Dry fibrin sealant dressings reduce blood loss, resuscitation volume, and improve survival in hypothermic coagulopathic swine with grade V liver injuries

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.

Hemostatic strategies for uncontrolled bleeding: A comprehensive update

Uncontrolled bleeding remains the leading cause of morbidity and mortality across the entire macrocosm. It refers to excessive loss of blood that occurs inside of body, due to unsuccessful platelet plug formation at the injury site. It is not only limited to the battlefield, but remains the second leading cause of death amongst the civilians, as a result of traumatic injury. Startlingly, there are no effective treatments currently available, to cater the issue of internal bleeding, even though early intervention is of utmost significance in minimizing the mortality rates associated with it. The fatal issue of uncontrolled bleeding is ineffectively being dealt with the use of pressure dressings, tourniquet, and surgical procedures. This is not a practical approach in combat arenas or in emergency situations, where the traumatic injury inflicted is deep inside the body, and cannot be addressed externally, by the application of topical dressings. This review focuses on the traditional hemostatic agents that are used to augment the process of hemostasis, such as mineral zeolites, chitosan based products, biologically active agents, anti-fibrinolytics, absorbable agents, and albumin and glutaraldehyde, as well as the micro- and nano-based hemostatic agents such as synthocytes, thromboerythrocytes, thrombosomes, and the synthetic platelets.

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

BACKGROUND

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

RESULTS

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

CONCLUSIONS

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

COMPARATIVE ANALYSIS OF SURGICAL HEMOSTATIC SPONGES IN LIVER INJURY: STUDY IN RATS

BACKGROUND

Obtaining effective hemostasis either in the traumatic or surgical lesions of parenchymal viscera, especially the liver, has always been a challenge.

AIM

Comparative study between the use of different hemostatic sponges in hepatic wound and their capacity of integration to cells in a short period.

METHODS

Fifteen Wistar rats were divided into three groups. Through laparotomy a standardized wound in hepatic right lobe was made. The animals were treated with three sponges, being gelatin in group I, equine collagen in group II, and oxidized cellulose in group III. The hemostatic capacity was analysed. On the 7º day after surgery samples for histology analysis (H&E and picrosirius) were collected for inflammatory evaluation and collagen quantification (types I and III) with polarized microscopy.

RESULTS

All materials used had similar haemostatic effects, with no significant difference in hemostasis time. In the assessment of tissue repair and adhesions provoked, as well as analysis of the inflammatory process, the gelatin sponge presented greater inflammation and adhesions to the contiguous structures to the procedure in relation to the other groups.

CONCLUSION

Animals which had their wounds treated with collagen and regenerated cellulose sponges presented better results in relationship to the ones treated with gelatin sponge.

Recent advances in topical agents for prehospital haemostasis

The prehospital treatment of severe extremity bleeding has remained unchanged for years and relies on compression with absorbent gauze dressings. Advances in haemostasis technology have identified several new methods of improving bleeding control. These are examined with a view to possible inclusion in a new prehospital dressing aimed at reducing the degree of exsanguination and associated mortality and morbidity from a major extremity injury.

Metabolomic analysis of survival in carbohydrate pre-fed pigs subjected to shock and polytrauma

Hemorrhagic shock, a result of extensive blood loss, is a dominant factor in battlefield morbidity and mortality. Early rodent studies in hemorrhagic shock reported carbohydrate feeding prior to the induction of hemorrhagic shock decreased mortality. When repeated in our laboratory with a porcine model, carbohydrate pre-feed resulted in a 60% increase in death rate following hemorrhagic shock with trauma when compared to fasted animals (15/32 or 47% vs. 9/32 or 28%). In an attempt to explain the unexpected death rate for pre-fed animals, we further investigated the metabolic profiles of pre-fed non-survivors (n = 15) across 4 compartments (liver, muscle, serum, and urine) at specific time intervals (pre-shock, shock, and resuscitation) and compared them to pre-fed survivors (n = 17). As hypothesized, pre-fed pigs that died as a result of hemorrhage and trauma showed differences in their metabolic and physiologic profiles at all time intervals and in all compartments when compared to pre-fed survivors. Our data suggest that, although all animals were subjected to the same shock and trauma protocol, non-survivors exhibited altered carbohydrate processing as early as the pre-shock sampling point. This was evident in (for example) the higher levels of ATP and markers of greater anabolic activity in the muscle at the pre-shock time point. Based on the metabolic findings, we propose two mechanisms that connect pre-fed status to a higher death rate: (1) animals that die are more susceptible to opening of the mitochondrial permeability transition pore, a major factor in ischemia/reperfusion injury; and (2) loss of fasting-associated survival mechanisms in pre-fed animals.

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.

Massive transfusion policies at trauma centers participating in the American College of Surgeons Trauma Quality Improvement Program

BACKGROUND

Massive transfusion protocols (MTPs) have been developed to implement damage control resuscitation (DCR) principles. A survey of MTP policies from American College of Surgeons Trauma Quality Improvement Program (ACS-TQIP) participants was performed to establish which MTP activation, hemostatic resuscitation, and monitoring aspects of DCR are included in the MTP guidelines.

METHODS

On October 10, 2013, ACS-TQIP administration administered a cross-sectional electronic survey to 187 ACS-TQIP participants.

RESULTS

Seventy-one percent (132 of 187) of responses were analyzed, with 62% designated as Level I and 38% designated as Level II ACS-TQIP trauma centers. Sixty-nine percent of sites indicated that they have plasma immediately available for MTP activation. By policy, in the first group of blood products administered, 88% of sites target high (≥1:2) plasma-to-red blood cell (RBC) ratios and 10% target low ratios. Likewise, 79% of sites target high platelet-to-RBC ratios and 16% target low ratios. Eighteen percent of sites reported incorporating point-of-care thromboelastogram into MTP policies. The most common intravenous hemostatic adjunct incorporated into MTPs was tranexamic acid (49%). Thirty-four percent of sites reported that some or all of their emergency medical service agencies have the ability to administer blood products or hemostatic agents during prehospital transport. There were minimal differences in MTP policies or capabilities between Level I and II sites.

CONCLUSION

The majority of ACS-TQIP participants reported having MTPs that support the use of DCR principles including high plasma-to-RBC and platelet-to-RBC ratios. Immediate availability of plasma and product use by emergency medical services are becoming increasingly common, whereas the incorporation of point-of-care thromboelastogram into MTP policies remains low.

A four-compartment metabolomics analysis of the liver, muscle, serum, and urine response to polytrauma with hemorrhagic shock following carbohydrate prefeed

Objective

Hemorrhagic shock accompanied by injury represents a major physiologic stress. Fasted animals are often used to study hemorrhagic shock (with injury). A fasted state is not guaranteed in the general human population. The objective of this study was to determine if fed animals would exhibit a different metabolic profile in response to hemorrhagic shock with trauma when compared to fasted animals.

Methods

Proton (1H) NMR spectroscopy was used to determine concentrations of metabolites from four different compartments (liver, muscle, serum, urine) taken at defined time points throughout shock/injury and resuscitation. PLS-DA was performed and VIP lists established for baseline, shock and resuscitation (10 metabolites for each compartment at each time interval) on metabolomics data from surviving animals.

Results

Fed status prior to the occurrence of hemorrhagic shock with injury alters the metabolic course of this trauma and potentially affects mortality. The death rate for CPF animals is higher than FS animals (47 vs 28%). The majority of deaths occur post-resuscitation suggesting reperfusion injury. The metabolomics response to shock reflects priorities evident at baseline. FS animals raise the baseline degree of proteolysis to provide additional amino acids for energy production while CPF animals rely on both glucose and, to a lesser extent, amino acids. During early resuscitation levels of metabolites associated with energy production drop, suggesting diminished demand.

Conclusions

Feeding status prior to the occurrence of hemorrhagic shock with injury alters the metabolic course of this trauma and potentially affects mortality. The response to shock reflects metabolic priorities at baseline.

In vivo study of novelly formulated porcine-derived fibrinogen as an efficient sealant

Fibrinogen has been used as surgical sealant in the clinical setting for decades. The application of human plasma-derived fibrinogen is limited due to high cost and the risk of prion and virus infection. We developed a novel arginine-formulated fibrinogen from cryoprecipitates of porcine plasma. This porcine-derived fibrinogen exhibited excellent stability during sterilization and better hemostatic efficacy than a leading commercial hemostatic product in a nonlethal hemorrhage model. Therefore, it has the potential to be more economical and readily available while having a decreased risk of human blood-borne pathogen transmission.

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.

Fibrin patch in a pig model with blunt liver injury under severe hypothermia

BACKGROUND

Rapid control of hemorrhage is one of the key aspects in trauma handling. To cope with bleeding, local hemostatic approaches are useful, along with surgical and systemic homostatic therapy. In this experimental study, we investigated the efficacy of a fibrinogen/thrombin containing collagen patch (TachoSil) in a coagulopathic pig model with blunt liver trauma under severe hypothermia.

METHODS

Eighteen anesthetized pigs underwent hemodilution by exchanging 70% of the blood volume with Ringer Lactate solution and hydroxyethyl starch 130/0.4 (1:1). Ten minutes after induction of a grade III blunt liver trauma, the animals randomly received treatment with TachoSil (FT-patch, n = 9) or a collagen patch (Tachotop, control group, n = 9). Blood loss, hemodynamics, and coagulation parameters were observed for 2 h. To confirm the consistency of liver trauma, pathologic examination of the liver tissue was performed.

RESULTS

Hypothermia (33.5°C ± 0.5°C) and hemodilution led to severe coagulopathy as measured by thromboelastometry and coagulation parameters. After trauma and patch application, thromboelastometry and coagulation parameters in the control group showed further deterioration compared with the stable parameters in the FT-patch group. The total blood loss was significantly reduced in the FT-patch group (FT-patch: 1195 mL; control group: 2495 mL; P < 0.001). Concordantly, the control animals were hemodynamically jeopardized to a higher degree. Microscopy confirmed a similar degree of liver injury.

CONCLUSIONS

Despite severe hypothermia and coagulopathy, TachoSil provided effective hemorrhage control in pigs with blunt liver injury. Therefore, TachoSil demonstrated usefulness as an additional early therapy in cases of uncontrolled bleeding following severe trauma.

A totally recombinant human fibrin sealant

BACKGROUND

Applications of plasma-derived human fibrin sealants (pdhFS) have been limited because of cost, limited supply of pathogen-screened plasma, the need for bioengineering improvements, and regulatory issues associated with federal approval. We describe a totally recombinant human fibrin sealant (rhFS), which may engender an abundant, safe, and cost-effective supply of efficacious fibrin sealant.

MATERIALS AND METHODS

A first-generation rhFS made from recombinant human fibrinogen (rhFI; produced in the milk of transgenic cows), activated recombinant human factor XIII (rhFXIIIa; produced in yeast), and recombinant human thrombin (rhFIIa; purchased, made in animal cell culture) was formulated using thromboelastography (TEG). The hemostatic efficacy of rhFS versus commercial pdhFS was compared in a nonlethal porcine hepatic wedge excision model.

RESULTS

The maximal clot strength of rhFS measured in vitro by TEG was not statistically different than that of pdhFS. TEG analysis also showed that the rhFS gained strength more quickly as reflected by a steeper α angle; however, the rhFS achieved this clot strength with a 5-fold lower factor I content than the pdhFS. When these fibrin sealants were studied in a porcine hepatic wedge excision model, the hemostatic scores of the rhFS were equivalent or better than that of the pdhFS.

CONCLUSIONS

The bioengineered rhFS had equivalent or better hemostatic efficacy than the pdhFS in a nonlethal hemorrhage model, despite the factor I concentration in the rhFS being about one-fifth that in the pdhFS. Because the rhFS is amenable to large-scale production, the rhFS has the potential to be more economical and abundant than the pdhFS, while having a decreased risk of blood-borne pathogen transmission.

Novel keratin (KeraStat™) and polyurethane (Nanosan®-Sorb) biomaterials are hemostatic in a porcine lethal extremity hemorrhage model

Traumatic injury is the leading cause of death in people aged 44 or less in the US. It is also estimated that 82% of deaths from battlefield hemorrhage may be survivable with better treatment options. In this study, two biomaterial hemostats having disparate mechanisms were evaluated in a large animal lethal hemorrhage model and compared to a commercial product and standard cotton gauze. We hypothesized that the biomaterial with a biologically active mechanism, as opposed to a mechanical mechanism, would be the most effective in this model. Using a published study protocol, the femoral artery in swine was punctured and treated. KeraStat™ (KeraNetics) and Nanosan®-Sorb (SNS Nano) hemostats were compared to a commercial chitosan dressing (second generation Hemcon®) and cotton gauze. Both KeraStat and Nanosan increased survival, significantly increased mean arterial pressure (MAP), and significantly decreased shock index compared to both controls. The Hemcon dressing was no different than gauze. Platelet adhesion assays suggested that the KeraStat mechanism of action involves β1 integrin mediated platelet adhesion while Nanosan-Sorb operates similar to one reported mechanism for Hemcon, absorbing fluid and concentrating clotting components. The Nanosan also swelled considerably and created pressure within the wound site even after direct pressure was removed.

Local and Systemic Hemostatics as an Adjunct to Control Bleeding in Trauma

Although surgical and angiointervention techniques remain the cornerstone for the management of severe bleeding after trauma, adjunct therapeutic strategies such as local or systemic hemostatic agents can play an important role. This article reviews the role and efficacy of the available hemostatic agents.

Internal vacuum-assisted closure device in the swine model of severe liver injury

OBJECTIVES

The authors present a novel approach to nonresectional therapy in major hepatic trauma utilizing intraabdominal perihepatic vacuum assisted closure (VAC) therapy in the porcine model of Grade V liver injury.

METHODS

A Grade V injury was created in the right lobe of the liver in a healthy pig. A Pringle maneuver was applied (4.5 minutes total clamp time) and a vacuum assisted closure device was placed over the injured lobe and connected to suction. The device consisted of a perforated plastic bag placed over the liver, followed by a 15 cm by 15cm VAC sponge covered with a nonperforated plastic bag. The abdomen was closed temporarily. Blood loss, cardiopulmonary parameters and bladder pressures were measured over a one-hour period. The device was then removed and the animal was euthanized.

RESULTS

Feasibility of device placement was demonstrated by maintenance of adequate vacuum suction pressures and seal. VAC placement presented no major technical challenges. Successful control of ongoing liver hemorrhage was achieved with the VAC. Total blood loss was 625 ml (20ml/kg). This corresponds to class II hemorrhagic shock in humans and compares favorably to previously reported estimated blood losses with similar grade liver injuries in the swine model. No post-injury cardiopulmonary compromise or elevated abdominal compartment pressures were encountered, while hepatic parenchymal perfusion was maintained.

CONCLUSION

These data demonstrate the feasibility and utility of a perihepatic negative pressure device for the treatment of hemorrhage from severe liver injury in the porcine model.

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

BACKGROUND

Hemorrhage within an intact abdominal cavity remains a leading cause of preventable death on the battlefield. Despite this need, there is no existing closed-cavity animal model to assess new hemostatic agents for the preoperative control of intra-abdominal hemorrhage.

METHODS

We developed a novel, lethal liver injury model in non-coagulopathic swine by strategic placement of two wire loops in the medial liver lobes including the hepatic and portal veins. Distraction resulted in grade V liver laceration with hepato-portal injury, massive bleeding, and severe hypotension. Crystalloid resuscitation was started once mean arterial pressure (MAP) fell below 65 mm Hg. Monitoring continued for up to 180 min.

RESULTS

We demonstrated 90% lethality (9/10) in swine receiving injury and fluid resuscitation, with a mean survival time of 43 min. Previous efforts in our laboratory to develop a consistently lethal swine model of abdominal solid organs, including preemptive anticoagulation, a two-hit injury with controlled hemorrhage prior to liver trauma, and the injury described above without resuscitation, consistently failed to result in lethal injury.

CONCLUSION

This model can be used to screen other interventions for pre hospital control of noncompressible.

QuikClot masquerading as Glaser shot: a new forensic pathology artifact?

Although in the forensic sphere, Glaser ammunition or handgun shot cartridges represent one of the most significant advances in firearms ballistics in the past 100 years, the mineral-based zeolite hemostatic agent QuikClot represents a no less significant development in the surgical and clinical context of the trauma-induced management of battlefield wounding and hemorrhage. Because of the essential structural configuration of both Glaser ammunition and QuikClot, consisting as they do of metallic beads on the one hand and mineral-based spherules on the other, the possibility exists that a medicolegal autopsy on a victim of gunshot wounding and on whom surgery has been performed with introduction of QuikClot in an effort to stem bleeding, the spherules of QuikClot might be misinterpreted as the pellets of handgun shot cartridges.We present a case of fatal wounding by a 9-mm handgun in which the discovery of QuikClot in the peritoneal cavity at autopsy initially raised the possibility of wounding by Glaser ammunition.

New hemostatic dressing (FAST Dressing) reduces blood loss and improves survival in a grade V liver injury model in noncoagulopathic swine

BACKGROUND

We performed this study to evaluate the hemostatic efficacy of the FAST Dressing in treating a grade V liver injury in noncoagulopathic swine.

METHODS

Sixteen female splenectomized, noncoagulopathic swine underwent reproducible grade V liver injuries. The animals were blindly randomized to two treatment groups: (1) FAST Dressing (n = 8) or (2) IgG placebo dressing (n = 8). After 30 seconds of uncontrolled hemorrhage, dressings and manual compression were applied at 4-minute intervals. The number of dressings used, time to hemostasis, total blood loss, mean arterial pressure, blood chemistry, and total resuscitation fluid volume were monitored for 2 hours after injury.

RESULTS

The mean total blood loss was 412.5 mL (SD 201.3) for the FAST Dressing group compared with 2296.6 mL (SD 1076.0) in the placebo group (p < 0.001). All animals in the FAST Dressing group achieved hemostasis and survived for the duration of the experiment (2 hours) after injury, whereas none of the animals in the placebo group attained hemostasis or survived to 2 hours after injury (p < 0.001). The mean time to hemostasis was 6.6 minutes (SD 2.5). A median of five dressings (mean absolute deviation 1.0, p = 0.007) was sufficient to control hemorrhage in the FAST Dressing group.

CONCLUSION

The FAST Dressing reduced blood loss and improved survival compared with placebo in a noncoagulopathic, grade V liver injury swine model.

Pre-hospital haemostatic dressings: a systematic review

BACKGROUND

Uncontrolled haemorrhage is a leading cause of prehospital death after military and civilian trauma. Exsanguination from extremity wounds causes over half of preven military combat deaths and wounds to the anatomical junctional zones provide a particular challenge for first responders. Commercial products have been developed, which claim to outperform standard gauze bandages in establishing and maintaining non-surgical haemostasis. Since 2004, two advanced haemostatic dressing products, HemCon and QuikClot have been widely deployed in military operations. Newer products have since become available which aim to provide more efficient haemostasis than and thus supersede HemCon and QuikClot.

AIM

To conduct a systematic review of clinical and preclinical evidence to compare the relative efficacy and safety of available haemostatic products, which are of relevance to pre-hospital military and civilian emergency medical providers.

METHOD

An English language literature search was performed, using PubMed and Web of Knowledge Databases, with cross-referencing, focussed product searches and communication with product manufacturers. For studies employing animal models, the injury model was required to produce fatal haemorrhage. Products were categorised by primary mode of action as either factor concentrators,mucoadhesive agents or procoagulant supplementors.

RESULTS

From 60 articles collated, 6 clinical papers and 37 preclinical animal trials were eligible for inclusion in this review. Products have been tested in three different types of haemorrhage model: low pressure, high volume venous bleeding, high pressure arterial bleeding and mixed arterial-venous bleeding. The efficacy of products varies with the model adopted. Criteria for the 'ideal battle field haemostatic dressing' have previously been defined by Pusateri, but no product has yet attained suchstatus. Since 2004, HemCon (a mucoadhesive agent) and QuikClot (a factor concentrator) have been widely deployed by United States and United Kingdom Armed Forces; retrospective clinical data supports their efficacy. However, in some recent animal models of lethal haemorrhage, WoundStat(mucoadhesive), Celox (mucoadhesive) and CombatGauze (procoagulant supplementor) have all outperformed both HemCon and QuikClot products.

CONCLUSION

HemCon and QuikClot have augmented the haemostatic capabilities of the military first aid responder, but newer products demonstrate potential to be more effective and should be considered as replacements for current in service systems. These products could have utility for civilian pre-hospital care.

Effect of TachoSil in a coagulopathic pig model with blunt liver injuries

OBJECTIVE

In this study, we investigated the efficacy of a fibrinogen/thrombin-coated collagen patch (TachoSil) to terminate severe bleeding in a coagulopathic pig model with blunt liver injury.

METHODS

Following surgical preparation, which included splenectomy and cystotomy, coagulopathy was induced by exchanging 80% of the animal's blood volume with hydroxyethylstarch 130/0.4 and lactated Ringer's solution. Subsequently, a grade III liver injury was induced by a force of 238 ± 19 Newton and free bleeding was allowed for 30 s. Animals were randomly assigned to receive either a placebo patch (cotton patch) (control group, n = 7) or a fibrinogen/thrombin patch (FT patch group, n = 7), which was positioned 30 s after injury on the inflicted area. Coagulation parameters, hemodynamic variables, as well as treatment were monitored for 2 h post-injury and patch placement. Histology was obtained to evaluate the equality of liver injury and to show the morphology of the FT patch.

RESULTS

Hemostasis after hemodilution was severely impaired. Blood loss after trauma was significantly diminished in the FT patch group (419 mL ± 90 mL) compared with the control group (1775 mL ± 358 mL) (P < 0.001). All animals treated with the FT patch survived, whereas 100% of the control group died before reaching the end of the observation period (P < 0.001). Gross sectioning and histology showed an equal degree of injury with a tight adherence of the FT patch.

CONCLUSION

TachoSil under severe coagulopathy effectively controlled bleeding and successfully prevented hemorrhagic death.

Evaluation of a New Hemostatic Agent in a Porcine Grade V Liver Injury Model

Our objective was to evaluate the hemostatic efficacy of a newly modified chitosan in a porcine grade V liver injury model. Fifteen Yorkshire pigs underwent standardized grade V liver injuries with a specially designed liver clamp and were randomized to either modified chitosan (MC) patch treatment or standard gauze packing. Free bleeding was allowed for 30 seconds. Fluid resuscitation was infused as necessary to reestablish a mean arterial pressure (MAP) within at least 80 per cent of the preinjury MAP. Animals were observed for 90 minutes or until death. Endpoints were survival, total blood loss, time to hemostasis, and resuscitation MAP, and resuscitation volume. Total mean blood loss was less in the MC patch group (464 ± 267 mL vs 1234 ± 78 mL, P < 0.001). Time to hemostasis was significantly less (4.8 ± 2.5 minutes in the MC patch group vs 9.6 ± 2.5 minutes, P < 0.01). Fluid resuscitation was less (1098 ± 459 mL in the MC patch group vs 1770 ± 172 mL, P < 0.01). Survival was 100 per cent in the MC patch group and 80 per cent in the gauze packing group. MC patches demonstrate the continued hemostatic agent evolution for improved control of lethal solid organ bleeding.

Use of a modified chitosan dressing in a hypothermic coagulopathic grade V liver injury model

BACKGROUND

Exsanguination from hepatic trauma is exacerbated by the lethal triad of acidosis, coagulopathy, and hypothermia. We evaluated the application of a modified chitosan dressing in a hypothermic coagulopathic model of grade V liver injury.

METHODS

Subject swine underwent induced hypothermic coagulopathy followed by standardized grade V liver injuries. A modified chitosan dressing was applied and compared with standard packing.

RESULTS

Pretreatment temperature, activated clotting time, and blood loss were similar between groups. Post treatment blood loss was significantly less and resuscitation mean arterial pressure were significantly greater in the modified chitosan group (P < .0001 and P < .018, respectively). Mean fluid resuscitative volume was significantly less in the modified chitosan group (P < .0056). Hemostasis was achieved on average 5.2 minutes following modified chitosan and never achieved with standard packing. At 1 hour post injury, all treatment animals survived compared with half of controls.

CONCLUSIONS

Modified chitosan dressings provide simple rapid treatment of life-threatening liver injuries.

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

BACKGROUND

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

Comparisons of three surgical procedures on intestine ischemia reperfusion injury in a superior mesenteric artery injury model

BACKGROUND

Temporary ligation, primary anastomosis, and temporary shunt have been reported to deal with superior mesenteric artery (SMA) injuries. We aimed to investigate which brought minimal ischemia reperfusion injury in a hypothermic traumatic shock swine model.

METHODS

SMA was completely clamped while pigs were hemorrhaged to a mean arterial pressure (MAP) of 40 mm Hg. Animals were then randomized into temporary ligation (A, n=8), primary anastomosis (B, n=8), temporary shunt (C, n=8), and control groups (n=4). Animals in group A remained SMA interrupted for additional 1h while the other groups underwent the corresponding procedures immediately. Intestine injury was assessed by histologic examination and measurement of lipid peroxidations at the end of ischemia and experiment.

RESULTS

Overall mortality rate was 50%, 25%, and 0% in groups A, B, and C, respectively (P<0.05). The total intestine ischemia time was predominantly shorter in group C in the other groups. Remarkable elevations of malonaldehyde (MDA) in small intestine were noted after reperfusion in group A. Animals in other groups, however, did not exacerbate during the 6-h reperfusion (resuscitation period). Group C showed the lowest MDA level at the end of experiment. Myeloperoxidase (MPO) levels showed no significant elevations during the ischemia or early reperfusion period; nevertheless, it reached approximately 3- to 6-fold in groups A and B (compared with baseline, P<0.01), and remained unchanged in group C at the end of experiment.

CONCLUSION

Our study suggests that temporary shunt insertion might be preferred as it shortens ischemia time, alleviates intestinal ischemia/reperfusion injury, and thus decreases early mortality in this animal model.

Assessment of the Thrombogenic Effect of Fibrin Sealant Dressing in a Vascular Surgery Model in Rabbits

This study's objective was to investigate the potential thrombogenic effects of thrombin-containing fibrin sealant dressings (FSD) in a vascular repair model. Oval-shaped pieces of the rabbit abdominal aorta and vena cava were excised, the injuries were repaired with FSD, and animals were allowed to recover. Thrombus formation was examined by (1) an infusion of indium-labeled platelets into the rabbits following FSD application and estimation of total number of platelets attached to the wounds at 2, 4, and 6 h later (short-term effect, n = 12); and by (2) morphological and histological examinations of the vessels and dressings on days 1, 3, and 7 after repair operation in another group of rabbits (long-term effect, n = 12). Application of FSD sealed the vascular injures and produced immediate hemostasis that was stable up to 1 week. The highest numbers of platelets (both native and labeled) adhered to the arterial and venous repair sites were 6.5 x 106 and 4.4 x 107, respectively, 6 h after operation. The adhered platelets, however, did not form a visible and clinically significant thrombus. In long-term experiments, no evidence of thrombus was found in the lumens of the repaired vessels or on the dressings, and no microthrombi were detected histologically in other tissues at any time point. Although vena caval injuries showed signs of healing at day 7 postoperatively, the aortic wounds expanded progressively (pseudoaneurysm) and were prone to rupture at later times. Thus, direct exposure of FSD does not cause intravascular thrombosis or thrombotic events in rabbits. The dressing appears to be safe and effective for short-term repair of vascular injuries. It may also allow healing of minor venous defects, but cannot replace conventional surgical techniques (suturing) for permanent repair of arterial damages.

Severe traumatic injury during long duration spaceflight: Light years beyond ATLS

Traumatic injury strikes unexpectedly among the healthiest members of the human population, and has been an inevitable companion of exploration throughout history. In space flight beyond the Earth's orbit, NASA considers trauma to be the highest level of concern regarding the probable incidence versus impact on mission and health. Because of limited resources, medical care will have to focus on the conditions most likely to occur, as well as those with the most significant impact on the crew and mission. Although the relative risk of disabling injuries is significantly higher than traumatic deaths on earth, either issue would have catastrophic implications during space flight. As a result this review focuses on serious life-threatening injuries during space flight as determined by a NASA consensus conference attended by experts in all aspects of injury and space flight.In addition to discussing the impact of various mission profiles on the risk of injury, this manuscript outlines all issues relevant to trauma during space flight. These include the epidemiology of trauma, the pathophysiology of injury during weightlessness, pre-hospital issues, novel technologies, the concept of a space surgeon, appropriate training for a space physician, resuscitation of injured astronauts, hemorrhage control (cavitary and external), surgery in space (open and minimally invasive), postoperative care, vascular access, interventional radiology and pharmacology.Given the risks and isolation inherent in long duration space flight, a well trained surgeon and/or surgical capability will be required onboard any exploration vessel. More specifically, a broadly-trained surgically capable emergency/critical care specialist with innate capabilities to problem-solve and improvise would be desirable. It will be the ultimate remote setting, and hopefully one in which the most advanced of our societies' technologies can be pre-positioned to safeguard precious astronaut lives. Like so many previous space-related technologies, these developments will also greatly improve terrestrial care on earth.

Effects of primary suture and fib sealant on hemostasis and liver regeneration in an experimental liver injury

AIM: To investigate the effects of fib sealant on hemostasis and liver regeneration and intra-abdominal adhesions in an experimental liver injury.

METHODS: Thirty-six Wistar rats were randomly divided into primary suture group (n = 15), fib sealant group (n = 15) and control group (n = 6). A wedge resection was performed on the left lobe of the liver. In primary suture group, liver was sutured using polypropylene material, while fib glue was administrated on the liver surface in fib sealant group.

RESULTS: More intra-abdominal adhesions were observed in the primary suture group compared to the fib sealant group on 3^rd (2.50 ± 0.5 vs 0.25 ± 0.5, P = 0.015), 10^th (2.75 ± 0.5 vs 0.50 ± 0.6, P = 0.06) and 20^th (1.75 ± 0.5 vs 0.70 ± 0.5, P = 0.015) postoperative days. Histopathological scores were better in the fib sealant group in comparison with the primary suture group on 3^rd (8.75 ± 0.5 vs 6.75 ± 0.5, P = 0.006), 10^th (7.50 ± 1.0 vs 5.5 ± 0.6, P = 0.021) and 20^th (6.40 ± 1.7 vs 3.20 ± 1.6, P = 0.025) postoperative days.

CONCLUSION: Out data suggest that fib sealant is preferred over primary suture in appropriate cases including liver trauma since it causes less intra-abdominal adhesions while allowing shorter hemostasis time as assessed in experimental liver trauma.

High-Pressure Fibrin Sealant Foam: An Effective Hemostatic Agent for Treating Severe Parenchymal Hemorrhage

BACKGROUND

The majority of early trauma deaths are related to uncontrolled, noncompressible, parenchymal hemorrhage from truncal injuries. The purpose of this study was to formulate a fibrin sealant foam (FSF) able to control severe parenchymal bleeding without compression or vascular control.

MATERIALS AND METHODS

FSF with high fibrinogen concentration (20 mg/mL) and low thrombin activity (5 U/mL) was prepared and pressurized by addition of liquid gas propellant. The efficacy of this foam was tested against a severe parenchymal hemorrhage, created by partial resection of liver lobes in anticoagulated rabbits (n = 7) and compared to untreated injury (n = 8) and placebo treatment (n = 7). The hemostatic efficacy of pressurized FSF (n = 8) was also compared to a commercially available liquid fibrin sealant (n = 8) and a developing dry powdered fibrin sealant product (n = 8) in the same model.

RESULTS

The liver injury resulted in 122 +/- 11.5 mL blood loss and death of 75% of untreated rabbits (3.2-3.4 kg) within 1 h. Treatment with placebo foam had no effect on blood loss or mortality rate. Pressurized FSF significantly reduced bleeding, resulting in 56% (P < 0.05) and 66% (P < 0.01) reduction in blood loss as compared to untreated or placebo-treated animals, respectively, and 100% survival (P = 0.008). When pressurized FSF was compared with liquid and powdered forms of fibrin sealant, only foam significantly reduced blood loss (49%, P < 0.05) and mortality rate (54%, P < 0.05) of rabbits as compared to untreated control animals (n = 9).

CONCLUSION

Biological nature, rapid preparation, coverage of large wound areas, and effective hemostatic properties make pressurized FSF an ideal candidate for treating nonoperable parenchymal injuries in damage control procedures.

The role of biological adhesive and suture material on rabbit hepatic injury

PURPOSE: To evaluate the performance of fibrin adhesive and absorbable suture thread in the repairing of hepatic injures in rabbits. METHODS: New Zealand albino rabbits (n=16), males and females, from 5 to 6 months old, average weight of 2500 g, were distributed randomly in Group A (n-8) - biological adhesive and Group B (n=8) - suture thread. After anesthesia with acepromazine (1mg/Kg), ketamine (50mg/Kg) and fentanyl EV (0,5ml/Kg), it was performed a supra-umbilical median laparotomy, the median hepatic lobe was isolated and subjected to severe standardized incision. In the group B the incision edges were sutured with simple 4-0 catgut, in separated stitches. It was evaluated the total time of the procedure, the hemostasis time and hemorrhage volume. In the 21st post-operative day it was evaluated the presence of adherences and signs of infection in the abdominal cavity, and it was followed by the resection of the median hepatic lobe for the histological evaluation. RESULTS: The calculated mean and standard deviation showed that the procedure time, hemostasis time and bleeding amount were significantly smaller in the group of animals subjected to the use of fibrin adhesive. The surgical abdominal incision was significantly more extensive in the animals of the suture group (average of 6,8 cm) in relation to the adhesive group (average of 3,8), as well as the number of occurrences of abscesses. The adherence of the intestinal ansas to the sutured incision (group B) occurred in five cases and the major omentum adhesion occurred in all animals. In the group A (adhesive) it occurred adherences of the major omentum in three cases. The microscopy of the hepatic incision repaired with the use of fibrin showed that the inflammatory infection is less intense, not associated with the formulation of secretion in the abscesses, and therefore has a more favorable later cicatricial aspect than a conventional suture with surgical thread. CONCLUSION: In agreement with other biomedical literature works, the fibrin adhesive is a viable option for the performance of hemostasis in a animal model (rabbit) with severe hepatic injury.

Transfusion vs. alternative treatment modalities in acute bleeding: a systematic review

BACKGROUND AND METHODS

The practice of transfusion varies a great deal between countries and hospitals. Therefore, a systematic literature review was performed to evaluate the evidence underlying practice of transfusion and alternative treatment modalities in acute bleeding. After a stepwise evaluation, 79 out of 2438 abstracts were approved as the evidence base.

RESULTS

Albumin for volume therapy is not better than artificial colloids or crystalloids and may be detrimental in trauma patients. No outcome difference has been proved between artificial colloids and crystalloids. Use of hypertonic solutions remains controversial, as do the concepts of delayed and hypotensive resuscitation. Healthy individuals tolerate acute, normovolaemic anaemia at 5 g haemoglobin/dl, but pre-operative haemoglobin < 6 g/dl gives increased mortality from surgical interventions. Keeping haemoglobin higher than 8-9 g/dl has not been associated with any positive effect on mortality or morbidity, even in patients with cardiovascular disease. The changes induced in erythrocytes by storage may be clinically insignificant. No alternative to erythrocyte transfusion was established. Evidence underlying the practice of thrombocyte and plasma transfusion is scarce. Available evidence on recombinant coagulation factor VIIa is insufficient to define its future role in acute bleedings. Antifibrinolytic drugs in general seem to reduce the need for transfusion.

CONCLUSIONS

Intravenous volume replacement and transfusion policies seem largely based on local tradition and expert opinions. As a result of the difficulties in performing controlled studies in patients with acute bleeding and the large number of patients needed to prove effects, other scientific evidence should be sought to better define best practice in this important field.

Making Sense of the Preclinical Literature on Advanced Hemostatic Products

A number of new hemostatic products have been developed recently for use in trauma settings of severe uncontrolled bleeding. Currently, the literature on these products is controversial, with efficacy demonstrated under some circumstances but not others. In this review, we analyze the current literature pertaining to four of the most promising products (dry fibrin sealant dressing, Rapid Deployment Hemostat, HemCon chitosan dressing, and QuikClot) that have been suggested for use in combat casualty care applications. In particular, this analysis takes into account the characteristics of the animal models used for efficacy testing of these products, the desired characteristics of hemostatic dressings, and specific safety considerations. Animal models ranged from those featuring low-pressure/low-flow bleeding to those featuring high-pressure/high-flow bleeding. When data are viewed in the context of the specific characteristics of the differing animal models used, seemingly disparate experimental results related to efficacy and safety become quite complementary and lead to recommendations for the use of different products in different injury scenarios. Mission and training requirements will dictate the use of these products by military and civilian prehospital care providers.

Comparison of Hemorrhage Control Agents Applied to Lethal Extremity Arterial Hemorrhages in Swine

BACKGROUND

QuikClot powder (QC), chitosan dressing (CD), and fibrin sealant dressing (FSD) are new hemostatic products touted to be more effective in controlling severe extremity bleeding than the current standard gauze dressing. All have been utilized in the global war on terrorism. Our objective was to evaluate the hemostatic efficacy of these three products in a model of severe extremity arterial hemorrhage that could not be stopped by standard gauze treatment.

METHODS

A model of severe extremity arterial hemorrhage was developed in swine that was 100% fatal with standard gauze application and manual compression. The Army Field Bandage (AFB) was the standard gauze control. Anesthetized animals (n = 60, 15/group, 37.7 +/- 2.5 kg) were splenectomized and instrumented. A reproducible femoral artery injury was created using a 6 mm aortic punch, and free bleeding was allowed for 45 seconds. Each hemostatic agent was applied twice with three-minute compressions. All products were applied on actively bleeding wounds through a pool of blood. Fluid resuscitation was started with the first compression and titrated to a mean pressure of 65 mm Hg. Animals were observed for 180 minutes or until death. Endpoints were percent survival, survival time, blood loss, resuscitation volume, wound temperatures and tissue histology. Data are expressed as mean +/- SD and analyzed by Fisher's exact, logrank, and nonparametric ANOVA tests.

RESULTS

Baseline physiologic parameters were similar among groups. AFB did not produce hemostasis. QC also showed no hemostatic benefit, and QC treatment markedly increased maximum wound temperatures to an average of 70.8 +/- 4.2 degrees C (p < 0.001). CD stopped bleeding temporarily in only one animal. There were no survivors in the AFB, QC, or CD groups. CD numerically prolonged survival time (58.9 +/- 21.1 minute) compared with the control (38.4 +/- 24.7 minutes, p = 0.045) but the difference was not significant. FSD reduced bleeding (p < 0.05) and prevented exsanguination in 10/15 (2/3) animals, and resulted in a significantly longer average survival time (p < 0.0001).

CONCLUSION

FSD was superior to other currently utilized hemostatic products in controlling lethal arterial hemorrhage in this model of a fatal extremity wound. CD showed some hemostatic benefit. The exothermic reaction of QC was significant and resulted in gross and histologic tissue changes of unknown clinical significance. Controlled human studies with the promising products are required.

A Salmon Thrombin-Fibrin Bandage Controls Arterial Bleeding in a Swine Aortotomy Model

BACKGROUND

Recently, a wide variety of bandages have been formulated to attempt to improve the effectiveness of emergency intervention in situations of uncontrolled bleeding. The best of these dressings contain a mixture of human thrombin and fibrinogen. The presence of human components in these bandages, although effective, increases the cost of the dressing and raises questions of availability of raw materials and transmission of pathogens. The purpose of this study was to investigate the efficacy of dressings composed of salmon thrombin and fibrinogen in a swine aortotomy model.

METHODS

A 4.4-mm aortotomy was produced in the abdominal aorta of 19 anesthetized, splenectomized swine. The United States Army standard field gauze was applied to 8 animals, and the salmon thrombin-fibrin dressing (SFD) was applied to 11 animals. Survival, blood loss, and other parameters were measured over a 60-minute period.

RESULTS

All 11 animals that received the SFD survived the aortotomy injury, and bleeding stopped within 7.5 +/- 1.5 min. Seven of 8 animals in the control group were killed when bleeding continued and blood pressures decreased to the cutoff values as outlined in the animal protocol. Bleeding was significantly less in the SFD group compared with the gauze group (241 +/- 65.3 vs. 932.7 +/- 142.4 mL).

CONCLUSION

Fibrin dressing using salmon-derived thrombin and fibrinogen is effective in controlling severe, uncontrolled bleeding. This dressing may offer an alternative to dressings composed of human coagulation proteins.

Effect of Recombinant FVIIa in Hypothermic, Coagulopathic Pigs with Liver Injuries

BACKGROUND

Previous experiments with diverse pig models to evaluate the ability of rFVIIa to reduce hemorrhage have provided divergent results. The current study was conducted to address concerns related to previous work by using larger sample sizes, and an extended observational period of 4 hours post-injury. The objectives were to evaluate further the hemostatic efficacy and safety of rFVIIa administration after traumatic, uncontrolled hemorrhage.

METHODS

Anesthetized, splenectomized pigs (36.6 +/- 0.3 kg; n = 18/group) underwent an approximately 50% isovolemic blood exchange with 33 degrees C 6% hetastarch, and body temperature was adjusted to 32.5 +/- 0.5 degrees C. Subsequently, a Grade V liver injury was inflicted. After 30 seconds, either vehicle or treatment (180 microg/kg or 720 microg/kg rFVIIa) was administered intravenously as a bolus. Concomitantly, laparotomy pads were packed around the liver. Resuscitation with 33 degrees C lactated Ringer's solution (260 mL/min) was initiated and pigs were monitored for 4 hour post-injury or until death. Tissues were collected and examined histologically to assess the presence of disseminated intravascular coagulation (DIC).

RESULTS

Liver injuries were comparable among all groups (p = 0.89). Measures associated with in vitro coagulation (prothrombin time, activated partial thromboplastin time, thromboelastographic split-point and R times) were enhanced by rFVIIa administration (p < 0.05). However, neither percent survival (p = 0.82), survival time (p = 0.56), nor blood loss (p = 0.63) were affected by treatment. DIC was not evident in lung or kidney tissue.

CONCLUSIONS

These data indicate an inability of rFVIIa at these doses to reduce blood loss, or to increase survival time or percent survival in this pig model. Absence of DIC provides evidence for safe use of rFVIIa under conditions specific to this study.

Hemostatic Efficacy of Two Advanced Dressings in an Aortic Hemorrhage Model in Swine

BACKGROUND

An effective hemostatic agent capable of stopping severe arterial bleeding and sustaining hemostasis over a prolonged time is required. The U.S. Army recently distributed fibrin sealant (under an Investigational New Drug-approved protocol) and chitosan dressings among deployed medics for treating severe external hemorrhage on the battlefield. The purpose of this study was to evaluate the efficacy of these dressings, as compared with the standard gauze army field dressing, to provide initial and sustained hemostasis up to 96 hours in a lethal uncontrolled arterial hemorrhage model.

METHODS

Anesthetized pigs were splenectomized and chronically instrumented for fluid/drug administration and continuous monitoring of vital signs. An infrarenal aortotomy was created using a 4.4-mm aortic hole punch and free bleeding was allowed for 5 seconds. While bleeding profusely, a dressing was applied and pressed into the wound for 4 minutes (occluding the distal flow) and then released. If hemostasis was not obtained, the dressing was replaced with a new one (maximum, two dressings per experiment) with another 4-minute compression. If hemostasis was achieved, the abdomen was closed; the animal was then recovered and monitored up to 96 hours. Initial hemostasis, duration of hemostasis, survival time, blood loss, and other variables were measured.

RESULTS

Application of army field dressing (gauze) did not stop the arterial hemorrhage and led to exsanguination of all the pigs (n = 6) within 10 to 15 minutes of the injury. Chitosan dressing produced initial hemostasis in five of seven pigs. However, the dressings failed to maintain hemostasis for more than 1.6 hours (range, 28-102 minutes), resulting in secondary bleeding and death of the animals. Fibrin sealant dressing produced initial hemostasis in all the pigs (n = 6) and maintained hemostasis in five cases, with one failure at 2.2 hours. These pigs resumed normal activities and lived for the 96-hour experiment duration. Computed tomographic images and histologic sections of the aortas from surviving fibrin sealant dressing-treated animals showed formation of pseudoaneurysms and early granulation tissue at the aortotomy site. The posttreatment blood loss, duration of hemostasis, and survival time were significantly different in the fibrin sealant dressing group than the chitosan dressing and army field dressing groups.

CONCLUSION

Both chitosan dressing and fibrin sealant dressing stopped initial arterial bleeding that could not be controlled by the standard army field dressing. However, although the fibrin sealant dressing secured hemostasis for up to 4 days, the chitosan dressing consistently failed within 2 hours after application. There may be a risk of rebleeding for high-pressure arterial wounds treated with chitosan dressings, particularly in situations where definitive care is delayed substantially.