Abstract
We investigated the effects of acid-base management during pre- and intra-ischemic hypothermia on regional cerebral blood flow (rCBF) and infarct volume using a transient focal cerebral ischemia model Normal temperature was maintained in a group of 7 anesthetized rats, and hypothermia (30° C) was maintained in two other groups of 7 anesthetized rats, in which alpha-stat (PaCO2 measured at 37° C was maintained at 36 mmHg) and pH-stat (PaCO2 corrected for body temperature was maintained at 36 mmHg) conditions, respectively, were established. rCBF was monitored by laser-Doppler flowmetry in the ischemic penumbra. The middle cerebral artery (MCA) was occluded for 2 h and then reperfused. Infarct volume was measured after 24 h and expressed as a percentage of hemisphere volume. Pre-ischemic hypothermia reduced rCBF in the alpha-stat group and the pH-stat group to 52 ±2% and 86 ± 7%, respectively (p 0.01). After MCA occlusion, rCBF dropped in the control group, alpha-stat group, and pH-stat group to 57 ± 11%, 31 ± 9%, 27 ± 10%, respectively. Infarct volume in the alpha-stat group and pH-stat group was significantly smaller (10 ± 1% and 7 ±2%) than in the control group (42 ±7%, p < 0.01), but no differences were found between the hypothermic groups. Differences in acid-base management in the present study did not affect infarct volume, but pre-ischemic rCBF in the alpha-stat group was significantly lower than in the pH-stat group. The steeper fall in rCBF after MCA occlusion in the pH-stat group suggested that the autoregulatory response of the collateral pathways may have been reduced in this group. [Neurol Res 1999; 21: 204-208]
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