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Use of Hypothermia in Management of Stroke

　　Thorsten Steiner, MD,[10] from the University of Heidelberg, Heidelberg, Germany, discussed hypothermia for stroke management. Body temperature has been studied as a prognostic factor in stroke patients, and it was shown to be an independent risk factor.[11] Additionally, hypothermic patients on admission had a lower mortality and a better outcome. In an animal study by Yanamoto and colleagues,[12] it was shown that hypothermia significantly reduced infarct size in a rat model of stroke. Use of hypothermia aims primarily at neuroprotection and brain edema prevention or reduction. There are 3 phases in inducing hypothermia: the initial stage of cooling, the maintenance stage, and the stage of passive or active rewarming. Hypothermia is graded as mild when body temperature is between 34 and 36 degrees Celsius and deep when the temperature is between 20 and 30 degrees Celsius. Modest hypothermia (ie, temperatures around 35 degrees Celsius) is usually the desired goal.
　　Hypothermia may be applied either locally (head) or systemically (trunk, extremities). It may also be surface hypothermia or systemic. Surface hypothermia studies for stroke patients have shown that high ICP may be successfully decreased, but a rebound increase of ICP occurs in the rewarming period. Additionally, there was a high incidence of thrombocytopenia, cardiac arrhythmias, and pneumonia.[13] Based on these findings, controlled and graduate rewarming was applied in a study by Steiner and coworkers.[14] They were able to control rebound ICP, but the technique was very demanding.[15]
　　Another problem with surface hypothermia is the occurrence of shivering when the body temperature reaches approximately 35.5 degrees Celsius. Meperidine has been used to successfully control shivering.[16] Administering buspirone appears to have an additive effect.[17]
　　Dr. Steiner concluded that in stroke, moderate surface-induced hypothermia is effective in reducing brain edema and elevated ICP. Rewarming should be controlled to avoid rebound ICP rise, and meperidine and buspirone may assist in shivering control. The duration of hypothermia and the target temperatures are still open to discussion.