Journal-March2008 Transfusion
The Journal of AABB
March 2008 - Vol. 48 Issue 3 Page 405-571
The Journal of AABB
March 2008 - Vol. 48 Issue 3 Page 405-571
You can download it for free, please click here .
Saturday, February 23, 2008
Wednesday, February 20, 2008
Stroke
Also known as a cerebrovascular accident (CVA), a stroke is a life-threatening event in which part of the brain is deprived of adequate oxygen. Strokes are extremely dangerous, accounting for more than 160,000 deaths each year in the United States, according to the Centers for Disease Control and Prevention (CDC). Stroke is the third leading cause of death in the United States, behind heart disease and cancer. It is also a leading cause of adult disability and institutionalization.
There are two kinds of strokes. An ischemic stroke occurs when the blood supply to the brain is interrupted, usually by a blood clot. The second kind of stroke is a hemorrhagic stroke, which occurs when there is bleeding in or around the brain. Some people may also experience a “mini-stroke” (also called a transient ischemic attack), where symptoms last for a short period of time. All strokes are considered medical emergencies.
Symptoms of a stroke may include numbness or weakness, confusion, dizziness, trouble speaking or understanding others and paralysis. After a stroke begins, it is imperative that people seek treatment as soon as possible to re-establish the flow of oxygen-rich blood to brain cells before permanent tissue damage or death occurs. Imaging tests may also be performed to confirm that a stroke has occurred, identify any potential causes and determine the extent of brain damage (if any).
People who survive a stroke should begin stroke rehabilitation as soon as possible to regain as many lost functions (e.g., lack of coordination, muscle strength) as possible.There are several risk factors associated with strokes. They include age, high blood pressure, heart disease, smoking and obesity. In general, prevention methods for stroke are aimed at eliminating or treating the risk factors. This can usually be accomplished by making certain lifestyle changes, such as eating a heart-healthy diet and taking medications. A physician might also recommend surgery for some patients.
A good linke in this regard:
Monday, February 18, 2008
Stroke
StrokeWhat causes a stroke?
Stroke is a disease that affects the blood vessels that supply blood to the brain.
A stroke occurs when a blood vessel that brings oxygen and nutrients to the brain either bursts (hemorrhagic stroke) or is clogged by a blood clot or some other mass (ischemic stroke). When a rupture or blockage occurs, parts of the brain don't get the blood and oxygen they need. Without oxygen, nerve cells in the affected area of the brain can't work properly, and die within minutes. And when nerve cells can't work, the part of the body they control can't work either. The devastating effects of a severe stroke are often permanent because dead brain cells aren't replaced.
There are two main types of stroke. One (ischemic stroke) is caused by blockage of a blood vessel; the other (hemorrhagic stroke) is caused by bleeding. Bleeding strokes have a much higher death rate than strokes caused by clots.
What is ischemic stroke?
Ischemic stroke is the most common type. It accounts for about 87 percent of all strokes. It occurs when a blood clot (thrombus) forms and blocks blood flow in an artery bringing blood to part of the brain. Blood clots usually form in arteries damaged by fatty buildups, called atherosclerosis.
When the blood clot forms within an artery of the brain, it's called a thrombotic stroke. These often occur at night or first thing in the morning. Another distinguishing feature is that very often they're preceded by a transient ischemic attack. This is also called a TIA or "warning stroke." TIAs have the same symptoms of stroke but only last a few minutes; stroke symptoms last much longer. If someones experiences a TIA, they should urgent medical care immediately.
What is a cerebral embolism?
A wandering clot (an embolus) or some other particle that forms away from the brain, usually in the heart, may also cause an ischemic stroke. This is called cerebral embolism. The clot is carried by the bloodstream until it lodges in an artery leading to or in the brain, blocking the flow of blood.
The most common cause of these emboli is blood clots that form during atrial fibrillation (AF). AF is a disorder found in about 2.2 million Americans. It's responsible for 15–20 percent of all strokes. In AF, the heart's two small upper chambers (the atria) quiver like a bowl of jello instead of beating strongly and effectively. Some blood isn't pumped completely out of them when the heart beats, so it pools and clots can form. When a blood clot enters the circulation and lodges in a narrowed artery of the brain, a stroke occurs. This is called a cardioembolic stroke, or a stroke that occurs because of a heart problem.
What is hemorrhagic stroke?
A subarachnoid hemorrhage occurs when a blood vessel on the brain's surface ruptures and bleeds into the space between the brain and the skull (but not into the brain itself).
A cerebral hemorrhage occurs when a defective artery in the brain bursts, flooding the surrounding tissue with blood.
Hemorrhage (or bleeding) from an artery in the brain can be caused by a head injury or a burst aneurysm. Aneurysms are blood-filled pouches that balloon out from weak spots in the artery wall. They're often caused or made worse by high blood pressure. Aneurysms aren't always dangerous, but if one bursts in the brain, they cause a hemorrhagic stroke.
When a cerebral or subarachnoid hemorrhage occurs, the loss of a constant blood supply means some brain cells no longer can work. Accumulated blood from the burst artery also may put pressure on surrounding brain tissue and interfere with how the brain works. Severe or mild symptoms can result, depending on the amount of pressure.
The amount of bleeding determines the severity of cerebral hemorrhages. In many cases, people with cerebral hemorrhages die of increased pressure on their brains. But those who live tend to recover much more than people who've had strokes caused by a clot. That's because when a blood vessel is blocked, part of the brain dies — and the brain doesn't regenerate itself; in other words, brain cells can't be replaced. But when a blood vessel in the brain bursts, pressure from the blood compresses part of the brain. If the person survives, gradually the pressure goes away. Then the brain may regain some of its former function.
Stroke is a disease that affects the blood vessels that supply blood to the brain.
A stroke occurs when a blood vessel that brings oxygen and nutrients to the brain either bursts (hemorrhagic stroke) or is clogged by a blood clot or some other mass (ischemic stroke). When a rupture or blockage occurs, parts of the brain don't get the blood and oxygen they need. Without oxygen, nerve cells in the affected area of the brain can't work properly, and die within minutes. And when nerve cells can't work, the part of the body they control can't work either. The devastating effects of a severe stroke are often permanent because dead brain cells aren't replaced.
There are two main types of stroke. One (ischemic stroke) is caused by blockage of a blood vessel; the other (hemorrhagic stroke) is caused by bleeding. Bleeding strokes have a much higher death rate than strokes caused by clots.
What is ischemic stroke?
Ischemic stroke is the most common type. It accounts for about 87 percent of all strokes. It occurs when a blood clot (thrombus) forms and blocks blood flow in an artery bringing blood to part of the brain. Blood clots usually form in arteries damaged by fatty buildups, called atherosclerosis.
When the blood clot forms within an artery of the brain, it's called a thrombotic stroke. These often occur at night or first thing in the morning. Another distinguishing feature is that very often they're preceded by a transient ischemic attack. This is also called a TIA or "warning stroke." TIAs have the same symptoms of stroke but only last a few minutes; stroke symptoms last much longer. If someones experiences a TIA, they should urgent medical care immediately.
What is a cerebral embolism?
A wandering clot (an embolus) or some other particle that forms away from the brain, usually in the heart, may also cause an ischemic stroke. This is called cerebral embolism. The clot is carried by the bloodstream until it lodges in an artery leading to or in the brain, blocking the flow of blood.
The most common cause of these emboli is blood clots that form during atrial fibrillation (AF). AF is a disorder found in about 2.2 million Americans. It's responsible for 15–20 percent of all strokes. In AF, the heart's two small upper chambers (the atria) quiver like a bowl of jello instead of beating strongly and effectively. Some blood isn't pumped completely out of them when the heart beats, so it pools and clots can form. When a blood clot enters the circulation and lodges in a narrowed artery of the brain, a stroke occurs. This is called a cardioembolic stroke, or a stroke that occurs because of a heart problem.
What is hemorrhagic stroke?
A subarachnoid hemorrhage occurs when a blood vessel on the brain's surface ruptures and bleeds into the space between the brain and the skull (but not into the brain itself).
A cerebral hemorrhage occurs when a defective artery in the brain bursts, flooding the surrounding tissue with blood.
Hemorrhage (or bleeding) from an artery in the brain can be caused by a head injury or a burst aneurysm. Aneurysms are blood-filled pouches that balloon out from weak spots in the artery wall. They're often caused or made worse by high blood pressure. Aneurysms aren't always dangerous, but if one bursts in the brain, they cause a hemorrhagic stroke.
When a cerebral or subarachnoid hemorrhage occurs, the loss of a constant blood supply means some brain cells no longer can work. Accumulated blood from the burst artery also may put pressure on surrounding brain tissue and interfere with how the brain works. Severe or mild symptoms can result, depending on the amount of pressure.
The amount of bleeding determines the severity of cerebral hemorrhages. In many cases, people with cerebral hemorrhages die of increased pressure on their brains. But those who live tend to recover much more than people who've had strokes caused by a clot. That's because when a blood vessel is blocked, part of the brain dies — and the brain doesn't regenerate itself; in other words, brain cells can't be replaced. But when a blood vessel in the brain bursts, pressure from the blood compresses part of the brain. If the person survives, gradually the pressure goes away. Then the brain may regain some of its former function.
Tuesday, February 12, 2008
Benefits of Mechanical Thrombectomy Catheter Devices.
Benefits of Mechanical Thrombectomy Catheter Devices.
The benefits of mechanical thrombectomy techniques have mainly been demonstrated in short-term studies. In one such trial, the benefit of using thrombectomy devices alongside any adjuvant therapy was examined.16 With the exception of aspirin and thienopyridine, which are used to prevent stroke, combined usage of adjuvant therapy and thrombectomy provides no long-term improvements in left ventricular systolic function. This indicates that thrombectomy alone is sufficient to remove thrombolic occlusion in the coronary artery. The main improvement offered by mechanical thrombectomy over standard angioplasty is the reduction in risk of distal embolism. The balloon catheter has to pass directly through the thrombus in order to be inflated, which frequently leads to the breaking off of small fragments from the thrombus that can cause a blockage elsewhere. In a study examining the microcirculation between mechanical thrombectomy and angioplasty patients, the thrombectomy method resulted in higher flow rates due to the reduced risk of distal embolism.12 Occurrence of macroembolisation was also negligible with thrombectomy tested on both fresh and hardened thrombi.17 In addition, the procedure time of both thrombectomy and the standard balloon technique is extremely comparable. Hence, the thrombectomy technique fits into the tight time constraints in cardiac blockage. Thrombectomy also has advantages over thrombolytics. Administration of thrombolytic substances is time-consuming: the drugs take from one hour to 90 minutes to reduce the thrombus. This time delay exposes the patient to a 1% haemorrhagic stroke rate, which is an unacceptable risk.18
The benefits of mechanical thrombectomy techniques have mainly been demonstrated in short-term studies. In one such trial, the benefit of using thrombectomy devices alongside any adjuvant therapy was examined.16 With the exception of aspirin and thienopyridine, which are used to prevent stroke, combined usage of adjuvant therapy and thrombectomy provides no long-term improvements in left ventricular systolic function. This indicates that thrombectomy alone is sufficient to remove thrombolic occlusion in the coronary artery. The main improvement offered by mechanical thrombectomy over standard angioplasty is the reduction in risk of distal embolism. The balloon catheter has to pass directly through the thrombus in order to be inflated, which frequently leads to the breaking off of small fragments from the thrombus that can cause a blockage elsewhere. In a study examining the microcirculation between mechanical thrombectomy and angioplasty patients, the thrombectomy method resulted in higher flow rates due to the reduced risk of distal embolism.12 Occurrence of macroembolisation was also negligible with thrombectomy tested on both fresh and hardened thrombi.17 In addition, the procedure time of both thrombectomy and the standard balloon technique is extremely comparable. Hence, the thrombectomy technique fits into the tight time constraints in cardiac blockage. Thrombectomy also has advantages over thrombolytics. Administration of thrombolytic substances is time-consuming: the drugs take from one hour to 90 minutes to reduce the thrombus. This time delay exposes the patient to a 1% haemorrhagic stroke rate, which is an unacceptable risk.18
Thursday, February 7, 2008
Mechanical Thrombectomy Devices Supplement Thrombolysis
Managing thrombosis comprises a critical part of vascular patient care, because the development of thromboses poses considerable risk throughout the body, frequently precipitating stroke, myocardial infarction, compromised circulation and ischemia. Sites at particular risk for thromboses formation include dialysis access grafts, ischemic lower extremities with native artery or bypass occlusions, iliofemoral deep veins, cerebral arteries and coronary bypass grafts, which are prone restenose and to seed distal thromboemboli.
Percutaneous revascularization of thrombus-containing lesions has an increased incidence of adverse events such as abrupt vessel closure, periprocedural myocardial infarction and death. Various pharmacologic agents and mechanical approaches have demonstrated modest angiographic success with significant periprocedural complications.
The pharmacological treatment of thrombosis has advanced in recent years with the growing familiarity with tissue plasminogen activators (rt-PAs), the market withdrawal and return of urokinase, and the advent of newer agents such as tenecteplase and plasmin-based products. Despite these developments, many patients remain refractory to pharmacotherapy. Moreover, the collective costs of such therapy are daunting among those in whom thrombosis can be treated in-hospital by large doses of lytic agents.
In those patients non-responsive to pharmacotherapy, the application of mechanical trombectomy devices (MTDs) is expanding to encompass a greater range of thrombotic sites. These devices fall into two broad categories, those that fragment the thrombus, with or without clot removal and those that contact the vessel wall.
The advantages of MTDs can include faster reperfusion of ischemic limbs, potentially shorter hospital stays than those required for lytic drug administration alone, and lower rates of rethrombosis. MTD therapy also may provide comparative advantages of safety by leading to fewer bleeding complications, because they can reduce lytic drug doses, or eliminate them altogether. This theoretical advantage, however, must be balanced against device risks such as distal embolization, hemolysis, and vessel wall damage, the likelihood of which varies with each specific device and application.
Mechanical thrombolytic devices have become the mainstay of percutaneous treatment of clotted dialysis grafts. Properly used, they are faster, safer and equally or more effective than chemical lysis. This was one of the main findings presented at the recent conference of the Cardiovascular and Interventional Radiological Society of Europe (CIRSE 2003).
Surgical literature indicates that removing wall-adherent material (clot and pseudointima) is not only desirable but also essential for improved patency of these grafts. Currently, only two wall-contact devices are approved by the FDA for de-clotting synthetic dialysis grafts: the Arrow-Trerotola percutaneous thrombolytic device from Arrow International, Reading, Penna. and the Akonya Eliminator from IDev Technologies, Houston.
In a broader category, the AngioJet (Possis Medical, Inc., Minneapolis) is the only thrombectomy system currently approved for peripheral arterial applications; although many other MTDs have been used off-label for this purpose. The AngioJet is a dual lumen catheter designed to rapidly remove blood clots with minimal vascular trauma. In April 2000, March 1999 and December 1996, Possis received FDA clearances to commence United States marketing of the AngioJet System, for removal of blood clots in leg arteries, native coronary arteries and coronary bypass grafts and access grafts used by patients on kidney dialysis, respectively. The AngioJet System is typically used in conjunction with other medical devices, such as angioplasty balloons and stents (both bare metal and drug eluting), and drugs, such as thrombolytics and platelet inhibitors. Possis also markets the XMI, XVG, Xpeedior and AVX catheters. Each of these catheters features the company's proprietary Cross-Stream Technology.
When compared with urokinase in the randomized VeGAS 2 Trial, AngioJet therapy yields greater angiographic success with a lower incidence of 30-day major adverse events.
The Trellis, manufactured by Bacchus Vascular, Inc., Santa Clara, Calif., is a novel drug infusion device designed for isolated thrombolysis. A thrombus is isolated between two occlusion balloons while the thrombolytic is mechanically dispersed with an oscillating wire and then aspirated. Theoretically, isolated thrombolysis enables single-setting thrombolysis by delivering a high concentration of thrombolytic agent while preventing systemic dispersion. Adjunctive procedures may be performed in the same single setting. Data from a voluntary company registry for isolated thrombolysis have indicated lower hospital costs due to reduced ICU stay and lytic dosing, and no reported bleeding complications. Bacchus reports that a future registry is planned. The Trellis is approved for use in the peripheral vasculature.
Percutaneous revascularization of thrombus-containing lesions has an increased incidence of adverse events such as abrupt vessel closure, periprocedural myocardial infarction and death. Various pharmacologic agents and mechanical approaches have demonstrated modest angiographic success with significant periprocedural complications.
The pharmacological treatment of thrombosis has advanced in recent years with the growing familiarity with tissue plasminogen activators (rt-PAs), the market withdrawal and return of urokinase, and the advent of newer agents such as tenecteplase and plasmin-based products. Despite these developments, many patients remain refractory to pharmacotherapy. Moreover, the collective costs of such therapy are daunting among those in whom thrombosis can be treated in-hospital by large doses of lytic agents.
In those patients non-responsive to pharmacotherapy, the application of mechanical trombectomy devices (MTDs) is expanding to encompass a greater range of thrombotic sites. These devices fall into two broad categories, those that fragment the thrombus, with or without clot removal and those that contact the vessel wall.
The advantages of MTDs can include faster reperfusion of ischemic limbs, potentially shorter hospital stays than those required for lytic drug administration alone, and lower rates of rethrombosis. MTD therapy also may provide comparative advantages of safety by leading to fewer bleeding complications, because they can reduce lytic drug doses, or eliminate them altogether. This theoretical advantage, however, must be balanced against device risks such as distal embolization, hemolysis, and vessel wall damage, the likelihood of which varies with each specific device and application.
Mechanical thrombolytic devices have become the mainstay of percutaneous treatment of clotted dialysis grafts. Properly used, they are faster, safer and equally or more effective than chemical lysis. This was one of the main findings presented at the recent conference of the Cardiovascular and Interventional Radiological Society of Europe (CIRSE 2003).
Surgical literature indicates that removing wall-adherent material (clot and pseudointima) is not only desirable but also essential for improved patency of these grafts. Currently, only two wall-contact devices are approved by the FDA for de-clotting synthetic dialysis grafts: the Arrow-Trerotola percutaneous thrombolytic device from Arrow International, Reading, Penna. and the Akonya Eliminator from IDev Technologies, Houston.
In a broader category, the AngioJet (Possis Medical, Inc., Minneapolis) is the only thrombectomy system currently approved for peripheral arterial applications; although many other MTDs have been used off-label for this purpose. The AngioJet is a dual lumen catheter designed to rapidly remove blood clots with minimal vascular trauma. In April 2000, March 1999 and December 1996, Possis received FDA clearances to commence United States marketing of the AngioJet System, for removal of blood clots in leg arteries, native coronary arteries and coronary bypass grafts and access grafts used by patients on kidney dialysis, respectively. The AngioJet System is typically used in conjunction with other medical devices, such as angioplasty balloons and stents (both bare metal and drug eluting), and drugs, such as thrombolytics and platelet inhibitors. Possis also markets the XMI, XVG, Xpeedior and AVX catheters. Each of these catheters features the company's proprietary Cross-Stream Technology.
When compared with urokinase in the randomized VeGAS 2 Trial, AngioJet therapy yields greater angiographic success with a lower incidence of 30-day major adverse events.
The Trellis, manufactured by Bacchus Vascular, Inc., Santa Clara, Calif., is a novel drug infusion device designed for isolated thrombolysis. A thrombus is isolated between two occlusion balloons while the thrombolytic is mechanically dispersed with an oscillating wire and then aspirated. Theoretically, isolated thrombolysis enables single-setting thrombolysis by delivering a high concentration of thrombolytic agent while preventing systemic dispersion. Adjunctive procedures may be performed in the same single setting. Data from a voluntary company registry for isolated thrombolysis have indicated lower hospital costs due to reduced ICU stay and lytic dosing, and no reported bleeding complications. Bacchus reports that a future registry is planned. The Trellis is approved for use in the peripheral vasculature.
Wednesday, February 6, 2008
Project
16. An Investigation into clot removal times concerning artificial and real blood clots inserted in a straight plastic tube. Supervisor: GP DescriptionThe aim of this project is to investigate the times (together with pressures involved and volumes of fluid extracted) taken to removal artificial blood clots using the ‘GP’ MTD in straight plastic tubes compared to the same using porcine blood clots in porcine arteries. Different lengths of clot will be used.
GP’ MTD=’GP’ Mechanical Thrombectomy Device. Recently patented.
To be honest, do you understand any thing at all?
That is what I have to do as my final project. The supervisor says ,she is going to invent something new, who knows! May be she can. Let’s pray for her.
Saturday, February 2, 2008
Who is Thomas Chang ?
Thomas Chang, O.C. (born 1933) is a Canadian physician and scientist who invented the world’s first artificial cell in 1957.
Born in Shantou, China, he is the Director, Artificial Cells & Organs Research Centre and Professor of Physiology, Medicine & Biomedical Engineering in the Faculty of Medicine at McGill University.
In 1991, he was made an Officer of the Order of Canada.
Thomas Chang, Professor of Physiology
Like many driven young men, Thomas Chang would bring his work home with him. The difference with Chang was his "work" was that the near-impossible task of creating the world's first artificial blood cell. And as an undergraduate student in 1956, his "home" was his residence room in McGill's Douglas Hall.
Remarkably, Chang was successful. Working with improvised materials like perfume atomizers, Chang managed to create a permeable plastic sack that would effectively carry haemoglobin almost as effectively as a natural blood cell. In 1989, the New Scientist called Chang's student research project an "elegantly simple and intellectually ambitious" idea that "has grown into a dynamic field of biomedical research and development."
Chang's remarkable career continued as Director of the Artificial Cells and Organs Research Centre at McGill. In the late sixties he discovered enzymes carried by artificial cells could correct some metabolic disorders and also developed charcoal-filled cells to treat drug poisoning, a now widely used technique. His work on finding a safe blood substitute brought him to prominence in the 1980s and 1990s, earning him an Order of Canada.
At one point considered for a Nobel Prize, Chang has not lost focus on his primary motivation: "To me as a scientist, what is most important is what is most useful to the patient, not what is good for your reputation or what pays the most money. The sick patient should be the most important stimulus for our work."
For more please have look on the related website Univeristy of McGill .
Born in Shantou, China, he is the Director, Artificial Cells & Organs Research Centre and Professor of Physiology, Medicine & Biomedical Engineering in the Faculty of Medicine at McGill University.
In 1991, he was made an Officer of the Order of Canada.
Thomas Chang, Professor of Physiology
Like many driven young men, Thomas Chang would bring his work home with him. The difference with Chang was his "work" was that the near-impossible task of creating the world's first artificial blood cell. And as an undergraduate student in 1956, his "home" was his residence room in McGill's Douglas Hall.
Remarkably, Chang was successful. Working with improvised materials like perfume atomizers, Chang managed to create a permeable plastic sack that would effectively carry haemoglobin almost as effectively as a natural blood cell. In 1989, the New Scientist called Chang's student research project an "elegantly simple and intellectually ambitious" idea that "has grown into a dynamic field of biomedical research and development."
Chang's remarkable career continued as Director of the Artificial Cells and Organs Research Centre at McGill. In the late sixties he discovered enzymes carried by artificial cells could correct some metabolic disorders and also developed charcoal-filled cells to treat drug poisoning, a now widely used technique. His work on finding a safe blood substitute brought him to prominence in the 1980s and 1990s, earning him an Order of Canada.
At one point considered for a Nobel Prize, Chang has not lost focus on his primary motivation: "To me as a scientist, what is most important is what is most useful to the patient, not what is good for your reputation or what pays the most money. The sick patient should be the most important stimulus for our work."
For more please have look on the related website Univeristy of McGill .
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