Cl. Robertson et al., No long-term benefit from hypothermia after severe traumatic brain injury with secondary insult in rats, CRIT CARE M, 28(9), 2000, pp. 3218-3223
Objectives: To evaluate the effect of application of transient, moderate hy
pothermia on outcome after experimental traumatic brain injury (TBI) with a
secondary hypoxemic insult.
Design: Prospective, randomized study.
Setting: University-based animal research facility. Subjects: Male Sprague-
Dawley rats.
Interventions: All rats were subjected to severe TBI followed by 30 mins of
moderate hypoxemia, associated with mild hypotension. Rats were randomized
to three groups: a) normothermia (37 degrees C +/- 0.5 degrees C); b) imme
diate hypothermia (32 degrees C +/- 0.5 degrees C initiated after trauma, b
efore hypoxemia); and c) delayed hypothermia (32 degrees C +/- 0.5 degrees
C after hypoxemia), The brain temperature was controlled for 4 hrs after TB
I and hypoxemia,
Measurements and Main Results: Animals were evaluated after TBI for motor a
nd cognitive performance using beam balance (days 1-5 after TBI), beam walk
ing (days 1-5 after TBI), and Morris Water Maze (days 14-18 after TBI) asse
ssments, On day 21 after TBI, rats were perfused with paraformaldehyde and
brains were histologically evaluated for lesion volume and hippocampal neur
on counts. All three groups showed marked deficits in beam balance, beam wa
lking, and Morris Water Maze performance. However, these deficits did not d
iffer between groups. There was no difference in lesion volume between grou
ps. All animals had significant hippocampal neuronal loss on the side ipsil
ateral to injury, but this loss was similar between groups.
Conclusions:ln this rat model of severe TBI with secondary insult, moderate
hypothermia for 4 hrs posttrauma failed to improve motor function, cogniti
ve function, lesion volume or hippocampal neuronal survival. Combination th
erapies may be necessary in this difficult setting.