Accurate Measurements of Oxygen Saturation in Neonates: Paired Arterial and Venous Blood Analyses

Abstract

Purpose The aim of this study was to examine the accuracy of arterial oxygen saturation (Sa o 2) and venous oxygen saturation (Sv o 2) with paired arterial and venous (AV) blood in relation to pulse oximetry saturation (Sp o 2) and oxyhemoglobin (Hb o 2) with fetal hemoglobin determination, and their Hb o 2 dissociation curves. Method Twelve preterm neonates with gestational ages ranging from 27 to 34 weeks at birth, who had umbilical AV lines inserted, were investigated. Analyses were performed with 37 pairs of AV blood samples by using a blood volume safety protocol. Results The mean differences between Sa o 2 and Sv o 2, and AV Hb o 2 were both 6 percent (±6.9 and ±6.7 percent, respectively), with higher Sv o 2 than those reported for adults. Biases were 2.1 ± 0.49 for Sa o 2, 2.0 ± 0.44 for Sv o 2, and 3.1 ± 0.45 for Sp o 2, compared against Hb o 2. With left-shifted Hb o 2 dissociation curves in neonates, for the critical values of oxygen tension values between 50 and 75 millimeters of mercury, Hb o 2 ranged from 92 to 93.4 percent; Sa o 2 ranged from 94.5 to 95.7 percent; and Sp o 2 ranged from 93.7 to 96.3 percent (compared to 85–94 percent in healthy adults). Conclusions In neonates, both left-shifted Hb o 2 dissociation curve and lower AV differences of oxygen saturation measurements indicated low flow of oxygen to the body tissues. These findings demonstrate the importance of accurate assessment of oxygenation statues in neonates.