Effects of mild hypothermia on blood-brain barrier disruption during isoflurane or pentobarbital anesthesia

Background: This study was performed to determine whether mild hypothermia (32 degreesC) could attenuate the degree of blood-brain barrier (BBB) disru ption caused by a hyperosmolar solution and whether the degree of disruptio n would vary depending on anesthetic agents. Methods: Rats were assigned to one of four groups: normothermic isoflurane, normothermic pentobarbital, hypothermic isoflurane., and hypothermic pento barbital. During isoflurane (1.4%; normothermic or hypothermic) or pentobar bital (50 mg/kg administered intraperitoneally; normothermic or hypothermic ) anesthesia, the external carotid artery and the femoral artery and vein w ere catheterized. Body temperature was maintained at 37 and 32 degreesC for the normothermic and hypothermic groups, respectively. To open the BBB, 25 % mannitol was infused through the right carotid artery at the rate of 0.25 nil . kg(-1) . s(-1) for 30 s. The transfer coefficient of C-14-alpha -ami noisobutyric acid was determined. Results. Blood pressure was similar among the four groups of animals. The d egree of the BBB disruption by hyperosmolar mannitol was less with isoflura ne than pentobarbital anesthesia in the normothermic groups (transfer coeff icient: 29.9 +/- 17.1 and 50.4 +/- 17.5 mul . g(-1) . min(-1) for normother mic isoflurane and pentobarbital, respectively; P < 0.05). Mild hypothermia decreased the BBB disruption during anesthesia with both anesthetic agents (hypothermic isoflurane: 9.8 +/- 8.3 mul . g(-1) . min(-1), P < 0.05 vs. n ormothermic isoflurane; hypothermic pentobarbital: 30.2 +/- 13.9 mul . g(-1 ) . min(-1), P < 0.05 vs. normothermic pentobarbital), but the disruption w as less during isoflurane anesthesia (hypothermic isoflurane vs. hypothermi c pentobarbital, P < 0.005). in the contralateral cortex, there were no sig nificant differences among these four experimental groups. Conclusions. The data demonstrated that hypothermia. was effective in atten uating BBB disruption by hyperosmolar mannitol during isoflurane as well as pentobarbital anesthesia. The degree of disruption appeared smaller during isoflurane than during pentobarbital anesthesia in both the normothermic a s well as the hypothermic groups.