Value of base deficit

Abstract

We read with interest the article of Knutzen et al1Knutzen L. Svirko E. Impey L. The significance of base deficit in acidemic term neonates.Am J Obstet Gynecol. 2015; 213: 373-377Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar and the accompanying editorials of Drs Cahill and Olofsson in discussing the significance of base deficit (BD) in umbilical cord blood. Together the authors discuss the use of pH, BDblood, BDECF, and lactate as to which represents the best predictor of neonatal morbidity. As noted by the authors, each of these parameters is interdependent and thus highly correlated. The findings are similar to our prior study of newborn acidosis2Victory R. Penava D. Da S.O. Natale R. Richardson B. Umbilical cord pH and base excess values in relation to adverse outcome events for infants delivering at term.Am J Obstet Gynecol. 2004; 191: 2021-2028Abstract Full Text Full Text PDF PubMed Scopus (138) Google Scholar in which the relationship of cord blood values to adverse neonatal outcomes was similar, whether using pH or BE values. Although Knutzen et al1Knutzen L. Svirko E. Impey L. The significance of base deficit in acidemic term neonates.Am J Obstet Gynecol. 2015; 213: 373-377Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar indicated that BD did not add significantly to pH in a hierarchical logistic regression, it would be of interest to know whether pH added significantly to BD in a similar regression analysis. Knutzen states that “it is largely the hydrogen ion concentration that is responsible for cellular damage.” However, respiratory acidosis, which also results in an increase in hydrogen ion concentration, does not appear to produce cell damage. Rather neural cell damage is likely more dependent on deprivation of glucose and oxygen, inflammatory cytokines, and a second-phase generation of oxygen-derived free radicals and excitatory amino acids. Consequently, each of these measures simply serve as a marker of tissue hypoxia rather than the putative injury-inducing factor. In fact, intracellular lactate production retards, not causes, acidosis. Although a more predictive umbilical artery acidosis indicator can aid in directing neonatal care, it is critical that we recognize that the major goal of fetal monitoring during labor and delivery is the prevention of this acidosis, whether quantified by pH, BDblood, BDECF, or lactate. Because of the inverse logarithmic function of pH, it cannot be utilized to time linear changes in fetal acid production in response to hypoxic stress. Knutzen et al1Knutzen L. Svirko E. Impey L. The significance of base deficit in acidemic term neonates.Am J Obstet Gynecol. 2015; 213: 373-377Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar suggests that BD may reflect the duration and severity of the hypoxic insult, findings that are confirmed in our studies in ovine fetuses.3Ross M.G. Jessie M. Amaya K. et al.Correlation of arterial fetal base deficit and lactate changes with severity of variable heart rate decelerations in the near-term ovine fetus.Am J Obstet Gynecol. 2013; 208: 285-286Abstract Full Text Full Text PDF PubMed Scopus (37) Google Scholar Human fetal heart rate patterns may be assessed in real time for quantification of BD changes in response to varying heart rate patterns.4Uccella S. Cromi A. Colombo G. et al.Prediction of fetal base excess values at birth using an algorithm to interpret fetal heart rate tracings: a retrospective validation.BJOG. 2012; 119: 1657-1664Crossref PubMed Scopus (5) Google Scholar The awareness of patterns and rates of BD accumulation as well as BD thresholds for injury can aid in the prospective management of fetal heart rate tracings and potentially prevent adverse outcomes. The significance of base deficit in acidemic term neonatesAmerican Journal of Obstetrics & GynecologyVol. 213Issue 3PreviewMuch 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. Full-Text PDF ReplyAmerican Journal of Obstetrics & GynecologyVol. 214Issue 3PreviewWe thank these authors for their interest in our paper. Full-Text PDF