NITROGLYCERIN-INDUCED HYPOXEMIA DOES NOT PRODUCE MYOCARDIAL-ISCHEMIA

Objective: Nitroglycerin has been the drug of choice for relieving myo cardial ischemia for more than a hundred years. Several studies have i ndicated that a significant reduction in arterial oxygen tension (PaO2 ) occurs after the administration of sublingual nitroglycerin to patie nts with coronary artery disease breathing room air. Because available oxygen in arterial blood is reduced, it would be reasonable to assume that oxygen delivery to the myocardium would also be impaired. The pu rpose of this study was to investigate whether nitroglycerin-induced a rterial desaturation results in compromised oxidative metabolism of my ocardium assessed by coronary sinus lactate concentration and oxygen c ontent in patients with coronary artery disease undergoing coronary ar tery bypass surgery. Participants: Ten randomly selected patients unde rgoing coronary bypass surgery. Setting: All studies were performed at Siyami Ersek Cardiovascular and Thoracic Surgery Center. Methods: A c atheter was inserted into the radial artery to measure blood gases and arterial lactate concentration. After sternotomy, and aortic and veno us cannula placement, a coronary sinus catheter was introduced into th e coronary sinus to measure oxygen content and lactate concentration. Control coronary sinus and arterial blood samples were obtained before nitroglycerin infusion. Nitroglycerin was then given in a dose of 2 m u g/kg/min for a period of 5 minutes. At the end of 5 minutes, second samples were obtained from the coronary sinus and arterial catheters, Main Results: It was found that arterial and coronary sinus oxygen ten sion decreased significantly. Arterial lactate concentration did not c hange, coronary sinus lactate concentration decreased, Despite a subst antial fall in arterial oxygen tension after administration of nitrogl ycerin, a significant reduction in coronary sinus lactate concentratio n occurred. Conclusion: Nitroglycerin-induced hypoxia does not comprom ise oxidative metabolism of myocardium as can be assessed by a concomi tant decrease in coronary sinus lactate concentration. Copyright (C) 1 997 by W.B. Saunders Company.