Non-invasive measurement of the haemodynamic effects of inhaled salbutamol, intravenous L-arginine and sublingual nitroglycerin

Abstract

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT • Haemodynamic effects of endothelial stimuli induced by salbutamol and L-arginine in humans have been previously studied predominantly at rest in selected vascular beds. • We studied the effects of salbutamol, L-arginine and nitroglycerin on cardiac and vascular function by continuous recording of pulse wave analysis and impedance cardiography both in the supine position and during passive head-up tilt. WHAT THIS STUDY ADDS • The divergent effects of the research drugs in supine position and during head-up tilt indicate that human haemodynamics should also be studied in the upright position. • Since inhaled salbutamol induced more pronounced changes in haemodynamics, it provides a clinically more applicable tool than infused L-arginine for the assessment of endothelial function in humans. AIMS To examine the effects of salbutamol and L-arginine, two compounds acting largely on the endothelium, and the endothelium-independent agent nitroglycerin on blood pressure, arterial compliance, cardiac function and vascular resistance. METHODS Continuous radial pulse wave analysis, whole-body impedance cardiography, and plethysmographic blood pressure from fingers in the supine position and during head-up tilt were recorded in nine healthy subjects. Data were captured before and after L-arginine (10 mg mg-1 min -1) or saline infusion, salbutamol (400g) or placebo inhalation, and sublingual nitroglycerin (0.25 mg) or placebo resoriblet. RESULTS The results of all measurements were comparable before drug administration. The effects of inhaled salbutamol were apparent in the supine position: systemic vascular resistance (-9.2 ± 2.6%) and augmentation index (-4.0 ± 1.5%) decreased, and heart rate (8.6 ± 2.5%) and cardiac output (8.8 ± 3.1%) increased. L-arginine had no clear effects on supine haemodynamics, but during head-up tilt blood pressure was moderately decreased and reduction in aortic reflection time prevented, indicating improved large arterial compliance. Nitroglycerin reduced supine vascular resistance (-6.7 ± 1.8%) and augmentation index (-7.4 ± 1.6%), and increased cardiac output (+9.2 ± 2.7%). During head-up tilt, nitroglycerin increased cardiac output (+10.6 ± 5.6%) and heart rate (+40 ± 7.5%), decreased vascular resistance (-7.8 ± 5.8%) and augmentation index (-18.7 ± 3.2%), and prevented the decrease in aortic reflection time. CONCLUSIONS Inhaled salbutamol predominantly changed supine haemodynamics, whereas the moderate effects of L-arginine were observed during the head-up tilt. In contrast, small doses of nitroglycerin induced major changes in haemodynamics both supine and during the head-up tilt. Altogether, these results emphasize the importance of haemodynamic measurements in both the supine and upright positions. © 2009 The Authors. Journal compilation © 2009 The British Pharmacological Society.