Overview of Anesthesia for Endovascular Therapy for Acute Ischemic Stroke in Adults
Every year, about 795,000 people in the United States have a stroke. That means, roughly, one person gets a stroke every 40 seconds, and sadly, one person dies from a stroke every four minutes. A stroke, which is a sudden interruption in the blood supply to the brain, can be of different types. These include ischemic, hemorrhic, subarachnoid, cerebral thrombosis, and spinal stroke. A majority of strokes, around 80 to 87%, are ischemic, meaning caused by a blocked artery. There are five subtypes of ischemic stroke:
- Large-artery atherosclerosis – hardening of the larger brain arteries
- Cardioembolism – blood clot formed in the heart
- Small-vessel occlusion – blockage of smaller blood vessels in the brain
- Stroke of other determined etiology – stroke caused by less common factors
- Stroke of undetermined etiology – stroke for which cause can’t be identified
There are certain risk factors for stroke that can be divided into those you can change and those you can’t. The ones you can control or treat include high blood pressure, diabetes, high cholesterol, smoking, alcohol and drug use, lack of physical activity, and irregular heartbeat known as atrial fibrillation. The risk factors you can’t change are age, gender, race, and genetics.
Anatomy and Physiology of Anesthesia for Endovascular Therapy for Acute Ischemic Stroke in Adults
The brain gets its supply of blood from two main sources: from the front via the internal carotid arteries, and from the back via the vertebral arteries. These arteries come together at a spot called the ‘circle of Willis’ and this is where other key arteries that supply blood to the brain start. The main arteries are the anterior cerebral artery, middle cerebral artery, anterior choroidal artery, posterior cerebral artery, anterior inferior cerebellar artery, posterior inferior cerebellar artery, and the basilar artery.
Just like there are arteries to take blood to the brain, the flanks of our brain also have a network of veins, called the cerebral venous system, to drain out blood. This system has superficial dural venous sinuses and deep cerebral veins.
There are two main types of stroke. An Acute Ischemic Stroke (AIS) is caused when the flow of blood and oxygen to the brain is blocked, while a hemorrhagic stroke occurs when blood vessels in the brain start to leak or bleed.
An ischemic stroke usually happens when a clot blocks blood vessels making its way to the brain, cutting off the flow of blood. Sometimes, this can also happen if a piece of plaque, a fatty deposit that narrows the arteries, breaks off and blocks a blood vessel to the brain. This can lead to brain cells dying due to lack of blood. In roughly 10 to 15% of all strokes, the blood vessel(s) ruptures and causes blood to flood into the brain. This type of stroke leads to higher death rates. After a stroke, the dead brain tissue is surrounded by brain tissue which is damaged but not fully dead yet – referred to as penumbra. This damaged tissue, potentially recoverable, becomes the focus of stroke treatment.
Why do People Need Anesthesia for Endovascular Therapy for Acute Ischemic Stroke in Adults
Endovascular therapy is a treatment option for acute ischemic stroke, which is a condition where blood flow to the brain is obstructed, often by a clot. This therapy is typically used for patients who arrive at the hospital too late for a commonly used stroke treatment called intravenous recombinant-type tissue plasminogen activator (IV rtPA). Essentially, IV rtPA is a medication given through the veins to break down the clot and restore blood flow to the brain.
However, if a patient cannot receive the IV rtPA therapy due to certain conditions like a recent surgery or a blood clotting disorder (coagulopathy), or if the IV rtPA treatment did not work for them, endovascular therapy can be used instead.
The good news is, patients who get endovascular therapy and standard medical care within 6 to 24 hours after the stroke symptoms start typically have a good chance of recovery. It’s always crucial to get medical attention as soon as possible if you suspect a stroke.
Equipment used for Anesthesia for Endovascular Therapy for Acute Ischemic Stroke in Adults
When doctors use brain imaging techniques, such as non-contrast computed tomography (an X-ray that takes a cross-sectional image of the brain), and diffusion weight magnetic resonance imaging (a type of MRI that measures the diffusion of water in various tissues), they use a variety of equipment, including:
In the case of Cerebral Angiography (a test that uses X-rays and a special dye to see how blood flows in the brain):
- Airway equipment, endotracheal tubes (tubes inserted through the mouth into the airway), and laryngoscopes (used to see the voice box and throat)
- An anesthesia machine, which is used to deliver medications to help you to sleep and not feel pain during the procedure
- Oxygen, to ensure your body has enough oxygen during the procedure
- Anesthesia induction agents like propofol and etomidate, which are used to help you sleep after medications are given to relax your muscles
- Vasoactive medications, such as vasopressors (drugs that tighten blood vessels and increase blood pressure) and anti-hypertensive drugs (medications that help lower blood pressure)
- An ultrasound machine, which uses sound waves to create images of blood vessels, for rapid vascular access or arterial line cannulation (the process of inserting a tube into an artery)
- An arterial blood gas analyzer to measure oxygen and carbon dioxide levels in the blood
- Glucometers, which are used to measure how much sugar is in your blood
For a Mechanical Thrombectomy (a treatment for stroke that removes a blood clot in the brain):
- A stent retriever, a device used to remove the clot
- A Mechanical Embolus Removal in Cerebral Ischemia (MERCI) device, which can restore blood flow by removing blood clots
- A proximal balloon guide catheter, a small tube used to help guide the doctor to the clot
- A large-bore distal access catheter, a larger tube also used to reach the clot
- A cervical guide catheter, used to navigate through the neck arteries to reach the clot in the brain
Standard American Society of Anesthesiology (ASA) monitors include equipment to observe heart and breathing rates, blood pressure, body temperature, and levels of carbon dioxide during the procedure.
Who is needed to perform Anesthesia for Endovascular Therapy for Acute Ischemic Stroke in Adults?
When you need sudden medical care, there is a team of healthcare professionals ready to help you. This includes people who work in the emergency room, specialists who use non-surgical procedures to treat conditions of the nervous system (neurointerventionalists), doctors who specialize in controlling pain and putting patients to sleep for surgeries (anesthesiologists), doctors who specialize in problems with the nervous system (neurologists), surgeons who operate on the brain and nerves (neurosurgeons), doctors who specialize in the critical care of patients with disorders that affect the brain and spinal cord (neurocritical care specialists), nurses, and technicians. This team works together to ensure you receive the best possible care.
Preparing for Anesthesia for Endovascular Therapy for Acute Ischemic Stroke in Adults
Mechanical thrombectomy, which is a medical procedure done in urgent situations, should be planned well beforehand to avoid any hold-ups when it comes to giving anesthesia. This means that special medical rooms used for examining blood vessels in the brain, or for surgeries, need to be set up in advance. Anesthesia is a type of medication that helps reduce pain during medical procedures, and the machine for administering it needs to be checked and made ready.
Also, equipment for maintaining the patient’s airway (breathing passage), devices for monitoring vital signs like heart rate and blood pressure, kits for establishing a vein access point (a way of putting medications directly into the bloodstream), and the needed medications themselves should all be prepared. These steps are important because they help to start and continue the use of anesthesia during the procedure. Preparing all this equipment in advance helps ensure the procedure goes smoothly and safely.
How is Anesthesia for Endovascular Therapy for Acute Ischemic Stroke in Adults performed
There are two types of strokes – hemorrhagic and ischemic. Let’s first simplify the information on these two types of strokes, and then the treatment approaches for them.
A hemorrhagic stroke is when a blood vessel in the brain bursts and spills blood into or around the brain. Hemorrhagic strokes are typically managed by controlling high blood pressure and surgically removing the blood that has accumulated in the brain. However, it’s uncertain how well these approaches improve health outcomes. Research comparing different levels of blood pressure control did not show fewer deaths or improvements in those suffering from hemorrhagic stroke. Nevertheless, early surgery to remove the accumulated blood has been shown to have some benefits.
An acute ischemic stroke (AIS) is caused by a blockage preventing blood from reaching parts of the brain. When this happens, brain cells die quickly. This is why it’s crucial to get treatment fast. For every minute that a large vessel stroke goes untreated, around 1.9 million neurons in the brain are lost. Thus, any delays in anesthesia should be avoided to preserve the salvageable part of the brain, called the penumbra region.
There’s ongoing debate about what kind of anesthesia is best for stroke patients – general anesthesia (you’re completely unconscious) or conscious sedation (you’re relaxed and pain-free, but still awake). Some studies have found general anesthesia to be linked with less disability, while others have found it to have worse health outcomes. Both types of anesthesia have their pros and cons. General anesthesia advantages are stillness, pain control, and airway protection, but it can cause more changes in heart rate and blood pressure and might delay the start of the procedure. Local anesthesia (numbing a small area) offers better control of heart rate and blood pressure and allows for neurological evaluation. But, patient movement, pain, agitation, and loss of airway control can be issues.
Guidelines from the American Heart Association/ American Stroke Association (AHA/ASA) suggest that anesthesia should be chosen based on your health risk factors, the specific circumstances of your stroke, and the procedure being performed. They endorse either general anesthesia or procedural sedation until more information is available.
During stroke treatment, continuous monitoring of blood pressure, heart rate, oxygen levels, and carbon dioxide levels is necessary. About 80% of people having an acute ischemic stroke have high blood pressure. Research has shown that both too high and too low blood pressure are associated with worse outcomes after a stroke. They recommend that no more than 15% of the baseline blood pressure is reduced initially. They also provide a few options for medications to control high blood pressure.
Maintaining good blood flow to the brain is a critical part of stroke treatment. Too low blood pressure is linked with poor outcomes, so the healthcare team will take steps to correct this and stabilize the patient. They must avoid giving too much fluid, though, as this can thin the blood too much. Unless low blood sugar is a concern, fluids given should not contain glucose.
Aspirin is usually given to patients with a stroke 24 to 48 hours after it happens. This should not replace other treatments for strokes, though, like breaking up or removing the clot causing the stroke. Supplemental oxygen may also be given to maintain a certain level of oxygen in your blood. Steps will be taken to avoid low oxygen levels and abnormal carbon dioxide levels.
A patient’s temperature should be kept in a specific range, and any high temperatures should be addressed quickly with medication or cooling methods as needed. Blood sugar should be monitored closely to prevent high levels and bouts of low blood sugar. Routine use of preventive antibiotics, seizure medications, and laying flat has not been proven to be beneficial. After the procedure, patients should be moved to a special care unit for continuous monitoring of their heart function and brain health.
Possible Complications of Anesthesia for Endovascular Therapy for Acute Ischemic Stroke in Adults
There may be several complications that come with performing a surgery on the brain or the blood vessels. These include bleeding within the brain (intracranial hemorrhage), the tearing of a blood vessel (vessel dissection), and the movement of a clot to new areas in the blood vessels causing blockages (emboli). Other complications might include narrowing of blood vessels (vasospasm), the movement or blockages in the small tube that holds blood vessels open (stent dislocation/occlusion), and the leakage of blood or other fluids from a blood vessel to surrounding tissues (extravasation).
What Else Should I Know About Anesthesia for Endovascular Therapy for Acute Ischemic Stroke in Adults?
An acute ischemic stroke is a kind of stroke that occurs when the blood supply to the brain is obstructed, usually by a blood clot. It’s essential to administer treatment as rapidly as possible for such strokes to prevent greater damage to the brain. This is because the longer you wait, the more brain tissue (known as the penumbra) can be lost, leading to poorer recovery.
Quick and efficient anesthesia is a big part of this treatment plan. This is because it allows doctors to perform a procedure called mechanical thrombectomy, which is basically a way to physically remove the clot causing the stroke. Stabilizing the patient’s bodily functions and blood pressure (often referred to as “hemodynamic stability”) is also one of the top priorities for patients undergoing this stroke treatment.
The key takeaway is this: prompt medical action can make a huge difference when dealing with an acute ischemic stroke. That’s why it’s so crucial to seek immediate medical attention if one suspects they’re having a stroke.
