[Intracranial temperature measurements in brain death]

Intracranial temperature in many clinical situations can significantly differ from core trunk temperature. Little is known about temperature relations in these locations in brain death.

The oesophageal and rectal temperatures were monitored in 52 comatose (GCS score: 3-9) patients after head trauma or haemorrhagic stroke. Brain temperature was recorded in 44 patients who had been treated surgically. In 8 patients treated conservatively only tympanic temperature was monitored. Signs of brain death appeared in 27 patients.

In patients who were unconscious but without signs of brain death, the brain and trunk temperature run parallel in time, the former being somewhat higher than the latter. The tympanic temperature matched well the temperature of the brain. With brain death symptoms all core temperatures fell by 2 to 4 degrees C during 6 to 12 hours. Most notably, the decrease in brain temperature far exceeded that of trunk temperature. As a result, intracranial temperature established itself as the lowest temperature of the body, being 2 to 4 degrees C lower than core trunk temperature. Tympanic temperature fall was less prominent, thus it no more mirrored brain temperature.

After brain death intracranial temperature dissociates from core trunk temperature and from the tympanic temperature. Brain temperature lower than arterial blood temperature is incompatible with ongoing brain metabolism. So such temperature relations might be specific to brain death.