Efficacy of a novel hemostatic agent in animal models of impaired hemostasis

Engineered Hemostatic Biomaterials for Sealing Wounds

Hemostatic biomaterials show great promise in wound control for the treatment of uncontrolled bleeding associated with damaged tissues, traumatic wounds, and surgical incisions. A surge of interest has been directed at boosting hemostatic properties of bioactive materials via mechanisms triggering the coagulation cascade. A wide variety of biocompatible and biodegradable materials has been applied to the design of hemostatic platforms for rapid blood coagulation. Recent trends in the design of hemostatic agents emphasize chemical conjugation of charged moieties to biomacromolecules, physical incorporation of blood-coagulating agents in biomaterials systems, and superabsorbing materials in either dry (foams) or wet (hydrogel) states. In addition, tough bioadhesives are emerging for efficient and physical sealing of incisions. In this Review, we highlight the biomacromolecular design approaches adopted to develop hemostatic bioactive materials. We discuss the mechanistic pathways of hemostasis along with the current standard experimental procedures for characterization of the hemostasis efficacy. Finally, we discuss the potential for clinical translation of hemostatic technologies, future trends, and research opportunities for the development of next-generation surgical materials with hemostatic properties for wound management.

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.

Does fibrin sealant applied to the kidney wound of a young rat affect the development of this organ? A comparative study

OBJECTIVE

The aim of the study was to compare the results of the application of fibrin sealant and absorbable interrupted sutures and to evaluate the impact of the kidney wound closure method on the further development of the organ in young rats.

MATERIALS AND METHODS

In 140 rats, a longitudinal bipolar incision of the renal parenchyma was made. In the study group the wound was closed using a fibrin sealant, whereas in the control group single absorbable sutures were applied to the renal parenchyma. Intravenous pyelography, postmortem and histopathological examinations were carried out 4 weeks and 6 months after the surgery.

RESULTS

The blood loss was smaller and the time of procedure shorter in the study group than in controls, and the differences were statistically significant. Both 4 weeks and 6 months after the surgery, the differences in the kidney dimensions and kidney weight between the two groups were statistically significant. The differences increased after a longer period of time following the surgery. The histopathological examination revealed that in the case of animals with surgical sutures applied to the wound, the rate of resorptive granulomas and abscess formation was higher, whereas kidneys with fibrin sealant applied to the wound featured a high number of lymphocytic infiltrations of minor severity.

CONCLUSIONS

The application of the fibrin sealant simplified the surgical procedure, shortened its duration, and provided hemostasis and permanent closure of the wound. The fibrin sealant facilitates the process of wound healing. The application of a fibrin sealant, compared to surgical sutures, improved the growth of rat kidneys without impairing their functions.

Evaluation of a gelatin matrix as a topical hemostatic agent for hepatic bleeding in the dog

New generation topical hemostatic agents containing thrombin have been developed for use in surgical procedures when control of bleeding by conventional methods is either ineffective or impractical. The authors compared the safety, hemostatic efficacy, and handling characteristics of a thrombin-containing topical surgical hemostatic agent (a gelatin matrix) to a hemostatic gelatin sponge for treatment of parenchymal bleeding after liver biopsy. Fourteen dogs were enrolled in this prospective clinical study. Paired 1.5 cm × 1.5 cm and 0.5 cm deep liver biopsies were obtained via laparotomy for each dog. One bleeding liver biopsy lesion was treated with the gelatin matrix and the other with a gelatin sponge. The treated liver biopsy sites were compared for bleeding severity, time to hemostasis, cumulative blood loss, and hemostatic agent handling characteristics. Median time to hemostasis was significantly shorter (P = 0.034) and median cumulative blood loss was significantly lower (P = 0.033) for the lesions treated with the gelatin matrix than the gelatin sponge. Adverse reactions were not observed within the first 24 hr postoperatively. When used to control parenchymal bleeding from liver biopsy sites in the dog, the evaluated gelatin matrix was safe and more effective than the gelatin sponge.

Topical haemostatic agents

BACKGROUND

A variety of local haemostatic agents is now available to stop troublesome bleeding. These agents are indicated for use during surgical interventions where conventional methods of haemostasis are not applicable because of the site of surgery or the degree of bleeding.

METHOD

A literature search using the PubMed and ISI Web of Knowledge databases identified relevant studies on topical haemostatic agents. Manufacturers' recommendations were also sought through commercial websites.

RESULTS AND CONCLUSION

A significant body of evidence now exists to support the use of topical haemostatic agents in a wide variety of clinical situations. The advantages and disadvantages of many of these agents are highlighted.

The Combination of Platelet-Enriched Autologous Plasma with Bovine Collagen and Thrombin Decreases the Need for Multiple Blood Transfusions in Trauma Patients with Retroperitoneal Bleeding

OBJECTIVES

Bleeding from blunt and penetrating retroperitoneal injuries during operative exploration are often difficult to control surgically and can be associated with significant blood loss. Our goals were to evaluate and compare the efficacy of a topical autologous platelet-enriched plasma combined with bovine collagen and thrombin (PCT) to Gelfoam/thrombin (G/T) in relation to hemostatic control/blood transfusion (BTx) requirements and subsequent outcome.

METHODS

Prospective data were collected on all patients who underwent operative exploration for retroperitoneal injuries in which either PCT or G/T was applied with or without packing over a 2.5-year period. Patients were stratified by age, gender, mechanism of injury, preoperative international normalized ratio, pH, hematocrit, intraoperative blood loss, and BTx requirements. Subsequent BTx requirements were calculated within 48 hours of the surgical procedure. Outcome was measured by intensive care unit and hospital length of stay and mortality.

RESULTS

A total of 78 patients met study criteria. Patients who received G/T had a significantly greater number of early postoperative transfusions (p < 0.001) and a longer hospital (p < 0.001) and intensive care unit length of stay (p < 0.007). There was no difference in mortality.

CONCLUSION

PCT is a rapidly available topical hemostat that is associated with a significant decrease in the need for postoperative blood transfusions and intensive care unit and hospital length of stay. A randomized prospective trial to confirm these results is warranted.

Evaluation of a novel hemostatic device in an ovine parenchymal organ bleeding model of normal and impaired hemostasis

Bleeding is a problem encountered by many surgeons, often complicated by the presence of coagulopathy or anticoagulant. The hemostatic effectiveness of CoStasis Surgical Hemostat (with bovine collagen, bovine thrombin, and autologous plasma) was evaluated and compared to a collagen sponge and to two investigational fibrin-sealant preparations under conditions of normal and impaired coagulation. A liver resection and controlled incisions in spleens and kidneys were made in sheep. Time to complete hemostasis and total blood loss were measured. Tissue response was evaluated at 7, 30, 60, and 75 days. CoStasis-treated sites demonstrated significantly shorter time to hemostasis (all surgical sites combined) compared with fibrin sealant (investigational fibrin sealant 1) (p= .005) or collagen sponge (p=0.013). In anticoagulated animals, CoStasis and fibrin sealant (investigational fibrin sealant 2) had comparable mean times to hemostasis, and CoStasis-treated sites exhibited lowered average blood loss compared to investigational fibrin-sealant-2 treated sites. CoStasis-treated sites demonstrated higher levels of tissue repair (lower inflammation, more extensive tissue repair, and less residual implant) compared to fibrin-sealant- or collagen-sponge-treated sites in Phases I and II. These findings demonstrate that CoStasis is a highly effective hemostatic agent for control of bleeding from parenchymal organs. Furthermore, under conditions of compromised coagulation, treatment with CoStasis demonstrates a reduction in average blood loss when compared to treatment with fibrin sealant.

Development of an animal model for assessment of the hemostatic efficacy of fibrin sealant in vascular surgery

PURPOSE

Sustained hemostatic function of fibrin sealant (FS) is crucial when it is used in cardiovascular surgery. The purpose of this study was to develop a model that can determine the long-term hemostatic efficacy of tissue sealants in a vascular surgery.

METHODS

To determine the ability of the model to detect differences in FS performance, various concentrations of FS were prepared and tested. Tensile strength of FS clots was determined in vitro using a tensiometer. Laparotomy was performed on 49 anesthetized rabbits, and a segment of the aorta was occluded, transected, and then sutured in an end-to-end fashion with four or eight interrupted 9-O sutures. The four-suture repair was covered with FS or placebo, and blood flow restored. Spilled blood was absorbed with gauze and weighed to estimate blood loss. Four weeks after surgery the animals were euthanized and the vessels recovered for histology.

RESULTS

Average tensile strength of FS clots at 120, 90, and 60 mg/ml topical fibrinogen complex (TFC) concentration was 0.42 +/- 0.07 N, with no significant difference among them. The lowest TFC concentration, 30 mg/ml, produced weaker clots than either 120 or 90 mg/ml (P < 0.05). All rabbits with four-suture anastomoses that were treated with placebo bled to death after the vessel was unclamped (n = 6). Treatment of suture line with standard FS concentration (120 mg/ml TFC, n = 8) sealed the anastomosis and prevented blood loss. Hemostasis was sustained for 4 weeks, allowing vascular healing. All rabbits with the eight-suture anastomosis survived the operation but lost 42 +/- 9.2 ml blood (n = 5). Hemostatic efficacy of FS was unchanged when TFC was diluted to 90 mg/ml (n = 6) but further dilution to 60 mg/ml with water (n = 8) produced significantly less effective clots, with an average blood loss of 5.5 +/- 7.6 ml (P < 0.05) and two fatal clot failures postoperatively. When FS was diluted to 60 mg/ml TFC with a buffer, it maintained its hemostatic strength (n = 6). Further TFC dilution to 30 mg/ml led to consistent bleeding with an average blood loss of 35.3 +/- 10.3 ml (P < 0.001, n = 6).

CONCLUSIONS

The four-suture anastomosis of rabbit aorta offers a consistent and reliable method for evaluating the short- and long-term hemostatic efficacy of FS products. This model is not only able to determine the functional differences in various concentrations of FS, but it is also sensitive to detect the subtle changes in FS preparation (e.g., medium composition) that is not detected by in vitro testing.