Arteriovenous differences in cord blood gas analysis and the prediction of adverse neonatal outcome.

INTRODUCTION: The aim of this paper was to determine whether arteriovenous differences of pH and pCO2 are useful predictors of adverse neonatal outcome in acidemic neonates.

MATERIAL AND METHODS: An established database of 8759 term, singleton, non-anomalous neonates with validated cord gases and outcomes [Encephalopathy (Grade 2/3), Apgar <7 at five minutes and composite neonatal outcomes of neurological and systemic involvement] was used. Analysis was of the cohort of the 520 acidemic (arterial pH <7.10) neonates. Chi-square tests with odds ratio (OR), 95% CI were calculated for dichotomous cut-offs of differences; hierarchical logistic regression was used to examine the predictive performance over and above arterial pH.

RESULTS: Arteriovenous hydrogen ion concentration ([H+ ion]) differences do not predict neonatal outcomes except low Apgar scores, and large pCO2 differences are associated with worse neonatal outcomes. Nevertheless, neonates with large arteriovenous [H+ ion] and pCO2 differences have lower arterial pH values. Hierarchical regression demonstrates that arteriovenous pCO2 differences do not add predictive value beyond arterial pH and arteriovenous [H+ ion] adds only to the prediction of low Apgar scores.

CONCLUSIONS: Arteriovenous differences of [H+ ion] and pCO2 are not useful independent predictors of adverse neonatal outcomes in acidemic neonates.