An autologous blood-derived patch as a hemostatic agent: evidence from thromboelastography experiments and a porcine liver punch biopsy model

Perioperative bleeding is a common complication in surgeries that increases morbidity, risk of mortality, and leads to increased socioeconomic costs. In this study we investigated a blood-derived autologous combined leukocyte, platelet, and fibrin patch as a new means of activating coagulation and maintaining hemostasis in a surgical setting. We evaluated the effects of an extract derived from the patch on the clotting of human blood in vitro, using thromboelastography (TEG). The autologous blood-derived patch activated hemostasis, seen as a reduced mean activation time compared to both non-activated controls, kaolin-activated samples, and fibrinogen/thrombin-patch-activated samples. The accelerated clotting was reproducible and did not compromise the quality or stability of the resulting blood clot. We also evaluated the patch in vivo in a porcine liver punch biopsy model. In this surgical model we saw 100% effective hemostasis and a significant reduction of the time-to-hemostasis, when compared to controls. These results were comparable to the hemostatic properties of a commercially available, xenogeneic fibrinogen/thrombin patch. Our findings suggest clinical potential for the autologous blood-derived patch as a hemostatic agent.

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.

Characterization of shape memory polymer foam hemostats in in vitro hemorrhagic wound models

Shape memory polymer foam hemostats are a promising option for future hemorrhage control in battlefield wounds. To enable their use as hemostatic devices, they must be optimized in terms of formulation and architecture, and their safety and efficacy must be characterized in animal models. Relevant in vitro models can be used for device optimization to help mitigate the excess use of animals and reduce costs of clinical translation. In this work, a simplified gunshot wound model and a grade V liver injury model were constructed. The models were used to characterize the effects of shape memory polymer foam hemostat geometry on wall pressures, application/removal times, hemorrhage (fluid loss), and fluid absorption in comparison with clinical controls. It was found that there is no benefit in over-sizing the hemostatic device relative to wound volume and that geometry effects are dependent upon the wound type. These models provide a rapid means for elucidation of promising hemostat geometries and formulations for use in future in vivo testing.

Determination of efficacy of novel modified chitosan sponge dressing in a lethal arterial injury model in swine

BACKGROUND

Chitosan is a functional biopolymer that has been widely used as a hemostat. Recently, its efficacy has been questioned due to clinical failures as a result of poor adhesiveness. The purpose of this study was to compare, in a severe groin injury model in swine, the hemostatic properties of an unmodified standard chitosan sponge with standard gauze dressing and a novel hydrophobically modified (hm) chitosan sponge. Previous studies have demonstrated that hm-chitosan provides greatly enhanced cellular adhesion and hemostatic effect via noncovalent insertion of hydrophobic pendant groups into cell membranes.

METHODS

Twenty-four Yorkshire swine were randomized to receive hm-chitosan (n = 8), unmodified chitosan (n = 8), or standard Accu-Sorb gauze dressing (n = 8) for hemostatic control. A complex groin injury involving arterial puncture (4.4-mm punch) of the femoral artery was made after splenectomy. After 30 seconds of uncontrolled hemorrhage, the randomized dressing was applied and compression was held for 3 minutes. Fluid resuscitation was initiated to achieve and maintain the baseline mean arterial pressure and the wound was inspected for bleeding. Failure of hemostasis was defined as pooling of blood outside the wound. Animals were then monitored for 180 minutes and surviving animals were killed.

RESULTS

Blood loss before treatment was similar between groups (p < 0.1). Compared with the hm-chitosan sponge group, which had no failures, the unmodified chitosan sponge group and the standard gauze group each had eight failures over the 180-minute observation period. For the unmodified chitosan sponge failures, six of which provided initial hemostasis, secondary rebleeding was observed 44 minutes ± 28 minutes after application. Standard gauze provided no initial hemostasis after the 3-minute compression interval.

CONCLUSIONS

Hm-chitosan is superior to unmodified chitosan sponges (p < 0.001) or standard gauze for controlling bleeding from a lethal arterial injury. The hm-chitosan technology may provide an advantage over native chitosan-based dressings for control of active hemorrhage.

Intracorporeal use of advanced local hemostatics in a damage control swine model of grade IV liver injury

BACKGROUND

The purpose of this study was to evaluate the efficacy of zeolite- and chitosan-based local hemostatic agents for the control of intracorporeal bleeding in a damage control swine model of grade IV liver injury.

METHODS

Anesthetized pigs (weight, 40 kg) had a controlled 35% total blood volume bleed from the right jugular vein. A laparotomy was performed and the animals were cooled to 35°C. Ringer's lactate was titrated to achieve a three to one blood withdrawal resuscitation. The liver was injured with a standardized 10 cm × 3 cm avulsion. After 2 minutes of uncontrolled hemorrhage, the animals were randomized to application of gauze control (GC, n = 11), Celox (CX, n = 11) (5AM Medical, Newport, OR), or QuikClot ACS (QC, n = 11) (7-Medica, Wallington, CT) and packed in a standardized manner. At 10 minutes, the packs were removed to calculate amount of shed blood. The animals then underwent damage control closure with packing in place. Forty-eight hours after initial damage control packing, the animals were returned to the operating room for pack removal and killing. The need for repacking of the liver was assessed and tissue samples were collected from the liver edge and adjacent small bowel for histopathology.

RESULTS

There was no difference in the amount of uncontrolled bleeding at 2 minutes (GC: 4.0 mL/kg ± 0.4 mL/kg, CX: 3.5 mL/kg ± 0.5 mL/kg, QC: 4.0 mL/kg ± 0.6 mL/kg; one-way analysis of variance: p = 0.715). Compared with GCs, the blood loss at 10 minutes was significantly lower in the CX and QC arms (GC: 8.3 mL/kg ± 0.9 mL/kg, CX: 3.7 mL/kg ± 0.7 mL/kg, QC: 4.6 mL/kg ± 0.8 mL/kg; one-way analysis of variance: p = 0.001). A total of 27.3% of control animals died compared with 18.2% of CX and 0.0% of QC. All GC and QC animals required repacking, compared with one (9.1%) of those in the CX arm. There was no difference between groups in the extent of necrosis.

CONCLUSION

Celox and QuikClot ACS(+) are effective adjuncts to standard intracavitary damage control packing for the control of bleeding. Celox provided durable control allowing packing removal at the time of take-back laparotomy. Further evaluation of their long-term effects is warranted.

Review of antimicrobial and antioxidative activities of chitosans in food

Interest in chitosan, a biodegradable, nontoxic, non-antigenic, and biocompatible biopolymer isolated from shellfish, arises from the fact that chitosans are reported to exhibit numerous health-related beneficial effects, including strong antimicrobial and antioxidative activities in foods. The extraordinary interest in the chemistry and application in agriculture, horticulture, environmental science, industry, microbiology, and medicine is attested by about 17,000 citations on this subject in the Scopus database. A special need exists to develop a better understanding of the role of chitosans in ameliorating foodborne illness. To contribute to this effort, this overview surveys and interprets our present knowledge of the chemistry and antimicrobial activities of chitosan in solution, as powders, and in edible films and coating against foodborne pathogens, spoilage bacteria, and pathogenic viruses and fungi in several food categories. These include produce, fruit juices, eggs and dairy, cereal, meat, and seafood products. Also covered are antimicrobial activities of chemically modified and nanochitosans, therapeutic properties, and possible mechanisms of the antimicrobial, antioxidative, and metal chelating effects. Further research is suggested in each of these categories. The widely scattered data on the multifaceted aspects of chitosan microbiology, summarized in the text and in 10 tables and 8 representative figures, suggest that low-molecular-weight chitosans at a pH below 6.0 presents optimal conditions for achieving desirable antimicrobial and antioxidative-preservative effects in liquid and solid foods. We are very hopeful that the described findings will be a valuable record and resource for further progress to improve microbial food safety and food quality.