Protective effects of high thoracic epidural anesthesia with different concentrations of bupivacaine on global cerebral ischemia/reperfusion injury in rats

Objective To compare the effects of high thoracic epidural anesthesia (HTEA) with different concentrations of bupivacaine on global cerebral ischemia/reperfusion injury (CI/RI) in rats. Methods Twenty-four male Wistar rats were randomly divided into four groups (n=6): a sham-operated group (SH group, 20 μl/h 0.9% saline), a control group (C group, 20 μl/h 0.9% saline), a high thoracic epidural anesthesia group 1 (HTEA1 group, 20 μl/h 0.250% bupivacaine), and a high thoracic epidural anesthesia group 2 (HTEA2 group, 20 μl/h 0.125% bupivacaine). Then, a global CI/RI model of rat was established by the four-artery occlusion method. During ischemia and reperfusion, the mean arterial blood pressure (MAP) and heart beat were recorded. The Neurological Deficit Score (NDS) was studied before ischemia and 24 h after CI/RI. The rats were sacrificed 24 h after reperfusion and the brains were collected for paraffin embedding. Hematoxylin-eosin (H-E) staining, Nissl-staining and TdT-mediated DUTP-biotin nick end labeling (TUNEL) staining were used to observe neurons in the hippocampus. The expression of fractalkine (FKN) proteins in the hippocampus were detected by immunohistochemical staining. Results Compared with the SH group, the HTEA1, HTEA2 and C groups showed remarkably increased MAP when ischemia began (P<0.05) and markedly decreased MAP during reperfusion (P<0.05), as well as remarkable increases in the number of apoptotic neurons and the expression of FKN and marked decreases in NDS and the number of survival neurons (P<0.05). Compared with the C group, the HTEA1 and HTEA2 groups presented an obviously increased number of survival neurons, and decreased number of apoptotic cells and FKN expression (P<0.05). There were no significant differences in MAP, HR and NDS among the C group and HTEA groups. Meanwhile, there were no significant differences in each indicator between the two groups. Conclusions HTEA with bupivacaine is beneficial to protect against ischemia/reperfusion injury in rats, without significant different effects between 0.125% and 0.250% bupivacaine. Key words: Bupivacaine; Anesthesia, epidural; Brain; Reperfusion injury