Early effects of acid-base management during hypothermia on cerebral infarct volume, edema, and cerebral blood flow in acute focal cerebral ischemia in rats

Background: Although the frequency for the use of moderate hypothermia in acute ischemic stroke is increasing, the optimal acid-base management during hypothermia remains unclear. This study investigates the effect of pH- and alpha-stat acid-base management on cerebral blood flow (CBF), infarct volume, and cerebral edema in a model of transient focal cerebral ischemia in rats. Methods: Twenty Sprague-Dawley rats were subjected to transient middle cerebral artery occlusion (MCAO) for 2 h during normothermic conditions followed by 5 h of reperfusion during hypothermia (33degreesC). Animals were artificially ventilated with either alpha- (n = 10) or pH-stat management (n = 10). CBF was analyzed 7 h after induction of MCAO by iodo[C-14]antipyrine autoradiography. Cerebral infarct volume and cerebral edema were measured by high-contrast silver infarct staining (SIS). Results. Compared with the a-stat regimen, pH-stat management reduced cerebral infarct volume (98.3 +/- 33.2 nim 3 vs. 53.6 +/- 21.6 mm(3); p greater than or equal to 0.05 mean +/- SD) and cerebral edema (10.6 +/- 4.0% vs. 3.1 +/- 2.4%; P greater than or equal to 0.05). Global CBF during pH-stat management exceeded that of a-stat animals (69.5 +/- 12.3 ml (.) 100 g(-1) (.) min(-1) vs. 54.7 +/- 13.3 ml (.) 100 g(-1) (.) min(-1); P greater than or equal to 0.05). The regional CBF of the ischendc hemisphere was 62.1 +/- 11.2 ml (.) 100 g(-1) (.) min(-1) in the pH-stat group versus 48.2 +/- 7.2 ml (.) 100 g(-1) (.) min(-1) in the alpha-stat group (P greater than or equal to 0.05). Conclusions. In the very early reperfusion period (5 h), pH-stat management significantly decreases cerebral infarct volume and edema as compared with a-stat during moderate hypothermia, probably by increasing CBF.