Clinical application of neurochemical monitoring

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Purpose ; to clinically introduce several biochemical indices, in addition to conventional electrophysiological monitoring, and thereby to detect the derangement of neural metabolic process upon which newly-developed therapies are to be focused.Subjects ; hypoxic encephalopathy, subarachnoid hemorrhage, head trauma (15 patients).Methods ; In hypoxic encephalopathy, oxygen saturation and lactate concentration in the jugular bulb blood were measured to assess the presence of anaerobic oxygen metabolism during relative hypoperfusion phase immediate post-resuscitation. In subarachnoid hemorrhage (SAH) complicated with cerebral vasospasm, the effect of mild hypothermia on excitotoxicity process was evaluated by measuring glutamate (Glu ; HPLC) and nitric oxide (NO2, NO3 ; capillary electrophoresis) levels in cerebrospinal fluid (CSF). In severely head-injured patients, Glu and NOx levels are measured in microdialysis perfusate.Results ; The concentration of lactate was greater in both arter … More ial and venous blood in non-survivors than in survivors. The arteriovenous difference of lactate was, however, not statistically different between survivors and non-survivors. The CSF Glu level was elevated early post-SAH ; Glu was decreased by inducing mild hypothermia (33-35 degree C). The elevated NOx level was not influenced by hypothermia. In a head-injured patient in whom microdialysis probe was inserted, perfusate NOx was increased 1-2 hours in advance to peaks of intracranial pressure changes.Discussion ; Sampling extracellular fluid with a microdialysis technique is superior to venous blood or CSF sampling for obtaining information regarding intracranial metabolic environment, although large molecules can not be dialyzed. Decreases in CSF Glu might represent the inhibitory effect of mild hypothermia upon excitotoxic process. NOx may be included in the development of traumatic brain injury, in which microdialysis method will be a promising real-time monitor for pathophysiologic process. Less