BACKGROUND: Cardiopulmonary bypass has often been applied to revive victims of cold water drowning. The success of resuscitative efforts in patients who have sustained severe hypothermia is largely determined by neurologic outcomes. Measurement of Fos, the protein product of the immediate-early gene c-fos, is a marker of cerebral injury. STUDY DESIGN: Twenty-eight infant lambs were sedated and ventilated. Group 1 lambs were immersed in a cold water bath for 2 hours (17.3 ± 2.7°C). Group 2 lambs were placed on normothermic cardiopulmonary bypass for 2 hours (37.7° ± 0.7°C). Group 3 lambs were immersed in a cold water bath for 2 hours (17.6° ± 2.4°C), and then rewarmed for a period of 2 hours on cardiopulmonary bypass (37.0° ± 0.6°C). The lambs were euthanized and immunohistochemical analysis for neuronal Fos was performed. RESULTS: There was significant induction of Fos-labeled nuclear profiles (cells/1,130 μm2) in group 3 in the hippocampal regions and dentate gyrus compared with groups 1 and 2 (p < 0.001). CONCLUSION: Isolated exposure to either hypothermia or cardiopulmonary bypass results in minimal expression of neuronal Fos; the significant induction of Fos in the group 3 animals may represent an ischemic-reperfusion phenomenon. Modifications of rewarming techniques that minimize Fos expression may improve neurologic outcomes in victims of cold water drowning.
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