Abstract: Objective To study the therapeutic effects of mild hypothermia on the cerebral edema at differentreperfusion time window after transient ischemia in rats.Methods Ninety-six male Sprague Dawley rats were randomly divided into mild hypothermiagroup and normothermia group. Middle cerebral artery occlusion and reperfusion (MCAO/R)were achieved with the use of an intraluminal filament to occlude the left MCA for 3, 6 or 9 hours.Sham-operations were also done. Mild hypothermia (32℃～35℃) was given for 3 or 5 hours.At the 24th hour after reperfusion, all rats were decapitated. Brain water content (BWC) wasdetermined by dry-wet method.Results Compared with sham-operated group, the BWC of all MCAO/R groups were increasedsignificantly. The BWCs in mild hypothermia for 3 hours group and 5 hours group afterMCAO3 h/R were 79.39% ± 2.44% and 79.20% ± 1.55%, while the BWC in normothermia groupafter MCAO3 h/R was 82.16% ± 1.50% (P <0.05). There were no significant differences betweenhypothermia group and normothermia group in MCAO6 h/R and MCAO9 h/R groups.Conclusion Mild hypothermia significantly reduces brain edema when reperfusion is performedearly after MCAO. However, mild hypothermia has no significant effect on brain edema whenreperfusion is prolonged.

Key words: Hypothermia; Brain ischemia; Reperfusion Brain edema

摘要： 目的 研究亚低温对延迟时间窗再灌注的局灶脑缺血大鼠缺血性脑水肿的治疗作用。方法 SD雄性大鼠96只，线栓法制作大脑中动脉闭塞模型后随机分为缺血3 h组、缺血6 h组、缺血9 h组（每组各30只），分别在造模3 h、6 h和9 h后拔出线栓，使大脑中动脉再灌注。各缺血组按照再灌注后是否给予亚低温治疗及亚低温持续时间分为常温、亚低温3 h和亚低温5 h三个亚组，每个亚组有10只大鼠。另设假手术组6只。缺血组大鼠在再灌注24 h后处死取脑，假手术组在术后24 h处死取脑，干－湿重法测定各组缺血侧脑组织含水量并进行比较。结果 与假手术组比较，缺血组缺血侧脑组织含水量明显增高。缺血3 h组中3 h亚低温和5 h亚低温亚组的缺血侧脑组织含水量与缺血3 h常温组比较，差异有统计学意义（79.39％±2.44％ vs82.16％±1.50％，P <0.05；79.20％±1.55％ vs 82.16％±1.50％，P <0.05）。其余各缺血组中经过亚低温治疗的大鼠与常温亚组的脑组织含水量无统计学差异。结论 亚低温可减轻缺血早期（3 h）再灌注的脑组织水肿，保护缺血脑组织，而对晚期（6 h和9 h）再灌注的缺血性脑水肿无论亚低温时间长短均无明显保护作用。

关键词: 亚低温; 脑缺血; 再灌注; 脑水肿