Hyperammonemia associated with perinatal asphyxia.

Twelve infants with severe perinatal asphyxia were found to have elevated blood ammonia levels (302 to 960 microgram/100 ml). In the seven survivors, hyperammonemia was associated with CNS irritability, hyperthermia, hypertension, and wide neonatal heart rate oscillations. Follow-up examinations revealed severe neurologic dysfunction in five of seven infants. CNS depression, hyperthermia, hypertension, and a nonreactive, fixed heart rate characterized the infants that died. These findings suggest a clinical entity secondary to perinatal asphyxia whose signs and symptoms may be related to hyperammonemia.