Effects of the Acute Hypoxia on Coronary Flow and Cardiac metabolism

In 6 light nembutalized dogs, hemodynamic study on coronary fow and some metabolic aspects of the heart were investigated during acute hypoxia which is produced by 10% oxygen inhalation. Coronary flow was determined by Kety and Schmidt s nitrous oxide method. The myocardial extraction or production rates for 02, C02 and glucose were determined by measuring A-V differences of each substrate and coronary flow. Following results were obtained. 1) Arterial oxygen saturation during acute hypoxia , arterial blood pressure, heart rate and respiratory minute volume were increased , respectively .. 2) The coronary flow was found to be 98cc/min/100 gm. heart 土21. 1 in control and increased to mean of 192cc/min/l00gm. heart±28.5 in the hypoxic state. 3) During hypoxia , myocardial 02 eχtraction was relatively constant as compared with contro l. Myocardial C02 production , however , was remarkably decreased. Therefore, R.Q. in myocardium was found to be 0.9 士 O. 25 in control and O. 67 土0/18 in the hypoxia. While, glucose extraction of myocardium showed remarkable increase more than 3 times as compared with control. These facts showed that myocardial metabolism in the hypoxia was more anaerobic than in the contro l