• R Burger, H Vince, J Meixensberger, and K Roosen.
• Department of Neurosurgery, University of Würzburg, Germany.
• Neurol. Res. 1998 Jan 1; 20 Suppl 1: S52-60.

AbstractTime-related effects of hypothermia on intracranial pressure (ICP), brain (Tbr) and rectal temperature (Tc), cortical (LDF) and subcortical microcirculation (ti-pO2) were assessed following a unilateral balloon induced epidural focal mass lesion in rats. Results of injured but normothermia animals (Group A, n = 6) were compared with hypothermia animals (Group B, n = 6). Parameters were recorded during balloon expansion (BE) to an ICP of 60 mmHg followed by a period of sustained inflation (SI) of 30+/-2 min. Animals in Group B were then cooled to 31.7+/-0.4 degrees C (Tbr) during SI. After reperfusion animals were monitored 178+/-4 min. The study protocol concluded with a rewarming phase of the hypothermic animals. Balloon expansion led to a Cushing response and flattening of the EEG. In both groups Tbr decreased during inflation of the balloon 0.5-0.8 degrees C below Tc and during SI in Group A 1.7 degrees C below Tc. During SI and reperfusion Tbr decreased below Tc in Group A but remained above Tc in Group B (p < 0.003). During sustained inflation LDF decreased in group A to 21% and in Group B to 45% of baseline values. After 178+/-4 min of reperfusion LDF reached 68% of baseline values in Group A and 97% in Group B (p < 0.001). During sustained inflation ti-pO2 showed median values of 0.8 mmHg in Group A and 5.5 mmHg in Group B. After reperfusion ti-pO2 reached normal values in both groups (p < 0.3) but ti-pO2 showed 18% higher values before rewarming. After reperfusion the secondary increase of ICP was reduced (p < 0.006) and CPP was improved by 20% in Group B. EEG restored quicker in Group B than Group A (106+/-11 min vs. 188+/-25 min). Intra-ischemic hypothermia improved cerebral microcirculation, prevented a secondary increase of ICP and improved restoration of EEG after ischemia-reperfusion.

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