Experiments on the cerebroprotective effects of local head cooling for cerebral ischemic lesion

1999 Fiscal Year Final Research Report Summary

• Project/Area Number: 09470305
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Cerebral neurosurgery
• Research Institution: University of Occupational and Environmental Health
• Principal Investigator: YOKOTA Akira University of Occupational and Environmental Health, Department of Neurosurgery, Professor, 医学部, 教授 (80040583)
• Co-Investigator(Kenkyū-buntansha): KINOSHTA Yoshimasa University of Occupational and Environmental Health, Department of Neurosurgery, Assistant, 医学部, 助手 (00258617) ; URASAKI Eiichirou University of Occupational and Environmental Health, Department of Neurosurgery, Assistant professor, 医学部, 講師 (20203599)
• Project Period (FY): 1997 – 1999
• Keywords: Hypothermia / Brain temperature / CSF perfusion / Cerebral ischemia / Brain protection

Research Abstract

Effectiveness of systemic hypothermia has been attested in the clinical practice since late 1980's, however, the current prevailing methods systemic hypothermia using heavy equipment and string man powers are too complicated to practice in routine clinical settings. This research examines the effectiveness of selective head cooling therapy for brain protection in comparison with systemic body cooling.
Methods : Adult cats in which the unilateral middle cerebral artery was occluded by transorbital approach were used in this experiment. The temperatures of brain and retum were monitored using copper-constantan thermocouples during general body cooling or selective head cooling. Effectiveness of cerebral protection was examined by MRI.
Results :
1. The general cooling worsened significantly vital signs, but selective head cooling maintained normal vital signs.
2. Selective head cooling gained rapidly lowed parenchymal temperature in the ischemic hemisphere (34-35℃), especially of the cerebral cortex, and showed intraparenchymal temperature gradient. In contrast, the brain temperature in the non-ischemic hemisphere was not affected by selective head coolin (37℃). On the other hand, hypothermia by systemic body cooling demonstrated that the non-ischemic hemisphere temperature slowly lowed in accordance with rectal temperature, but lowering of the ischemic brain temperature laged behind that of rectum and showed much slower time course.
3. MRI study revealed significant decrease of the size of infarction and the extent of brain edema bin the selective head cooling animals in comparison with the control. The selective head cooling showed the same cerebroprotective effect as the systemic hypothermia.
Conclusion : This research results demonstrated that the therapeutic window for acute cerebral infarction, which is thought within 3 - 6 hours after the onset of insult may be widen by simple local hypothermia. Selective head cooling is simple and easy to use for patients outside the therapeutic window to reduce brain edema without serious side effects. Urgent use of local hypothermia may be helpful for the brain protection in case of unexpected breakdown of cerebral circulation during neurosurgical procedure.