Overview of Stroke Anticoagulation
Stroke is a major cause of death and severe, long-term disability around the world. As medical treatments improve, both the occurrence and death rate from strokes are decreasing. The majority of strokes we see today are called ischemic strokes, rather than hemorrhagic strokes, which are less common.
An ischemic stroke can be caused by many different factors, some of which can be changed and some of which can’t. For example, things like a person’s age, gender, and race can’t be changed, but their lifestyle choices and health conditions can often be managed to reduce the risk of a stroke. Some risk factors that can be changed include lack of physical activity, the ratio of waist-to-hip size, alcohol consumption, smoking, poor diet, high blood pressure, high cholesterol, diabetes, certain heart diseases including atrial fibrillation, and other metabolic conditions. Short-term risks can also cause a stroke, such as infections or stress.
Doctors use these risk factors in an important part of trying to prevent strokes. There are tools that doctors use to calculate the risk of a stroke so that they can determine which preventative treatments a patient might need. One well-known tool for predicting stroke risk is the Framingham Stroke Risk Profile. This tool takes into account risk factors that can and cannot be changed. Using this information, doctors can change the risk of stroke by intervening with targeted treatments.
If a patient comes to the hospital with changes in consciousness or sudden changes in physical or mental function, doctors must quickly determine if they are having a stroke. In such situations, the most important step is to figure out when the stroke symptoms first started, as this will help decide what type of treatment to use.
The doctor will perform a physical examination to find out where in the brain the stroke has occurred, eliminate other possible causes of the symptoms, assess the extent of the brain injury, and identify any other health conditions that could affect treatment. This includes a thorough review of the patient’s medical history, which can reveal risk factors for ischemic stroke, recent injuries, blood clotting disorders, use of birth control pills, use of illegal drugs like cocaine, and migraines.
Before starting treatment, the doctor will consider several important factors. First, they will perform a brain scan, typically using a non-contrast CT or MRI, to ensure that there is no bleeding in the brain. Blood glucose and oxygen levels are also measured, as low or high levels can mimic stroke symptoms.
In addition, the doctor will probably order a set of baseline lab tests, which should include a complete blood count (including a count of platelets, a type of blood cell that helps with clotting), serum electrolytes (which help balance the amount of water in your body, the balance of your body’s pH, move nutrients into your cells, etc.), kidney function tests, cardiac panel (which measures the heart’s function and specifies the levels of substances released into the blood), and electrocardiogram (a test that measures the electrical activity of the heartbeat). However, treatment should not be delayed while waiting for these results, except in cases where the doctor suspects that the patient might have a low platelet count or a bleeding disorder and is taking drugs that thin the blood like heparin or warfarin.
When a stroke is suspected, the first step is usually a non-contrast CT scan, a type of imaging test that uses X-rays and a computer to create detailed images of the brain. However, an MRI can sometimes be used, especially if the doctor needs to check for a brain hemorrhage (bleeding in the brain) or if it’s early in the course of a isolated stroke and need to identify the infarct (the area of tissue that dies due to lack of blood flow during a stroke).
During treatment, the doctor will also assess vital signs and pay special attention to breathing, temperature, and blood pressure. High blood pressure might be the body’s way of trying to maintain blood flow to the parts of the brain affected by the stroke. Patients who are not breathing adequately can have an increase in the level of carbon dioxide in their blood, which can worsen the stroke by causing the blood vessels in the brain to expand and the pressure in the skull to rise, so there might be a need for intubation (a tube placed into the windpipe to maintain an open airway). It’s also important to keep the patient’s temperature normal for several days after an acute stroke because fever can worsen the stroke.
The latest guidelines by the American Heart Association/American Stroke Association for managing patients with ischemic stroke include the use of clot-busting drugs, blood thinners, antiplatelet agents (drugs that reduce the ability of platelets to stick together and form clots), cholesterol lowering drugs, drugs to lower blood pressure, and control of blood sugar levels. Previously, blood thinners were used widely in the immediate treatment of ischemic stroke. Recent research has limited their use to certain patient populations only. Now, blood thinners play a major role mainly in trying to prevent initial and recurrent ischemic strokes.
Anatomy and Physiology of Stroke Anticoagulation
An acute ischemic stroke, often abbreviated as AIS, is caused by a sudden halt in blood flow to the brain. This usually happens when a blood clot or other object blocks one of the blood vessels that deliver blood to the brain, resulting in loss of brain function. When the blood flow stops, this creates a shortage of oxygen and “cellular energy” (known medically as adenosine triphosphate or ATP), that our cells need to function. Without enough ATP, the carefully balanced mixture of ions within and outside of our cells is disrupted. This leads to an overload of sodium and calcium ions and water moving into cells, which can cause harmful swelling inside the cells.
What exactly happens during an ischemic stroke and how severe it is can depend on what caused the stroke. For instance, there may be different outcomes if the stroke was caused by a small blood vessel blockage (lacunar), a clot that traveled from the heart (cardioembolic), hardening of the arteries (atherosclerotic), tears in the artery wall (dissections), inflammation of blood vessels (vasculitis), specific genetic disorders, or other causes.
Ischemic strokes can lead to changes in both thinking (cognitive) and movement (motor) abilities. If the loss of blood flow to the brain is severe, it can cause physical changes to different types of brain cells and brain matter, including “knob” diseases (neuronal), blood vessel diseases (vascular endothelial), star-shaped cells (astrocytic cells), and myelin-forming cells (oligodendrocyte), which are essential for communication in the brain. Damage to white matter regions in the brain can result in nerve injury and loss of insulating layer (demyelination) leading to impaired nerve signal conduction. If the stroke is less severe, only certain populations of nerve cells may be damaged, while others remain unharmed.
Understanding what happens in the brain during and after a stroke is important because it helps in finding ways to prevent and treat strokes effectively.
Why do People Need Stroke Anticoagulation
Restoring blood flow quickly is the best way to save brain tissue that’s not getting enough oxygen because of a stroke. Doctors often use a medicine called alteplase to do this. It’s injected into a vein and works by breaking up the blood clot that’s causing the stroke. Alteplase has been proven to work well in many major research studies.
Generally, patients who receive alteplase within 3 to 4.5 hours from when their stroke symptoms started see significant improvements. The decision to use alteplase is based on several specific criteria. For example, recent research suggests that alteplase could benefit patients who have mild strokes that are still causing disability.
The American Heart Association and American Stroke Association (AHA/ASA) guidelines from 2018 do not recommend blood thinners to treat strokes, no matter how severe the blood vessel blockage is. This recommendation is based on studies that found no clear evidence to support urgent blood thinning. But these studies did not include a trial that compared the effectiveness of a type of blood thinner called low molecular weight heparin (LMWH) to aspirin in preventing early stroke symptoms and blood clots in the leg and lung, and in measuring stroke outcomes after 6 months.
Taking LMWH, as opposed to aspirin, soon after a stroke until 10 days later could lower the risk of early stroke symptoms and clots in the leg. However, there’s still a lack of data to support these results, so the AHA/ASA 2018 guidelines do not recommend urgent blood thinners for stroke patients with a significant blockage in the neck’s main artery.
Moreover, anticoagulants like thrombin and factor Xa inhibitors have also been examined for possible use in stroke treatment. These inhibitors could be used alone or alongside alteplase. However, more extensive studies are needed to prove their effectiveness and safety. Lastly, while the potential benefits of anticoagulants are still being debated for stroke treatment, their use is highly recommended for preventing strokes in patients with an irregular heart rhythm condition called atrial fibrillation. These patients have a moderate to high risk of stroke.
When a Person Should Avoid Stroke Anticoagulation
Using blood thinning medication to prevent strokes requires careful consideration of the risks and benefits. Water-soluble blood thinners, like heparin or LMWH (low molecular weight heparin), should be avoided when starting this treatment. This is because they could increase the risk of bleeding in the brain and repeat strokes. Moreover, if someone has suffered from a severe stroke, it might be sensible to wait longer before starting blood thinners.
For people who have a higher risk of bleeding, the dangers of using blood thinners may outweigh the benefits. This means that they should probably avoid these drugs. In particular, blood thinners might not be suitable for those who have very poor kidney or liver function. They are also not suitable for people who have a severe type of bleed in the brain, known as a parenchymal hematoma. However, there are still some unanswered questions in this area of treatment.
Possible Complications of Stroke Anticoagulation
The primary complication linked to ischemic stroke, a condition where blood flow to the brain is blocked, is the progression to hemorrhagic stroke. Hemorrhagic stroke occurs when a blood vessel in your brain leaks or ruptures. This situation can become particularly risky when blood-thinning medications known as anticoagulants are used.
What Else Should I Know About Stroke Anticoagulation?
Anticoagulants are medicines that help prevent blood clots. They can reduce the risk of having a stroke, which often happens because of a clot blocking blood flow in the brain, or other issues caused by clots, by over two-thirds. This is true no matter what your health condition is.
Right now, there are many studies being done to see how safe and effective these medicines are, especially when used with or instead of a common treatment for acute ischemic stroke (AIS) known as tissue plasminogen activator (tPA), which helps dissolve blood clots. We need more information to decide on the best way to use these treatments.
Nonetheless, anticoagulants are very important in preventing a first stroke or a repeat stroke.
