T. Nakamura et al., Influence of rewarming conditions after hypothermia in gerbils with transient forebrain ischemia, J NEUROSURG, 91(1), 1999, pp. 114-120
Object. Recently, several studies have demonstrated that hypothermia has a
beneficial effect on clinical outcome, however, it is difficult to determin
e the appropriate rewarming conditions in clinical use. The pul pose of the
present study was to examine the influence of rewarming conditions in gerb
ils with transient forebrain ischemia.
Methods. Ischemia was induced in the gerbils by a 5-minute bilateral common
carotid artery occlusion, after which the animals were immediately subject
ed to moderate or deep hypothermia. After moderate hypothermia (30.5 degree
s C for 4 hours) the animals were rewarmed over standard, fast. or slow tim
e periods. After deep hypothermia (24 degrees C for 2 hours) the animals we
re rewarmed in a standard, fast, slow, or stepwise manner. Cerebral blood f
low (CBF), extracellular glutamate, and lactate were monitored. Hippocampal
CA1 cell damage was assessed 7 days after induction of ischemia.
In animals treated with moderate hypothermia, the rewarming rate had no inf
luence on the number of surviving neurons. However, fast rewarming from dee
p hypothermia (to 37 degrees C for 30 minutes) failed to provide the neurop
rotective effect of hypothermia. Furthermore, this group showed a poor reco
very of CBF (p < 0.01) and, consequently, an increase in extracellular glut
amate (p < 0.01) and lactate (p < 0.01) in the hippocampus.
Conclusions. The results of this study indicate a transient uncoupling of C
BF and cerebral metabolism during fast rewarming from deep hypothermia, whe
reas slow and stepwise rewarming periods were found to be useful for protec
tion against uncoupling of CBF and cerebral metabolism Juring rewarming.