Measurement of umbilical cord blood gases; effects of delays in collection and analysis

The merit of routine cord blood pH measurement at birth

We searched the literature for mean values of arterial cord blood pH at birth and their lower limits of statistical normality. An arterial cord blood pH, correctly sampled, measured, validated, and interpreted, provides the most objective and sensitive index for fetal hypoxemia during labor. We advise to sample both artery and vein from a clamped segment of the cord within 30 minutes after birth. In accordance with physiological and statistical evidence, it is proposed to classify arterial cord blood pH in three categories: normal (when > 7.11), abnormal (when < 6.99), and borderline (7.00-7.11). An abnormal pH indicates that the fetus was in a state of biochemical decompensation at birth. Disadvantages of routine measurement include extra work load and the lack of a universally agreed definition of normal or abnormal pH. The major advantage of routine measurement is to provide care-givers with immediate feedback on their care during childbirth and an opportunity to learn from that feedback.

Umbilical cord blood gas analysis; a comparison of two simple methods of sample storage

Umbilical cord vessel acid-base analysis is increasingly employed as an end-point in the study of ante-partum and intra-partum care. Delay in processing the sample can results in erroneous values as a result of gaseous diffusion and continuing metabolism. The effect of delay was investigated for samples stored in heparinized syringes at room temperature and simultaneously stored samples in double clamped cord segments. Small, but statistically significant changes were seen for pH, base deficit and PCO2 over 30 min. Storage in the syringe results in the most reliable values for pH and base deficit, whereas the cord segments showed no changes in PO2 and PCO2.