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

Abstract

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 (400 microg) 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.

Figure 1

Mean values for aortic mean arterial pressure (a–c), cardiac output (d–f) and systemic vascular resistance index (SVRI) (g–i) after L-arginine infusion (10 mg kg⁻¹ min⁻¹), saline infusion, salbutamol inhalation (400 µg), placebo inhalation, nitroglycerin resoriblet (0.25 mg) and placebo resoriblet. Research drug was administrated at measurement time 0 and head-up tilt was performed from 5 to 10 min. *P < 0.05 vs. saline/placebo, anova

Figure 2

Mean values for heart rate (a–c), augmentation index (d–f) and aortic reflection time (g–i) after L-arginine infusion (10 mg kg⁻¹ min⁻¹), saline infusion, salbutamol inhalation (400 µg), placebo inhalation, nitroglycerin resoriblet (0.25 mg) and placebo resoriblet. Research drug was administrated at measurement time 0 and head-up tilt was performed from 5 to 10 min. *P < 0.05 vs. saline/placebo, anova