NEUROCHEMICAL MONITORING USING INTRACEREBRAL MICRODIALYSIS IN PATIENTS WITH SUBARACHNOID HEMORRHAGE

The authors have developed a method for routine monitoring of disturba nces in brain energy metabolism and extracellular levels of excitatory amino acids using intracerebral microdialysis in 10 patients with sub arachnoid hemorrhage. Microdialysis was conducted for periods ranging from 6 to 11 days after ictus. Altogether, 16,054 chemical analyses fr om 1647 dialysate samples were performed. Concentrations of the energy -related substances lactate, pyruvate, glucose, and hypoxanthine were measured, and the lactate/pyruvate ratio was calculated. The excitator y amino acids glutamate and aspartate were measured. The microdialysis data were matched with computerized tomography findings, clinical cou rse, and outcome. The results support the concepts that microdialysis is a promising tool for chemical monitoring of the human brain and tha t extracellular fluid levels of lactate. lactate/pyruvate ratio, gluco se, hypoxanthine, and glutamate are useful markers of disturbances in brain energy metabolism in neurointensive care patients. These results have generated a working hypothesis that the pattern of these extrace llular markers may help differentiate between various causes of energy perturbations, such as hypoxia and different degrees of ischemia. The correlation between the dialysate levels of excitatory amino acids an d outcome supports the concept of glutamate receptor overactivation in acute human brain injury.