The protective effect of isoflurane against focal cerebral ischemia- reperfusion injury in rats

Objective To determine if isoflurane has protective effect on brain against focal ischemia-reperfusion injury in rats. Methods Thirty-two male SD rats weighing 280-320 g were anesthetized with intraperitoneal peritobarbital 40 mg·kg-1 . Middle cerebral artery occlusion (MCAO) was performed by surgical exposure of common, internal and external carotid arteries through a longitudinal incision in the neck. A nylon filament (0.25-0.30 mm in diameter) with rounded end was inserted into internal carotid artery and threaded cranially until resistance was felt. The depth of insertion was about 20-22 mm. The animals were randomly divided into four equal groups: sham operation group in which carotid arteries were exposed but no MCAO was performed; ischemia group:the animals inhaled 100% O2 for 30 min before the beginning of MCAO which was maintained for 2 h; isoflurane groups: isoflurane 0.9% (group 3 ) or 1.5 % ( group 4) was inhaled for 30 min before the 2 h MCAO. Tympanic membrane temperature was monitored during ischemia-reperfusion. After MCAO and emergence from anesthesia, neurologic deficit of the animals was assessed by a 0-4 grade scoring system (0 = no deficit, 4 = unable to walk, unconscious). After 2 h MCAO 22 h or 70 h reperfusion the animals were decapitated and brain was immediately removed for determination of infarct size and light and electron microscopic examination. Results The tympanic membrane temperature on the ischemic side was significantly lower than that on the non-ischemic side. The maximal difference in the temperature between the two sides was 0.78℃±0.35℃. Isoflurane inhalation significantly reduced the infarct size at the end of 22 h and 70 h reperfusion. 1.5% isoflurane inhalation was more effective than 0.9% in reducing the infarct size. Light and electron microscopic examination showed that isoflurane significantly reduced neuronal, mitochondrial and endothelial cell damage induced by ischemia-reperfusion injury.Conclusion Inhalation of 0.9% or 1.5% isoflurane can protect brain from focal ischemia reperfusion injury to some extent in rats.