Multiple interstitial substances measured by microdialysis in patients with subarachnoid hemorrhage

OBJECTIVE: Intracerebral microdialysis is a tool to monitor metabolic distu rbances in the brains of patients with severe head injuries or subarachnoid hemorrhage (SAH). In the search for putative indicators of primary and sec ondary brain damage, we measured multiple metabolites in the dialysates of patients with SAH, to elucidate their significance for the outcomes of the patients as well as their temporal profiles of liberation after the insult. METHODS: Microdialysis probes were placed, with a ventriculostomy catheter for drainage of cerebrospinal fluid, into a frontal lobe of 10 patients wit h aneurysmal SAH, for 4.6 +/- 0.5 days. Amino acids, metabolites of glycoly sis, purines, catecholamines, and nitric oxide oxidation byproducts were me asured by high-performance liquid chromatography. Spearman's correlation co efficient and Student's t test were used to compare the levels of the metab olites with the outcomes of the patients, as assessed using the Glasgow Out come Scale, 3 months after the ictus. RESULTS: For patients with unfavorable outcomes (Glasgow Outcome Scale scor es of 1-3), which were primarily associated with the development of large i nfarctions, dialysate levels of excitatory amino acids increased up to 30-f old, those of lactate up to TO-fold, and those of nitrite up to 5-fold, com pared with normal levels observed for patients with favorable outcomes (Gla sgow Outcome Scale scores of 4 or 5). When average peak concentrations in t he dialysates of patients with favorable and unfavorable outcomes were comp ared, significantly higher levels of excitatory amino acids, taurine, lacta te, and nitrite, but not of purines and catecholamines, were observed for t hose with poor outcomes (P < 0.05). With respect to the temporal profiles o f the average metabolite concentrations, the significantly increased levels of amino acids observed for patients with poor outcomes followed a bipbasi c course, with maxima( concentrations on the first and second days or the s eventh day after the insult (P < 0.01). CONCLUSION: These data confirm the usefulness of excitatory amino acids and lactate as major parameters for neurochemical monitoring for patients thre atened by acute cerebral disorders. Other substances, such as taurine and n itrite, were also demonstrated to be potentially predictive. Release of the se substances into the extracellular fluid of the brain might be particular ly relevant for the development of secondary brain damage after SAW, e.g., infarction or brain swelling.