Extracellular Glutamate in the Brains of Children with Severe Head Injuries: A Pilot Microdialysis Study

OBJECTIVE: To determine, using a microdialysis technique, the extracellular levels of glutamate and non-transmitter amino acids in the brain of children with severe head injuries. METHODS: A microdialysis probe was inserted along side the intracranial pressure (ICP) bolt in 9 children (age range 2-14 years) with severe head injuries (Glasgow coma scale30 micro M). No correlation with outcome at discharge was demonstrated. Structural amino acid levels did not follow the glutamate fluctuations. Low glutamine/glutamate ratio was associated with increased morbidity, while a high ratio was associated with clinical improvement. Glutamate metabolism may have a more significant role in the pathophysiology of paediatric head injury than has already been recognised.