carotid ultrasound

carotid ultrasound

Imaging The use of ultrasound to evaluate blood flow through the carotid arteries in the neck in Pts at risk of CVAs or TIAs

Ultrasound, Arterial Doppler, Carotid Studies

Synonym/acronym: Carotid Doppler, carotid ultrasound, arterial ultrasound.

Common use

To visualize and assess blood flow through the carotid arteries toward evaluating risk for stroke related to atherosclerosis.

Area of application

Arteries.

Contrast

Done without contrast.

Description

Ultrasound (US) procedures are diagnostic, noninvasive, and relatively inexpensive. They take a short time to complete, do not use radiation, and cause no harm to the patient. High-frequency sound waves of various intensities are delivered by a transducer, a flashlight-shaped device, pressed against the skin. The waves are bounced back off internal anatomical structures and fluids, converted to electrical energy, amplified by the transducer, and displayed as images on a monitor.

Using the duplex scanning method, carotid US records sound waves to obtain information about the carotid arteries. The amplitude and waveform of the carotid pulse are measured, resulting in a two-dimensional image of the artery. Carotid arterial sites used for the studies include the common carotid, external carotid, and internal carotid. Blood flow direction, velocity, and the presence of flow disturbances can be readily assessed. The sound waves that hit the moving red blood cells and are reflected back to the transducer correspond to the velocity of the blood flow through the vessel. The result is the visualization of the artery to assist in the diagnosis (i.e., presence, amount, location) of plaque causing vessel stenosis or atherosclerotic occlusion affecting the flow of blood to the brain. Depending on the degree of stenosis causing a reduction in vessel diameter, additional testing can be performed to determine the effect of stenosis on the hemodynamic status of the artery.

The combined information obtained from carotid US and ankle-brachial index (ABI) provides significant support for predicting coronary artery disease. ABI is a noninvasive, simple comparison of blood pressure measurements in the arms and legs and can be used to detect peripheral artery disease (PAD). A Doppler stethoscope is used to obtain the systolic pressure in either the dorsalis pedis or the posterior tibial artery. This ankle pressure is then divided by the highest brachial systolic pressure acquired after taking the blood pressure in both of the patient’s arms. This index should be greater than 1. When the index falls below 0.5, blood flow impairment is considered significant. Patients should be scheduled for a vascular consult for an abnormal ABI. Patients with diabetes or kidney disease, and some elderly patients, may have a falsely elevated ABI due to calcifications of the vessels in the ankle causing an increased systolic pressure. The ABI test approaches 95% accuracy in detecting PAD. However, a normal ABI value does not absolutely rule out the possibility of PAD for some individuals, and additional tests should be done to evaluate symptoms.

This procedure is contraindicated for

    N/A

Indications

  • Assist in the diagnosis of carotid artery occlusive disease, as evidenced by visualization of blood flow disruption
  • Detect irregularities in the structure of the carotid arteries
  • Detect plaque or stenosis of the carotid artery, as evidenced by turbulent blood flow or changes in Doppler signals indicating occlusion

Potential diagnosis

Normal findings

  • Normal blood flow through the carotid arteries with no evidence of occlusion or narrowing

Abnormal findings related to

  • Carotid artery occlusive disease (atherosclerosis)
  • Plaque or stenosis of carotid artery
  • Reduction in vessel diameter of more than 16%, indicating stenosis

Critical findings

    N/A

Interfering factors

  • Factors that may impair clear imaging

    • Attenuation of the sound waves by bony structures, which can impair clear imaging of the vessels
    • Incorrect placement of the transducer over the desired test site; quality of the US study is very dependent upon the skill of the ultrasonographer
    • Metallic objects (e.g., jewelry, body rings) within the examination field, which may inhibit organ visualization and cause unclear images
    • Inability of the patient to cooperate or remain still during the procedure because of age, significant pain, or mental status

Nursing Implications and Procedure

Pretest

  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching: Inform the patient this procedure can assist in assessing the carotid arteries in the neck.
  • Obtain a history of the patient’s complaints or clinical symptoms, including a list of known allergens, especially allergies or sensitivities to latex.
  • Obtain a history of the patient’s cardiovascular system, symptoms, and results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Note any recent procedures that can interfere with test results (i.e., barium or iodine-based contrast procedures, surgery, or biopsy). There should be 24 hr between administration of barium or iodine contrast medium and this test.
  • Obtain a list of the patient’s current medications, including anticoagulants, aspirin and other salicylates, herbs, nutritional supplements, and nutraceuticals. (see Effects of Natural Products on Laboratory Values online at DavisPlus). Such products should be discontinued by medical direction for the appropriate number of days prior to a surgical procedure.
  • Review the procedure with the patient. Address concerns about pain related to the procedure and explain that some pain may be experienced during the test, and there may be moments of discomfort. Inform the patient that the procedure is performed in a US department by a health-care provider (HCP) who specializes in this procedure, with support staff, and takes approximately 30 to 60 min.
  • Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Instruct the patient to remove jewelry and other metallic objects from the area to be examined.
  • Note that there are no food, fluid, or medication restrictions unless by medical direction.

Intratest

  • Potential complications: N/A
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient.
  • Ensure that the patient has removed all external metallic objects from the area to be examined prior to the procedure.
  • Instruct the patient to void and change into the gown, robe, and foot coverings provided.
  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Instruct the patient to cooperate fully and to follow directions. Ask the patient to remain still throughout the procedure because movement produces unreliable results.
  • Place the patient in the supine position on an examination table; other positions may be used during the examination.
  • Expose the neck and drape the patient.
  • Conductive gel is applied to the skin, and a Doppler transducer is moved over the skin to obtain images of the area of interest.
  • Ask the patient to breathe normally during the examination. If necessary for better organ visualization, ask the patient to inhale deeply and hold his or her breath.

Post-Test

  • Inform the patient that a report of the results will be made available to the requesting HCP, who will discuss the results with the patient.
  • When the study is completed, remove the gel from the skin.
  • Instruct the patient to continue with diet, fluids, and medications, as directed by the HCP.
  • Nutritional Considerations: Abnormal findings may be associated with cardiovascular disease. Nutritional therapy is recommended for the patient identified to be at risk for developing coronary artery disease (CAD) or for individuals who have specific risk factors and/or existing medical conditions (e.g., elevated low-density lipoprotein [LDL] cholesterol levels, other lipid disorders, insulin-dependent diabetes, insulin resistance, or metabolic syndrome). Other changeable risk factors warranting patient education include strategies to encourage patients, especially those who are overweight and with high blood pressure, to safely decrease sodium intake, achieve a normal weight, ensure regular participation in moderate aerobic physical activity three to four times per week, eliminate tobacco use, and adhere to a heart-healthy diet. If triglycerides also are elevated, the patient should be advised to eliminate or reduce alcohol. The 2013 Guideline on Lifestyle Management to Reduce Cardiovascular Risk published by the American College of Cardiology (ACC) and the American Heart Association (AHA) in conjunction with the National Heart, Lung, and Blood Institute (NHLBI) recommends a “Mediterranean”-style diet rather than a low-fat diet. The new guideline emphasizes inclusion of vegetables, whole grains, fruits, low-fat dairy, nuts, legumes, and nontropical vegetable oils (e.g., olive, canola, peanut, sunflower, flaxseed) along with fish and lean poultry. A similar dietary pattern known as the Dietary Approaches to Stop Hypertension (DASH) diet makes additional recommendations for the reduction of dietary sodium. Both dietary styles emphasize a reduction in consumption of red meats, which are high in saturated fats and cholesterol, and other foods containing sugar, saturated fats, trans fats, and sodium.
  • Social and Cultural Considerations: Numerous studies point to the prevalence of excess body weight in American children and adolescents. Experts estimate that obesity is present in 25% of the population ages 6 to 11 yr. The medical, social, and emotional consequences of excess body weight are significant. Special attention should be given to instructing the child and caregiver regarding health risks and weight-control education.
  • Recognize anxiety related to test results, and be supportive of fear of shortened life expectancy and perceived loss of independent function. Discuss the implications of abnormal test results on the patient’s lifestyle. Provide teaching and information regarding the clinical implications of the test results, as appropriate. Educate the patient regarding access to counseling services. Provide contact information, if desired, for the AHA (www.americanheart.org), the NHLBI (www.nhlbi.nih.gov), or the Legs for Life (www.legsforlife.org).
  • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family.
  • Instruct the patient in the use of any ordered medications. Explain the importance of adhering to the therapy regimen. As appropriate, instruct the patient in significant side effects and systemic reactions associated with the prescribed medication. Encourage him or her to review corresponding literature provided by a pharmacist.
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

  • Related tests include angiography carotid, angiography coronary, antiarrhythmic drugs, apolipoprotein A & B, AST, blood gases, calcium, cholesterol (total, HDL, LDL), CT angiography, CT cardiac scoring, echocardiography, CRP, CK and isoenzymes, glucose, glycated hemoglobin, Holter monitor, homocysteine, ketones, LDH and isoenzymes, lipoprotein electrophoresis, magnesium, MRI angiography, MRI chest, MRI venography, myocardial infarction scan, myocardial perfusion heart scan, myoglobin, PET heart, triglycerides, troponin, US arterial Doppler upper and lower extremities, and US venous Doppler extremity.
  • Refer to the Cardiovascular System table at the end of the book for related tests by body system.