Arterial and venous dilation by nitroprusside and nitroglycerin--is there a difference?

Whole-body arterial and venous dilating properties of nitroprusside and nitroglycerin were compared with each other in 20 adult patients during cardiopulmonary bypass for coronary artery bypass or valvular heart surgery and were compared with simultaneous forearm vascular measurements. Nitroprusside was found to be a more effective whole-body arterial vasodilator and nitroglycerin a better whole-body venous vasodilator when each drug was infused at rates of 1.5 and 2.0 microgram/kg/min. No difference in whole-body vasodilation between the two drugs was found at 1.0 microgram/kg/min. Forearm plethysmography did not distinguish between the two drugs at any dose level.