CONTINUOUS NITROGLYCERIN INFUSION AND ITS INFLUENCE ON THE NEUROHUMORAL SYSTEM IN PATIENTS WITH NORMAL LEFT-VENTRICULAR FUNCTION

Patients with congestive heart failure show an attenuation of the init ial hemodynamic nitroglycerin effects after 18-24 h of continuous nitr oglycerin infusion. Two main mechanisms which in part are thought to b e responsible for these tolerance development are 1. the activation of the renin-angiotensin-aldosterone-system and 2. an increase in intrav ascular volume. We investigated the influence of a prolonged 48 h nitr oglycerin infusion (1.5 mu g/kg/min) on neurohumoral counterregulation and plasma volume changes in 14 patients with regular left ventricula r function. During the 48 h nitroglycerin infusion period there was no increase in serum levels of renin [day 1: 49.6 (+/- 48.5) mu U/ml, da y 2: 48.1 (+/- 55.0) mu U/ml, day 3: 41.7 (+/- 53.2) mu U/ml; differen ces not significant] and catecholamines but a significant decrease in aldosterone activity [day 1: 16.5 (+/- 7.6) ng/dl, day 2: 12.0 (+/- 4. 3) ng/dl, day 3: 6.3 (+/- 3.3) ng/dl, p < 0.001 compared to day I and day 3]. Furthermore, there was a significant increase in intravascular volume during the prolonged nitroglycerin infusion. In summary: Patie nts with normal left ventricular function show no activation of the re nin-angiotensin-aldosterone-system during sustained 48 h nitroglycerin infusion. The significant decrease in serum aldosterone is a sensitiv e marker for intravascular volume expansion during prolonged nitroglyc erin infusion.