Vasodilator properties of nitroglycerin and isosorbide dinitrate during cardiopulmonary bypass

In a placebo-controlled trial, we have studied the vasodilator properties of bolus doses of nitroglycerin (TNG) and isosorbide dinitrate (ISDN) in 32 patients during cardiopulmonary bypass with a constant pump flow. Blood volume of the venous reservoir and mean arterial pressure were recorded for 10 min after drug administration to detect changes in venous capacitance and arteriolar resistance, respectively. The venous capacitance-increasing effects of TNG 200 micrograms and ISDN 1,600 micrograms were initially identical and significant at 2 and 3 min after the bolus. Thereafter, the effect of TNG began to decline, while that of ISDN remained significant until the end of the study. TNG 200 micrograms decreased arterial pressure slightly more than ISDN 1,600 micrograms, but the effect of both drugs lasted for only 1-2 min. TNG and ISDN were equipotent in increasing venous capacitance when administered in a bolus dose ratio of 1:8 during CPB, but the venodilator effect of ISDN lasted longer than that of TNG. The duration of the arteriolar dilator effect was very short with both drugs.