Masui. The Japanese journal of anesthesiology
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We investigated the effects of increased arterial carbon dioxide (PaCO2 not equal to 60 mmHg) on myocardial tissue oxygen tension and metabolism in anesthetized dogs. Ten adult mongrel dogs weighing 15.3 +/- 4.1 kg were anesthetized with 0.5% isoflurane in 50% oxygen and ventilated mechanically to maintain normocapnia. After thoracotomy, regional myocardial tissue PO2 was measured using a monopolar polarographic needle electrode inserted in the myocardium. ⋯ As a result, the coronary blood flow and myocardial oxygen tension increased during hypercapnia. The myocardial lactate extraction and coronary venous lactate were unchanged and excess lactate was kept below zero, although coronary venous L/P ratio increased during hypercapnia. These results indicate that hypercapnia (PaCO2 not equal to 60 mmHg) increases coronary blood flow and myocardial oxygen tension, while myocardial aerobic metabolism is not impaired under hypercapnia.
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To evaluate effects of stellate ganglion block (SGB) on coronary circulation under coronary occlusion, the changes in cardiac function and tissue blood flow in the myocardial ischemic area after right and left SGB were observed in the dogs. Tissue blood flow in the myocardial ischemic area measured with laser doppler flowmeter showed no significant change after right or left SGB. ⋯ On the other hand, in the left SGB group, heart rate, circumflex branch blood flow and rate pressure product showed no significant changes, while end-diastolic pressure and myocardial oxygen extraction rate increased significantly (P < 0.05). These data suggest that although right SGB might be useful to improve the oxygen demand-supply relation, left SGB does not improve the oxygen demand-supply relation and might increase the risk of myocardial ischemia.