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May.27.2020

Blood Pressure: Lower Extremity - CE

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 that 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, which is 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 minimal pressure exerted against the arterial wall at all times.

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

Cuff size should be proportionate to the limb circumference (Table 1)Table 1. Most adults require a large adult cuff. An improper-size cuff produces inaccurate BP measurements. Studies show that using a cuff that is too narrow results in an overestimation of BP, and using a cuff that is too wide results in an underestimate of BP.undefined#ref1">1

When measuring BP in the upper arm is not possible—for example, when the available BP cuffs do not fit the upper arm properly—BP may be measured in the forearm. To obtain the most accurate reading, the nurse must use the proper size BP cuff for the forearm, which typically has a smaller circumference than the upper arm. BP measurements in the forearm and upper arm are not interchangeable. Forearm measurements tend to be higher than upper-arm measurements with the greater variability in systolic BPs.6 The thigh or calf can be used if measurement of the upper arms and forearms is not possible.1

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 Hg2 (Table 2)Table 2.
  • 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.7
    • Weight management
    • Daily exercise
    • Diet low in sodium and saturated fat
    • Adequate intake of dietary potassium and calcium
    • Avoidance of 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.
  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 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 in older adults
    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 minutes3 before BP assessment. Make sure the patient does not have to void.
  2. Rationale: The urge to void can significantly increase BP. 4
  3. Make sure the room is warm.
  4. Rationale: Exposure to cold can significantly increase systolic BP. 4
  5. Measure lower-extremity circumference and select the appropriate-size cuff (Table 1)Table 1.
  6. Rationale: An improper-size cuff produces inaccurate BP measurements. Studies show that using a cuff that is too narrow results in an overestimation of BP, and using a cuff that is too wide results in an underestimate of BP. 1
  7. Tell the patient that BP is going to be taken and that the cuff will squeeze the leg.

PROCEDURE

Auscultation Method

  1. Perform hand hygiene.
  2. Verify the correct patient using two identifiers.
  3. Explain the procedure to the patient and ensure that he or she 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 his or her legs.
  5. Rationale: The prone position provides the best access to the popliteal artery. Leg crossing can falsely increase systolic and diastolic BP.
  6. Expose the patient's leg fully by removing any constricting clothing. Do not place the BP cuff over clothing.
  7. Rationale: Placing the cuff over clothing may affect the BP measurement.
  8. 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.1
      3. Apply the cuff above the artery by centering the arrows marked on the cuff over the artery so that the lower edge of the cuff is 2 to 3 cm above the popliteal fossa to allow room for placement of the stethoscope.1 If the cuff has no center arrows, estimate the center of the bladder and place it over the artery (Figure 3)Figure 3.
      4. Rationale: Positioning the cuff bladder directly over the popliteal artery ensures that proper pressure is applied during inflation.
      5. Wrap the fully deflated cuff evenly and snugly around the patient's thigh.
      6. Rationale: A loose-fitting cuff causes false-high readings.
    2. Calf
      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.1
      3. Apply the cuff so that the lower edge of the cuff is about 2.5 cm above the malleoli.1
      4. Wrap the fully deflated cuff evenly and snugly around the patient's calf.
      5. Rationale: A loose-fitting cuff causes false-high readings.
  9. Position the manometer vertically at eye level.
  10. Rationale: Looking up or down at the scale can result in incorrect readings.
  11. Ask the patient not to speak while BP is being measured.
  12. Place the stethoscope earpieces in the ears and make sure sounds are clear, not muffled.
  13. Locate the popliteal artery for thigh BP, or the dorsalis pedis or posterior tibial artery for calf BP and place the diaphragm of the stethoscope over it below the lower edge of the cuff.
  14. Rationale: Using the bell of the stethoscope may cause inaccurate reading. 4
    1. Do not allow the chest piece to touch the cuff or clothing.
    2. Do not place the diaphragm under the cuff.4
    3. Do not place excessive pressure on the stethoscope head.4
    4. If unable to palpate the artery because of weakened pulse, use an ultrasonic stethoscope (Figure 1)Figure 1.
    5. Rationale: Proper stethoscope placement ensures the best sound reception. An improperly positioned stethoscope causes muffled sounds that often result in false-low systolic and false-high diastolic readings. Use of the bell and excessive pressure on the diaphragm of the stethoscope can lead to inaccurate BP measurements. 4
  15. 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.
  16. Rationale: Closing the valve prevents air leak during inflation. Rapid cuff inflation ensures accurate measurement of systolic pressure.
  17. 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
  18. Rationale: Too rapid or slow a decline in the mercury level causes inaccurate readings.
  19. Observe the point on the manometer at which the first Korotkoff sound is heard, indicating the systolic BP. The sound slowly increases in intensity.
  20. Rationale: The first Korotkoff sound is a snapping sound. This sound for at least two consecutive heartbeats reflects the systolic BP.
  21. Continue to deflate the cuff gradually; observe the point on the manometer at which all Korotkoff sounds disappear, indicating the diastolic BP.
  22. 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 The fourth Korotkoff sound involves distinct muffling of sounds and indicates diastolic pressure in children. 7
  23. When the sounds disappear, quickly deflate the cuff completely.
  24. Remove the cuff from the patient's leg unless a repeat measurement is needed.
  25. Rationale: Continuous cuff inflation causes arterial occlusion, resulting in numbness and tingling of the patient's leg.
  26. If this is the patient's first BP assessment, repeat the procedure on the other leg.
  27. Rationale: Comparing BP in both legs helps detect circulatory problems.
  28. Help the patient resume a comfortable position and cover the leg if previously clothed. Inform the patient of the blood pressure reading, as appropriate.
  29. Report abnormal values to the practitioner (Table 2)Table 2.
  30. Clean the BP cuff per the manufacturer’s instructions and the organization’s practice. Clean the earpieces and diaphragm of the stethoscope per the organization’s practice. Return the equipment to its assigned storage space.
  31. Discard supplies and perform hand hygiene.
  32. Document the procedure in the patient's record.

Electronic Method

  1. Perform hand hygiene.
  2. Introduce yourself to the patient.
  3. Verify the correct patient using two identifiers.
  4. Explain the procedure to the patient and ensure that he or she agrees to treatment.
  5. 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 his or her legs.
  6. Rationale: The prone position provides the best access to the popliteal artery. Leg crossing can falsely increase BP.
  7. 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.
  8. Prepare the BP cuff by manually squeezing all the air out of it and connecting it to the connector hose.
  9. Expose the patient's leg fully by removing any constricting clothing. Do not place the BP cuff over clothing.
  10. Rationale: Placing the cuff over clothing may affect the BP measurement.
  11. Apply the BP cuff. Do not place the cuff over a bony prominence, superficial nerve, or joint.1
    1. Thigh
      1. Palpate the popliteal artery for a pulse.
      2. Position the cuff over the lower third of the patient's thigh.1
      3. Apply the cuff above the artery by centering the arrows marked on the cuff over the artery so that the lower edge of the cuff is 2 to 3 cm above the popliteal fossa to allow room for placement of the stethoscope.1 If the cuff has no center arrows, estimate the center of the bladder and place it over the artery (Figure 3)Figure 3.
      4. Rationale: Positioning the cuff bladder directly over the popliteal artery ensures that proper pressure is applied during inflation.
      5. Wrap the fully deflated cuff evenly and snugly around the patient’s thigh.
        Rationale: A loose-fitting cuff causes false-high readings.
    2. Calf
      1. Position the cuff over the lower half of the patient's calf.1
      2. Apply the cuff so that the lower edge of the cuff is about 2.5 cm above the malleoli.1
      3. Wrap the fully deflated cuff evenly and snugly around the patient's calf.
    Rationale: A loose-fitting cuff causes false-high readings.
  12. Ask the patient not to speak while BP is being measured.
  13. Verify that the connector hose between the cuff and the machine is not kinked.
  14. Set the frequency control for automatic or manual and then press the start button following the manufacturer's instructions.
  15. When the deflation is complete, observe the digital display, which provides the most recent values.
  16. Obtain additional readings by pressing the start button rather than the cancel button.
  17. Rationale: Pressing the cancel button immediately deflates the cuff.
  18. 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.
    3. Patients with abnormal bleeding tendencies are at risk for microvascular rupture from repeated inflations.
  19. Remove the cuff from the patient's leg unless a repeat measurement is needed.
  20. Rationale: Continuous cuff inflation causes arterial occlusion, resulting in numbness and tingling of the patient's leg.
  21. If this is the patient's first BP assessment, repeat the procedure on the other leg.
  22. Rationale: Comparing BP in both legs helps detect circulatory problems.
  23. Help the patient return to a comfortable position and cover the leg if previously clothed. Inform the patient of the blood pressure reading, as appropriate.
  24. Report abnormal values to the practitioner (Table 2)Table 2.
  25. Clean the BP cuff per the manufacturer’s instructions. Return the equipment to its assigned storage space.
  26. Discard supplies and perform hand hygiene.
  27. 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 nursing interventions
  • Education

PEDIATRIC CONSIDERATIONS

  • BP measurement is not a routine part of assessment in children younger than 3 years of age.5
  • Thigh BP measurement is uncomfortable for children. The right arm is preferred for BP measurement in children.7
  • BP measurement may frighten children. Prepare the child for the squeezing feeling of the inflated BP cuff by comparing the sensation to an elastic band on a finger or a tight hug.
  • Measure the child's BP before performing anxiety-producing tests or procedures.
  • Assess the BP of a child or adolescent with respect to body size and age.
    • Heavier and taller children have a higher BP than smaller children 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 boys and systolic 124 to 127 mm Hg and diastolic 63 to 74 mm Hg for girls.7
  • Korotkoff sounds are difficult to hear in children because of the low frequency and amplitude. A pediatric stethoscope bell often helps.
  • Though the beginning of the fifth Korotkoff sound indicates diastolic pressure in adults, the fourth Korotkoff (distinct muffling) indicates diastolic pressure in children.

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 Association of Critical-Care Nurses (AACN). (2016). AACN practice alert: Obtaining accurate noninvasive blood pressure measurements in adults. Critical Care Nurse, 36(3), e12-e16. doi:10.4037/ccn2016590 (Level VII)
  2. American Heart Association (AHA). (2017). Understanding blood pressure readings. Retrieved April 24, 2020, from https://www.heart.org/HEARTORG/Conditions/HighBloodPressure/KnowYourNumbers/Understanding-Blood-Pressure-Readings_UCM_301764_Article.jsp#.Wucr9UxFwy9
  3. American Heart Associate (AHA). (2017). Monitoring your blood pressure at home. Retrieved April 24, 2020, from https://www.heart.org/HEARTORG/Conditions/HighBloodPressure/KnowYourNumbers/Monitoring-Your-Blood-Pressure-at-Home_UCM_301874_Article.jsp#.Wuct7ExFwy9
  4. Kallioinen, N. and others. (2017). Sources of inaccuracy in the measurement of adult patients’ resting blood pressure in clinical settings: A systematic review. Journal of Hypertension, 35(3), 421-441. doi:10.1097/HJH.0000000000001197 (Level I)
  5. National Heart, Lung, and Blood Institute (NHLBI). (2012). Expert panel on integrated guidelines for cardiovascular health and risk reduction in children and adolescents. Retrieved April 23, 2020, from https://www.nhlbi.nih.gov/files/docs/peds_guidelines_sum.pdf (classic reference)* (Level VII)
  6. Schimanski, K. and others. (2014). Comparison study of upper arm and forearm non-invasive blood pressures in adult emergency department patients. International Journal of Nursing Studies, 51(12), 1575-1584. doi:10.1016/j.ijnurstu.2014.03.008 (Level IV)
  7. Schroeder, M.L. and others. (2019). Chapter 27: The child with cardiovascular dysfunction. In M.J. Hockenberry, D. Wilson, C.C. Rodgers (Eds.), Wong’s nursing care of infants and children (11th ed., pp. 959-1018). St. Louis: Elsevier.

ADDITIONAL READINGS

Daskalopoulou, S.S. and others. (2015). The 2015 Canadian hypertension education program recommendations for blood pressure measurement, diagnosis, assessment of risk, prevention, and treatment of hypertension. Canadian Journal of Cardiology, 31(5), 549-568. doi:10.1016/j.cjca.2015.02.016 (Level I)

*In these skills, a “classic” reference is a widely cited, standard work of established excellence that significantly affects current practice and may also represent the foundational research for practice.

Adapted from Perry, A.G., Potter, P.A., Ostendorf, W.R. (Eds.). (2018). Clinical nursing skills & techniques (9th ed.). St. Louis: Elsevier.

Elsevier Skills Levels of Evidence

  • Level I - Systematic review of all relevant randomized controlled trials
  • Level II - At least one well-designed randomized controlled trial
  • Level III - Well-designed controlled trials without randomization
  • Level IV - Well-designed case-controlled or cohort studies
  • Level V - Descriptive or qualitative studies
  • Level VI - Single descriptive or qualitative study
  • Level VII - Authority opinion or expert committee reports