Inhaled β-agonist does not modify sympathetic activity in patients with COPD

Area of Science:

• Pulmonary Medicine
• Cardiovascular Physiology
• Pharmacology

Background:

• Neurohumoral activation is implicated in COPD, linking pulmonary and systemic effects, particularly cardiovascular disease.
• Long-acting inhaled beta-agonists may reduce sympathoexcitation by mitigating hyperinflation via the inflation reflex.

Purpose of the Study:

• To investigate if inhaled salmeterol reduces muscle sympathetic nerve activity (MSNA) in COPD patients.
• To evaluate the effects of salmeterol on sympathoexcitation using microneurography.

Main Methods:

• Continuous measurement of MSNA, heart rate, blood pressure, and respiration.
• Acute administration of placebo followed by salmeterol (50 μg), with subsequent measurements.
• Assessment of lung function, plasma catecholamines, arterial pulse wave velocity, heart rate variability, and baroreflex sensitivity before and after 4 weeks of salmeterol treatment (50 μg twice daily).

Main Results:

• No significant difference in MSNA change between acute salmeterol and placebo administration (-1.96 ± 9.81 vs. -0.65 ± 9.07 bursts/100 heartbeats; p=0.51), despite significant reduction in hyperinflation.
• No changes in MSNA or catecholamines were observed after 4 weeks of treatment.
• Significant increase in heart rate observed both acutely (3.8 ± 4.2 bpm) and after 4 weeks (3.9 ± 4.3 bpm); treatment was safe and well-tolerated.

Conclusions:

• Microneurography revealed no change in MSNA following acute or chronic salmeterol inhalation in COPD patients.
• Despite reducing hyperinflation, salmeterol does not appear to modulate sympathoexcitation in COPD.