How should blood pressure (BP) be measured in hemodialysis patients, in the arm or leg?

Blood Pressure Measurement in Hemodialysis Patients: Arm vs. Leg

Blood pressure should be measured in the arm whenever possible in hemodialysis patients, with leg measurements reserved only for patients who have undergone multiple surgeries for vascular accesses in both arms making arm measurements technically impossible. 1

Preferred Approach to BP Measurement in Hemodialysis

Standard Arm Measurement

• Measure BP in the arm without vascular access
• Patient should be seated quietly for at least 5 minutes before measurement
• Feet should be on the floor and arm supported at heart level
• Measure BP at least 5 minutes before dialysis access needles are placed
• Use appropriate cuff size (bladder should encircle at least 80% of the arm)
• Use the auscultatory method with disappearance of Korotkoff sounds defining diastolic BP
• Measure both before and after dialysis 1

When to Consider Leg Measurement

Leg BP measurement should only be used when:

• Patient has undergone multiple surgeries for vascular accesses in both arms
• BP is technically not measurable in either arm 1

Important Considerations for Leg BP Measurement

When leg measurement is necessary:

• Healthcare professionals must be properly trained in this technique
• Use appropriate (larger) cuff size for the thigh/leg
• Measure BP only in the supine position
• Be aware that leg BP values are not equivalent to arm BP values:
  • Systolic BP and pulse pressure are amplified from the aorta toward peripheral arteries
  • In young subjects, ankle pressure can be higher than arm pressure by as much as 30%
  • In older subjects, ankle and arm pressures tend to be more similar
  • The reference value of 140 mmHg for systolic BP is valid only for brachial pressure
  • Reference values for lower limb BP are essentially unknown 1

Timing and Frequency of BP Measurement

• Measure BP both before and after dialysis sessions
• Neither pre-dialysis nor post-dialysis BP alone is a particularly good predictor of interdialytic BP
• Consider the following when possible:
  • Ambulatory BP monitoring (ABPM) provides the most accurate assessment
  • Home BP monitoring is a good alternative when ABPM is not feasible
  • A composite of BP measurements over 1-2 weeks rather than isolated readings should guide therapy 2

Pitfalls to Avoid

• Avoid measuring BP immediately after access needles are placed (can cause stress)
• Avoid measuring BP within 30 minutes of caffeine consumption, exercise, or smoking
• Be aware that automated BP devices may overestimate BP by 14/7 mmHg before dialysis 1
• Poor measurement technique can lead to significant underestimation of BP (by approximately 6 mmHg for both systolic and diastolic readings) 3
• In patients with severe vascular calcifications, indirect BP measurements may be inaccurate 1

Special Considerations

• For patients with diabetes or cardiomyopathy, more careful BP monitoring may be needed as they are more prone to hemodynamic instability 4
• Consider the impact of antihypertensive medications on BP readings, especially if taken shortly before dialysis 4
• Be aware that BP control targets are achieved in a decreasing percentage of hemodialysis patients over time, highlighting the importance of accurate measurement 5

By following these guidelines, clinicians can ensure accurate BP measurement in hemodialysis patients, which is essential for proper diagnosis and management of hypertension in this high-risk population.