Hypertonic saline infusion suppresses apoptosis of hippocampal cells in a rat model of cardiopulmonary resuscitation

FLUID THERAPY DURING AND AFTER CARDIOPULMONARY RESUSCITATION FOR NONTRAUMATIC CARDIAC ARREST: A SYSTEMATIC REVIEW OF EVIDENCE FROM PRECLINICAL AND CLINICAL STUDIES

ABSTRACT

Background: Several therapeutic interventions are recommended during and after cardiopulmonary resuscitation (CPR) in order to optimize oxygen delivery and improve survival rates. Among these interventions, there is a clinical practice heterogeneity regarding use of fluids in this setting. The optimal fluid resuscitation strategy remains controversial. This systematic review aimed to summarize the current knowledge regarding type, dosing, and safety of fluid therapy during and after CPR in animal models and human studies. Methods: A systematic search of the literature within PubMed and Embase was conducted from database inception to June 2024. Preclinical and clinical studies involving adult patients with nontraumatic cardiac arrest describing fluid resuscitation strategies and reporting at least one outcome of interest were included: achievement of return of spontaneous circulation, survival to hospital admission or discharge, incidence of acute kidney injury and neurological outcome. Studies assessing intra-arrest bicarbonate buffer therapy and/or using cold fluid infusions to induce hypothermia were excluded. Results: Twenty-nine studies met inclusion criteria, including 10 clinical studies and 19 animal models. The effects of fluid therapy during CPR are underexplored in clinical research. Hypertonic saline therapy has emerged as an alternative resuscitative fluid during CPR in animal models. In postresuscitation setting, balanced crystalloids have been increasingly assessed. There are no clinical studies investigating the impact of early goal directed fluid resuscitation on outcomes in particular shock resolution and neurological recovery. Conclusions: There is a call for clinical evidence to assess the efficacy and safety of fluid resuscitation during CPR, to define the place of hypertonic saline therapy during and after resuscitation and finally to implement early goal-directed fluid therapy as a tailored intervention of the postarrest care bundle. Review registration: ROSPERO; No.: CRD42024571617; URL: https://www.crd.york.ac.uk/prospero/.

Development and validation of prediction models for death within 6 months after cardiac arrest

Background

Even in patients with a successful return of spontaneous circulation (ROSC), outcomes after cardiac arrest (CA) remain poor, with some eventually succumbing after several months of treatment. There is a need for early assessment of outcomes in patients with ROSC after CA. Therefore, we developed three models for predicting death within 6 months after CA using early post-arrest factors, performed external validation, and compared their efficiency.

Methods

In this retrospective cohort study, 199 patients aged 18-80 years who experienced either in-hospital cardiac arrest or out-of-hospital cardiac arrest and achieved ROSC were included as the training set. Patients were divided into an "alive" group (95 cases) and a "dead" group (104 cases) according to their survival status 6 months after CA. Demographic data, medical history, and laboratory results were collected. Univariate and multivariate logistic regression analyses were used to identify risk factors. A risk prediction model was constructed using random forest methods, support vector machine (SVM), and a nomogram based on factors with P < 0.1 in the multivariate logistic analyses. An additional 42 patients aged 18-80 years who experienced CA with ROSC were included as the validation set. Receiver operating characteristic (ROC), decision, and calibration curves were used to assess model performance.

Results

Duration of cardiac arrest, lactate level after ROSC, secondary infections, length of hospital stay, and ventilator support were the top five risk factors for death within 6 months after CA (P < 0.1) in sequence. The random forest model [average area under the ROC curve (AUC), training set = 0.991, validation set = 0.703] performed better than the SVM model (AUC, training set = 0.905, validation set = 0.636) and the nomogram model (AUC, training set = 0.893, validation set = 0.682). Decision curve analysis indicated that the random forest model provided the best net benefit. The calibration curve indicated that the prediction for death within 6 months after CA by the random forest model was consistent with actual outcomes. The AUC of the prediction model constructed using random forest, SVM, and nomogram methods was 0.991, 0.893, and 0.905, respectively.

Conclusions

The prediction model established by early post-arrest factors performed well, which can aid in evaluating prognosis within 6 months after cardiac arrest. The predictive model constructed using random forest methods exhibited better predictive efficacy.

2024 AAHA Fluid Therapy Guidelines for Dogs and Cats

Fluids are drugs used in veterinary patients capable of producing beneficial therapeutic or inadvertent harmful effects within the body's intravascular, interstitial, and intracellular fluid spaces. The individualized design of a fluid therapy plan requires careful patient assessment and targeted selection of proper fluid types, administration routes, and rates, along with adjustments during therapy tailored specifically as per the individual patient's fluid requirement and therapeutic response. Personalized fluid prescriptions and vigilant patient monitoring help avoid patient morbidity from body fluid deficiencies, fluid excess, and electrolyte derangements and support better patient outcomes. These guidelines provide an overview of fluid dynamics within the fluid spaces of the body, describe various types of fluids and their uses, and outline recommendations for fluid administration for resuscitation, rehydration, and maintenance purposes. The guidelines also outline approaches to fluid therapy for anesthetized patients and reiterate the recommendations of reduced fluid rates in this population of patients. Additionally, the guidelines include practical fluid therapy strategies for patients with various common disorders. The goal of these guidelines is to help veterinary professionals safely and effectively prescribe and administer fluid therapy for canine and feline patients.

Neuroprotective Approaches for Brain Injury After Cardiac Arrest: Current Trends and Prospective Avenues

With the implementation of improved bystander cardiopulmonary resuscitation techniques and public-access defibrillation, survival after out-of-hospital cardiac arrest (OHCA) has increased significantly over the years. Nevertheless, OHCA survivors have residual anoxia/reperfusion brain damage and associated neurological impairment resulting in poor quality of life. Extracorporeal membrane oxygenation or targeted temperature management has proven effective in improving post-cardiac arrest (CA) neurological outcomes, yet considering the substantial healthcare costs and resources involved, there is an urgent need for alternative treatment strategies that are crucial to alleviate brain injury and promote recovery of neurological function after CA. In this review, we searched PubMed for the latest preclinical or clinical studies (2016-2023) utilizing gas-mediated, pharmacological, or stem cell-based neuroprotective approaches after CA. Preclinical studies utilizing various gases (nitric oxide, hydrogen, hydrogen sulfide, carbon monoxide, argon, and xenon), pharmacological agents targeting specific CA-related pathophysiology, and stem cells have shown promising results in rodent and porcine models of CA. Although inhaled gases and several pharmacological agents have entered clinical trials, most have failed to demonstrate therapeutic effects in CA patients. To date, stem cell therapies have not been reported in clinical trials for CA. A relatively small number of preclinical stem-cell studies with subtle therapeutic benefits and unelucidated mechanistic explanations warrant the need for further preclinical studies including the improvement of their therapeutic potential. The current state of the field is discussed and the exciting potential of stem-cell therapy to abate neurological dysfunction following CA is highlighted.

Remote preconditioning combined with nebulized budesonide alleviate lipopolysaccharide induced acute lung injury via regulating HO-1 and NF-κB in rats

BACKGROUND

Acute lung injury (ALI) may result in severe systemic inflammation and is life-threatening. Remote inflammatory preconditioning (RIPC) has been confirmed to have an endogenous protective effect against ALI. Budesonide (BS) is a potent corticosteroid typically administered through nebulization that reduces inflammation in the lungs. We speculate that the combined use of RIPC and nebulized BS has a stronger protective effect on ALI.

METHODS

48 Sprague-Dawley male rats were used for the experiments. Animals were divided evenly and randomly into three groups, control (NS injection), LPS (LPS injection), and RIPC (LPS injection with RIPC). Each group was then divided into two subgroups with inhalation of nebulized normal saline (NS) or BS. Prior to injection of LPS, RIPC was performed by tying and untying the right hind limb for three cycles of 5 min each. Following LPS injection, animals in each subgroup were placed in a same cage for nebulized inhalation. Animals were sacrificed 6 h after LPS injection. Histological evaluation of ALI and lung wet-to-dry weight ratio were measured. Serum lactate acid, inflammatory cytokines, oxidative stress indicators were detected. The expression of HO-1, NF-κB p65 and p-p65 was measured by western blotting.

RESULTS

RIPC combined with nebulized BS significantly attenuated the LPS-induced ALI in rats. Reduction of MDA, increasing of SOD activity were found significantly improved by the joint strategy. TNF- and IL-1β rise brought on by LPS was reduced, but IL-10 production dramatically enhanced when compared to the LPS group. The expression of HO-1 was significantly increased by RIPC combined with nebulized BS while the expression of NF-κB p65 and p-p65 was decreased when compared with the LPS group.

CONCLUSION

RIPC combined with nebulized budesonide is protective for ALI induced by LPS in rats.

Rat model of asphyxia-induced cardiac arrest and resuscitation

Neurologic injury after cardiopulmonary resuscitation is the main cause of the low survival rate and poor quality of life among patients who have experienced cardiac arrest. In the United States, as the American Heart Association reported, emergency medical services respond to more than 347,000 adults and more than 7,000 children with out-of-hospital cardiac arrest each year. In-hospital cardiac arrest is estimated to occur in 9.7 per 1,000 adult cardiac arrests and 2.7 pediatric events per 1,000 hospitalizations. Yet the pathophysiological mechanisms of this injury remain unclear. Experimental animal models are valuable for exploring the etiologies and mechanisms of diseases and their interventions. In this review, we summarize how to establish a standardized rat model of asphyxia-induced cardiac arrest. There are four key focal areas: (1) selection of animal species; (2) factors to consider during modeling; (3) intervention management after return of spontaneous circulation; and (4) evaluation of neurologic function. The aim was to simplify a complex animal model, toward clarifying cardiac arrest pathophysiological processes. It also aimed to help standardize model establishment, toward facilitating experiment homogenization, convenient interexperimental comparisons, and translation of experimental results to clinical application.

Eleutheroside E alleviates cerebral ischemia-reperfusion injury in a 5-hydroxytryptamine receptor 2C (Htr2c)-dependent manner in rats

Stroke is the central disorder underlined by ischemia-reperfusion (I/R) injury. Eleutheroside E (EE) is administered as the shield in some ischemia tissues with anti-inflammatory action. However, whether EE defends I/R-induced damage in the brain remains unknown. Here, we demonstrated that EE significantly alleviated the cerebral I/R injury and reduced the apoptosis of hippocampal neuron cells in rats. During the anti-apoptosis process, EE significantly upregulated the expression of 5-hydroxytryptamine receptor 2C (Htr2c) gene. Silencing Htr2c expression dramatically weakened the protective effect of EE on I/R-induced apoptosis of rat hippocampal neuron. EE-regulated Htr2c also remarkably inhibited the expression of caspase-3, −6 and −7, thereby suggesting a plausible anti-apoptosis mechanism associated with Htr2c/caspase axis. These findings elicit the potentially clinical strategy that targets Htr2c to improve outcome of ischemia brain.

Remote Inflammatory Preconditioning Alleviates Lipopolysaccharide-Induced Acute Lung Injury via Inhibition of Intrinsic Apoptosis in Rats

BACKGROUND

Acute lung injury (ALI) always leads to severe inflammation. As inflammation and oxidative stress are the common pathological basis of endotoxin-induced inflammatory injury and ischemic reperfusion injury (IRI), we speculate that remote ischemic preconditioning (RIPC) can be protective for ALI when used as remote inflammatory preconditioning (RInPC).

METHOD

A total of 21 Sprague-Dawley rats were used for the animal experiments. Eighteen rats were equally and randomly divided into the control (NS injection), LPS (LPS injection), and RInPC groups. The RInPC was performed prior to the LPS injection via tourniquet blockage of blood flow to the right hind limb and adopted three cycles of 5 min tying followed by 5 min untying. Animals were sacrificed 24 hours later. There were 2 rats in the LPS group and 1 in the RInPC group who died before the end of the experiment. Supplementary experiments in the LPS and RInPC groups were conducted to ensure that 6 animals in each group reached the end of the experiment.

RESULTS

In the present study, we demonstrated that the RInPC significantly attenuated the LPS-induced ALI in rats. Apoptotic cells were reduced significantly by the RInPC, with the simultaneous improvement of apoptosis-related proteins. Reduction of MPO and MDA and increasing of SOD activity were found significantly improved by the RInPC. Increasing of TNF-α, IL-1β, and IL-6 induced by the LPS was inhibited, while IL-10 was significantly increased by RInPC, compared to the LPS group.

CONCLUSION

RInPC could inhibit inflammation and attenuate oxidative stress, thereby reducing intrinsic apoptosis and providing lung protection in the LPS-induced ALI in rats.

Fluid Therapy During Cardiopulmonary Resuscitation

Cardiopulmonary arrest (CPA), the acute cessation of blood flow and ventilation, is fatal if left untreated. Cardiopulmonary resuscitation (CPR) is targeted at restoring oxygen delivery to tissues to mitigate ischemic injury and to provide energy substrate to the tissues in order to achieve return of spontaneous circulation (ROSC). In addition to basic life support (BLS), targeted at replacing the mechanical aspects of circulation and ventilation, adjunctive advanced life support (ALS) interventions, such as intravenous fluid therapy, can improve the likelihood of ROSC depending on the specific characteristics of the patient. In hypovolemic patients with CPA, intravenous fluid boluses to improve preload and cardiac output are likely beneficial, and the use of hypertonic saline may confer additional neuroprotective effects. However, in euvolemic patients, isotonic or hypertonic crystalloid boluses may be detrimental due to decreased tissue blood flow caused by compromised tissue perfusion pressures. Synthetic colloids have not been shown to be beneficial in patients in CPA, and given their documented potential for harm, they are not recommended. Patients with documented electrolyte abnormalities such as hypokalemia or hyperkalemia benefit from therapy targeted at those disturbances, and patients with CPA induced by lipid soluble toxins may benefit from intravenous lipid emulsion therapy. Patients with prolonged CPA that have developed significant acidemia may benefit from intravenous buffer therapy, but patients with acute CPA may be harmed by buffers. In general, ALS fluid therapies should be used only if specific indications are present in the individual patient.

Remote Ischemic Postconditioning Inhibits Hippocampal Neuronal Apoptosis and Mitophagy After Cardiopulmonary Resuscitation in Rats

BACKGROUND

Studies have shown that remote ischemic post-conditioning can improve brain damage caused by ischemia and hypoxia. However, the specific mechanism underlying this phenomenon is still unclear. The purpose of this study was to investigate the effects of remote ischemic post-conditioning on neuronal apoptosis and mitophagy after cardiopulmonary resuscitation (CPR) in rats.

METHODS

Male Sprague-Dawley rats were used to establish an asphyxia cardiac arrest model by clamping the tracheal duct. First, the expression levels of P53, Cytochrome c (Cytc), and Parkin in the cytoplasm and mitochondria were observed at 3, 6, 24, and 72 h after the restoration of spontaneous circulation (ROSC). Then neurological deficit scores, hippocampal neuron apoptosis, mitochondrial P53 and Parkin, cytoplasmic Cytc, and neuron ultrastructure were evaluated 24 h after ROSC.

RESULTS

P53 and Parkin can translocate from the cytoplasm to the mitochondria, promoting the translocation of cytoplasmic Cytc to mitochondria after CPR, reaching a peak at 24 h after the ROSC. The P53 inhibitor Pifithrin-μ reduced apoptosis induced by P53 mitochondrial translocation. Apoptosis was induced after cardiac arrest and attenuated by remote ischemic postconditioning via inhibiting P53 mitochondrial translocation and the release of Cytc to the cytoplasm. In addition, remote ischemic postconditioning could inhibit Parkin-mediated mitophagy.

CONCLUSION

Taken together, our results show that remote ischemic post-conditioning improves neural function after CPR by inhibiting P53 mitochondrial translocation-induced apoptosis and Parkin-mediated mitophagy.

Cyclosporine A Plus Ischemic Postconditioning Improves Neurological Function in Rats After Cardiac Resuscitation

BACKGROUND AND OBJECTIVE

Attenuation of neuronal apoptosis helps maintain neurological function in patients after cardiac arrest. After ischemia-reperfusion, both cyclosporin A (CsA) and ischemic postconditioning independently protect mitochondria and thus reduce nerve injury. This study employed a rat model to evaluate the neuroprotective effect of combining ischemic postconditioning with CsA after cardiopulmonary resuscitation (CPR).

METHODS

Rats were apportioned equally to model control, postconditioned, CsA-treated, or CsA + postconditioned groups. Asphyxial cardiac arrest was imposed using modified Utstein-style guidelines. In the appropriate groups, postconditioning was implemented by ischemia and reperfusion (clamping and loosening the left femoral artery); CsA treatment was delivered with a single intravenous dose. Neurological deficits were scored at different times after CPR. Histological evaluation and electron microscopy were used to evaluate tissue damage, and TUNEL and flow cytometry were used to measure the apoptotic rate of hippocampal neurons and size of the mitochondrial permeability transition pore (mPTP) opening.

RESULTS

The apoptotic rate was significantly lower in the postconditioned and CsA-treated groups compared with the model control and lowest in the CsA + postconditioned group. By histological evaluation and electron microscopy, the least damage was observed in the CsA + postconditioned group. The neurological deficit score of the CsA + postconditioned group was significantly higher than that of the CsA-treated group, but the size of the mPTP openings of these two groups was comparable.

CONCLUSION

Ischemic postconditioning combined with CsA exerted a better neuroprotective effect after CPR than did either postconditioning or CsA alone. Inhibiting the opening of the mPTP is not the only neuroprotective mechanism.

Mitophagy in the Hippocampus Is Excessive Activated After Cardiac Arrest and Cardiopulmonary Resuscitation

This study examined the activation of mitophagy following cardiac arrest (CA) and cardiopulmonary resuscitation (CPR) and the relationship between the change with time and apoptosis.

MAIN METHODS

The male Sprague-Dawley rats were randomized into four groups: Sham group, CPR24h group, CPR48h group, CPR72h group. The rat model of cardiac arrest was established by asphyxiation. We employed western blot to analyze the levels of mitophagy related proteins of hippocampus, JC-1 to detect mitochondrial membrane potential (MMP) and flow cytometry to measure the rate of apoptosis of hippocampal neurons. Moreover, we also intuitively observed the occurrence of mitophagy through electron microscopy.

KEY FINDINGS

The results showed that the levels of TOMM20 and Tim23 protein were significantly decreased after CPR, which were more remarkable following 72 h of CPR. However, the protein levels of dynamin related protein 1 (Drp1) and cytochrome C (Cyt-c) were strongly up-regulated after CPR. Meanwhile, the hippocampal MMP decreased gradually with time after CPR. Furthermore, we more intuitively verified the activation of mitophagy through electron microscopy. In addition, the rats of apoptosis rate of hippocampus after CPR were significantly increased, which were gradually enhanced over time from 24 h until at least 72 h following CPR.

SIGNIFICANCE

with the enhancement of mitophagy, the apoptosis of hippocampal neurons was gradually enhanced, which suggested mitophagy may be excessive activated and aggravating brain damage after CA and CPR.

The post-cardiac arrest syndrome: A case for lung-brain coupling and opportunities for neuroprotection

Systemic inflammation and multi-organ failure represent hallmarks of the post-cardiac arrest syndrome (PCAS) and predict severe neurological injury and often fatal outcomes. Current interventions for cardiac arrest focus on the reversal of precipitating cardiac pathologies and the implementation of supportive measures with the goal of limiting damage to at-risk tissue. Despite the widespread use of targeted temperature management, there remain no proven approaches to manage reperfusion injury in the period following the return of spontaneous circulation. Recent evidence has implicated the lung as a moderator of systemic inflammation following remote somatic injury in part through effects on innate immune priming. In this review, we explore concepts related to lung-dependent innate immune priming and its potential role in PCAS. Specifically, we propose and investigate the conceptual model of lung-brain coupling drawing from the broader literature connecting tissue damage and acute lung injury with cerebral reperfusion injury. Subsequently, we consider the role that interventions designed to short-circuit lung-dependent immune priming might play in improving patient outcomes following cardiac arrest and possibly other acute neurological injuries.

Hypothermic properties of dexmedetomidine provide neuroprotection in rats following cerebral ischemia-reperfusion injury

Dexmedetomidine (Dex) is a sedative and analgesic agent that is widely administered to patients admitted to the intensive care unit, and has been demonstrated to result in hypothermia. Many patients have been revealed to benefit from therapeutic hypothermia, which can mitigate cerebral ischemia/reperfusion (I/R) injury following successful cardiopulmonary resuscitation. However, studies investigating the efficacy of Dex in I/R treatment is lacking. The present study aimed to investigate the efficacy of Dex in mitigating neuronal damage, and to determine the possible mechanism of its effects in a rat model of cardiac arrest (CA). CA was induced in Sprague-Dawley rats by asphyxiation for 5 min. Following successful resuscitation, the surviving rats were randomly divided into two treatment groups; one group was intraperitoneally administered with Dex (D group), whereas the control group was treated with normal saline (N group). Critical parameters, including core temperature and blood pressure were monitored following return of spontaneous circulation (ROSC). Arterial blood samples were collected at 10 min after surgery (baseline) 30 and 120 min post-ROSC; and neurological deficit scores (NDS) of the rats were taken 12 or 24 h after ROSC prior to euthanasia. The hippocampal tissue was then removed for analysis by histology, electron microscopy and western blotting. Rats in the D group exhibited a lower core temperature and higher NDS scores compared with the N group (P<0.05). In addition, Dex injection resulted in reduced expression of apoptotic and autophagy-associated factors in the hippocampus (P<0.05). Dex treatment induced hypothermia and improved neurological function in rats after ROSC following resuscitation from CA by inhibiting neuronal apoptosis and reducing autophagy, which suggested that Dex may be a potential therapy option for patients with CA.

The protective effects of distal ischemic treatment on apoptosis and mitochondrial permeability in the hippocampus after cardiopulmonary resuscitation

Apoptosis and mitochondrial dysfunction are the main cause of neurological injury after cardiopulmonary resuscitation (CPR). However, the effects of distal ischemic treatments on ischemia induced apoptosis are rarely studied, and the mechanism by which mitochondrial dysfunction contributes to CPR still unclear. A rat model of distal ischemia was established by clipping the right femoral artery. Rats were divided into blank, model, pre distal ischemic treatment, per-treatment, and post-treatment groups. Neurological deficit score was scored to evaluate neurologic function after cardiopulmonary resuscitation for 72 hr. We employed TUNEL and flow cytometry to measure the rate of apoptosis of hippocampal neurons, the integrity of mitochondrial membrane and the degree of mitochondrial permeability transition pore (mPTP) opening. The rate of apoptosis rate of hippocampal CA1 neurons in the pre-treatment and post-treatment groups were significantly lower than that of the model group. Moreover, the integrity of the mitochondrial membrane in the pre-treatment and post-treatment groups was higher than that in the model and per- treatment groups. Furthermore, the degree of mPTP opening was lower in the pre-treatment and post-treatment groups than the untreated and per-treatment groups. Taken together, our results show that ischemic preconditioning and post processing can maintain the integrity of mitochondria, perhaps by inhibiting the opening of mPTP, and reducing apoptosis of hippocampal neurons by regulating expression of apoptosis related proteins after CPR, to improve neurological function. This study highlights a novel target pathway for treatment of CPR.