Excitatory amino acids and magnesium sulfate in neonatal asphyxia

Objective. The excitatory amino acids (EAA); glutamate and aspartate are released into the cerebrospinal fluids (CSF) of asphyxiated newborns. The objectives of this study were: (a) to examine the relation of the concentration of EAA in the CSF with the degree of brain injury, (b) To determine the time of the release of these EAA into the CSF, and (c) to detect the effect of magnesium sulfate (MgSO4) on their levels. Designs and methods. A randomized controlled trial was conducted on 47 full term asphyxiated newborns. Twenty three infants received an intravenous 10% solution of MgSO4 at a dose of 250 mg/kg within the first 24 h of life while the other 24 newborns received isotonic saline (0.9%) of an equal volume. Levels of glutamate and aspartate were measured before and 72 h after giving the trial solution. Results. In the study population (n=47) both glutamate and aspartate were significantly elevated in infants with higher grades of HIE compared to those with lower grades (P=0.013 and 0.031, respectively). Compared to baseline level, glutamate decreased significantly over time in placebo group (-8.28±14.26, P=0.025) and in MgSO4 group (-14.39±18.72, P=0.005). Glutamate concentration did not differ between groups when measured at baseline (29.26±16.31 vs. 31.27±22.62, P=0.82) and at 72 h (19.28±15.63 vs. 19.6±16.54, P=0.87). The change in aspartate concentration over time was not significant in placebo group (-0.45±1.96, P=0.34) or in MgSO4 group (-0.7±3.19, P=0.37). Aspartate did not differ between groups when measured at baseline (3.52±2.4 vs. 3.92±2.59, P=0.49) or at 72 h (2.79±1.24 vs. 3.05±2.48, P=0.92). Conclusions. The EAA; glutamate and aspartate are released in the CSF of asphyxiated newborns immediately after birth and declined by 72 h. Their initial concentrations correlated with the severity of HIE. Postnatal administration of MgSO4 did not alter the levels of these 2 EAA. © 2005 Elsevier B.V. All rights reserved.