PULMONARY VASCULAR EFFECTS OF TRINITROGLYCERIN AND ISOSORBIDE DINITRATE AFTER CARDIOPULMONARY BYPASS

We have compared the systemic and right ventricular haemodynamic effec ts of trinitroglycerin (TNG) and isosorbide dinitrate (ISDN) in patien ts recovering from coronary artery bypass grafting. Each of the 16 pat ients was given increasing iv. doses of the two nitrates in a random o rder and double blind fashion until the target of a 25% decrease in me an pulmonary artery pressure (MPAP) was achieved. Total doses of TNG 9 (6-12) mug kg-1 (mean, 95% confidence interval) and ISDN 148 (76-220) mug kg-1 were given during infusions of 22 (18-25) min and 34 (28-41) min duration, respectively. The target decrease in MPAP was produced with infusion rates of TNG 0.5 (0.4-0.7) mug kg-1 min-1 and ISDN 5.8 ( 4.1-7.5) mug kg-1 min-1. These doses produced similar acute decreases in MPAP and similar effects on pulmonary and systemic vascular resista nces and systemic and right ventricular haemodynamic variables. We con clude that TNG is more than 10 times as potent as ISDN in its acute ha emodynamic effects in cardiac surgical patients in the immediate posto perative period. Both nitrates have relatively greater effect on the p ulmonary than the systemic vasculature.