Ankle Brachial Indexby: SECEI ESCS on YouTube
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Purpose: Diagnose the presence of arterial insufficiency or critical limb ischemia in the lower leg. Examine the appropriateness of use of compression in lymphedema or venous insufficiency. It also establishes a baseline for severity of arterial disease in the lower limb. An abnormal result of an ankle brachial index (ABI) may also suggest atherosclerosis in other parts of the body.
Procedure: Equipment needed: Continuous wave doppler machine (handheld at 8-9 MHz), ultrasound gel, thigh blood pressure cuff, arm blood pressure cuff. Procedure: 1. "Place the blood-pressure cuff on the patient’s right or left arm above the elbow crease. 2. Palpate the brachial pulse. 3. Apply gel at the site where you feel the pulse, and obtain a Doppler signal by placing the probe at a 60-degree angle toward the patient’s head. 4. Inflate the cuff rapidly to 20 to 30 mm Hg above the point of cessation of brachial-artery flow, then slowly deflate the blood-pressure cuff in order to note the systolic value. 5. Wipe the gel from the patient’s skin and repeat the procedure on the other arm. Record the systolic blood pressure of the arms. 6. After measuring the systolic blood pressure in the arms, place the cuff just above the ankle on the right or left leg. The anatomical landmark of the dorsalis pedis artery should be lateral to the extensor hallucis longus tendon. 7. Place the Doppler probe on the palpable dorsalis pedis pulse or on the site that produces the best arterial Doppler signal from the dorsalis pedis artery. 8. Once again, inflate the blood-pressure cuff to 20 to 30 mm Hg above the level at which flow ceases, then deflate the cuff slowly and note the systolic pressure (the pressure at which you first hear the flow from the dorsalis pedis artery). 9. Repeat the procedure for the posterior tibial artery. Then repeat the procedure for the contralat- eral leg to obtain the systolic pressure from both the dorsalis pedis and posterior tibial arteries. Record these values. 10. To calculate the ankle–brachial index, divide the systolic blood pressure in the ankle by the systolic blood pressure in the arm. The higher brachial systolic pressure is usually chosen for calculation, simply because the vessels of an arm may be affected by arterial occlusive disease. The higher of the systolic pressures from the dorsalis pedis or posterior tibial artery is used to determine the ankle–brachial index" (Grenon, Gagnon, & Hsiang, 2009, p. e40(3)). Normal Result: A normal result is >/= 0.95 and less than 1.2. Abnormal Result: An abnormal result is </=0.9, indicating arterial insufficiency. Critical limb ischemia is generally noted at an ABI </=0.5. Calcification of the blood vessels is noted with an ABI >/=1.2. Clinical Notes: An ABI is contraindicated if a patient has a deep vein thrombosis. It has a sensitivity above 90% and a specificity of 95% for peripheral arterial disease. |
References
Grenon, S. M., Gagnon, J., & Hsiang, Y. (2009). Ankle-brachial index for assessment of peripheral arterial disease. N Engl J Med, 361(19), e40.
Weitz, J. I., Byrne, J., Clagett, G. P., Farkouh, M. E., Porter, J. M., Sackett, D. L., ... & Taylor, L. M. (1996). Diagnosis and treatment of chronic arterial insufficiency of the lower extremities: a critical review. Circulation, 94(11), 3026-3049.
Grenon, S. M., Gagnon, J., & Hsiang, Y. (2009). Ankle-brachial index for assessment of peripheral arterial disease. N Engl J Med, 361(19), e40.
Weitz, J. I., Byrne, J., Clagett, G. P., Farkouh, M. E., Porter, J. M., Sackett, D. L., ... & Taylor, L. M. (1996). Diagnosis and treatment of chronic arterial insufficiency of the lower extremities: a critical review. Circulation, 94(11), 3026-3049.
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