Systemic hemodynamics changes following nitroglycerin intravenous injection

In acute experiments on the mongrel anesthetized cats it was shown, that intravenous injection of nitroglycerine causes the decrease of arterial pressure and total peripheral resistance, whereas heart rate, cardiac output and venous return did not change significantly. In that case, the superior vena cava flow increases, and inferior vena cava flow decreases. The shifts of the superior vena cava flow begin and come to an end earlier in comparison with the changes of the inferior vena cava flow. The right atrial pressure following nitroglycerine injection can be reduced or increased. The dynamics of restoration of the right atrial pressure to an initial level is faster than the changes of the venous return. In animals with the decreasing of right atrial pressure the inferior vena cava flow decreased practically twice more than in animals, where the right atrial pressure increased. Superior vena cava flow in both groups of animals was increased in the same level, while the myocardial contractility - decreased. Thus we concluded, that the character of changes of right atrial pressure during the time of its maximal shifts depends from the interrelation of the superior and inferior vena cava flows and does not depend from the venous return.