Comparative effects of glyceryl trinitrate and amyl nitrite on pulse wave reflection and augmentation index

Abstract

AimsThe influence of vasodilators on augmentation index (AIx) offers a simple, rapid and noninvasive method of evaluating vascular function. Glyceryl trinitrate (GTN) is widely used as an endothelium-independent vasodilator, although other nitrates that are shorter acting may have advantages in clinical studies. The aim of this study was to compare the effects of two short-acting nitrates, GTN and amyl nitrite, which have differing pharmacodynamic profiles. MethodsTwenty-one healthy volunteers (15 male; mean age 35 years, range 21-56 years) attended on three occasions and received sublingual GTN (0.5 mg for 3 min), inhaled amyl nitrite (0.2 ml inhaled for 30 s), or no treatment in a randomized cross-over design. Haemodynamic responses of AIx, blood pressure and thoracic bioimpedance (heart rate, cardiac index) were assessed by measurement at baseline, every 60 s for the first 5 min, and then every 5 min for a further 55 min. ResultsAIx was reduced by amyl nitrite (peak effect -9 ± 2% at 1 min, P < 0.002) and GTN (peak effect -12 ± 3% at 4 min, P < 0.05). Compared with amyl nitrite, the onset and offset of action of GTN was slower. Amyl nitrite initially increased heart rate by 27 ± 4% ( P < 0.001) and cardiac index by 13 ± 3% ( P < 0.001) whereas GTN had no significant effect ( P > 0.05). Neither agent affected blood pressure. ConclusionsGTN causes a slower and more sustained reduction in AIx than amyl nitrite. Although amyl nitrite causes a more rapid fall and recovery in AIx, it induces a reflex tachycardia that may limit interpretation of the initial (1 min) but not later (2 min) changes in AIx. The prolonged offset of GTN suggests that a sufficient washout period must be included when making repeated measures or when assessing the subsequent effects of other agents.

Effect of a short-acting NO donor on bubble formation from a saturation dive in pigs

“…In a previous study in rats, we demonstrated that NO given immediately before a 45-min air dive effectively reduced bubble formation (18). Because of the fact that NO reduces venous tone through a reduction of the preload and hence reduces CO (6,8), part of the effect on bubble formation could have been caused by a reduction in gas uptake. This is less likely in the present study since we are close to saturation and since our NO donor was given at the end of the bottom phase of the dive.…”

“…The lower arteriovenous O 2 difference in the NO-treated animals (12%) 30 min after the start of decompression indicates on one hand that the O 2 extraction per unit of blood has decreased because perfusion has increased, which is also supported by the increase in heart rates seen in the experimental group. On the other hand, other studies have shown a slight decrease in cardiac output (CO) after administration of the drug, without changing the blood pressure (6). However, the experimental group showed a higher heart rate immediately after nitrate infusion compared with the control group.…”

Exogenous Nitric Oxide and Bubble Formation in Divers

“…Nitroglycerine will reduce peripheral vascular resistance and reduce venous tone, leading to a slight reduction in cardiac output with little change in blood pressure (7). This may influence uptake of inert gas.…”

The potent calcitonin gene‐related peptide receptor antagonist, telcagepant, does not affect nitroglycerin‐induced vasodilation in healthy men

“…This PWF information has become a powerful tool to investigate the cardiovascular response in vivo in humans to disease states and drugs. It was notably shown more reliable in detecting arterial triptan and nitrate-induced vascular effects than the classically used brachial artery diastolic (DBP) and systolic blood pressure (SBP) [25][26][27][28]. High resolution ultrasound allows the real time measurement of changes in the brachial artery diameter (BAD) induced by vasoactive drugs, notably triptans and nitrates [25].…”