Effect of hypoxic-ischemic time on reduction of hypoxic-ischemic brain injury by sevoflurane postconditioning in neonatal rats

Abstract

Objective To evaluate the effect of hypoxic-ischemic time on reduction of hypoxic-ischemic brain injury by sevoflurane postconditioning in neonatal rats. Methods Two hundred and ten 7-day-old Sprague-Dawley rats (105 male, 105 female), weighing 13-17 g, were randomly divided into 7 groups (n=30 each) using a random number table: sham operation group (group Sham), hypoxia-ischemia group (group HI), and sevoflurane postconditioning at different hypoxic-ischemic time point groups (P0, P3, P6, P12 and P24 groups). Immediately after ligation of the left common carotid artery, and at 3, 6, 12 and 24 h after ligation, the rats inhaled the mixed gas containing 2% sevoflurane for 30 min in P0, P3, P6, P12 and P24 groups, respectively.The fatality was recorded within 7 days after establishment of the model.At 7 days after establishment of the model, the rats were sacrificed, the brains were removed, and the right and left cerebral hemispheres were weighed separately, and the left/right cerebral hemisphere weight ratio was calculated.The hippocampal CA1 region and posterior cingulate gyrus were isolated, and the ratio of density of normal neurons in the left to the right was calculated. Results Compared with group Sham, the left cerebral hemisphere weight, left/right cerebral hemisphere weight ratio, and ratio of density of normal neurons were significantly decreased, and the fatality rate was increased in the other six groups (P 0.05). Compared with group P6, the left cerebral hemisphere weight, left/right cerebral hemisphere weight ratio, and ratio of density of normal neurons were significantly increased in P0 and P3 groups (P 0.05). Conclusion Sevoflurane postconditioning performed within 6 h of hypoxia-ischemia can reduce hypoxic-ischemic brain injury, and it provides no cerebral protection if exceeding 12 h. Key words: Time factors; Anesthetics, inhalation; Hypoxia-ischemia, brain; Infant, newborn; Ischemic postconditioning