The effects of an intravenous infusion of isosorbide dinitrate during open heart surgery

Recent awareness of right ventricular dysfunction during open heart surgery has focused attention upon the importance of protection of the right ventricle and control of right ventricular afterload for the maintenance of the cardiac output. Conventional doses of systemic vasodilators, when used to reduce pulmonary vascular resistance, may produce systemic hypotension, reduce coronary arterial perfusion and even lower the cardiac output. A study of the effects of bolus intravenous isosorbide dinitrate during open heart surgery showed that following cardiopulmonary bypass intravenous isosorbide dinitrate produced highly significant falls in pulmonary artery pressure and induced active pulmonary vasodilatation without systemic side-effects or reduced atrial filling procedures. Treatment with intravenous isosorbide dinitrate by low-dose infusion during and after open heart surgery significantly lowered mean pulmonary artery pressure and pulmonary vascular resistance (P less than 0.001) in patients receiving no sympathomimetic drug support. The results suggest that possibly the effect of low-dose isosorbide dinitrate following cardiopulmonary by-pass is exerted predominantly on the right ventricular afterload if systemic arterial pressure is not elevated. This may have applications in the management of pulmonary hypertension and of acute right heart failure following cardiac surgery.