Theoretical and practical significance of parallel assays of serum lactic acid, pH and blood gases in mothers and neonates at birth

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Abstract
After preliminary studies of the lactate measuring method itself for assessment and specification of the blood components in which lactate was measured, maternal arterial (Lm) and cord blood lactate concentrations (La-umbilical artery and Lv-umbilical vein) were assayed in 126 vaginal and 32 abdominal deliveries, using the Lactate Analyzer 640 (Hoffmann La Roche). The results were correlated to fetal outcome (CTG [cardiotocogram] findings, Apgar scores), to duration of the late 2nd stage, and to the usual blood gas and acid-base parameters. There was close correlation between maternal and fetal lactate levels in the absence of fetal distress. Maternal lactate correlated well with duration of late 2nd stage. When the late 2nd stage was short, the lactate concentration gradient from fetus to mother was usually maintained, or only small lactate infusions occurred. The fetal outcome at delivery was not endangered. When the late 2nd stage was long, maternal lactate level was higher, permitting a maternal-fetal infusion acidosis; it appeared after only 6-8 bearing down pains and could produce fetal distress after .apprx. 10 bearing down pains. In the presence of primary fetal distress, fetal lactate levels were already excessive, so that even a long late 2nd stage could not produce infusion acidosis because of the concentration gradient. An increase of maternal arterial lactate levels of .apprx. 1.2 mmol/l always accompanied induction of full anesthesia. Its etiology is discussed. This increase could cause infusion acidosis in primary cesarean sections, but not in sections due to of fetal distress. Even when CTG-patterns remained normal, delivery should be terminated with an operative procedure after 8 bearing down pains at the most and hyperventilation preceding intubation anesthesia for cesarean section should be kept as short as possible to prevent metabolic infusion acidosis.

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