Correlation of cord blood pH, base excess, and lactate concentration measured with a portable device for identifying fetal acidosis.

Abstract

To determine the effectiveness of portable lactate analyzers in identifying fetal acidosis by correlating arterial and venous lactate values from umbilical cord blood with lactate, pH, and base excess measurements from central laboratory analyzers. We performed a prospective study using arterial and venous cord blood from 52 women with a singleton fetus delivered at term. We evaluated the correlation between the cord blood lactate concentration measured using two of the same portable devices (Lactate Plus, Nova Biomedical) with the result from a central laboratory analyzer. Analyses of the correlation between arterial lactate concentration measured on the portable device with arterial pH and base excess were then performed. We observed a median arterial pH of 7.24 (range 7.05 to 7.35) and a median arterial lactate concentration of 3.7 mmol/L (range 1.7 to 8.8 mmol/L). An excellent correlation was observed between lactate concentrations measured by the two portable devices (arterial R² = 0.98 and venous R² = 0.98), and between the portable device and the central laboratory analyzer (arterial R² = 0.94 and venous R² = 0.95). In our population, the optimal cut-offs to predict a pH < 7.20 or a base excess > -8.0 mmol/L were a lactate concentration of 4.9 mmol/L and 5.3 mmol/L, respectively, according to receiver operator characteristic analysis. With a lactate concentration > 4.9 mmol/L, the portable device had a sensitivity of 82% and a specificity of 90% to identify samples with an arterial pH < 7.20. Cord blood lactate concentration measured with a portable device is a good predictor of cord blood base excess and pH. Future studies should be designed to correlate scalp blood lactate measurements with clinical outcomes.