HYPERAMMONEMIA ASSOCIATED WITH SEVERE PERINATAL ASPHYXIA

Abstract

Although hyperammonemia has been associated with asphyxia in experimental animals, its role and clinical manifestations in the asphyxiated newborn have not been defined. We report 5 new-borns with the following common features: gestational age greater than 40 wk.(4>42 wks.), evidence of fetal distress by severe fetal bradycardia lasting at least 10 min. in addition to the presence of meconium in the amniotic fluid, prolapsed umbilical cord or abruptio placentae. All had severe neonatal asphyxia (1 or 5 min. Apgar<5). CNS irritability and convulsions. Hyper-thermia was found to be associated with ammonia elevations (185-960 mcg/100ml) as was hypertension, respiratory alkalosis and exaggerated cardiac vagal tone. Three infants survived and 2 died. The infants who died were comatose preterminally whereas 2 survivors showed improvement of their neurologic status concomitant with declining ammonia levels. Neurologic improvement was temporally related to exchange transfusion for hyperammonemia in 1 patient. Two survivors showed signs of CNS abnormality at 1 yr. followup. As high ammonia levels are felt to diminish the rate of oxidation in the brain by depletion of ketoglutarate, thereby influencing the Krebs cycle adversely, the accumulation of ammonia in the newborn can only aggravate the neurologic disorder. These infants suggest a clinical syndrome whose symptoms may be related to the ammonia level. The further identification of infants with this syndrome will be necessary to ascertain the role of hyperammonemia in asphyxia and its long term sequelae.

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