MILD HYPOXEMIA DOES NOT ALTER RED-BLOOD-CELL PRODUCTION IN FETAL SHEEP

1. Fetal sheep at 120 days gestation were fitted with upper and lower body arterial and venous catheters in addition to a flow sensor and oc cluder placed around the aorta below the renal arteries. 2. After 7 da ys of recovery, the occluder was partially inflated to reduce aortic b lood flow to 70 % of control. Blood flow reduction was maintained at t his level for the remainder of the experiment. 3. Blood samples were t aken after 60 min of blood flow reduction and again after 3 or more da ys of blood flow reduction. 4. There was no change in upper body arter ial or venous blood pressure. Lower body arterial blood pressure decre ased, as expected. Arterial P(O2) decreased while packed cell volume a nd haemoglobin concentration increased. There was no change in plasma erythropoietin concentrations or plasma renin activity. 5. While both red cell mass and haemoglobin mass increased during the period of the study, the rate of increase was no different from the rate of blood vo lume increase.