Effects of different ratios of medicine dosage for sevoflurane and propofol on postoperative cognitive function in aged rats

Abstract

Objective To evaluate the effects of different ratios of medicine dosage for sevoflurane and propofol on postoperative cognitive function in aged rats. Methods Sixty healthy male Wistar rats, aged 18-20 months, weighing 600-650 g, were divided into 6 groups(n=10 each)using a random number table: control group(group C), sevoflurane anesthesia group(group S), propofol anesthesia group(group P)and different ratios of medicine dosage for sevoflurane and propofol groups(group SP1, group SP2 and group SP3). Normal saline 10 ml was infused intravenously in group C. Group S inhaled 3.1% sevoflurane.Propofol was infused intravenously at a rate of 40 mg·kg-1·h-1 in group P. In group SP1, 2.4% sevoflurane was inhaled, and propofol was intravenously infused at a rate of 10 mg·kg-1·h-1.In group SP2, 1.8% sevoflurane was inhaled, and propofol was intravenously infused at a rate of 20 mg·kg-1·h-1.In group SP3, 1.2% sevoflurane was inhaled, and propofol was intravenously infused at a rate of 30 mg·kg-1·h-1.Duration of anesthesia was 2 h in all the groups.After loss of righting reflex, open reduction and internal fixation was performed after tibial fracture was induced in the other five groups except group C. At 1 day after anesthesia, Y-maze test was performed, and the time spent on the novel arm and total number of entries into each arm were recorded, and fear conditioning test was carried out for determination of the rate of freezing time to reflect the cognitive function.The rats were sacrificed after behavioral testing, and the hippocampus was removed for determination of occludin, matrix metalloproteinase-2(MMP-2)and MMP-9 expression by Western blot. Results Compared with group C, the time spent on the novel arm was significantly shortened, the total number of entries into each arm and rate of freezing time were decreased, the expression of occludin was down-regulated, the expression of MMP-2 and MMP-9 was up-regulated in the other five groups, and the most unmarked change in the indices mentioned above was found in group SP2(P<0.05 or 0.01). Conclusion Different ratios of medicine dosage for sevoflurane and propofol can induce postoperative cognitive decline, and inhaling 1.8% sevoflurane and infusing propofol 20 mg·kg-1·h-1 produce little influence on postoperative cognitive function in aged rats. Key words: Anesthetics, inhalation; Propofol; Cognition disorders; Postoperative complications; Aged