Effect of Local Hypothermia on the Brain

Jo, S G; Park, S D; Lee, H K; Chu, J W

Abstract

A study of local hypothermia upon the brain was performed in cats. Extravascular local cooling of brain was designed for the experiment using a heat exchanger with a cuff. The cuff was circulated by a cold liquid, saline, at a temperature of 0 degrees +/-1.1 degrees C and rested on brain surface. The thermocouples were inserted and placed at different depths of each 0.5 cm in the brain, and then temperatures were measured at each depth before and during cooling every 10 minutes. The mean precooling temperatures were 32.0 degrees C at brain surface and 37.7 degrees C at 1.5 cm depth in brain. During cooling, temperature lowering was the most marked and evident at extent of 1.0 cm thickness in the subcortical tissue. The lowest mean temperature at each depth throughout the cooling were 18.9 degrees C at surface, 20.0 degrees C at 0.5 cm depth, 22.9 degrees C at 1.0 cm depth and 32.8 degrees C at 1.5 cm depth in the brain. Temperature lowering in the area of brain injured by contusion was more marked and evident in its degree than that in the normal brain, especially within 10 minutes of cooling. Another design of this experiment was an evaluation of the effect of local hypothermia on cerebral edema induced by impaction injury of the brain. Immediately after the intravenous administration of fluorescein, impaction injuries were made on the area of suprasylvian gyri, and then the left part of hemisphere received local hypotehrmia while the counter part of same brain was untreated. These injured brains were removed as specimens at various time intervals after trauma and their coronal sections were examined macroscopically under the ultravilolet illumination. In cooled hemisphere, there were lesser extent of spread and brightness of fluorescein than those in the untreated. Local cerebral cooling in this experimental condition was safe and beneficial in the treatment of trauma-induced vasogenic edema.