Nitroglycerine ============== þ NTG may not work well in Asians - Mutations in the aldehyde dehydrogenase-2 (ALDH2) gene that are particularly common in Asian populations can significantly reduce the effectiveness of sublingual nitroglycerin. [J. Clin. Invest. 116:506-511 (2006). doi:10.1172/JCI26564 Mitochondrial aldehyde dehydrogenase-2 (ALDH2) Glu504Lys polymorphism contributes to the variation in efficacy of sublingual nitroglycerin Yifeng Li1,2, Dandan Zhang1, Wei Jin2,3, Chunhong Shao4, Pengrong Yan1, Congjian Xu5, Haihui Sheng2, Yan Liu2,3, Jinde Yu3, Yuying Xie1, Yingnan Zhao1, Daru Lu1, Daniel W. Nebert6, Donald C. Harrison6, Wei Huang2,3 and Li Jin] þ Interaction with Viagra: þ NTG may cause bradycardic arrest: Brandes W, Santiago T, Limacher M Nitroglycerin-induced hypotension, bradycardia, and asystole: report of a case and review of the literature. Clin Cardiol 1990 Oct;13(10):741-4 A 36-year-old man presented with a prolonged history of chest pain, and was given two sublingual nitroglycerin tablets. Subsequently, the patient became hypotensive, bradycardiac, apneic, and lost consciousness. The bradycardia resolved spontaneously. No evidence for acute myocardial infarction or ischemic disease was found. Thirty-four cases reported to date are reviewed, demonstrating that this response appears to be an independent effect of nitroglycerin taken in any form, in patients with and without myocardial infarction and to be unpredictable, especially without evidence of inferior or right ventricular infarction. Careful monitoring is warranted when administering nitroglycerin. þ NTG may worsen V/Q mismatch and cause hypoxemia: Kopman EA, Weygandt GR, Bauer S, Ferguson TB Arterial hypoxemia following the administration of sublingual nitroglycerin. Am Heart J 1978 Oct;96(4):444-7 The effect of nitroglycerin on arterial blood gases and cardiovascular hemodynamics were studied in patients with coronary artery disease. In 13 premedicated patients blood gases and cardiovascular hemodynamics were studied before and 10 minutes after sublingual nitroglycerin (0.6 mg). In eight unpremedicated patients only blood gases were determined before and 10 minutes after sublingual nitroglycerin 0.6 mg. All studies were performed before induction of anesthesia with the patients in the supine position breathing room air. In both groups, arterial PO2 decreased significantly (p less than 0.001); pH and pCO2 did not change. In the 13 patients on which hemodynamic studies were performed, the mean arterial pressure (p less than 0.001), cardiac index (p less than 0.001), central venous pressure (p less than 0.001), pulmonary artery (p less than 0.001) and pulmonary artery wedge pressure (p less than 0.001) decreased. Calculated values for systemic and pulmonary vascular resistance were not significantly altered (p greater than 0.4). This study gives conclusive evidence that nitroglycerin reduces arterial PO2 in most patients with coronary artery disease breathing room air in the supine position. The possible mechanisms and clinical implications are discussed. Weygandt GR, Kopman EA, Ludbrook PA Mechanism of nitroglycerin-induced hypoxemia. Cathet Cardiovasc Diagn 1980;6(4):387-95 We and others have previously demonstrated a consistent significant decline in arterial oxygen tension (PaO2) after sublingual nitroglycerin in premedicated and unpremedicated patients both with and without coronary artery disease and/or obstructive ventilatory disease. Thus, in our 19 patients, PaO2 fell by an average of 17% (12 mm Hg), mean systemic arterial pressure by 19% (17 mm Hg), pulmonary arterial pressure by 38% (6 mm Hg), pulmonary arterial occlusive pressure by 62% (5.3 mm Hg), and cardiac index by 16% (0.37 liter/min/m2) [P less than 0.001 for each] after nitroglycerin. Previous experimental studies suggest that the mechanism for the reduction of PaO2 may be relief of hypoxic pulmonary vasoconstriction with an increase in perfusion to poorly ventilated or nonventilated regions of the lungs. To examine this possibility, pulmonary vasodilatation was precluded by administration of a pulmonary vasoconstrictor (phenylephrine) simultaneously with nitroglycerin in nine patients with coronary artery disease. No significant change was observed in systemic or pulmonary arterial pressure, pulmonary arterial occlusive pressure, or systemic and pulmonary vascular resistance, and PaO2 did not decline. In ten other patients with coronary artery disease, the intrapulmonary right-to-left shunt fraction was determined before and after sublingual nitroglycerin; only a minimal increase in shunt fraction of 1.4% was observed, quantitatively insufficient to account for the observed decline in PaO2, thus excluding a predominant effect of nitroglycerin on nonventilated alveoli as a cause of the hypoxemia. We conclude that the reduction of PaO2 after nitroglycerin administration is attributable to pulmonary vasodilatation with a relative increase in perfusion of poorly ventilated lung units. þ NTG may cause methemoglobinemia: Bojar RM, Rastegar H, Payne DD, Harkness SH, England MR, Stetz JJ, Weiner B, Cleveland RJ Methemoglobinemia from intravenous nitroglycerin: a word of caution. Ann Thorac Surg 1987 Mar;43(3):332-4 The dose of intravenously administered nitroglycerin (IV NTG) used to control ischemic chest pain usually is limited by hypotension from decreased preload. Herein we describe 2 patients who tolerated IV NTG without hemodynamic compromise but in whom severe impairment of blood oxygen content developed from methemoglobinemia noted during coronary bypass surgery. Methemoglobinemia must be suspected if chocolate-brown blood is encountered despite a normal arterial oxygen tension and calculated oxygen saturation. Before a methemoglobin level is available, the extent of hypoxemia can be determined by an oximetric oxygen saturation and therapy begun with intravenous administration of methylene blue. These case reports focus attention on the potential deleterious effects of undetected hypoxemia from methemoglobinemia in patients being stabilized with high-dose IV NTG for urgent cardiac surgery.