Relationship between brain temperature, brain chemistry and oxygen delivery after severe human head injury: The effect of mild hypothermia

AbstractWe studied brain temperature and the effect of mild hypothermia in 58 patients after severe head injury (SHI). Brain tissue oxygen tension (ptiO2), carbon dioxide tension (ptiCO2), tissuie pH (pHti) and temperature (Tbr) were measured using a multiparameter probe. Microdialysis was performed to measure glucose, lactate, glutamate, and aspartate in the extracellular fluid. Mild hypothermia (34° – 36°C) was employed in 33 selected patients who had persistent increased intracranial pressure (ICP > 20 mmHg). Mild induced hypothermia decreased brain oxygen significantly from 33 ± 24 mmHg to 30 ± 22 mmHg (p < 0.05). The ptiCO2 (46 ± 8 mmHg) was also significantly lower during mild hypothermia (40.4 ± 4.0 mmHg), p < 0.0001). The pH i increased from 7.13 ± 0.15 to 7.24 ± 0.10 (p < 0.0001) under hypothermic conditions. Induced hypothermia may protect patients from secondary ischemic events by lowering the critical ptiO2 threshold, reducing anaerobic metabolism, and decreasing the release of excitatory amin...