The cerebral 'no-reflow' phenomenon after cardiac arrest in rats--influence of low-flow reperfusion

Improving Outcomes After Post-Cardiac Arrest Brain Injury: A Scientific Statement From the International Liaison Committee on Resuscitation

This scientific statement presents a conceptual framework for the pathophysiology of post-cardiac arrest brain injury, explores reasons for previous failure to translate preclinical data to clinical practice, and outlines potential paths forward. Post-cardiac arrest brain injury is characterized by 4 distinct but overlapping phases: ischemic depolarization, reperfusion repolarization, dysregulation, and recovery and repair. Previous research has been challenging because of the limitations of laboratory models; heterogeneity in the patient populations enrolled; overoptimistic estimation of treatment effects leading to suboptimal sample sizes; timing and route of intervention delivery; limited or absent evidence that the intervention has engaged the mechanistic target; and heterogeneity in postresuscitation care, prognostication, and withdrawal of life-sustaining treatments. Future trials must tailor their interventions to the subset of patients most likely to benefit and deliver this intervention at the appropriate time, through the appropriate route, and at the appropriate dose. The complexity of post-cardiac arrest brain injury suggests that monotherapies are unlikely to be as successful as multimodal neuroprotective therapies. Biomarkers should be developed to identify patients with the targeted mechanism of injury, to quantify its severity, and to measure the response to therapy. Studies need to be adequately powered to detect effect sizes that are realistic and meaningful to patients, their families, and clinicians. Study designs should be optimized to accelerate the evaluation of the most promising interventions. Multidisciplinary and international collaboration will be essential to realize the goal of developing effective therapies for post-cardiac arrest brain injury.

COMBINATION OF HYPEROXYGENATION AND TARGETED TEMPERATURE MANAGEMENT IMPROVES FUNCTIONAL OUTCOMES OF POST CARDIAC ARREST SYNDROME IRRESPECTIVE OF CAUSES OF ARREST IN RATS

ABSTRACT

Background: The high mortality rates of patients who are resuscitated from cardiac arrest (CA) are attributed to post cardiac arrest syndrome (PCAS). This study evaluated the effect of hyperoxygenation and targeted temperature management (TTM) on PCAS in rats with different causes of CA. Methods and Results: One hundred sixty-eight Sprague-Dawley rats were equally divided into asphyxial and dysrhythmic groups. Animals were further randomized into four subgroups immediately after resuscitation: normoxia-normothermia (NO-NT), ventilated with 21% oxygen under normothermia; hyperoxia-normothermia (HO-NT), ventilated with 100% oxygen for 3 hours under normothermia; normoxia-hypothermia (NO-HT), ventilated with 21% oxygen for 3 hours under hypothermia; and hyperoxia-hypothermia (HO-HT), ventilated with 100% oxygen for 3 hours under hypothermia. Post resuscitation cardiac dysfunction, neurological recovery, and pathological analysis were assessed. For asphyxial CA, HO-NT and HO-HT (68.8% and 75.0%) had significantly higher survival than NO-NT and NO-HT (31.3% and 31.3%). For dysrhythmic CA, NO-HT and HO-HT (81.3% and 87.5%) had significantly higher survival than NO-NT and HO-NT (44.0% and 50.0%). When all of the rats were considered, the survival rate was much higher in HO-HT (81.3%). Compared with NO-NT (57.7% ± 14.9% and 40.3% ± 7.8%), the collagen volume fraction and the proportion of fluoro-jade B-positive area in HO-HT (14.0% ± 5.7% and 28.0% ± 13.3%) were significantly reduced. Conclusion: The beneficial effects of hyperoxygenation and TTM are dependent on the cause of arrest: hyperoxygenation benefits asphyxial, whereas TTM benefits dysrhythmic CA. The combination of hyperoxygenation and TTM could effectively improve the functional outcome of PCAS regardless of the cause of CA.

Optimal inhaled oxygen and carbon dioxide concentrations for post-cardiac arrest cerebral reoxygenation and neurological recovery

Prolonged cerebral hypoperfusion after the return of spontaneous circulation (ROSC) from cardiac arrest (CA) may lead to poor neurological recovery. In a 7-min asphyxia-induced CA rat model, four combinations of inhaled oxygen (iO2) and carbon dioxide (iCO2) were administered for 150 min post-ROSC and compared in a randomized animal trial. At the end of administration, the partial pressure of brain tissue oxygenation (PbtO2) monitored in the hippocampal CA1 region returned to the baseline for the 88% iO2 [ΔPbtO2, median: -0.39 (interquartile range: 5.6) mmHg] and 50% iO2 [ΔpbtO2, -2.25 (10.9) mmHg] groups; in contrast, PbtO2 increased substantially in the 88% iO2+12% iCO2 [ΔpbtO2, 35.05 (16.0) mmHg] and 50% iO2+12% iCO2 [ΔpbtO2, 42.03 (31.7) mmHg] groups. Pairwise comparisons (post hoc Dunn's test) indicated the significant role of 12% iCO2 in augmenting PbtO2 during the intervention and improving neurological recovery at 24 h post-ROSC. Facilitating brain reoxygenation may improve post-CA neurological outcomes.

Coagulofibrinolytic effects of recombinant soluble thrombomodulin in prolonged porcine cardiac arrest

Aim

To evaluate coagulofibrinolytic abnormalities and the effects of ART-123 (recombinant human thrombomodulin alpha) in a porcine model of cardiac arrest and prolonged cardiopulmonary resuscitation (CA/CPR).

Methods

Fifteen pigs (n = 5 per group) underwent 8 minutes of no-flow CA followed by 50 minutes of mechanical CPR, while 2 pigs underwent sham arrest. CA/CPR animals were randomized to receive saline or 1 mg/kg ART-123 pre-arrest (5 minutes prior to ventricular fibrillation) or post-arrest (2 minutes after initiation of CPR). Arterial and venous blood samples were drawn at multiple time points for blood gas analysis and measurement of plasma and whole blood markers of coagulation and fibrinolysis.

Results

In saline-treated CA/CPR, but not sham animals, robust and persistent activation of coagulation and fibrinolysis was observed throughout resuscitation. After 50 minutes of CPR, plasma tests and thromboelastography indicated a mix of hypercoagulability and consumptive coagulopathy. ART-123 had a robust anticoagulant effect, reducing both thrombin-antithrombin (TAT) complexes and d-dimer (p < 0.05 for each). The duration of anticoagulant effect varied depending on the timing of ART-123 administration. Similarly, ART-123 when given prior to cardiac arrest was found to have pro-fibrinolytic effects, increasing free tissue plasminogen activator (tPA, p = 0.02) and decreasing free plasminogen activator inhibitor-1 (PAI-1, p = 0.04).

Conclusion

A porcine model of prolonged CA/CPR reproduces many of the coagulofibrinolytic abnormalities observed in human cardiac arrest patients. ART-123 demonstrates a combination of anticoagulant and profibrinolytic effects, depending on the timing of its administration relative to cardiac arrest.

Cerebral hemodynamics after cardiac arrest: implications for clinical management

Following resuscitation from cardiac arrest, hypoxic ischemic brain injury (HIBI) ensues, which is the primary determinant of adverse outcome. The pathophysiology of HIBI can be compartmentalized into primary and secondary injury, resulting from cerebral ischemia during cardiac arrest and reperfusion following successful resuscitation, respectively. During the secondary injury phase, increased attention has been directed towards the optimization of cerebral oxygen delivery to prevent additive injury to the brain. During this phase, cerebral hemodynamics are characterized by early hyperemia following resuscitation and then a protracted phase of cerebral hypoperfusion termed "no-reflow" during which additional hypoxic-ischemic injury can occur. As such, identification of therapeutic strategies to optimize cerebral delivery of oxygen is at the forefront of HIBI research. Unfortunately, randomized control trials investigating the manipulation of arterial carbon dioxide tension and mean arterial pressure augmentation as methods to potentially improve cerebral oxygen delivery have shown no impact on clinical outcomes. Emerging literature suggests differential patient-specific phenotypes may exist in patients with HIBI. The potential to personalize therapeutic strategies in the critical care setting based upon patient-specific pathophysiology presents an attractive strategy to improve HIBI outcomes. Herein, we review the cerebral hemodynamic pathophysiology of HIBI, discuss patient phenotypes as it pertains to personalizing care, as well as suggest future directions.

Association of prehospital hypotension depth and dose with survival following out-of-hospital cardiac arrest

INTRODUCTION

Hypotension following resuscitation from out-of-hospital cardiac arrest (OHCA) may cause harm by exacerbating secondary brain injury; however, limited research has explored this relationship. Our objective was to examine the association between duration and depth of prehospital post return of spontaneous circulation (ROSC) hypotension and survival.

METHODS

We utilized the 2019 and 2020 ESO Data Collaborative public use research data sets for this study (ESO, Austin, TX). Hypotension dose (mmHg*min.), average prehospital systolic blood pressure (SBP), and lowest recorded prehospital SBP were calculated. The association of these measures with survival to home (STH) and rearrest were explored using multivariable logistic regression. Time to hypotension resolution analyses by hypotension management strategy (push dose vasopressors, vasopressor infusion, or fluid only) were conducted using adjusted Cox proportional hazards models.

RESULTS

17,280 OHCA patients met inclusion criteria, of which 3,345 had associated hospital outcome data. Over one-third (37.8%; 6,526/17,280) of all patients had at least one recorded SBP below 90 mmHg. When modeled continuously, average prehospital SBP (1.19 [1.15, 1.23] per 10 mmHg), lowest prehospital SBP (1.20 [1.17, 1.24] per 10 mmHg), and hypotension dose (0.995 [0.993, 0.996] per mmHg*min.) were independently associated with STH. Differences in hypotension management were not associated with differences in survival or time to hypotension resolution.

CONCLUSION

Severity and duration of hypotension were significantly associated with worse outcomes in this dataset. Defining a threshold for hypotension requiring treatment above the classical SBP threshold of 90 mmHg may be warranted in the setting of prehospital post-resuscitation care.

Inhaled Carbon Dioxide Improves Neurological Outcomes by Downregulating Hippocampal Autophagy and Apoptosis in an Asphyxia‐Induced Cardiac Arrest and Resuscitation Rat Model

Background

Protracted cerebral hypoperfusion following cardiac arrest (CA) may cause poor neurological recovery. We hypothesized that inhaled carbon dioxide (CO₂) could augment cerebral blood flow (CBF) and improve post‐CA neurological outcomes.

Methods and Results

After 6‐minute asphyxia‐induced CA and resuscitation, Wistar rats were randomly allocated to 4 groups (n=25/group) and administered with different inhaled CO₂ concentrations, including control (0% CO₂), 4% CO₂, 8% CO₂, and 12% CO₂. Invasive monitoring was maintained for 120 minutes, and neurological outcomes were evaluated with neurological function score at 24 hours post‐CA. After the 120‐minute experiment, CBF was 242.3% (median; interquartile range, 221.1%–267.4%) of baseline in the 12% CO₂ group while CBF fell to 45.8% (interquartile range, 41.2%–58.1%) of baseline in the control group (P<0.001). CBF increased along with increasing inhaled CO₂ concentrations with significant linear trends (P<0.001). At 24 hours post‐CA, compared with the control group (neurological function score, 9 [interquartile range, 8–9]), neurological recovery was significantly better in the 12% CO₂ group (neurological function score, 10 [interquartile range, 9.8–10]) (P<0.001) while no survival difference was observed. Brain tissue malondialdehyde (P=0.02) and serum neuron‐specific enolase (P=0.002) and S100β levels (P=0.002) were significantly lower in the 12% CO₂ group. TUNEL (terminal deoxynucleotidyl transferase–mediated biotin–deoxyuridine triphosphate nick‐end labeling)‐positive cell densities in hippocampal CA1 (P<0.001) and CA3 (P<0.001) regions were also significantly reduced in the 12% CO₂ group. Western blotting showed that beclin‐1 (P=0.02), p62 (P=0.02), and LAMP2 (lysosome‐associated membrane protein 2) (P=0.01) expression levels, and the LC3B‐II:LC3B‐I ratio (P=0.02) were significantly lower in the 12% CO₂ group.

Conclusions

Administering inhaled CO₂ augmented post‐CA CBF, mitigated oxidative brain injuries, ameliorated neuronal injury, and downregulated apoptosis and autophagy, thereby improving neurological outcomes.

Brain injury in extracorporeal cardiopulmonary resuscitation: translational to clinical research

The addition of extracorporeal membrane oxygenation (ECMO) to conventional cardiopulmonary resuscitation (CPR), termed extracorporeal cardiopulmonary resuscitation (ECPR), has significantly improved survival in selected patient populations. Despite this advancement, significant neurological impairment persists in approximately half of survivors. ECPR represents a potential advancement for patients who experience refractory cardiac arrest (CA) due to a reversible etiology and do not regain spontaneous circulation. Important risk factors for acute brain injury (ABI) in ECPR include lack of perfusion, reperfusion, and altered cerebral autoregulation. The initial hypoxic-ischemic injury caused by no-flow and low-flow states after CA and during CPR is compounded by reperfusion, hyperoxia during ECMO support, and nonpulsatile blood flow. Additionally, ECPR patients are at risk for Harlequin syndrome with peripheral cannulation, which can lead to preferential perfusion of cerebral vessels with deoxygenated blood. Lastly, the oxygenator membrane is prothrombotic and requires systemic anticoagulation. The two competing phenomena result in thrombus formation, hemolysis, and thrombocytopenia, increasing the risk of ischemic and hemorrhagic ABI. In addition to clinical studies, we assessed available ECPR animal models to identify the mechanisms underlying ABI at the cellular level. Standardized multimodal neurological monitoring may facilitate early detection of and intervention for ABI. With the increasing use of ECPR, it is critical to understand the pathophysiology of ABI, its prevention, and the management strategies for improving the outcomes of ECPR. Translational and clinical research focusing on acute ABI immediately after ECMO cannulation and its short- and long-term neurological outcomes are warranted.

Updates on the Management of Neurologic Complications of Post-Cardiac Arrest Resuscitation

Sudden cardiac arrest (SCA) is one of the leading causes of mortality and morbidity in the United States, and survivors are frequently left with severe disability. Of the 10% successfully resuscitated from SCA, only around 10% of these live with a favorable neurologic outcome. Survivors of SCA commonly develop post-cardiac arrest syndrome (PCAS). PCAS is composed of neurologic, myocardial, and systemic injury related to inadequate perfusion and ischemia-reperfusion injury with free radical formation and an inflammatory cascade. While targeted temperature management is the cornerstone of therapy, other intensive care unit-based management strategies include monitoring and treatment of seizures, cerebral edema, and increased intracranial pressure, as well as prevention of further neurologic injury. In this review, we discuss the scientific evidence, recent updates, future prospects, and knowledge gaps in the treatment of post-cardiac arrest patients.

Regional cerebral oxygen saturation in cardiac arrest survivors undergoing targeted temperature management 36℃ versus 33℃: A randomized clinical trial

AIM

of study To investigate whether regional cerebral oxygen saturation (rSO₂) differs in out-of-hospital cardiac arrest (OHCA) survivors undergoing targeted temperature management (TTM) 36℃ versus 33℃.

METHODS

A randomized clinical trial was conducted at intensive care units in two referral hospitals. Fifty-seven comatose OHCA survivors were randomized into either a 36℃ or 33℃ group. Patients were cooled and maintained at an oesophageal temperature of either 36℃ or 33℃ for 24 hours, rewarmed at a rate of 0.25℃/hour, and maintained at < 37.5℃ until 72 hours. During 72 hours of TTM, rSO₂ was continuously monitored on the left forehead using near-infrared spectroscopy (INVOS^TM 5100C). The rSO₂ level at 72 hours was compared between the two groups. Next, serial rSO₂ levels for 72 hours were compared using mixed effects regression. The association between rSO₂ levels and 6-month neurological outcomes was also evaluated.

RESULTS

There were no significant differences in the rSO₂ level at 72 hours between the 36℃ and 33℃ groups (p = 0.372). Furthermore, serial rSO₂ levels for 72 hours of TTM were not different between the two groups (p = 0.733). However, low rSO₂ levels, particularly at 24 hours of TTM, were significantly associated with poor 6-month neurological outcomes (odds ratio = 0.899, 95% confidence interval: 0.831 - 0.974). The area under the receiver operating characteristic curve of the rSO₂ level at 24 hours for poor neurological outcomes was 0.800.

CONCLUSIONS

Regardless of target temperatures, low rSO₂ levels during TTM were significantly associated with poor 6-month neurological outcomes in OHCA survivors.

Oxygen administration in patients recovering from cardiac arrest: a narrative review

High oxygen tension in blood and/or tissue affects clinical outcomes in several diseases. Thus, the optimal target PaO₂ for patients recovering from cardiac arrest (CA) has been extensively examined. Many patients develop hypoxic brain injury after the return of spontaneous circulation (ROSC); this supports the need for oxygen administration in patients after CA. Insufficient oxygen delivery due to decreased blood flow to cerebral tissue during CA results in hypoxic brain injury. By contrast, hyperoxia may increase dissolved oxygen in the blood and, subsequently, generate reactive oxygen species that are harmful to neuronal cells. This secondary brain injury is particularly concerning. Although several clinical studies demonstrated that hyperoxia during post-CA care was associated with poor neurological outcomes, considerable debate is ongoing because of inconsistent results. Potential reasons for the conflicting results include differences in the definition of hyperoxia, the timing of exposure to hyperoxia, and PaO₂ values used in analyses. Despite the conflicts, exposure to PaO₂ > 300 mmHg through administration of unnecessary oxygen should be avoided because no obvious benefit has been demonstrated. The feasibility of titrating oxygen administration by targeting SpO₂ at approximately 94% in patients recovering from CA has been demonstrated in pilot randomized controlled trials (RCTs). Such protocols should be further examined.

Cerebral Blood Flow-Guided Manipulation of Arterial Blood Pressure Attenuates Hippocampal Apoptosis After Asphyxia-Induced Cardiac Arrest in Rats

Background In most post-cardiac arrest patients, the autoregulation mechanism of cerebral blood flow (CBF) is dysregulated. We examined whether recovery of CBF by adjusting mean arterial pressure mitigates post-cardiac arrest neuronal damage. Methods and Results Wistar rats that underwent 8-minute asphyxia-induced cardiac arrest and resuscitation were computer-randomized to norepinephrine or control groups. The CBF was measured at the dorsal hippocampal CA1 region of the left hemisphere. In the norepinephrine group, the mean arterial pressure was adjusted to recover CBF to 80% to 100% of baseline. Twenty-four hours following resuscitation, neurological outcomes were assessed, and brain tissues and blood samples were harvested for neuronal apoptosis and injury assessment. Thirty resuscitated rats were randomized into 2 groups, each containing 12 rats that completed the experiments. Norepinephrine infusion effectively prevented posthyperemia hypoperfusion and recovered CBF to pre-arrest baseline levels; a moderate positive linear correlation between mean arterial pressure and CBF during this period was also observed (P<0.001). There were no significant between-group differences in neurological recovery. In the norepinephrine group compared with the control group, upregulated cleaved caspase-3 protein expression in brain tissue determined by Western blot was reduced (P=0.02) and the densities of apoptotic cells in hippocampal CA1 and CA3 regions determined by terminal deoxynucleotidyl transferase-mediated dUTP biotin nick-end labeling were decreased (P<0.001). No significant differences in serum neuron-specific enolase or S100β levels were detected between the 2 groups. Conclusions CBF recovery demonstrated neuroprotective effects by reducing activation of cerebral apoptosis and number of apoptotic neurons. However, these effects did not significantly improve clinical neurological function, necessitating further investigation.

Therapeutic hypothermia promotes cerebral blood flow recovery and brain homeostasis after resuscitation from cardiac arrest in a rat model

Laboratory and clinical studies have demonstrated that therapeutic hypothermia (TH), when applied as soon as possible after resuscitation from cardiac arrest (CA), results in better neurological outcome. This study tested the hypothesis that TH would promote cerebral blood flow (CBF) restoration and its maintenance after return of spontaneous circulation (ROSC) from CA. Twelve Wistar rats resuscitated from 7-min asphyxial CA were randomized into two groups: hypothermia group (7 H, n = 6), treated with mild TH (33-34℃) immediately after ROSC and normothermia group (7 N, n = 6,37.0 ± 0.5℃). Multiple parameters including mean arterial pressure, CBF, electroencephalogram (EEG) were recorded. The neurological outcomes were evaluated using electrophysiological (information quantity, IQ, of EEG) methods and a comprehensive behavior examination (neurological deficit score, NDS). TH consistently promoted better CBF restoration approaching the baseline levels in the 7 H group as compared with the 7 N group. CBF during the first 5-30 min post ROSC of the two groups was 7 H:90.5% ± 3.4% versus 7 N:76.7% ± 3.5% (P < 0.01). Subjects in the 7 H group showed significantly better IQ scores after ROSC and better NDS scores at 4 and 24 h. Early application of TH facilitates restoration of CBF back to baseline levels after CA, which in turn results in the restoration of brain electrical activity and improved neurological outcome.

Establishing a Rodent Model of Ventricular Fibrillation Cardiac Arrest With Graded Histologic and Neurologic Damage With Different Cardiac Arrest Durations

Purpose:

The aim of the study was to establish a ventricular fibrillation (VF) cardiac arrest (CA) resuscitation model with consistent neurologic and neuropathologic damage as potential therapeutic target.

Methods:

Prospectively randomized groups of experiments in two phases. In phase 1 four groups of male Sprague–Dawley rats (n = 5) were resuscitated after 6 min VFCA with 2 and 6 min basic life support durations (BLS) with and without adrenaline. In phase 2 the most promising group regarding return of spontaneous circulation (ROSC) and survival was compared with a group of 8 min CA. Resuscitability, neurologic deficit scores (NDS), and overall performance category (OPC) were assessed daily; histolopathology of the hippocampal CA1 region [hematoxylin and eosin- (viable neurons), Fluoro-Jade- (dying neurons), and Iba-1 immunostaining (microglial activation–semiquantitative)] on day 14.

Results:

Two minutes BLS and with adrenaline as most promising group of phase 1 compared with an 8 min group in phase 2 exhibited ROSC in 8 (80%) vs. 9 (82%) animals and survivors till day 14 in 7 (88%) (all OPC 1, NDS 0 ± 0) vs. 6 (67%) (5 OPC 1, 1 OPC 2, NDS 0.83 ± 2.4) animals. OPC and NDS were only significantly different at day 1 (OPC: P = 0.035; NDS: P = 0.003). Histopathologic results between groups were not significantly different; however, a smaller variance of extent of lesions was found in the 8 min group. Both CA durations caused graded neurologic, overall, such as histopathologic damage.

Conclusions:

This dynamic global ischemia model offers the possibility to evaluate further cognitive and novel neuroprotective therapy testing after CA.

Comparison of Quantitative Characteristics of Early Post-resuscitation EEG Between Asphyxial and Ventricular Fibrillation Cardiac Arrest in Rats

BACKGROUND

Quantitative electroencephalogram (EEG) analysis has shown promising results in studying brain injury and functional recovery after cardiac arrest (CA). However, whether the quantitative characteristics of EEG, as potential indicators of neurological prognosis, are influenced by CA causes is unknown. The purpose of this study was designed to compare the quantitative characteristics of early post-resuscitation EEG between asphyxial CA (ACA) and ventricular fibrillation CA (VFCA) in rats.

METHODS

Thirty-two Sprague-Dawley rats of both sexes were randomized into either ACA or VFCA group. Cardiopulmonary resuscitation was initiated after 5-min untreated CA. Characteristics of early post-resuscitation EEG were compared, and the relationships between quantitative EEG features and neurological outcomes were investigated.

RESULTS

Compared with VFCA, serum level of S100B, neurological deficit score and brain histopathologic damage score were dramatically higher in the ACA group. Quantitative measures of EEG, including onset time of EEG burst, time to normal trace, burst suppression ratio, and information quantity, were significantly lower for CA caused by asphyxia and correlated with the 96-h neurological outcome and survival.

CONCLUSIONS

Characteristics of earlier post-resuscitation EEG differed between cardiac and respiratory causes. Quantitative measures of EEG not only predicted neurological outcome and survival, but also have the potential to stratify CA with different causes.

Niacin and Selenium Attenuate Brain Injury After Cardiac Arrest in Rats by Up-Regulating DJ-1-Akt Signaling

OBJECTIVES

To determine neuroprotective effects and mechanism of the combination therapy of niacin and selenium in cardiac arrest rats.

DESIGN

Prospective laboratory study.

SETTING

University laboratory.

SUBJECTS

Rat cortex neurons and male Sprague-Dawley rats (n = 68).

INTERVENTIONS

In rat cortex neurons underwent 90 minutes of oxygen-glucose deprivation and 22.5 hours of reoxygenation, effects of the combination therapy of niacin (0.9 mM) and selenium (1.5 μM) were investigated. The role of DJ-1 was determined using DJ-1 knockdown cells. In cardiac arrest rats, posttreatment effects of the combination therapy of niacin (360 mg/kg) and selenium (60 μg/kg) were evaluated.

MEASUREMENTS AND MAIN RESULTS

In oxygen-glucose deprivation and 22.5 hours of reoxygenation cells, combination therapy synergistically activated the glutathione redox cycle by a niacin-induced increase in glutathione reductase and a selenium-induced increase in glutathione peroxidase activities and reduced hydrogen peroxide level. It increased phosphorylated Akt and intranuclear Nuclear factor erythroid 2-related factor 2 expression and attenuated neuronal injury. However, these benefits were negated by DJ-1 knockdown. In cardiac arrest rats, combination therapy increased DJ-1, phosphorylated Akt, and intranuclear nuclear factor erythroid 2-related factor 2 expression, suppressed caspase 3 cleavage, and attenuated histologic injury in the brain tissues. It also improved the 7-day Neurologic Deficit Scales from 71.5 (66.0-74.0) to 77.0 (74.-80.0) (p = 0.02).

CONCLUSIONS

The combination therapy of clinically relevant doses of niacin and selenium attenuated brain injury and improved neurologic outcome in cardiac arrest rats. Its benefits were associated with reactive oxygen species reduction and subsequent DJ-1-Akt signaling up-regulation.

Disseminated intravascular coagulation in cardiac arrest and resuscitation

The aims of this review are to demonstrate that the changes in coagulation and fibrinolysis observed in cardiac arrest and resuscitation can be recognized as disseminated intravascular coagulation (DIC), and to discuss the probability of DIC being a therapeutic target. The appearance of triggers of DIC, such as damage-associated molecular patterns, inflammatory cytokines, and adrenaline, is associated with platelet activation, marked thrombin generation and fibrin formation, insufficient anticoagulation pathways, and increased fibrinolysis by tissue-type plasminogen activator, followed by the suppression of fibrinolysis by plasminogen activator inhibitor-1, in patients with cardiac arrest and resuscitation. Simultaneous neutrophil activation and endothelial injury associated with glycocalyx perturbation have been observed in these patients. The degree of these changes is more severe in patients with prolonged precardiac arrest hypoxia and long no-flow and low-flow times, patients without return of spontaneous circulation, and non-survivors. Animal and clinical studies have confirmed decreased cerebral blood flow and microvascular fibrin thrombosis in vital organs, including the brain. The clinical diagnosis of DIC in patients with cardiac arrest and resuscitation is associated with multiple organ dysfunction, as assessed with the sequential organ failure assessment score, and increased mortality. This review confirms that the coagulofibrinolytic changes in cardiac arrest and resuscitation meet the definition of DIC proposed by the ISTH, and that DIC is associated with organ dysfunction and poor patient outcomes. This evidence implies that established DIC should be considered to be one of the main therapeutic targets in post-cardiac arrest syndrome.

Evaluation of small intestinal damage in a rat model of 6 Minutes cardiac arrest

BACKGROUND

Contribution of the small intestine to systemic inflammation after cardiac arrest (CA) is poorly understood. The objective was to evaluate whether an in vivo rat model of 6 min CA is suitable to initiate intestinal ischaemia-reperfusion-injury and to evaluate histomorphological changes and inflammatory processes in the small intestinal mucosa resp. in sera.

METHODS

Adult male Wistar rats were subjected to CA followed by cardio-pulmonary resuscitation. Proximal jejunum and serum was collected at 6 h, 24 h, 72 h and 7 d post return of spontaneous circulation (ROSC) and from a control group. The small intestine was evaluated histomorphologically. Cytokine concentrations were measured in jejunum lysates and sera.

RESULTS

Histomorphological evaluation revealed a significant increase in mucosal damage in the jejunum at all timepoints compared to controls (p < 0.0001). In jejunal tissues, concentrations of IL-1α, IL-1β, IL-10, and TNF-α showed significant peaks at 24 h and were 1.5- to 5.7-fold higher than concentrations at 6 h and in the controls (p < 0.05). In serum, a significant higher amount of cytokine was detected only for IL-1β at 24 h post-ROSC compared to controls (15.78 vs. 9.76 pg/ml).

CONCLUSION

CA resulted in mild small intestinal tissue damage but not in systemic inflammation. A rat model of 6 min CA is not capable to comprehensively mimic a post cardiac arrest syndrome (PCAS). Whether there is a vital influence of the intestine on the PCAS still remains unclear.

Individualized perfusion targets in hypoxic ischemic brain injury after cardiac arrest

Secondary injury is a major determinant of outcome in hypoxic ischemic brain injury (HIBI) after cardiac arrest and may be mitigated by optimizing cerebral oxygen delivery (CDO₂). CDO₂ is determined by cerebral blood flow (CBF), which is dependent upon mean arterial pressure (MAP). In health, CBF remains constant over the MAP range through cerebral autoregulation. In HIBI, the zone of intact cerebral autoregulation is narrowed and varies for each patient. Maintaining MAP within the intact autoregulation zone may mitigate ischemia, hyperemia and secondary injury. The optimal MAP in individual patients can be determined using real time autoregulation monitoring techniques.

An improved three-vessel occlusion model of global cerebral ischemia in rats

We developed an improved three-vessel occlusion model of global cerebral ischemia in rats. This method consists in cessation of cerebral blood flow by accessing a. carotis communis sinistra through the ventral surface of the neck as well as tr. brachiocephalicus and a. subclavia sinistra through the first intercostal space, bypassing the pleural cavity and excluding pneumothorax. After the occlusion of the vessels that resulted in interruption of their blood flow, according to laser-Doppler flowmetry, there was a sharp decline in local cerebral blood flow in the visual cortex to 4±1% of the initial level. After restoring the level of local cerebral blood flow at the 5th minute, 10th minute, 20th minute and 24th hour of reperfusion, the levels of local cerebral blood flow were 51±7%, 41±5%, 35±8% and 54±9% of the initial level, respectively. Histo-quantitative analysis of changes in neurons of the hippocampus of rats showed that after ischemic injury, the numerical density of neurons in hippocampal zone CA1 in the observed 1mm² region decreased by 29%, 22%, and 35%, respectively, compared to sham-operated animals (p<0.05). By the first day after global cerebral ischemia, the experimental group had shown a mean neurological deficit score equal to 7.5±1.0 and 7.9±0.7 points, followed by a decrease up to score 6.5±1.1 and 5.9±0.7 on the third day, 4.6±0.8 and 4.7±0.5 on the fifth day (on chloral hydrate and propofol anesthesia correspondently).

Clinical pathophysiology of hypoxic ischemic brain injury after cardiac arrest: a "two-hit" model

Hypoxic ischemic brain injury (HIBI) after cardiac arrest (CA) is a leading cause of mortality and long-term neurologic disability in survivors. The pathophysiology of HIBI encompasses a heterogeneous cascade that culminates in secondary brain injury and neuronal cell death. This begins with primary injury to the brain caused by the immediate cessation of cerebral blood flow following CA. Thereafter, the secondary injury of HIBI takes place in the hours and days following the initial CA and reperfusion. Among factors that may be implicated in this secondary injury include reperfusion injury, microcirculatory dysfunction, impaired cerebral autoregulation, hypoxemia, hyperoxia, hyperthermia, fluctuations in arterial carbon dioxide, and concomitant anemia.Clarifying the underlying pathophysiology of HIBI is imperative and has been the focus of considerable research to identify therapeutic targets. Most notably, targeted temperature management has been studied rigorously in preventing secondary injury after HIBI and is associated with improved outcome compared with hyperthermia. Recent advances point to important roles of anemia, carbon dioxide perturbations, hypoxemia, hyperoxia, and cerebral edema as contributing to secondary injury after HIBI and adverse outcomes. Furthermore, breakthroughs in the individualization of perfusion targets for patients with HIBI using cerebral autoregulation monitoring represent an attractive area of future work with therapeutic implications.We provide an in-depth review of the pathophysiology of HIBI to critically evaluate current approaches for the early treatment of HIBI secondary to CA. Potential therapeutic targets and future research directions are summarized.

Alterations in Cerebral Blood Flow after Resuscitation from Cardiac Arrest

Greater than 50% of patients successfully resuscitated from cardiac arrest have evidence of neurological disability. Numerous studies in children and adults, as well as in animal models have demonstrated that cerebral blood flow (CBF) is impaired after cardiac arrest. Stages of cerebral perfusion post-resuscitation include early hyperemia, followed by hypoperfusion, and finally either resolution of normal blood flow or protracted hyperemia. At the level of the microcirculation the blood flow is heterogeneous, with areas of no flow, low flow, and increased flow. CBF directed therapies in animal models of cardiac arrest improved neurological outcome, and therefore, the alterations in CBF after cardiac arrest likely contribute to the development of hypoxic ischemic encephalopathy. Current intensive care after cardiac arrest is centered upon maintaining systemic oxygenation, normal blood pressure values for age, maintaining general homeostasis, and avoiding hyperthermia. Assessment of CBF and oxygenation is not routinely performed after cardiac arrest. Currently available and underutilized techniques to assess cerebral perfusion include transcranial doppler, near-infrared spectroscopy, and arterial spin labeling magnetic resonance imaging. Limited clinical studies established the role of CBF and oxygenation monitoring in prognostication after cardiac arrest and few studies suggest that guiding critical care post-resuscitation to mean arterial pressures above the minimal autoregulatory range might improve outcome. Important knowledge gaps thus remain in cerebral monitoring and CBF and oxygen goal-directed therapies post-resuscitation from cardiac arrest.

Quantitative analysis of the capillary network of aged APPswe/PS1dE9 transgenic mice

A combination of immunohistochemical and stereological techniques were used to investigate the capillary network in the cerebral cortex of 18-month-old APPswe/PS1dE9 transgenic (Tg) mice and control littermates. Data regarding total capillary length, segment number, diffusion radius, and pericyte number are presented. The total length was 60 meters and there was a one-to-one relationship between the number of capillary segments and pericytes in both groups. Significant differences were not observed in the Tg and wild-type controls indicating that the Alzheimer's-like amyloidosis produced in this Tg mouse has a minimal affect on the structural integrity of the cerebral capillary network.

The pathophysiologies of asphyxial vs dysrhythmic cardiac arrest: implications for resuscitation and post-event management

BACKGROUND

Cardiac arrest is not a uniform condition and significant heterogeneity exists within all victims with regard to the cause of cardiac arrest. Primary cardiac (dysrhythmic) and asphyxial causes together are responsible for most cases of cardiac arrest at all age groups. The purpose of this article is to review the pathophysiologic differences between dysrhythmic and asphyxial cardiac arrest in the prearrest period, during the no-flow state, and after successful cardiopulmonary resuscitation.

METHODS

The electronic databases of PubMed/Medline, Scopus, and Cochrane were searched for relevant literature and studies.

RESULTS/DISCUSSION

Significant differences exist between dysrhythmic and asphyxial cardiac arrest regarding their pathophysiologic pathways and affect consequently the postresuscitation period. Laboratory data indicate that asphyxial cardiac arrest leads to more widespread postresuscitation brain damage compared with dysrhythmic cardiac arrest. Regarding postresuscitation myocardial dysfunction, few studies have addressed a comparison of the 2 conditions with controversial results.

CONCLUSIONS

Asphyxial cardiac arrest differs significantly from dysrhythmic cardiac arrest with regard to pathophysiologic mechanisms, neuropathologic damage, postresuscitation organ dysfunction, and response to therapy. Both conditions should be considered and treated in a different manner.

Do different anesthesia regimes affect hippocampal apoptosis and neurologic deficits in a rodent cardiac arrest model?

Background

Different anesthesia regimes are commonly used in experimental models of cardiac arrest, but the effects of various anesthetics on clinical outcome parameters are unknown. We conducted a study in which we subjected rats to cardiac arrest under medetomidine/ketamine or sevoflurane/fentanyl anesthesia.

Methods

Asystolic cardiac arrest for 8 minutes was induced in 73 rats with a mixture of potassium chloride and esmolol. Daily behavioral and neurological examination included the open field test (OFT), the tape removal test (TRT) and a neurodeficit score (NDS). Animals were randomized for sacrifice on day 2 or day 5 and brains were harvested for histology in the hippocampus cornus ammonis segment CA1. The inflammatory markers IL-6, TNF-α, MCP-1 and MIP-1α were assessed in cerebrospinal fluid (CSF). Proportions of survival were tested with the Fisher’s exact test, repeated measurements were assessed with the Friedman’s test; the baseline values were tested using Mann–Whitney U test and the difference of results of repeated measures were compared.

Results

In 31 animals that survived beyond 24 hours neither OFT, TRT nor NDS differed between the groups; histology was similar on day 2. On day 5, significantly more apoptosis in the CA1 segment of the hippocampus was found in the sevoflurane/fentanyl group. MCP-1 was higher on day 5 in the sevoflurane/fentanyl group (p = 0.04). All other cyto- and chemokines were below detection threshold.

Conclusion

In our cardiac arrest model neurological function was not influenced by different anesthetic regimes; in contrast, anesthesia with sevoflurane/fentanyl results in increased CSF inflammation and histologic damage at day 5 post cardiac arrest.

Effects of levosimendan on hemodynamics, local cerebral blood flow, neuronal injury, and neuroinflammation after asphyctic cardiac arrest in rats

OBJECTIVES

Despite advances in cardiac arrest treatment, high mortality and morbidity rates after successful cardiopulmonary resuscitation are still a major clinical relevant problem. The post cardiac arrest syndrome subsumes myocardial dysfunction, impaired microcirculation, systemic inflammatory response, and neurological impairment. The calcium-sensitizer levosimendan was able to improve myocardial function and initial resuscitation success after experimental cardiac arrest/cardiopulmonary resuscitation. We hypothesized that levosimendan exerts beneficial effects on cerebral blood flow, neuronal injury, neurological outcome, and inflammation 24 hours after experimental cardiac arrest/cardiopulmonary resuscitation.

DESIGN

Laboratory animal study.

SETTING

University animal research laboratory.

SUBJECTS

Sixty-one male Sprague-Dawley rats.

INTERVENTIONS

Animals underwent asphyxial cardiac arrest/cardiopulmonary resuscitation, randomized to groups with levosimendan treatment (bolus 12 µg/kg and infusion for 3 hr [0.3 µg/min/kg]) or vehicle (saline 0.9% bolus and infusion for 3 hr [equivalent fluid volume]). Cardiac index, local cerebral blood flow, and hemodynamic variables were measured for 180 minutes after cardiac arrest/cardiopulmonary resuscitation. Behavioral and neurological evaluations were conducted 24 hours after cardiac arrest/cardiopulmonary resuscitation. Furthermore, neuronal injury, expressed as Fluoro-Jade B-positive cells in the hippocampal formation, cortical and hippocampal inflammatory cytokine gene expression, and blood plasma interleukin-6 values were assessed.

MEASUREMENTS AND MAIN RESULTS

Treatment with levosimendan reduced neuronal injury and improved neurological outcome after 24 hours of reperfusion and resulted in elevated cardiac index and local cerebral blood flow compared with vehicle after cardiac arrest/cardiopulmonary resuscitation. Mean arterial blood pressure was reduced during the early reperfusion period in the levosimendan group. Cortical and hippocampal inflammatory cytokine gene expression and blood plasma interleukin-6 levels were not influenced.

CONCLUSIONS

Levosimendan increased cerebral blood flow after experimental cardiac arrest/cardiopulmonary resuscitation. This effect coincided with reduced neuronal injury and improved neurologic outcome. Findings seem to be independent of inflammatory effects because no effects by levosimendan on cerebral or systemic inflammation could be detected. In summary, levosimendan is a promising agent to improve neurological outcome after cardiac arrest/cardiopulmonary resuscitation.

Global and regional differences in cerebral blood flow after asphyxial versus ventricular fibrillation cardiac arrest in rats using ASL-MRI

Both ventricular fibrillation cardiac arrest (VFCA) and asphyxial cardiac arrest (ACA) are frequent causes of CA. However, only isolated reports compared cerebral blood flow (CBF) reperfusion patterns after different types of CA, and even fewer reports used methods that allow serial and regional assessment of CBF. We hypothesized that the reperfusion patterns of CBF will differ between individual types of experimental CA. In a prospective block-randomized study, fentanyl-anesthetized adult rats were subjected to 8min VFCA or ACA. Rats were then resuscitated with epinephrine, bicarbonate, manual chest compressions and mechanical ventilation. After the return of spontaneous circulation, CBF was then serially assessed via arterial spin-labeling magnetic resonance imaging (ASL-MRI) in cortex, thalamus, hippocampus and amygdala/piriform complex over 1h resuscitation time (RT). Both ACA and VFCA produced significant temporal and regional differences in CBF. All regions in both models showed significant changes over time (p<0.01), with early hyperperfusion and delayed hypoperfusion. ACA resulted in early hyperperfusion in cortex and thalamus (both p<0.05 vs. amygdala/piriform complex). In contrast, VFCA induced early hyperperfusion only in cortex (p<0.05 vs. other regions). Hyperperfusion was prolonged after ACA, peaking at 7min RT (RT7; 199% vs. BL, Baseline, in cortex and 201% in thalamus, p<0.05), then returning close to BL at ∼RT15. In contrast, VFCA model induced mild hyperemia, peaking at RT7 (141% vs. BL in cortex). Both ACA and VFCA showed delayed hypoperfusion (ACA, ∼30% below BL in hippocampus and amygdala/piriform complex, p<0.05; VFCA, 34-41% below BL in hippocampus and amygdala/piriform complex, p<0.05). In conclusion, both ACA and VFCA in adult rats produced significant regional and temporal differences in CBF. In ACA, hyperperfusion was most pronounced in cortex and thalamus. In VFCA, the changes were more modest, with hyperperfusion seen only in cortex. Both insults resulted in delayed hypoperfusion in all regions. Both early hyperperfusion and delayed hypoperfusion may be important therapeutic targets. This study was approved by the University of Pittsburgh IACUC 1008816-1.

Niacin suppresses the mitogen-activated protein kinase pathway and attenuates brain injury after cardiac arrest in rats

OBJECTIVES

To determine whether niacin attenuates brain injury and improves neurological outcome after cardiac arrest in rats and if its therapeutic benefits are associated with suppression of the mitogen-activated protein kinase pathway.

DESIGN

Prospective laboratory study.

SETTING

University laboratory.

SUBJECTS

Male Sprague-Dawley rats (n=77).

INTERVENTIONS

After 6 minutes of no flow time induced by ventricular fibrillation, cardiopulmonary resuscitation was provided and return of spontaneous circulation was achieved. Animals were then administered vehicle, single low dose (360 mg/kg; at 1 hr postreturn of spontaneous circulation), single high dose (1080 mg/kg; at 1 hr), or repeated low dose of niacin (360 mg/kg/d for 3 d; at 1, 24, and 48 hr) through an orogastric tube.

MEASUREMENTS AND MAIN RESULTS

Neurologic deficit scales were scored at 24 hours, 72 hours, and 7 days postreturn of spontaneous circulation. Single high dose of niacin improved neurologic deficit scales at 48 hours and 7 days, and repeated low dose of niacin improved neurologic deficit scales at 7 days. Then, a separate set of animals were killed at 72 hours postreturn of spontaneous circulation, and brain tissues were harvested. Single high dose and repeated low dose of niacin attenuated cellular apoptosis and neuronal damage in hippocampal cornu ammonis 1 and decreased axonal injury and microglial activation in corpus callosum. They increased nicotinamide adenine dinucleotide, reduced nicotinamide adenine dinucleotide phosphate and reduced glutathione levels, and decreased malondialdehyde level in brain tissues. Furthermore, they suppressed the phosphorylations of p38 and c-Jun N-terminal kinase/stress-activated protein kinase and the cleavage of caspase 3. However, they failed to enhance extracellular signal-regulated kinases 1/2 phosphorylation.

CONCLUSIONS

Single high dose and repeated low dose of niacin attenuated brain injury and improved neurological outcome after cardiac arrest in rats. Their therapeutic benefits were associated with suppressions of the phosphorylations of p38 and c-Jun N-terminal kinase/stress-activated protein kinase and the cleavage of caspase 3.

Extracorporeal versus conventional cardiopulmonary resuscitation after ventricular fibrillation cardiac arrest in rats: a feasibility trial

OBJECTIVES

Extracorporeal cardiopulmonary resuscitation with cardiopulmonary bypass potentially provides cerebral reperfusion, cardiovascular support, and temperature control for resuscitation from cardiac arrest. We hypothesized that extracorporeal cardiopulmonary resuscitation is feasible after ventricular fibrillation cardiac arrest in rats and improves outcome versus conventional cardiopulmonary resuscitation.

DESIGN

Prospective randomized study.

SETTING

University laboratory.

SUBJECTS

Adult male Sprague-Dawley rats.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Rats (intubated, instrumented with arterial and venous catheters and cardiopulmonary bypass cannulae) were randomized to conventional cardiopulmonary resuscitation, extracorporeal cardiopulmonary resuscitation with/without therapeutic hypothermia, or sham groups. After 6 minutes of ventricular fibrillation cardiac arrest, resuscitation was performed with drugs (epinephrine, sodium bicarbonate, and heparin), ventilation, either cardiopulmonary resuscitation or extracorporeal cardiopulmonary resuscitation, and defibrillation. Temperature was maintained at 37.0°C or 33.0°C for 12 hours after restoration of spontaneous circulation. Neurologic deficit scores, overall performance category, histological damage scores (viable neuron counts in CA1 hippocampus at 14 days; % of sham), and microglia proliferation and activation (Iba-1 immunohistochemistry) were assessed.

RESULTS

Extracorporeal cardiopulmonary resuscitation induced hypothermia more rapidly than surface cooling (p<0.05), although heart rate was lowest in the extracorporeal cardiopulmonary resuscitation hypothermia group (p<0.05). Survival, neurologic deficit scores, overall performance category, and surviving neurons in CA1 did not differ between groups. Hypothermia significantly reduced neuronal damage in subiculum and thalamus and increased the microglial response in CA1 at 14 days (all p<0.05). There was no benefit from extracorporeal cardiopulmonary resuscitation versus cardiopulmonary resuscitation on damage in any brain region and no synergistic benefit from extracorporeal cardiopulmonary resuscitation with hypothermia.

CONCLUSIONS

In a rat model of 6-minute ventricular fibrillation cardiac arrest, cardiopulmonary resuscitation or extracorporeal cardiopulmonary resuscitation leads to survival with intact neurologic outcomes. Twelve hours of mild hypothermia attenuated neuronal death in subiculum and thalamus but not CA1 and, surprisingly, increased the microglial response. Resuscitation from ventricular fibrillation cardiac arrest and rigorous temperature control with extracorporeal cardiopulmonary resuscitation in a rat model is feasible, regionally neuroprotective, and alters neuroinflammation versus standard resuscitation. The use of experimental extracorporeal cardiopulmonary resuscitation should be explored using longer insult durations.

Coagulofibrinolytic changes in patients with disseminated intravascular coagulation associated with post-cardiac arrest syndrome--fibrinolytic shutdown and insufficient activation of fibrinolysis lead to organ dysfunction

INTRODUCTION

Post-cardiac arrest syndrome (PCAS) is often associated with disseminated intravascular coagulation (DIC), thus leading to the development of multiple organ dysfunction syndrome (MODS). The aim of this study was to examine the pathophysiological relationships between coagulation, fibrinolysis and fibrinolytic shutdown by evaluating the levels of coagulofibrinolytic markers, including soluble fibrin, thrombin-activatable fibrinolysis inhibitor (TAFI), tissue plasminogen activator-plasminogen activator inhibitor-1 complex (tPAIC), plasmin-alpha2 plasmin inhibitor complex (PPIC), neutrophil elastase and fibrin degradation product by neutrophil elastase (EXDP).

MATERIALS AND METHODS

Fifty-two resuscitated patients were divided into two groups: 22 DIC and 30 non-DIC patients.

RESULTS

The levels of soluble fibrin, PPIC, tPAIC, EXDP and neutrophil elastase in the DIC patients with PCAS were significantly higher than those observed in the non-DIC patients. The values of the tPAIC and JAAM DIC scores were found to be independent predictors of increased SOFA scores in the DIC patients. The MODS patients demonstrated significantly higher levels of soluble fibrin and tPAIC; however, the levels of TAFI and EXDP were identical between the patients with and without MODS. In addition, positive correlations were observed between the levels of tPAIC and EXDP in the patients with non-MODS; however, no correlations were observed between these markers in the MODS patients.

CONCLUSIONS

Thrombin activation and fibrinolytic shutdown play important roles in the development of organ dysfunction in PCAS patients. Neutrophil elastase-mediated fibrinolysis cannot overcome the fibrinolytic shutdown that occurs in DIC patients with PCAS, thus resulting in the development of MODS.

Acute microvascular changes after subarachnoid hemorrhage and transient global cerebral ischemia

Subarachnoid hemorrhage and transient global cerebral ischemia result in similar pathophysiological changes in the cerebral microcirculation. These changes include microvascular constriction, increased leukocyte-endothelial interactions, blood brain barrier disruption, and microthrombus formation. This paper will look at various animal and preclinical studies that investigate these various microvascular changes, perhaps providing insight in how these microvessels can be a therapeutic target in both subarachnoid hemorrhage and transient global cerebral ischemia.

Rat forebrain perfusion in vivo by 1 artery like the isolated kidney model: a robust recovery model permitting ischemia without anesthesia to compare multiple brain injury states

BACKGROUND

Rat brain perfusion models are critical to basic research, but they can be imprecise and/or not durable for extended outcome studies.

OBJECTIVE

To demonstrate a rat brain perfusion model that provides a simplified reliable brain perfusion circuit, reduces variables during experiment and recovery, and therefore permits more precise, reliable, and context-independent research data.

METHODS

Rat forebrain perfusion was reduced surgically to that by 1 internal carotid artery without injury to the animal. The next day, the fully awake rat was studied for brain ischemia painlessly yet in the absence of anesthesia or other interventions that might bias or alter the biochemistry of the event. This model was rigorously validated with isotope cerebral blood studies during ischemia and with histology studies at 72 hours after ischemia. The first application of this model was to compare ischemia injuries for global total, global penumbra, and global shock ischemia in a single experimental context.

RESULTS

This model is accurate, reliable, and remarkably durable. This model permits the severest brain ischemia by vessel occlusion ever demonstrated in a recovery model. It also confirms that, with conditions otherwise identical, penumbra ischemia is less injurious than total ischemia and that total ischemia is less injurious than shock ischemia.

CONCLUSION

Although meticulous in construction, this model creates ischemia more simply and more reliably than the Pulsinelli 4-vessel ischemia model that inspired it, with the inherent advantages of an isolated organ system, in which a known tissue volume is perfused at a predetermined volume and rate. This model permits robust long-term recovery.

Management of the post-cardiac arrest syndrome

BACKGROUND

Recent advances in resuscitation science have revolutionized care of the cardiac arrest patient. Dramatic departures from time-honored advanced cardiac life support therapies, such as cardiocerebral resuscitation and bundled post-arrest care, have given rise to a new paradigm of resuscitation practices, which has boosted the rate of neurologically intact survival.

OBJECTIVES

This article reviews the pathophysiology of the post-cardiac arrest syndrome, the collective pathophysiology after return of spontaneous circulation, and presents management pearls specifically for the emergency physician. This growing area of scientific inquiry must be managed appropriately to sustain improved outcomes.

DISCUSSION

The emergency physician must understand this pathophysiology, manage resuscitated patients according to the latest evidence, and coordinate with appropriate inpatient resources.

CONCLUSION

The new approach to cardiac arrest care is predicated on a chain of survival that spans the spectrum of care from the prehospital arena through the emergency, intensive, and inpatient settings. The emergency physician is a crucial link in this chain.

Model of cardiac arrest in rats by transcutaneous electrical epicardium stimulation

OBJECTIVE

To establish a new model of cardiac arrest (CA) in rats by transcutaneous electrical epicardium stimulation.

METHODS

Two acupuncture needles connected to the anode and cathode of a stimulator were transcutaneously inserted into the epicardium as electrodes. The stimulating current was steered to the epicardium and the stimulation was maintained for 3 min to induce CA. Cardiopulmonary resuscitation (CPR) was performed at 6 min after a period of nonintervention.

RESULTS

CA was successfully induced in a total of 20 rats. The success rate of induction was 12/20 at the current intensity of 1 mA; and reached 20/20 when the current intensity was increased to 2 mA. After the electrical stimulation, the femoral blood pressure quickly dropped below 25 mmHg and the arterial pulse waveform disappeared. The average time from the electrical stimulation to CA induction was 5.10 (+/-2.81) s. When the electrical stimulation stopped, 18/20 rats had ventricular fibrillation and 2/20 rats had pulseless electrical activity. CPR was performed for averagely 207.4 (+/-148.8) s. The restoration of spontaneous circulation (ROSC) was 20/20. The death rate within 4h after ROSC was 5/20, and the 72-h survival rate was 10/20. There were only two cases of complications, a minor muscle contraction and a minor lung lobe injury.

CONCLUSION

The model of CA in rats induced by transcutaneous electrical epicardium stimulation is a stable model that requires low-intensity current and has fewer complications. This model may provide another option for experimental research of CA induced by malignant arrhythmia (especially VF).

Animal models of ischemic stroke. Part two: modeling cerebral ischemia

Animal models of stroke provide an essential tool for the understanding of the complex cellular and molecular pathophysiology of stroke and for testing novel recanalyzing, neuroprotective, neuroregenerative or anti- inflammatory drugs in pre- clinical setting. Since the first description of the distal occlusion of the middle cerebral artery (MCA) in rats, different techniques and methods to induce focal and global ischemia of the brains have been developed and optimized. The different models, ranging from proximal to distal MCA occlusion to embolic and photothrombotic stroke vary widely in their ability to model human disease and in their application to the study of cell death, inflammation and neural repair. In the first part of the review animal models developed for studying stroke related risk factors are described while this section discusses specific models that have been created for mimicking different types of stroke, focal and global ischemia in an experimental setup. Advantages and limits and the potential of the diverse models for the study of novel therapies as well as for the study of basic pathophysiological mechanisms are explored.

Cardiac arrest and cardiopulmonary resuscitation dysregulates the hypothalamic-pituitary-adrenal axis

Cardiac arrest and cardiopulmonary resuscitation (CA/CPR) increase the risk for affective disorders in human survivors. Postischemic anxiety- and depressive-like behaviors have been documented in animal models of CA/CPR; however, the stability of post-CA/CPR anxiety-like behavior over time and the underlying physiologic mechanisms remain unknown. The hypothalamic-pituitary-adrenal (HPA) axis and the corticotropin releasing factor (CRF) system may mediate the pathophysiology of anxiety and depression; therefore, this study measured CA/CPR-induced changes in CRF receptor binding and HPA axis negative feedback. Mice were exposed to CA/CPR or SHAM surgery and assessed 7 or 21 days later. Consistent with earlier demonstrations of anxiety-like behavior 7 days after CA/CPR, increased anxiety-like behavior in the open field was also present 21 days after CA/CPR. On postoperative day 7, CA/CPR was associated with an increase in basal serum corticosterone concentration relative to SHAM, but this difference resolved by postoperative day 21. The Dexamethasone Suppression Test showed that the CA/CPR group had enhanced negative feedback compared with SHAM controls at postoperative day 21. Furthermore, there was a gradual increase in CRF(1) receptor binding in the paraventricular nucleus of the hypothalamus and bed nucleus of the stria terminalis, as well as a transient decrease of both CRF(1) and CRF(2A) receptors in the dorsal hippocampus. Therefore, sustained changes in activity of the HPA axis and the CRF system after CA/CPR may contribute to the postischemic increase in affective disorders.

Post-cardiac arrest syndrome: Epidemiology, pathophysiology, treatment, and prognostication: A scientific statement from the International Liaison Committee on Resuscitation; the American Heart Association Emergency Cardiovascular Care Committee; the Council on Cardiovascular Surgery and Anesthesia; the Council on Cardiopulmonary, Perioperative, and Critical Care; the Council on Clinical Cardiology; the Council on Stroke (Part 1)

AIM OF THE REVIEW

To review the epidemiology, pathophysiology, treatment and prognostication in relation to the post-cardiac arrest syndrome.

METHODS

Relevant articles were identified using PubMed, EMBASE and an American Heart Association EndNote master resuscitation reference library, supplemented by hand searches of key papers. Writing groups comprising international experts were assigned to each section. Drafts of the document were circulated to all authors for comment and amendment.

RESULTS

The 4 key components of post-cardiac arrest syndrome were identified as (1) post-cardiac arrest brain injury, (2) post-cardiac arrest myocardial dysfunction, (3) systemic ischaemia/reperfusion response, and (4) persistent precipitating pathology.

CONCLUSIONS

A growing body of knowledge suggests that the individual components of the postcardiac arrest syndrome are potentially treatable.

Effects of activated protein C on post cardiac arrest microcirculation: an in vivo microscopy study

BACKGROUND

The clinical symptoms and pathophysiologic mechanisms during and after ischaemia-reperfusion following cardiac arrest (CA) and successful cardiopulmonary resuscitation (CPR) closely resemble those observed in patients with severe sepsis. Impairment of microcirculation and endothelial leakage seem to play key roles in the underlying pathophysiology. Recombinant human activated protein C (rhAPC) is the first drug being licensed for the treatment of severe sepsis in patients. Therefore, for the first time, we investigated effects of rhAPC on microhaemodynamic changes and endothelial leakage applying in vivo microscopy of postcapillary mesenteric venules after CA and CPR in rats.

METHODS

After 6 min of CA, male Wistar rats were randomised into two groups (n=10) to receive rhAPC or placebo (0.9% NaCl). Sham-operated animals (n=10) served as non-ischaemic controls. At 360, 420, and 480 min after CA in vivo microscopy was performed to assess wall shear rate (WSR) and plasma extravasation (PE).

RESULTS

Both treatment groups showed typical signs of impaired microcirculation and a severe endothelial leakage after CA at all time points studied when compared to the sham group. However, no significant differences between the treatment groups were observed with regard to WSR and PE.

CONCLUSION

Our results show that CA with consecutive successful CPR leads to a microcirculatory impairment closely resembling experimentally induced sepsis. Intriguingly, despite these similarities, rhAPC had no significant effects on WSR and PE. Our results strongly suggest that further mechanisms such as mast cell activation might play an important role and have therefore to be studied to elucidate the pathophysiology of "postresuscitation disease".