Brain hypothermia induced by cold spinal fluid using a torso cooling pad: theoretical analyses.

Brain hypothermia induced by a temperature reduction of the spinal fluid using a torso-cooling pad is evaluated as a cooling alternative for traumatic injury patients. A theoretical model of the human head is developed to include its tissue structures and their contribution to local heat transfer. The Pennes bioheat equation and finite element analysis are used to predict the temperature distribution in the head region. The energy balance in the cerebrospinal fluid (CSF) layer surrounding the brain during mixing of the CSF and cold spinal fluid is also formulated to predict the CSF temperature reduction. Results show that the presence of cooled CSF around the brain provides mild cooling (approximately 1 degrees C) to the grey matter within 3000 s (50 min) with a cooling capacity of approximately 22 W. However, large temperature variations (approximately 3.5 degrees C) still occur in the grey matter. This approach is more effective during ischemia because it promotes deeper cooling penetration and results in larger temperature reductions; the average grey matter temperature decreases to 35.4 degrees C. Cooling in the white matter is limited and only occurs under ischemic conditions. The non-invasive nature of the torso-cooling pad and its ability to quickly induce hypothermia to the brain tissue are beneficial to traumatic injury patients.