Base deficit in acidemic newborns not informative

By David Douglas

NEW YORK (Reuters Health) - In acidemic term neonates, the metabolic component of cord gases does not add prognostic information beyond that of the arterial pH level, according to UK researchers.

"The emphasis we have put on the metabolic component of acidosis at birth may be misplaced," Dr. Liv Knutzen of the University of Oxford told Reuters Health by email.

As reported March 28 online in the American Journal of Obstetrics and Gynecology, Dr. Knutzen and colleagues examined data on 8797 term singleton neonates - including 520 who were acidemic (pH <7.1) and 84 who were severely acidemic (pH <7.0).

The main outcome measures were encephalopathy (grade 2 and 3) and/or death, neonatal unit admission, and an Apgar score <7 at five minutes. Secondary outcomes included a composite neurological adverse outcome, systemic involvement, and a composite of neurological adverse outcome AND systemic involvement.

Base deficit and arterial pH were significantly negatively correlated, demonstrating the association of greater base deficit with lower pH, the authors reported.

For each outcome except for encephalopathy grade 2/3 or death, affected neonates had significantly lower median arterial pH, compared to those who were unaffected. Median base deficits were also consistently higher in affected babies, although rarely to a statistically significant extent.

Hierarchical logistic regression analysis showed that pH was a highly significant predictor of all studied adverse outcomes. Incorporation of base deficit did not increase predictive value.

Dr. Knutzen concluded, "This paper shows that poor short-term neonatal outcome can be predicted from the pH. Base deficit adds no predictive value. It is essentially a surrogate marker of a lower pH."

Commenting by email, Dr. Antoniya Georgieva, scientific director of the Oxford Center for Fetal Monitoring Technologies, told Reuters Health, "I congratulate the authors on this in-depth analysis because our understanding of the pathophysiology of asphyxia in labor is still limited. Such investigations of biomarkers or measures that can link the labor experience to the subsequent neonatal compromise are vital for future progress."

"This study fits very well into the context of my own previous work," Dr. Georgieva added. (Here: http://bit.ly/1EFWFeA) "We used a large cohort from Oxford to show that arterial pH alone is a better marker than base deficit alone for the risk of neonatal compromise. Knutzen et al have now focused specifically on acidemic infants, using a much 'cleaner' dataset (with more precise data validation) and conclude that base deficit has no added value when pH is already taken into account. The two studies complement each other well and make the picture more complete."

The authors reported no funding or disclosures.

SOURCE: http://bit.ly/1Is8eb3

Am J Obstet Gynecol 2015.

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