Multiple sampling improves norepinephrine reproducibility in essential hypertension: a comparison with the...

Area of Science:

• Cardiovascular Physiology
• Neuroendocrinology

Background:

• Essential hypertension is characterized by enhanced sympathetic drive.
• Plasma norepinephrine levels are often used to assess sympathetic activity but have limited reproducibility.
• Muscle sympathetic nerve traffic is a more reproducible measure of sympathetic drive.

Purpose of the Study:

• To determine if increasing the number of blood samples for norepinephrine assay improves its reproducibility in essential hypertension.
• To compare the reproducibility of plasma norepinephrine measurements with muscle sympathetic nerve traffic.

Main Methods:

• 14 untreated patients with mild-to-moderate essential hypertension participated.
• Measurements included blood pressure, heart rate, plasma norepinephrine, and muscle sympathetic nerve traffic over two sessions.
• Three norepinephrine samples were collected at 30-minute intervals in each session.

Main Results:

• Muscle sympathetic nerve traffic showed high reproducibility between sessions (r=0.79).
• Single plasma norepinephrine samples lacked significant correlation between sessions (r=0.42).
• Averaging norepinephrine values from the second or third samples significantly improved correlation (r=0.63).

Conclusions:

• Plasma norepinephrine reproducibility in essential hypertension can be substantially improved by analyzing multiple blood samples.
• Using averaged data from serial norepinephrine samples enhances its reliability as an adrenergic marker.