Neurochemical monitoring in the management of severe head-injured patients with hypothermia.

The neuroprotective action and effect of hypothermia on the neurochemical system is not well understood. The present study was performed using six patients with GCS scores of 5 or less to clarify the relationship between monitored brain temperature, intracranial pressure (ICP), cerebral perfusion pressure (CPP) and oxygen saturation of the jugular venous blood (SjO2). Changes in concentration of excitatory amino acids, glutamate (GLU) and aspartate (ASP), and NO2 were studied using intracerebral microdialysis as well as in jugular venous blood and cerebrospinal fluid (CSF). Changes in brain temperature, CPP and SjO2 resulting from hypothermia and brain death associated with markedly higher concentrations of and fluctuations in the concentrations of GLU, ASP and NO2 were observed in the dialysate than in the jugular venous blood or CSF. Hypothermic treatment significantly reduces excitatory amino acid and NO2 concentrations, a finding which was associated with an improvement in CPP and SjO2. Measurement of GLU and ASP using intracerebral microdialysis is a clinically useful method for clarifying abnormal neurochemical events associated with severe head injury and for evaluating the effects of hypothermia.