INTRACEREBRAL MICRODIALYSIS OF GLUTAMATE AND ASPARTATE IN 2 VASCULAR TERRITORIES AFTER ANEURYSMAL SUBARACHNOID HEMORRHAGE

CEREBRAL ISCHEMIA ASSOCIATED with subarachnoid hemorrhage may have sev ere consequences for neuronal functioning. The excitatory amino acid n eurotransmitters glutamate and aspartate have been shown to be of part icular importance for ischemia and ischemic neuronal damage. For seven patients who underwent early surgery for ruptured intracranial aneury sms, intracerebral microdialysis of glutamate and aspartate was perfor med to monitor local metabolic changes in the medial temporal (all sev en patients) and subfrontal cortex (Patients 4 through 7). Samples wer e collected every 30 or 60 minutes, using an autosampler. The results show that extracellular glutamate and aspartate concentrations can ris e to very high levels after surgery for subarachnoid hemorrhage and an eurysm. These increased levels of excitatory amino acids correlated we ll with the clinical course and neurological symptoms of the patients. Simultaneous sampling from two vascular territories (middle cerebral artery and anterior cerebral artery) also showed that a rise in extrac ellular glutamate and aspartate in one territory is not necessarily pa rallel with a rise in the other. The application of the microdialysis technique with an on-line assay system might be of value in the future for continuous monitoring of ischemic events to optimize treatment wi th, for example, blockers of glutamatergic neurotransmission.