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49: Arterial cord blood (ACB) lactate correlates with brain lactate in non-encephalopathic term infants

      Objective

      Brain lactate is a biomarker for injury in infants with HIE. Recent data indicate ACB lactate may be superior to pH and base excess as a marker of neonatal morbidity risk. Advanced magnetic resonance imaging (MRI) allows detection of brain lactate without need for pathologic samples. Combining these technologies, we aimed to correlate ACB lactate with brain lactate in non-encephalopathic term infants.

      Study Design

      A nested case-control study was performed within an on-going prospective cohort of over 8000 consecutive singleton term (≥ 37 weeks) non-anomalous infants. Neonates underwent cerebral MRI within the first 72 hours of life. Cases (ACB pH ≤ 7.10) were gender- and race-matched 1:3 to controls (ACB pH > 7.10). MR spectroscopy (MRS) was used to detect qualitative, and if present quantitative, lactate in the left thalamus by a single technician, blind to ACB lactate and clinical measures. The lactate peak was identified as a doublet (2 methyl groups) at 1.33 ppm resonance frequency. Integral values for MRS lactate, as well as N-acetyl aspartate (NAA) for normalization, were calculated. The ACB lactate was measured as part of the primary cord gas analysis. Linear regression was used to estimate the association between incremental change in ACB lactate and brain lactate, both directly and as a ratio with NAA, adjusting for mode of delivery, nulliparity, and maternal fever.

      Results

      Of 178 infants who underwent MRI with spectral sequencing, 3 studies were too poor to interpret. 52 of the remaining 175 infants had detectable brain lactate. The 52 infants with MRI lactate peaks had ACB lactate values of 1.6 - 11.4 mmol/L. Among these infants, for every 1.0mmol/L increase in ACB lactate, there was an increase in MRI lactate of 0.02, which remained significant even when corrected for NAA.

      Conclusion

      MR spectroscopy measured brain lactate is significantly correlated with ACB lactate in non-anomalous term infants, which may help to explain the observed association between ACB lactate and neurologic morbidity.
      Tabled 1
      Figure thumbnail fx1
      *b represents the change in MRI lactate level per unit change in arterial blood gas lactate.