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    Blood Pressure: Lower Extremity - CE

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    Aug.29.2024

    Blood Pressure: Lower Extremity - CE/NCPD

    ALERT

    If unable to palpate an artery because of a weak pulse, use an ultrasonic stethoscope (Figure 1)Figure 1.

    Blood pressure (BP) measurements with an electronic BP device may be affected by excessive movement, such as with seizures, tremors, or shivering, and irregular heart rates.

    OVERVIEW

    BP is the force exerted by blood against the vessel walls. During a normal cardiac cycle, BP reaches a peak, followed by a trough. The peak pressure occurs when the heart’s ventricular contraction, or systole, forces blood under high pressure into the aorta. When the ventricles relax, the blood remaining in the arteries exerts a trough, or diastolic, pressure against the arterial wall. Diastolic pressure is the minimum pressure exerted against the arterial wall.

    Patients at risk for alterations in BP measurement include those who have:

    • Circulatory shock (hypovolemic, septic, cardiogenic, or neurogenic)
    • Acute or chronic pain
    • Rapid IV infusion of fluids or blood products
    • Increased intracranial pressure
    • Postoperative status
    • Preeclampsia of pregnancy

    The standard unit for measuring BP is millimeters of mercury (mm Hg). The measurement indicates the height at which BP can sustain the column of mercury.

    The most common techniques for measuring BP are auscultation, using a sphygmomanometer and stethoscope, and measurement using an electronic BP monitor. Palpation may be used to obtain an estimate of systolic BP before using the auscultation method.

    During auscultation, as the sphygmomanometer cuff is deflated, five different sounds, called Korotkoff sounds, are heard over the artery. Each sound has a distinct characteristic (Figure 2)Figure 2. BP is recorded with the systolic reading (first Korotkoff sound) before the diastolic reading (beginning of the fifth Korotkoff sound). The difference between systolic pressure and diastolic pressure is the pulse pressure. For a BP of 120/80 mm Hg, the pulse pressure is 40 mm Hg, the difference between 120 mm Hg and 80 mm Hg. Systolic BP readings tend to be higher in more distal arteries, whereas diastolic BP readings tend to be lower in more distal arteries.undefined#ref4">4,5 The thigh or lower calf/ankle is used if measurement of the upper arms and forearms is not possible.8 Ankle blood pressure is clinically effective in diagnosing hypertension when the upper arm is not available for proper cuff placement.7

    Cuff size should be proportionate to the limb circumference (Table 1)Table 1. An improperly sized cuff produces an inaccurate BP measurement. Using a cuff that is too narrow results in an overestimation of BP, whereas using a cuff that is too wide results in an underestimation of BP.4 Most adults require a large adult cuff, particularly when the cuff is used for taking BP in a lower extremity.4 A bariatric cuff may be needed for larger adults. The correct cuff size is especially important for obtaining accurate readings in pediatric patients and patients with obesity.5

    SUPPLIES

    See Supplies tab at the top of the page.

    EDUCATION

    • Provide developmentally and culturally appropriate education based on the desire for knowledge, readiness to learn, and overall neurologic and psychosocial state.
    • Explain the equipment and the procedure to the patient and family.
    • Instruct the patient and family about ambulatory BP threshold guidelines. In adults, normal BP is less than 120/80 mm Hg (Table 2)Table 2.2,3
    • Educate the patient and family about the risk factors for hypertension.
      • Family history of hypertension, premature heart disease, lipidemia, or renal disease
      • Obesity
      • Cigarette smoking
      • Heavy alcohol consumption
      • High blood cholesterol and triglyceride levels
      • Prolonged stress from psychosocial and environmental factors
      • Sedentary lifestyle
    • Educate the patient and family regarding the primary strategies for preventing hypertension.1
      • Managing weight
      • Engaging in daily exercise
      • Limiting sodium and saturated fat in the diet
      • Maintaining adequate intake of dietary potassium and calcium
      • Taking medication as prescribed
      • Limiting alcohol intake
      • Avoiding tobacco products
    • Instruct the patient and family to ensure that the patient has adequate rest before BP measurements and that BP measurements are performed at the same time each day using the same limb with the patient in the same position, either prone or supine.
    • Explain that the patient must remain still and quiet during the procedure.
    • Explain that Korotkoff sounds may be difficult to hear for one of the following reasons (Table 3)Table 3.
      • Cuff is too loose, not big enough, or too narrow.
      • Stethoscope is not over the arterial pulse.
      • Cuff is deflated too quickly or too slowly.
      • Cuff is not pumped high enough for systolic readings.
    • Encourage questions and answer them as they arise.

    ASSESSMENT AND PREPARATION

    Assessment

    1. Perform hand hygiene before patient contact. Don appropriate personal protective equipment (PPE) based on the patient’s need for isolation precautions or the risk of exposure to bodily fluids.
    2. Introduce yourself to the patient.
    3. Verify the correct patient using two identifiers.
    4. Review the patient’s medical record for a history of hypertension, cardiovascular disease, renal disease, diabetes, and other factors that may influence BP (e.g., weight, smoking, medications).
    5. Assess the patient for risk factors for BP alterations.
      1. Circulatory shock (hypovolemic, septic, cardiogenic, or neurogenic)
      2. Acute or chronic pain
      3. Rapid IV infusion of fluids or blood products
      4. Increased intracranial pressure
      5. Postoperative status
      6. Preeclampsia of pregnancy
    6. Assess the patient for signs and symptoms of BP alterations.
      1. Assess a patient at risk for high BP for the following signs and symptoms.
        1. Headache (usually occipital)
        2. Facial flushing
        3. Nosebleed
        4. Fatigue
      2. Assess a patient at risk for low BP for the following signs and symptoms.
        1. Dizziness
        2. Mental confusion
        3. Restlessness
        4. Pale, dusky, or cyanotic skin and mucous membranes
        5. Cool, mottled skin over the extremities
    7. Determine the best site for BP assessment. Avoid applying the cuff to an extremity in the following situations.
      1. The extremity has been traumatized.
      2. The extremity has known infections or medical conditions (e.g., those causing vasoconstriction or a tumor pressing on the vascular supply).
      3. The extremity has a cast or bulky bandage.
    8. Determine the previous baseline BP and measurement site, if available, from the patient’s record.
    9. Determine the appropriateness of using an electronic BP measurement (Box 1)Box 1.

    Preparation

    1. Make sure the patient has not exercised, ingested caffeine, or smoked for 30 minutes before BP assessment.2 Make sure the patient does not have to void.
      Rationale: A full bladder increases pressure on the kidneys and can increase blood pressure.
    2. Make sure the room is warm (approximately 22°C to 23°C [71.6°F to 73.4°F]).4
      Rationale: Exposure to cold can increase systolic BP.4
    3. Measure lower extremity circumference and select the appropriate-size cuff (Table 1)Table 1.
      Rationale: An improperly sized cuff produces inaccurate BP measurements.
    4. Tell the patient that BP will be taken and that the cuff will squeeze the leg.

    PROCEDURE

    Auscultation Method

    1. Perform hand hygiene and don gloves. Don additional PPE based on the patient’s need for isolation precautions or the risk of exposure to bodily fluids.
    2. Verify the correct patient using two identifiers.
    3. Explain the procedure and ensure that the patient agrees to treatment.
    4. Assist the patient to a prone position. If the patient is unable to assume a prone position, assist the patient to a supine position with the knee slightly flexed. Ask the patient not to cross the legs.
      Rationale: The prone position provides the best access to the popliteal artery. Leg crossing can increase systolic and diastolic BP.
    5. Expose the patient’s leg fully by removing any constricting clothing. Do not place the BP cuff over clothing.
      Rationale: Placing the cuff over clothing may affect the BP measurement.
    6. Apply the BP cuff.
      1. Thigh
        1. Palpate the popliteal artery for a pulse.
        2. Position the cuff over the lower third of the patient’s thigh.4
        3. Apply the cuff over the popliteal artery and above the popliteal fossa.4 If the cuff has no center arrows, estimate the center of the bladder and place it over the artery (Figure 3)Figure 3.
          Rationale: Positioning the cuff bladder directly over the popliteal artery ensures that proper pressure is applied during inflation.
        4. Wrap the fully deflated cuff evenly and snugly around the patient’s thigh.
          Rationale: A loose-fitting cuff can cause an artificially high reading.
      2. Lower calf/ankle
        1. Palpate the dorsalis pedis or posterior tibial artery for a pulse.
        2. Position the cuff over the lower half of the patient’s calf.8
        3. Secure the deflated cuff evenly and snugly around the lower calf and above the malleoli.
          Rationale: A loose-fitting cuff can cause an artificially high reading.
    7. Position the manometer vertically at eye level.
      Rationale: Looking up or down at the scale can result in an incorrect reading.
    8. Ask the patient not to speak while BP is being measured.
    9. Place the stethoscope earpieces in the ears and make sure sounds are clear, not muffled.
    10. Locate the popliteal artery for thigh BP or the dorsalis pedis or posterior tibial artery for a calf BP; place either the bell or the diaphragm4 of the stethoscope over the artery below the lower edge of the cuff.
      1. Do not allow the chest piece to touch the cuff or clothing.
      2. Do not place the diaphragm under the cuff.
      3. If unable to palpate the artery because of weakened pulse, use an ultrasonic stethoscope (Figure 1)Figure 1.
        Rationale: Proper stethoscope placement ensures the best sound reception. An improperly positioned stethoscope causes muffled sounds that often result in an artificially low systolic and an artificially high diastolic reading.
    11. Turn the valve of the pressure bulb clockwise until tight. Quickly inflate the cuff above the patient’s previously documented systolic pressure or the point at which Korotkoff sounds cease.
      Rationale: Closing the valve prevents air leak during inflation. Rapid cuff inflation ensures accurate measurement of systolic pressure.
    12. Slowly release the pressure bulb valve, allowing the manometer needle to fall slowly and continuously at a rate of 2 to 3 mm Hg per second.4
      Rationale: Too rapid or slow a decline in the mercury level can cause inaccurate measurements.
    13. Observe the point on the manometer at which the first Korotkoff sound is heard, indicating the systolic BP. The sound slowly increases in intensity.
      Rationale: The first Korotkoff sound is a snapping sound. This sound for at least two consecutive heartbeats reflects the systolic BP.
    14. Continue to deflate the cuff gradually; observe the point on the manometer at which all Korotkoff sounds disappear, indicating the diastolic BP.
      Rationale: The fifth Korotkoff sound falls silent as the cuff pressure drops below the diastolic pressure. Thus, the beginning of the fifth Korotkoff sound indicates diastolic pressure in adults.4
    15. When the sounds disappear, quickly deflate the cuff completely.
    16. Remove the cuff from the patient’s leg unless a repeat measurement is needed.
      Rationale: Continuous cuff inflation causes arterial occlusion, resulting in numbness and tingling of the patient’s leg.
    17. If this is the patient’s first BP assessment, repeat the procedure on the other leg.
      Rationale: Comparing BP in both legs helps detect circulatory problems.
    18. Help the patient resume a comfortable position and cover the leg if previously clothed. Inform the patient of the BP reading, as appropriate.
    19. Report abnormal values to the practitioner (Table 2)Table 2.
    20. Clean the BP cuff per the manufacturer’s instructions and the organization’s practice. Clean the earpieces and diaphragm of the stethoscope with an alcohol swab or per the organization’s practice. Return the equipment to its assigned storage space.
    21. Discard supplies, remove PPE, and perform hand hygiene.
    22. Document the procedure in the patient’s record.

    Electronic Method

    1. Perform hand hygiene and don gloves. Don additional PPE based on the patient’s need for isolation precautions or the risk of exposure to bodily fluids.
    2. Verify the correct patient using two identifiers.
    3. Explain the procedure and ensure that the patient agrees to treatment.
    4. Assist the patient to a prone position. If the patient is unable to assume a prone position, assist the patient to a supine position with the knee slightly flexed. Ask the patient not to cross the legs.
      Rationale: The prone position provides the best access to the popliteal artery. Leg crossing can increase BP.
    5. Plug in the device and place it near the patient’s extremity and then choose an appropriate-size cuff (Table 1)Table 1. Ensure that the BP cuff is appropriate for the electronic device per the manufacturer’s instructions.
    6. Prepare the BP cuff by manually squeezing all the air out of it and connecting it to the connector hose.
    7. Expose the patient’s leg fully by removing any constricting clothing. Do not place the BP cuff over clothing.
      Rationale: Placing the cuff over clothing may affect the BP measurement.
    8. Apply the BP cuff. Do not place the cuff over a bony prominence, superficial nerve, or joint.4
      1. Thigh
        1. Palpate the popliteal artery for a pulse.
        2. Position the cuff over the lower third of the patient’s thigh (Figure 3)Figure 3.8
        3. Apply the cuff over the popliteal artery and above the popliteal fossa.8 If the cuff has no center arrows, estimate the center of the bladder and place it over the artery.
          Rationale: Positioning the cuff bladder directly over the popliteal artery ensures that proper pressure is applied during inflation.
        4. Wrap the fully deflated cuff evenly and snugly around the patient’s thigh.
          Rationale: A loose-fitting cuff can cause an artificially high reading.
      2. Lower calf/ankle
        1. Position the cuff over the lower half of the patient’s calf.8
        2. Apply the cuff to the lower calf and above the malleoli.8
        3. Secure the fully deflated cuff evenly and snugly around the patient’s lower calf and above the malleoli.
    9. Ask the patient not to speak while BP is being measured.
    10. Verify that the connector hose between the cuff and the machine is not kinked.
    11. Set the frequency control for automatic or manual and then press the start button following the manufacturer’s instructions.
    12. When the deflation is complete, observe the digital display, which provides the most recent values.
    13. Obtain additional readings by pressing the start button rather than the cancel button.
      Rationale: Pressing the cancel button immediately deflates the cuff.
    14. If frequent BP measurements are required, leave the cuff in place. Set the frequency of BP measurements and the upper and lower alarm limits for systolic, diastolic, and mean BP readings.
      1. Remove the cuff at regular intervals to assess the underlying skin integrity.
      2. If possible, alternate BP sites.
        Patients with abnormal bleeding tendencies are at risk for microvascular rupture from repeated inflations.
    15. Remove the cuff from the patient’s leg unless a repeat measurement is needed.
      Rationale: Continuous cuff inflation causes arterial occlusion, resulting in numbness and tingling of the patient’s leg.
    16. If this is the patient’s first BP assessment, repeat the procedure on the other leg.
      Rationale: Comparing BP in both legs helps detect circulatory problems.
    17. Help the patient return to a comfortable position and cover the leg if previously clothed. Inform the patient of the BP reading, as appropriate.
    18. Report abnormal values to the practitioner (Table 2)Table 2.
    19. Clean the BP cuff per the manufacturer’s instructions. Return the equipment to its assigned storage space.
    20. Discard supplies, remove PPE, and perform hand hygiene.
    21. Document the procedure in the patient’s record.

    MONITORING AND CARE

    1. If assessing lower extremity BP for the first time, establish the BP reading as the lower extremity baseline if it is within the acceptable range.
    2. Compare the lower extremity BP reading with patient’s previous lower extremity baseline and the usual BP for the patient’s age.
    3. Assess, treat, and reassess pain.

    EXPECTED OUTCOMES

    • BP is within acceptable range for the patient’s age and body size.
    • Patient tolerates procedure.

    UNEXPECTED OUTCOMES

    • BP is above or below acceptable range.
    • BP is insufficient for adequate perfusion and oxygenation of tissues.
    • BP reading cannot be obtained.
    • Patient experiences orthostatic hypotension.
    • A significant difference exists between left leg and right leg BP readings.

    DOCUMENTATION

    • BP measurement
    • Method
    • Site assessed and patient’s position
    • BP measurement after administration of specific therapies
    • Signs and symptoms of BP alterations
    • Abnormal findings
    • Unexpected outcomes and related interventions
    • Education

    PEDIATRIC CONSIDERATIONS

    • Thigh BP measurement is uncomfortable for pediatric patients. The right arm is preferred for BP measurement in pediatric patients.6
    • Measure the patient’s BP before performing anxiety-producing tests or procedures.
    • Assess the BP of a pediatric patient with respect to body size and age.
      • Heavier and taller patients have a higher BP than smaller patients of the same age.
      • During adolescence, BP continues to vary according to body size.
      • The normal range for 10- to 17-year-old patients at the 90th percentile for weight is systolic 124 to 136 mm Hg and diastolic 77 to 84 mm Hg for biological male patients and systolic 124 to 127 mm Hg and diastolic 63 to 74 mm Hg for biological female patients.4
    • Korotkoff sounds are difficult to hear in pediatric patients because of the low frequency and amplitude.
    • Though the beginning of the fifth Korotkoff sound indicates diastolic pressure in adults, the fourth Korotkoff (distinct muffling) indicates diastolic pressure in pediatric patients.

    OLDER ADULT CONSIDERATIONS

    • The skin of older adults is more fragile and susceptible to damage from cuff pressure when BP measurements are frequent. More frequent assessment of the skin under the cuff or rotation of BP sites is recommended.
    • Older adults have increased systolic pressure related to decreased vessel elasticity.
    • Older adults may be more likely to have peripheral vascular disease.
    • Older adults often experience a fall in BP after eating.
    • Instruct older adults to change position slowly and wait after each change to avoid postural hypotension and prevent injuries.

    HOME CARE CONSIDERATIONS

    • Assess the home noise level to determine the room that provides the quietest environment for BP measurement.
    • Teach the patient the importance of using an appropriate-size BP cuff for home BP measurement.
    • Assess the family’s ability to afford a sphygmomanometer for performing BP evaluations on a regular basis. Recommend electronic devices or aneroid sphygmomanometers that have proven to be accurate according to standard testing as well as appropriate-size cuffs.

    REFERENCES

    1. American Heart Association (AHA). (2024). How to Manage High Blood Pressure. Retrieved July 2, 2024, from https://www.heart.org/en/health-topics/high-blood-pressure/changes-you-can-make-to-manage-high-blood-pressure
    2. American Heart Association. (AHA). (2024). Home Blood Pressure Monitoring. Retrieved July 2, 2024, from https://www.heart.org/en/health-topics/high-blood-pressure/understanding-blood-pressure-readings/monitoring-your-blood-pressure-at-home#.Wuct7ExFwy9
    3. American Heart Association (AHA). (2024). Understanding blood pressure readings. Retrieved July 2, 2024, from https://www.heart.org/en/health-topics/high-blood-pressure/understanding-blood-pressure-readings#.Wucr9UxFwy9
    4. Muntner, P. and others. (2019). Measurement of blood pressure in humans: A scientific statement from the American Heart Association. Hypertension, 73(5), e35-e66. doi:10.1161/HYP.0000000000000087
    5. Pickering, T.G. and others. (2005). Recommendations for blood pressure measurement in humans and experimental animals. Part 1: Blood pressure measurement in humans: A statement for professionals from the Subcommittee of Professional and Public Education of the American Heart Association Council on High Blood Pressure Research. Hypertension, 45(1), 142-161. doi:10.1161/01.HYP.0000150859.47929.8e Retrieved July 2, 2024, from https://www.ahajournals.org/doi/full/10.1161/01.HYP.0000150859.47929.8e
    6. Schroeder, M.L. and others. (2024). Chapter 27: The child with cardiovascular dysfunction. In M.J. Hockenberry, E.A. Duffy, K.D. Gibbs (Eds.), Wong’s nursing care of infants and children (12th ed., pp. 949-1012). St. Louis: Elsevier.
    7. Sheppard, J. and others. (2019). Defining the relationship between arm and leg blood pressure readings: A systematic review and meta-analysis. Journal of Hypertension, 37(4), 660-670. Retrieved July 2, 2024, from https://journals.lww.com/jhypertension/Abstract/2019/04000/Defining_the_relationship_between_arm_and_leg.2.aspx
    8. Sheppard, J. and others. (2020). Measurement of blood pressure in the leg—A statement on behalf of the British and Irish Hypertension Society. Journal of Human Hypertension, 34(6), 418-419. doi:10.1038/s41371-020-0325-5

    Adapted from Perry, A.G. and others (Eds.). (2022). Clinical nursing skills and techniques (10th ed.). St. Louis: Elsevier.

    Clinical Review: Martha Beck, MA, BSN, RN, CNOR

    Published: August 2024

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