Combined hemorrhage/trauma models in pigs-current state and future perspectives

A translational study evaluating a ruggedized portable oxygen concentrator versus an oxygen cylinder in simulated polytrauma intubation of swine

Objectives

Portable oxygen concentrators (POCs) are medical devices that use filters to selectively remove nitrogen from ambient air to produce concentrated, medical-grade oxygen. This is the first study to evaluate a ruggedized POC's performance during simulated polytrauma intubation.

Methods

Twenty-seven swine were intubated and anesthetized with ketamine. At T = 0, animals were extubated, received a chest wall injury, a tibia fracture, and 20% total blood volume controlled hemorrhage was initiated. At T = 10 min, the swine were pre-oxygenated using a bag-valve mask connected to one of three randomized oxygen sources: (1) a ruggedized POC, (2) a M-15 oxygen cylinder, or (3) room air (control). At T = 12 min, animals were re-intubated to simulate polytrauma intubation and connected to the test oxygen source for the remainder of the experiment. Surviving animals entered a 2-h period where partial pressure of oxygen (PaO2), oxygen saturation (SpO2), and regional oxygen saturation (rSO2) were monitored. Groups were compared using analysis of variance (ANOVA), Fisher's exact, log-rank analysis, or mixed-effects model as appropriate.

Results

All animals survived except one in the POC group. Mixed-effects models revealed differences between groups with regards to PaO2 (p < 0.0001) and SpO2 (p = 0.006). Based on post hoc analysis, oxygen cylinder PaO2 was superior to both POC and control, but there were no differences between POC and control PaO2. There were statistically and clinically significant differences in SpO2 during periods of pre-oxygenation (T = 10‒12 min), intubation (T = 12‒14 min), and immediately after intubation (T = 14‒20 min). The POC battery was consumed in 43 ± 13 min.

Conclusion

In our swine model, a single, ruggedized POC provided inferior amounts of oxygen supplementation compared to an oxygen cylinder and performed no better than room air.

Effects of anesthesia with sevoflurane on outcome parameters in murine experimental studies

PURPOSE

Multiple murine studies modelling the immuno-pathophysiological consequences of trauma, shock, burn or sepsis were performed during the last decades. Almost every animal model requires anesthesia for practical and ethical reasons. Furthermore, often, corresponding control groups involve untreated animals without or with a limited exposure to anesthetics. However, the influences of anesthetic drugs on immuno-pathophysiological reactions remain insufficiently investigated. Therefore, we aimed to closer characterize the anesthetic impact exemplified by sevoflurane on the organ performance in mice and thereby investigate the influence of anesthesia itself on major outcome parameters in animal studies.

METHODS

C57/BL6 mice were subjected either to 270 min of sevoflurane narcosis or directly euthanized. Plasma, BAL-fluids, lungs, kidneys, liver and intestine were collected and examined for immunological, functional and morphological changes.

RESULTS

Systemic levels of the cytokine keratinocyte chemoattractant (KC) were raised in the narcosis group, while concentrations of high mobility group box protein 1 (HMGB-1) as a major inflammatory marker were reduced. In the lungs, levels of HMGB-1 and interleukin 6 (IL-6) were reduced. In contrast, systemic concentrations of intestinal fatty acid binding-protein (i-FABP) as an intestinal damage marker were elevated. Furthermore, liver-type fatty acid binding-protein (L-FABP) levels were lower in the narcosis animals, and inflammatory markers were reduced in liver tissues. Anesthesia also ameliorated the inflammatory reaction in renal tissues, while plasma levels of urea and creatinine were elevated, reflecting either dehydration and/or impaired renal function.

CONCLUSION

As anesthesia with sevoflurane exhibited distinct effects in different organs, it is difficult to predict its specific impact on targets of interest in in vivo studies. Therefore, further studies are required to clarify the effects of different anesthetic drugs. Overall, the inclusion of a control group subjected to the same anesthesia protocol as the experimental groups of interest seems helpful to precisely define the inherent impact of the anesthetic when investigating immuno-pathophysiologic conditions in vivo.

Fracture haematoma proteomics

Aims

The aim of this study was to determine the fracture haematoma (fxH) proteome after multiple trauma using label-free proteomics, comparing two different fracture treatment strategies.

Methods

A porcine multiple trauma model was used in which two fracture treatment strategies were compared: early total care (ETC) and damage control orthopaedics (DCO). fxH was harvested and analyzed using liquid chromatography-tandem mass spectrometry. Per group, discriminating proteins were identified and protein interaction analyses were performed to further elucidate key biomolecular pathways in the early fracture healing phase.

Results

The early fxH proteome was characterized by immunomodulatory and osteogenic proteins, and proteins involved in the coagulation cascade. Treatment-specific proteome alterations were observed. The fxH proteome of the ETC group showed increased expression of pro-inflammatory proteins related to, among others, activation of the complement system, neutrophil functioning, and macrophage activation, while showing decreased expression of proteins related to osteogenesis and tissue remodelling. Conversely, the fxH proteome of the DCO group contained various upregulated or exclusively detected proteins related to tissue regeneration and remodelling, and proteins related to anti-inflammatory and osteogenic processes.

Conclusion

The early fxH proteome of the ETC group was characterized by the expression of immunomodulatory, mainly pro-inflammatory, proteins, whereas the early fxH proteome of the DCO group was more regenerative and osteogenic in nature. These findings match clinical observations, in which enhanced surgical trauma after multiple trauma causes dysbalanced inflammation, potentially leading to reduced tissue regeneration, and gained insights into regulatory mechanisms of fracture healing after severe trauma.

Preclinical models of orthopaedic trauma: Orthopaedic Research Society (ORS) and Orthopaedic Trauma Association (OTA) symposium 2022

Orthopaedic trauma remains a leading cause of patient morbidity, mortality, and global health care burden. Although significant advances have been made in the diagnosis, treatment, and rehabilitation of these injuries, complications such as malunion, nonunion, infection, disuse muscle atrophy and osteopenia, and incomplete return to baseline function still occur. The significant inherent clinical variability in fracture care such as differing patient demographics, injury patterns, and treatment protocols make standardized and replicable study, especially of cellular and molecular based mechanisms, nearly impossible. Hence, the scientists dedicated to improving therapy and treatments for patients with orthopaedic trauma rely on preclinical models. Preclinical models have proven to be invaluable in understanding the timing between implant insertion and bacterial inoculation on the bioburden of infection. Posttraumatic arthritis (PTOA) can take years to develop clinically, but with a porcine pilon fracture model, posttraumatic arthritis can be reliably induced, so different surgical and therapeutic strategies can be tested in prevention. Conversely, the racehorse presents a well-accepted model of naturally occurring PTOA. With preclinical polytrauma models focusing on chest injury, abdominal injury, multiple fractures, and/or head injury, one can study how various injury patterns affect fracture healing can be systemically studied. Finally, these preclinical models serve as a translational bridge to for clinical application in human patients. With selection of the right preclinical model, studies can build a platform to decrease the risk of emerging technologies and provide foundational support for therapeutic clinical trials. In summary, orthopaedic trauma preclinical models allow scientists to simplify a complex clinical challenge, to understand the basic pathways starting with lower vertebrate models. Then, R&D efforts progress to higher vertebrate models to build in more complexity for translation of findings to the clinical practice.

Real-Time Measurements of Oral Mucosal Carbon Dioxide (POMCO2) Reveals an Inverse Correlation With Blood Pressure in a Porcine Model of Coagulopathic Junctional Hemorrhage

INTRODUCTION

Shock states that occur during, for example, profound hemorrhage can cause global tissue hypoperfusion leading to organ failure. There is an unmet need for a reliable marker of tissue perfusion during hemorrhage that can be followed longitudinally. Herein, we investigated whether longitudinal POMCO2 tracks changes in hemodynamics in a swine model of coagulopathic uncontrolled junctional hemorrhage.

MATERIALS AND METHODS

Female Yorkshire-crossbreed swine (n = 7, 68.1 ± 0.7 kg) were anesthetized and instrumented for continuous measurement of mean arterial pressure (MAP). Coagulopathy was induced by the exchange of 50 to 60% of blood volume with 6% Hetastarch over 30 minutes to target a hematocrit of <15%. A 4.5-mm arteriotomy was made in the right common femoral artery with 30 seconds of free bleeding. POMCO2 was continuously measured from baseline through hemodilution, hemorrhage, and a subsequent 3-h intensive care unit period. Rotational thromboelastometry and blood gases were measured.

RESULTS

POMCO2 and MAP showed no significant changes during the hemodilution phase of the experiment, which produced coagulopathy evidenced by prolonged clot formation times. However, POMCO2 increased because of the uncontrolled hemorrhage by 11.3 ± 3.1 mmHg and was inversely correlated with the drop (17.9 ± 5.9 mmHg) in MAP (Y = -0.4122*X + 2.649, P = .02, r2 = 0.686). In contrast, lactate did not significantly correlate with the changes in MAP (P = .35) or POMCO2 (P = .37).

CONCLUSIONS

Despite the logical appeal of measuring noninvasive tissue CO2 measurement as a surrogate for gastrointestinal perfusion, prior studies have only reported snapshots of this readout. The present investigation shows real-time longitudinal measurement of POMCO2 to confirm that MAP inversely correlates to POMCO2 in the face of coagulopathy. The simplicity of measuring POMCO2 in real time can provide an additional practical option for military or civilian medics to monitor trends in hypoperfusion during hemorrhagic shock.

Biological response of nonhuman primates to controlled levels of acute blood loss

Introduction

The global shortage of human blood for medical use has prompted the development of alternative blood sources. Nonhuman primates (NHPs) are commonly used owing to their physiological similarities to humans. The objective of the current study was to establish a controlled-blood-loss model in NHPs to explore their clinical and biological responses.

Methods

Blood was sequentially withdrawn from 10 cynomolgus monkeys (10, 14, 18, 22, and 25% of the total blood volume); their vital signs were monitored, and blood parameters were serially analyzed. Humoral mediators in the blood were measured using flow cytometry and enzyme-linked immunosorbent assays.

Results

In NHPs subjects to 25% blood loss and presenting with related clinical symptoms, the systolic blood pressure ratio on day 0 after bleeding was significantly lower than that of the animals from the other groups (median: 0.65 vs. 0.88, P = 0.0444). Red blood cell counts from day 0-14 and hematocrit levels from day 0-7 were markedly decreased relative to the baseline (P < 0.01). These parameters showed a direct correlation with the extent of blood loss. The levels of creatine phosphokinase, aspartate aminotransferase, and alanine aminotransferase exhibited increases in response to blood loss and had a stronger correlation with the hemoglobin ratio than the volume of blood loss. The levels of C3a and C4a, as well as interleukin (IL)-1α and IL-15, displayed a strong correlation, with no apparent association with blood loss.

Conclusion

The findings of the present study showed that only NHPs with 25% blood loss exhibited clinical decompensation and significant systolic blood pressure reduction without fatalities, suggesting that this level of blood loss is suitable for evaluating blood transfusion efficacy or other treatments in NHP models. In addition, the ratio of hemoglobin may serve as a more dependable marker for predicting clinical status than the actual volume of blood loss. Thus, our study could serve as a basis for future xenotransfusion research and to predict biological responses to massive blood loss in humans where controlled experiments cannot be ethically performed.

Establishment and validation of intravenous anesthesia with dexmedetomidine for pigs under assisted spontaneous breathing: A preclinical model of intensive care conditions

Large animal models are frequently used to investigate new medical approaches. In most cases, animals are kept under general anesthesia and mandatory mechanical ventilation during the experiments. However, in some situations assisted spontaneous breathing is essential, e.g. when simulating conditions in a modern intensive care unit. Therefore, we established an anesthesia regime with dexmedetomidine and midazolam/ketamine in porcine models of assisted spontaneous breathing. The total intravenous anesthesia was used in lung healthy pigs, in pigs with oleic acid induced acute respiratory distress syndrome and in pigs with methacholine induced bronchopulmonary obstruction. We were able to maintain stable conditions of assisted spontaneous breathing without impairment of hemodynamic, respiratory or blood gas variables in lung healthy pigs and pigs with induced acute respiratory distress syndrome for a period of five hours and in pigs with induced bronchopulmonary obstruction for three hours. Total intravenous anesthesia containing dexmedetomidine enables stable conditions of assisted spontaneous breathing in healthy pigs, in pigs with induced acute respiratory distress syndrome and in pigs induced bronchopulmonary obstruction as models of intensive care unit conditions.

The Use of Large Animal Models in Trauma and Bleeding Studies

BACKGROUND

 Major trauma often results in significant bleeding and coagulopathy, posing a substantial clinical burden. To understand the underlying pathophysiology and to refine clinical strategies to overcome coagulopathy, preclinical large animal models are often used. This review scrutinizes the clinical relevance of large animal models in hemostasis research, emphasizing challenges in translating findings into clinical therapies.

METHODS

 We conducted a thorough search of PubMed and EMBASE databases from January 1, 2010, to December 31, 2022. We used specific keywords and inclusion/exclusion criteria centered on large animal models.

RESULTS

 Our review analyzed 84 pertinent articles, including four animal species: pigs, sheep, dogs, and nonhuman primates (NHPs). Eighty-five percent of the studies predominantly utilized porcine models. Meanwhile, sheep and dogs were less represented, making up only 2.5% of the total studies. Models with NHP were 10%. The most frequently used trauma models involved a combination of liver injury and femur fractures (eight studies), arterial hemorrhage (seven studies), and a combination of hemodilution and liver injury (seven studies). A wide array of coagulation parameters were employed to assess the efficacy of interventions in hemostasis and bleeding control.

CONCLUSIONS

 Recognizing the diverse strengths and weaknesses of large animal models is critical for trauma and hemorrhage research. Each model is unique and should be chosen based on how well it aligns with the specific scientific objectives of the study. By strategically considering each model's advantages and limitations, we can enhance our understanding of trauma and hemorrhage pathophysiology and further advance the development of effective treatments.

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.

Comparison of cardiorespiratory and anesthetic effects of ketamine-midazolam-xylazine-sufentanil and tiletamine-zolazepam-xylazine in miniature pigs

Effective and adequate anesthesia is conducive to better restrain for pigs during surgical or diagnostic procedures This study aimed to evaluate cardiorespiratory and anesthetic effects of ketamine-midazolam-xylazine-sufentanil or tiletamine-zolazepam-xylazine as general anesthetics in miniature pigs. In phase 1, one of the combinations was administered intramuscularly to miniature pigs. The KMXS protocol combined 10 mg kg^-1 ketamine, 0.5 mg kg^-1 midazolam, and 2 mg kg^-1 xylazine with 2 μg kg^-1 sufentanil. The TZX protocol combined 2.2 mg kg^-1 tiletamine, 2.2 mg kg^-1 zolazepam, and 1.4 mg kg^-1 xylazine. After treatment, the mean arterial pressure, systolic arterial pressure, diastolic arterial pressure, heart rate, respiratory rate, peripheral hemoglobin oxygen saturation, rectal temperature, and anesthesia quality were recorded. In phase 2, the feasibility of KMXS and TZX as general anesthetics were evaluated for pig castration. In phase 1, both drug combinations provided smooth induction with similar anesthetic effects. The KMXS protocol provided moderate anesthesia for 60–70 minutes in pigs, while the TZX protocol provided 30–45 minutes. In phase 2, castration was completed smoothly in all pigs with little fluctuation in physiological variables. The KMXS protocol is better for medium-term anesthesia, while the TZX protocol is preferable for short-term anesthesia in pigs.

Standardized porcine unilateral femoral nailing is associated with changes in PMN activation status, rather than aberrant systemic PMN prevalence

PURPOSE

Intramedullary nailing (IMN) of fractures is associated with increased rates of inflammatory complications. The pathological mechanism underlying this phenomenon is unclear. However, polymorphonuclear granulocytes (PMNs) seem to play an important role. We hypothesized that a femur fracture and standardized IMN in pigs is associated with altered appearance of PMNs in circulation and enhanced activation status of these cells.

METHODS

A porcine model including a femur fracture and IMN was utilized. Animals were randomized for control [anesthesia + mechanical ventilation only (A/MV)] and intervention [A/MV and unilateral femur fracture (FF) + IMN] conditions. PMN numbers and responsiveness, integrin (CD11b), L-selectin (CD62L) and Fcγ-receptor (CD16 and CD32)-expression levels were measured by flowcytometry of blood samples. Animals were observed for 72 h.

RESULTS

Circulatory PMN numbers did not differ between groups. Early PMN-responsiveness was retained after insult. PMN-CD11b expression increased significantly upon insult and peaked after 24 h, whereas CD11b in control animals remained unaltered (P = 0.016). PMN-CD16 expression levels in the FF + IMN-group rose gradually over time and were significantly higher compared with control animals, after 48 h (P = 0.016) and 72 h (P = 0.032). PMN-CD62L and CD32 expression did not differ significantly between conditions.

CONCLUSION

This study reveals that a femur fracture and subsequent IMN in a controlled setting in pigs is associated with enhanced activation status of circulatory PMNs, preserved PMN-responsiveness and unaltered circulatory PMN-presence. Indicating that monotrauma plus IMN is a specific and substantial stimulus for the cellular immune system. Early alterations of circulatory PMN receptor expression dynamics may be predictive for the intensity of the post traumatic response.

17α-Ethinyl estradiol-3-sulfate increases survival and hemodynamic functioning in a large animal model of combined traumatic brain injury and hemorrhagic shock: a randomized control trial

Background

Traumatic brain injury (TBI) and severe blood loss resulting in hemorrhagic shock (HS) represent leading causes of trauma-induced mortality, especially when co-occurring in pre-hospital settings where standard therapies are not readily available. The primary objective of this study was to determine if 17α-ethinyl estradiol-3-sulfate (EE-3-SO4) increases survival, promotes more rapid cardiovascular recovery, or confers neuroprotection relative to Placebo following TBI + HS.

Methods

All methods were approved by required regulatory agencies prior to study initiation. In this fully randomized, blinded preclinical study, eighty (50% females) sexually mature (190.64 ± 21.04 days old; 28.18 ± 2.72 kg) Yucatan swine were used. Sixty-eight animals received a closed-head, accelerative TBI followed by removal of approximately 40% of circulating blood volume. Animals were then intravenously administered EE-3-SO4 formulated in the vehicle at 5.0 mg/mL (dosed at 0.2 mL/kg) or Placebo (0.45% sodium chloride solution) via a continuous pump (0.2 mL/kg over 5 min). Twelve swine were included as uninjured Shams to further characterize model pathology and replicate previous findings. All animals were monitored for up to 5 h in the absence of any other life-saving measures (e.g., mechanical ventilation, fluid resuscitation).

Results

A comparison of Placebo-treated relative to Sham animals indicated evidence of acidosis, decreased arterial pressure, increased heart rate, diffuse axonal injury and blood–brain barrier breach. The percentage of animals surviving to 295 min post-injury was significantly higher for the EE-3-SO4 (28/31; 90.3%) relative to Placebo (24/33; 72.7%) cohort. EE-3-SO4 also restored pulse pressure more rapidly post-drug administration, but did not confer any benefits in terms of shock index. Primary blood-based measurements of neuroinflammation and blood brain breach were also null, whereas secondary measurements of diffuse axonal injury suggested a more rapid return to baseline for the EE-3-SO4 group. Survival status was associated with biological sex (female > male), as well as evidence of increased acidosis and neurotrauma independent of EE-3-SO4 or Placebo administration.

Conclusions

EE-3-SO4 is efficacious in promoting survival and more rapidly restoring cardiovascular homeostasis following polytraumatic injuries in pre-hospital environments (rural and military) in the absence of standard therapies. Poly-therapeutic approaches targeting additional mechanisms (increased hemostasis, oxygen-carrying capacity, etc.) should be considered in future studies.

Hemodynamic Effects of Cardiovascular Medications in a Normovolemic and Hemorrhaged Yorkshire-cross Swine Model

The Yorkshire-cross swine model is a valuable translational model commonly used to study cardiovascular physiologyand response to insult. Although the effects of vasoactive medications have been well described in healthy swine, the effects of these medications during hemorrhagic shock are less studied. In this study, we sought to expand the utility of the swine model by characterizing the hemodynamic changes that occurred after the administration of commonly available vasoactive medications during euvolemic and hypovolemic states. To this end, we anesthetized and established femoral arterial,central venous, and pulmonary arterial access in 15 juvenile Yorkshire-cross pigs. The pigs then received a series of rapidlymetabolized but highly vasoactive medications in a standard dosing sequence. After completion of this sequence, each pigunderwent a 30-mL/kg hemorrhage over 10 min, and the standard dosing sequence was repeated. We then used standard statisticaltechniques to compare the effects of these vasoactive medications on a variety of hemodynamic parameters betweenthe euvolemic and hemorrhagic states. All subjects completed the study protocol. The responses in the hemorrhagic state wereoften attenuated or even opposite of those in the euvolemic state. For example, phenylephrine decreased the mean arterialblood pressure during the euvolemic state but increased it in the hemorrhagic state. These results clarify previously poorlydefined responses to commonly used vasoactive agents during the hemorrhagic state in swine. Our findings also demonstratethe need to consider the complex and dynamic physiologic state of hemorrhage when anticipating the effects of vasoactivedrugs and planning study protocols.

The effectiveness of alprostadil in treating coronary microcirculation dysfunction following ST-segment elevation myocardial infarction in a pig model

Though alprostadil has been reported to improve the impaired microcirculation of patients with pulmonary arterial hypertension, its effectiveness as a treatment for coronary microvasculature dysfunction (CMD) following ST-segment elevation myocardial infarction (STEMI) is unknown. A total of 18 miniature pigs with CMD following STEMI were randomized into three groups that received an intracoronary injection of 5 ml of normal saline, 2 mg of nicorandil or 10 µg of alprostadil immediately after measurement of the index of microcirculatory resistance (IMR) and then an intravenous drip containing 5 ml of normal saline, 2 mg of nicorandil or 10 µg of alprostadil once a day for 6 days. The IMR, cardiac function using ultrasound, infarct areas and heparanase levels in infarct areas were measured and compared between the three groups. The IMR decreased markedly 10 min after alprostadil or nicorandil intracoronary injection (both P<0.05) but not following saline injection (P>0.05). After 7 days, the IMR was substantially lower in the alprostadil and nicorandil groups compared with the saline group (both P<0.05) and the ejection fraction was considerably higher in the alprostadil and nicorandil groups compared with the saline group (both P<0.05). Differences in infarct areas and the relative heparanase expression levels among the 3 groups were similar to the differences in the ejection fraction. No significant differences in the above assessment indexes were identified in the alprostadil and nicorandil groups. Alprostadil infusion improved coronary microcirculation function, reduced the infarct area and limited left ventricular dilatation in a pig coronary microvasculature dysfunction model following STEMI.

Internal Fixation Construct and Defect Size Affect Healing of a Translational Porcine Diaphyseal Tibial Segmental Bone Defect

BACKGROUND AND OBJECTIVE

Porcine translational models have become the gold-standard translational tool to study the effects of major injury and hemorrhagic shock because of their similarity to the human immunologic response to trauma. Segmental bone defects (SBDs) typically occur in warfighters with associated severe limb trauma. The purpose of this study was to develop a translational porcine diaphyseal SBD model in Yucatan minipigs (YMPs), which could be used in bone healing investigations that simulate injury-relevant conditions. We were specifically working toward developing a critical sized defect (CSD).

METHODS

We used an adaptive experimental design in which both 25.0 mm and 40.0 mm SBDs were created in the tibial mid-diaphysis in skeletally mature YMPs. Initially, eight YMPs were subjected to a 25.0 mm SBD and treated with intramedullary nailing (intramedullary nail [IMN] 25mm). Due to unanticipated wound problems, we subsequently treated four specimens with identical 25.0 mm defect with dual plating (open reduction with internal fixation [ORIF] 25mm). Finally, a third group of four YMPs with 40.0 mm defects were treated with dual plating (ORIF 40mm). Monthly radiographs were made until sacrifice. Modified Radiographic Union Score for Tibia fractures (mRUST) measurements were made by three trauma-trained orthopedic surgeons. CT scans of the tibias were used to verify the union results.

RESULTS

At 4 months post-surgery, mean mRUST scores were 11.7 (SD ± 1.8) in the ORIF 25mm YMPs vs. 8.5 (SD  ± 1.4) in the IMN 25mm YMPs (P < .0001). All four ORIF 25mm YMPs were clinically healed. In contrast, none of the IMN 25mm YMPs were clinically healed and seven of eight IMN 25mm YMPs developed delayed wound breakdown. All four of the ORIF 40mm YMPs had flail nonunions with complete hardware failure by 3 months after surgery and were sacrificed early. CT scanning confirmed that none of the IMN 25mm YMPs, none of the ORIF 40mm YMPs, and two of four ORIF 25mm YMPs were healed. A third ORIF 25mm specimen was nearly healed on CT scanning. Inter-rater and intra-rater reliability interclass coefficients using the mRUST scale were 0.81 and 0.80, respectively.

CONCLUSIONS

YMPs that had a 40 mm segment of bone removed from their tibia and were treated with dual plating did not heal and could be used to investigate interventions that accelerate bone healing. In contrast, a 25 mm SBD treated with dual plating demonstrated delayed but successful healing, indicating it can potentially be used to investigate bone healing adjuncts or conversely how concomitant injuries may impair bone healing. Pigs treated with IMN failed to heal and developed consistent delayed wound breakdown presumably secondary to chronic limb instability. The porcine YMP SBD model has the potential to be an effective translational tool to investigate bone healing under physiologically relevant injury conditions.

Bone Morphogenetic Protein-2 Rapidly Heals Two Distinct Critical Sized Segmental Diaphyseal Bone Defects in a Porcine Model

INTRODUCTION

Segmental bone defects (SBDs) are devastating injuries sustained by warfighters and are difficult to heal. Preclinical models that accurately simulate human conditions are necessary to investigate therapies to treat SBDs. We have developed two novel porcine SBD models that take advantage of similarities in bone healing and immunologic response to injury between pigs and humans. The purpose of this study was to investigate the efficacy of Bone Morphogenetic Protein-2 (BMP-2) to heal a critical sized defect (CSD) in two novel porcine SBD models.

MATERIALS AND METHODS

Two CSDs were performed in Yucatan Minipigs including a 25.0-mm SBD treated with intramedullary nailing (IMN) and a 40.0-mm SBD treated with dual plating (ORIF). In control animals, the defect was filled with a custom spacer and a bovine collagen sponge impregnated with saline (IMN25 Cont, n = 8; ORIF40 Cont, n = 4). In experimental animals, the SBD was filled with a custom spacer and a bovine collage sponge impregnated with human recombinant BMP-2 (IMN25 BMP, n = 8; ORIF40 BMP, n = 4). Healing was quantified using monthly modified Radiographic Union Score for Tibia Fractures (mRUST) scores, postmortem CT scanning, and torsion testing.

RESULTS

BMP-2 restored bone healing in all eight IMN25 BMP specimens and three of four ORIF40 BMP specimens. None of the IMN25 Cont or ORIF40 Cont specimens healed. mRUST scores at the time of sacrifice increased from 9.2 (±2.4) in IMN25 Cont to 15.1 (±1.0) in IMN25 BMP specimens (P < .0001). mRUST scores increased from 8.2 (±1.1) in ORIF40 Cont to 14.3 (±1.0) in ORIF40 BMP specimens (P < .01). CT scans confirmed all BMP-2 specimens had healed and none of the control specimens had healed in both IMN and ORIF groups. BMP-2 restored 114% and 93% of intact torsional stiffness in IMN25 BMP and ORIF40 BMP specimens.

CONCLUSIONS

We have developed two porcine CSD models, including fixation with IMN and with dual-plate fixation. Porcine models are particularly relevant for SBD research as the porcine immunologic response to injury closely mimics the human response. BMP-2 restored healing in both CSD models, and the effects were evident within the first month after injury. These findings support the use of both porcine CSD models to investigate new therapies to heal SBDs.

Determination of indicators allowing to evaluating the hemostatic activity of chitosan without a biological experiment

The biopolymer chitosan is widely used for the development of local hemostatic agents. However, the physicochemical parameters of chitosan that determine its hemostatic properties have not yet been determined. Standard quality control of chitosan-containing raw materials and medical products on its basis do not allow us to make a conclusion about the effectiveness of their use for stopping bleeding. The most reliable method for assessing hemostatic activity remains in vivo experiment on large animals. The aim of this study was to determine additional physicochemical parameters of chitosan, which would make it possible to predict its hemostatic activity without conducting a biological experiment. In this work, using the methods of nuclear magnetic resonance spectroscopy, spectrophotometry and viscometry, it has been shown that the ability to initiate hemostasis is depending of the molecular weight and degree of deacetylation of chitosan, but not enough linearly. The hemostatic properties in vitro increases in a series of samples with a relatively constant molecular weight with an increase in the degree of deacetylation. As well as in a series with the same degree of deacetylation with an increase in molecular weight. However, at molecular weight values more than 300 kDa, the viscosity of the polymer causes the opposite effect: with an increase in the degree of deacetylation, the hemostatic activity decreases. The best ability to initiate hemostasis have chitosan samples with a degree of deacetylation of 90.0%–97.4% and molecular weight 145.7–284.7 kDa, in which at pH of solution close to physiological, a significant part of the molecules transitioned from conformation state rigid rod to state globule. It was accompanied by an abrupt change in light transmission of the solution. It was concluded, that it is possible to study conformational states by spectrophotometry to assess the hemostatic activity of chitosan samples without performing biological experiment.

The future of basic science in orthopaedics and traumatology: Cassandra or Prometheus?

Orthopaedic and trauma research is a gateway to better health and mobility, reflecting the ever-increasing and complex burden of musculoskeletal diseases and injuries in Germany, Europe and worldwide. Basic science in orthopaedics and traumatology addresses the complete organism down to the molecule among an entire life of musculoskeletal mobility. Reflecting the complex and intertwined underlying mechanisms, cooperative research in this field has discovered important mechanisms on the molecular, cellular and organ levels, which subsequently led to innovative diagnostic and therapeutic strategies that reduced individual suffering as well as the burden on the society. However, research efforts are considerably threatened by economical pressures on clinicians and scientists, growing obstacles for urgently needed translational animal research, and insufficient funding. Although sophisticated science is feasible and realized in ever more individual research groups, a main goal of the multidisciplinary members of the Basic Science Section of the German Society for Orthopaedics and Trauma Surgery is to generate overarching structures and networks to answer to the growing clinical needs. The future of basic science in orthopaedics and traumatology can only be managed by an even more intensified exchange between basic scientists and clinicians while fuelling enthusiasm of talented junior scientists and clinicians. Prioritized future projects will master a broad range of opportunities from artificial intelligence, gene- and nano-technologies to large-scale, multi-centre clinical studies. Like Prometheus in the ancient Greek myth, transferring the elucidating knowledge from basic science to the real (clinical) world will reduce the individual suffering from orthopaedic diseases and trauma as well as their socio-economic impact.

Survival Rates and Biomarkers in a Large Animal Model of Traumatic Brain Injury Combined With Two Different Levels of Blood Loss

INTRODUCTION

The pathology resulting from concurrent traumatic brain injury (TBI) and hemorrhagic shock (HS; TBI+HS) are leading causes of mortality and morbidity worldwide following trauma. However, the majority of large animal models of TBI+HS have utilized focal/contusional injuries rather than incorporating the types of brain trauma (closed-head injury caused by dynamic acceleration) that typify human injury.

OBJECTIVE

To examine survival rates and effects on biomarkers from rotational TBI with two levels of HS.

METHODS

Twenty-two sexually mature Yucatan swine (30.39 ± 2.25 kg; 11 females) therefore underwent either Sham trauma procedures (n = 6) or a dynamic acceleration TBI combined with either 55% (n = 8) or 40% (n = 8) blood loss in this serial study.

RESULTS

Survival rates were significantly higher for the TBI+40% (87.5%) relative to TBI+55% (12.5%) cohort, with the majority of TBI+55% animals expiring within 2 h post-trauma from apnea. Blood-based neural biomarkers and immunohistochemistry indicated evidence of diffuse axonal injury (increased NFL/Aβ42), blood-brain barrier breach (increased immunoglobulin G) and inflammation (increased glial fibrillary acidic protein/ionized calcium-binding adaptor molecule 1) in the injured cohorts relative to Shams. Invasive hemodynamic measurements indicated increased shock index and decreased pulse pressure in both injury cohorts, with evidence of partial recovery for invasive hemodynamic measurements in the TBI+40% cohort. Similarly, although both injury groups demonstrated ionic and blood gas abnormalities immediately postinjury, metabolic acidosis continued to increase in the TBI+55% group ∼85 min postinjury. Somewhat surprisingly, both neural and physiological biomarkers showed significant changes within the Sham cohort across the multi-hour experimental procedure, most likely associated with prolonged anesthesia.

CONCLUSION

Current results suggest the TBI+55% model may be more appropriate for severe trauma requiring immediate medical attention/standard fluid resuscitation protocols whereas the TBI+40% model may be useful for studies of prolonged field care.

Instant intra-operative neutropenia despite the emergence of banded (CD16dim/CD62Lbright) neutrophils in peripheral blood - An observational study during extensive trauma-surgery in pigs

INTRODUCTION

Deregulation of polymorphonuclear neutrophils (PMNs) is an essential step in the development of inflammatory complications upon trauma. Different neutrophil subtypes have been identified recently, however, the role of neutrophil subtypes in immunoregulation upon trauma is unclear. We hypothesize that extensive trauma surgery causes instant progressive heterogeneity of the blood neutrophil pool, and increased appearance of young (CD16^dim/CD62L^bright) neutrophils in peripheral blood.

MATERIAL AND METHODS

A standardized extensive thoraco-abdominal porcine trauma surgery model was utilized, and 12 animals were included. Blood was collected at defined timepoints and neutrophil numbers and subtypes were studied by flowcytometry. Neutrophil subtypes were identified by differences in cell surface expression levels of CD16 (FcγRIII) and CD62L (L-selectin). Porcine neutrophil subtypes were further characterized after flow sorting.

RESULTS

Eleven animals survived the 3-hour surgical protocol. Neutrophil numbers dropped significantly from a mean of 8,6 ± 3,5 × 10⁶ to 2,4 ± 1,8 × 10⁶ cells/ml during 180 min, (p<0.001). Simultaneously, the blood PMN population became increasingly heterogeneous due to the appearance of new neutrophil subtypes. Cell sorting experiments and cytological analysis revealed that these porcine subtypes had specific morphological characteristics, mimicking their human counterparts. At baseline, 88% ± 1 percent of circulatory PMNs comprised of mature (CD16^bright/CD62L^bright) PMNs, while at 3 h the blood PMN pool consisted of 59% ± 2 percent of mature subtypes (p<0.001). Despite a marked drop in neutrophil levels during surgery, absolute and relative numbers of banded (CD16^dim/CD62L^bright) neutrophils continued to rise throughout surgery.

CONCLUSION

Standardized extensive trauma surgery was associated with instant progressive neutropenia and increased heterogeneity of the blood neutrophil pool. Furthermore, three different neutrophil subsets in peripheral porcine blood were identified over the course of surgery. Further studies should clarify their precise role in the development of early organ failure upon extensive trauma surgery. This for the first time exemplifies experimentally the time constraints and impact of damage control surgery after severe trauma.

Pulse Arrival Time Is Associated With Hemorrhagic Volume in a Porcine Model: A Pilot Study

BACKGROUND

Hemorrhage is a major cause of preventable death worldwide, and early identification can be lifesaving. Pulse wave contour analysis has previously been used to infer hemodynamic variables in a variety of settings. We hypothesized that pulse arrival time (PAT), a form of pulse wave contour analysis which is assessed via electrocardiography (ECG) and photoplethysmography (PPG), is associated with hemorrhage volume.

METHODS

Yorkshire-Cross swine were randomized to hemorrhage (30 mL/kg over 20 minutes) vs. control. Continuous ECG and PPG waveforms were recorded with a novel monitoring device, and algorithms were developed to calculate PAT and PAT variability throughout the respiratory cycle, termed "PAT index" or "PAT_I." Mixed effects models were used to determine associations between blood loss and PAT and between blood loss and PAT_I to account for clustering within subjects and investigate inter-subject variability in these relationships.

RESULTS

PAT and PAT_I data were determined for ∼150 distinct intervals from five subjects. PAT and PAT_I were strongly associated with blood loss. Mixed effects modeling with PAT alone was substantially better than PAT_I alone (R2 0.93 vs. 0.57 and Akaike information criterion (AIC) 421.1 vs. 475.5, respectively). Modeling blood loss with PAT and PAT_I together resulted in slightly improved fit compared to PAT alone (R2 0.96, AIC 419.1). Mixed effects models demonstrated significant inter-subject variability in the relationships between blood loss and PAT.

CONCLUSIONS

Findings from this pilot study suggest that PAT and PAT_I may be used to detect blood loss. Because of the simple design of a single-lead ECG and PPG, the technology could be packaged into a very small form factor device for use in austere or resource-constrained environments. Significant inter-subject variability in the relationship between blood loss and PAT highlights the importance of individualized hemodynamic monitoring.

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.

Engagement of Posthemorrhagic Shock Mesenteric Lymph on CD4+ T Lymphocytes In Vivo and In Vitro

BACKGROUND

Immune dysfunction is associated with posthemorrhagic shock mesenteric lymph (PHSML) return. To determine the proliferation and cytokine production capacity of CD4⁺ T lymphocytes, the effect of PHSML drainage on spleen CD4⁺ T lymphocytes in a mouse model of hemorrhagic shock was assessed.

METHODS

The normal spleen CD4⁺ T lymphocytes were in vitro incubated with either drained normal mesenteric lymph (NML), PHSML during hypotension (PHSML-H), or PHSML from 0 h to 3 h after resuscitation (PHSML-R) to verify direct proliferation effects of PHSML.

RESULTS

Hemorrhagic shock led to reduction of proliferation and mRNA expression of interleukin 2 (IL-2) and IL-2 receptor in CD4⁺ T lymphocytes and to decrease in IL-2 and interferon γ (IFN-γ) levels in supernatants. In contrast, the interleukin-4 levels were increased. These effects were reversed by PHSML drainage. Moreover, NML incubation promoted CD4⁺ T lymphocyte proliferation, whereas both PHSML-H and PHSML-R treatment had a biphasic effects on CD4⁺ T lymphocyte proliferation, exhibiting an enhanced effect at early stages and an inhibitory effect at later stages. Compared with NML, PHSML-H increased IL-2 expression at 12 h, but decreased expression of both IL-2 and IFN-γ at 24 h. By contrast, PHSML-R induced significant increases in IL-2 and IFN-γ levels at 24 h. Interleukin-4 expression in CD4⁺ T lymphocytes was reduced at 12 h, but augmented at 24 h after incubation with either PHSML-H or PHSML-R.

CONCLUSIONS

The results indicate that PHSML has a direct inhibitory effect on CD4⁺ T lymphocyte proliferation that induces an inflammatory response, which is associated with cellular immune dysfunction.

Addition of terlipressin to initial volume resuscitation in a pediatric model of hemorrhagic shock improves hemodynamics and cerebral perfusion

Hemorrhagic shock is one of the leading causes of mortality and morbidity in pediatric trauma. Current treatment based on volume resuscitation is associated to adverse effects, and it has been proposed that vasopressors may be used in the pharmacological management of trauma. Terlipressin has demonstrated its usefulness in other pediatric critical care scenarios and its long half-life allows its use as a bolus in an outpatient critical settings. The aim of this study was to analyze whether the addition of a dose of terlipressin to the initial volume expansion produces an improvement in hemodynamic and cerebral perfusion at early stages of hemorrhagic shock in an infant animal model. We conducted an experimental randomized animal study with 1-month old pigs. After 30 minutes of hypotension (mean arterial blood pressure [MAP]<45 mmHg) induced by the withdrawal of blood over 30 min, animals were randomized to receive either normal saline (NS) 30 mL/kg (n = 8) or a bolus of 20 mcg/kg of terlipressin plus 30 mL/kg of normal saline (TP) (n = 8). Global hemodynamic and cerebral monitoring parameters, brain damage markers and histology samples were compared. After controlled bleeding, significant decreases were observed in MAP, cardiac index (CI), central venous pressure, global end-diastolic volume index (GEDI), left cardiac output index, SvO₂, intracranial pressure, carotid blood flow, bispectral index (BIS), cerebral perfusion pressure (CPP) and increases in systemic vascular resistance index, heart rate and lactate. After treatment, MAP, GEDI, CI, CPP and BIS remained significantly higher in the TP group. The addition of a dose of terlipressin to initial fluid resuscitation was associated with hemodynamic improvement, intracranial pressure maintenance and better cerebral perfusion, which would mean protection from ischemic injury. Brain monitoring through BIS was able to detect changes caused by hemorrhagic shock and treatment.

Review of Animal Models of Comorbidities in Fracture-Healing Research

There is clinical evidence that patient-specific comorbidities like osteoporosis, concomitant tissue injury, and ischemia may strongly interfere with bone regeneration. However, underlying mechanisms are still unclear. To study these mechanisms in detail, appropriate animal models are needed. For decades, bone healing has been studied in large animals, including dogs, rabbits, pigs, or sheep. However, large animal models display a limited ability to study molecular pathways and cellular functions. Therefore in recent years, mice and rats have become increasingly popular as a model organism for fracture healing research due to the availability of molecular analysis tools and transgenic models. Both large and small animals can be used to study comorbidities and risk factors, modelling the human clinical situation. However, attention has to be paid when choosing an appropriate model due to species differences between large animals, rodents, and humans. This review focuses on large and small animal models for the common comorbidities ischemic injury/reduced vascularization, osteoporosis, and polytrauma, and critically discusses the translational and molecular aspects of these models. Here, we review material which was presented at the workshop "Animal Models of Comorbidities in Fracture Healing Research" at the 2019 ORS Annual Meeting in Austin Texas. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2491-2498, 2019.

Single Low Dose of Human Recombinant Antithrombin (ATryn) has no Impact on Endotoxin-Induced Disseminated Intravascular Coagulation: An Experimental Randomized Open Label Controlled Study

BACKGROUND

Antithrombin (AT) III physiological levels are decreased during septic shock and supplementation therapy could therefore be beneficial.

OBJECTIVE

We hypothesized that the use of recombinant human AT could reduce disseminated intravascular coagulation (DIC) occurrence.

METHODS

We conducted a randomized open label controlled experimental study. Ten female "Large White" pigs were challenged with i.v. infusion of Escherichia coli endotoxin. Two groups of 5 pigs were randomly assigned to receive either recombinant human AT 100 U/kg over 30 min (ATryn group) or 0.9% saline (control group). AT III levels, coagulation, hemostasis, inflammation parameters, hemodynamics, and microcirculatory parameters were measured over a 5-h period. Immediately after euthanasia, kidneys were withdrawn for histology evaluation. Statistical analysis was performed with nonparametric tests and Dunn's test for multiple comparisons.

RESULTS

AT III activity was significantly higher in the ATryn group than in the control group from 60% (213% [203-223] vs. 104% [98-115], P = 0.008, respectively) to 300 min (115% [95-124] vs. 79% [67-93], P = 0.03). Recombinant human AT supplementation had no impact on hemodynamics, microcirculatory parameters, and sequential changes of coagulation parameters (platelet count, fibrinogen level, thrombin-AT complexes, and von Willebrand factor). Interleukin 6 and tumor necrosis factor α values were statistically the same for both groups throughout the study. Percentage of thrombosed glomeruli and percentage of thrombosed capillary in glomerulus were not significantly different between both groups.

CONCLUSIONS

In our model of endotoxic shock, a single low dose of recombinant human AT did not prevent DIC occurrence, severity, inflammatory profile, or hemodynamic alterations.

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.

Concomitant chest trauma and traumatic brain injury, biomarkers correlate with worse outcomes

BACKGROUND

Clinical data are lacking on the influence of chest trauma on the secondary injury process after traumatic brain injury (TBI), with some data suggesting that multiple trauma may worsens brain injury. Blunt chest trauma and TBI represent the two major single injury entities with the highest risk of complications and are potential biomarker targets.

METHODS

Trauma patients with severe TBI were enrolled. Serum biomarker levels were obtained every 6 hours for 72 hours. Baseline, 6 hours and 24 hours CT head scans were evaluated. Neurologic worsening was defined as increased contusions, ischemia, compression of basal cisterns, and/or midline shift. The TBI patients with chest injury (Abbreviated Injury Scale chest score ≥1) and those without chest injury were compared. Wilcoxon rank sum test, univariate logistic regression and receiver operating characteristic were reported.

RESULTS

Fifty-seven patients. Mean age of 40.5 years. Median motor Glasgow Coma Scale score at admission and 24 hours was 3 (interquartile range, 1-5) and 5 (interquartile range, 3-5). Of the patients enrolled, 12.2% patients underwent craniotomy within 6 hours from the time of admission and 22.8% within 12 hours. Patients with chest trauma, 24.5% had a chest Abbreviated Injury Scale score of 3 or greater, and 73.6% sustained blunt chest trauma. Stratifying TBI patients with and without chest injury revealed higher mean levels of IL-4, IL-5, IL-8, and IL-10 and lower mean IFN-γ and IL-7 levels in patient with chest injury. IL-7 levels adjusted for chest injury predicted neurological worsening with area under the receiver operating characteristic of 0.59 (p value = 0.011). The TBI and chest trauma patients' IL-4 and neuron-specific enolase levels were predictive of mortality (area under the receiver operating characteristic of 0.67 and 0.63, p = 0.0001, 0.003), respectively.

CONCLUSION

Utilizing biomarkers for early identification of patients with TBI and chest trauma has the capability of modifying adverse factors affecting morbidity and mortality in this subset of TBI patients.

LEVEL OF EVIDENCE

Level III.

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.

Intravenous injection of post-hemorrhagic shock mesenteric lymph induces multiple organ injury in rats

Post-hemorrhagic shock mesenteric lymph (PHSML) has an important role in the multiple organ injuries caused by severe shock. The current study investigated whether intravenous injection of PHSML induces organ injury in normal rats. Following the establishment of hemorrhagic shock in donor rats (40±2 mmHg, 3 h), PHSML was drained during hypotension at 1-3 h and then injected to normal rats through the femoral vein within 30 min. The mean arterial pressure (MAP) was measured, and samples were obtained for analysis of histology and biochemical indices at 2.5 h post-PHSML administration. PHSML administration resulted in a significant decrease in MAP at the early and late stage of the experiment. Structural damage of the lung, kidney, heart and liver was also observed, and the levels of urea, creatinine, aspartate aminotransferase, total bile acid and creatine kinase MB isoenzyme were increased in the plasma. Additionally, PHSML injection significantly increased the levels of trypsin, tumor necrosis factor-α (TNF-α), intercellular adhesion molecule-1 and receptor of advanced glycation end-products in the plasma, malondialdehyde in the lung and myocardium, and TNF-α in the lung, kidney, myocardium and liver. Intravenous injection of PHSML induced multiple organ injury in normal rats via increases in trypsin activity, inflammatory factors and free radical production. The findings indicate that PHSML return is an important contributor to organ damage following hemorrhagic shock.

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.

The impact of septic stimuli on the systemic inflammatory response and physiologic insult in a preclinical non-human primate model of polytraumatic injury

BACKGROUND

Established animal trauma models are limited in recapitulating the pathophysiology of human traumatic injury. Herein, we characterize the physiologic insult and inflammatory response in two clinically relevant non-human primate (NHP) trauma models.

METHODS

Mauritian Cynomolgus Macaques underwent either a laparoscopic closed abdomen liver injury (laparoscopic 60% left-lobe hepatectomy) in an established uncontrolled severe hemorrhage model (THM), or a polytrauma hemorrhage model (PHM) involving combined liver and bowel injury, uncontrolled severe hemorrhage as well as an open full-thickness cutaneous flank wound. Fixed volume resuscitation strategies were employed in the THM and goal directed resuscitation was used in the PHM. Complete peripheral blood and critical clinical chemistry parameters, serum biomarkers of systemic inflammation, tissue perfusion parameters, as well as survival, were compared between the models throughout the 2-week study period.

RESULTS

NHPs in both the THM (n = 7) and the PHM (n = 21) demonstrated tissue hypoperfusion (peak lactate 6.3 ± 0.71 mmol/L) with end organ injury (peak creatinine 3.08 ± 0.69 mg/dL) from a similar liver injury (60% left hemi-hepatectomy), though the PHM NHPs had a significantly higher blood loss (68.1% ± 12.7% vs. 34.3% ± 2.3%, p = 0.02), lower platelet counts (59 ± 25 vs. 205 ± 46 K/uL, p = 0.03) and a trend towards higher mortality (90.5% vs. 33.3%, p = 0.09). The inflammatory response was robust in both models with peak cytokine (IL-6 > 6000-fold above baseline) and peak leukocyte values (WBC 27 K/uL) typically occurring around t = 240 min from the time of hepatic injury. A more robust systemic inflammatory response was appreciated in the PHM resulting in marked elevations in peak serum IL-6 (7887 ± 2521 pg/mL vs.1076 ± 4833 pg/mL, p = 0.02), IL-1ra (34,499 ± 5987 pg/mL vs. 2511 ± 1228 pg/mL, p < 0.00), and IL-10 (13,411 pg/mL ± 5598 pg/mL vs. 617 pg/mL ± 252 pg/mL, p = 0.03).

CONCLUSION

This comparative analysis provides a unique longitudinal perspective on the post-injury inflammatory response in two clinically relevant models, and demonstrates that the addition of septic stimuli to solid organ injury increases both the hemorrhagic insult and inflammatory response.

Nitric Oxide Regulates The Lymphatic Reactivity Following Hemorrhagic Shock Through Atp-Sensitive Potassium Channel

Lymphatic reactivity has been shown to exhibit a biphasic change following hemorrhagic shock, and nitric oxide (NO) is involved in this process. However, the precise mechanism responsible for NO regulation of the lymphatic reactivity along with the progression of hemorrhagic shock is unclear. Therefore, the present study was to investigate how NO participates in regulating the shock-induced biphasic changes in lymphatic reactivity and its underlying mechanisms. First, the expressions or contents of inducible NO synthase, nitrite plus nitrate, and elements of cAMP-PKA-KATP and cGMP-PKG-KATP pathway in thoracic ducts tissue were assessed. The results revealed that levels of nitrite plus nitrate, cAMP, cyclic guanosine monophosphate (cGMP), p-PKA, and p-PKG were increased gradually along with the process of shock. Second, the roles of cAMP-PKA-KATP and cGMP-PKG-KATP in NO regulating lymphatic response to gradient substance P were evaluated with an isolated lymphatic perfusion system. The results showed that the NOS substrate (L-Arg), PKA donor (8-Br-cAMP) decreased the reactivity of shock 0.5 h-lymphatics, and that the PKA inhibitor (H-89) and KATP inhibitor (glibenclamide) restrained the effects of L-Arg while glibenclamide abolished the effects of 8-Br-cAMP. Meanwhile, NOS antagonist (L-NAME), protein kinase G (PKG) inhibitor (KT-5823), and soluble guanylate cyclase inhibitor (ODQ) increased the reactivity of shock 2 h-lymphatics, whereas KATP opener (pinacidil) inhibited these elevated effects induced by either L-NAME, ODQ, or KT-5823. Taken together, these results indicate that NO regulation of lymphatic reactivity during shock involves both cAMP-PKA-KATP and cGMP-PKG-KATP pathways. These findings have potential significance for the treatment of hemorrhagic shock through regulating lymphatic reactivity.

Sodium lactate improves renal microvascular thrombosis compared to sodium bicarbonate and 0.9% NaCl in a porcine model of endotoxic shock: an experimental randomized open label controlled study

Background

Sodium lactate seemed to improve fluid balance and avoid fluid overload. The objective of this study was to determine if these beneficial effects can be at least partly explained by an improvement in disseminated intravascular coagulation (DIC)-associated renal microvascular thrombosis.

Methods

Ancillary work of an interventional randomized open label controlled experimental study. Fifteen female “Large White” pigs (2 months old) were challenged with intravenous infusion of E. coli endotoxin. Three groups of five animals were randomly assigned to receive different fluids: a treatment group received sodium lactate 11.2% (SL group); an isotonic control group received 0.9% NaCl (NC group); a hypertonic control group, with the same amount of osmoles and sodium than SL group, received sodium bicarbonate 8.4% (SB group). Glomerular filtration rate (GFR) markers, coagulation and inflammation parameters were measured over a 5-h period. Immediately after euthanasia, kidneys were withdrawn for histological study. Statistical analysis was performed with nonparametric tests and the Dunn correction for multiple comparisons. A p < 0.05 was considered significant.

Results

The direct immunofluorescence study revealed that the percentage of capillary sections thrombosed in glomerulus were significantly lesser in SL group [5 (0–28) %] compared to NC [64 (43–79) %, p = 0.01] and SB [64 (43–79), p = 0.03] groups. Alterations in platelet count and fibrinogen level occurred earlier and were significantly more pronounced in both control groups compared to SL group (p < 0.05 at 210 and 300 min). The increase in thrombin–antithrombin complexes was significantly higher in NC [754 (367–945) μg/mL; p = 0.03] and SB [463 (249–592) μg/mL; p = 0.03] groups than in SL group [176 (37–265) μg/mL]. At the end of the experiment, creatinine clearance was significantly higher in SL group [55.46 (30.07–67.85) mL/min] compared to NC group [1.52 (0.17–27.67) mL/min, p = 0.03].

Conclusions

In this study, we report that sodium lactate improves DIC-associated renal microvascular thrombosis and preserves GFR. These findings could at least partly explain the better fluid balance observed with sodium lactate infusion.

Inflammatory Profile in Response to Uncontrolled Hemorrhage in a Non-Human Primate (Rhesus Macaque) Model

BACKGROUND

Uncontrolled hemorrhage (UH), the leading cause of potentially survivable combat-related death, elicits a deleterious inflammatory response. Our group previously reported an increased secretion of pro-inflammatory cytokines in a novel non-human primate model of UH; however, to better understand the molecular profile of the inflammatory response to UH, we performed a comprehensive evaluation of inflammation at the proteomic and transcriptomic level.

METHODS

Anesthetized rhesus macaques (n = 8) underwent UH by 60% left lobe hepatectomy T = 0 min. At T = 5 min, animals received 11 mL of 5% albumin followed by normal saline infusion to a total resuscitation volume of 20 mL/kg by T = 120 min. Blood (T = 0, 5, 20, 120, 480 min) was collected for qPCR and multiplex cytokine quantification. Results from each non-human primate (NHP) per time-point are shown. Statistical analysis by one-way ANOVA with repeated measures, P <0.05 was considered significant.

RESULTS

Luminex analysis in serum revealed significant up-regulation compared with baseline of 8 cytokines/chemokines starting T = 120 min postinjury and significant down-regulation of 4 cytokines/chemokines as early as T = 20 min postinjury. Gene expression analysis in white blood cells uncovered 10 genes that were up-regulated greater than 3-fold compared with baseline and 29 genes that were down-regulated greater than 3-fold.

CONCLUSION

The present study confirms the presence of systemic inflammation after UH at the proteomic and transcriptomic level providing insight into the inflammatory mediators that are involved as well as their kinetics following UH. The data demonstrates that NHP hemorrhage models may be suitable for evaluating therapeutics to control inflammation following hemorrhage.

Thoracic trauma now and then: A 10 year experience from 16,773 severely injured patients

Background and purpose

Thoracic trauma remains to be a relevant injury to the polytraumatised patient. However, literature regarding how far changes in clinical guidelines for pre- and in-hospital trauma management and diagnostic procedures affect the outcome of multiple injured patients with severe chest injury during a long-term observation period is sparse.

Methods

Multiple traumatised patients (age≥16y) documented in the TraumaRegister DGU^® (TR-DGU) from January 1^st 2005 to December 31^st 2014 with severe chest trauma (AIS≥3) were included in this study. Demographic data, the pattern of injury, injury severity, radiographic emergency procedures, indication for intubation, duration of mechanical ventilation, emergency surgery, occurrence of complications and mortality were evaluated per year and over time.

Results

A total of 16,773 patients were analysed. The use of whole body computer tomography increased (p<0.001), while the incidence of plain x-rays decreased (p<0.001). Furthermore, incidence of AIS_Thorax = 3 graded injuries increased (p<0.001) while AIS_Thorax = 4 decreased (p<0.001). Both, rate of patients being intubated at the time of ICU admission decreased (p<0.001) and the time of mechanical ventilation decreased (p<0.001). Additionally, need for emergency surgery, lung failure, sepsis, and multi organ failure all decreased (p<0.001). However, mortality remained unchanged.

Interpretation

Severity of severe chest trauma and associated complications decreased while diagnostics and treatment improved over time. However, mortality remained unchanged. Our results are in line with those expected in the context of the incidence of CT diagnostics, which has increased parallel to the clinical outcome Thus, our data demonstrate a positive trend in the treatment of patients with severe chest 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.

Traumatic Brain Injury and Polytrauma in Theaters of Combat: The Case for Neurotrauma Resuscitation?

Polytrauma associated with traumatic brain injury (TBI) is defined as a concurrent injury to the brain and one or more body areas or organ systems that results in physical, cognitive, and psychosocial impairments. Consequently, polytrauma accompanied by TBI presents a unique challenge for emergency medicine, in particular, to those associated with the austere environments encountered in military theaters of operation and the logistics of en-route care. Here, we attempt to put needed focus on this medical emergency, specifically addressing the problem of an exsanguinating polytrauma requiring fluid resuscitation complicated by TBI. Critical questions to consider are the following: (1) What is the optimal resuscitation fluid for these patients? (2) In defining the resuscitation fluid, what considerations must be given with regard to the very specific logistics of military operations? and (3) Can treatment of the brain injury be initiated in parallel with resuscitation practices. Recognizing the immense clinical and experimental complexity of this problem, our goal was to encourage research that embraces with high-fidelity 'combined' animal models of polytrauma and TBI with an objective toward elucidating safe and effective neurotherapeutic resuscitation protocols.

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

BACKGROUND

An animal polytrauma model was developed, including trunk and extremity injuries combined with hemorrhagic shock and a prolonged post-traumatic phase. This could be useful for the assessment of different therapeutic approaches during intensive care therapy.

METHODS

A standardized polytrauma including lung contusion, liver laceration and lower leg fracture was applied in 25 pigs. They underwent controlled haemorrhage either with a blood volume loss of 45 % and a median arterial pressure (MAP) <30 mmHg/90 min (group L, n = 15) or a 50 % blood loss of and an MAP <25 mmHg/120 min (group H, n = 10). Five non-traumatized pigs served as a control (group C). Subsequently, intensive care treatment was given for an observational period of 48 h.

RESULTS

Both trauma groups showed signs of shock and organ injury (heart rate, MAP and lactate). The frequency of cardiopulmonary resuscitation (CPR) and lung injury was directly related to the severity of the haemorrhagic shock (CPR-group L: 4 of 15 pigs, group H: 4 of 10 pigs; Respiratory failure-group L: 3 of 13, group H: 3 of 9. There was no difference in mortality between trauma groups.

CONCLUSION

The present data suggest that our model reflects the mortality and organ failure of polytrauma in humans during shock and the intensive care period. This suggests that the experimental protocol could be useful for the assessment of therapeutic approaches during the post-traumatic period.

Current Concepts in Orthopedic Management of Multiple Trauma

Multiple trauma patients frequently present challenging clinical scenarios with musculoskeletal injuries being the most common indications for surgical procedures in these patients. Despite our substantial knowledge, a universally approved objective definition for “multiple trauma” is yet to be delineated. Several controversial aspects of economics, pathophysiology, animal models, diagnosis, management and outcome of patients with multiple trauma have recently been explored and although some progress has been made, it seems that the available evidence is still inconclusive in some occasions. This manuscript revisits several current concepts of multiple trauma that have been the focus of recent investigation. We aim to provide the reader with an updated perspective based on the most recently published literature in the field of multiple trauma.

Dried platelets in a swine model of liver injury

INTRODUCTION

Lyophilization may facilitate production of a safe, portable, easily storable, and transportable source of platelets for bleeding patients. The objective of this study was to examine the impact of lyophilized human and porcine platelets in a swine liver injury model of nonsurgical hemorrhage.

METHODS

Anesthetized pigs (40 kg) had a controlled 35% total blood volume bleed from the right jugular vein followed by cooling to 35°C and resuscitation with Ringer's lactate to achieve a 3:1 blood withdrawal resuscitation. Through a midline laparotomy, the liver was injured with two standardized 5 × 5-cm grids with lacerations 1 cm apart and 0.5 cm deep. After 2 min of uncontrolled hemorrhage, the animals were treated with placebo (n = 5), lyophilized human (n = 5, HP), or swine platelets (n = 5, SP). At 15 min, shed blood was calculated. The animals then underwent abdominal closure. At 48 h, the animals were killed for histopathologic evaluation of the lung, kidney, and heart.

RESULTS

Intraoperative blood loss at 15 min was significantly higher in the HP arm (SP: 4.9 ± 2.9 mL/kg, HP: 12.3 ± 4.7 mL/kg, and control: 6.1 ± 2.5 mL/kg; P = 0.013). Mortality at 48 h was 20% in all three arms, due to uncontrolled intra-abdominal bleeding. At the time the animals were killed, SP animals had a significantly higher hematocrit (SP: 22.0% ± 3.0%, HP: 15.1% ± 4.9%, and control: 13.9% ± 0.6%; P = 0.026). No significant difference was found in platelet count (SP: 319.3 ± 62.1 × 10(3)/µL, HP:361.5 ± 133.6 × 10(3)/µL, and control: 242.7 ± 42.5 × 10(3)/µL; P = 0.259). Histopathology of kidneys, lungs, and heart demonstrated no evidence of thromboembolic complications.

CONCLUSION

In this swine model of liver injury, human lyophilized platelets increased intraoperative blood loss. With the use of species-specific lyophilized platelets, however, this effect was abolished, with a decrease in blood loss at 48 h after injury.

Impact of haemorrhagic shock intensity on the dynamic of alarmins release in porcine poly-trauma animal model

PURPOSE

Traumatic insults result in an altered inflammatory response, in which alarmins release has a central role. The impact of haemorrhagic shock intensity on the long-term kinetics of alarmins is not yet fully elucidated. We investigated these aspects in a combined trauma (chest, abdominal, and extremities injury) porcine model with different severities and durations of haemorrhagic shock.

METHODS

After induction of combined trauma (tibia fracture, lung contusion, and liver laceration), haemorrhagic shock was induced at different intensities: moderate haemorrhage (MH; n = 15): mean arterial pressure (MAP) <30 ± 5 mmHg [maximum loss of total blood volume (TBVmax): 45 %] for 90 min, and severe haemorrhage (SH; n = 10): MAP <25 ± 5 mmHg (TBVmax 50 %) for 120 min. Resuscitation was performed using a standardized crystalloid infusion protocol. Animals were mechanically ventilated and underwent ICU-monitoring for 48 h (MH) and 48.5 h (SH). Blood samples were collected over the clinical time course, and systemic levels of serum alarmins [High-Mobility Group Protein B-1 (HMGB-1) and Heat Shock Protein 70 (HSP70)] were measured using an ELISA kit.

RESULTS

Heart rate, systemic blood pressure, lactate, and base excess were significantly altered as a function of haemorrhagic shock in both trauma groups (MH and SH). Systemic HMGB-1 levels were significantly elevated in both trauma groups when compared to the sham group. Haemorrhagic shock severity and duration were positively correlated with HMGB-1 levels and compared to baseline values, concentrations remained significantly increased in SH when compared to MH. On the other hand, we observed a significant decrease in the systemic HSP70 levels of trauma groups (MH, and SH) when compared to the sham group, which was significantly decreased compared to baseline values in SH over the entire time course.

CONCLUSION

Our data show that haemorrhagic shock duration and severity affect the systemic levels of HMGB-1 and HSP70. This early alarmins release after trauma can be used to guide the treatment strategies (e.g. surgical procedures) of polytrauma patients.

Local inflammation in fracture hematoma: results from a combined trauma model in pigs

Background. Previous studies showed significant interaction between the local and systemic inflammatory response after severe trauma in small animal models. The purpose of this study was to establish a new combined trauma model in pigs to investigate fracture-associated local inflammation and gain information about the early inflammatory stages after polytrauma. Material and Methods. Combined trauma consisted of tibial fracture, lung contusion, liver laceration, and controlled hemorrhage. Animals were mechanically ventilated and under ICU-monitoring for 48 h. Blood and fracture hematoma samples were collected during the time course of the study. Local and systemic levels of serum cytokines and diverse alarmins were measured by ELISA kit. Results. A statistical significant difference in the systemic serum values of IL-6 and HMGB1 was observed when compared to the sham. Moreover, there was a statistical significant difference in the serum values of the fracture hematoma of IL-6, IL-8, IL-10, and HMGB1 when compared to the systemic inflammatory response. However a decrease of local proinflammatory concentrations was observed while anti-inflammatory mediators increased. Conclusion. Our data showed a time-dependent activation of the local and systemic inflammatory response. Indeed it is the first study focusing on the local and systemic inflammatory response to multiple-trauma in a large animal model.

Modeling acute traumatic injury

Acute traumatic injury is a complex disease that has remained a leading cause of death, which affects all ages in our society. Direct mechanical insult to tissues may result in physiological and immunologic disturbances brought about by blood loss, coagulopathy, as well as ischemia and reperfusion insults. This inappropriate response leads to an abnormal release of endogenous mediators of inflammation that synergistically contribute to the incidence of morbidity and mortality. This aberrant activation and suppression of the immune system follows a bimodal pattern, wherein activation of the innate immune responses is followed by an anti-inflammatory response with suppression of the adaptive immunity, which can subsequently lead secondary insults and multiple organ dysfunction. Traumatic injury rodent and swine models have been used to describe many of the underlying pathologic mechanisms, which have led to an improved understanding of the morbidity and mortality associated with critically ill trauma patients. The enigmatic immunopathology of the human immunologic response after severe trauma, however, has never more been apparent and there grows a need for a clinically relevant animal model, which mimics this immune physiology to enhance the care of the most severely injured. This has necessitated preclinical studies in a more closely related model system, the nonhuman primate. In this review article, we summarize animal models of trauma that have provided insight into the clinical response and understanding of cellular mechanisms involved in the onset and progression of ischemia-reperfusion injury as well as describe future treatment options using immunomodulation-based strategies.

Resuscitation with amiodarone increases survival after hemorrhage and ventricular fibrillation in pigs

Supplemental digital content is available in the text.

BACKGROUND

The aim of this experimental study was to compare survival and hemodynamic effects of a low-dose amiodarone and vasopressin compared with vasopressin in hypovolemic cardiac arrest model in piglets.

METHODS

Eighteen anesthetized male piglets (with a weight of 25.3 [1.8] kg) were bled approximately 30% of the total blood volume via the femoral artery to a mean arterial blood pressure of 35 mm Hg in a 15-minute period. Afterward, the piglets were subjected to 4 minutes of untreated ventricular fibrillation followed by 11 minutes of open-chest cardiopulmonary resuscitation. At 5 minutes, circulatory arrest amiodarone 1 mg/kg was intravenously administered in the amiodarone group (n = 9), while the control group received the same amount of saline (n = 9). At the same time, all piglets received vasopressin 0.4 U/kg intravenously administered and hypertonic-hyperoncotic solution 3-mL/kg infusion for 20 minutes. Internal defibrillation was attempted from 7 minutes of cardiac arrest to achieve restoration of spontaneous circulation. The experiment was terminated 3 hours after resuscitation.

RESULTS

Three-hour survival was greater in the amiodarone group (p = 0.02). After the successful resuscitation, the amiodarone group piglets had significantly lower heart rate as well as greater systolic, diastolic, and mean arterial pressure. Troponin I plasma concentrations were lower and urine output was greater in the amiodarone group.

CONCLUSION

Combined resuscitation with amiodarone and vasopressin after hemorrhagic circulatory arrest resulted in greater 3-hour survival, better preserved hemodynamic parameters, and smaller myocardial injury compared with resuscitation with vasopressin only.

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.