Peripheral vasodilators in open heart surgery
The concept of pharmacologically induced vasodilatation has gained a new place in the therapy of inadequate hemodynamic function. Vasodilators are now being used in the treatment of myocardial ischemia and low-output cardiac failure. There is now substantial evidence that myocardial ischemia and refractory heart failure can be improved by appropriate vasodilator therapy. These drugs are being applied in the operating room and in the intensive care units of many institutions. Many of these drugs are familiar to us, such as trimethaphan, but are now being used for a different purpose, not for deliberate hypotension, but instead to improve tissue perfusion and myocardial function. The hemodynamic effects are listed in the Table.
Treatment of myocardial ischemia with vasodilators
In the past 5 years, many studies in man and animals have demonstrated that vasodilators may decrease the extent of infarction as measured by creatine phosphokinase levels, ST-segment changes, and improved systemic hemodynamics. Nitroglycerin has been used in most of these studies, but some authors have used nitroprusside, phentolamine, trimethaphan, and other vasodilators. Even better myocardial preservation has been shown with a combination of a vasodilator, such as nitroglycerin, and an alpha-adrenergic stimulant, such as methoxamine. The alpha-adrenergic agonist is added to maintain the coronary perfusion pressure. Intravenous nitroglycerin is being used by many in preference to other vasodilators because (1) the dose can be easily regulated when given in a dilute intravenous solution; (2) little overshoot and hypotension occur; (3) minimal increases in heart rate occur; (4) nitroglycerin has little known toxicity; . . .