Effects of dexmedetomidine postconditioning on brain injury after cardiac arrest and resuscitation in a swine model / 中华急诊医学杂志

ABSTRACT

Objective To investigate the effects of dexmedetomidine postconditioning on brain injury after cardiac arrest and resuscitation in a swine model.Methods Twenty-eight healthy male domestic pigs,weighing 36±2 kg,were randomized (random number) into 4 groups (n=7 each group)sham operation group (S group),cardiopulmonary resuscitation group (CPR group),low-dose dexmedetomidine postconditioning group (LDP group),and high-dose dexmedetomidine postconditioning group (HDP group).Animals in the S group only underwent the surgical preparation.In the other three groups,the experimental model was established by 8 mins of electrically induced ventricular fibrillation and then 5 mins of cardiopulmonary resuscitation.At 5 min after resuscitation,a loading dose of dexmedetomidine of 0.25 μg/kg was intravenously infused followed by continuous infusion at a rate of 0.25 μg/(kg·h) for 6 h in the LDP group,and a loading dose of dexmedetomidine of 0.5 μ.g/kg was infused followed by continuous infusion at a rate of 0.5 μg/(kg·h) for 6 h in the HDP group.The same amount of normal saline was administered in the S and CPR groups.At 1 h,3 h,6 h and 24 h after resuscitation,the levels of serum neuron specific enolase (NSE) and S100B protein were measured.At 24 h after resuscitation,neurologic deficit score (NSD) was evaluated.After that,the animals were euthanized and cerebral cortex was obtained for the determination of tumor necrosis factor-α (TNF-α),interleukin-6 (IL-6)and malondialdehyde (MDA) contents,superoxide dismutase (SOD) activity,cell apoptosis and caspase-3 expression.Results Compared with the S group,post-resuscitation neurologic dysfunction and brain injury were observed in the other three groups,which were indicated by significantly higher NDS and markedly greater levels of serum NSE and S 100B (all P＜0.05).Compared with the CPR group,the score of NDS at 24 h post-resuscitation were significantly lower and the levels of serum NSE and S100B at 6 h and 24 h post-resuscitation were significantly less in the LDP and HDP groups [NDS194±26,103±16 vs 278±23 at 24 h;NSE (ng/mL)32.4±1.8,28.6±3.7 vs 36.2±2.8 at 6 h,39.9±4.2,35.1±1.5 vs 45.1±3.0 at 24 h;S100B (pg/mL)2 534±207,2 382±170 vs 2 825±113 at 6 h,3 719±164,3 246±176 vs 4 085±161 at 24 h,all P＜0.05].Compared with the LDP group,neurologic dysfunction and brain injury at 24 h postresuscitation were further significantly alleviated in the HDP group (all P＜0.05).Pathological analysis indicated that brain inflammation,oxidative stress and cell apoptosis were observed after resuscitation in the CPR,LDP and HDP groups.However,the contents of TNF-α,IL-6 and MDA were significantly lower while the activity of SOD was significantly higher,and cell apoptosis and caspase-3 expression were significantly reduced in the brain after resuscitation in the LDP and HDP groups compared with the CPR group (all P＜0.05).In addition,those pathological injuries mentioned above were further significantly alleviated in the brain after resuscitation in the HDP group compared to the LDP group (all P＜0.05).Conclusions Dexmedetomidine postconditioning significantly alleviated the severity of postresuscitation brain injury in a dose-dependent manner,in which the protection was produced possibly through reducing tissue inflammation,oxidative stress and cell apoptosis.