrhagic shock

Traumatic brain injury (TBI) and severe blood loss (SBL) frequently co-occur in human trauma, resulting in high levels of mortality and morbidity. Importantly, each of the individual post-injury cascades is characterized by complex and potentially opposing pathophysiological responses, complicating optimal resuscitation and therapeutic approaches. Large animal models of poly-neurotrauma closely mimic human physiology, but a systematic literature review of published models has been lacking. The current review suggests a relative paucity of large animal poly-neurotrauma studies (N = 52), with meta-statistics revealing trends for animal species (exclusively swine), characteristics (use of single biological sex, use of juveniles) and TBI models. Although most studies have targeted blood loss volumes of 35-45%, the associated mortality rates are much lower relative to Class III/IV human trauma. This discrepancy may result from potentially mitigating experimental factors (e.g., mechanical ventilation prior to or during injury, pausing/resuming blood loss based on physiological parameters, administration of small volume fluid resuscitation) that are rarely associated with human trauma, highlighting the need for additional work in this area.

Efficacy of the perfluorocarbon dodecafluoropentane as an adjunct to pre-hospital resuscitation

BACKGROUND

Hemorrhage is the most common cause of preventable death in the pre-hospital phase in trauma, with a critical capability gap optimizing pre-hospital resuscitation in austere environments. One promising avenue is the concept of a multi-functional resuscitation fluid (MRF) that contains a blood product backbone with agents that promote clotting and enhance oxygen delivery. Oxygen therapeutics, such as hemoglobin based oxygen carriers(HBOCs) and perfluorocarbons(PFCs), may be a critical MRF component. Our purpose was to assess the efficacy of resuscitation with a PFC, dodecafluoropentane(DDFPe), compared to fresh whole blood(FWB).

METHODS AND FINDINGS

Forty-five swine(78±5kg) underwent splenectomy and controlled hemorrhage via femoral arterial catheter until shock physiology(lactate = 7.0) was achieved prior to randomization into the following groups: 1) Control-no intervention, 2)Hextend-500mL, 3)FFP-500mL, 4)FFP+DDFPe-500mL, 5)FWB-500mL. Animals were observed for an additional 180 minutes following randomization.

RESULTS

Baseline physiologic values did not statistically differ. At T = 60min, FWB had significantly decreased lactate(p = 0.001) and DDFPe was not statistically different from control. There was no statistical significance in tissue oxygenation(StO2) between groups at T = 60min. Survival was highest in the FWB and Hextend groups(30% at 180min). Kaplan-Meier analysis showed decreased survival of DDFPe+FFP in comparison to FWB(p<0.05) and was not significantly different from control or FFP. Four animals who received DDFPe died within 10 minutes of administration. This study was limited by a group receiving DDFPe alone, however this would not be feasible in this lethal swine model as DDFPe given its small volume.

CONCLUSION

DDFPe administration with FFP does not improve survival or enhance tissue oxygenation. However, given similar survival rates of Hextend and FWB, there is evidence that an ideal MRF should contain an element of volume expansion to enhance oxygen delivery.

Fluid administration rate for uncontrolled intraabdominal hemorrhage in swine

Background

We hypothesized that slow crystalloid resuscitation would result in less blood loss and a smaller hemoglobin decrease compared to a rapid resuscitation during uncontrolled hemorrhage.

Methods

Anesthetized, splenectomized domestic swine underwent hepatic lobar hemitransection. Lactated Ringers was given at 150 or 20 mL/min IV (rapid vs. slow, respectively, N = 12 per group; limit of 100 mL/kg). Primary endpoints were blood loss and serum hemoglobin; secondary endpoints included survival, vital signs, coagulation parameters, and blood gases.

Results

The slow group had a less blood loss (1.6 vs. 2.7 L, respectively) and a higher final hemoglobin concentration (6.0 vs. 3.4 g/dL).

Conclusions

Using a fixed volume of crystalloid resuscitation in this porcine model of uncontrolled intraabdominal hemorrhage, a slow IV infusion rate produced less blood loss and a smaller hemoglobin decrease compared to rapid infusion.

A novel model of highly lethal uncontrolled torso hemorrhage in swine

INTRODUCTION

A reproducible, lethal noncompressible torso hemorrhage model is important to civilian and military trauma research. Current large animal models balancing clinical applicability with standardization and internal validity. As such, large animal models of trauma vary widely in the surgical literature, limiting comparisons. Our aim was to create and validate a porcine model of uncontrolled hemorrhage that maximizes reproducibility and standardization.

METHODS

Seven Yorkshire-cross swine were anesthetized, instrumented, and splenectomized. A simple liver tourniquet was applied before injury to prevent unregulated hemorrhage while creating a traumatic amputation of 30% of the liver. Release of the tourniquet and rapid abdominal closure following injury provided a standardized reference point for the onset and duration of uncontrolled hemorrhage. At the moment of death, the liver tourniquet was quickly reapplied to provide accurate quantification of intra-abdominal blood loss. Weight and volume of the resected and residual liver segments were measured. Hemodynamic parameters were recorded continuously throughout each experiment.

RESULTS

This liver injury was rapidly and universally lethal (11.2 ± 4.9 min). The volume of hemorrhage (35.8% ± 6% of total blood volume) and severity of uncontrolled hemorrhage (100% of animals deteriorated to a sustained mean arterial pressure <35 mmHg for 5 min) were consistent across all animals. Use of the tourniquet effectively halted preprocedure and postprocedure blood loss allowing for accurate quantification of amount of hemorrhage over a defined period. In addition, the tourniquet facilitated the creation of a consistent liver resection weight (0.0043 ± 0.0003 liver resection weight: body weight) and as a percentage of total liver resection weight (27% ± 2.2%).

CONCLUSIONS

This novel tourniquet-assisted noncompressible torso hemorrhage model creates a standardized, reproducible, highly lethal, and clinically applicable injury in swine. Use of the tourniquet allowed for consistent liver injury and precise control over hemorrhage. Recorded blood loss was similar across all animals. Improving reproducibility and standardization has the potential to offer improvements in large animal translational models of hemorrhage.

LEVEL OF EVIDENCE

Level I.

The Reversal of Direct Oral Anticoagulants in Animal Models

Several direct oral anticoagulants (DOACs), including direct thrombin and factor Xa inhibitors, have been approved as alternatives to vitamin K antagonist anticoagulants. As with any anticoagulant, DOAC use carries a risk of bleeding. In patients with major bleeding or needing urgent surgery, reversal of DOAC anticoagulation may be required, presenting a clinical challenge. The optimal strategy for DOAC reversal is being refined, and may include use of hemostatic agents such as prothrombin complex concentrates (PCCs; a source of concentrated clotting factors), or DOAC-specific antidotes (which bind their target DOAC to abrogate its activity). Though promising, most specific antidotes are still in development.Preclinical animal research is the key to establishing the efficacy and safety of potential reversal agents. Here, we summarize published preclinical animal studies on reversal of DOAC anticoagulation. These studies (n = 26) were identified via a PubMed search, and used rodent, rabbit, pig, and non-human primate models. The larger of these animals have the advantages of similar blood volume/hemodynamics to humans, and can be used to model polytrauma. We find that in addition to varied species being used, there is variability in the models and assays used between studies; we suggest that blood loss (bleeding volume) is the most clinically relevant measure of DOAC anticoagulation-related bleeding and its reversal.The studies covered indicate that both PCCs and specific reversal agents have the potential to be used as part of a clinical strategy for DOAC reversal. For the future, we advocate the development and use of standardized, clinically, and pharmacologically relevant animal models to study novel DOAC reversal strategies.

Characterization of blunt chest trauma in a long-term porcine model of severe multiple trauma

Chest trauma has a significant relevance on outcome after severe trauma. Clinically, impaired lung function typically occurs within 72 hours after trauma. However, the underlying pathophysiological mechanisms are still not fully elucidated. Therefore, we aimed to establish an experimental long-term model to investigate physiological, morphologic and inflammatory changes, after severe trauma. Male pigs (sus scrofa) sustained severe trauma (including unilateral chest trauma, femur fracture, liver laceration and hemorrhagic shock). Additionally, non-injured animals served as sham controls. Chest trauma resulted in severe lung damage on both CT and histological analyses. Furthermore, severe inflammation with a systemic increase of IL-6 (p = 0.0305) and a local increase of IL-8 in BAL (p = 0.0009) was observed. The pO₂/FiO₂ ratio in trauma animals decreased over the observation period (p < 0.0001) but not in the sham group (p = 0.2967). Electrical Impedance Tomography (EIT) revealed differences between the traumatized and healthy lung (p < 0.0001). In conclusion, a clinically relevant, long-term model of blunt chest trauma with concomitant injuries has been developed. This reproducible model allows to examine local and systemic consequences of trauma and is valid for investigation of potential diagnostic or therapeutic options. In this context, EIT might represent a radiation-free method for bedside diagnostics.

Evaluation of Prehospital Blood Products to Attenuate Acute Coagulopathy of Trauma in a Model of Severe Injury and Shock in Anesthetized Pigs

Acute trauma coagulopathy (ATC) is seen in 30% to 40% of severely injured casualties. Early use of blood products attenuates ATC, but the timing for optimal effect is unknown. Emergent clinical practice has started prehospital deployment of blood products (combined packed red blood cells and fresh frozen plasma [PRBCs:FFP], and alternatively PRBCs alone), but this is associated with significant logistical burden and some clinical risk. It is therefore imperative to establish whether prehospital use of blood products is likely to confer benefit. This study compared the potential impact of prehospital resuscitation with (PRBCs:FFP 1:1 ratio) versus PRBCs alone versus 0.9% saline (standard of care) in a model of severe injury. Twenty-four terminally anesthetised Large White pigs received controlled soft tissue injury and controlled hemorrhage (35% blood volume) followed by a 30-min shock phase. The animals were allocated randomly to one of three treatment groups during a 60-min prehospital evacuation phase: hypotensive resuscitation (target systolic arterial pressure 80 mmHg) using either 0.9% saline (group 1, n = 9), PRBCs:FFP (group 2, n = 9), or PRBCs alone (group 3, n = 6). Following this phase, an in-hospital phase involving resuscitation to a normotensive target (110 mmHg systolic arterial blood pressure) using PRBCs:FFP was performed in all groups. There was no mortality in any group. A coagulopathy developed in group 1 (significant increase in clot initiation and dynamics shown by TEG [thromboelastography] R and K times) that persisted for 60 to 90 min into the in-hospital phase. The coagulopathy was significantly attenuated in groups 2 and 3 (P = 0.025 R time and P = 0.035 K time), which were not significantly different from each other. Finally, the volumes of resuscitation fluid required was significantly greater in group 1 compared with groups 2 and 3 (P = 0.0067) (2.8 ± 0.3 vs. 1.9 ± 0.2 and 1.8 ± 0.3 L, respectively). This difference was principally due to a greater volume of saline used in group 1 (P = 0.001). Prehospital PRBCs:FFP or PRBCs alone may therefore attenuate ATC. Furthermore, the amount of crystalloid may be reduced with potential benefit of reducing the extravasation effect and later tissue edema.

Effect of Negative Pressure Therapy on the Inflammatory Response of the Intestinal Microenvironment in a Porcine Septic Model

In a swine model of ischemia/reperfusion injury coupled with sepsis, we have previously shown attenuation of secondary organ injury and decreased mortality with negative pressure therapy (NPT). We hypothesized that NPT modulates the intestinal microenvironment by mediating the innate immune system. Sepsis was induced in 12 anesthetized female pigs. Group 1 (n = 6) was decompressed at 12 hrs after injury (T₁₂) and treated with standard of care (SOC), and group 2 (n = 6) with NPT for up to T₄₈. Immunoparalysis was evident as lymphocytopenia at T₂₄ in both groups; however, survival was improved in the NPT group versus SOC (Odds ratio = 4.0). The SOC group showed significant reduction in lymphocyte numbers compared to NPT group by T₄₈ (p < 0.05). The capacity of peritoneal fluid to stimulate a robust reactive oxygen species response in vitro was greater for the NPT group, peaking at T₂₄ for both M1 (p = 0.0197) and M2 macrophages (p = 0.085). Plasma elicited little if any effect which was confirmed by microarray analysis. In this septic swine model NPT appeared to modulate the intestinal microenvironment, facilitating an early robust, yet transient, host defense mediated by M1 and M2 macrophages. NPT may help overcome immunoparalysis that occurs during inflammatory response to septic injury.

Induced Hypothermia Does Not Harm Hemodynamics after Polytrauma: A Porcine Model

BACKGROUND

The deterioration of hemodynamics instantly endangers the patients' life after polytrauma. As accidental hypothermia frequently occurs in polytrauma, therapeutic hypothermia still displays an ambivalent role as the impact on the cardiopulmonary function is not yet fully understood.

METHODS

We have previously established a porcine polytrauma model including blunt chest trauma, penetrating abdominal trauma, and hemorrhagic shock. Therapeutic hypothermia (34°C) was induced for 3 hours. We documented cardiovascular parameters and basic respiratory parameters. Pigs were euthanized after 15.5 hours.

RESULTS

Our polytrauma porcine model displayed sufficient trauma impact. Resuscitation showed adequate restoration of hemodynamics. Induced hypothermia had neither harmful nor major positive effects on the animals' hemodynamics. Though heart rate significantly decreased and mixed venous oxygen saturation significantly increased during therapeutic hypothermia. Mean arterial blood pressure, central venous pressure, pulmonary arterial pressure, and wedge pressure showed no significant differences comparing normothermic trauma and hypothermic trauma pigs during hypothermia.

CONCLUSIONS

Induced hypothermia after polytrauma is feasible. No major harmful effects on hemodynamics were observed. Therapeutic hypothermia revealed hints for tissue protective impact. But the chosen length for therapeutic hypothermia was too short. Nevertheless, therapeutic hypothermia might be a useful tool for intensive care after polytrauma. Future studies should extend therapeutic hypothermia.

Fibrinolysis shutdown phenotype masks changes in rodent coagulation in tissue injury versus hemorrhagic shock

INTRODUCTION

Systemic hyperfibrinolysis (accelerated clot degradation) and fibrinolysis shutdown (impaired clot degradation) are associated with increased mortality compared with physiologic fibrinolysis after trauma. Animal models have not reproduced these changes. We hypothesize rodents have a shutdown phenotype that require an exogenous profibrinolytic to differentiate mechanisms that promote or inhibit fibrinolysis.

METHODS

Fibrinolysis resistance was assessed by thrombelastography (TEG) using exogenous tissue plasminogen activator (tPA) titrations in whole blood. There were 3 experimental groups: (1) tissue injury (laparotomy/bowel crush), (2) shock (hemorrhage to mean arterial pressure of 20 mmHg), and (3) control (arterial cannulation and tracheostomy). Baseline and 30-minute postintervention blood samples were collected, and assayed with TEG challenged with taurocholic acid (TUCA).

RESULTS

Rats were resistant to exogenous tPA; the percent clot remaining 30 minutes after maximum amplitude (CL30) at 150 ng/mL (P = .511) and 300 ng/mL (P = .931) was similar to baseline, whereas 600 ng/mL (P = .046) provoked fibrinolysis. Using the TUCA challenge, the percent change in CL30 from baseline was increased in tissue injury compared with control (P = .048.), whereas CL30 decreased in shock versus control (P = .048). tPA increased in the shock group compared with tissue injury (P = .009) and control (P = .012).

CONCLUSION

Rats have an innate fibrinolysis shutdown phenotype. The TEG TUCA challenge is capable of differentiating changes in clot stability with rats undergoing different procedures. Tissue injury inhibits fibrinolysis, whereas shock promotes tPA-mediated fibrinolysis.

Reconstitution fluid type does not affect pulmonary inflammation or DNA damage following infusion of lyophilized plasma

BACKGROUND

Dysfunctional inflammation following traumatic hemorrhage can lead to multiple-organ failure and death. In our polytrauma swine model, lyophilized plasma (LP) reconstituted with sterile water and ascorbic acid suppressed systemic inflammation and attenuated DNA damage. However, it remains unknown whether the inflammatory response is affected by the type of fluid used to reconstitute LP. We hypothesized that common resuscitation fluids such as normal saline (LP-NS), lactated Ringer's solution (LP-LR), Hextend (LP-HX), or sterile water (LP-SW) would yield similar inflammation profiles and DNA damage following LP reconstitution and transfusion.

METHODS

This was a randomized, prospective, blinded animal study. LP was reconstituted to 50% of original volume with NS, LR, HX, or SW buffered with 15-mM ascorbic acid. Forty swine were subjected to a validated model of polytrauma, hemorrhagic shock, and Grade V liver injury and resuscitated with LP. Serum interleukin 6 (IL-6), IL-10, plasma C-reactive protein, and 8-hydroxy-2-deoxyguanosine concentrations were assessed for systemic inflammation and DNA damage at baseline, 2 hours, and 4 hours following liver injury. Lung inflammation was evaluated by Real Time Polymerize Chain Reaction (RT-PCR).

RESULTS

Reconstituted LP pH was similar between groups before resuscitation. IL-6 and IL-10 increased at 2 hours and 4 hours compared with baseline in all groups (p < 0.017). DNA damage increased at 2 hours and 4 hours compared with baseline and from 2 hours to 4 hours in the LP-NS, LP-LR, and LP-SW groups (all p < 0.017). Animals resuscitated with LP-HX not only demonstrated increased DNA damage at 4 hours versus baseline but also had the lowest C-reactive protein level at 2 hours and 4-hours (p < 0.017). Overall, differences between groups were similar for DNA damage and lung inflammation.

CONCLUSION

Reconstitution fluid type does not affect inflammatory cytokine profiles or DNA damage following LP transfusion in this swine polytrauma model. Based on universal availability, these data suggest that sterile water is the most logical choice for LP reconstitution in humans.

LEVEL OF EVIDENCE

Prognostic, level II.

Non-osteotomy and osteotomy large animal fracture models in orthopedic trauma research

Large animal fracture models are important in the field of orthopedic trauma research. New implants are tested in animals before being implanted into humans. Large animals like sheep or swine often are more properly to simulate conditions in humans, e.g. biomechanical demands, compared to rodents. Cited articles mainly analyze shock or fracture healing. Both osteotomy and non-osteotomy fracture models have been used in the past. However, comparative studies are rare and clear recommendation when to use which model are missing. This review will summarize large animal fracture models putting special emphasis on non-osteotomy fracture models.

Comparison of arterial and venous whole blood clot initiation, formation, and strength by thromboelastography in anesthetized swine

Thromboelastography (TEG) analysis was used to determine if differences exist between venous and arterial samples in anesthetized swine, using identical sampling techniques for each of the samples. We hypothesized that TEG parameters would not differ between native whole blood venous and arterial samples. Thirty male Landrace swines were included in the study. Both the femoral artery and vein were catheterized using standard cut-down techniques and with identically sized catheters to rule out any catheter size effects on the results. Standard TEG parameters for native whole venous and arterial blood samples (r, K, α, MA, G, and coagulation index) were measured or calculated, and t-test or Mann-Whitney rank-sum test used for comparison when appropriate. Significant differences were detected for r (venous < arterial), K (venous < arterial), α (venous > arterial), and coagulation index (venous > arterial) TEG parameters. No significant differences were measured for MA or G. These differences are important, especially when temporal changes in TEG are utilized to monitor patient stability and fluid therapy protocols using trends in coagulation properties. Taken together, these results suggest that clots are more likely to form at a faster rate in venous samples compared to arterial samples, but the overall clot strength does not differ. Therefore, if TEG analysis is being used to monitor coagulation profiles in a patient, care should be taken to use the same site and technique if results are to be used for comparative purposes.

Relevance of induced and accidental hypothermia after trauma-haemorrhage-what do we know from experimental models in pigs?

Recent experimental research has either focused on the role of accidental hypothermia as part of the lethal triad after trauma or tried to elucidate the effects of therapeutically induced hypothermia on the posttraumatic course. Induced hypothermia seems to reduce the mortality in experimental models of trauma-haemorrhage. As potential mechanisms, a decrease of cellular metabolism, beneficial effects on haemodynamic function and an attenuation of the inflammatory response have been described. However, negative side effects of hypothermia have to be considered, such as impairment of the coagulatory function and immunosuppressive effects. Furthermore, the optimal strategy for the induction of hypothermia (magnitude, duration, timing, cooling rate, etc.) and subsequent rewarming remains unclear. Nevertheless, this piece of information is essential before considering hypothermia as a treatment strategy for severely injured patients. This review aims to elaborate the differences between accidental and induced hypothermia and to summarize the current knowledge of the potential therapeutic use of induced hypothermia suggested in porcine models of trauma-haemorrhage.

Comparison of the hemostatic efficacy of low-volume lyophilized plasma reconstituted using sterile water, lactated Ringer's, normal saline, and Hextend solutions

BACKGROUND

Low-volume ascorbic acid-buffered reconstituted lyophilized plasma (LP) provides logistic advantages, reduces the risks for large-volume resuscitation, modulates inflammation, and is equally effective for hemostatic resuscitation as full-volume LP. We compared the physiologic effects of resuscitation using LP reconstituted with sterile water (LP-SW), lactated Ringer's solution (LP-LR), normal saline (LP-NS), and Hextend (LP-Hx).

METHODS

Plasma was collected from swine, lyophilized, and then reconstituted into four test solutions: LP-SW, LP-LR, LP-NS, or LP-Hx. Forty swine were anesthetized and subjected to a validated model of polytrauma and hemorrhagic shock (including a Grade V liver injury), then randomized to receive one of the four test solutions. Physiologic parameters, blood loss, lactate, and hematocrit were followed up. Coagulation status was evaluated using thrombelastography. Inflammatory mediator expression was evaluated by multiplex serum assay.

RESULTS

Forty animals were included in the study (10 animals per group). One animal died following LP-Hx resuscitation. There was less blood loss in the LP-SW and LP-LR groups compared with the LP-NS and LP-Hx groups (p < 0.05). The LP-SW group exhibited less early coagulopathic changes by thrombelastography, and the LP-Hx group had persistently elevated international normalized ratios at the end of the study period (p < 0.05). Serum interleukin 6 was lower after 4 hours in the LP-SW group compared with LP-NS (p < 0.05).

CONCLUSION

Resuscitation using low-volume LP-SW and LP-LR buffered with ascorbic acid confers an anti-inflammatory benefit and results in less blood loss. Sterile water is a safe, cost-effective, and universally available fluid for creating a low-volume hemostatic LP resuscitation solution.

A time course study of acute traumatic coagulopathy prior to resuscitation: from hypercoagulation to hypocoagulation caused by hypoperfusion?

INTRODUCTION

Coagulopathy after sever injury predicts the requirements of blood products, organ failure and mortality in traumatic patients. The early onset and complexity of traumatic coagulopathy preclude the understanding the underlying mechanism. The aim of the study is to characterize the early coagulation alteration in a swine model with multi-trauma and shock.

METHODS

Twelve pigs were subjected to multi-trauma (femur fracture, laparotomy, 10 cm intestine resection and grade III injury of liver) and hemorrhaged to a mean arterial pressure (MAP) of 40 mmHg. Physiologic parameters and coagulation variables (prothrombin time (PT), international normalized ratio (INR), fibrinogen, antithrombin-III (AT-III) activity, D-dimer and thromboelastography (TEG)) were measured after instrumentation (baseline), 5 min after multi-trauma (after trauma), 10 min (early shock) and 40 min (late shock) after hemorrhage. A group of 6 instrumented pigs were used as control.

RESULTS

Multi-trauma and hemorrhage caused significant increase of base excess (BE) and lactate (p<0.05). PT shortened after multi-trauma but increased significantly at late shock (p<0.05). Fibrinogen reduced greatly after trauma and at early shock (p<0.05), while remained stable afterwards. AT-III activity decreased throughout the experiment. Reaction time (R) shortened after trauma and at early shock (both p<0.05). Maximal amplitude (MA) decreased significantly during the shock period.

CONCLUSION

After traumatic hemorrhagic shock, hypercoagulation turned into hypocoagulation in a short period, which was probably caused by hypoperfusion.

Hyperosmolar reconstituted lyophilized plasma is an effective low-volume hemostatic resuscitation fluid for trauma

BACKGROUND

We performed this study to optimize reconstituted lyophilized plasma (LP) into a minimal volume fluid that provides effective hemostatic resuscitation for trauma while minimizing logistical limitations.

METHODS

We performed a prospective, blinded animal study. Plasma was lyophilized following whole blood collection from anesthetized swine. The minimal volume needed for reconstitution was determined, and this solution was evaluated for safe infusion into the swine. Reconstituted LP was analyzed for electrolyte content, osmolarity, and coagulation factor activity. Twenty swine were anesthetized and subjected to a validated model of polytrauma and hemorrhagic shock (including a Grade V liver injury), then randomized to resuscitation with LP reconstituted to either 100% of the original plasma volume (100%LP) or the minimal volume LP fluid. Physiologic data were monitored, and blood loss and hematocrit were measured. Coagulation status was evaluated using thrombelastography.

RESULTS

The minimal volume of reconstituted LP safe for infusion in swine was 50% of the original plasma volume (50%LP). The 50%LP had higher electrolyte concentrations, osmolarity, and increased coagulation factor activity levels by volume compared with 100%LP (p < 0.05). Blood loss, hematocrit, mean arterial pressure, and heart rate did not differ between animals receiving 100%LP (n = 10) or 50%LP (n = 10) at any time point (p > 0.05). International normalized ratio and thrombelastography parameters were not different between groups (R time, α angle, or maximal amplitude, p > 0.05).

CONCLUSION

Resuscitation with 50%LP fluid was well tolerated and equally effective compared with 100%LP, with respect to physiologic and hemostatic properties. The smaller volume of fluid necessary to reconstitute hypertonic LP makes it logistically superior to 100%LP for first responders and may reduce adverse effects of large-volume resuscitation.

Induced hypothermia does not impair coagulation system in a swine multiple trauma model

BACKGROUND

Accidental hypothermia, acidosis, and coagulopathy represent the lethal triad in severely injured patients. Therapeutic hypothermia however is commonly used in transplantations, cardiac and neurosurgical surgery, or after cardiac arrest. However, the effects of therapeutic hypothermia on the coagulation system following multiple trauma need to be elucidated.

METHODS

In a porcine model of multiple trauma including blunt chest injury, liver laceration, and hemorrhagic shock followed by fluid resuscitation, the influence of therapeutic hypothermia on coagulation was evaluated. A total of 40 pigs were randomly assigned to sham (only anesthesia) or trauma groups receiving either hypothermia or normothermia. Each group consisted of 10 pigs. Analyzed parameters were cell count (red blood cells, platelets), pH, prothrombin time (PT), fibrinogen concentration, and analysis with ROTEM and Multiplate.

RESULTS

Trauma and consecutive fluid resuscitation resulted in impaired coagulation parameters (cell count, pH, PT, fibrinogen, ROTEM, and platelet function). During hypothermia, coagulation parameters measured at 37°C, such as PT, fibrinogen, thrombelastometry measurements, and platelet function, showed no significant differences between normothermic and hypothermic animals in both trauma groups. Additional analyses of thrombelastometry at 34°C during hypothermia showed significant differences for clotting time and clot formation time but not for maximum clot firmness. We were not able to detect macroscopic or petechial bleeding in both trauma groups.

CONCLUSION

Based on the results of the present study we suggest that mild hypothermia can be safely performed after stabilization following major trauma. Mild hypothermia has effects on the coagulation system but does not aggravate trauma-induced coagulopathy in our model. Before hypothermic treatment can be performed in the clinical setting, additional experiments with prolonged and deeper hypothermia to exclude detrimental effects are required.

A pilot study of the use of kaolin-impregnated gauze (Combat Gauze) for packing high-grade hepatic injuries in a hypothermic coagulopathic swine model

BACKGROUND

Severe hepatic injuries may be highly lethal, and perihepatic packing remains the mainstay of treatment. This is not always successful, particularly in the setting of hypothermia and coagulopathy. Kaolin-impregnated Combat Gauze (CG) is an effective hemostatic dressing used primarily to treat external wounds. The objective of this study was to determine the ability of CG to control severe hemorrhage in hypothermic, coagulopathic swine with a high-grade hepatic injury.

METHODS

Anesthetized animals underwent splenectomy and were cooled to 32°C while undergoing a 60% exchange transfusion with Hextend. A grade V liver injury was created in the left middle hepatic lobe. Animals were allowed to freely bleed for 30 s and then randomized to treatment with CG or plain gauze laparotomy pads (PG) applied to the injury site. Animals were then resuscitated with warmed Hextend.

RESULTS

There was no difference between groups in preinjury hemodynamic or laboratory values. Animals packed with CG had less blood loss when compared with standard packing (CG = 25 mL/kg versus PG = 58 mL/kg, P = 0.05). There was a trend towards lower hetastarch resuscitation requirements in the CG group (CG = 7 mL/kg versus PG = 44 mL/kg, P = 0.06) but no statistically significant difference in mortality (CG = 13% versus PG = 50%, P = 0.11). Histology of the injury sites revealed more adherent clot in the CG group, but no inflammation, tissue necrosis, or residual material.

CONCLUSION

In pigs with severe hepatic injury, Combat Gauze reduced blood loss and resuscitation requirements when compared with plain laparotomy pads. Combat Gauze may be safe and effective for use on severe liver injuries.

The microcirculation: linking trauma and coagulopathy

Survival after severe traumatic shock can be complicated by a number of pathophysiologic processes that ensue after the initial trauma. One of these is trauma-induced coagulopathy (TIC) whose onset may occur before initial fluid resuscitation. The pathogenesis of TIC has not yet been fully elaborated, but evolving evidence appears to link severe tissue hypoxia and damage to the endothelium as key factors, which evolve into measurable structural and biochemical changes of the endothelium resulting in a coagulopathic state. This paper will provide a general review of these linkages and identify knowledge gaps as well as suggest new approaches and areas of investigation, which may both limit the development of TIC as well as produce insights into its pathophysiology. A better understanding of these issues will be necessary in order to advance the practice of remote damage control resuscitation.

The use of lyophilized plasma in a severe multi-injury pig model

BACKGROUND

Shock and severe tissue injury lead to an endogenous coagulopathy mediated by activation of Protein C and hyperfibrinolysis known as acute traumatic coagulopathy. Together, hemodilution, acidosis, inflammation, and hypothermia result in a global trauma-induced coagulopathy. Coagulopathy in trauma is associated with mortality. Early and effective hemostatic resuscitation is critical in restoring perfusion, correcting coagulopathy, and saving lives in exsanguinating trauma. Lyophilized plasma (LP) provides a logistically superior alternative to fresh frozen plasma (FFP).

STUDY DESIGN AND METHODS

Plasma was lyophilized following whole blood collection from anesthetized swine. A series of studies were performed using anesthetized swine subjected to a validated model of polytrauma and hemorrhagic shock including a Grade V liver injury. Animals were randomized to resuscitation using reconstituted LP fluids. Physiologic data and blood loss were measured. Coagulation status and inflammatory mediators were evaluated.

RESULTS

Full volume reconstituted LP (100%LP) retains on average 86% coagulation factor activity compared to fresh plasma and when used in 1:1 ratios with red blood cells demonstrated superior hemostatic efficacy compared to FFP. Hypertonic LP reconstituted using 50% of the original plasma volume (50%LP) had higher coagulation factor concentrations, was well tolerated in swine, and equally effective compared to 100%LP with respect to physiologic and hemostatic properties. Buffering with ascorbic acid resulted in significant reductions in serum levels of tumor necrosis factor alpha and interleukin-6.

CONCLUSION

By minimizing the volume of reconstituted LP and optimizing its anti-inflammatory properties, an LP resuscitation fluid may be created to provide effective hemostatic resuscitation with superior logistical properties.

Animal models of trauma-induced coagulopathy

Resurgent study of trauma-induced coagulopathy (TIC) has delivered considerable improvements in survival after injury. Robust, valid and clinically relevant experimental models of TIC are essential to support the evolution of our knowledge and management of this condition. The aims of this study were to identify and analyze contemporary animal models of TIC with regard to their ability to accurately characterize known mechanisms of coagulopathy and/or to test the efficacy of therapeutic agents. A literature review was performed. Structured search of the indexed online database MEDLINE/PubMed in July 2010 identified 43 relevant articles containing 23 distinct animal models of TIC. The main aim of 26 studies was to test a therapeutic and the other 17 were conducted to investigate pathophysiology. A preponderance of porcine models was identified. Three new models demonstrating an endogenous acute traumatic coagulopathy (ATC) have offered new insights into the pathophysiology of TIC. Independent or combined effects of induced hypothermia and metabolic acidosis have been extensively evaluated. Recently, a pig model of TIC has been developed that features all major etiologies of TIC, although not in correct chronological order. This review identifies a general lack of experimental research to keep pace with clinical developments. Tissue injury and hemorrhagic shock are fundamental initiating events that prime the hemostatic system for subsequent iatrogenic insults. New animal models utilizing a variety of species that accurately simulate the natural clinical trajectory of trauma are urgently needed.

Lyophilized plasma reconstituted with ascorbic acid suppresses inflammation and oxidative DNA damage

BACKGROUND

Lyophilized plasma (LP) has been shown to be as effective as fresh frozen plasma (FFP) for resuscitation in polytrauma and hemorrhagic shock. LP reconstituted with ascorbic acid is associated with suppression of cytokines when compared with fresh frozen plasma. We aimed to determine the effect of using alternate LP reconstitution acids on physiologic parameters, blood loss, coagulation, oxidative DNA damage, and proinflammatory cytokines in a polytrauma and hemorrhagic shock model.

METHODS

Thirty swine were anesthetized, subjected to polytrauma, hemorrhagic shock, and randomized to resuscitation with LP-ascorbic acid (AA), LP-citric acid (CA), or LP-hydrochloric acid (HCL). Physiologic data were continuously monitored, blood loss measured, and serum collected at baseline, 2 hours, and 4 hours for enzyme-linked immunosorbent assays. Measured 8-OH-2'-deoxyguanosine (8-OHdG) was a biomarker of oxidative DNA damage.

RESULTS

No differences were observed in physiologic measures, blood loss, or coagulation parameters. Interleukin-6 increased over time for all groups, but at 2 hours, the concentration in AA (median [minimum, maximum]: 113 ng/mL [0, 244]) was lower compared with CA (181 ng/mL [69, 314], p = 0.01) and HCL (192 ng/mL [41, 310], p = 0.03). Comparing 4 hours to baseline, a significant increase in oxidative DNA damage was observed in CA (22.9 ng/mL [16.3, 34.3] vs. 15.6 ng/mL [13.6, 26.7], p = 0.03) and HCL (19.6 ng/mL [15.7, 56.7] vs. 15.8 ng/mL [11.6, 21.4], p = 0.01) but not in AA (17.9 ng/mL [12.6, 26.9] vs. 17.1 ng/mL [11.8, 18.4], p = 0.24).

CONCLUSIONS

Resuscitation with AA results in decreased interleukin-6 expression and oxidative DNA damage compared with CA and HCL.

A porcine model for evaluating the management of noncompressible torso hemorrhage

BACKGROUND

Noncompressible hemorrhage from central vascular injuries remains the leading cause of preventable death in modern combat. This report introduces a large animal model of noncompressible torso hemorrhage, which permits assessment of the various approaches to this problem.

METHODS

Yorkshire swine were anesthetized and monitoring devices for central aortic pressure, carotid flow, and intracerebral and transcutaneous brain oximetry were applied. Class IV hemorrhagic shock was induced through an iliac arterial injury and animals were subjected to different vascular control methods including thoracic aortic clamping, supraceliac aortic clamping, direct vascular control, and proximal endovascular balloon occlusion. After vascular control, the injury was shunted, and damage control resuscitation was continued. Serum markers, intravenous fluid volumes, and vasopressor requirements were tracked over a subsequent resuscitation period. Postmortem tissue analysis was performed to compare levels of acute ischemic injury between groups.

RESULTS

The protocol for animal preparation, hemorrhage volume, open surgical technique, and posthemorrhage resuscitation was developed using four animals. The endovascular approach was developed using two additional animals. After model development, treatment animals subsequently underwent noncompressible hemorrhage with thoracic aortic clamping, supraceliac aortic clamping, direct vascular control, and endovascular aortic occlusion. Premature death occurred in one animal in the direct vascular control group.

CONCLUSION

This study presents a large animal model of class IV hemorrhagic shock from noncompressible hemorrhage, which permits comparison of various vascular control methods to address this challenging problem. Future studies using this model as the standard will allow further development of strategies for the management of noncompressible hemorrhage.

Lyophilized plasma with ascorbic acid decreases inflammation in hemorrhagic shock

BACKGROUND

Delivery of a high ratio of plasma to packed red blood cells to patients who require massive transfusion is associated with improved survival. Hemorrhagic shock causes increased production of pro-inflammatory cytokines. These are associated with late morbidity and mortality. The use of fresh frozen plasma makes high ratio resuscitation logistically difficult and does not address dysfunctional inflammation. Lyophilized plasma (LP) is a stable powdered form of plasma that is both safe and easily reconstituted. Previous work demonstrated that LP reconstituted with ascorbic acid (AA) decreased inflammation. Whether the reduction of inflammation was associated with LP or the AA is unknown.

METHODS

Thirty female swine were anesthetized and subjected to a multisystem combat relevant model consisting of femur fracture, controlled hemorrhage, and hypothermia. A standardized grade V liver injury was made and the animals were randomly assigned to receive LP reconstituted with AA, citric acid (CA), or hydrochloric acid (HCl). Blood was drawn at baseline and at 2 hours and 4 hours for interleukin (IL)-6, IL-8, and tumor necrosis factor-α serum concentrations measured by enzyme-linked immunosorbent assay. Lung tissue was harvested and processed for gene expression before euthanizing the animals.

RESULTS

No differences were observed in mortality, baseline cytokine serum concentration, or gene expression. Enzyme-linked immunosorbent assay demonstrated that IL-6 concentration increased over time for all groups (p < 0.05), but less so at 2 hours in the AA group compared with CA and HCl.

CONCLUSION

In this animal model of trauma, hemorrhage and resuscitation, AA decreases IL-6 expression relative to CA and HCl. These findings confirm previous work from our laboratory and suggest that AA is responsible for suppression of dysfunctional inflammation in this model.

Development and testing of low-volume hyperoncotic, hyperosmotic spray-dried plasma for the treatment of trauma-associated coagulopathy

BACKGROUND

Trauma-associated coagulopathy carries an extremely high mortality. Fresh-frozen plasma (FFP) is the mainstay of treatment; however, its availability in the battlefield is limited. We have already shown that lyophilized, freeze-dried plasma (FDP) reconstituted in its original volume can reverse trauma-associated coagulopathy. To enhance the logistical advantage (lower volume and weight), we developed and tested a hyperoncotic, hyperosmotic spray-dried plasma (SDP) product in a multiple injuries/hemorrhagic shock swine model.

METHODS

Plasma separated from fresh porcine blood was stored as FFP or preserved as FDP and SDP. In in vitro testing, SDP was reconstituted in distilled water that was either equal (1 × SDP) or one-third (3 × SDP) the original volume of FFP. Analysis included measurements of prothrombin time (PT), partial thromboplastin time (PTT), fibrinogen levels, and activity of selected clotting factors. In in vivo testing, swine were subjected to multiple injuries (femur fracture and grade V liver injury) and hemorrhagic shock (60% arterial hemorrhage, with the "lethal triad" of acidosis, coagulopathy, and hypothermia) and were treated with FFP, FDP, or 3 × SDP (n=4-5/group). Coagulation profiles (PT, PTT, and thromboelastography) were measured at baseline, post-shock, post-crystalloid, treatment (M0), and during 4 hours of monitoring (M1-4).

RESULTS

In vitro testing revealed that clotting factors were preserved after spray drying. The coagulation profiles of FFP and 1 × SDP were similar, with 3 × SDP showing a prolonged PT/PTT. Multiple injuries/hemorrhagic shock produced significant coagulopathy, and 3 × SDP infusion was as effective as FFP and FDP in reversing it.

CONCLUSION

Plasma can be spray dried and reconstituted to one-third of its original volume without compromising the coagulation properties in vivo. This shelf-stable, low-volume, hyperoncotic, hyperosmotic plasma is a logistically attractive option for the treatment of trauma-associated coagulopathy in austere environments, such as a battlefield.

Experimental trauma models: an update

Treatment of polytrauma patients remains a medical as well as socioeconomic challenge. Although diagnostics and therapy improved during the last decades, multiple injuries are still the major cause of fatalities in patients below 45 years of age. Organ dysfunction and organ failure are major complications in patients with major injuries and contribute to mortality during the clinical course. Profound understanding of the systemic pathophysiological response is crucial for innovative therapeutic approaches. Therefore, experimental studies in various animal models are necessary. This review is aimed at providing detailed information of common trauma models in small as well as in large animals.

Preliminary study of the effects of smectite granules (WoundStat) on vascular repair and wound healing in a swine survival model

BACKGROUND

WoundStat (WS) (TraumaCure, Bethesda, MD) is a topical hemostatic agent that effectively stops severe hemorrhage in animal models. To the best of our knowledge, no survival study has been conducted to ensure long-term product safety. We evaluated vascular patency and tissue responses to WS in a swine femoral artery injury model with survival up to 5 weeks.

METHODS

Anesthetized swine received a standardized femoral artery injury with free hemorrhage for 45 seconds followed by WS application. One hour after application, the WS was removed, the wound copiously irrigated, and the artery repaired using a vein patch. Six groups of three animals received WS and were killed either immediately after surgery or at weekly intervals up to 5 weeks. Three control animals were treated with gauze packing and direct pressure followed by identical vascular repair and survival for 1 week. At the time of killing, angiograms were performed, and tissue was collected for histopathology.

RESULTS

Hemostasis was complete in all WS animals. All animals survived the procedure, and there were no clinically evident postoperative complications. Vascular repairs were angiographically patent in 15 of 18 animals (83%) receiving WS. Histopathologic examination of WS animals revealed severe diffuse fibrogranulomatous inflammation, early endothelial degeneration with subsequent intimal hyperplasia, moderate myocyte necrosis, and fibrogranulomatous nerve entrapment with axonal degeneration.

CONCLUSION

Although an effective hemostatic agent, WS use was associated with a substantial local inflammatory response and neurovascular changes up to 5 weeks postinjury.

Red blood cells accelerate the onset of clot formation in polytrauma and hemorrhagic shock

BACKGROUND

Hemorrhage and coagulopathy are major contributors to death after trauma. The contribution of red blood cells (RBCs) in correcting coagulopathy is poorly understood. Current methods of measuring coagulopathy may fail to accurately characterize in vivo clotting. We aimed to determine the effect of RBCs on clotting parameters by comparing resuscitation regimens containing RBCs and plasma with those containing plasma alone.

METHODS

Thirty-two Yorkshire swine were anesthetized, subjected to a complex model of polytrauma and hemorrhagic shock, and resuscitated with either fresh frozen plasma, lyophilized plasma (LP), or 1:1 ratios of fresh frozen plasma:packed RBC (PRBC) or LP:PRBC. Activated clotting time, prothrombin time, partial thromboplastin time, and thrombelastography (TEG) were performed at 1 hour, 2 hours, 3 hours, and 4 hours after resuscitation.

RESULTS

Animals treated with 1:1 LP:PRBC had less blood loss than the other groups (p < 0.05). The activated clotting time was shorter in the 1:1 groups when compared with the pure plasma groups at all time points (p < 0.05). The 1:1 groups had shorter TEG R times (time to onset of clotting) at 1 hour, 3 hours, and 4 hours compared with pure plasma groups (p < 0.05). Other TEG parameters did not differ between groups. Partial thromboplastin time was shorter in the pure plasma groups than the 1:1 groups at all time points (p < 0.05).

CONCLUSIONS

Whole blood assays reveal that RBCs accelerate the onset of clot formation. Coagulation assays using spun plasma underestimate the effect of RBCs on clotting and do not completely characterize clot formation.

Systemic central venous oxygen saturation is associated with clot strength during traumatic hemorrhagic shock: A preclinical observational model

Background

Clot strength by Thrombelastography (TEG) is associated with mortality during trauma and has been linked to severity of tissue hypoperfusion. However, the optimal method for monitoring this important relationship remains undefined. We hypothesize that oxygen transport measurements will be associated with clot strength during traumatic shock, and test this hypothesis using a swine model of controlled traumatic shock.

Methods

N = 33 swine were subjected to femur fracture and hemorrhagic shock by controlled arterial bleeding to a predetermined level of oxygen debt measured by continuous indirect calorimetry. Hemodynamics, oxygen consumption, systemic central venous oxygenation (ScvO₂), base excess, lactate, and clot maximal amplitude by TEG (TEG-MA) as clot strength were measured at baseline and again when oxygen debt = 80 ml/kg during shock. Oxygen transport and metabolic markers of tissue perfusion were then evaluated for significant associations with TEG-MA. Forward stepwise selection was then used to create regression models identifying the strongest associations between oxygen transport and TEG-MA independent of other known determinants of clot strength.

Results

Multiple markers of tissue perfusion, oxygen transport, and TEG-MA were all significantly altered during shock compared to baseline measurements (p < 0.05). However, only ScvO₂ demonstrated a strong bivariate association with TEG-MA measured during shock (R = 0.7, p < 0.001). ScvO₂ measured during shock was also selected by forward stepwise selection as an important covariate in linear regression models of TEG-MA after adjusting for the covariates fibrinogen, pH, platelet count, and hematocrit (Whole model R² = 0.99, p ≤ 0.032).

Conclusions

Among multiple measurements of oxygen transport, only ScvO₂ was found to retain a significant association with TEG-MA during shock after adjusting for multiple covariates. ScvO₂ should be further studied for its utility as a clinical marker of both tissue hypoxia and clot formation during traumatic shock.

Rabbit model of uncontrolled hemorrhagic shock and hypotensive resuscitation

Clinically relevant animal models capable of simulating traumatic hemorrhagic shock are needed. We developed a hemorrhagic shock model with male New Zealand rabbits (2200-2800 g, 60-70 days old) that simulates the pre-hospital and acute care of a penetrating trauma victim in an urban scenario using current resuscitation strategies. A laparotomy was performed to reproduce tissue trauma and an aortic injury was created using a standardized single puncture to the left side of the infrarenal aorta to induce hemorrhagic shock similar to a penetrating mechanism. A 15-min interval was used to simulate the arrival of pre-hospital care. Fluid resuscitation was then applied using two regimens: normotensive resuscitation to achieve baseline mean arterial blood pressure (MAP, 10 animals) and hypotensive resuscitation at 60% of baseline MAP (10 animals). Another 10 animals were sham operated. The total time of the experiment was 85 min, reproducing scene, transport and emergency room times. Intra-abdominal blood loss was significantly greater in animals that underwent normotensive resuscitation compared to hypotensive resuscitation (17.1 ± 2.0 vs 8.0 ± 1.5 mL/kg). Antithrombin levels decreased significantly in normotensive resuscitated animals compared to baseline (102 ± 2.0 vs 59 ± 4.1%), sham (95 ± 2.8 vs 59 ± 4.1%), and hypotensive resuscitated animals (98 ± 7.8 vs 59 ± 4.1%). Evidence of re-bleeding was also noted in the normotensive resuscitation group. A hypotensive resuscitation regimen resulted in decreased blood loss in a clinically relevant small animal model capable of reproducing hemorrhagic shock caused by a penetrating mechanism.

Recombinant myostatin (GDF-8) propeptide enhances the repair and regeneration of both muscle and bone in a model of deep penetrant musculoskeletal injury

BACKGROUND

Myostatin (GDF-8) is known as a potent inhibitor of muscle growth and development, and myostatin is also expressed early in the fracture healing process. The purpose of this study was to test the hypothesis that a new myostatin inhibitor, a recombinant myostatin propeptide, can enhance the repair and regeneration of both muscle and bone in cases of deep penetrant injury.

METHODS

We used a fibula osteotomy model with associated damage to lateral compartment muscles (fibularis longus and brevis) in mice to test the hypothesis that blocking active myostatin with systemic injections of a recombinant myostatin propeptide would improve muscle and bone repair. Mice were assigned to two treatment groups after undergoing a fibula osteotomy: those receiving either vehicle (saline) or recombinant myostatin propeptide (20 mg/kg). Mice received one injection on the day of surgery, another injection 5 days after surgery, and a third injection 10 days after surgery. Mice were killed 15 days after the osteotomy procedure. Bone repair was assessed using microcomputed tomography (micro-CT) and histologic evaluation of the fracture callus. Muscle healing was assessed using Masson trichrome staining of the injury site, and image analysis was used to quantify the degree of fibrosis and muscle regeneration.

RESULTS

Three propeptide injections over a period of 15 days increased body mass by 7% and increased muscle mass by almost 20% (p < 0.001). Micro-CT analysis of the osteotomy site shows that by 15 days postosteotomy, bony callus tissue was observed bridging the osteotomy gap in 80% of the propeptide-treated mice but only 40% of the control (vehicle)-treated mice (p < 0.01). Micro-CT quantification shows that bone volume of the fracture callus was increased by ∼ 30% (p < 0.05) with propeptide treatment, and the increase in bone volume was accompanied by a significant increase in cartilage area (p = 0.01). Propeptide treatment significantly decreased the fraction of fibrous tissue in the wound site and increased the fraction of muscle relative to fibrous tissue by 20% (p < 0.01).

CONCLUSIONS

Blocking myostatin signaling in the injured limb improves fracture healing and enhances muscle regeneration. These data suggest that myostatin inhibitors may be effective for improving wound repair in cases of orthopaedic trauma and extremity injury.

Testing of blood products in a polytrauma model: results of a multi-institutional randomized preclinical trial

INTRODUCTION

Trauma-induced coagulopathy, acidosis, and hypothermia form a "lethal triad" that is difficult to treat and is associated with extremely high mortality. This study was performed at three academic centers to evaluate whether resuscitation with blood components could reverse the coagulopathy in a complex polytrauma model.

METHODS

Yorkshire swine (40 +/- 5 kg) were subjected to a three-phase protocol: (a) "Prehospital" phase = femur fracture, hemorrhage (60% blood volume), and 30 minutes shock + infusion of saline (3x shed blood) + induction of hypothermia (33 degrees C); (b) "Early hospital" phase = grade V liver injury; and (c) "Operative" phase= liver packing. After liver packing, the animals (n = 60) were randomized to the following groups: (1) Sham-instrumentation and anesthesia without hemorrhage/injuries, (2) fresh whole blood (FWB), (3) 6% hetastarch (Hextend), (4) fresh frozen plasma/packed RBCs in 1:1 ratio (1:1 FFP/PRBC), and (5) FFP alone. Treatment volumes were equal to the volume of shed blood. Hemodynamic and physiologic parameters and coagulation profile (thrombelastography, prothrombin time, activated partial thromboplastin time, international normalized ratio, and platelets) were monitored during the experiment and for 4 hours posttreatment.

RESULTS

At the end of prehospital phase, animals had developed significant acidosis (lactate >5 mmol/L and base deficit >9 mmol/L) and coagulopathy. Posttreatment mortality rates were 85% and 0% for the Hextend and blood component treated groups, respectively (p < 0.05). Hemodynamic parameters and survival rates were similar in groups that were treated with blood products (FWB, FFP, and FFP:PRBC). Animals treated with FFP and Hextend had significant anemia compared with the groups that received red blood cells (FWB and FFP:PRBC). Treatment with FFP and FFP:PRBC corrected the coagulopathy as effectively as FWB, whereas Hextend treatment worsened coagulopathy.

CONCLUSIONS

In this reproducible model, we have shown that trauma-associated coagulopathy is made worse by hetastarch, but it can be rapidly reversed with the administration of blood components. Impressively, infusion of FFP, even without any red blood cells, can correct the coagulopathy and result in excellent early survival.

Increase in activated protein C mediates acute traumatic coagulopathy in mice

In severely injured and hypoperfused trauma patients, endogenous acute coagulopathy (EAC) is associated with an increased morbidity and mortality. Recent human data correlate this coagulopathy with activation of the protein C pathway. To examine the mechanistic role of protein C in the development of EAC, we used a mouse model of trauma and hemorrhagic shock, characterized by the combination of tissue injury and severe metabolic acidosis. Mice were subjected to one of four treatment groups: 1) C, control; 2) T, trauma (laparotomy); 3) H, hemorrhage (MAP, 35 mmHg x 60 min); 4) TH, trauma + hemorrhage. After 60 min, blood was drawn for analysis. Compared with C mice, the TH mice had a significantly elevated activated partial thromboplastin time (23.3 vs. 34.5 s) and significantly increased levels of activated protein C (aPC; 2.30 vs. 13.58 ng/mL). In contrast, T and H mice did not develop an elevated activated partial thromboplastin time or increased aPC. Selective inhibition of the anticoagulant property of aPC prevented the coagulopathy seen in response to trauma/hemorrhage (23.5 vs. 38.6 s [inhibitory vs. control monoclonal antibody]) with no impact on survival during the shock period. However, complete blockade of both the anticoagulant and cytoprotective functions of aPC caused 100% mortality within 45 min of shock, with histopathology evidence of pulmonary thrombosis and perivascular hemorrhage. These results indicate that our unique mouse model of T/H shock mimics our previous observations in trauma patients and demonstrates that EAC is mediated by the activation of the protein C pathway. In addition, the cytoprotective effect of protein C activation seems to be necessary for survival of the initial shock injury.

A new survivable damage control model including hypothermia, hemodilution, and liver injury

BACKGROUND

The purpose of this article is to describe a new model of traumatic intra-cavitary hemorrhage in a hypothermic, hemodiluted liver injury model that incorporates damage control principles and allows for survival.

MATERIALS AND METHODS

Twenty swine underwent a standardized 35% blood volume hemorrhage followed by resuscitation. Ten animals sustained nonsurgical and 10 a surgical high-grade liver injury. In the surgical liver injury, damage control gauze packing was performed. No operative treatment was provided for the nonsurgical liver injury, which was designed to test the efficacy of systemic hemostatic agents. After a 15 min treatment phase, the abdominal cavity was closed, with the packing in place for the surgical injury, and all animals were resuscitated. Necropsy was performed at 48 h post-injury.

RESULTS

At the time of liver injury, the animals were hemodiluted and hypothermic. Both injuries caused a 20% drop in the mean arterial pressure from baseline (P<0.001). Comparing baseline thromboelastography results with the results after hemodilution, hypothermia, and liver injury, a hypercoagulopathic state was observed. Mortality was 30% for both types of liver injury. The mean volume of intra-abdominal blood present at autopsy was similar for both types of liver injuries (202 ± 161 mL and 214 ± 203 mL, respectively).

CONCLUSION

A new model of traumatic intra-cavitary hemorrhage in a hypothermic, hemodiluted liver injury model with damage control that allows for survival has been described. The mortality rate of 30% allows for the comparison of therapeutic interventions that may lead to improved survival.

Surviving blood loss without blood transfusion in a swine poly-trauma model

BACKGROUND

We have demonstrated previously that valproic acid (VPA), a histone deacetylase inhibitor, can improve survival in lethal models of hemorrhagic shock. This study investigated whether VPA treatment would improve survival in a clinically relevant large animal model of poly-trauma/hemorrhagic shock, and whether the protective effects are executed through the Akt survival pathway.

METHODS

Yorkshire swine were subjected to a poly-trauma protocol including: (1) Pre-hospital phase- Femur fracture, 60% hemorrhage, 30 min of shock (mean arterial pressure [MAP]: 25-30 mmHg), and infusion of 154mM NaCl (3 x shed blood); (2) Early hospital phase A Grade V liver injury (simulating rupture of a previously contained hematoma) followed by liver packing; (3) Treatment/monitoring phase randomization to 3 treatment groups (n = 6-8/group): no treatment (control), fresh whole blood (FWB), and intravenous VPA (400 mg/kg, given during the pre-hospital phase). Animals were monitored for 4 h, with survival being the primary endpoint. Liver tissue was subjected to Western blot analysis.

RESULTS

FWB (n = 6) and VPA treatments (n = 7) significantly increased survival (100% and 86%, respectively) compared to control group (n = 8) (25%). The protocol produced significant anemia (Hb<6 g/dL) and lactic acidosis (lactate 3-5 mmol/L). Acidosis improved after blood transfusion and worsened in the other two groups. VPA treatment increased phospho-Akt (activated), phospho-GSK-3beta (Glycogen synthase kinase 3beta), beta-catenin and Bcl-2 (B-cell leukemia/lymphoma 2) protein levels compared to control group (P = .01, .01, .03, and .02, respectively). There was no significant difference in the level of these proteins between the control and FWB groups.

CONCLUSION

Treatment with VPA without blood transfusion improves early survival in a highly lethal poly-trauma and hemorrhagic shock model. The survival advantage is due not to improvement in resuscitation but to better tolerance of shock by the cells, in part due to the preservation of the Akt survival pathway.