title: The significance of base deficit in acidemic term neonates.
abstract: OBJECTIVE
  Much emphasis is placed on the metabolic component of umbilical cord acidemia at birth, with an importance attached to an arterial level of <7.00 accompanied by a base deficit of 12 mmol/L. We hypothesized that in acidemic neonates, the level of arterial base deficit provides no prognostic information beyond that provided by the level of arterial pH.
  
  
  METHODS
  This is a cohort study using a database of deliveries from a major teaching hospital, with additional information from neonatal records. A total of 8797 term, singleton, nonanomalous neonates were identified who had paired and validated cord blood gas analysis. Of these, 520 were acidemic (pH <7.1) and 84 were severely acidemic (pH <7.0). Outcomes examined were encephalopathy grade 2/3 and/or death, Apgar <7 at 5 minutes, neonatal unit admission, and composite outcomes of neurological and systemic involvement. Hierarchical logistic regressions were done using IBM SPSS Statistics 20.0 (Armonk, NY) to assess the predictive value of arterial pH and arterial base deficit.
  
  
  RESULTS
  For each outcome the median pH and base deficit of those neonates affected by the adverse outcome was significantly lower than for those who were unaffected. Hierarchical logistic regressions showed that pH is a significant predictor of all adverse outcomes studied (P < .001 for all outcomes). When base deficit, and then the cross-product, are added to the model, neither add predictive value.
  
  
  CONCLUSIONS
  In acidemic neonates, the metabolic component does not predict those at risk of adverse outcomes once pH is taken into account. The apparently worse outcomes with greater base deficit simply reflect a greater degree of acidemia. The prognostic significance attached to the base deficit among acidemic neonates is questionable.
authors.affiliation: Oxford Fetal Medicine Unit, Women's Center, John Radcliffe Hospital, Oxford, United Kingdom. Electronic address: liv.knutzen@doctors.org.uk.
authors.forename: Liv
authors.initials: L
authors.lastname: Knutzen
authors.affiliation: United Kingdom Medical Careers Research Group, Nuffield Department of Population Health, University of Oxford, Oxford, United Kingdom.
authors.forename: Elena
authors.initials: E
authors.lastname: Svirko
authors.affiliation: Oxford Fetal Medicine Unit, Women's Center, John Radcliffe Hospital, Oxford, United Kingdom.
authors.forename: Lawrence
authors.initials: L
authors.lastname: Impey
mesh_terms: D000138:Acidosis / Q000097:blood / Q000175:diagnosis*; D015331:Cohort Studies; D005312:Fetal Blood / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007231:Infant, Newborn; D016015:Logistic Models; D011237:Predictive Value of Tests; D011379:Prognosis; D011446:Prospective Studies
keywords: adverse neonatal outcome; base deficit; metabolic acidosis; pH; umbilical cord