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The blood-brain barrier (BBB) plays an important role in regulating and restricting transfer of molecules into the interstitial space of the brain. Anesthetic agents may affect the permeability of the BBB. In this investigation, the effect of isoflurane on the transport of small hydrophilic molecules across the BBB was studied in rats by measuring the blood-brain transfer coefficient (Ki) and the regional cerebral blood flow (rCBF) and by calculating the capillary permeability-surface area (PS) product. In the control group, after a femoral artery and vein were catheterized under isoflurane, anesthesia, rats were allowed to remain awake for 2 h before measuring Ki (n = 6) or rCBF (n = 11). In the two experimental groups, rats were anesthetized with 1% and 2% isoflurane respectively, and their lungs were mechanically ventilated through a tracheal tube. Ki was measured (1% n = 6, 2% n = 7) using 14C-α-aminoisobutyric acid, and rCBF was measured (2% n = 7) using 14C-α-iodoantipyrine. Two percent isoflurane did not affect rCBF in 9 of 13 brain regions. Blood flow was less in the lateral and posterior cortex and greater in the medulla and pons when compared with the control group. Ki was less in 11 of 13 brain regions in both the 1% and 2% isoflurane groups than in the control group. There was no significant difference between 1 and 2% isoflurane in any brain region. The average values of Ki in all of the brain regions were 8.9 ± 4.9 μl·g-1·min-1 in the control group and 4.6 ± 2.6 and 5.1 ± 3.4 μl·g-1 min-1 in the 1% and 2% isoflurance groups, respectively (P

Background This study was performed to determine whether mild hypothermia (32 degrees C) could attenuate the degree of blood-brain barrier (BBB) disruption caused by a hyperosmolar solution and whether the degree of disruption would vary depending on anesthetic agents. Methods Rats were assigned to one of four groups: normothermic isoflurane, normothermic pentobarbital, hypothermic isoflurane, and hypothermic pentobarbital. During isoflurane (1.4%; normothermic or hypothermic) or pentobarbital (50 mg/kg administered intraperitoneally; normothermic or hypothermic) anesthesia, the external carotid artery and the femoral artery and vein were catheterized. Body temperature was maintained at 37 and 32 degrees C 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 ml x kg(-1) x s(-1) for 30 s. The transfer coefficient of 14C-alpha-aminoisobutyric acid was determined. Results Blood pressure was similar among the four groups of animals. The degree of the BBB disruption by hyperosmolar mannitol was less with isoflurane than pentobarbital anesthesia in the normothermic groups (transfer coefficient: 29.9 +/- 17.1 and 50.4 +/- 17.5 microl x g(-1) x min(-1) for normothermic 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 microl x g(-1) x min(-1), P < 0.05 vs. normothermic isoflurane; hypothermic pentobarbital: 30.2 +/- 13.9 microl x g(-1) x min(-1), P < 0.05 vs. normothermic pentobarbital), but the disruption was less during isoflurane anesthesia (hypothermic isoflurane vs. hypothermic pentobarbital, P < 0.005). In the contralateral cortex, there were no significant differences among these four experimental groups. Conclusions The data demonstrated that hypothermia was effective in attenuating 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 as well as the hypothermic groups.