Accurate measurements of oxygen saturation in neonates: Paired arterial and venous blood analyses

Purpose: The aim of this study was to examine the accuracy of arterial oxygen saturation (SaO₂) and venous oxygen saturation (SvO₂) with paired arterial and venous (AV) blood in relation to pulse oximetry saturation (SpO₂) and oxyhemoglobin (HbO₂) with fetal hemoglobin determination, and their HbO₂ 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 SaO₂ and SvO₂, and AV HbO₂ were both 6 percent (±6.9 and ±6.7 percent, respectively), with higher SvO₂ than those reported for adults. Biases were 2.1 ± 0.49 for SaO₂, 2.0 ± 0.44 for SvO₂, and 3.1 ± 0.45 for SpO₂, compared against HbO₂. With left-shifted HbO₂ dissociation curves in neonates, for the critical values of oxygen tension values between 50 and 75 millimeters of mercury, HbO₂ ranged from 92 to 93.4 percent; SaO₂ ranged from 94.5 to 95.7 percent; and SpO₂ ranged from 93.7 to 96.3 percent (compared to 85-94 percent in healthy adults). Conclusions: In neonates, both left-shifted HbO₂ 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.