Regional brain blood flow and oxygen supply in guinea pig fetuses near term.

To examine brain blood flow and oxygen supply to 14 brain regions in fetal guinea pigs near term, 6 fetuses were catheterized under general anaesthesia of the dam between days 61 and 63 of pregnancy. Fetal arterial blood pressure was measured and a blood sample was taken from the right axillary artery to determine fetal blood gases and acid-base balance. Isotope-labelled microspheres were then injected in a lateral saphenous vein and a reference blood sample was taken from the right axillary artery according to Carter and Gu. Preductal arterial haemoglobin oxygen saturation ranged from 16-33% (26.7 +/- 6.3 mean +/- SD) and pH from 7.08-7.30 (7.20 +/- 0.09); oxygen content varied between 3.0-6.7 ml/dl. Blood flow to the whole brain was 105-258 ml/min per 100 g (167 +/- 58), oxygen supply to the brain was 6.6-10.7 ml O2/min per 100 g (8.0 +/- 1.6). Both regional brain blood flow and oxygen supply were significantly different in the various brain parts. They were highest in the spinal medulla and in other parts of the brain stem and lowest in the cerebrum. Brain blood flow increased significantly with increasing pCO2 and systolic blood pressure and with decreasing haemoglobin oxygen saturation, pH, base excess, and arterial oxygen content. On the other hand, except for the mid portion of the spinal medulla, there were no correlations between blood gas and acid-base balance variables and the oxygen supply to the whole brain or to various regions of the brain.(ABSTRACT TRUNCATED AT 250 WORDS)