Thrombin is a naturally derived enzyme that has been widely characterized for its roles in hemostasis, inflammation, and cell signaling. Thrombin has been purified from numerous sources and used as a ...clinical aid for topical hemostasis for more than 60 years. Due to both its ease of use and apparent effectiveness, thrombin has become used routinely as an aid for topical hemostasis in nearly all types of surgical procedures, including but not limited to cardiovascular, orthopedic, neurologic, general, gynecologic, and dental procedures. Due to the widespread acceptance of thrombin in the surgical setting, it is conservatively estimated that at least 1 million patients in the United States are treated with topical applications of thrombin each year. Although the U.S. Food and Drug Administration (FDA) has approved a wide array of topical and biologic products to stop surgical bleeding, the only thrombin that is currently FDA approved as a stand-alone hemostatic product in the United States is derived from bovine sources. Bovine-derived thrombin has potent biologic activity in its ability to convert fibrinogen to fibrin, activate platelets, and induce vascular contraction. However, it has also been shown to induce a robust immune response following human exposure. Numerous reports have documented an array of clinical events that follow bovine thrombin exposure, which include the development of antibodies against thrombin, prothrombin, factor V, and cardiolipin. In some well-described cases, these antibodies have led to clinical syndromes that range from severe postoperative bleeding to high rates of vascular bypass graft thrombosis. Furthermore, experimental applications of bovine thrombin to various strains of mice have induced a postexposure autoimmune syndrome that was pathologically identical to lupus. Thrombin-derived products are well accepted by the surgical community for use as an aid for hemostasis, but the bovine-derived products have an unacceptably high and unnecessary association with immunologic side effects. If a nonimmunologic and effective thrombin were developed, one would expect it to be rapidly adopted by the clinical community.
Objectives Vascular access dysfunction is the major cause of morbidity in patients on hemodialysis to treat end stage renal disease. Preclinical studies have demonstrated that the perivascular ...placement of implants containing allogeneic aortic endothelial cells (Vascugel) reduces thrombosis, inflammation, stenosis and increases lumen diameter in porcine models of arteriovenous fistulae (AVF) and arteriovenous grafts (AVG). We conducted a phase I/II clinical study to investigate the safety of Vascugel placement around the surgical anastomotic sites of newly constructed dialysis accesses. Methods From July 2006 to August 2006, eight patients (4 AVG, 4 AVF) were treated with two Vascugel sponges at the venous anastomosis in the open–label phase I trial. From January 2007 to August 2007 57 patients (30 AVG and 27 AVF) were randomized in a 2:1 fashion to receive either Vascugel or control matrices (placebo) at surgery. The phase II AVG patients had sponges placed at both the venous and arterial anastomoses. All patients were followed for 24 weeks. The primary objective of the study was to demonstrate the safety (incidence of infection, intervention, and thrombosis) of Vascugel compared with placebo within 30 days post-surgery. Secondary endpoints included assessments of patency, lumen diameter, and immunologic sensitization to human leukocyte antigens (HLA) determined by measurement of panel reactive antibodies (PRA). Results There was no difference in early complication rates between the Vascugel and placebo groups at 4 weeks (10.9% vs 21.1%, respectively). There were no statistically significant differences in primary or assisted primary patency between the intent to treat groups at 24 weeks. Vascugel treated AVG had a primary patency rate of 38% and an assisted primary patency rate of 72% (vs 23% and 58%, respectively, for placebo). Vascugel treated AVF had a primary patency rate of 60% at 24 weeks and an assisted primary patency rate of 96% (vs 62% and 88%, respectively, for placebo). A greater than 30% increase in PRA was detected in 9 of the 46 (19.5%) Vascugel treated patients and one of the 19 (5.2%) placebo patients ( P = .26) and was not associated with any evidence of local or systemic complications. Conclusions Targeted local therapy with perivascular, allogeneic endothelial cells is a safe and novel therapeutic approach that may be ideally suited to control the response to injury at surgical anastomoses. Larger randomized trials are needed to determine if Vascugel can prolong AVG or AVF patency.
The incidence of wartime vascular injury has increased and is a leading cause of mortality and morbidity. While ligation remains an option, current resuscitation and damage control techniques have ...resulted in vascular repair being pursued in more than half of wartime injuries. Options for vascular reconstruction are currently limited to autologous vein or synthetic conduits, choices which have not changed in decades, both of which have problems. Autologous vein is preferable but requires time to harvest and may not be available. Synthetic grafts are poorly resistant to infection and associated with thrombotic complications. Recognizing this capability gap, the US Combat Casualty Care Research Program has partnered with academia and industry to support the development and clinical introduction of a bioengineered human acellular vessel. This human acellular vessel has the potential to be an off-the-shelf conduit that is resistant to infection and incorporates well into native tissues. This report reviews the rationale of this military-civilian partnership in medical innovation and provides an update on the clinical use and ongoing study of this new vascular technology. LEVEL OF EVIDENCE: Therapeutic, level III.
Our previous investigations showed that involuntary treadmill exercise is neuroprotective in a light-induced retinal degeneration mouse model, and it may act through activation of tropomyosin-related ...kinase B (TrkB) receptors. This study investigated whether voluntary running wheel exercise can be neuroprotective in an inheritable model of the retinal degenerative disease retinitis pigmentosa (RP), rd10 mice.
Breeding pairs of rd10 and C57BL/6J mice were given free-spinning (active) or locked (inactive) running wheels. Pups were weaned into separate cages with their parents' respective wheel types, and visual function was tested with ERG and a virtual optokinetic system at 4, 5, and 6 weeks of age. Offspring were killed at 6 weeks of age and retinal cross-sections were prepared for photoreceptor nuclei counting. Additionally, separate cohorts of active and inactive rd10 pups were injected daily for 14 days after eye opening with a selective TrkB receptor antagonist (ANA-12) or vehicle solution and assessed as described above.
Mice in the rd10 active group exhibited significant preservation of visual acuity, cone nuclei, and total photoreceptor nuclei number. Injection with ANA-12 precluded the preservation of visual acuity and photoreceptor nuclei number in rd10 mice.
Voluntary running partially protected against the retinal degeneration and vision loss that otherwise occurs in the rd10 mouse model of RP. This protection was prevented by injection of ANA-12, suggesting that TrkB activation mediates exercise's preservation of the retina. Exercise may serve as an effective, clinically translational intervention against retinal degeneration.
The incidence of wartime vascular injury has increased and is a leading cause of mortality and mobidity. While ligation remains an option, current resuscitation and damage control techniques have ...resulted in vascular repair being pursued in more than half of wartime injuries. Options for vascular reconstruction are currently limited to autologous vein or synthetic conduits, choices which have not changed in decades, both of which have problems. Autologous vein is preferable but requires time to harvest and may not be available. Synthetic grafts are poorly resisent to infection and associated with thrombotic complications.Recognizing this capability gap, the U.S. Combat Casualty Care Research Program has partnered with academia and industry to support the development, and clinical introduction of a bioengineered human acellular vessel (HAV). This HAV has the potential to be an off-the-shelf conduit that is resistant to infection and incorporates well into native tissues. This report reviews the rationale of this military-civilian partnership in medical innovation and provides an update on the clinical use and ongoing study of this new vascular technology. LEVEL OF EVIDENCE: III; Therapeutic.
A multidisciplinary panel consisting of experts chosen by the 2 chairs of the group representing experts in anesthesiology, blood banking, hematology, critical care medicine, and various surgical ...disciplines (trauma, cardiac, pediatric, neurologic, obstetrics, and vascular) convened in January 2008 to discuss hemostasis and management of the bleeding patient across different clinical settings, with a focus on perioperative considerations. Although there are many ways to define hemostasis, one clinical definition would be control of bleeding without the occurrence of pathologic thrombotic events (i.e., when balance among procoagulant, anticoagulant, fibrinolytic, and antifibrinolytic activities is achieved). There are common hemostatic challenges that include lack of scientific evidence and standardized guidelines for the use of therapeutic drugs, need for reliable and rapid laboratory tools for measuring hemostasis, and individual variability. Clinically meaningful and accurate real-time laboratory data reflecting a patient's hemostatic status are needed to guide treatment decisions. Current available routine laboratory tests of hemostasis (e.g., platelet count, prothrombin time/international normalized ratio, and activated partial thromboplastin time) do not reflect the complexity of in vivo hemostasis and can mislead the clinician. Although point-of-care coagulation monitoring tests including measures of thromboelastography/elastometry provide insight into overall hemostatic status, they are time-consuming to perform, complex to interpret, and require trained personnel. There is a particular need to develop laboratory tests that can measure the effects of anticoagulant and antiplatelet agents for individual patients, predict bleeding complications, and guide therapy when and if treatment with blood products or pharmacologic drugs is required. Formation of an organization comprised of specialists who treat bleeding patients will foster multidisciplinary collaborations and promote discussions of the current state of hemostasis treatment and future priorities for hemostasis research. Controlled trials with clinically meaningful end points and suitable study populations, as well as observational studies, investigator-initiated studies, and large registry and database studies are essential to answer questions in hemostasis. Because of the complexities of maintaining hemostatic balance, advances in hemostasis research and continuing communication across specialties are required to improve patient care and outcomes.
Objective The purpose of this Phase I open label nonrandomized trial was to assess the safety and efficacy of autologous bone marrow mononuclear cell (ABMNC) therapy in promoting amputation-free ...survival (AFS) in patients with critical limb ischemia (CLI). Methods Between September 2005 and March 2009, 29 patients (30 limbs), with a median age of 66 years (range, 23-84 years; 14 male, 15 female) with CLI were enrolled. Twenty-one limbs presented with rest pain (RP), six with RP and ulceration, and three with ulcer only. All patients were not candidates for surgical bypass due to absence of a patent artery below the knee and/or endovascular approaches to improving perfusion was not possible as determined by an independent vascular surgeon. Patients were treated with an average dose of 1.7 ± 0.7 × 109 ABMNC injected intramuscularly in the index limb distal to the anterior tibial tuberosity. The primary safety end point was accumulation of serious adverse events, and the primary efficacy end point was AFS at 1 year. Secondary end points at 12 weeks posttreatment were changes in first toe pressure (FTP), toe-brachial index (TBI), ankle-brachial index (ABI), and transcutaneous oxygen measurements (TcPO2 ). Perfusion of the index limb was measured with positron emission tomography-computed tomography (PET-CT) with intra-arterial infusion of H2 O15 . RP, using a 10-cm visual analogue scale, quality of life using the VascuQuol questionnaire, and ulcer healing were assessed at each follow-up interval. Subpopulations of endothelial progenitor cells were quantified prior to ABMNC administration using immunocytochemistry and fluorescent-activated cell sorting. Results There were two serious adverse events; however, there were no procedure-related deaths. Amputation-free survival at 1 year was 86.3%. There was a significant increase in FTP (10.2 ± 6.2 mm Hg; P = .02) and TBI (0.10 ± 0.05; P = .02) and a trend in improvement in ABI (0.08 ± 0.04; P = .73). Perfusion index by PET-CT H2 O15 increased by 19.3 ± 3.1, and RP decreased significantly by 2.2 ± 0.6 cm ( P = .02). The VascuQol questionnaire demonstrated significant improvement in quality of life, and three of nine ulcers (33%) healed completely. KDR+ but not CD34+ or CD133+ subpopulations of ABMNC were associated with improvement in limb perfusion. Conclusion This Phase I study has demonstrated safety, and the AFS rates suggest efficacy of ABMNC in promoting limb salvage in “no option” CLI. Based on these results, we plan to test the concept that ABMNCs improve AFS at 1 year in a Phase III randomized, double-blinded, multicenter trial.
Synthetic expanded polytetrafluorethylene (ePTFE) grafts are routinely used for vascular repair and reconstruction but prone to sustained bacterial infections. Investigational bioengineered human ...acellular vessels (HAVs) have shown clinical success and may confer lower susceptibility to infection. Here we directly compared the susceptibility of ePTFE grafts and HAV to bacterial contamination in a preclinical model of infection.
Sections (1 cm2) of ePTFE (n = 42) or HAV (n = 42) were inserted within bilateral subcutaneous pockets on the dorsum of rats and inoculated with Staphylococcus aureus (107 CFU/0.25 mL) or Escherichia coli (108 CFU/0.25 mL) before wound closure. Two weeks later, the implant sites were scored for abscess formation and explanted materials were halved for quantification of microbial recovery and histological analyses.
The ePTFE implants had significantly higher abscess formation scores for both S. aureus and E. coli inoculations compared to that of HAV. In addition, significantly more bacteria were recovered from explanted ePTFE compared to HAV. Gram staining of explanted tissue sections revealed interstitial bacterial contamination within ePTFE, whereas no bacteria were identified in HAV tissue sections. Numerous CD45+ leukocytes, predominantly neutrophils, were found surrounding the ePTFE implants but minimal intact neutrophils were observed within the ePTFE matrix. The host cells surrounding and infiltrating the HAV explants were primarily nonleukocytes (CD45−).
In an established animal model of infection, HAV was significantly less susceptible to bacterial colonization and abscess formation than ePTFE. The preclinical findings presented in this manuscript, combined with previously published clinical observations, suggest that bioengineered HAV may exhibit low rates of infection.
Abstract Objective This study evaluated whether the use of a staged Hemodialysis Reliable Outflow (HeRO; Merit Medical, South Jordan, Utah) implantation strategy incurs increased early infection risk ...compared with conventional primary HeRO implantation. Methods A retrospective review was performed of 192 hemodialysis patients who underwent HeRO graft implantation: 105 patients underwent primary HeRO implantation in the operating room, and 87 underwent a staged implantation where a previously inserted tunneled central venous catheter was used for guidewire access for the venous outflow component. Within the staged implantation group, 32 were performed via an existing tunneled hemodialysis catheter (incidentally staged), and 55 were performed via a tunneled catheter inserted across a central venous occlusion in an interventional radiology suite specifically for HeRO implantation (intentionally staged). Early infection was defined as episodes of bacteremia or HeRO infection requiring resection ≤30 days of HeRO implantation. Results For staged HeRO implantations, the median interval between tunneled catheter insertion and conversion to a HeRO graft was 42 days. The overall HeRO-related infection rate ≤30 days of implantation was 8.6% for primary HeRO implantation and 2.3% for staged implantations ( P = .12). The rates of early bacteremia and HeRO resection requiring surgical resection were not significantly different between groups ( P = .19 and P = .065, respectively), nor were age, gender, laterality, anastomosis to an existing arteriovenous access, human immunodeficiency virus status, diabetes, steroids, chemotherapy, body mass index, or graft location. None of the patient variables, techniques, or graft-related variables correlated significantly with the early infection rate. Conclusions The staged HeRO implantation strategy did not result in an increased early infection risk compared with conventional primary implantation and is thus a reasonable strategy for HeRO insertion in hemodialysis patients with complex central venous disease.
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