Cognitive and Functional Consequence of Cardiac Arrest

Cardiac arrest is associated with high morbidity and mortality. Better-quality bystander cardiopulmonary resuscitation training, cardiocerebral resuscitation principles, and intensive post-resuscitation hospital care have improved survival. However, cognitive and functional impairment after cardiac arrest remain areas of concern. Research focus has shifted beyond prognostication in the immediate post-arrest period to identification of mechanisms for long-term brain injury and implementation of promising protocols to reduce neuronal injury. These include therapeutic temperature management (TTM), as well as pharmacologic and psychological interventions which also improve overall neurological function. Comprehensive assessment of cognitive function post-arrest is hampered by heterogeneous measures among studies. However, the domains of attention, long-term memory, spatial memory, and executive function appear to be affected. As more patients survive cardiac arrest for longer periods of time, there needs to be a greater focus on interventions that can enhance cognitive and psychosocial function post-arrest.     

Emergency Neurological Life Support: Resuscitation Following Cardiac Arrest

Cardiac arrest is the most common cause of death in North America. Neurocritical care interventions, including targeted temperature management (TTM), have significantly improved neurological outcomes in patients successfully resuscitated from cardiac arrest. Therefore, resuscitation following cardiac arrest was chosen as an emergency neurological life support protocol. Patients remaining comatose following resuscitation from cardiac arrest should be considered for TTM. This protocol will review induction, maintenance, and re-warming phases of TTM, along with management of TTM side effects. Aggressive shivering suppression is necessary with this treatment to ensure the maintenance of a target temperature. Ancillary testing, including electrocardiography, computed tomography and/or magnetic resonance imaging of the brain, continuous electroencephalography monitoring, and correction of electrolyte, blood gas, and hematocrit changes, are also necessary to optimize outcomes.     

Management of brain injury after resuscitation from cardiac arrest

The devastating neurologic injury in survivors of cardiac arrest has been recognized since the development of modern resuscitation techniques. After numerous failed clinical trials, two trials showed that induced mild hypothermia can ameliorate brain injury and improve survival and functional neurologic outcome in comatose survivors of out-of-hospital cardiac arrest. This article provides a comprehensive review of the advances in the care of brain injury after cardiac arrest, with updates on the process of prognostication, the use of therapeutic hypothermia and adjunctive intensive care unit care for cardiac arrest survivors.     

Hypothermia for acute brain injury--mechanisms and practical aspects

Hypothermia is widely accepted as the gold-standard method by which the body can protect the brain. Therapeutic cooling--or targeted temperature management (TTM)--is increasingly being used to prevent secondary brain injury in patients admitted to the emergency department and intensive care unit. Rapid cooling to 33 °C for 24 h is considered the standard of care for minimizing neurological injury after cardiac arrest, mild-to-moderate hypothermia (33-35 °C) can be used as an effective component of multimodal therapy for patients with elevated intracranial pressure, and advanced cooling technology can control fever in patients who have experienced trauma, haemorrhagic stroke, or other forms of severe brain injury. However, the practical application of therapeutic hypothermia is not trivial, and the treatment carries risks. Development of clinical management protocols that focus on detection and control of shivering and minimize the risk of other potential complications of TTM will be essential to maximize the benefits of this emerging therapeutic modality. This Review provides an overview of the potential neuroprotective mechanisms of hypothermia, practical considerations for the application of TTM, and disease-specific evidence for the use of this therapy in patients with acute brain injuries.     

Hypothermia for neuroprotection after cardiac arrest: mechanisms, clinical trials and patient care

Therapeutic hypothermia is a proven part of cardio-cerebral resuscitation after cardiac arrest as it improves neurologic outcomes after hypoxic brain injury. This article reviews the mechanisms of hypothermic neuroprotection, the clinical trials that support its use after cardiac arrest, as well as the impact of hypothermia on patient management and prognosis. In caring for patients suffering hypoxic brain injury after cardiac arrest, the role of the neurologist is no longer limited to prognosis but is now to become actively involved in clinical management which includes the use of therapeutic hypothermia.     

Ethical issues in critical care and cardiac arrest: clinical research, brain death, and organ donation

Cardiac arrest results in global hypoxic-ischemic brain injury from which there is a range of possible neurological outcomes. In most cases, patients may require a surrogate to make decisions regarding end-of-life care, including the withdrawal of life-sustaining therapies. This article reviews ethical considerations that arise in the clinical care of patients following cardiac arrest, including decisions to continue or withdraw life-sustaining therapies; brain death determination; and organ donation in the context of brain death and cardiac death (so-called non-heart-beating donation). This article also discusses ethical concerns pertaining to the design and conduct of resuscitation research that is necessary for the development of effective therapies to prevent anoxic brain injury or promote neurological recovery.     

Repetitive anodal transcranial direct current stimulation improves neurological recovery by preserving the neuroplasticity in an asphyxial rat model of cardiac arrest

BackgroundNon-shockable rhythms present an increasing proportion of out-of-hospital cardiac arrest (CA) patients, but are associated with poor prognosis and received limited therapeutic effect of targeted temperature management (TTM). Previous study showed repetitive anodal transcranial direct current stimulation (tDCS) improved neurological outcomes in animals with ventricular fibrillation. Here, we examine the effectiveness of tDCS on neurological recovery and the potential mechanisms in a rat model of asphyxial CA.MethodCardiopulmonary resuscitation was initiated after 5 min of untreated asphyxial CA. Animals were randomized to three experimental groups immediately after successful resuscitation (n = 12/group, 6 males): no-treatment control (NTC) group, TTM group, and tDCS group. Post resuscitation hemodynamics, quantitative electroencephalogram (EEG), neurological deficit score, and 96-h survival were evaluated. Brain tissues of additional animals undergoing same experimental procedure was harvested for enzyme-linked immunoassay-based quantification assays of neuroplasticity-related biomarkers and compared with the sham-operated rats (n = 6/group).ResultsWe observed that after resuscitation tDCS-treated animals exhibited significantly higher mean arterial pressure and left ventricular ejection fraction than NTC group and showed greatly improved EEG characteristics including weighted-permutation entropy and gamma band power, and neurologic deficit scores and 96-h survival rates compared to NTC and TTM groups. Furthermore, neuroplastic biomarkers including microtubule-associated protein 2, growth-associated protein 43, postsynaptic density protein 95 and synaptophysin, were significantly higher in tDCS group when compared with NTC and TTM groups.ConclusionIn this rat model of asphyxial CA, repetitive anodal tDCS commenced after resuscitation improved neurological recovery, and it may exert a neuroprotective effect by preserving the neuroplasticity.     

Post-cardiac arrest encephalopathy

Brain injury continues to be a leading cause of mortality and morbidity in patients resuscitated after cardiac arrest. During periods of hypoxia and ischemia, numerous mechanisms contribute to the initial and secondary injury of the brain. Though many drugs and therapies have been evaluated for neuroprotection, only therapeutic hypothermia has been proven to be effective. Accurate prognostication after cardiac arrest is essential, and can be achieved with careful neurologic examination and several ancillary tests utilizing neurophysiology, neuroimaging, and biochemistry. Practice guidelines are now available for prognostication and postresuscitation care, with emphasis on improving survival and quality of life. Also reviewed are a wide spectrum of postarrest neurologic complications and their targeted treatments.     

Targeted temperature management and early neuro-prognostication after cardiac arrest

Targeted temperature management (TTM) is a recommended neuroprotective intervention for coma after out-of-hospital cardiac arrest (OHCA). However, controversies exist concerning the proper implementation and overall efficacy of post-CA TTM, particularly related to optimal timing and depth of TTM and cooling methods. A review of the literature finds that optimizing and individualizing TTM remains an open question requiring further clinical investigation. This paper will summarize the preclinical and clinical trial data to-date, current recommendations, and future directions of this therapy, including new cooling methods under investigation. For now, early induction, maintenance for at least 24 hours, and slow rewarming utilizing endovascular methods may be preferred. Moreover, timely and accurate neuro-prognostication is valuable for guiding ethical and cost-effective management of post-CA coma. Current evidence for early neuro-prognostication after TTM suggests that a combination of initial prediction models, biomarkers, neuroimaging, and electrophysiological methods is the optimal strategy in predicting neurological functional outcomes.     

Neuroprognostication after adult cardiac arrest treated with targeted temperature management: task force for Belgian recommendations

The prognosis of patients who are admitted to the hospital after cardiac arrest often relies on neurological examination, which could be significantly influenced by the use of sedative drugs or the implementation of targeted temperature management. The need for early and accurate prognostication is crucial as up to 15–20% of patients could be considered as having a poor outcome and may undergo withdrawal of life-sustaining therapies while a complete neurological recovery is still possible. As current practice in Belgium is still based on a very early assessment of neurological function in these patients, the Belgian Society of Intensive Care Medicine created a multidisciplinary Task Force to provide an optimal approach for monitoring and refine prognosis of CA survivors. This Task Force underlined the importance to use a multimodal approach using several additional tools (e.g., electrophysiological tests, neuroimaging, biomarkers) and to refer cases with uncertain prognosis to specialized centers to better evaluate the extent of brain injury in these patients.     

Neurologische Prognose und Therapie nach kardiopulmonaler Reanimation

The developments of cardiopulmonary resuscitation and intensive care medicine have made possible survival after cardiac arrest. However, only 10-30% of patients with initially successful resuscitation later reach a state without severe neurological impairment. Ethical and socioeconomic reasons therefore make early prognosis important for certain patients. There are no reliable parameters for predictions of good clinical outcome. If clinical information is consistent with severe hypoxic brain damage, cortical somatosensory evoked potentials are absent, and neuron-specific enolase values exceed 33-65 microg/l, recovery of consciousness can be excluded. The same result can be predicted if brain imaging shows severe hypoxemic changes or if a myoclonic status occurs on the first day. In summary, the prognosis in patients with cerebral anoxy and cardiopulmonary resuscitation remains poor. Treatment with hypothermia for 24 h is recommended.     

Clinical neurophysiologic monitoring and brain injury from cardiac arrest

Electrophysiologic testing continues to play an important role in injury stratification and prognostication in patients who are comatose after cardiac arrest. As discussed previously, however, the adage about treating whole patients, not just the numbers, is relevant in this situation. EEG and SSEP can offer high specificity for discerning poor prognosis as long as they are applied to appropriate patient populations. As discussed previously, EEG and SSEP patterns change during the first hours to days after cardiac arrest and negative prognostic information should not be based solely on studies performed during the first 24 hours. Both electrophysiologic techniques also are susceptible to artifacts that may worsen the electrical patterns artificially and suggest a falsely poor prognosis. EEG is suppressed by anesthetic agents and hypothermia, both of which may produce ECS and burst suppression. Patients who experience respiratory arrest from a toxic ingestion of narcotics or barbiturates, in particular, may present with high-grade EEG patterns initially. Many patients also receive anesthetic medications at the time of tracheal intubation, which may linger beyond their normal half-life in patients who have hepatic or renal insufficiency or concurrent use of interacting medications. SSEP is much less susceptible to sedative anesthetic agents, but hypothermia is demonstrated to prolong evoked potential latencies. As therapeutic hypothermia becomes more common after cardiac arrest, the effect of temperature on electrophysiologic testing needs to be taken into account. The publications discussed previously also emphasize the need to adjust the prognostic value of electro-physiologic tests to the pretest probability of meaningful neurologic recovery in individual patients. Clearly, grade I EEG patterns and normal N20 potentials indicate a much better prognosis in patients who have a short du-ration of cardiac arrest, short duration of coma after resuscitation, and when the studies are performed within the first few days. In patients who remain in coma days after resuscitation and lack appropriate brainstem reflexes, however, even the most normal appearing electrophysiologic patterns do little to change the overall prognosis. Aside from prognostication, electrophysiologic testing holds great promise in defining the basic anatomy and physiology of coma emergence after cardiac arrest. In addition, quantitative EEG and automated evoked potentials have the potential to render these tools less subjective and arcane and more applicable for monitoring patients in the period during and immediately after resuscitation. Quantitative EEG also has great potential asa tool to define the time window for neuroprotective intervention and the means to track the response to such therapies in real time.     

Emergency Neurological Life Support: Resuscitation Following Cardiac Arrest

Cardiac arrest is the most common cause of death in North America. Neurocritical care interventions, including therapeutic hypothermia (TH), have significantly improved neurological outcomes in patients successfully resuscitated from cardiac arrest. Therefore, resuscitation following cardiac arrest was chosen as an Emergency Neurological Life Support protocol. Patients remaining comatose following resuscitation from cardiac arrest and who are not bleeding are potential candidates for TH. This protocol will review induction, maintenance, and re-warming phases of TH, along with management of TH side effects. Aggressive shivering suppression is necessary with this treatment to ensure the maintenance of a target temperature. Ancillary testing, including electrocardiography, computed tomography imaging of the brain, continuous electroencephalography, monitoring, and correction of electrolyte, blood gas, and hematocrit changes are also necessary to optimize outcomes.     

Prehospital interventions to improve neurological outcome following cardiac arrest

As many cases of cardiac arrest occur outside of the health care setting, prehospital treatment may dramatically affect patient outcomes. The three major interventions that have been studied are chest compressions and ventilation, electrical defibrillation, and medications. Recent studies show that increasing the rate of cardiopulmonary resuscitation (CPR), decreasing the rate of ventilation, and initiation of CPR prior to defibrillation may result in improved survival. Biphasic defibrillators can restore perfusing rhythms while minimizing myocardial injury. Public access to automatic defibrillators has been shown to increase the survival of cardiac arrest patients. Medications such as amiodarone, vasopressin, and thrombolytics also may have a role in the prehospital treatment of cardiac arrest. Recent advances in these areas will be reviewed with a discussion of the effect of each intervention on the restoration of circulation and neurological outcomes.     

Repetitive anodal transcranial direct current stimulation improves neurological outcome and survival in a ventricular fibrillation cardiac arrest rat model

Background

Transcranial direct current stimulation (tDCS) modulates neuronal activity and is a potential therapeutic tool for many neurological diseases. However, its beneficial effects on post cardiac arrest syndrome remains uncertain.

Hypoxic-ischaemic brain injury

Hypoxic-ischaemic brain injury is common and usually due to cardiac arrest or profound hypotension. The clinical pattern and outcome depend on the severity of the initial insult, the effectiveness of immediate resuscitation and transfer, and the post-resuscitation management on the intensive care unit. Clinical assessment is difficult and so often these days compromised by sedation, neuromuscular blockade, ventilation, hypothermia and inotropic management. Investigations can add valuable information, in particular brain MRI shows characteristic patterns depending on the severity of the injury and the timing of imaging. EEG patterns may also suggest the possibility of a good outcome. There is no entirely reliable algorithm of clinical signs or investigations which allow a definitive prognosis but the combination of careful repeated observations and appropriate ancillary investigations allows the neurologist to give an informed and accurate opinion of the likely outcome, and to advise on management. Overall, the prognosis is extremely poor and only a quarter of patients survive to hospital discharge, and often even then with severe neurological or cognitive deficits.     

Adenosine treatment delays postischemic hippocampal CA1 loss after cardiac arrest and resuscitation in rats

Resuscitation from cardiac arrest results in reperfusion injury that leads to increased postresuscitation mortality and delayed neuronal death. One of the many consequences of resuscitation from cardiac arrest is a derangement of energy metabolism and the loss of adenylates, impairing the tissue's ability to regain proper energy balance. In this study, we investigated the effects of adenosine (ADO) on the recovery of the brain from 12 min of ischemia using a rat model of cardiac arrest and resuscitation. Compared to the untreated group, treatment with adenosine (7.2 mg/kg) initiated immediately after resuscitation increased the proportion of rats surviving to 4 days and significantly delayed hippocampal CA1 neuronal loss. Brain blood flow was increased significantly in the adenosine-treated rats 1 h after cardiac arrest and resuscitation. Adenosine-treated rats exhibited less edema in cortex, brainstem and hippocampus during the first 48 h of recovery. Adenosine treatment significantly lowered brain temperature during recovery, and a part of the neuroprotective effects of adenosine treatment could be ascribed to adenosine-induced hypothermia. With this dose, adenosine may have a delayed transient effect on the restoration of the adenylate pool (AXP = ATP + ADP + AMP) 24 h after cardiac arrest and resuscitation. Our findings suggested that improved postischemic brain blood flow and ADO-induced hypothermia, rather than adenylate supplementation, may be the two major contributors to the neuroprotective effects of adenosine following cardiac arrest and resuscitation. Although adenosine did not prevent eventual CA1 neuronal loss in the long term, it did delay neuronal loss and promoted long-term survival. Thus, adenosine or specific agonists of adenosine receptors should be evaluated as adjuncts to broaden the window of opportunity in the treatment of the reperfusion injury following cardiac arrest and resuscitation.     

Molecular markers of brain damage--clinical and ethical implications with particular focus on cardiac arrest

Although 25-50% of patients suffering from cardiac arrest can be stabilised haemodynamically, the hospital discharge rate is only 2-14%. One of the major causes of this discrepancy is persistent brain damage. Studies to assess the prognostic value of early prediction of neurologic and overall outcome in patients with cardiac arrest have not yet produced precise and generally accepted diagnostic rules. As apparative diagnostic methods often fail to predict neurologic outcome, the role of molecular markers has come a focus of common interest for early outcome prediction. This systematic review article aims to give an overview on the most important molecular markers for neurologic and overall outcome prediction and outline the advantages, clinical implications and ethical issues in patients undergoing cardiopulmonary resuscitation after cardiac arrest. For this purpose, the traditional marker for brain damage, the neuron-specific enolase, a gamma gamma isomer of enolase and cytoplasmatic enzyme of glycolysis, and the astroglial protein S100, a calcium-binding protein regulating neuronal differentiation, outgrowth, and apoptosis, are analysed and their role discussed as a marker for brain damage in general and recovery after cardiopulmonary resuscitation following cardiac arrest. Neuron-specific enolase has been investigated as a neuro-marker after brain damage and for outcome prediction in unconscious patients. Whereas the protein S100 has proven to be a good marker for neuronal damage after isolated brain injury, its role in cardiac surgery is not as clear: at least, in the early postoperative phase S100 is not a sole marker for neurologic damage, as release of S100 from cardiac tissue and other sources has also been demonstrated. However, the persistent elevation of S100 after cardiac surgery is specific for neurologic impairment. Most interestingly, after cardiac arrest the protein S100 has shown to be a good survival marker for overall outcome prediction. Although it cannot be absolutely determined whether cerebral or cardiac release of S100 is predominant in this clinical setting, recent studies have revealed that S100 serum levels are a useful diagnostic tool for outcome prediction. In contrast, after cardiac arrest serum levels of protein S100 did not reach a 100% specificity and sensitivity in clinical studies, and, therefore, elevated S100 in these patients has to be interpreted with caution. Nonetheless, low S100 serum levels have been correlated with good outcome and, therefore, even if all other diagnostic tests indicate poor outcome, all therapeutic efforts must be undertaken, as no single study has shown that normal S100 serum levels were associated with poor prognosis.     

Thiamine and Parkinson's disease

Cardiac arrest is a leading cause of death that affects more than a million individuals worldwide every year. Despite the recent advancement in the field of cardiac arrest and resuscitation, the management and prognosis of post-cardiac arrest brain injury remain suboptimal. The pathophysiology of post-cardiac arrest brain injury involves a complex cascade of molecular events, most of which remain unknown. Considering that a potentially broad therapeutic window for neuroprotective drug therapy is offered in most successfully resuscitated patient after cardiac arrest, the need for further research is imperative. The aim of this article is to present the major pathophysiological disturbances leading to post-cardiac arrest brain injury, as well as to review the available pharmacological therapies.     

Sexually Dimorphic Response of TRPM2 Inhibition Following Cardiac Arrest-Induced Global Cerebral Ischemia in Mice

Transient global cerebral ischemia due to cardiac arrest followed by resuscitation (CA/CPR) causes significant neurological damage in vulnerable neuron populations within the brain, such as hippocampal CA1 neurons. In recent years, we have implicated the transient receptor potential M2 (TRPM2) channel as a mediator of ischemic injury to neurons. We previously demonstrated that genetic and pharmacological strategies that reduce TRPM2 function preferentially protect male neurons in vitro and reduce infarct volume following experimental stroke. Due to the narrow therapeutic window for intervention following ischemic stroke, it is important to assess the role of TRPM2 in other models of cerebral ischemia. Therefore, this study utilized a modified mouse model of CA/CPR to mimic more accurately the clinical condition by maintaining body and head temperatures near the physiological range throughout. Here, we report that inhibition of TRPM2 activity with clotrimazole reduces hippocampal CA1 neuronal injury when administered 30 min after resuscitation from cardiac arrest. Consistent with our previous observations, neuroprotection was observed in male mice and no effect on injury was observed in the female. These findings provide further evidence for TRPM2 as a target for protection against cerebral ischemia in the male brain.