The significance of hypothermic acid-base management induced before ischemia in a rat model of transient middle cerebral artery occlusion.
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 degrees C) was maintained in two other groups of 7 anesthetized rats, in which alpha-stat (PaCO2 measured at 37 degrees 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.
Nagai
S
S
Department of Neurosurgery, Kitasato University School of Medicine, Japan.
Irikura
K
K
Maruyama
S
S
Miyasaka
Y
Y
D000136:Acid-Base Equilibrium; D000818:Animals; D001157:Arterial Occlusive Diseases / Q000150:complications / Q000473:pathology / Q000628:therapy*; D002544:Cerebral Infarction / Q000473:pathology; D004195:Disease Models, Animal; D006973:Hypertension / Q000150:complications*; D007036:Hypothermia, Induced; D007430:Intraoperative Care / Q000379:methods; D002546:Ischemic Attack, Transient / Q000209:etiology / Q000473:pathology / Q000517:prevention & control*; D008297:Male; D051381:Rats; D011918:Rats, Inbred SHR