Peripheral fractional oxygen extraction and other measures of tissue oxygenation to guide blood transfusions in preterm infants

The physiological effects of anemia in the preterm infant are complex and the indications for transfusions in preterm infants are controversial. A measure of the adequacy of tissue oxygenation may be a better guide to the need for transfusions than currently used criteria. This article considers 2 measures of tissue oxygenation of preterm infants: 1) The whole blood lactate concentration, and 2) Peripheral fractional oxygen extraction (FOE) by using near infrared spectroscopy. Several studies have shown falls in blood lactate concentration after blood transfusion, but it has been difficult to establish a convincing link between raised lactate concentrations and significant anemia because even anemic infants have lactate concentrations that are within or close to the normal range. Lactate concentrations may be affected by the haematocrit of the blood sample. Peripheral FOE can be measured by using near infrared spectroscopy with partial venous occlusion and has been studied in preterm infants with symptomatic and asymptomatic anaemia. Mean (SD) FOE was significantly higher in symptomatic [0.425 (0.06)] ( P