Fetal myocardial oxygen and carbohydrate metabolism in sustained hypoxemia in utero

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Abstract
Although there is a great deal of interest regarding the effects of a reduced arterial blood O2 content on fetal cardiovascular and metabolic phenomena, most investigations have been limited by the necessity of acutely imposing the hypoxemic challenge. During these studies on fetal myocardial O2 and carbohydrate consumption 10 lamb fetuses were encountered that had a reduced arterial blood O2 content (< 2,500 .mu.M) but a normal blood pH 2 days after instrumentation. These fetuses were compared with 13 normoxemic fetuses of the same gestational age. Myocardial O2 and carbohydrate consumption were measured in both groups. In the hypoxemic fetuses arterial blood O2 content was 50% lower and the fetal weight was 20% lower; this suggests that these animals suffered chronic intrauterine growth retardation most likely associated with chronic arterial hypoxemia. There was no difference in heart rate or systolic arterial blood pressure between the 2 groups. In the hypoxemic fetuses myocardial blood flow was greater and the arteriovenous difference of O2 across the left ventricular myocardium was lower; myocardial O2 consumption was similar in the 2 groups. Arterial glucose concentration and arteriovenous difference of glucose were lower in the hypoxemic fetuses, but the myocardial glucose consumptions were similar in the 2 groups. Arterial lactate concentration was significantly greater in the hypoxemic fetuses but the arteriovenous difference of lactate was lower and myocardial lactate consumptions were similar in the 2 groups. As the arterial hypoxemia in the lamb fetus was not associated with any significant change in myocardial consumption of O2, glucose or lactate, fetal myocardial metabolism apparently was maintained at its normal aerobic level during a sustained 50% reduction of arterial O2 content.

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