A porcine polytrauma model with two different degrees of hemorrhagic shock: outcome related to trauma within the first 48 h

A dumbbell rescue stent graft facilitates clamp-free repair of aortic injury in a porcine model

Objective

Noncompressible torso hemorrhage is a high-mortality injury. We previously reported improved outcomes with a retrievable rescue stent graft to temporize aortic hemorrhage in a porcine model while maintaining distal perfusion. A limitation was that the original cylindrical stent graft design prohibited simultaneous vascular repair, given the concern for suture ensnarement of the temporary stent. We hypothesized that a modified, dumbbell-shaped design would preserve distal perfusion and also offer a bloodless plane in the midsection, facilitating repair with the stent graft in place and improve the postrepair hemodynamics.

Methods

In an Institutional Animal Care and Use Committee-approved terminal porcine model, a custom retrievable dumbbell-shaped rescue stent graft (dRS) was fashioned from laser-cut nitinol and polytetrafluoroethylene covering and compared with aortic cross-clamping. Under anesthesia, the descending thoracic aorta was injured and then repaired with cross-clamping (n = 6) or dRS (n = 6). Angiography was performed in both groups. Operations were divided into phases: (1) baseline, (2) thoracic injury with either cross-clamp or dRS deployed, and (3) recovery, after which the clamp or dRS were removed. Target blood loss was 22% to simulate class II or III hemorrhagic shock. Shed blood was recovered with a Cell Saver and reinfused for resuscitation. Renal artery flow rates were recorded at baseline and during the repair phase and reported as a percentage of cardiac output. Phenylephrine pressor requirements were recorded.

Results

In contrast with cross-clamped animals, dRS animals demonstrated both operative hemostasis and preserved flow beyond the dRS angiographically. Recovery phase mean arterial pressure, cardiac output, and right ventricular end-diastolic volume were significantly higher in dRS animals (P = .033, P = .015, and P = .012, respectively). Whereas distal femoral blood pressures were absent during cross-clamping, among the dRS animals, the carotid and femoral MAPs were not significantly different during the injury phase (P = .504). Cross-clamped animals demonstrated nearly absent renal artery flow, in contrast with dRS animals, which exhibited preserved perfusion (P<.0001). Femoral oxygen levels (partial pressure of oxygen) among a subset of animals further confirmed greater distal oxygenation during dRS deployment compared with cross-clamping (P = .006). After aortic repair and clamp or stent removal, cross-clamped animals demonstrated more significant hypotension, as demonstrated by increased pressor requirements over stented animals (P = .035).

Conclusions

Compared with aortic cross-clamping, the dRS model demonstrated superior distal perfusion, while also facilitating simultaneous hemorrhage control and aortic repair. This study demonstrates a promising alternative to aortic cross-clamping to decrease distal ischemia and avoid the unfavorable hemodynamics that accompany clamp reperfusion. Future studies will assess differences in ischemic injury and physiological outcomes.

Clinical Relevance

Noncompressible aortic hemorrhage remains a high-mortality injury, and current damage control options are limited by ischemic complications. We have previously reported a retrievable stent graft to allow rapid hemorrhage control, preserved distal perfusion, and removal at the primary repair. The prior cylindrical stent graft was limited by the inability to suture the aorta over the stent graft owing to risk of ensnarement. This large animal study explored a dumbbell retrievable stent with a bloodless plane to allow suture placement with the stent in place. This approach improved distal perfusion and hemodynamics over clamp repair and heralds the potential for aortic repair while avoiding complications.

Pulmonary inflammatory response and immunomodulation to multiple trauma and hemorrhagic shock in pigs

BACKGROUND

Patients suffering from severe trauma experience substantial immunological stress. Lung injury is a known risk factor for the development of posttraumatic complications, but information on the long-term course of the pulmonary inflammatory response and treatment with mild hypothermia are scarce.

AIM

To investigate the pulmonary inflammatory response to multiple trauma and hemorrhagic shock in a porcine model of combined trauma and to assess the immunomodulatory properties of mild hypothermia.

METHODS

Following induction of trauma (blunt chest trauma, liver laceration, tibia fracture), two degrees of hemorrhagic shock (45 and 50%) over 90 (n = 30) and 120 min. (n = 20) were induced. Animals were randomized to hypothermia (33°C) or normothermia (38°C). We evaluated bronchoalveolar lavage (BAL) fluid and tissue levels of cytokines and investigated changes in microRNA- and gene-expression as well as tissue apoptosis.

RESULTS

We observed a significant induction of Interleukin (IL) 1β, IL-6, IL-8, and Cyclooxygenase-2 mRNA in lung tissue. Likewise, an increased IL-6 protein concentration could be detected in BAL-fluid, with a slight decrease of IL-6 protein in animals treated with hypothermia. Lower IL-10 protein levels in normothermia and higher IL-10 protein concentrations in hypothermia accompanied this trend. Tissue apoptosis increased after trauma. However, intervention with hypothermia did not result in a meaningful reduction of pro-inflammatory biomarkers or tissue apoptosis.

CONCLUSION

We observed signs of a time-dependent pulmonary inflammation and apoptosis at the site of severe trauma, and to a lower extent in the trauma-distant lung. Intervention with mild hypothermia had no considerable effect during 48 hours following trauma.

Club cell protein (CC)16 as potential lung injury marker in a porcine 72 h polytrauma model

BACKGROUND

Polytrauma and respiratory tract damage after thoracic trauma cause about 25% of mortality among severely injured patients. Thoracic trauma can lead to the development of severe lung complications such as acute respiratory distress syndrome, and is, therefore, of great interest for monitoring in intensive care units (ICU). In recent years, club cell protein (CC)16 with its antioxidant properties has proven to be a potential outcome-related marker. In this study, we evaluated whether CC16 constitutes as a marker of lung damage in a porcine polytrauma model.

METHODS

In a 72 h ICU polytrauma pig model (thoracic trauma, tibial fracture, hemorrhagic shock, liver laceration), blood plasma samples (0, 3, 9, 24, 48, 72 h), BAL samples (72 h) and lung tissue (72 h) were collected. The trauma group (PT) was compared to a sham group. CC16 as a possible biomarker for lung injury in this model, and IL-8 concentrations as known indicator for ongoing inflammation during trauma were determined by ELISA. Histological analysis of ZO-1 and determination of total protein content were used to show barrier disruption and edema formation in lung tissue from the trauma group.

RESULTS

Systemic CC16 levels were significantly increased early after polytrauma compared vs. sham. After 72 h, CC16 concentration was significantly increased in lung tissue as well as in BAL in PT vs. sham. Similarly, IL-8 and total protein content in BAL were significantly increased in PT vs. sham. Evaluation of ZO-1 staining showed significantly lower signal intensity for polytrauma.

CONCLUSION

The data confirm for the first time in a larger animal polytrauma model that lung damage was indicated by systemic and/or local CC16 response. Thus, early plasma and late BAL CC16 levels might be suitable to be used as markers of lung injury in this polytrauma model.

Hemodynamic Effect of Resuscitative Endovascular Balloon Occlusion of the Aorta in Hemodynamic Instability Secondary to Acute Cardiac Tamponade in a Porcine Model

BACKGROUND

The pre-hospital use of Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) is increasing, although it remains controversial, in part because of suggested contraindications such as acute cardiac tamponade (ACT). As both the pre-hospital and in-hospital use of REBOA might potentially occur with concurrent ACT, knowledge of the hemodynamic effect of REBOA in this setting is crucial. This study, therefore, aimed at investigating the physiological effects of REBOA in hemodynamic instability secondary to ACT in a porcine model. We hypothesize that REBOA can temporarily increase systemic blood pressure and carotid blood flow, and prolong survival, in hemodynamic shock caused by ACT.

METHODS

Fourteen pigs (24-38 kg) underwent ACT, through true cardiac injury and hemorrhage into the pericardial space, and were allowed to hemodynamically deteriorate. At a systolic blood pressure (SBP) of 50 mm Hg (SBP50) they were randomized to total occlusion REBOA in zone 1 or to a control group. Survival, hemodynamic parameters, carotid blood flow (CBF), femoral blood flow (FBF), cardiac output (CO), end-tidal CO2, and arterial blood gas parameters were analyzed.

RESULTS

REBOA intervention was associated with a significant increase in SBP (50 mm Hg to 74 mm Hg, P = 0.016) and CBF (110 mL/min to 195 mL/min, P = 0.031), with no change in CO, compared to the control group. At 20 min after SBP50, the survival rate in the intervention group was 86% and in the control group 14%, with time to death being significantly longer in the intervention group.

CONCLUSIONS

This randomized animal study demonstrates that REBOA can help provide hemodynamic stabilization and prolong survival in hemodynamic shock provoked by ACT. It is important to stress that our study does not change the fact that urgent pericardiocentesis or cardiac surgery is, and should remain, the standard optimal treatment for ACT.Level of evidence: Prospective, randomized, experimental animal study. Basic science study, therapeutic.

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 Simple Cardiovascular Model for the Study of Hemorrhagic Shock

Hemorrhagic shock is the number one cause of death on the battlefield and in civilian trauma as well. Mathematical modeling has been applied in this context for decades; however, the formulation of a satisfactory model that is both practical and effective has yet to be achieved. This paper introduces an upgraded version of the 2007 Zenker model for hemorrhagic shock termed the ZenCur model that allows for a better description of the time course of relevant observations. Our study provides a simple but realistic mathematical description of cardiovascular dynamics that may be useful in the assessment and prognosis of hemorrhagic shock. This model is capable of replicating the changes in mean arterial pressure, heart rate, and cardiac output after the onset of bleeding (as observed in four experimental laboratory animals) and achieves a reasonable compromise between an overly detailed depiction of relevant mechanisms, on the one hand, and model simplicity, on the other. The former would require considerable simulations and entail burdensome interpretations. From a clinical standpoint, the goals of the new model are to predict survival and optimize the timing of therapy, in both civilian and military scenarios.

Hematological and Chemical Profiles in a Porcine Model of Severe Multiple Trauma

BACKGROUND

Clinical chemistry and hematological tests are widely used to monitor the clinical course of several diseases. However, these parameters are sparse in large-animal models of multiple trauma (MT). Thus, we aimed to provide these missing data to improve future experimental setups in trauma research.

METHODS

Male pigs (German Landrace pigs) were randomized into either an MT group (n = 8) including blunt thoracic trauma, tibial fracture, and controlled hemorrhage or a sham group (n = 8) without any trauma. After trauma induction, all animals received intensive care treatment for 72 h under anesthesia, including mechanical ventilation and volume resuscitation. Blood and urine samples were obtained to measure common hematological and chemical parameters before trauma (0 h), after trauma (1.5 h), during resuscitation (2.5 h), after fracture stabilization (3.5 h), and at 12, 24, 48, and 72 h. Statistical analyses were performed using a linear mixed model (group × time) and Welch's ANOVA.

RESULTS

MT led to a perceptible immunological reaction. Between groups, significantly different time courses of leukocyte counts (p = 0.034) and lymphocyte proportions (p = 0.001) were observed. Moreover, MT changed the time course of total protein (p = 0.006). Significantly lower concentrations compared to sham were found in MT at each single time point starting at 1.5 h to the end of the observation period (all p < 0.05).

CONCLUSIONS

Our results indicate that a traumatic insult leads to significant alterations in the immune system already shortly after trauma. Together with the additional catabolic reactions observed, these alterations might contribute to the occurrence of later complications. The presented data provide valid references for further experimental setups with prolonged observation times, especially in similar porcine models of MT.

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.

Complement Activation and Organ Damage After Trauma-Differential Immune Response Based on Surgical Treatment Strategy

Background: The complement system is part of the innate immunity, is activated immediately after trauma and is associated with adult respiratory distress syndrome, acute lung injury, multiple organ failure, and with death of multiply injured patients. The aim of the study was to investigate the complement activation in multiply injured pigs as well as its effects on the heart in vivo and in vitro. Moreover, the impact of reamed vs. non-reamed intramedullary nailing was examined with regard to the complement activation after multiple trauma in pigs.

Materials and Methods: Male pigs received multiple trauma, followed by femoral nailing with/without prior conventional reaming. Systemic complement hemolytic activity (CH-50 and AH-50) as well as the local cardiac expression of C3a receptor, C5a receptors1/2, and the deposition of the fragments C3b/iC3b/C3c was determined in vivo after trauma. Human cardiomyocytes were exposed to C3a or C5a and analyzed regarding calcium signaling and mitochondrial respiration.

Results: Systemic complement activation increased within 6 h after trauma and was mediated via the classical and the alternative pathway. Furthermore, complement activation correlated with invasiveness of fracture treatment. The expression of receptors for complement activation were altered locally in vivo in left ventricles. C3a and C5a acted detrimentally on human cardiomyocytes by affecting their functionality and their mitochondrial respiration in vitro.

Conclusion: After multiple trauma, an early activation of the complement system is triggered, affecting the heart in vivo as well as in vitro, leading to complement-induced cardiac dysfunction. The intensity of complement activation after multiple trauma might correlate with the invasiveness of fracture treatment. Reaming of the femoral canal might contribute to an enhanced “second hit” response after trauma. Consequently, the choice of fracture treatment might imply the clinical outcome of the critically injured patients and might be therefore crucial for their survival.

Trauma Severity and Its Impact on Local Inflammation in Extremity Injury-Insights From a Combined Trauma Model in Pigs

Background: Extremity fracture is frequently seen in multiple traumatized patients. Local post-traumatic inflammatory reactions as well as local and systemic interactions have been described in previous studies. However, trauma severity and its impact on the local immunologic reaction remains unclear. Therefore, fracture-associated local inflammation was investigated in a porcine model of isolated and combined trauma to gain information about the early inflammatory stages.

Material and Methods: Polytrauma (PT) consisted of lung contusion, liver laceration, femur fracture, and controlled hemorrhage. Monotrauma (MT) consisted of femur fracture only. The fracture was operatively stabilized and animals were monitored under ICU-standard for 72 h. Blood, fracture hematoma (FH) as well as muscle samples were collected throughout the experimental period. Levels of local and systemic pro- and anti-inflammatory as well as angiogenetic cytokines were measured by ELISA.

Results: Both groups showed a significant decrease in pro-inflammatory IL-6 in FH over time. However, concentrations in MT were significantly higher than in PT. The IL-8 concentrations initially decreased in FH, but recovered by the end of the observation period. These dynamics were only statistically significant in MT. Furthermore, concentrations measured in muscle tissue showed inverse kinetics compared to those in FH. The IL-10 did not present statistical resilient dynamics over time, although a slight increase in FH was seen by the end of the observation time in the MT group.

Conclusions: Time-dependent dynamics of the local inflammatory response were observed. Trauma severity showed a significant impact, with lower values in pro- as well as angiogenetic mediators. Fracture repair could be altered by these trauma-related changes of the local immunologic milieu, which might serve as a possible explanation for the higher rates of delayed or non-union bone repair in polytraumatised patients.

New hemostatic device for grade IV-V liver injury in porcine model: a proof of concept

Background

The liver is the most injured organ following abdominal trauma. Uncontrolled bleeding remains the main cause of early liver injury-related death, with a mortality rate of 50–54% in the first 24 h after admission and with 80% of operative deaths. Packing and reoperation account for the increased survival in severe liver trauma, and they are recommended for severe liver injuries (grades IV–V).

Perihepatic packing can lead to several potential complications. An excessive packing can cause complications due to abdominal compartment syndrome, while a soft packing may be ineffective, and thus, bleeding can continue inadvertently with the consequent hypovolemic shock and potentially death.

Methods

We designed a new vacuum-based device to perform perihepatic packing without the negative side-effects of the classic technique. We conducted a prospective pilot feasibility study in a porcine model. We compared the traditional perihepatic packing (PHP) (n = 2) with the new VacBagPack device (VBP) (n = 2).

Results

Both pigs survived with the new device and showed an equivalent outcome to the one that survived in the traditional technique group. Blood tests were similar too. This suggests that VBP could be at least as effective as traditional PHP.

Conclusions

We establish a first step towards the development of a new packing device. A new study with a bigger sample size still in pigs will be conducted. Also, an industrial model of the device is currently in production.

Midkine Is Elevated After Multiple Trauma and Acts Directly on Human Cardiomyocytes by Altering Their Functionality and Metabolism

Background and Purpose: Post-traumatic cardiac dysfunction often occurs in multiply injured patients (ISS ≥ 16). Next to direct cardiac injury, post-traumatic cardiac dysfunction is mostly induced by the release of inflammatory biomarkers. One of these is the heparin-binding factor Midkine, which is elevated in humans after fracture, burn injury and traumatic spinal cord injury. Midkine is associated with cardiac pathologies but the exact role of Midkine in the development of those diseases is ambiguous. The systemic profile of Midkine after multiple trauma, its effects on cardiomyocytes and the association with post-traumatic cardiac dysfunction, remain unknown.

Experimental Approach: Midkine levels were investigated in blood plasma of multiply injured humans and pigs. Furthermore, human cardiomyocytes (iPS) were cultured in presence/absence of Midkine and analyzed regarding viability, apoptosis, calcium handling, metabolic alterations, and oxidative stress. Finally, the Midkine filtration capacity of the therapeutic blood absorption column CytoSorb ®300 was tested with recombinant Midkine or plasma from multiply injured patients.

Key Results: Midkine levels were significantly increased in blood plasma of multiply injured humans and pigs. Midkine acts on human cardiomyocytes, altering their mitochondrial respiration and calcium handling in vitro. CytoSorb®300 filtration reduced Midkine concentration ex vivo and in vitro depending on the dosage.

Conclusion and Implications: Midkine is elevated in human and porcine plasma after multiple trauma, affecting the functionality and metabolism of human cardiomyocytes in vitro. Further examinations are required to determine whether the application of CytoSorb®300 filtration in patients after multiple trauma is a promising therapeutic approach to prevent post-traumatic cardiac disfunction.

Cerebral Alterations Following Experimental Multiple Trauma and Hemorrhagic Shock

Multiple trauma (MT) associated with hemorrhagic shock (HS) might lead to cerebral hypoperfusion and brain damage. We investigated cerebral alterations using a new porcine MT/HS model without traumatic brain injury (TBI) and assessed the neuroprotective properties of mild therapeutic hypothermia. Male pigs underwent standardized MT with HS (45% or 50% loss of blood volume) and resuscitation after 90/120 min (T90/T120). In additional groups (TH90/TH120) mild hypothermia (33°C) was induced following resuscitation. Normothermic or hypothermic sham animals served as controls. Intracranial pressure, cerebral perfusion pressure (CPP), and cerebral oxygenation (PtiO2) were recorded up to 48.5 h. Serum protein S-100B and neuron-specific enolase (NSE) were measured by ELISA. Cerebral inflammation was quantified on hematoxylin and eosin -stained brain slices; Iba1, S100, and inducible nitric oxide synthase (iNOS) expression was assessed using immunohistochemistry. Directly after MT/HS, CPP and PtiO2 were significantly lower in T90/T120 groups compared with sham. After resuscitation both parameters showed a gradual recovery. Serum protein S-100B and NSE increased temporarily as a result of MT/HS in T90 and T90/T120 groups, respectively. Cerebral inflammation was found in all groups. Iba1-staining showed significant microgliosis in T90 and T120 animals. iNOS-staining indicated a M1 polarization. Mild hypothermia reduced cerebral inflammation in the TH90 group, but resulted in increased iNOS activation. In this porcine long-term model, we did not find evidence of gross cerebral damage when resuscitation was initiated within 120 min after MT/HS without TBI. However, trauma-related microglia activation and M1 microglia polarization might be a consequence of temporary hypoxia/ischemia and further research is warranted to detail underlying mechanisms. Interestingly, mild hypothermia did not exhibit neuroprotective properties when initiated in a delayed fashion.

Nerve grafting for peripheral nerve injuries with extended defect sizes

Artificial and non-artificial nerve grafts are the gold standard in peripheral nerve reconstruction in cases with extensive loss of nerve tissue, particularly where a direct end-to-end suture or an autologous nerve graft is inauspicious. Different materials are marketed and approved by the US Food and Drug Administration (FDA) for peripheral nerve graft reconstruction. The most frequently used materials are collagen and poly(DL-lactide-ε-caprolactone). Only one human nerve allograft is listed for peripheral nerve reconstruction by the FDA. All marketed nerve grafts are able to demonstrate sufficient nerve regeneration over small distances not exceeding 3.0 cm. A key question in the field is whether nerve reconstruction on large defect lengths extending 4.0 cm or more is possible. This review gives a summary of current clinical and experimental approaches in peripheral nerve surgery using artificial and non-artificial nerve grafts in short and long distance nerve defects. Strategies to extend nerve graft lengths for long nerve defects, such as enhancing axonal regeneration, include the additional application of Schwann cells, mesenchymal stem cells or supporting co-factors like growth factors on defect sizes between 4.0 and 8.0 cm.

Hypothermia does not influence liver damage and function in a porcine polytrauma model

BACKGROUND

Previous studies revealed evidence that induced hypothermia attenuates ischemic organ injuries after severe trauma. In the present study, the effect of hypothermia on liver damage was investigated in a porcine long term model of multi-system injury, consisting of blunt chest trauma, penetrating abdominal trauma, musculoskeletal injury, and hemorrhagic shockMETHODS: In 30 pigs, a standardized polytrauma including blunt chest trauma, penetrating abdominal trauma, musculoskeletal injury, and hemorrhagic shock of 45% of total blood volume was induced. Following trauma, hypothermia of 33∘C was induced for 12 h and intensive care treatment was evaluated for 48 h. As outcome parameters, we assessed liver function and serum transaminase levels as well as a histopathological analysis of tissue samples. A further 10 animals served as controls.

RESULTS

Serum transaminase levels were increased at the end of the observation period following hypothermia without reaching statistical significance compared to normothermic groups. Liver function was preserved (p⩽ 0.05) after the rewarming period in hypothermic animals but showed no difference at the end of the observation period. In H&E staining, cell death was slightly increased hypothermic animals and caspase-3 staining displayed tendency towards more apoptosis in hypothermic group as well.

CONCLUSIONS

Induction of hypothermia could not significantly improve hepatic damage during the first 48 h following major trauma. Further studies focusing on multi-organ failure including a longer observation period are required to illuminate the impact of hypothermia on hepatic function in multiple trauma patients.

Cardiac Depression in Pigs after Multiple Trauma - Characterization of Posttraumatic Structural and Functional Alterations

The purpose of this study was to define the relationship between cardiac depression and morphological and immunological alterations in cardiac tissue after multiple trauma. However, the mechanistic basis of depressed cardiac function after trauma is still elusive. In a porcine polytrauma model including blunt chest trauma, liver laceration, femur fracture and haemorrhage serial trans-thoracic echocardiography was performed and correlated with cellular cardiac injury as well as with the occurrence of extracellular histones in serum. Postmortem analysis of heart tissue was performed 72 h after trauma. Ejection fraction and shortening fraction of the left ventricle were significantly impaired between 4 and 27 h after trauma. H-FABP, troponin I and extracellular histones were elevated early after trauma and returned to baseline after 24 and 48 h, respectively. Furthermore, increased nitrotyrosine and Il-1β generation and apoptosis were identified in cardiac tissue after trauma. Main structural findings revealed alteration of connexin 43 (Cx43) and co-translocation of Cx43 and zonula occludens 1 to the cytosol, reduction of α-actinin and increase of desmin in cardiomyocytes after trauma. The cellular and subcellular events demonstrated in this report may for the first time explain molecular mechanisms associated with cardiac dysfunction after multiple trauma.

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.

Long-Term Effects of Induced Hypothermia on Local and Systemic Inflammation - Results from a Porcine Long-Term Trauma Model

Background

Hypothermia has been discussed as playing a role in improving the early phase of systemic inflammation. However, information on the impact of hypothermia on the local inflammatory response is sparse. We therefore investigated the kinetics of local and systemic inflammation in the late posttraumatic phase after induction of hypothermia in an established porcine long-term model of combined trauma.

Materials & Methods

Male pigs (35 ± 5kg) were mechanically ventilated and monitored over the study period of 48 h. Combined trauma included tibia fracture, lung contusion, liver laceration and pressure-controlled hemorrhagic shock (MAP < 30 ± 5 mmHg for 90 min). After resuscitation, hypothermia (33°C) was induced for a period of 12 h (HT-T group) with subsequent re-warming over a period of 10 h. The NT-T group was kept normothermic. Systemic and local (fracture hematoma) cytokine levels (IL-6, -8, -10) and alarmins (HMGB1, HSP70) were measured via ELISA.

Results

Severe signs of shock as well as systemic and local increases of pro-inflammatory mediators were observed in both trauma groups. In general the local increase of pro- and anti-inflammatory mediator levels was significantly higher and prolonged compared to systemic concentrations. Induction of hypothermia resulted in a significantly prolonged elevation of both systemic and local HMGB1 levels at 48 h compared to the NT-T group. Correspondingly, local IL-6 levels demonstrated a significantly prolonged increase in the HT-T group at 48 h.

Conclusion

A prolonged inflammatory response might reduce the well-described protective effects on organ and immune function observed in the early phase after hypothermia induction. Furthermore, local immune response also seems to be affected. Future studies should aim to investigate the use of therapeutic hypothermia at different degrees and duration of application.