Effects of haemorrhage on myocardial consumption of oxygen and carbohydrate in fetal sheep in utero.

A previous study has demonstrated that fetal myocardial blood flow decreased during haemorrhage. To assess the effects of a decrease in myocardial blood flow on fetal myocardial oxygenation and metabolism, we measured fetal myocardial consumption of oxygen, glucose, lactate, and pyruvate, at rest and during haemorrhage in fetal sheep in utero. During haemorrhage blood flow to the left ventricular free wall decreased. There were no significant changes in blood oxygen content in the ascending aorta or in arteriovenous oxygen difference across the left ventricular myocardium. There was a decrease in consumption of oxygen by left ventricular free wall. There were no significant changes in blood glucose concentration in the ascending aorta or in the arteriovenous difference of glucose, but glucose consumption by the left ventricular free wall decreased. During haemorrhage blood lactate concentration in the ascending aorta and the arteriovenous difference of lactate increased. Because the decrease in blood flow to the left ventricular free wall was proportional to the increase in arteriovenous difference of lactate, myocardial lactate consumption was unchanged. There were no significant changes in pyruvate flux during haemorrhage. Because both myocardial oxygen consumption and demand decrease during haemorrhage, whereas lactate consumption and inner: outer myocardial blood flow ratio were unchanged, this study shows that fetal myocardial blood flow and oxygen consumption decrease during haemorrhage as a reflection of decreased cardiac work.