Bantayehu Sileshi

A comprehensive review of topical hemostatic agents: efficacy and recommendations for use.

Since ancient times we have attempted to facilitate hemostasis by application of topical agents. In the last decade, the number of different effective hemostatic agents has increased drastically. In order for the modern surgeon to successfully choose the right agent at the right time, it is essential to understand the mechanism of action, efficacy and possible adverse events as they relate to each agent. In this article we provide a comprehensive review of the most commonly used hemostatic agents, subcategorized as physical agents, absorbable agents, biologic agents, and synthetic agents. We also evaluate novel hemostatic dressings and their application in the current era. Furthermore, wholesale acquisition prices for hospitals in the United States are provided to aid in cost analysis. We conclude with an expert opinion on which agent to use under different scenarios.

The Biocompatibility of Titanium Cardiovascular Devices Seeded With Autologous Blood-Derived Endothelial Progenitor Cells: EPC-Seeded Antithrombotic Ti Implants

Implantable and extracorporeal cardiovascular devices are commonly made from titanium (Ti) (e.g. Ti-coated Nitinol stents and mechanical circulatory assist devices). Endothelializing the blood-contacting Ti surfaces of these devices would provide them with an antithrombogenic coating that mimics the native lining of blood vessels and the heart. We evaluated the viability and adherence of peripheral blood-derived porcine endothelial progenitor cells (EPCs), seeded onto thin Ti layers on glass slides under static conditions and after exposure to fluid shear stresses. EPCs attached and grew to confluence on Ti in serum-free medium, without preadsorption of proteins. After attachment to Ti for 15 min, less than 5% of the cells detached at a shear stress of 100 dyne / cm(2). Confluent monolayers of EPCs on smooth Ti surfaces (Rq of 10 nm), exposed to 15 or 100 dyne/cm(2) for 48 h, aligned and elongated in the direction of flow and produced nitric oxide dependent on the level of shear stress. EPC-coated Ti surfaces had dramatically reduced platelet adhesion when compared to uncoated Ti surfaces. These results indicate that peripheral blood-derived EPCs adhere and function normally on Ti surfaces. Therefore EPCs may be used to seed cardiovascular devices prior to implantation to ameliorate platelet activation and thrombus formation.

The development and potential of acoustic radiation force impulse (ARFI) imaging for carotid artery plaque characterization

Stroke is the third leading cause of death and long-term disability in the USA. Currently, surgical intervention decisions in asymptomatic patients are based upon the degree of carotid artery stenosis. While there is a clear benefit of endarterectomy for patients with severe (> 70%) stenosis, in those with high/moderate (50–69%) stenosis the evidence is less clear. Evidence suggests ischemic stroke is associated less with calcified and fibrous plaques than with those containing softer tissue, especially when accompanied by a thin fibrous cap. A reliable mechanism for the identification of individuals with atherosclerotic plaques which confer the highest risk for stroke is fundamental to the selection of patients for vascular interventions. Acoustic radiation force impulse (ARFI) imaging is a new ultrasonic-based imaging method that characterizes the mechanical properties of tissue by measuring displacement resulting from the application of acoustic radiation force. These displacements provide information about the local stiffness of tissue and can differentiate between soft and hard areas. Because arterial walls, soft tissue, atheromas, and calcifications have a wide range in their stiffness properties, they represent excellent candidates for ARFI imaging. We present information from early phantom experiments and excised human limb studies to in vivo carotid artery scans and provide evidence for the ability of ARFI to provide high-quality images which highlight mechanical differences in tissue stiffness not readily apparent in matched B-mode images. This allows ARFI to identify soft from hard plaques and differentiate characteristics associated with plaque vulnerability or stability.

Pathophysiology of Bleeding and Clotting in the Cardiac Surgery Patient From Vascular Endothelium to Circulatory Assist Device Surface

Clinicians are faced with the challenge of navigating the precarious balance between bleeding and clotting. Bleeding disorders or failure to obtain adequate hemostasis during surgery may lead to severe hemorrhage. However, if thrombotic complications occur (eg, thromboembolic stroke), they may be far more difficult to treat. To achieve a stable equilibrium between bleeding and clotting, the treating physician should have a fundamental understanding of coagulation biology. In this article, we review the physiological role of the vascular endothelium in maintaining an antithrombogenic environment at baseline and a prothrombotic state after injury. Commonly used hemostatic and anticoagulant drugs and their mechanism of action are examined in this context. This is followed by a review of the most common inherited and acquired bleeding and clotting disorders, as well as the mechanism by which they lead to defects in coagulation biology. The approach to a bleeding patient is then discussed, including the interpretation of the most frequently used coagulation tests. Finally, we analyze mechanical assist device therapy as an extreme case of an acquired bleeding and clotting diathesis. The concept of blood coagulation dates back to the 1960s, when Davie, Ratnoff, and Macfarlane published articles in Nature and Science outlining the fundamental principle of a cascade of proenzymes activated through proteolytic cleavage that in turn activate “downstream” enzymes.1,2 Schematically, the coagulation system is divided into the extrinsic and intrinsic pathways (Figure 1 and Movie I in the online-only Data Supplement). The extrinsic pathway is triggered in response to tissue trauma and is initiated with exposure of tissue factor. The role of the intrinsic pathway is less clear in vivo but becomes important when the blood is activated via contact with artificial surfaces, such as a cardiopulmonary bypass circuit or a mechanical circulatory assist device (MCAD).3 Figure 1. Coagulation cascade. The extrinsic …

Surgical aspects and biological considerations of arteriovenous fistula placement.

Since the Fistula First Initiative was formulated in 2003, providers and payers have increasingly emphasized the need to create more arteriovenous fistulae. To maximize the chances of successful fistula maturation, a thorough understanding of the biology and surgical aspects of fistula placement are essential. A functional endothelium in the target vessels is the prerequisite for the adaptive remodeling of the vessel wall, which has to take place after fistula formation. Mechanoreceptors of the endothelium sense the increase in shear stress and, through a variety of activated signaling cascades, induce the necessary changes and vasodilation of the respective vessels. The successful fistula placement starts with a thorough preoperative evaluation, which focuses on protecting the target vessels and avoiding intravenous catheters and devices. Intraoperatively, the risk of endothelial dysfunction and hyperplasia is further minimized through an atraumatic dissection with minimal manipulation of the vein and artery. The surgical technique should also focus on decreasing the vessel compliance mismatch and avoiding an inflammatory response secondary to hematoma formation. Postoperatively, the fistula must be diligently monitored for the complications of thrombosis, postoperative steal syndrome, neuropathy, aneurysm formation, infection, and high‐output cardiac failure. Early recognition of a problem is the key to saving an otherwise doomed fistula. An armamentarium of percutaneous techniques is available to the access surgeon to treat the most common causes of failed access formation. However, in some cases a surgical revision of the access site through patch angioplasty, a jump graft, and graft interposition is necessary to create a fistula which can be successfully used for hemodialysis.

Application Of Energy-based Technologies And Topical Hemostatic Agents In The Management Of Surgical Hemostasis

Achieving intraoperative hemostasis is essential for excellent surgical outcomes. A variety of methods, ranging from mechanical tools and energy-based technologies to topical hemostatic agents, are available to the modern surgeon. Given that bleeding develops from different origins, from small discrete bleeding or venous oozing to arterial hemorrhage, different tools and agents have different efficacy in specific situations. In this article, we review the mechanism by which currently available hemostatic tools and agents stop bleeding and give recommendations for their use during surgery. Furthermore, the costs of the various methods are presented, allowing the provider to choose not only the most potent but also the most cost-effective treatment modality in each situation.

Genomic modeling of atherosclerosis in peripheral arterial disease and its variant phenotype in patients with diabetes.

Microarrays can be used to discover candidate genes associated with peripheral arterial disease (PAD) and develop models that predict patient clinical status. We hypothesize that multiple phenotypes of PAD with distinct patterns of gene expression exist. We histologically characterized and extracted ribonucleic acid from 31 arterial samples collected from the lower extremities of patients undergoing amputation or free fibular grafting. Analysis using the Affymetrix U133A microarray identified 335 genes with twofold or greater differences in expression between normal and diseased arteries (p < .01) and 104 genes with twofold or greater differences between diabetic and nondiabetic atherosclerotic arteries (p < .1). Many genes identified have known roles in inflammatory and lipid uptake pathways. Predictive models were developed that could predict PAD and the associated diabetic phenotype with an accuracy of 71 to 90%. Developing distinct genomic models of PAD will serve as the first step toward understanding the molecular and genetic basis of PAD and subsequent application of novel therapeutics to this condition.