Behavioral Protection by Moderate Hypothermia Initiated After Experimental Traumatic Brain Injury

Abstract

The effects of postinjury hypothermia on behavioral outcome following moderate fluid percussion traumatic brain injury (TBI) were examined. In Experiment I, three groups of rats were examined. The first group was normothermic (37.5 degrees C); and hypothermia (30 degrees C) was initiated 15 min and 30 min postinjury in the second and third groups, respectively. Whole body cooling was achieved by ventral ice pack. Cooling of the brain to 30 degrees C was achieved in 25 min and maintained for 60 min. Brain temperature was measured indirectly by a probe in the temporalis muscle. Behavioral outcome was assessed by beam-balance performance, beam-walking performance, and body weight loss measured daily for 5 days after TBI. Both the normothermic group and the 30-min postinjury hypothermic group exhibited significant (p < 0.05) beam-balance and beam-walking deficits on days 1 through 5 after TBI. In contrast, the 15-min postinjury hypothermic group exhibited significant (p < 0.05) beam-walking deficits only on day 1 after TBI and significant (p < 0.05) beam-balance deficits on days 1, 3, and 4 after TBI. In Experiment II, subcortical brain temperature was compared to temporalis muscle temperature in normothermic (37.5 degrees C) and hypothermic (30 degrees C) rats subjected to TBI. In both groups brain temperature tracked within 0.4 degree C of temporalis muscle temperature. These results are similar to post-TBI excitatory receptor antagonist studies and indicate a therapeutic window for moderate hypothermia of less than 30 min after moderate fluid percussion TBI in the rat.

Protection in Animal Models of Brain and Spinal Cord Injury with Mild to Moderate Hypothermia

“…In that study, hypothermia of 338C significantly reduced mortality rates as well as attenuated deficits in beam walking, beam balance, and body weight loss compared to normothermia treatment. In a study by Lyeth et al (1993a), the effects of 1 h post-injury hypothermia (338C) on behavioral outcome was evaluate. Some evidence for improved behavioral outcome was demonstrated with post-traumatic hypothermia.…”

Neurological impairment in rats after subarachnoid hemorrhage—A comparison of functional tests

“…The beam balance task is one of the most widely used techniques to assess deficits of balance and motor function [24,30,31] in models of cerebellar [32], traumatic [33][34][35][36][37], subarachnoid hemorrhage [16,17,19] and global [31] and focal [30,[38][39][40] cerebral damage. The rats are required to balance steadily on a narrow, usually wooden beam of various diameters and shapes.…”

Effects of Moderate Hypothermia on Constitutive and Inducible Nitric Oxide Synthase Activities After Traumatic Brain Injury in the Rat

“…Clifton et al (1991) reported that adult rats treated with transient hypothermia (32°C for 1 h) beginning 5 min after fluidpercussion (F-P) brain injury exhibited better functional outcome (beam walking and beam balance) than normothermic controls. Further work showed that hypothermia also improved behavioral outcome when begun within 15 min, but not 30 min, posttrauma (Lyeth et al, 1993). tex was significantly increased 5 rnin after TBI, returned to control values by 30 min, and was reduced at 1 and 7 days.…”