A Comparison of Nitroglycerin and Nitroprusside: I. Treatment of Postoperative Hypertension

Abstract

Nitroglycerin improves perfusion to ischemic myocardial regions and therefore has theoretical advantages over sodium nitroprusside to treat hypertension (mean arterial pressure [MAP] greater than 95 mm Hg) following coronary bypass operation. Thirty-three hypertensive patients were randomized to an initial infusion of either nitroglycerin or nitroprusside in a crossover trial designed to reduce MAP to 85 mm Hg. Thermodilution cardiac output measurements permitted calculation of left ventricular stroke work index (LVSWI), and nuclear ventriculograms permitted estimation of left ventricular ejection fraction, left ventricular end-diastolic volume index (LVEDVI), and left ventricular end-systolic volume index (LVESVI). Coronary sinus blood flow was measured by the continuous thermodilution technique, and arterial and coronary sinus lactate measurements permitted calculation of myocardial lactate flux (MV˙L). Both nitroglycerin and nitroprusside reduced MAP (− 25 ± 12 mm Hg and − 20 ± 10 mm Hg, respectively; not significant [NS]). Nitroglycerin reduced LVSWI more than did nitroprusside (−15 ± 13 gm-m/m 2 and −7 ± 9 gm-m/m 2, respectively; p < 0.01). Both agents increased left ventricular ejection fraction (nitroglycerin, +8 ± 8%, and nitroprusside, + 10 ± 7%; NS), and decreased LVEDVI (-20 ± 22 ml/m 2 and −11 ± 17 ml/m 2, respectively; NS) and LVESVI (−13 ± 14 ml/m 2 and −10 ± 12 ml/m 2, respectively; NS). Coronary sinus blood flow decreased with both drugs (NS), but MV˙L increased with nitroglycerin (+ 0.02 ± 0.14 mmol/min) and decreased with nitroprusside (-0.02 ± 0.02 mmol/min) ( p < 0.05). Both medications controlled hypertension following coronary bypass grafting, but only nitroglycerin improved myocardial metabolism. While either nitroglycerin or nitroprusside may be used after routine operation, nitroglycerin is preferred for patients with suspected perioperative ischemia.