Tissue oxygen delivery in lambs: effect of postnatal age and acute hypoxemia

Organ tissue arterial oxygen delivery in relation to postnatal age and acute hypoxemia (arterial pO2 34 +/- 5 Torr for 30 min) was studied in chronically catheterized, non anesthetized lambs 2-38 days of age. Baseline tissue oxygen delivery to heart and skeletal muscle correlated significantly with postnatal age. Acute hypoxemia induced significantly decreased oxygen delivery to kidney, spleen, ileum, jejunum and skeletal muscle without significant relation to postnatal age. Hypoxemia also induced increased arterial oxygen capacity and hemoglobin concentration which correlated significantly with postnatal age. These results suggest that baseline organ tissue oxygen delivery and response to hypoxemia remain constant during early postnatal maturation. Furthermore, hypoxemia may induce an apparent shift of fluid from the intravascular compartment which is greater in older lambs.