Nitroglycerin-induced hypoxemia does not produce myocardial ischemia.

OBJECTIVE: Nitroglycerin has been the drug of choice for relieving myocardial ischemia for more than a hundred years. Several studies have indicated that a significant reduction in arterial oxygen tension (PaO2) occurs after the administration of sublingual nitroglycerin to patients 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 purpose of this study was to investigate whether nitroglycerin-induced arterial desaturation results in compromised oxidative metabolism of myocardium assessed by coronary sinus lactate concentration and oxygen content in patients with coronary artery disease undergoing coronary artery bypass surgery. PARTICIPANTS: Ten randomly selected patients undergoing coronary bypass surgery. SETTING: All studies were performed at Siyami Ersek Cardiovascular and Thoracic Surgery Center. METHODS: A catheter was inserted into the radial artery to measure blood gases and arterial lactate concentration. After sternotomy, and aortic and venous cannula placement, a coronary sinus catheter was introduced into the 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 micrograms/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 tension decreased significantly. Arterial lactate concentration did not change, coronary sinus lactate concentration decreased. Despite a substantial fall in arterial oxygen tension after administration of nitroglycerin, a significant reduction in coronary sinus lactate concentration occurred. CONCLUSION: Nitroglycerin-induced hypoxia does not compromise oxidative metabolism of myocardium as can be assessed by a concomitant decrease in coronary sinus lactate concentration.

Effects of hypothermia on blood endogenous endotoxin levels during cardiopulmonary bypass.

Endotoxin activates white blood cells and complement and produces a spectrum of clinical syndromes ranging from fever to septic shock. Although production of endogenous endotoxemia during cardiopulmonary bypass (CPB) has recently been reported, the role of hypothermia on endotoxemia is not clear. In this study, we evaluated the effects of moderate (24-28 degrees C) and mild (32-34 degrees C) hypothermia on blood endotoxin levels. The study population consisted of 20 patients who underwent coronary artery bypass grafting (CABG) with CPB. Moderate systemic hypothermia was applied during aortic cross-clamping in ten patients (group 1) and mild hypothermia in the remaining ten patients (group 2). The mean rectal temperatures were 26.8 +/- 1.2 degrees C in group 1 and 33.8 +/- 0.8 degrees C in group 2. The blood samples for endotoxin level measurements were obtained before CPB, during aortic cross-clamping, immediately after the release of the cross-clamp, 20 minutes after the release of the cross-clamp, after CPB, and 2 hours postoperatively. There were no endotoxins in any of the samples before CPB, but it was detected after CPB in both groups. The endotoxin levels were significantly higher in group 1 than in group 2. The present study suggests that when hypothermia is the technique of choice, the deleterious effects of endotoxemia on patients with comorbidity must be considered.

Absent right superior vena cava with hypoplastic proximal inferior vena cava.

We describe the precise preoperative diagnosis of a very rare anomaly that comprises absence of the right superior vena cava, persistence of the left superior vena cava, and proximal hypoplasia of the inferior vena cava draining into the left superior vena cava via the hemiazygos vein associated with a large atrial septal defect and tricuspid regurgitation.

Intermittent aortic cross-clamping and cold crystalloid cardioplegia for low-risk coronary patients.

BACKGROUND: Blood cardioplegic strategies have been shown to increase myocardial oxygen uptake, replenish depleted energy stores, and improve myocardial function and survival in the high-risk subset of patients. However, the superiority of these techniques over intermittent aortic cross-clamping and crystalloid cardioplegia in low-risk patients is still controversial. METHODS: This study consisted of two parts. In the first part, we assessed the results of a recent cohort of 399 consecutive low-risk patients undergoing their first coronary artery bypass grafting between 1993 and 1995 using cold crystalloid cardioplegia (n = 128) and intermittent aortic cross-clamping (n = 271). In the second part of the study, 40 consecutive low-risk patients undergoing elective first time coronary artery bypass grafting were randomly divided into two equal groups. One group received cold crystalloid cardioplegia and the other group had myocardial management with intermittent aortic cross-clamping. The two groups were compared with respect to hemodynamic, biochemical and ultrastructural changes. RESULTS: The overall mortality rate, the perioperative myocardial in the need for intraaortic balloon pumps, and the need for inotropic agents were 0.25%, 1.5%, 1%, and 5.8%, respectively. No significant differences were observed between the groups with respect to these clinically defined end points. CONCLUSIONS: Both intermittent aortic cross-clamping and cold crystalloid cardioplegia techniques may be used safely in low-risk patients undergoing first-time coronary artery bypass grafting.