Development of a lethal, closed-abdomen grade V hepato-portal injury model in non-coagulopathic swine

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.

Moving toward point-of-care surgery in Ukraine: testing an ultra-portable operating room in an active war zone

PURPOSE

In conflict zones, providers may have to decide between delaying time-sensitive surgeries or performing operative interventions in the field, potentially subjecting patients to significant infection risks. We conducted a single-arm crossover study to assess the feasibility of using an ultraportable operating room (U-OR) for surgical procedures on a porcine cadaver abdominal traumatic injury model in an active war zone.

METHODS

We enrolled participants from an ASSET-type course designed to train Ukrainian surgeons before deployment to active conflict zones. They performed three standardized consecutive abdominal surgical procedures (liver, kidney, and small bowel injury repair) with and without the U-OR. Primary outcomes included surgical procedure completion rate, procedure time, and airborne particle count at the start of surgery. Secondary survey-based outcomes assessed surgery task load index (SURG-TLX) and perceived operative factors.

RESULTS

Fourteen surgeons performed 76 surgical procedures (38 with the U-OR, 38 without the U-OR). The completion rate for each surgical procedure was 100% in both groups. While the procedure time for the liver injury repair did not differ significantly between the two groups, the use of the U-OR was associated with a longer time for kidney (155 vs. 56 s, p = 0.002), and small bowel (220 vs. 103 s, p = 0.004) injury repair. The average airborne particle count within the U-OR was substantially lower compared to outside the U-OR (6,753,852 vs. 232,282 n/m3, p < 0.001). There was no statistically significant difference in SURG-TLX for procedures performed with and without the U-OR.

CONCLUSION

The use of the U-OR did not affect the procedure completion rate or SURG-TLX. However, there was a marked difference in airborne particle counts between inside and outside the U-OR during surgery. These preliminary findings indicate the potential feasibility of using a U-OR to perform abdominal damage-control surgical procedures in austere settings.

Safety of the injectable expanding biopolymer foam for non-compressible truncal bleeding in swine

BACKGROUND

A novel hydrophobically modified chitosan (hm-chitosan) polymer has been previously shown to improve survival in a non-compressible intra-abdominal bleeding model in swine. We performed a 28-day survival study to evaluate the safety of the hm-chitosan polymer in swine.

METHODS

Female Yorkshire swine (40-50 kg) were used. A mild, non-compressible, closed-cavity bleeding model was created with splenic transection. The hm-chitosan polymer was applied intra-abdominally through an umbilical nozzle in the same composition and dose previously shown to improve survival. Animals were monitored intraoperatively and followed 28 days postoperatively for survival, signs of pain, and end-organ function. Gross pathological and microscopic evaluations were performed at the conclusion of the experiment.

RESULTS

A total of 10 animals were included (hm-chitosan = 8; control = 2). The 2 control animals survived through 28 days, and 7 of the 8 animals from the hm-chitosan group survived without any adverse events. One animal from the hm-chitosan group required early termination of the study for signs of pain, and superficial colonic ulcers were found on autopsy. Laboratory tests showed no signs of end-organ dysfunction after exposure to hm-chitosan after 28 days. On gross pathological examination, small (<0.5 cm) peritoneal nodules were noticed in the hm-chitosan group, which were consistent with giant-cell foreign body reaction in microscopy, presumably related to polymer remnants. Microscopically, no signs of systemic polymer embolization or thrombosis were noticed.

CONCLUSION

Prolonged intraperitoneal exposure to the hm-chitosan polymer was tolerated without any adverse event in the majority of animals. In the single animal that required early termination, the material did not appear to be associated with end-organ dysfunction in swine. Superficial colonic ulcers that would require surgical repair were identified in 1 out of 8 animals exposed to hm-chitosan.

Construction and validation of a novel and severe hepatic injury model in swine focuses on research and training. Observational study

Some hepatic wound models have been developed in pigs with the aim of reproducing liver injury; however, the wound shape, severity, and outcome differ among them. The novel injury profile employed in this study differed from that used elsewhere for standardized, repeatable, reproducible, incising-penetrating, vascular, and severe injury in swine. It is made with a cutting object that penetrates deep into the hepatic parenchyma, always affecting the two suprahepatic veins at the point where they merge into the common trunk. The primary outcome was reproducibility and replicability of the surgical method. The secondary outcome was the analysis of some variables (blood loss, survival, and flow) to validate the model. •This novel method of liver injury provides a liver injury with the following characteristics: standardized, incise-penetrated, deep, bloody, and severe.•This model can be used for research (trauma, hepato-bilio-pancreatic, pharmaceutical) and training (damage control surgery).•Method name: Incising-Penetrating, Vascular and Severe Liver Injury Model in Swine.

Comparison of a gelatin thrombin versus a modified absorbable polymer as a unique treatment for severe hepatic hemorrhage in swine

There are many surgical techniques (packing, Pringle maneuver, etc.) and hemostatic agents to manage hepatic bleeding in trauma surgery. This study compares the effectiveness of two different types of hemostatic agents, one is an active flowable hemostat and the other is a passive hemostat made of modified absorbable polymers [MAP]. Both surgical technique and hemostatic agents can be used together as a means of controlling bleeding. We have hypothesized that a single hemostatic agent might be as effective as a unique hemostatic surgical technique. Twenty swine were prospectively randomized to receive either active Flowable (Floseal) or passive MAP powder (PerClot) hemostatic agents. We used a novel severe liver injury model that caused exsanguinating hemorrhage. The main outcome measure was total blood loss volume. The total volume of blood loss, from hepatic injury to minute 120, was significantly lower in the Flowable group (407.5 cm3; IqR: 195.0-805.0 cm3) compared to MAP group (1107.5 cm3; IqR: 822.5 to 1544.5 cm3) (Hodges-Lehmann median difference: - 645.0 cm3; 95% CI: - 1144.0 to - 280.0 cm3; p = 0.0087). The rate of blood loss was significantly lower in the flowable group compared with the MAP group as measured from time of injury to minutes 3, 9, 12, and 120 (except for 6 min). The mean arterial pressure gradually recovered in the flowable group by 24 h, whereas in the MAP group, the mean arterial pressure was consistently stayed below baseline values. Kaplan-Meier survival analysis indicated similar rates of death between study groups (Logrank test p = 0.3395). Both the flowable and the MAP hemostatic agents were able to effectively control surgical bleeding in a novel severe liver injury model, however, the flowable gelatin-thrombin agent provided quicker and better bleed control.

Utility of microporous polysaccharide hemospheres in severe hepatic trauma: Experimental study of hemostatic strength and ease of use

BACKGROUND

Animal studies confirm the utility of hemostatics against standard packing following severe liver injury. We investigated the efficacy and ease of use of novel microporous polysaccharide hemosphere (MPH) compounds (Perclot®, Baxter) in the treatment of severe hepatic hemorrhage in pig.

METHODS

Pigs were randomized to one of two equal treatment groups: MPH compounds (n=12) and Standard Packing (n=12). All animals underwent standardized surgical devascularization of the suprahepatic veins (grade V) to induce severe hepatic injury. Measures relating to the hemostatic success were monitored at 12, 60, 120 minutes and 24 hours post injury.

RESULTS

Animals allocated to treatment with MPH compounds were associated with higher survival rates at 24 hours than those undergoing standard packing: 66.7% vs, 0%, respectively (p=0.001). At 120 minutes MPH compounds were also associated with reduced blood loss, median (IQR) 1.16 (0.60) vs. 10.19 (5.77) mL/Kg, respectively: p<0.001) as well as higher invasive mean arterial pressures (iMAP) median (IQR) 39.12 (11.29) vs. 25.75 (14.28) mmHg, respectively: p=0.14) and hemoglobin levels median (IQR) 5.45 (2.50) vs. 6.45 (1.73) g/dL, respectively p=0.127). Overall, the application of MPH compounds required nearly half the time of standard packing median (IQR) 32.92 (6.51) vs. 67.75 (14.66) sec, respectively: p<0.001).

CONCLUSIONS

The data suggests that the use of MPH works in a severe hemorrhage in the liver of pigs, improving many variables in comparison to standard packing, including survival, blood loss and speed of application and we conclude that this offers a potential alternative for the treatment of hepatic injury. Further work is needed to corroborate these findings.

Gastroesophageal resuscitative occlusion of the aorta prolongs survival in a lethal liver laceration model

BACKGROUND

Noncompressible torso hemorrhage management remains a challenge especially in the prehospital setting. We evaluated a device designed to occlude the aorta from the stomach (gastroesophageal resuscitative occlusion of the aorta [GROA]) for its ability to stop hemorrhage and improve survival in a swine model of lethal liver laceration and compared its performance to resuscitative endovascular balloon occlusion of the aorta (REBOA) and controls.

METHODS

Swine (n = 24) were surgically instrumented and a 30% controlled arterial hemorrhage over 20 minutes was followed by liver laceration. Animals received either GROA, REBOA, or control (no treatment) for 60 minutes. Following intervention, devices were deactivated, and animals received whole blood and crystalloid resuscitation. Animals were monitored for an additional 4 hours.

RESULTS

The liver laceration resulted in the onset of class IV shock. Mean arterial blood pressure (MAP) (standard deviation) decreased from 84.5 mm Hg (11.69 mm Hg) to 27.1 mm Hg (5.65 mm Hg) at the start of the intervention. Seven of eight control animals died from injury prior to the end of the intervention period with a median survival (interquartile) time of 10.5 minutes (12 minutes). All GROA and REBOA animals survived the duration of the intervention period (60 minutes) with median survival times of 86 minutes (232 minutes) and 79 minutes (199 minutes) after resuscitation, respectively. The GROA and REBOA animals experienced a significant improvement in survival compared with controls (p = 0.01). Resuscitative endovascular balloon occlusion of the aorta resulted in higher MAP at the end of intervention 114.6 mm Hg (22.9 mm Hg) compared with GROA 88.2 mm Hg (18.72 mm Hg) (p = 0.024), as well as increased lactate compared with GROA 13.2 meq·L-1 (1.56 meq·L-1) versus 10.5 meq·L-1 (1.89 meq·L-1) (p = 0.028). Histological examination of the gastric mucosa in surviving animals revealed mild ischemic injury from both GROA and REBOA.

CONCLUSION

The GROA and REBOA devices were both effective at temporarily stanching lethal noncompressible torso hemorrhage of the abdomen and prolonging survival.

Efficacy of past, present, and future fluid strategies in an improved large animal model of non-compressible intra-abdominal hemorrhage

BACKGROUND

Noncompressible hemorrhage is a leading cause of potentially survivable combat death, with the vast majority of such deaths occurring in the out-of-hospital environment. While large animal models of this process are important for device and therapeutic development, clinical practice has changed over time and past models must follow suit. Developed in conjunction with regulatory feedback, this study presents a modernized, out-of-hospital, noncompressible hemorrhage model, in conjunction with a randomized study of past, present, and future fluid options following a hypotensive resuscitation protocol consistent with current clinical practice.

METHODS

We performed a randomized controlled experiment comparing three fluid resuscitation options in Yorkshire swine. Baseline data from animals of same size from previous experiments were analyzed (n = 70), and mean systolic blood pressure was determined, with a permissive hypotension resuscitation target defined as a 25% decrease from normal (67 mm Hg). After animal preparation, a grade IV to V liver laceration was induced. Animals bled freely for a 10-minute "time-to-responder" period, after which resuscitation occurred with randomized fluid in boluses to the goal target: 6% hetastarch in lactated electrolyte injection (HEX), normal saline (NS), or fresh whole blood (FWB). Animals were monitored for a total simulated "delay to definitive care" period of 2 hours postinjury.

RESULTS

At the end of the 2-hour study period, 8.3% (1 of 12 swine) of the HEX group, 50% (6 of 12 swine) of the NS group, and 75% (9 of 12 swine) of the FWB had survived (p = 0.006), with Holm-Sidak pairwise comparisons showing a significant difference between HEX and FWB and (p = 0.005). Fresh whole blood had significantly higher systemic vascular resistance and hemoglobin levels compared with other groups (p = 0.003 and p = 0.001, respectively).

CONCLUSION

Survival data support the movement away from HEX toward NS and, preferably, FWB in clinical practice and translational animal modeling. The presented model allows for future research including basic science, as well as translational studies of novel diagnostics, therapeutics, and devices.

Efficacy of a Temporary Hemostatic Device in a Swine Model of Closed, Lethal Liver Injury

INTRODUCTION

Solid abdominal organ hemorrhage remains one of the leading causes of death both on the battlefield of modern warfare and in the civilian setting. A novel, temporary hemostatic device combining CELOX and direct intra-abdominal physical compression was invented to control closed SAOH during transport to a medical treatment facility.

MATERIALS AND METHODS

A swine model of closed, lethal liver injury was established to determine hemostasis. The animals were randomly divided into group A (extra-abdominal compression), group B (gauze packing), group C (intra-abdominal compression), group D (CELOX coverage), and group E (intra-abdominal compression and CELOX coverage) with six swines per group. Survival time (ST), blood loss (BL), vital signs, pathologic examination, and CT-scan were monitored to further observe the effectiveness of the device.

RESULTS

Group E had an average 30-minute extension in ST (74.3 ± 15.4 minutes versus 44.0 ± 13.8 minutes, p = 0.026) with less BL (46.0 ± 13.0 versus 70.8 ± 8.2 g/kg, p = 0.018), and maintained mean arterial pressure≥70 mmHg and cardiac output ≥ 3.5 L/minute for a longer time. No significant differences were observed in ST and BL of groups B and E, and there were no marked differences in ST and BL of groups A, C, and D. No CELOX clots were noted in the spleen, pancreas, lungs, heart, kidneys, or the adjacent large vessels in groups D and E. Compared to group A, the CT-scan showed better hepatic hemorrhage control in group E.

CONCLUSIONS

The device, which combined 20 g of CELOX particles and 20 pieces of CELOX (8 g) sponge tablets with 50-mmHg intra-abdominal compression for 10 minutes, prolonged the ST by an average of 30 minutes with less BL. It was not markedly different from the full four quadrants gauze packing of liver in hemostatic effect, with no CELOX clot formation in other organs.

Hemostatic agents for prehospital hemorrhage control: a narrative review

Hemorrhage is the leading cause of preventable death in combat trauma and the secondary cause of death in civilian trauma. A significant number of deaths due to hemorrhage occur before and in the first hour after hospital arrival. A literature search was performed through PubMed, Scopus, and Institute of Scientific Information databases for English language articles using terms relating to hemostatic agents, prehospital, battlefield or combat dressings, and prehospital hemostatic resuscitation, followed by cross-reference searching. Abstracts were screened to determine relevance and whether appropriate further review of the original articles was warranted. Based on these findings, this paper provides a review of a variety of hemostatic agents ranging from clinically approved products for human use to newly developed concepts with great potential for use in prehospital settings. These hemostatic agents can be administered either systemically or locally to stop bleeding through different mechanisms of action. Comparisons of current hemostatic products and further directions for prehospital hemorrhage control are also discussed.

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.

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.

Diffuse optical monitoring of peripheral tissues during uncontrolled internal hemorrhage in a porcine model

Reliable, continuous and noninvasive blood flow and hemoglobin monitoring in trauma patients remains a critical, but generally unachieved goal. Two optical sensing methods - diffuse correlation spectroscopy (DCS) and diffuse reflectance spectroscopy (DRS) - are used to monitor and detect internal hemorrhage. Specifically, we investigate if cutaneous perfusion measurements acquired using DCS and DRS in peripheral (thighs and ear-lobe) tissues could detect severe hemorrhagic shock in a porcine model. Four animals underwent high-grade hepato-portal injury in a closed abdomen, to induce uncontrolled hemorrhage and were subsequently allowed to bleed for 10 minutes before fluid resuscitation. DRS and DCS measurements of cutaneous blood flow were acquired using fiber optical probes placed on the thigh and earlobe of the animals and were obtained repeatedly starting from 1 to 5 minutes pre-injury, up to several minutes post shock. Clear changes were observed in measured optical spectra across all animals at both sites. DCS-derived cutaneous blood flow decreased sharply during hemorrhage, while DRS-derived vascular saturation and hemoglobin paralleled cardiac output. All derived optical parameters had the steepest changes during the rapid initial hemorrhage unambiguously. This suggests that a combined DCS and DRS based device might provide an easy-to-use, non-invasive, internal-hemorrhage detection system that can be used across a wide array of clinical settings.

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.

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.

Percutaneous damage control with self-expanding foam: pre-hospital rescue from abdominal exsanguination

Non-compressible intra-abdominal hemorrhage results in significant morbidity and mortality in contemporary trauma medicine. Regrettably, many deaths from non-compressible hemorrhage are attributable to potentially survivable injuries. A self-expanding polyurethane foam has been developed for rapid, percutaneous damage control of exsanguinating abdominal hemorrhage, for patients not expected to survive to definitive surgical care. Foam intervention creates a temporary, commensal, hemostatic environment within the abdominal cavity. This tropism away from exsanguination physiology creates a hemostatic bridge such that the patient may reach definitive surgical intervention. This review article summarizes the existing literature characterizing the safety and efficacy of this intervention, along with a study in recently deceased patients that enables dose translation from animal models to human beings.

Chronic safety assessment of hemostatic self-expanding foam: 90-day survival study and intramuscular biocompatibility

BACKGROUND

Noncompressible hemorrhage is a significant cause of preventable death in trauma, with no effective presurgical treatments. We previously described the efficacy and 28-day safety of a self-expanding hemostatic foam in swine models. We hypothesized that the 28-day results would be confirmed at a second site and that results would be consistent over 90 days. Finally, we hypothesized that the foam material would be biocompatible following intramuscular implantation.

METHODS

Foam treatment was administered in swine following a closed-cavity splenic injury. The material was explanted after 3 hours, and the animals were monitored to 28 days (n = 6) or 90 days (n = 4). Results were compared with a control group with injury alone (n = 6 at 28 days, n = 3 at 90 days). In a separate study, foam samples were implanted in rabbit paravertebral muscle and assessed at 28 days and 90 days relative to a Food and Drug Administration-approved polyurethane mesh (n = 3 per group).

RESULTS

All animals survived the acute phase of the study, and the foam animals required enterorrhaphy. One animal developed postoperative ileus and was euthanized; all other animals survived to the 28-day or 90-day end point without clinically significant complications. Histologic evaluation demonstrated that remnant particles were associated with a fibrotic capsule and mild inflammation. The foam was considered biocompatible in 28-day and 90-day intramuscular implant studies.

CONCLUSION

Foam treatment was not associated with significant evidence of end-organ dysfunction or toxicity at 28 days or 90 days. Remnant foam particles were well tolerated. These results support the long-term safety of this intervention for severely bleeding patients.

Diagnosis and deployment of a self-expanding foam for abdominal exsanguination: Translational questions for human use

BACKGROUND

We have previously described the hemostatic efficacy of a self-expanding polyurethane foam in lethal venous and arterial hemorrhage models. A number of critical translational questions remain, including prehospital diagnosis of hemorrhage, use with diaphragmatic injury, effects on spontaneous respiration, the role of omentum, and presence of a laparotomy on foam properties.

METHODS

In Experiment 1, diagnostic blood aspiration was attempted through a Veress needle before foam deployment during exsanguination (n = 53). In Experiment 2: a lethal hepatoportal injury/diaphragmatic laceration was created followed by foam (n = 6) or resuscitation (n = 10). In Experiment 3, the foam was deployed in naïve, spontaneously breathing animals (n = 7), and respiration was monitored. In Experiments 4 and 5, the foam was deployed above (n = 6) and below the omentum (n = 6) and in naïve animals (n = 6). Intra-abdominal pressure and organ contact were assessed.

RESULTS

In Experiment 1, blood was successfully aspirated from a Veress needle in 70% of lethal iliac artery injuries and 100% of lethal hepatoportal injuries. In Experiment 2, in the presence of a diaphragm injury, between 0 cc and 110 cc of foam was found within the pleural space. Foam treatment resulted in a survival benefit relative to the control group at 1 hour (p = 0.03). In Experiment 3, hypercarbia was observed: mean (SD) Pco2 was 48 (9.4) mm Hg at baseline and 65 (14) mm Hg at 60 minutes. In Experiment 4, abdominal omentum seemed to influence organ contact and transport in two foam deployments. In Experiment 5, there was no difference in intra-abdominal pressure following foam deployment in the absence of a midline laparotomy.

CONCLUSION

In a series of large animal studies, we addressed key translational issues surrounding safe use of foam treatment. These additional data, from diagnosis to deployment, will guide human experiences with foam treatment for massive abdominal exsanguination where no other treatments are available.

Self-expanding foam for prehospital treatment of intra-abdominal hemorrhage: 28-day survival and safety

BACKGROUND

Intracavitary noncompressible hemorrhage remains a significant cause of preventable death on the battlefield and in the homeland. We previously demonstrated the hemostatic efficacy of an in situ self-expanding poly(urea)urethane foam in a severe, closed-cavity, hepatoportal exsanguination model in swine. We hypothesized that treatment with, and subsequent explantation of, foam would not adversely impact 28-day survival in swine.

METHODS

Following a closed-cavity splenic transection, animals received either fluid resuscitation alone (control group, n = 6) or resuscitation plus foam treatment at doses of 100 mL (n = 6), 120 mL (n = 6), and 150 mL (n = 2). Foam was allowed to polymerize in situ and was explanted after 3 hours. The animals were recovered and monitored for 28 days.

RESULTS

All 18 animals in the 100-mL, 120-mL, and control groups survived to the 28-day endpoint without complications. The 150-mL group was terminated after the acute phase (n = 2). En bloc explantation of the foam took less than 2 minutes and was associated with millimeter-sized remnant particles. All foam animals required some level of enteric repair (imbrication or resection). Excluding the aborted 150-mL group, all animals survived, with no differences in renal or hepatic function, serum chemistries, or semiquantitative abdominal adhesion scores. Histologic analysis demonstrated that remnant particles were associated with a fibrotic capsule and mild inflammation, similar to that of standard suture reaction. In addition, safety testing (including genotoxicity, pyrogenicity, and cytotoxicity) was performed consistent with the ISO-10993 standard, and the materials passed all tests.

CONCLUSION

For a distinct dose range, 28-day recovery after foam treatment and explantation for noncompressible, intra-abdominal hemorrhage is not associated with significant physiologic or biochemical evidence of end-organ dysfunction. A foam volume exceeding the maximum tolerable dose was identified. Bowel repair is required to ensure survival.

A laparoscopic swine model of noncompressible torso hemorrhage

BACKGROUND

Hemorrhage persists as the leading cause of potentially preventable civilian and military death. Noncompressible torso hemorrhage (NCTH) is a particularly lethal injury complex, with few contemporary prehospital interventions available. Various porcine models of hemorrhage have been developed for civilian and military trauma research. However, the predominant contemporary models lack key physiologic characteristics including the natural tamponade provided by an intact abdominal wall.To improve physiologic and clinical relevance, we developed a laparoscopic model of NCTH. This approach maintains both the integrity of the peritoneum and the natural tamponade effect of an intact abdominal wall while preserving the intrinsic physiologic responses to hemorrhage. Furthermore, we present data quantifying the contribution of the swine contractile spleen in the context of uncontrolled hemorrhage.

METHODS

Anesthetized adult male Yorkshire swine underwent a laparoscopic Grade V liver injury, with or without open preinjury splenectomy. Animals were observed without intervention for a total of 120 minutes after injury to simulate point of injury, transport time, and arrival at hospital.

RESULTS

Shed blood-to-body weight ratio did not differ among groups; however, mortality was higher in splenectomized animals (67% vs. 33%). Cox regression modeling demonstrated a critical time point of 45 minutes and blood pressure as significant predictors of mortality.

CONCLUSION

This study describes a model of NCTH that reflects clinically relevant physiology in trauma and uncontrolled hemorrhage. In addition, it quantitatively assesses the role of the swine contractile spleen in the described 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.

Development of a fatal noncompressible truncal hemorrhage model with combined hepatic and portal venous injury in normothermic normovolemic swine

Noncompressible truncal hemorrhage and brain injury currently account for most early mortality of warfighters on the battlefield. There is no effective treatment for noncompressible truncal hemorrhage, other than rapid evacuation to a surgical facility. The availability of an effective field treatment for noncompressible truncal hemorrhage could increase the number of warfighters salvaged from this frequently-lethal scenario. Our intent was to develop a porcine model of noncompressible truncal hemorrhage with a ∼50% one-hour mortality so that we could develop new treatments for this difficult problem. Normovolemic normothermic domestic swine (barrows, 3 months old, 34–36 kg) underwent one of three injury types through a midline incision: 1) central stellate injury (N = 6); 2) excision of a portal vein branch distal to the main PV trunk (N = 6); or 3) hemi-transection of the left lateral lobe of the liver at its base (N = 10). The one-hour mortality of these injuries was 0, 82, and 40%, respectively; the final mean arterial pressure was 65, 24, and 30 mm Hg, respectively; and the final hemoglobin was 8.3, 2.3, and 3.6 g/dL, respectively. Hemi-transection of the left lateral lobe of the liver appeared to target our desired mortality rate better than the other injury mechanisms.

Self-expanding foam improves survival following a lethal, exsanguinating iliac artery injury

BACKGROUND

Noncompressible abdominal bleeding is a significant cause of preventable death on the battlefield and in the civilian setting, with no effective therapies available at point of injury. We previously reported that a self-expanding polyurethane foam significantly improved survival in a lethal hepatoportal injury model of massive venous hemorrhage. In this study, we hypothesized that foam treatment could improve survival in a lethal iliac artery injury model in noncoagulopathic swine.

METHODS

In swine with a closed abdomen, an iliac artery transection was created, resulting in massive noncompressible exsanguination. After injury, animals were treated with damage-control fluid resuscitation alone (n = 14) or foam treatment in addition to fluids. Two doses of foam treatment were studied: 100 mL (n = 12) and 120 mL (n = 13); all animals were monitored for 3 hours or until death.

RESULTS

Foam treatment at both doses resulted in a significant survival benefit and reduction in hemorrhage rate relative to the control group. Median survival time was 135 minutes and 175 minutes for the 120-mL and 100-mL doses, compared with 32 minutes in the control group (p < 0.001 for both groups). Foam resulted in an immediate, persistent improvement in mean arterial pressure and a transient increase in intra-abdominal pressure. The median hemorrhage rate was 0.27 g/kg per minute in the 120-mL group and 0.23 g/kg per minute in the 100-mL group, compared with 1.4 g/kg per minute in the control group (p = 0.003 and 0.006, respectively, as compared with the control).

CONCLUSION

Self-expanding foam treatment significantly improves survival in an otherwise lethal, noncompressible, massive, arterial injury. This treatment may provide a prehospital intervention for control of noncompressible abdominal hemorrhage.

Hydrophobically-modified chitosan foam: description and hemostatic efficacy

BACKGROUND

Trauma represents a significant public health burden, and hemorrhage alone is responsible for 40% of deaths within the first 24 h after injury. Noncompressible hemorrhage accounts for the majority of hemorrhage-related deaths. Thus, materials which can arrest bleeding rapidly are necessary for improved clinical outcomes. This preliminary study evaluated several self-expanding hydrophobically modified chitosan (HM-CS) foams to determine their efficacy on a noncompressible severe liver injury under resuscitation.

METHODS

Six HM-CS foam formulations (HM-CS1, HM-CS2, HM-CS3, HM-CS4, HM-CS5, and HM-CS6) of different graft types and densities were synthesized, characterized, and packaged into spray canisters using dimethyl ether as the propellant. Expansion profiles of the foams were evaluated in bench testing. Foams were then evaluated in vitro, interaction with blood cells was determined via microscopy, and cytotoxicity was assessed via live-dead cell assay on MCF7 breast cancer cells. For in vivo evaluation, rats underwent a 14 ± 3% hepatectomy. The animals were treated with either: (1) an HM-CS foam formulation, (2) CS foam, and (3) no treatment (NT). All animals were resuscitated with lactated Ringer solution. Survival, total blood loss, mean arterial pressures (MAP), and resuscitation volume were recorded for 60 min.

RESULTS

Microscopy showed blood cells immobilizing into colonies within tight groups of adjacent foam bubbles. HM-CS foam did not display any toxic effects in vitro on MCF7 cells over a 72 h period studied. Application of HM-CS foam after hepatectomy decreased total blood loss (29.3 ± 7.8 mL/kg in HM-CS5 group versus 90.9 ± 20.3 mL/kg in the control group; P <0.001) and improved survival from 0% in controls to 100% in the HM-CS5 group (P <0.001).

CONCLUSIONS

In this model of severe liver injury, spraying HM-CS foams directly on the injured liver surface decreased blood loss and increased survival. HM-CS formulations with the highest levels of hydrophobic modification (HM-CS4 and HM-CS5) resulted in the lowest total blood loss and highest survival rates. This pilot study suggests HM-CS foam may be useful as a hemostatic adjunct or solitary hemostatic intervention.

Self-expanding foam for prehospital treatment of severe intra-abdominal hemorrhage: dose finding study

BACKGROUND

Noncompressible abdominal bleeding is a significant cause of preventable death on the battlefield and in the civilian trauma environment, with no effective therapies available at point of injury. We previously described the development of a percutaneously administered, self-expanding, poly(urea)urethane foam that improved survival in a lethal Grade V hepatic and portal vein injury model in swine. In this study, we hypothesized that survival with foam treatment is dose dependent.

METHODS

A high-grade hepatoportal injury was created in a closed abdominal cavity, resulting in massive noncompressible hemorrhage. After injury, the animals were divided into five groups. The control group (n = 12) was treated only with fluid resuscitation, and four polymer groups received different dose volumes (Group 1, n = 6, 64 mL; Group 2, n = 6, 85 mL; Group 3, n = 18, 100 mL; and Group 4, n = 10, 120 mL) in addition to fluids. Ten minutes after injury, the foam was percutaneously administered, and animals were monitored for 3 hours.

RESULTS

Survival with hepatoportal injury was highest in Group 4 (90%) and decreased in a dose-dependent fashion (Group 3, 72%; Group 2, 33%; Group 1, 17%). All polymer groups survived significantly longer than the controls (8.3%). Hemorrhage rate was reduced in all groups but lowest in Group 4 versus the control group (0.34 [0.052] vs. 3.0 [1.3] mL/kg/min, p < 0.001). Increasing foam dose volume was associated with increased peak intra-abdominal pressure (88.2 [38.9] in Group 4 vs. 9.5 [3.2] in the controls, p < 0.0001) and increased incidence of focal bowel injuries.

CONCLUSION

The self-expanding foam significantly improves survival in a dose-dependent fashion in an otherwise lethal injury. Higher doses are associated with better survival but resulted in the need for bowel resection.

Development of a lethal, closed-abdomen, arterial hemorrhage model in noncoagulopathic swine

BACKGROUND

Prehospital treatment for noncompressible abdominal bleeding, particularly due to large vascular injury, represents a significant unmet medical need on the battlefield and in civilian trauma. To date, few large animal models are available to assess new therapeutic interventions and hemostatic agents for prehospital hemorrhage control.

METHODS

We developed a novel, lethal, closed-abdomen injury model in noncoagulopathic swine by strategic placement of a cutting wire around the external iliac artery. The wire was externalized, such that percutaneous distraction would result in vessel transection leading to severe uncontrolled abdominal hemorrhage. Resuscitation boluses were administered at 5 and 12 min.

RESULTS

We demonstrated 86% mortality (12/14 animals) at 60 min, with a median survival time of 32 min. The injury resulted in rapid and massive hypotension and exsanguinating blood loss. The noncoagulopathic animal model incorporated clinically significant resuscitation and ventilation protocols based on best evidenced-based prehospital practices.

CONCLUSION

A new injury model is presented that enables screening of prehospital interventions designed to control noncompressible arterial hemorrhage.