Comparison of brain temperature with bladder and rectal temperatures in adults with severe head injury

The purpose of this study was to compare brain temperature (Tbr) with conventional indicators of core body temperature (i.e., rectal temperature [Tre] and bladder temperature [Tbl]), in adults with severe head injury.

The relationships between Tbr and Tbl and between Tbr and Tre are described in terms of differences in temperature in eight patients with severe head injury.

Brain tissue temperature was measured every minute, with a thermocouple embedded 2 cm from the tip of a ventriculostomy catheter used to measure intracranial pressure. Tbl was measured with a thermistor embedded in a bladder catheter, and Tre was measured with a thermistor in a rectal probe.

Tbr was usually greater than Tbl and Tre. The average difference between Tbr and Tbl for each patient ranged from 0.32 to 1.9 degrees C, with standard deviations of the difference ranging from 0.30 to 0.80 degrees C. The average difference between Tbr and Tre for each patient ranged from 0.1 to 2.0 degrees C, with standard deviations of the difference ranging from 0.32 to 1.08 degrees C. In the majority of patients, the differences (Tbr - Tbl and Tbr - Tre) were greater at temperatures outside of the normal temperature range (Tbr < or =36 degrees C and >38 degrees C).

Tbl and Tre often underrepresent Tbr after traumatic brain injury, particularly when the patient is hypo- or hyperthermic.