Effect Of Increased Oxygen-Hemoglobin Affinity On Cardiac Tissue Oxygen Unloading Of Lambs Following Inhalation Of Carbon-Monoxide (Co)

Previous studies in newborn lambs have shown that a decrease in whole blood oxygen affinity results in an increased coronary sinus PO2 and in an decreased cardiac output for the same oxygen consumption (VO2). The present studies were designed to investigate the response of the heart to an acute shift of the oxyhemoglobin equilibrium curve to the left. Polyvinyl catheters were placed chronically in the right ventricle, carotid artery and coronary sinus of 4-8 wks. old lambs by direct visualization during thoracotomy. Measurements of blood [HbO2] and [HbCO] % saturation, PO2, PCO2, pH and P50 in these vessels and total VO2 were obtained before and after blood [HbCO2] was raised 12-15 % by CO inhalation. Arteriovenous oxygen content difference (AVD) and cardiac output were calculated. In the 11 animals studied mean coronary sinus Fog decreased from 24 to 17 mmHg, AVD across the heart decreased from 7.7 to 6.1 ml O2/100 ml blood and the total cardiac output increased from 165 to 250 ml/m min. x kg. These data suggest that by increasing blood O2 affinity there may have been an increase in coronary blood flow presumably as a secondary increase to myocardial hypoxia.