A laparoscopic swine model of noncompressible torso hemorrhage

Development of a two-hit lethal liver injury model in swine

PURPOSE

Noncompressible truncal hemorrhage remains a leading cause of preventable death in the prehospital setting. Standardized and reproducible large animal models are essential to test new therapeutic strategies. However, existing injury models vary significantly in consistency and clinical accuracy. This study aims to develop a lethal porcine model to test hemostatic agents targeting noncompressible abdominal hemorrhages.

METHODS

We developed a two-hit injury model in Yorkshire swine, consisting of a grade IV liver injury combined with hemodilution. The hemodilution was induced by controlled exsanguination of 30% of the total blood volume and a 3:1 resuscitation with crystalloids. Subsequently, a grade IV liver injury was performed by sharp transection of both median lobes of the liver, resulting in major bleeding and severe hypotension. The abdominal incision was closed within 60 s from the injury. The endpoints included mortality, survival time, serum lab values, and blood loss within the abdomen.

RESULTS

This model was lethal in all animals (5/5), with a mean survival time of 24.4 ± 3.8 min. The standardized liver resection was uniform at 14.4 ± 2.1% of the total liver weight. Following the injury, the MAP dropped by 27 ± 8mmHg within the first 10 min. The use of a mixed injury model (i.e., open injury, closed hemorrhage) was instrumental in creating a standardized injury while allowing for a clinically significant hemorrhage.

CONCLUSION

This novel highly lethal, consistent, and clinically relevant translational model can be used to test and develop life-saving interventions for massive noncompressible abdominal hemorrhage.

Transition of Resuscitative Endovascular Balloon Occlusion of the Aorta from Zone 3 to Zone 1 to Treat Hemodynamic Collapse during Continued Hemorrhage

INTRODUCTION

Noncompressible torso hemorrhage (NCTH) accounts for most potentially survivable deaths on the battlefield. Treatment of NCTH is challenging, especially in far-forward environments with limited capabilities. Resuscitative endovascular balloon occlusion of the aorta (REBOA) has shown promise in the care of patients with NCTH. REBOA involves introducing a balloon catheter into the descending aorta in a specific occlusion region (zones 1, 2, or 3) and acts as a hemorrhage control adjunct with resuscitative support. The balloon is placed in zone 3 in the infrarenal aorta for high junctional or pelvic injuries and in zone 1 proximal to the diaphragm for torso hemorrhage. Zone 1 REBOA provides more resuscitative support than zone 3; however, the potential for ischemia and reperfusion injuries is greater with zone 1 than with zone 3 REBOA placement. This study aims to determine the possible benefit of transitioning the REBOA balloon from zone 3 to zone 1 to rescue a patient with ongoing venous bleeding and impending cardiovascular collapse.

MATERIALS AND METHODS

Yorkshire male swine (70-90 kg, n = 6 per group) underwent injury to the femoral artery, which was allowed to bleed freely for 60 s, along with a simultaneous controlled venous hemorrhage. After 60 s, the arterial bleed was controlled with hemostatic gauze and zone 3 REBOA was inflated. Five hundred milliliters of Hextend was used for initial fluid resuscitation. The controlled venous bleed continued until a mean arterial pressure (MAP) of 30 mmHg was reached to create an impending cardiovascular collapse. The animals were then randomized into either continued zone 3 REBOA or transition from zone 3 to zone 1 REBOA. Following 30 min, a "hospital phase" was initiated, consisting of cessation of the venous hemorrhage, deflation of the REBOA balloon, and transfusion of one unit of whole blood administered along with saline and norepinephrine to maintain a MAP of 60 mmHg or higher. The animals then underwent a 2-h observation period. Survival, hemodynamics, and blood chemistries were compared between groups.

RESULTS

No significant differences between groups were observed in hemodynamic or laboratory values at baseline, postinitial injury, or when MAP reached 30 mmHg. Survival was significantly longer in animals that transitioned into zone 1 REBOA (log-rank analysis, P = .012). The average time of survival was 14 ± 10 min for zone 3 animals vs. 65 ± 59 min for zone 1 animals (P = .064). No animals in the zone 3 group survived to the hospital phase. Zone 1-treated animals showed immediate hemodynamic improvement after transition, with maximum blood pressure reaching near baseline values compared to those in the zone 3 group.

CONCLUSIONS

In this swine model of NCTH, hemodynamics and survival were improved when the REBOA balloon was transitioned from zone 3 to zone 1 during an impending cardiovascular collapse. Furthermore, these improved outcome data support the pursuit of additional research into mitigating ischemia-reperfusion insult to the abdominal viscera while still providing excellent resuscitative support, such as intermittent or partial REBOA.

Thermoreversible Reverse-Phase-Shift Foam for Treatment of Noncompressible Torso Hemorrhage, a Safety Trial in a Porcine Model

INTRODUCTION

Noncompressible torso hemorrhage is the leading cause of exsanguination on the battlefield. A self-expanding, intraperitoneal deployed, thermoreversible foam has been developed that can be easily administered by a medic in austere settings to temporarily tamponade noncompressible torso hemorrhage. The purpose of this study was to assess the long-term safety and physical characteristics of using Fast Onset Abdominal Management (FOAM; Critical Innovations LLC) in swine.

MATERIALS AND METHODS

Yorkshire swine (40-60 kg) were sedated, intubated, and placed on ventilatory support. An external jugular catheter was placed for sampling of blood. Continuous heart rate, temperature, saturation of peripheral oxygen, end-tidal carbon dioxide, and peak airway pressures were monitored for a 4-hour period after intervention (i.e., FOAM agent injection or a sham introducer without agent delivery). The FOAM agent was injected to obtain an intra-abdominal pressure of 60 mmHg for at least 10 minutes. After 4 hours, the animals were removed from ventilatory support and returned to their housing for a period of 7-14 days. Group size analysis was not performed, as this was a descriptive safety study. Blood samples were obtained at baseline and at 1-hour post-intervention and then on days 1, 3, 7, and 14. Euthanasia, necropsy, and harvesting of samples for histologic analysis (from kidneys, terminal ilium, liver, pancreas, stomach, spleen, and lungs) were performed upon expiration. Histologic scoring for evidence of ischemia, necrosis, and abdominal compartment sequela was blinded and reported by semi-quantitative scale (range 0-4; 0 = no change, 1 = minimal, 2 = mild, 3 = moderate, and 4 = marked). Oregon Health & Science University's Institutional Animal Care and Use Committee, as well as the U.S. Army Animal Care and Use Review Office, approved this protocol before the initiation of experiments (respectively, protocol numbers IP00003591 and MT180006.e002).

RESULTS

Five animals met a priori inclusion criteria, and all of these survived to their scheduled endpoints. Two animals received sham injections of the FOAM agent (one euthanized on day 7 and one on day 14), and three animals received FOAM agent injections (one euthanized on day 7 and two on day 14). A transitory increase in creatinine and lactate was detected during the first day in the FOAM injected swine but resolved by day 3. No FOAM agent was observed in the peritoneal cavity upon necropsy at day 7 or 14. Histologic data revealed no clinically relevant differences in any organ system between intervention and control animals upon sacrifice at day 7 or 14.

CONCLUSIONS

This study describes the characteristics, survival, and histological analysis of using FOAM in a porcine model. In our study, FOAM reached the desired intra-abdominal pressure endpoint while not significantly altering basic hematologic parameters, except for transient elevations of creatinine and lactate on day 1. Furthermore, there was no clinical or histological relevant evidence of ischemia, necrosis, or intra-abdominal compartment syndrome. These results provide strong support for the safety of the FOAM device and will support the design of further regulatory studies in swine and humans.

Thermoreversible Reverse-Phase-Shift Foam for Treatment of Noncompressible Torso Hemorrhage

BACKGROUND

Noncompressible torso hemorrhage (NCTH) is a leading cause of traumatic exsanguination, requiring emergent damage control surgery performed by a highly trained surgeon in a sterile operating environment. A self-expanding, intraabdominally deployed, thermoreversible foam is one proposed method to potentially task shift temporizing hemostasis to earlier providers and additional settings. The purpose of this study was to assess the feasibility of using Fast Onset Abdominal Management (FOAM) in a lethal swine model of NCTH.

METHODS

This was a proof-of-concept study comparing FOAM intervention in large Yorkshire swine to historical control animals in the established Ross-Burns model of NCTH. After animal preparation, a Grade IV liver laceration was surgically induced, followed by a free bleed period of 10 min. FOAM was then deployed to a goal intraabdominal pressure of 60 mm Hg for 5 min, followed by a total 60-min observation period following injury.

RESULTS

At the end of the experiment, the FOAM agent was found to be distributed throughout the peritoneal cavity in all animals, without signs of iatrogenic injury. The FOAM group demonstrated a significantly higher mean arterial pressure compared with historical controls and a trend toward improved survival: 82% (9/11) compared with 50% for controls (7/14; P = 0.082).

CONCLUSIONS

This is the first study to describe the use of a thermoresponsive foam to manage NCTH and successfully demonstrated proof-of-concept feasibility of FOAM deployment. These results provide strong support for future, higher-powered studies to confirm improved survival with this novel intervention.

Does the pediatric hemodynamic cliff exist in response to hemorrhagic shock?

BACKGROUND

The paradigm that children maintain normal blood pressure during hemorrhagic shock until 30%-45% hemorrhage is widely accepted. There are minimal data supporting when decompensation occurs and how a child's vasculature compensates up to that point. We aimed to observe the arterial response to hemorrhage and when mean arterial pressure (MAP) decreased from baseline in pediatric swine.

METHODS

Piglets were hemorrhaged in 20% increments of their total blood volume to 60%. MAP and angiograms of the thoracic aorta (TA) and abdominal arteries were obtained. Percent change in area of the vessels from baseline was calculated.

RESULTS

Piglets (n = 8) had a differential vasoconstriction starting at 20% hemorrhage (celiac artery 36.3% [31.4-44.6] vs TA 16.7% [10.7-19.1] p = 0.0012). At 40% hemorrhage, the differential vasoconstriction favored shunting blood away from the abdominal visceral branches to the TA (celiac artery 54.7% [36.9-60.6] vs TA 29.5% [23.9-36.2] p = 0.0056 superior mesenteric artery 46.7% [43.9-68.6] vs TA 29.5% [23.9-36.2] p = 0.0100). This was exacerbated at 60% hemorrhage. MAP decreased from baseline at 20% hemorrhage (66.4 ± 6.0 mmHg vs 41.4 ± 10.4 mmHg, p < 0.0001), and worsened at 40% and 60% hemorrhage.

CONCLUSION

In piglets, a differential vasocontriction shunting blood proximally occurred in response to hemorrhage. This did not maintain normal MAP at 20%, 40% or 60% hemorrhage.

LEVEL OF EVIDENCE

Level II.

Novel use of XSTAT 30 for mitigation of lethal non-compressible torso hemorrhage in swine

Background

Management of Non-Compressible Torso Hemorrhage (NCTH) consists primarily of aortic occlusion which has significant adverse outcomes, including ischemia-reperfusion injury, in prolonged field care paradigms. One promising avenue for treatment is through use of RevMedx XSTAT 30™ (an FDA approved sponge-based dressing utilized for extremity wounds). We hypothesized that XSTAT 30™ would effectively mitigate NCTH during a prolonged pre-hospital period with correctable metabolic and physiologic derangements.

Methods and findings

Twenty-four male swine (53±2kg) were anesthetized, underwent line placement, and splenectomy. Animals then underwent laparoscopic transection of 70% of the left lobe of the liver with hemorrhage for a period of 10min. They were randomized into three groups: No intevention (CON), XSTAT 30™-Free Pellets (FP), and XSTAT 30™-Bagged Pellets (BP). Animals were observed for a pre-hospital period of 180min. At 180min, animals underwent damage control surgery (DCS), balanced blood product resuscitation and removal of pellets followed by an ICU period of 5 hours. Postoperative fluoroscopy was performed to identify remaining pellets or bags. Baseline physiologic and injury characteristics were similar. Survival rates were significantly higher in FP and BP (p<0.01) vs CON. DCS was significantly longer in FP in comparison to BP (p = 0.001). Two animals in the FP group had pellets discovered on fluoroscopy following DCS. There was no significant difference in blood product or pressor requirements between groups. End-ICU lactates trended to baseline in both FP and BP groups.

Conclusions

While these results are promising, further study will be required to better understand the role for XSTAT in the management of NCTH.

Resuscitative endovascular balloon occlusion of the aorta (REBOA) in a pediatric swine liver injury model: A pilot study

BACKGROUND

Resuscitative endovascular balloon occlusion of the aorta (REBOA) has not been studied in children. We hypothesized that REBOA was feasible and would improve hemorrhage control and survival time, compared to no aortic occlusion, in a pediatric swine liver injury model.

METHODS

Pediatric swine were randomized to Zone 1 REBOA or no intervention (control). Piglets underwent a partial liver amputation and free hemorrhage followed by either REBOA or no intervention for 30 min, then a damage control laparotomy and critical care for 4 h.

RESULTS

Compared to control piglets (n = 5), REBOA piglets (n = 6) had less blood loss (34.0 ± 1.6 vs 61.3 ± 2.5 mL/kg, p < 0.01), higher end hematocrit (28.1 ± 2.1 vs 17.1 ± 4.1%, p = 0.03), higher end creatinine (1.4 ± 0.1 vs 1.2 ± 0.1 mg/dL, p = 0.05), higher end ALT and AST (56 ± 4 vs 32 ± 6 U/L, p = 0.01 and 155 ± 26 vs 69 ± 25 U/L, p = 0.05) and required more norepinephrine during critical care (1.4 ± 0.3 vs 0.3 ± 0.3 mg/kg, p = 0.04). All REBOA piglets survived, whereas 2 control piglets died, p = 0.10.

CONCLUSION

In pediatric swine, 30 min of REBOA is feasible, decreases blood loss after liver injury and may improve survival.

LEVEL OF EVIDENCE

Level 1.

Selective aortic arch perfusion with fresh whole blood or HBOC-201 reverses hemorrhage-induced traumatic cardiac arrest in a lethal model of noncompressible torso hemorrhage

BACKGROUND

Hemorrhage-induced traumatic cardiac arrest (HiTCA) has a dismal survival rate. Previous studies demonstrated selective aortic arch perfusion (SAAP) with fresh whole blood (FWB) improved the rate of return of spontaneous circulation (ROSC) after HiTCA, compared with resuscitative endovascular balloon occlusion of the aorta and cardiopulmonary resuscitation (CPR). Hemoglobin-based oxygen carriers, such as hemoglobin-based oxygen carrier (HBOC)-201, may alleviate the logistical constraints of using FWB in a prehospital setting. It is unknown whether SAAP with HBOC-201 is equivalent in efficacy to FWB, whether conversion from SAAP to extracorporeal life support (ECLS) is feasible, and whether physiologic derangement post-SAAP therapy is reversible.

METHODS

Twenty-six swine (79 ± 4 kg) were anesthetized and underwent HiTCA which was induced via liver injury and controlled hemorrhage. Following arrest, swine were randomly allocated to resuscitation using SAAP with FWB (n = 12) or HBOC-201 (n = 14). After SAAP was initiated, animals were monitored for a 20-minute prehospital period prior to a 40-minute damage control surgery and resuscitation phase, followed by 260 minutes of critical care. Primary outcomes included rate of ROSC, survival, conversion to ECLS, and correction of physiology.

RESULTS

Baseline physiologic measurements were similar between groups. ROSC was achieved in 100% of the FWB animals and 86% of the HBOC-201 animals (p = 0.483). Survival (t = 320 minutes) was 92% (11/12) in the FWB group and 67% (8/12) in the HBOC-201 group (p = 0.120). Conversion to ECLS was successful in 100% of both groups. Lactate peaked at 80 minutes in both groups, and significantly improved by the end of the experiment in the HBOC-201 group (p = 0.001) but not in the FWB group (p = 0.104). There was no significant difference in peak or end lactate between groups.

CONCLUSION

Selective aortic arch perfusion is effective in eliciting ROSC after HiTCA in a swine model, using either FWB or HBOC-201. Transition from SAAP to ECLS after definitive hemorrhage control is feasible, resulting in high overall survival and improvement in lactic acidosis over the study period.

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.

Lower extremity cooling reduces ischemia-reperfusion injury following Zone 3 REBOA in a porcine hemorrhage model

BACKGROUND

New strategies to mitigate ischemia during REBOA and to prolong its maximal duration are needed. We hypothesized that simple external cooling of the hind limbs would decrease ischemia-reperfusion injury following prolonged Zone 3 REBOA.

METHODS

Twelve swine were anesthetized, instrumented, splenectomized, and then underwent 15% total blood volume hemorrhage. Animals were randomized to hypothermia or control followed by 4 hours of Zone 3 REBOA, resuscitation with shed blood, and 3 hours of critical care. Physiologic parameters were continuously recorded, and laboratory specimens were obtained at regular intervals. Baseline and end-of-study muscle biopsies were obtained for histologic analysis.

RESULTS

There were no significant differences between groups at baseline or after hemorrhage. Maximum creatine kinase was significantly lower in the hypothermia group compared with the normothermia group (median [interquartile range] = 3,445 U/mL [3,380-4,402 U/mL] vs. 22,544 U/mL [17,030-24,981 U/mL]; p < 0.01). Maximum serum myoglobin was also significantly lower in the hypothermia group (1,792 ng/mL [1,250-3,668 ng/mL] vs. 21,186 ng/mL [14,181-24,779 ng/mL]; p < 0.01). Fascial compartment pressures were significantly lower during critical care in the hypothermia group (p = 0.03). No histologic differences were observed in hind limb skeletal muscle.

CONCLUSIONS

External cooling during prolonged Zone 3 REBOA decreased ischemic muscle injury and resulted in lower compartment pressures following reperfusion. Hypothermia may be a viable option to extend the tolerable duration of Zone 3 occlusion, beyond what is currently achievable. Future survival studies are required to assess functional outcomes.

Hemorrhage Treatment Adjuncts in a Helicopter Emergency Medical Service

Hemorrhaging is the leading cause of preventable death after trauma. In our helicopter emergency medical service (HEMS), we introduced a bundle of 3 hemostatic adjuncts: 1) tourniquet, 2) hemostatic chitosan-based wound packings, and 3) tranexamic acid (TXA). The real-life frequency of applying these adjuncts in HEMS remains unclear. Therefore, we analyzed our electronic HEMS database regarding the use of these hemostatic adjuncts. We analyzed all subsequent dispatches of our HEMS "Lifeliner 1" within a searchable digital database (01.02.2013-22.05.2018). This HEMS operates 24/7, servicing ∼4.5 million inhabitants of the Netherlands. During the 75-month study period, we registered 15,759 dispatches, of which 8,658 were canceled, and 7,101 included on-site patient care, including 4,928 (69.4%) trauma cases. In total, we recorded 78 tourniquet applications (1.1% of patients), 104 hemostatic wound packings (1.5% of patients), and 1,379 cases with prehospital TXA administration (19.4% of patients). This difference in the use of hemostatics has several contributors, including a possible lack of awareness for tourniquets and procoagulant wound packing, a high proportion of blunt trauma with internal bleeding not accessible to tourniquet or wound packing, and a liberal use of TXA (eg, in patients with unproven hemorrhage). Besides creating awareness for those hemostatic adjuncts, the practical implications of our findings need further evaluation in future studies.

Fabrication of injectable and superelastic nanofiber rectangle matrices ("peanuts") and their potential applications in hemostasis

Uncontrolled hemorrhage, which typically involves the torso and/or limb junctional zones, remains a great challenge in the prehospital setting. Here, we for the first time report an injectable and superelastic nanofiber rectangle matrix ("peanut") fabricated by a combination of electrospinning, gas foaming, hydrogel coating and crosslinking techniques. The compressed nanofiber peanut is capable of re-expanding to its original shape in atmosphere, water and blood within 10 s. Such nanofiber peanuts exhibit greater capacity of water/blood absorption compared to current commercial products and high efficacy in whole blood clotting assay, in particular for thrombin-immobilized samples. These nanofiber peanuts are capable of being packed into a syringe for injection. Further in vivo tests indicated the effectiveness of nanofiber peanuts for hemostasis in a porcine liver injury model. This new class of nanofiber-based materials may hold great promise for hemostatic applications.

Experimental Study of Thoracoabdominal Injuries Suffered from Caudocephalad Impacts Using Pigs

To know the caudocephalad impact- (CCI-) induced injuries more clearly, 21 adult minipigs, randomly divided into three groups: control group (n = 3), group I (n = 9), and group II (n = 9), were used to perform the CCI experiments on a modified deceleration sled. Configured impact velocity was 0 m/s in the control group, 8 m/s in group I, and 11 m/s in group II. The kinematics and mechanical responses of the subjects were recorded and investigated. The functional change examination and the autopsies were carried out, with which the injuries were evaluated from the Abbreviated Injury Scale (AIS) and the Injury Severity Score (ISS). The subjects in group I and group II experienced the caudocephalad loading at the peak pelvic accelerations of 108.92 ± 58.87 g and 139.13 g ± 78.54 g, with the peak abdomen pressures, 41.24 ± 16.89 kPa and 63.61 ± 65.83 kPa, respectively. The injuries of the spleen, lung, heart, and spine were detected frequently among the tested subjects. The maximal AIS (MAIS) of chest injuries was 4 in group I and 5 in group II, while both the MAIS of abdomen injuries in group I and group II were 5. The ISS in group II was 52.71 ± 6.13, significantly higher than in group I, 26.67 ± 5.02 (p < 0.05). The thoracoabdomen CCI injuries and the mechanical response addressed presently may be useful to conduct both the prevention studies against military or civilian injuries.

The coherence of macrocirculation, microcirculation, and tissue metabolic response during nontraumatic hemorrhagic shock in swine

Hemorrhagic shock is clinically observed as changes in macrocirculatory indices, while its main pathological constituent is cellular asphyxia due to microcirculatory alterations. The coherence between macro‐ and microcirculatory changes in different shock states has been questioned. This also applies to the hemorrhagic shock. Most studies, as well as clinical situations, of hemorrhagic shock include a “second hit” by tissue trauma. It is therefore unclear to what extent the hemorrhage itself contributes to this lack of circulatory coherence. Nine pigs in general anesthesia were exposed to a controlled withdrawal of 50% of their blood volume over 30 min, and then retransfusion over 20 min after 70 min of hypovolemia. We collected macrocirculatory variables, microcirculatory blood flow measurement by the fluorescent microspheres technique, as well as global microcirculatory patency by calculation of Pv‐aCO₂, and tissue metabolism measurement by the use of microdialysis. The hemorrhage led to anticipated changes in macrocirculatory variables with a coherent change in microcirculatory and metabolic variables. In the late hemorrhagic phase, the animals' variables generally improved, probably through recruitment of venous blood reservoirs. After retransfusion, all variables were normalized and remained same throughout the study period. We find in our nontraumatic model consistent coherence between changes in macrocirculatory indices, microcirculatory blood flow, and tissue metabolic response during hemorrhagic shock and retransfusion. This indicates that severe, but brief, hemorrhage with minimal tissue injury is in itself not sufficient to cause lack of coherence between macro‐ and microcirculation.

Host responses to concurrent combined injuries in non-human primates

Background

Multi-organ failure (MOF) following trauma remains a significant cause of morbidity and mortality related to a poorly understood abnormal inflammatory response. We characterized the inflammatory response in a non-human primate soft tissue injury and closed abdomen hemorrhage and sepsis model developed to assess realistic injury patterns and induce MOF.

Methods

Adult male Mauritan Cynomolgus Macaques underwent laparoscopy to create a cecal perforation and non-anatomic liver resection along with a full-thickness flank soft tissue injury. Treatment consisted of a pre-hospital phase followed by a hospital phase after 120 minutes. Blood counts, chemistries, and cytokines/chemokines were measured throughout the study. Lung tissue inflammation/apoptosis was confirmed by mRNA quantitative real-time PCR (qPCR), H&E, myeloperoxidase (MPO) and TUNEL staining was performed comparing age-matched uninjured controls to experimental animals.

Results

Twenty-one animals underwent the protocol. Mean percent hepatectomy was 64.4 ± 5.6; percent blood loss was 69.0 ± 12.1. Clinical evidence of end-organ damage was reflected by a significant elevation in creatinine (1.1 ± 0.03 vs. 1.9 ± 0.4, p=0.026). Significant increases in systemic levels of IL-10, IL-1ra, IL-6, G-CSF, and MCP-1 occurred (11-2986-fold) by 240 minutes. Excessive pulmonary inflammation was evidenced by alveolar edema, congestion, and wall thickening (H&E staining). Concordantly, amplified accumulation of MPO leukocytes and significant pulmonary inflammation and pneumocyte apoptosis (TUNEL) was confirmed using qRT-PCR.

Conclusion

We created a clinically relevant large animal multi-trauma model using laparoscopy that resulted in a significant systemic inflammatory response and MOF. With this model, we anticipate studying systemic inflammation and testing innovative therapeutic options.

Incremental balloon deflation following complete resuscitative endovascular balloon occlusion of the aorta results in steep inflection of flow and rapid reperfusion in a large animal model of hemorrhagic shock

INTRODUCTION

To avoid potential cardiovascular collapse after resuscitative endovascular balloon occlusion of the aorta (REBOA), current guidelines recommend methodically deflating the balloon for 5 minutes to gradually reperfuse distal tissue beds. However, anecdotal evidence suggests that this approach may still result in unpredictable aortic flow rates and hemodynamic instability. We sought to characterize aortic flow dynamics following REBOA as the balloon is deflated in accordance with current practice guidelines.

METHODS

Eight Yorkshire-cross swine were splenectomized, instrumented, and subjected to rapid 25% total blood volume hemorrhage. After 30 minutes of shock, animals received 60 minutes of Zone 1 REBOA with a low-profile REBOA catheter. During subsequent resuscitation with shed blood, the aortic occlusion balloon was gradually deflated in stepwise fashion at the rate of 0.5 mL every 30 seconds until completely deflated. Aortic flow rate and proximal mean arterial pressure (MAP) were measured continuously over the period of balloon deflation.

RESULTS

Graded balloon deflation resulted in variable initial return of aortic flow (median, 78 seconds; interquartile range [IQR], 68-105 seconds). A rapid increase in aortic flow during a single-balloon deflation step was observed in all animals (median, 819 mL/min; IQR, 664-1241 mL/min) and corresponded with an immediate decrease in proximal MAP (median, 30 mm Hg; IQR, 14.5-37 mm Hg). Total balloon volume and time to return of flow demonstrated no correlation (r = 0.016).

CONCLUSION

This study is the first to characterize aortic flow during balloon deflation following REBOA. A steep inflection point occurs during balloon deflation that results in an abrupt increase in aortic flow and a concomitant decrease in MAP. Furthermore, the onset of distal aortic flow was inconsistent across study animals and did not correlate with initial balloon volume or relative deflation volume. Future studies to define the factors that affect aortic flow during balloon deflation are needed to facilitate controlled reperfusion following REBOA.

Small changes, big effects: The hemodynamics of partial and complete aortic occlusion to inform next generation resuscitation techniques and technologies

BACKGROUND

The transition from complete aortic occlusion during resuscitative endovascular balloon occlusion of the aorta can be associated with hemodynamic instability. Technique refinements and new technologies have been proposed to minimize this effect. In order to inform new techniques and technology, we examined the relationship between blood pressure and aortic flow during the restoration of systemic circulation following aortic occlusion at progressive levels of hemorrhage.

METHODS

An automated supraceliac aortic clamp, capable of continuously variable degrees of occlusion, was applied in seven swine. The swine underwent stepwise removal of 40% of their total blood volume in four equal aliquots. After each aliquot, progressive luminal narrowing to the point of complete aortic occlusion was achieved over 5 minutes, sustained for 5 minutes, and then released over 5 minutes. Proximal and distal blood pressure and distal aortic flow were continuously recorded throughout the study.

RESULTS

Upon release of the clamp, hyperemic aortic flow was observed following 10% and 20% hemorrhage (1,599 ± 785 mL/min, p < 0.01; and 1,070 ± 396 mL/min, p < 0.01, respectively). Proximal blood pressure exhibited a nonlinear relationship to aortic flow during clamp removal; however, distal blood pressure increased linearly with distal flow upon clamp opening across all hemorrhage volumes.

CONCLUSIONS

Hyperemic blood flow following return of circulation may contribute to cardiovascular collapse. Reintroduction of systemic blood flow after aortic occlusion should be guided by distal blood pressure rather than proximal pressure. Awareness of hemodynamic physiology during aortic occlusion is of paramount importance to the clinical implementation of next-generation resuscitative endovascular balloon occlusion of the aorta techniques and technologies.

A novel model of highly lethal uncontrolled torso hemorrhage in swine

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

LEVEL OF EVIDENCE

Level I.

A comparison of Selective Aortic Arch Perfusion and Resuscitative Endovascular Balloon Occlusion of the Aorta for the management of hemorrhage-induced traumatic cardiac arrest: A translational model in large swine

BACKGROUND

Survival rates remain low after hemorrhage-induced traumatic cardiac arrest (TCA). Noncompressible torso hemorrhage (NCTH) is a major cause of potentially survivable trauma death. Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) at the thoracic aorta (Zone 1) can limit subdiaphragmatic blood loss and allow for IV fluid resuscitation when intrinsic cardiac activity is still present. Selective Aortic Arch Perfusion (SAAP) combines thoracic aortic balloon hemorrhage control with intra-aortic oxygenated perfusion to achieve return of spontaneous circulation (ROSC) when cardiac arrest has occurred.

METHODS AND FINDINGS

Male Yorkshire Landrace cross swine (80.0 ± 6.0 kg) underwent anesthesia, instrumentation for monitoring, and splenectomy. TCA was induced by laparoscopic liver lobe resection combined with arterial catheter blood withdrawal to achieve a sustained systolic blood pressure <10 mmHg, cardiac arrest. After 3 min of arrest, swine were allocated to one of three interventions: (1) REBOA plus 4 units of IV fresh whole blood (FWB), (2) SAAP with oxygenated lactated Ringer's (LR), 1,600 mL/2 min, or (3) SAAP with oxygenated FWB 1,600 mL/2 min. Primary endpoint was survival to the end of 60 min of resuscitation, a simulated prehospital phase. Thirty animals were allocated to 3 groups (10 per group)-5 protocol exclusions resulted in a total of 35 animals being used. Baseline measurements and time to cardiac arrest were not different amongst groups. ROSC was achieved in 0/10 (0%, 95% CI 0.00-30.9) REBOA, 6/10 (60%, 95% CI 26.2-87.8) SAAP-LR and 10/10 (100%, 95% CI 69.2-100.0) SAAP-FWB animals, p < 0.001. Survival to end of simulated 60-minute prehospital resuscitation was 0/10 (0%, 95% CI 0.00-30.9) for REBOA, 1/10 (10%, 95% CI 0.25-44.5) for SAAP-LR and 9/10 (90%, 95% CI 55.5-99.7) for SAAP-FWB, p < 0.001. Total FWB infusion volume was similar for REBOA (2,452 ± 0 mL) and SAAP-FWB (2,250 ± 594 mL). This study was undertaken in laboratory conditions, and as such may have practical limitations when applied clinically. Cardiac arrest in this study was defined by intra-aortic pressure monitoring that is not feasible in clinical practice, and as such limits the generalizability of findings. Clinical trials are needed to determine if the beneficial effects of SAAP-FWB observed in this laboratory study will translate into improved survival in clinical practice.

CONCLUSIONS

SAAP conferred a superior short-term survival over REBOA in this large animal model of hemorrhage-induced traumatic cardiac arrest with NCTH. SAAP using an oxygen-carrying perfusate was more effective in this study than non-oxygen carrying solutions in TCA. SAAP can effect ROSC from hemorrhage-induced electrocardiographic asystole in large swine.