An arteriovenous malformation (AVM) is an abnormal cluster of blood vessels that lack a capillary network. Recall that capillaries are those small blood vessels that deliver oxygen to the tissues and connect arteries to veins so the blood can return to the heart. This lack of a capillary network results in both disrupted blood flow and disrupted oxygen delivery. The blood flow inside an AVM is a rapid circulating blood flow which leads to vasodilation of the upstream artery, causing it to weaken and possibly even rupture. AVMs are most commonly seen in the brain and spinal cord, but can occur anywhere in the body.
Individuals most at risk for AVM are those with a specific gene mutation, a family history of AVM and those with a condition called hemorrhagic telangiectasia (HHT).
Maximize your learning about AVMs by reading this article and then listening to this information in episode 241 of the Straight A Nursing podcast. Tune in wherever you get your podcast fix, or straight from the website here.
What are the complications of AVM?
The most significant complication of AVM is hemorrhage due to the weakened or ruptured vessel wall. There’s also risk of stroke due to the formation of blood clots in the area of disrupted flow or due to decreased blood flow to that area of the brain. Both of these conditions can be fatal.
Individuals with AVM are also at risk for seizure, dementia or impaired cognitive function and intracranial microbleeds. They can also cause tissue necrosis and damage nearby nerves leading to loss of function and/or sensation to the affected area.
Now that you’ve got a little background knowledge about AVMs, let’s go through this condition using the Straight A Nursing LATTE method.
L: How does the patient with an AVM LOOK??
In other words, what are their signs and symptoms?
Most of the S/S of AVM are neurological in nature:
- The patient may complain of headaches, dizziness, visual changes and problems with memory.
- They could exhibit ataxia (loss of coordination) which can lead to gait abnormalities
- They could also have back pain, lower extremity weakness and paresthesia if the AVM is located in the spinal cord.
- Aphasia may be present, which means the individual has difficulty with speech (both speaking and understanding)
- Some patients may even experience dementia, hallucinations, confusion and even seizures.
- Learning and behavior disorders may be subtle and show up years before the more noticeable symptoms.
- If the thermoregulation center of the brain is affected, the individual could have a high body temperature not related to an infectious process (this is called “central fever” or “neurogenic fever.”)
- Skin lesions may be present on the torso, neck and extremities due to lack of oxygen delivery to underlying tissues.
A: How do you ASSESS the patient with an AVM?
Your priority assessment will be to monitor your patient for any neurological impairment. For a detailed discussion about neuro assessment, check out this article. Key things to make note of are:
- Any sudden deterioration in neurological status – this could indicate a stroke is occurring either due to hemorrhage, blood clot or lack of adequate blood flow to a portion of the brain
- Any signs of stroke – slurred speech, visual changes, loss of movement/sensation in one side of the body, difficulty understanding language, facial droop, etc…
- A sudden-onset, very severe headache. This is often described as “the worst headache of my life” or “like a thunderclap.” This is a sign of hemorrhagic stroke and is a neurological emergency!
- Assess for any loss of sensation or numbness/tingling in the extremities.
- Assess for musculoskeletal abnormalities – Assess hand grip by having the patient squeeze both of your hands. Assess ankle strength by having the patient perform dorsiflexion and plantar flexion against resistance. Other strength assessments include holding the arms up for a count of 10 and holding the legs off the bed for a count of 5 (the legs are done individually).
- Assess the patient’s gait, making note of difficulties that put them at risk for falls.
- Perform a full skin assessment, looking for skin lesions or tissue necrosis.
- Listen for the presence of a bruit, which resembles a blowing sound caused by the very rapid blood flow through the AVM.
T: What TESTS will be conducted for AVM?
The tests for AVM will be aimed at identifying the abnormal structure through imaging studies. These include:
- Cerebral angiography (also called CT angiography) – This test utilizes contrast dye and radiation to show the structure of blood vessels. This test supplies the most reliable images for AVM identification.
- CT scan – This test uses radiation to create images and is most useful when assessing for the presence of hemorrhage.
- Magnetic resonance imaging (MRI) – This test will show abnormalities in neurological tissues.
- Magnetic resonance angiography (MRA) – This test will show blood flow abnormalities in the brain and spinal card and is considered a good option for those who cannot tolerate the contrast dye used in cerebral angiography.
- Doppler ultrasound may be done to measure blood flow. A specific doppler called a “transcranial doppler ultrasound” measures how fast blood is flowing through the brain.
T: What TREATMENTS are provided for someone with an AVM?
The goal of treatment in AVM is to improve blood flow to the tissues and prevent complications. Some patients may simply be observed for any changes to the size and blood flow of their AVM. When intervention is needed, two common procedures are sclerotherapy and embolization. Though not curative, these procedures can prevent the AVM from progressing.
Sclerotherapy – In sclerotherapy, a sclerosing agent is injected into the malformation which destroys the vessels and causes scars to form, thereby decreasing blood flow through the AVM.
Endovascular embolization – In embolization, special materials such as medical glue or coils are deployed through a catheter and placed inside the AVM to block blood flow.
Surgery – Surgery may be conducted to remove the AVM or reduce its size. Surgery is typically only considered when the malformation is located superficially and smaller in size.
Radiosurgery – This is a minimally invasive treatment option that may be used for small AVMs that have not ruptured. In this procedure, a beam of radiation is focused on the AVM to damage the vessels causing them to close over the next several months.
Ablation – Another procedure is percutaneous radiofrequency ablation. In this procedure, the tissue of the AVM is destroyed through a very high powered and continuous radiofrequency ablation technique. It may be considered in those who have complex AVMs not treatable with surgery, sclerotherapy or embolization.
E: How do you EDUCATE the individual with an AVM?
The most important thing to teach your patient is to recognize signs of stroke, especially hemorrhagic stroke. These include the sudden and very severe “worst in my life” headache, visual problems, difficulty with speech, and movement.
Patients who undergo an invasive procedure such as surgery will receive standard post-op teaching, and include monitoring for signs of infection such as fever, redness/swelling at the surgical site, purulent drainage and increasing pain at the surgical site.
Some patients may be sent home with heparin for anticoagulation for a period of time post operatively. Ensure the patient understands how to administer the medication and properly dispose of sharps. They will also need education on bleeding precautions such as using an electric razor, avoiding falls, and being extra careful with sharp objects.
After surgical excision, the patient should be re-educated on the signs and symptoms of AVM, as it is common for the malformation to reoccur.
So there you have it, your quick guide to caring for patients with AVMs. Looking for more neurological topics? Explore them here!
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