Induced hyperthermia exacerbates neurologic neuronal histologic damage after asphyxial cardiac arrest in rats

BACKGROUND: Temperature is an important modulator of the evolution of ischemic brain injury--with hypothermia lessening and hyperthermia exacerbating damage. We recently reported that children resuscitated from predominantly asphyxial arrest often develop an initial spontaneous hypothermia followed by delayed hyperthermia. The initial hypothermia observed in these children was frequently treated with warming lights which, despite careful monitoring, often resulted in overshoot hyperthermia. We have previously reported in a rat model of asphyxial cardiac arrest that active warming, to prevent spontaneous hypothermia, worsens brain injury. OBJECTIVE: We sought to determine whether delayed induction of hyperthermia would worsen brain injury after asphyxial arrest in rats. DESIGN: Male Sprague-Dawley rats were asphyxiated for 8 mins and resuscitated. An implantable temperature probe was placed into the peritoneum before asphyxia. The probe is a component of a computer-based, radiofrequency, telemetry system (Minimitter, Sunriver, OR) that allowed continuous acquisition and manipulation (via heating and cooling devices) of core (intraperitoneal) body temperature. Body temperature was monitored but not manipulated for the first 24 hrs of recovery. Rats were assigned to: no temperature manipulation (n = 21), induced hyperthermia (40 +/- 0.5 degrees C) for 3 hrs beginning at 24 hrs (n = 21), or induced hyperthermia at 48 hrs (n = 10). Control groups included sham rats (all surgical procedures except asphyxia) treated with induced hyperthermia at 24 hrs (n = 4) or 48 hrs (n = 4) and na?ve rats (n = 4). Rats were killed at 7 days and injured neurons in hematoxylin and eosin stained coronal brain sections through dorsal hippocampus were scored in a semiquantitative manner on a scale of 0 to 10 (0 = normal; 1 = up to 10% neurons with ischemic neuronal changes; 10 = 90-100% neurons with ischemic neuronal changes). Normal-appearing neurons were also counted in CA1. The number of normal-appearing neurons in a 20x field in CA1 were also counted. MAIN RESULTS: All na?ve and sham hyperthermia control rats survived the protocol. There was a trend toward a larger mortality rate in asphyxiated rats treated with induced hyperthermia at 24 hrs (9 of 21 died) vs. asphyxiated rats without induced hyperthermia (3 of 21) or with hyperthermia induced at 48 hrs (3 of 10) (Kaplan-Meier p=.0595). Asphyxiated rats with hyperthermia induced at 24 hrs had larger (worse) histopathology damage scores than rats subjected to asphyxia without induced hyperthermia (9.3 +/- 1.5 vs. 6.2 +/- 2.6; p=.001). Histopathology damage scores in asphyxiated rats with hyperthermia induced at 48 hrs did not differ from those in rats asphyxiated without induced hyperthermia (6.4 +/- 3.0 vs. 6.2 +/- 2.6; p=.907). There were fewer normal-appearing CA1 neurons in asphyxiated rats with hyperthermia induced at 24 hrs vs. rats subjected to asphyxia without induced hyperthermia (33 +/- 13 vs. 67 +/- 36; p=.002). The number of normal-appearing CA1 neurons in asphyxiated rats with hyperthermia induced at 48 hrs did not differ from that in rats asphyxiated without induced hyperthermia (59 +/- 21 vs. 67 +/- 36; p=.885). CONCLUSIONS: Induced hyperthermia when administered at 24 hrs, but not 48 hrs, worsens ischemic brain injury in rats resuscitated from asphyxial cardiac arrest. This may have implications for postresuscitative management of children and adults resuscitated from cardiac arrest. The common clinical practice of actively warming patients with spontaneous hypothermia might result in iatrogenic injury if warming results in hyperthermic overshoot. Avoidance of hyperthermia induced by active warming at critical time periods after cardiac arrest may be important.     

Neurotensin-induced hypothermia improves neurologic outcome after hypoxic-ischemia

OBJECTIVE: External cooling is commonly used to force induction of mild hypothermia but requires equipment, has a slow onset of action, and must be prolonged to provide permanent neurologic benefits after hypoxic-ischemia. It is unknown whether the method for inducing mild hypothermia affects neurologic outcome after near-drowning. The objective of the study was to induce mild hypothermia with neurotensin analog NT77 or external cooling in a rat model of near-drowning. We hypothesize that NT77 would be more effective for improving neurologic outcome than external cooling of the same duration. DESIGN: Rats were randomized to a normothermic control, neurotensin-induced hypothermia, brief external cooling, or prolonged external cooling group after asphyxial cardiac arrest. SETTING: Laboratory investigation. SUBJECTS: Forty-eight rats. INTERVENTIONS: Mild hypothermia was induced by external cooling for 4 hrs (brief external cooling) or 24 hrs (prolonged external cooling) or by neurotensin-induced hypothermia administration 30 mins after asphyxial cardiac arrest in rats. MEASUREMENTS: Outcome was assessed by a neurologic deficit score, the Morris water maze, and CA1 hippocampus histology 15 days after resuscitation. MAIN RESULTS: Neurologic deficit score at 72 hrs after asphyxial cardiac arrest was lower with neurotensin-induced hypothermia (score, 0) and prolonged external cooling (score, 0) vs. normothermic control (score, 20) and brief external cooling (score, 18; p <.05). Latency time in the Morris water maze 15 days after asphyxial cardiac arrest was decreased with neurotensin-induced hypothermia (14+/-11 secs) and prolonged external cooling (18+/-9 secs) vs. normothermic control (74+/-17 secs) and brief external cooling (78+/-18 secs, p <.05). There was less ischemic neuronal damage with neurotensin-induced hypothermia (28+/-24%) and prolonged external cooling (21+/-14%) vs. normothermic control (61+/-32%) and brief external cooling (51+/-32%). CONCLUSIONS: Neurotensin-induced hypothermia improved neurologic outcome after asphyxial cardiac arrest in rats vs. brief external cooling but was comparable to prolonged external cooling.     

Post-cardiac arrest temperature manipulation alters early EEG bursting in rats

OBJECTIVES: Hypothermia improves outcomes after cardiac arrest (CA), while hyperthermia worsens injury. EEG recovers through periodic bursting from isoelectricity after CA, the duration of which is associated with outcome in normothermia. We quantified burst frequency to study the effect of temperature on early EEG recovery after CA. METHODS: Twenty-four rats were divided into three groups, based on 6h of hypothermia (T=33 degrees C), normothermia (T=37 degrees C), or hyperthermia (T=39 degrees C) immediately post-resuscitation from 7-min asphyxial CA. Temperature was maintained using surface cooling and re-warming. Neurological recovery was defined by 72-h neurological deficit score (NDS). RESULTS: Burst frequency was higher during the first 90min in rats treated with hypothermia (25.6+/-12.2min(-1)) and hyperthermia (22.6+/-8.3min(-1)) compared to normothermia (16.9+/-8.5min(-1)) (p<0.001). Burst frequency correlated strongly with 72-h NDS in normothermic rats (p<0.05) but not in hypothermic or hyperthermic rats. The 72-h NDS of the hypothermia group (74, 61-74; median, 25-75th percentile) was significantly higher than the normothermia (49, 47-61) and hyperthermia (43, 0-50) groups (p<0.001). CONCLUSIONS: In normothermic rats resuscitated from CA, early EEG burst frequency is strongly associated with neurological recovery. Increased bursting followed by earlier restitution of continuous EEG activity with hypothermia may represent enhanced recovery, while heightened metabolic rate and worsening secondary injury is likely in the hyperthermia group. These factors may confound use of early burst frequency for outcome prediction.     

Improving neurological outcomes post-cardiac arrest in a rat model: immediate hypothermia and quantitative EEG monitoring

OBJECTIVES: Therapeutic hypothermia (TH) after cardiac arrest (CA) improves outcomes in a fraction of patients. To enhance the administration of TH, we studied brain electrophysiological monitoring in determining the benefit of early initiation of TH compared to conventional administration in a rat model. METHODS: Using an asphyxial CA model, we compared the benefit of immediate hypothermia (IH, T=33 degrees C, immediately post-resuscitation, maintained 6h) to conventional hypothermia (CH, T=33 degrees C, starting 1h post-resuscitation, maintained 12h) via surface cooling. We tracked quantitative EEG using relative entropy (qEEG) with outcome verification by serial Neurological Deficit Score (NDS) and quantitative brain histopathological damage scoring (HDS). Thirty-two rats were divided into 4 groups based on CH/IH and 7/9-min duration of asphyxial CA. Four sham rats were included for evaluation of the effect of hypothermia on qEEG. RESULTS: The 72-h NDS of the IH group was significantly better than the CH group for both 7-min (74/63; median, IH/CH, p<0.001) and 9-min (54/47, p=0.022) groups. qEEG showed greater recovery with IH (p<0.001) and significantly less neuronal cortical injury by HDS (IH: 18.9+/-2.5% versus CH: 33.2+/-4.4%, p=0.006). The 1-h post-resuscitation qEEG correlated well with 72-h NDS (p<0.05) and 72-h behavioral subgroup of NDS (p<0.01). No differences in qEEG were noted in the sham group. CONCLUSIONS: Immediate but shorter hypothermia compared to CH leads to better functional outcome in rats after 7- and 9-min CA. The beneficial effect of IH was readily detected by neuro-electrophysiological monitoring and histological changes supported the value of this observation.     

The effect of mild hypothermia and induced hypertension on long term survival rate and neurological outcome after asphyxial cardiac arrest in rats

STUDY OBJECTIVE: we studied the long-term effect of a combined treatment with resuscitative mild hypothermia and induced hypertension on survival rate and neurological outcome after asphyxial cardiac arrest (CA) in rats. METHODS: 36 male Wistar rats, were randomised into three groups: Group I (n=10): anaesthetised with halothane and N(2)O/O(2) (70/30%) had vessel cannulation but no asphyxial CA; mechanical ventilation was continued to 1 h. Group II (n=13): under the same anaesthetic conditions and vessel cannulation, was subjected to asphyxial CA of 8 min, reversed by brief external heart massage and followed by mechanical ventilation to 1 h post restoration of spontaneous circulation (ROSC). Group III (n=13): received the same insult and resuscitation as described in group II, but in contrast to the previous group, a combination treatment of hypothermia (34 degrees C) and induced hypertension was started immediately after ROSC and maintained for 60 min ROSC. Survival rate and neurological deficit (ND) scores were determined before arrest, at 2 and 24 h, and each 24-h up to 4 weeks after ROSC. RESULTS: Baseline variables were the same in the three groups. Comparison of the asphyxial CA groups (groups II and III), showed an increased, although not statistically significant, survival rate at 72 h after ROSC in group III, and it became highly significant at 4 weeks after ROSC. The ND scores were the same in both asphyxial CA groups (groups II and III). CONCLUSIONS: Resuscitative mild hypothermia and induced hypertension after asphyxial CA in rats is associated with a better survival rate. This beneficial effect persisted for 4 weeks after ROSC.     

Neurotensin Analog NT69L Induces Rapid and Prolonged Hypothermia after Hypoxic Ischemia

OBJECTIVE: To determine whether the neurotensin analog NT69L, administered systemically, could induce mild brain hypothermia after asphyxial cardiac arrest (ACA) in rats. METHODS: The study design was experimental, blinded, randomized, and approved by the animal use committee. All rats had continuous monitoring of brain temperature and sustained 8 minutes of ACA, resuscitation, and either saline or NT69L intravenously after return of spontaneous circulation (ROSC). Rats surviving 14 days after ACA had a neurological deficit score (NDS) and a Morris Water Maze (MWM) test. RESULTS: Seven of eight rats in each group survived 14 days. Brain temperature was less than 35 degrees C 13.1 +/- 3 minutes (mean +/- standard deviation) after NT69L vs controls that remained 37.5 degrees C at the same ambient temperature (p < 0.05 ANOVA). The NT69L group remained below 35 degrees C for 300 +/- 100 minutes while the controls remained at 37.5 +/- 0.5 degrees C. The NDS in the NT69L rats was 3 +/- 3% vs controls 26 +/- 8% (p < 0.05, Kruskal-Wallis, 0% = normal, 100% = brain dead). The NT69L rats performed better on the MWM vs the controls (22 +/- 8 sec vs 45 +/- 26 sec, respectively, p < 0.05 ANOVA). CONCLUSIONS: NT69L induced rapid and prolonged mild brain hypothermia after ACA in this rat model and reduced neurological deficits.     

Survival without brain damage after clinical death of 60-120 mins in dogs using suspended animation by profound hypothermia

OBJECTIVES: This study explored the limits of good outcome of brain and organism achievable after cardiac arrest (no blood flow) of 60-120 mins, with preservation (suspended animation) induced immediately after the start of exsanguination cardiac arrest. DESIGN: Prospective experimental comparison of three arrest times, without randomization. SETTING: University research laboratory. SUBJECTS: Twenty-seven custom-bred hunting dogs (17-25 kg). INTERVENTIONS: Dogs were exsanguinated over 5 mins to cardiac arrest no-flow of 60 mins, 90 mins, or 120 mins. At 2 mins of cardiac arrest, the dogs received, via a balloon-tipped catheter, an aortic flush of isotonic saline at 2 degrees C (at a rate of 1 L/min), until tympanic temperature reached 20 degrees C (for 60 mins of cardiac arrest), 15 degrees C (for 60 mins of cardiac arrest), or 10 degrees C (for 60, 90, or 120 mins of cardiac arrest). Resuscitation was by closed-chest cardiopulmonary bypass, postcardiac arrest mild hypothermia (tympanic temperature 34 degrees C) to 12 hrs, controlled ventilation to 20 hrs, and intensive care to 72 hrs. MEASUREMENTS AND MAIN RESULTS: We assessed overall performance categories (OPC 1, normal; 2, moderate disability; 3, severe disability; 4, coma; 5, death), neurologic deficit scores (NDS 0-10%, normal; 100%, brain death), regional and total brain histologic damage scores at 72 hrs (total HDS >0-40, mild; 40-100, moderate; >100, severe damage), and morphologic damage of extracerebral organs. For 60 mins of cardiac arrest (n = 14), tympanic temperature 20 degrees C (n = 6) was achieved after flush of 3 mins and resulted in two dogs with OPC 1 and four dogs with OPC 2: median NDS, 13% (range 0-27%); and median total HDS, 28 (range, 4-36). Tympanic temperature of 15 degrees C (n = 5) was achieved after flush of 7 mins and resulted in all five dogs with OPC 1, NDS 0% (0-3%), and HDS 8 (0-48). Tympanic temperature 10 degrees C (n = 3) was achieved after flush of 11 mins and resulted in all three dogs with OPC 1, NDS 0%, and HDS 16 (2-18). For 90 mins of cardiac arrest (n = 6), tympanic temperature 10 degrees C was achieved after flush of 15 mins and resulted in all six dogs with OPC 1, NDS 0%, and HDS 8 (0-37). For 120 mins of cardiac arrest (n = 7), three dogs had to be excluded. In the four dogs within protocol, tympanic temperature 10 degrees C was achieved after flush of 15 mins. This resulted in one dog with OPC 1, NDS 0%, and total HDS 14; one with OPC 1, NDS 6%, and total HDS 20; one with OPC 2, NDS 13%, and total HDS 10; and one with OPC 3, NDS 39%, and total HDS 22. CONCLUSIONS: In a systematic series of studies in dogs, the rapid induction of profound cerebral hypothermia (tympanic temperature 10 degrees C) by aortic flush of cold saline immediately after the start of exsanguination cardiac arrest-which rarely can be resuscitated effectively with current methods-can achieve survival without functional or histologic brain damage, after cardiac arrest no-flow of 60 or 90 mins and possibly 120 mins. The use of additional preservation strategies should be pursued in the 120-min arrest model.     

Mild Hypothermia Induced before Cardiac Arrest Reduces Brain Edema Formation in Rats

OBJECTIVES: The mechanisms by which hypothermia improves cardiac arrest (CA)-induced brain damage are unclear. The authors hypothesized that mild hypothermia induced before CA attenuates brain edema formation by preventing neutrophil-mediated dysfunction of the endothelial cell junction proteins. METHODS: Eighteen rats were randomized to normal control surgery (group 1, n = 6), normothermic (37.5 degrees C) CA (group 2, n = 6), or hypothermic (34 degrees C) CA (group 3, n = 6). Hypothermia was induced with external cooling before CA in group 3. Cardiac arrest was induced by 8 minutes of asphyxiation. Brain edema was determined by wet-to-dry weight ratio and cerebral spinal fluid pressure (CSFP). Brain neutrophil content was determined by myeloperoxidase (MPO) activity, and occludin degradation was assessed by western blotting. RESULTS: Normothermic CA significantly increased brain wet-to-dry weight ratio from 4.52 +/- 0.04 in group 1 to 4.80 +/- 0.04 in group 2 (p = 0.0003) and CSFP from 3.6 +/- 0.9 in group 1 to 8.9 +/- 0.9 mm Hg in group 2 (p = 0.004). Mild hypothermia before CA in group 3 significantly reduced brain wet-to-dry weight ratio (4.68 +/- 0.03, p = 0.008 vs. group 2) and CSFP (3.8 +/- 0.5 mm Hg, p = 0.004 vs. group 2). Cardiac arrest increased brain MPO from 0.07 +/- 0.025 in group 1 to 0.16 +/- 0.02 units/gram brain weight in group 2 (p = 0.006) that was not decreased by hypothermia before CA (0.12 +/- 0.02 in group 3 (p = 0.07 vs. group 2). There was no occludin proteolysis in any group. CONCLUSIONS: Mild hypothermia before CA decreases CA-induced brain edema. The hypothermia-elicited reduction in brain edema does not appear to be neutrophil-dependent and the early brain edema formation may not involve the proteolysis of occludin.     

Effects of mild hypothermia on autophagy in hippocampal CAI neurons in rats after CPR北大核心CSCD

Objective To establish the cardiac arrest-cardiopulmonary resuscitation model in rats, and to observe the effect of mild hypothermia on autophagy in hippocampal CAI neurons after ROSC. Methods A total of 36 Wistar rats were randomly divided into two groups: normal temperature treatment group (NT group) and mild hypothermia treatment group ( HT group). To establish the cardiac arrest- cardiopulmonary resuscitation ( CA-CPR) model in rats by epicardial electrical stimulation induced ventricular fibrillation, and to sacrifice 3 animals in each group to obtain the brain cortex in 2nd and 4th hours after ROSC in order to observe the expression of p-AMPK by electron microscope and LC3 granules through Western blot. The neurological deficit score (NDS) was assessed in 24, 48, 72 hours respectively after ROSC. To sacrifice the animals so as to take the cerebrum in 72 hours after ROSC, then calculate the apoptotic index of the hippocampal CAI neurons, which were dyed through TUNEL method. Results The expression of p-AMPK, Beclin-1 and LC3-E/LC3- I ratio in Normothermia group were all lower than the Mild hypothermia group (P < 0. 05 ) , the neurons plasma of hippocampal CAI area in the Hypothermia group demonstrated obvious LC3 granules formation, the NDS score of the Normothermia group and the Mild hypothermia group in ROSC24h, ROSC48h, ROSC72h were 320vs205, 285vsl40, 266vsl20, respectively. The apoptotic index of the hippocampal CA1 area in the Normothemia group in ROSC72h was higher than the Mild hypothermia group, ( P < 0. 05 ). Conclusions Mild hypothermia after cardiopulmonary resuscitation promotes autophagy of the hippocampal CA1 area neurons in rats and reduce neuronal apoptosis.     

Mild protective and resuscitative hypothermia for asphyxial cardiac arrest in rats

It has been shown in dogs that mild hypothermia (34°C) during or immediately after ventricular fibrillation cardiac arrest can improve cerebral outcome. The effect of mild hypothermia on outcome after 8 minutes of asphyxiation (5 minutes' cardiac arrest) was studied for the first time in rats. Restoration of spontaneous circulation was with external cardiopulmonary resuscitation and observation to 72 hours. Three groups of 10 rats each were studied. At 72 hours postarrest, compared with the normothermic control group 1, final overall performance categories (OPC) and neurological deficit scores (NDS) were numerically better in the resuscitative (post-arrest) hypothermia group 2 and significantly better in the protective (pre-intra-arrest) hypothermia group 3 (P < .05). Total brain histopathological damage scores (HDS) were 17 ± 5 in group 1, 14 ± 6 in group 2 (NS), and 6 ± 2 in group 3 (P < .001 versus group 1). HDS correlated with OPC (r = .6, P < .05) and NDS (r = .7, P < .05). Mild hypothermia improved cerebral outcome after asphyxial cardiac arrest in rats, more when induced before than after arrest. The model's insult is within the therapeutic window, which makes it also suitable for screening other cerebral resuscitation potentials.     

A moderate dose of propofol and rapidly induced mild hypothermia with extracorporeal lung and heart assist (ECLHA) improve the neurological outcome after prolonged cardiac arrest in dogs

BACKGROUND AND PURPOSE: Propofol has been shown to protect against neuronal damage induced by brain ischaemia in small animal models. We reported previously that mild hypothermia (33 degrees C) in combination with extracorporeal lung and heart assist (ECLHA) improved the neurological outcome in dogs with cardiac arrest (CA) of 15 min induced during normothermia. In the present study, we investigated the neuroprotective effect of propofol infusion under mild hypothermia with ECLHA in this model. METHODS: Twenty-one female dogs (15 mongrel dogs and 6 beagles) were divided into three groups: Midazolam 0.1 mg/(kg h) infusion group (M, n=7), Propofol 2 mg/(kg h) infusion group (P2, n=7), Propofol 4 mg/(kg h) infusion group (P4, n=7). Normothermic ventricular fibrillation (VF) was induced in all dogs for 15 min, followed by brief ECLHA and 168 h of intensive care. The drug infusion was initiated at a constant rate after the restoration of spontaneous circulation (ROSC) to 24 h. Mild hypothermia (33 degrees C) was maintained for 20 h. Neurological deficit scores (NDS: 0%=normal, 100%=brain death) were evaluated for neurological function from 33 to 168 h. RESULTS: One dog in the M group died, and the remaining dogs survived for 168 h. The P4 group showed better neurological recovery compared with the M group (48 h, 21+/-16% versus 32+/-15%; 72 h, 7+/-6% versus 25+/-11%; 96 h, 6+/-6% versus 21+/-6%; 120 h, 5+/-5% versus 20+/-6%; 144 h, 4+/-4% versus 20+/-6%; 168 h, 4+/-4% versus 20+/-6%, p<0.05). One dog in the P2 and three dogs in the P4 group achieved full neurological recovery (NDS: 0%). The number of intact pyramidal cells in the hippocampal CA1 was greater in the propofol groups than midazolam group (p<0.05). CONCLUSION: The combination of propofol infusion at a rate of 4 mg/(kg h), 24h and rapidly induced mild hypothermia (33 degrees C) with ECLHA might provide a successful means of cerebral resuscitation from CA.     

Strain specific differences in a cardio-pulmonary resuscitation rat model

An asphyxial cardiac arrest rat model, originally developed for Sprague-Dawley rats, was transferred to a Wistar rat model. Several strain specific life support adjustments, i.e. ventilator settings, anaesthesia, and drug requirements, were necessary to stabilize the model for Wistar rats. Despite these arrangements numerous resuscitation related variables appeared different. Three groups were evaluated and compared: a temperature monitored Wistar group 1 (n=34), a temperature controlled Wistar group 2 (n=26) and a temperature controlled Sprague-Dawley group 3 (n=7). Overall, Wistar rats seem to have more sensitive cardio-circulatory system evidenced by a more rapid development of cardiac arrest (164 vs. 201 s), requiring higher adrenaline/epinephrine doses (10 vs. 5 microg/kg) and requiring more time for recovery after resuscitation (i.e. for return of blood pressure and blood gases). Without strict temperature control (as in groups 2+3 rats) group 1 rats went into spontaneous mild to moderate hypothermia during the first 24 h after restoration of spontaneous circulation (ROSC). Spontaneous hypothermia delayed the development of overall visible CA1 neuronal damage 24-48 h, but did not prevent it; therefore the model seemed to be suitable for future studies. Neuronal damages in the CA1 region in Wistar rats appeared to be more as shrunken cell bodies and pyknotic nuclei before resorption took place, whereas in Sprague-Dawley rats appeared in the same region.     

亚低温对复苏后大鼠脑细胞凋亡相关因子的影响

  目的  研究亚低温对心肺复苏后大鼠神经细胞凋亡及凋亡基因表达的影响。  方法  60只健康雄性SD大鼠随机分为常温组(T=37℃±0.5℃)和亚低温组(T=33℃±1.0℃), 每组30只; 窒息法建立心肺复苏模型, 于自主循环恢复后12、24 h通过神经功能缺损评分评价神经功能, 使用TUNEL染色观察脑细胞凋亡情况, 并于自主循环恢复后0、2、6、12、24 h采用RT-PCR检测脑组织中凋亡诱导因子(apoptosis-inducing factor, AIF)、caspase-3、Fas基因mRNA表达。  结果  亚低温组大鼠12及24 h神经功能缺损评分明显高于常温组(P < 0.05), 6、12、24 h神经细胞凋亡数量明显少于常温组(P < 0.05);与常温组相比, 自主循环恢复后各时间点AIF、caspase- 3及6、12、24 h Fas基因mRNA表达显著下调(P < 0.05)。  结论  亚低温可能通过抑制脑组织中AIF、caspase-3、Fas凋亡基因表达, 减少神经元凋亡, 改善神经功能。     

Moderate hypothermia may be detrimental after traumatic brain injury in fentanyl-anesthetized rats

OBJECTIVES: To determine whether transient, moderate hypothermia is beneficial after traumatic brain injury in fentanyl-anesthetized rats. DESIGN: Prospective, randomized study. SETTING: University-based animal research facility. SUBJECTS: Adult male Sprague-Dawley rats. INTERVENTIONS: All rats were intubated, mechanically ventilated, and anesthetized with fentanyl (10 microg/kg intravenous bolus and then 50 microg.kg(-1).hr(-1) infusion). Controlled cortical impact was performed to the left parietal cortex, followed immediately by 1 hr of either normothermia (brain temperature 37 +/- 0.5 degrees C) or hypothermia (brain temperature 32 +/- 0.5 degrees C). Hypothermic rats were rewarmed gradually over 1 hr. Fentanyl anesthesia and mechanical ventilation were continued in both groups until the end of rewarming (2 hrs after traumatic brain injury). MEASUREMENTS AND MAIN RESULTS: Histologic assessment performed 72 hrs after traumatic brain injury was the primary outcome variable. Secondary outcome variables were physiologic variables monitored during the first 2 hrs after traumatic brain injury and plasma catecholamine and serum fentanyl concentrations measured at the end of both hypothermia and rewarming (1 and 2 hrs after traumatic brain injury). Contusion volume was larger in hypothermic vs. normothermic rats (44.3 +/- 4.2 vs. 28.6 +/- 4.0 mm, p <.05), but hippocampal neuronal survival did not differ between groups. Physiologic variables did not differ between groups. Plasma dopamine and norepinephrine concentrations were increased at the end of hypothermia in hypothermic (vs. normothermic) rats (p <.05), indicating that hypothermia augmented the systemic stress response. Similarly, serum fentanyl concentrations were higher in hypothermic (vs. normothermic) rats at the end of both hypothermia and rewarming (p <.05), demonstrating that hypothermia reduced the clearance and/or metabolism of fentanyl. CONCLUSIONS: Moderate hypothermia was detrimental after experimental traumatic brain injury in fentanyl-anesthetized rats. Since treatment with hypothermia has provided reliable benefit in experimental traumatic brain injury with inhalational anesthetics, these results indicate that the choice of anesthesia/analgesia after traumatic brain injury may dramatically influence response to other therapeutic interventions, such as hypothermia. Given that narcotics commonly are administered to patients after severe traumatic brain injury, this study may have clinical implications.     

Rapidly induced hypothermia with extracorporeal lung and heart assist (ECLHA) improves the neurological outcome after prolonged cardiac arrest in dogs

PURPOSE: We reported previously that therapeutic hypothermia with extracorporeal lung and heart assist (ECLHA) improved neurological outcome after 15 min cardiac arrest (CA) in dogs, although 45 min was needed to achieve hypothermia. We now investigate whether rapidly induced hypothermia with ECLHA (RHE) would result in a better outcome than slowly induced hypothermia with ECLHA (SHE) in dogs. METHODS: Fifteen mongrel female dogs were divided into two groups: an RHE (n = 7) and an SHE (n = 8) group. Normothermic ventricular fibrillation was induced for 15 min and the animals were resuscitated by ECLHA. Rapid hypothermia was induced with a heat exchanger added to the ECLHA circuit in the RHE group, and by immersing the drainage tube of the ECLHA circuit in an ice water bath in the SHE group. Hypothermia (33 degrees C) was maintained for 20 h. The dogs were weaned from ECLHA at 24 h after resuscitation and treated for 96 h; neurological deficit scores (NDS) were measured throughout this period. RESULTS: It took 1.6+/-0.8 min to reach 33 degrees C in the RHE group and 49.5+/-12.1 min to reach 33 degrees C in the SHE group. There was no difference in survival rate between the two groups. The NDS at 96 h in the RHE group was better than that in the SHE group (26% (range: 10-28%) versus 32% (26-37%); p < 0.05) although there was no significant difference in NDS between the two groups until 72 h. CONCLUSION: Rapid hypothermic induction might be an important factor to improve neurological outcomes in prolonged CA models.     

Cerebral Cortical Aquaporin-4 Expression in Brain Edema following Cardiac Arrest in Rats

OBJECTIVES: Brain edema occurs following clinical as well as experimental cardiac arrest (CA) and predicts a poor neurologic outcome. The objective of this study was to determine the expression of cerebral cortex aquaporin (AQP)-4, a member of a family of membrane water-channel proteins, in brain edema formation following normothermic or hypothermic CA. METHODS: Twenty-four rats were subjected to time-matched normothermic (N-Sham, 37.5 degrees C +/- 0.5 degrees C, n = 6) or hypothermic (H-Sham, 34 degrees C +/- 0.5 degrees C, n = 6) sham experiments and normothermic (N-CA, n = 6) or hypothermic (H-CA, n = 6) CA induced by asphyxiation for 8 minutes. Hypothermia was induced before CA. The animals were resuscitated with cardiopulmonary resuscitation, ventilation, and epinephrine administration. Brain edema was determined by brain wet-to-dry weight ratio at one hour of resuscitation. AQP4 immunoactivity in the cerebral cortex was determined using immunohistochemical staining and was semiquantified as an intensity of staining with an automated cell imaging system. RESULTS: Mild hypothermia in the sham experiments did not alter cerebral cortex AQP4 immunoactivity (mean +/- SD) (55.0 +/- 3.7 in H-Sham vs. 53.3 +/- 1.7 in N-Sham, p > 0.05). N-CA resulted in a significant increase in AQP4 immunoactivity (61.8 +/- 4.5) compared with N-Sham (p = 0.01) and H-Sham (p = 0.03). H-CA attenuated AQP4 compared with N-CA (53.4 +/- 1.3, p = 0.01). Brain wet-to-dry weight ratios were 4.41 +/- 0.07 in N-Sham, 4.40 +/- 0.08 in H-Sham (p > 0.05 vs. N-Sham), 4.55 +/- 0.04 in N-CA (p = 0.004 vs. N-Sham; p = 0.005 vs. H-Sham), and 4.43 +/- 0.09 in H-CA (p = 0.02 vs. N-CA; p > 0.05 vs. N-Sham and H-Sham). CONCLUSIONS: Cerebral cortical AQP4 expression is up-regulated after normothermic CA, which is attenuated by hypothermia induced before CA.     

Study of the relationship between brain injury and glucose metabolism in rat model of cardiac arrest北大核心CSCD

Objective To determine the relationship between brain injury and cerebral glucose metabolism in rat model of cardiac arrest. Methods Asphyxia-induced cardiac arrest model was established. Forty-two male Wistar rats were randomly assigned to sham or experimental groups. Rats in the CA4,CA6 and CA8 group were treated with cardiopulmonary resuscitation(CPR) 4 min, 6 min and 8 min after cardiac arrest, respectively. The maximum standardized uptake value (SUV^J of glucose was detected by PET, and neural deficit score (NDS) were evaluated at 24 h and 72 h after ROSC. The numbers of injured neurons and apoptotic cells and the protein level of hexokmase I (HXK I) were measured at 72 h after ROSC. Results SUV, NDS and the level of HXK I were all decreased after ROSC, and interestingly, this declination of these markers was conelated with the prolongation of the duration of CA, the longer duration of CA the more declination of these biomarkers. Accordingly, the number of injured neurons and apoptotic cells increased were correlated with duration of CA, and thus CA8 group had greater numbers of those cells than CA6 group and CA4 group (P<0.05),and CA6 group had greater numbers of those cells than CA4 group(P<0.05). In addition, the SUV, was positively correlated with NDS (P<0.05), and negatively correlated with the numbers of injured neurons and apoptotic index(P<0.05). Conclusions The degree of brain injury is associated with cerebral glucose metabolism, and PET may become a novel method to assess the severity of brain damage after CA. © 2018 Chinese Medical Association. All rights reserved.     

Effect of valproic acid on survival and neurologic outcomes in an asphyxial cardiac arrest model of rats

Aim of the study

Valproic acid (VPA) has been known to reduce neuronal injury, has anti-inflammatory and anti-apoptotic effects as a histone deacetylase (HDAC) inhibitor. Thus, this study was performed to investigate the effects of VPA on survival and neurological outcomes in an asphyxial cardiac arrest model of rats.

Methods

Male Sprague-Dawley rats were subjected to asphyxial cardiac arrest. For survival study, rats were subjected to 450 s of asphyxial cardiac arrest. Cardiopulmonary resuscitation (CPR) was performed and then rats were blindly allocated to one of two groups (control group, n = 10; VPA group, n = 10). Valproic acid (300 mg kg⁻¹) or vehicle (normal saline) was administered via tail vein immediately after return of spontaneous circulation (ROSC) and observed for 72 h. For neurological outcome study, rats (n = 7 for each group) were subjected to same experimental procedures except duration of cardiac arrest of 360 s. Neurological deficit scale (NDS) score was measured every 24 h after ROSC for 72 h and was ranged from 0 (brain dead) to 80 (normal). Brain tissues were harvested at 72 h for evaluation of apoptotic injury and acetylation status of histone H3.

Results

In survival study, 2 rats in VPA group were excluded because cardiac arrest was not achieved in predetermined time. Thus, 10 rats were allocated to control group and 8 rats were allocated to VPA group. The survival rates at 72 h after cardiac arrest were significantly higher in VPA group than in control group (6/8 in VPA group, 3/10 rats in control group; log rank test, p < 0.05). In neurological outcome study, all rats survived for 72 h and NDS at 72 h were significantly higher in VPA group than in control group (p < 0.05). In brain tissues, expressions of acetylated histone H3 were not significantly different. However, expressions of cleaved caspase-3 were significantly lower in VPA group than in control group (p < 0.05).

Conclusion

VPA increased survival rates and improved neurologic outcome in asphyxial cardiac arrest model of rats while decreasing expressions of cleaved caspase-3.     

Comparison of the Effects of Hypothermia at 33°C or 35°C after Cardiac Arrest in Rats

Objectives: Hypothermia of 32°C–34°C induced after resuscitation from cardiac arrest improves neurologic recovery, but the optimal depth of cooling is unknown. Using a rat model, the authors tested the hypothesis that cooling to 35°C between hours 1 and 24 after resuscitation would improve neurologic outcome as much as cooling to 33°C.
Methods: Halothane-anesthetized rats ( n = 38) underwent 8 minutes of asphyxial cardiac arrest and resuscitation. Cranial temperature was maintained at 37°C before, during, and after arrest. Between one and 24 hours after resuscitation, cranial temperature was maintained at 33°C, 35°C, or 37°C using computer-controlled cooling fans and heating lamps. Neurologic scores were measured daily, and rats were killed at 14 days for histologic analysis. Neurons per high-powered field were counted in the CA1 region of the anterior hippocampus using neuronal nuclear antigen staining.
Results: After 14 days, 12 of 12 rats (100%) cooled to 33°C, 11 of 12 rats (92%) cooled to 35°C, and ten of 14 rats (71%) cooled to 37°C survived, with hazard of death greater in the rats cooled to 37°C than in the combined hypothermia groups. Neurologic scores were worse in the rats cooled to 37°C than in the hypothermia groups on days 1, 2, and 3. Numbers of surviving neurons were similar between the groups cooled to 33°C and 35°C and were higher than in the group cooled to 37°C.
Conclusions: These data illustrate that hypothermia of 35°C or 33°C over the first day of recovery improves neurologic scores and neuronal survival after cardiac arrest in rats. The benefit of induced hypothermia of 35°C appears to be similar to the benefit of 33°C.     

高渗盐对心搏骤停鼠脑复苏的作用

目的研究高渗盐对心搏骤停复苏后脑组织的保护作用及其机制,探讨脑复苏治疗的有效方法。方法大鼠窒息导致心搏骤停模型复制成功后,实验两组于复苏即刻分别静脉注射生理盐水、10%高渗盐,比较两组大鼠复苏前及复苏后各时间点平均动脉压值、自主循环恢复(ROSC)时间、动脉血与脑匀浆丙二醛(MDA)、脑干湿质量比、神经功能缺损评分(NDS)及脑海马组织病理改变。结果两组大鼠复苏前平均动脉压值差异无统计学意义(P>0.05),而复苏后各时间点平均动脉压值高渗盐组均高于对照组(P<0.05);高渗盐组较对照组能显著改善自主循环恢复时间(P<0.01),提高24、48hNDS(P<0.05),减轻大脑湿质量(P<0.01)及减轻脑组织病理损伤;但对1h动脉血MDA及24h脑匀浆MDA无作用。结论静脉注射10%高渗盐能减轻大鼠心搏骤停复苏后脑组织损伤,改善脑功能。