Ultrasound, Arterial Doppler, Lower and Upper Extremity Studies


Ultrasound, Arterial Doppler, Lower and Upper Extremity Studies

Synonym/acronym: Doppler, arterial ultrasound, duplex scan.

Common use

To visualize and assess blood flow through the arteries of the upper and lower extremities toward diagnosing disorders such as occlusion and aneurysm and evaluate for the presence of plaque and stenosis. This procedure can also be used to assess the effectiveness of therapeutic interventions such as arterial graphs and blood flow to transplanted organs.

Area of application

Arteries of the lower and upper extremities.

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, arterial leg US records sound waves to obtain information about the arteries of the lower extremities from the common femoral arteries and their branches as they extend into the calf area. The amplitude and waveform of the pulses are measured, resulting in a two-dimensional image of the artery. Blood flow direction, velocity, and the presence of flow disturbances can be readily assessed, and for diagnostic studies, the technique is done bilaterally. The sound waves hit the moving red blood cells and are reflected back to the transducer corresponding 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, and location) of plaque causing vessel stenosis or occlusion and to help determine the cause of claudication. Arterial reconstruction and graft condition and patency can also be evaluated.

In arterial Doppler studies, arteriosclerotic disease of the peripheral vessels can be detected by slowly deflating blood pressure cuffs that are placed on an extremity such as the calf, ankle, or upper extremity. The systolic pressure of the various arteries of the extremities can be measured. The Doppler transducer can detect the first sign of blood flow through the cuffed artery, even the most minimal blood flow, as evidenced by a swishing noise. There is normally a reduction in systolic blood pressure from the arteries of the arms to the arteries of the legs; a reduction exceeding 20 mm Hg is indicative of occlusive disease (deep vein thrombosis) proximal to the area being tested. This procedure may also be used to monitor the patency of a graft, status of previous corrective surgery, vascular status of the blood flow to a transplanted organ, blood flow to a mass, or the extent of vascular trauma.

The ankle-brachial index (ABI) can also be assessed during this study. This noninvasive, simple comparison of blood pressure measurements in the arms and legs 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

  • Aid in the diagnosis of small or large vessel PAD
  • Aid in the diagnosis of spastic arterial disease, such as Raynaud’s phenomenon
  • Assist in the diagnosis of aneurysm, pseudoaneurysm, hematoma, arteriovenous malformation, or hemangioma
  • Assist in the diagnosis of ischemia, arterial calcification, or plaques, as evidenced by visualization of blood flow disruption
  • Detect irregularities in the structure of the arteries
  • Detect plaque or stenosis of the lower extremity artery, as evidenced by turbulent blood flow or changes in Doppler signals indicating occlusion
  • Determine the patency of a vascular graft, stent, or previous surgery
  • Evaluate possible arterial trauma

Potential diagnosis

Normal findings

  • Normal blood flow through the lower extremity arteries with no evidence of vessel occlusion or narrowing
  • Normal arterial systolic and diastolic Doppler signals
  • Normal reduction in systolic blood pressure (i.e., less than 20 mm Hg) when compared to a normal extremity
  • Normal ABI (greater than 0.85)

Abnormal findings related to

  • ABI less than 0.85, indicating significant arterial occlusive disease within the extremity
  • Aneurysm
  • Arterial calcification or plaques
  • Embolic arterial occlusion
  • Graft diameter reduction
  • Hemangioma
  • Hematoma
  • Ischemia
  • PAD
  • Pseudoaneurysm
  • Reduction in vessel diameter of more than 16%, indicating stenosis
  • Spastic arterial occlusive disease, such as Raynaud’s phenomenon

Critical findings

    N/A

Interfering factors

  • Factors that may impair the results of the examination

    • 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

  • Other considerations

    • Cold extremities, resulting in vasoconstriction, which can cause inaccurate measurements
    • Occlusion proximal to the site being studied, which would affect blood flow to the area
    • Cigarette smoking, because nicotine can cause constriction of the peripheral vessels
    • An abnormally large leg, making direct examination difficult

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 blood flow to the upper and lower extremities.
  • 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.
  • Report the presence of a lesion that is open or draining; maintain clean, dry dressing for the ulcer; protect the limb from trauma.
  • Note any recent procedures that can interfere with test results (i.e., barium or iodine-based contrast procedures, surgery, or biopsy). There should be24 hr between administration of barium or iodine contrast medium and this test.
  • Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values online at DavisPlus).
  • 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) specializing 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 area of interest and drape the patient.
  • Place blood pressure cuffs on the thigh, calf, and ankle.
  • Apply conductive gel to the skin over the area distal to each of the cuffs to promote the passage of sound waves as a Doppler transducer is moved over the skin to obtain images of the area of interest.
  • Inflate the thigh cuff to a level above the patient’s systolic pressure found in the normal extremity.
  • Place the Doppler transducer in the gel, distal to the inflated cuff, and slowly release the pressure in the cuff.
  • When the swishing sound of blood flow is heard, record it at the highest point along the artery at which it is audible. The test is repeated at the calf and then the ankle.

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 diet, fluids, and medications, as directed by the HCP.
  • Nutritional Considerations: 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 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 of 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. Patients on low-sodium diets should be advised to avoid beverages such as colas, ginger ale, sports drinks, lemon-lime sodas, and root beer. Many over-the-counter medications, including antacids, laxatives, analgesics, sedatives, and antitussives, contain significant amounts of sodium. The best advice is to emphasize the importance of reading all food, beverage, and medicine labels.
  • Recognize anxiety related to test results, and be supportive of 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. Provide contact information, if desired, for the American Heart Association (www.americanheart.org), the National Heart, Lung, and Blood Institute (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.
  • 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 alveolar/arterial ratio, ANA, angiography pulmonary, aPTT, blood gases, CBC platelet count, CT angiography, d-Dimer, FDP, fibrinogen, lung perfusion scan, lung ventilation scan, MRI abdomen, MRI angiography, plethysmography, PT/INR, US venous Doppler lower extremities, and venography lower extremity.
  • Refer to the Cardiovascular System table at the end of the book for related tests by body system.