Abstract
Uncontrolled hemorrhage shock is the highest treatment priority for military trauma surgeons. Injuries to the torso area remain the greatest treatment challenge, since external dressings and compression cannot be used here. Bleeding control strategies may thus offer more effective haemostatic management in these cases. Chitosan, a linear polysaccharide derived from chitin, has been considered as an ideal material for bleeding arrest. This study evaluated the potential of chitosan-based dressings relative to commercial gauze to minimize femoral artery hemorrhage in a swine model. Stable haemostasis was achieved in animals treated with chitosan fibre (CF) or chitosan sponge (CS), resulting in stabilization of mean arterial pressure and a substantially higher survival rate (100% vs. 0% for gauze). Pigs receiving treatment with CF or CS dressings achieved haemostasis within 3.25 ± 1.26 or 2.67 ± 0.58 min, respectively, significantly more rapidly than with commercial gauze (>100 min).
Moreover, the survival of animals treated with chitosan-based dressings was dramatically prolonged (>180 min) relative to controls (60.92 ± 0.69 min). In summary, chitosan-based dressings may be suitable first-line treatments for uncontrolled hemorrhage on the battlefield, and require further investigation into their use as alternatives to traditional dressings in pre-hospital emergency care.
Introduction
Moderate to severe battlefield injury and hemorrhage is the highest treatment priority for military trauma surgeons and researchers. Traumatic hemorrhage of military personnel injured in the line of duty accounts for more than 40% of pre-hospitalization deaths within the first 24 hours of injury (1). In addition, uncontrolled hemorrhage is the second leading cause of death in civilian trauma patients (1–4). Life-threatening coagulopathy is frequently observed in severe trauma patients. Trauma-associated coagulopathy is caused by metabolic acidosis, hypothermia, and dysfunctional clot formation. Moreover, immediate complications such as multiple organ failure may result from prolonged hypotension, sepsis, and plasma product transfusion (5–8).
According to statistics from a previous study, approximately 24% of deaths resulting from combat could have been prevented with immediate and effective treatment (9). Most of these victims died because of preventable compressible or non-compressible hemorrhaging. Therefore, it is critical to develop a first-line measure to control hemorrhage.
Since 2003, several haemostatic products have been developed to treat compressible hemorrhages arising from battlefield injuries. However, 15% of battlefield injuries occur to the torso area (chest, abdomen, pelvis, and back), where external dressings and compression are not useful (10,11). Hemorrhage control seems to be a promising approach to avoiding this problem, so studying bleeding control may suggest effective haemostatic methods that could save lives during the acute emergency phase. The haemostatic efficacy and acute safety of haemostatic dressings have been tested in swine on groin arterial hemorrhages that could not be controlled with standard surgical cotton gauze. These dressings are most promising, since they allow precise application even under extremely cold temperatures or insufficient light conditions.
Currently, there are more than 10 commercially available chitosan-based dressings that are utilized in the acute emergency phase. Chitosan haemostatic dressings are superior to traditional granular/powder agents due to their effective bleeding arrest, ease of use, and precise application to deep, penetrating wounds, as well as possible antibacterial properties and regeneration-stimulating effects (12). In this context, we tested two novel chitosan-based dressings, chitosan fibre (CF) and chitosan sponge (CS), for use as first aid measures in a swine model of standard arterial hemorrhage. These dressings are made from poly-D-glucosamine and poly-N-acetyl glucosamine derived from natural organic chitosan. Chitosan is a linear amino polysaccharide produced by deacetylation of naturally occurring chitin and exhibits interesting biological, physiological, and pharmacological properties.
Chitosan is rich in glycosaminoglycan, which participates in cell–cell and cell–matrix interactions, cell proliferation and migration, and in cytokine and growth factor signalling, thus locally modulating biologic activities (13). Major bioactivities include the promotion of wound healing, haemostatic activity, immunity enhancement, hypolipidemic activity, mucoadhesion, and antimicrobial activity. Despite its low water solubility, chitosan has become a common substance in biomaterials research and has been used for several applications in the biomedical field.
The soft, non-woven CF dressing is made of chitosan fibres that can accelerate haemostasis and wound care during arterial hemorrhage. With its unique flexibility, the CF dressing is suitable for various wound surfaces, regardless of location, size, sinus, or depth. Chitosan fibre manufacturing techniques have been established during the past two decades. Generally, CF dressing is prepared using a wet-spinning process that produces fibres by dissolving the polymer in a solvent (e.g. acetic acid), after which the polymer solution is extruded via dies into a non-solvent (e.g. aqueous sodium hydroxide). The polymer precipitate emerges in the form of fibres that can be washed, drained, and dried. The CF dressing uses the properties of chitosan fibres to combine an adequate porous structure with excellent degradability and mechanical properties.
The CS dressing, which is a light-yellow sponge, is made of natural organic chitosan particles and can be comfortably attached to the skin to seal a wound. Generally, CS dressing is prepared using a freeze-drying method, resulting in a sponge-like form. It keeps the wound sterile for as long as seven days. Additionally, the porosity of the CS dressing allows rapid absorption of a large volume of exudate from the injury site. Following absorption, the exudate interacts with the CS dressing to form a moist environment covering the wound for up to seven days.
This study aims to compare the efficacy of chitosan-based dressings and commercial gauze in a swine model. We explored the potential of these two chitosan-based dressings to minimize femoral artery hemorrhage and achieve immediate haemostasis in a swine model. Based on our results, chitosan-based dressings require further study as alternatives to traditional dressings in pre-hospital emergency care.
The present study shows that the CF and CS dressings achieved haemostasis effectively, rapidly controlling moderate-to-severe hemorrhage, which represented a great improvement over commercial gauze. The reduced bleeding time resulted in less blood loss and a lower fluid resuscitation rate. It is reasonable to postulate that the large blood loss with commercial gauze, and the subsequent high fluid resuscitation rate, reduced the clotting
capacity of the blood, leading to unfavorable outcomes. Both chitosan-based dressings exhibited similar efficacy even in the presence of anticoagulants in the blood. Therefore, we hypothesize that interactions between the positively charged ions in the chitosan and the negatively charged ions in red blood cell membranes may enhance haemagglutination and encourage platelet adhesion and activation via protein adsorption and orientation, thus affecting cellular responses to proteins (14,15). It has also been demonstrated that the porosity of this dressing facilitates higher ventilation over the injury site, allowing more oxygen to diffuse inward across the skin, thereby stimulating the healing process.
Chitosan characteristically carries cations such as -NH3 +, which have a positive effect on haemostasis. If attached to the surface of the chitosan-based dressing, the metal cation–chitosan complex enhances the adhesion of erythrocytes and platelets to the injury site. Chitosan also improves blood coagulation efficiency (either stopping bleeding or controlling hemorrhage). Indeed, it appears to demonstrate better haemostatic efficacy than traditional granular/powder agents, even in the presence of anticoagulants such as heparin. Once the bleeding has stopped, the dressing would then form an antibacterial layer to prevent wound infections and provide an appropriate wound-healing environment. Further, such dressings are compatible with human skin and possess properties that allow ventilation of the wound and absorption of the wound exudate. Previous studies have also demonstrated the safety of chitosan. The biocompatibility and biodegradability of chitosan, combined with its haemostatic and anti-infection activity, make it highly useful and advantageous for use in wound dressings.
The swine model of femoral artery hemorrhage we used in this study represented a severe injury to the groin area with partial destruction of the femoral artery, causing a life-threatening hemorrhage that is impossible to control with commercial gauze, and not manageable using a tourniquet. The strength to this study was that the surgical procedures were performed by a researcher who was blinded to group assignment, which increases confidence in the outcome.
Although our approach represents a reliable model for examining the efficacy of haemostatic dressings, there are some limitations of this study that should be addressed in future research.
- Firstly, considering there are many different types of gauze available for haemostatic management of bleeding, the results in this study can be influenced by the gauze type.
- Secondly, we are unable to establish a comprehensive comparison between chitosan-based dressings and gauze because of lack of packing time in this study. Although chitosan-based dressings significantly reduced time to haemostasis as compared with control, they require more time for packing according to the procedure.
- Thirdly, this model does not fully mimic battlefield or accident-induced traumatic injuries. The efficacy of the dressings could be affected by changes in environmental or wound conditions.
- Lastly, given our small sample size (3 different dressings on 10 animals), this should be followed up with additional studies using a larger sample size.
Currently, the biomedical application of most synthetic polymers is limited by insufficient biocompatibility and poor biodegradability. In contrast, natural polymers such as cellulose, chitin, chitosan, and their derivatives have been proven to be biocompatible and biodegradable. Furthermore, the degradation product of chitosan is nontoxic to humans (16).
Chitosan is also useful as a supporting material for tissue engineering. Previous studies have revealed that both chitosan and chitosan oligomers exhibit antibacterial activity, and that chitosan displays greater antibacterial activity than chitosan oligomers (17,18). Potential future directions should include conducting chitosan-based dressings testing in more challenging animal models, combining chitosan with other materials to achieve stable haemostasis, and modifying the dressings to facilitate handling to further reduce the packing time.
In summary, a large amount of effort has been invested in the investigation of novel haemostatic products. In this study, a swine model of femoral artery hemorrhage was utilized to evaluate the efficacy of CF and CS dressings. This model mimicked a severe injury to the groin area with partial destruction of the femoral artery, causing a life-threatening hemorrhage that is impossible to control with commercial gauze and not manageable with a tourniquet. The results revealed that both CF and CS dressings reduced the time to haemostasis and the fluid resuscitation rate relative to commercial gauze, and the CF- and CS-treated animals survived significantly longer than the control animals. Additionally, the two types of chitosan dressing were equally efficacious in mitigating blood loss and promoting survival.
Based on these findings, CF and CS dressings may be suitable first-line treatments for uncontrolled haemorrhage on the battlefield, and require further investigation into their use as alternatives to traditional dressings in pre-hospital emergency care.
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