Post-cardiac arrest myocardial dysfunction is improved with cyclosporine treatment at onset of resuscitation but not in the reperfusion phase

Reassessment of mitochondrial cyclophilin D as a target for improving cardiac arrest outcomes in the era of therapeutic hypothermia

Uncertainty exists regarding whether cyclophilin D (CypD), a mitochondrial matrix protein that plays a key role in ischemia-reperfusion injury, can be a pharmacological target for improving outcomes after cardiac arrest (CA), especially when therapeutic hypothermia is used. Using CypD knockout mice (CypD-/-), we investigated the effects of loss of CypD on short-term and medium-term outcomes after CA. CypD-/- mice or their wild-type (WT) littermates underwent either 5 minute CA followed by resuscitation with and/or without hypothermia at 33°C-34°C (targeted temperature reached within minutes after resuscitation), or a sham procedure. Brain and cardiac injury were assessed using echocardiography, neurological scores, MRI and biomarkers. Seven day survival was compared using Kaplan-Meier estimates. The rate of restoration of spontaneous circulation was significantly higher in CypD-/- mice (with shorter cardiac massage duration) than in WT mice (P < 0.05). Loss of CypD significantly attenuated CA-induced release of troponin and S100ß protein, and limited myocardial dysfunction at 150 minutes after CA. Loss of CypD combined with hypothermia led to the best neurological and MRI scores at 24 hours and highest survival rates at 7 days compared to other groups (P < 0.05). In animals successfully resuscitated, loss of CypD had no benefits on day 7 survival while hypothermia was highly protective. Pharmacological inhibition of CypD with cyclosporine A combined with hypothermia provided similar day 7 survival than loss of CypD combined with hypothermia. CypD is a viable target to improve success of cardiopulmonary resuscitation but its inhibition is unlikely to improve long-term outcomes, unless therapeutic hypothermia is associated.

Trimetazidine Alleviates Postresuscitation Myocardial Dysfunction and Improves 96-Hour Survival in a Ventricular Fibrillation Rat Model

Background Myocardial dysfunction is a critical cause of post-cardiac arrest hemodynamic instability and circulatory failure that may lead to early mortality after resuscitation. Trimetazidine is a metabolic agent that has been demonstrated to provide protective effects in myocardial ischemia. However, whether trimetazidine protects against postresuscitation myocardial dysfunction is unknown. Methods and Results Cardiopulmonary resuscitation was initiated after 8 minutes of untreated ventricular fibrillation in Sprague-Dawley rats. Animals were randomized to 4 groups immediately after resuscitation (n=15/group): (1) normothermia control (NTC); (2) targeted temperature management; (3) trimetazidine-normothermia; (4) trimetazidine-targeted temperature management. TMZ was administered at a single dose of 10 mg/kg in rats with trimetazidine. The body temperature was maintained at 34.0°C for 2 hours and then rewarmed to 37.5°C in rats with targeted temperature management. Postresuscitation hemodynamics, 96-hours survival, and pathological analysis were assessed. Heart tissues and blood samples of additional rats (n=6/group) undergoing the same experimental procedure were collected to measure myocardial injury, inflammation and oxidative stress-related biomarkers with ELISA-based quantification assays. Compared with normothermia control, tumor necrosis factor-α, and cardiac troponin-I were significantly reduced, whereas the left ventricular ejection fraction and 96-hours survival rates were significantly improved in the 3 experimental groups. Furthermore, inflammation and oxidative stress-related biomarkers together with collagen volume fraction were significantly decreased in rats undergoing postresuscitation interventions. Conclusions Trimetazidine significantly alleviates postresuscitation myocardial dysfunction and improves survival by decreasing oxidative stress and inflammation in a ventricular fibrillation rat model. A single dose of trimetazidine administrated immediately after resuscitation can effectively improve cardiac function, whether used alone or combined with targeted temperature management.

Prostaglandin E1 attenuates post‑cardiac arrest myocardial dysfunction through inhibition of mitochondria‑mediated cardiomyocyte apoptosis

Post‑cardiac arrest myocardial dysfunction (PAMD) is a leading cause of death in patients undergoing resuscitation patients following cardiac arrest (CA). Although prostaglandin E1 (PGE1) is a clinical drug used to mitigate ischemia injury, its effect on PAMD remains unknown. In the present study, the protective effects of PGE1 on PAMD were evaluated in a rat model of CA and in a hypoxia‑reoxygenation (H/R) in vitro model. Rats were randomly assigned to CA, CA+PGE1 or sham groups. Asphyxia for 8 min followed by cardiopulmonary resuscitation were performed in the CA and CA+PGE1 groups. PGE1 was intravenously administered at the onset of return of spontaneous circulation (ROSC). PGE1 treatment significantly increased the ejection fraction and cardiac output within 4 h following ROSC and improved the survival rate, compared with the CA group. Moreover, PGE1 inactivated GSK3β, prevented mitochondrial permeability transition pore (mPTP) opening, while reducing cytochrome c and cleaved caspase‑3 expression, as well as cardiomyocyte apoptosis in the rat model. To examine the underlying mechanism, H/R H9c2 cells were treated with PGE1 at the start of reoxygenation. The changes in GSK3β activity, mPTP opening, cytochrome c and cleaved caspase‑3 expression, and apoptosis of H9c2 cells were consistent with those noted in vivo. The results indicated that PGE1 attenuated PAMD by inhibiting mitochondria‑mediated cardiomyocyte apoptosis.

Translation from animal studies of novel pharmacological therapies to clinical trials in cardiac arrest: A systematic review

BACKGROUND

There is a lack of new promising therapies to improve the dismal outcomes from cardiac arrest. The objectives of this study were: (1) To identify novel pharmacological therapies investigated in experimental animal studies and (2) to identify pharmacological therapies translated from experimental animal studies to clinical trials.

METHODS

PubMed was searched to first identify relevant experimental cardiac arrest animal models published within the last 20 years. Based on this, a list of interventions was created and a second search was performed to identify clinical trials testing one of these interventions. Data extraction was performed using standardised data extraction forms.

RESULTS

We identified 415 animal studies testing 190 different pharmacological interventions. The most commonly tested interventions were classified as vasopressors, anaesthetics/gases, or interventions aimed at molecular targets. We found 43 clinical trials testing 26 different interventions identified in the animal studies. Of these, 13 trials reported positive findings and 30 trials reported neutral findings with regards to the primary endpoint. No study showed harm of the intervention. Some interventions tested in human clinical trials, had previously been tested in animal studies without a positive effect on outcomes. A large number of animal studies was performed after publication of a clinical trial.

CONCLUSION

Numerous different pharmacological interventions have been tested in experimental animal models. Despite this only a limited number of these interventions have advanced to clinical trials, however several of the clinical trials tested interventions that were first tested in experimental animal models.

Aldehyde Dehydrogenase 2 Protects Against Post-Cardiac Arrest Myocardial Dysfunction Through a Novel Mechanism of Suppressing Mitochondrial Reactive Oxygen Species Production

Post-cardiac arrest myocardial dysfunction significantly contributes to early mortality after the return of spontaneous circulation. However, no effective therapy is available now. Aldehyde dehydrogenase 2 (ALDH2) enzyme has been shown to protect the heart from aldehyde toxicity such as 4-hydroxy-2-nonenal (4-HNE) and oxidative stress. In this study, we evaluated the effect of enhanced activity or expression of ALDH2 on post-cardiac arrest myocardial dysfunction and survival in a rat cardiac arrest model. Furthermore, we elucidated the underlying mechanisms with a focus on mitochondrial reactive oxygen species (ROS) production in a cell hypoxia/reoxygenation model. A total of 126 rats were used for the ALDH2 activation or cardiac overexpression of ALDH2 studies. Randomization was done 10 min before the respective agonist injection or in vivo gene delivery. We showed that enhanced activity or expression of ALDH2 significantly improved contractile function of the left ventricle and survival rate in rats subjected to cardiac arrest-cardiopulmonary resuscitation procedure. Moreover, ALDH2 prevented cardiac arrest-induced cardiomyocyte death from apoptosis and mitochondrial damage. Mechanistically, 4-HNE, a representative substrate of ALDH2, was dominantly increased in the hypoxia/reoxygenation-exposed cardiomyocytes. Direct addition of 4-HNE led to significantly augmented succinate accumulation and mitochondrial ROS production. Through metabolizing 4-HNE, ALDH2 significantly inhibited mitochondrial ROS production. Our findings provide compelling evidence of the cardioprotective effects of ALDH2 and therapeutic targeting this enzyme would provide an important approach for treating post-cardiac arrest myocardial dysfunction.

Age-Dependent Myocardial Dysfunction in Critically Ill Patients: Role of Mitochondrial Dysfunction

Myocardial dysfunction is common in septic shock and post-cardiac arrest but manifests differently in pediatric and adult patients. By conventional echocardiographic parameters, biventricular systolic dysfunction is more prevalent in children with septic shock, though strain imaging reveals that myocardial injury may be more common in adults than previously thought. In contrast, diastolic dysfunction in general and post-arrest myocardial systolic dysfunction appear to be more widespread in the adult population. A growing body of evidence suggests that mitochondrial dysfunction mediates myocardial depression in critical illness; alterations in mitochondrial electron transport system function, bioenergetic production, oxidative and nitrosative stress, uncoupling, mitochondrial permeability transition, fusion, fission, biogenesis, and autophagy all may play key pathophysiologic roles. In this review we summarize the epidemiologic and clinical phenotypes of myocardial dysfunction in septic shock and post-cardiac arrest and the multifaceted manifestations of mitochondrial injury in these disease processes. Since neonatal and pediatric-specific data for mitochondrial dysfunction remain sparse, conclusive age-dependent differences are not clear; instead, we highlight what evidence exists and identify gaps in knowledge to guide future research. Finally, since focal ischemic injury (with or without reperfusion) leading to myocardial infarction is predominantly an atherosclerotic disease of the elderly, this review focuses specifically on septic shock and global ischemia-reperfusion injury occurring after resuscitation from cardiac arrest.

Intra-Arrest Administration of Cyclosporine and Methylprednisolone Does Not Reduce Postarrest Myocardial Dysfunction

Objective

To determine whether the administration of intra-arrest cyclosporine (CCY) and methylprednisolone (MP) preserves left ventricular ejection fraction (LVEF) and cardiac output (CO) after return of spontaneous circulation (ROSC).

Methods

Eleven, 25-30kg female swine were randomized to receive 10mg/kg CCY + 40mg MP or placebo, anesthetized and given a transthoracic shock to induce ventricular fibrillation. After 8 minutes, standard CPR was started. After two additional minutes, the experimental agent was administered. Animals with ROSC were supported for up to 12h with norepinephrine as needed. Echocardiography was performed at baseline, and 1, 2, 6 and 12h post-ROSC. Analysis was performed using generalized estimating equations (GEE) after downsampling continuously sampled data to 5 minute epochs.

Results

Eight animals (64%) achieved ROSC after a median of 7 [IQR 5-13] min of CPR, 2 [ IQR 1-3] doses of epinephrine and 2 [IQR 1-5] defibrillation shocks. Animals receiving CCY+MP had higher post ROSC MAP (GEE coefficient -10.2, P = <0.01), but reduced cardiac output (GEE coefficient 0.8, P = <0.01) compared to placebo. There was no difference in LVEF or vasopressor use between arms.

Conclusions

Intra-arrest cyclosporine and methylprednisolone decreased post-arrest cardiac output and increased mean arterial pressure without affecting left ventricular ejection fraction.

Fast therapeutic hypothermia prevents post-cardiac arrest syndrome through cyclophilin D-mediated mitochondrial permeability transition inhibition

The opening of the mitochondrial permeability transition pore (PTP), which is regulated by the matrix protein cyclophilin D (CypD), plays a key role in the pathophysiology of post-cardiac arrest (CA) syndrome. We hypothesized that therapeutic hypothermia could prevent post-CA syndrome through a CypD-mediated PTP inhibition in both heart and brain. In addition, we investigated whether specific pharmacological PTP inhibition would confer additive protection to cooling. Adult male New Zealand White rabbits underwent 15 min of CA followed by 120 min of reperfusion. Five groups (n = 10-15/group) were studied: control group (CA only), hypothermia group (HT, hypothermia at 32-34 °C induced by external cooling at reperfusion), NIM group (injection at reperfusion of 2.5 mg/kg NIM811, a specific CypD inhibitor), HT + NIM, and sham group. The following measurements were taken: hemodynamics, echocardiography, and cellular damage markers (including S100β protein and troponin Ic). Oxidative phosphorylation and PTP opening were assessed on mitochondria isolated from both brain and heart. Acetylation of CypD was measured by immunoprecipitation in both the cerebral cortex and myocardium. Hypothermia and NIM811 significantly prevented cardiovascular dysfunction, pupillary areflexia, and early tissue damage. Hypothermia and NIM811 preserved oxidative phosphorylation, limited PTP opening in both brain and heart mitochondria and prevented increase in CypD acetylation in brain. There were no additive beneficial effects in the combination of NIM811 and therapeutic hypothermia. In conclusion, therapeutic hypothermia limited post-CA syndrome by preventing mitochondrial permeability transition mainly through a CypD-dependent mechanism.

Urocortin Treatment Improves Acute Hemodynamic Instability and Reduces Myocardial Damage in Post-Cardiac Arrest Myocardial Dysfunction

Aims

Hemodynamic instability occurs following cardiac arrest and is associated with high mortality during the post-cardiac period. Urocortin is a novel peptide and a member of the corticotrophin-releasing factor family. Urocortin has the potential to improve acute cardiac dysfunction, as well as to reduce the myocardial damage sustained after ischemia reperfusion injury. The effects of urocortin in post-cardiac arrest myocardial dysfunction remain unclear.

Methods and Results

We developed a preclinical cardiac arrest model and investigated the effects of urocortin. After cardiac arrest induced by 6.5 min asphyxia, male Wistar rats were resuscitated and randomized to either the urocortin treatment group or the control group. Urocortin (10 μg/kg) was administrated intravenously upon onset of resuscitation in the experimental group. The rate of return of spontaneous circulation (ROSC) was similar between the urocortin group (76%) and the control group (72%) after resuscitation. The left ventricular systolic (dP/dt₄₀) and diastolic (maximal negative dP/dt) functions, and cardiac output, were ameliorated within 4 h after ROSC in the urocortin-treated group compared to the control group (P<0.01). The neurological function of surviving animals was better at 6 h after ROSC in the urocortin-treated group (p = 0.023). The 72-h survival rate was greater in the urocortin-treated group compared to the control group (p = 0.044 by log-rank test). Cardiomyocyte apoptosis was lower in the urocortin-treated group (39.9±8.6 vs. 17.5±4.6% of TUNEL positive nuclei, P<0.05) with significantly increased Akt, ERK and STAT-3 activation and phosphorylation in the myocardium (P<0.05).

Conclusions

Urocortin treatment can improve acute hemodynamic instability as well as reducing myocardial damage in post-cardiac arrest myocardial dysfunction.

Intracoronary Poloxamer 188 Prevents Reperfusion Injury in a Porcine Model of ST-Segment Elevation Myocardial Infarction

Poloxamer 188 (P188) is a nonionic triblock copolymer believed to prevent cellular injury after ischemia and reperfusion. This study compared intracoronary (IC) infusion of P188 immediately after reperfusion with delayed infusion through a peripheral intravenous catheter in a porcine model of ST-segment elevation myocardial infarction (STEMI). STEMI was induced in 55 pigs using 45 min of endovascular coronary artery occlusion. Pigs were then randomized to 4 groups: control, immediate IC P188, delayed peripheral P188, and polyethylene glycol infusion. Heart tissue was collected after 4 h of reperfusion. Assessment of mitochondrial function or infarct size was performed. Mitochondrial yield improved significantly with IC P188 treatment compared with control animals (0.25% vs. 0.13%), suggesting improved mitochondrial morphology and survival. Mitochondrial respiration and calcium retention were also significantly improved with immediate IC P188 compared with control animals (complex I respiratory control index: 7.4 vs. 3.7; calcium retention: 1,152 nmol vs. 386 nmol). This benefit was only observed with activation of complex I of the mitochondrial respiratory chain, suggesting a specific effect from ischemia and reperfusion on this complex. Infarct size and serum troponin I were significantly reduced by immediate IC P188 infusion (infarct size: 13.9% vs. 41.1%; troponin I: 19.2 μg/l vs. 77.4 μg/l). Delayed P188 and polyethylene glycol infusion did not provide a significant benefit. These results demonstrate that intracoronary infusion of P188 immediately upon reperfusion significantly reduces cellular and mitochondrial injury after ischemia and reperfusion in this clinically relevant porcine model of STEMI. The timing and route of delivery were critical to achieve the benefit.

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STEMI remains a significant cause of in-hospital mortality, and up to 20% of people go on to develop heart failure.

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P188 is a nonionic triblock copolymer believed to prevent cellular injury after ischemia and reperfusion. The CORE trial examined P188 for STEMI patients showing no benefit when it was infused through a peripheral IV catheter approximately 30 min after revascularization with thrombolytic therapy.

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STEMI was induced in pigs using endovascular coronary artery occlusion to compare intracoronary infusion of P188 immediately after revascularization to infusion of P188 through a peripheral IV catheter 30 min after revascularization. Immediate intracoronary infusion of vehicle control and PEG, a rheological control, were also compared.

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Intracoronary infusion of P188 immediately upon reperfusion reduced infarct size by 68% compared with delayed peripheral P188 infusion, which was similar to vehicle control.

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Mitochondrial respiration and calcium stress tolerance were preserved in the ischemic tissue of pigs treated with immediate intracoronary P188 infusion. Mitochondria from pigs with delayed peripheral P188 infusion were no different from control pigs.

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By reducing infarct size and mitochondrial dysfunction, immediate intracoronary infusion of P188 may provide a therapeutic strategy to improve post-STEMI outcomes. The timing and route of delivery were critical to the observed benefit.

Protective effects of cyclosporine A and hypothermia on neuronal mitochondria in a rat asphyxial cardiac arrest model

BACKGROUND

Cyclosporine A (CsA) was neuroprotective in the settings of traumatic brain injury and stroke. We sought to investigate the protective effects of CsA and hypothermia on neuronal mitochondria after cardiac arrest.

METHODS AND RESULTS

Five groups were included: sham (S), normothermia (N), CsA (C), hypothermia (H), and CsA plus hypothermia (C+H). Cardiac arrest was induced by 10min of asphyxia. CsA (10mg/kg) was administered immediately after return of spontaneous circulation in the CsA groups. Temperature of the rats was maintained at 33±0.5°C after return of spontaneous circulation in the hypothermia groups. Hippocampal mitochondria were measured after 2h of resuscitation. Mitochondrial transmembrane potential was significantly higher in the C, the H, and the C+H groups than in the N group and was higher in the C+H group than in the C and the H groups. Cytosolic cytochrome c was significantly higher in the N group. Superoxide dismutase activity was significantly lower in the N group than in the other groups and was higher in the C and the C+H groups than in the H group. Malondialdehyde concentration was significantly higher in the N group.

CONCLUSIONS

CsA or hypothermia used immediately after resuscitation enhanced mitochondrial transmembrane potential, kept cytochrome c from releasing out of the mitochondria, increased superoxide dismutase activity, and decreased malondialdehyde concentration in hippocampus. Moreover, the protective effects of CsA were reinforced by hypothermia. One of the mechanisms that hypothermia protected neuronal mitochondria from damage was inhibiting the opening of mitochondrial permeability transition pore.

Breakthrough in cardiac arrest: reports from the 4th Paris International Conference

Jean-Luc Diehl The French Intensive Care Society organized on 5th and 6th June 2014 its 4th "Paris International Conference in Intensive Care", whose principle is to bring together the best international experts on a hot topic in critical care medicine. The 2014 theme was "Breakthrough in cardiac arrest", with many high-quality updates on epidemiology, public health data, pre-hospital and in-ICU cares. The present review includes short summaries of the major presentations, classified into six main chapters: Epidemiology of CA Pre-hospital management Post-resuscitation management: targeted temperature management Post-resuscitation management: optimizing organ perfusion and metabolic parameters Neurological assessment of brain damages Public healthcare.

Myocardial Dysfunction and Shock after Cardiac Arrest

Postarrest myocardial dysfunction includes the development of low cardiac output or ventricular systolic or diastolic dysfunction after cardiac arrest. Impaired left ventricular systolic function is reported in nearly two-thirds of patients resuscitated after cardiac arrest. Hypotension and shock requiring vasopressor support are similarly common after cardiac arrest. Whereas shock requiring vasopressor support is consistently associated with an adverse outcome after cardiac arrest, the association between myocardial dysfunction and outcomes is less clear. Myocardial dysfunction and shock after cardiac arrest develop as the result of preexisting cardiac pathology with multiple superimposed insults from resuscitation. The pathophysiology involves cardiovascular ischemia/reperfusion injury and cardiovascular toxicity from excessive levels of inflammatory cytokine activation and catecholamines, among other contributing factors. Similar mechanisms occur in myocardial dysfunction after cardiopulmonary bypass, in sepsis, and in stress-induced cardiomyopathy. Hemodynamic stabilization after resuscitation from cardiac arrest involves restoration of preload, vasopressors to support arterial pressure, and inotropic support if needed to reverse the effects of myocardial dysfunction and improve systemic perfusion. Further research is needed to define the role of postarrest myocardial dysfunction on cardiac arrest outcomes and identify therapeutic strategies.

Neuroprotective strategies and neuroprognostication after cardiac arrest

Neurocognitive disturbances are common among survivors of cardiac arrest (CA). Although initial management of CA, including bystander cardiopulmonary resuscitation, optimal chest compression, and early defibrillation, has been implemented continuously over the last years, few therapeutic interventions are available to minimize or attenuate the extent of brain injury occurring after the return of spontaneous circulation. In this review, we discuss several promising drugs that could provide some potential benefits for neurological recovery after CA. Most of these drugs have been investigated exclusively in experimental CA models and only limited clinical data are available. Further research, which also considers combined neuroprotective strategies that target multiple pathways involved in the pathophysiology of postanoxic brain injury, is certainly needed to demonstrate the effectiveness of these interventions in this setting. Moreover, the evaluation of neurological prognosis of comatose patients after CA remains an important challenge that requires the accurate use of several tools. As most patients with CA are currently treated with targeted temperature management (TTM), combined with sedative drug therapy, especially during the hypothermic phase, the reliability of neurological examination in evaluating these patients is delayed to 72-96 h after admission. Thus, additional tests, including electrophysiological examinations, brain imaging and biomarkers, have been largely implemented to evaluate earlier the extent of brain damage in these patients.

The effect of cyclosporine A in hemorrhagic shock model of rats

BACKGROUND

The inhibition of mitochondrial permeability transition pore opening during ischemia-reperfusion can ameliorate injuries. This study aimed to investigate the effects of cyclosporine A (CsA) in rats after hemorrhagic shock.

METHODS

Male Sprague-Dawley rats were subjected to pressure-controlled hemorrhagic shock (mean arterial pressure, 38 ± 1 mm Hg) for 90 minutes. After the hemorrhagic shock period, rats were randomly allocated to one of three groups as follows: a control group, a CsA10 group, or a CsA50 group. CsA for the treatment groups (10 mg/kg for the CsA10 group and 50 mg/kg for the CsA50 group) or normal saline for the control group was administered via tail vein for 10 minutes, and shed blood was transfused for 15 minutes. For the survival study, animals were observed for up to 9 hours, and their survival time was recorded until death. Separate experiments were performed to examine the effect of CsA on inflammatory responses and liver injury. Rats were sacrificed at 210 minutes after the shock period, and blood and liver tissues were harvested.

RESULTS

Survival times were shown to be significantly longer in the CsA-treated groups (i.e., the CsA10 and CsA50 groups) than in the control group. Plasma interleukin-6 and thiobarbituric acid-reactive substances were significantly lower in the CsA50 group than in the control group and phosphorylation of Akt, GSK-3β, and Bad were significantly increased in the CsA-treated groups compared with the control group. Expressions of Bcl-2, cleaved caspase 3, and cytoplasmic cytochrome C were significantly decreased in the CsA-treated groups compared with the control group. Although histologic liver injury was not significantly different among the groups, ultrastructural changes of mitochondria were more prominent in the control group than in the CsA-treated groups.

CONCLUSION

CsA increased survival time, decreased proinflammatory cytokine and lipid peroxidation, and augmented Akt survival pathways in rats subjected to pressure-controlled hemorrhagic shock.

Minor Changes in Core Temperature Prior to Cardiac Arrest Influence Outcomes: An Experimental Study

AIM

To investigate whether slight variations in core temperature prior to cardiac arrest (CA) influence short-term outcomes and mitochondrial functions.

METHODS AND MATERIALS

Three groups of New Zealand White rabbits (n = 12/group) were submitted to 15 minutes of CA at 38°C (T-38 group), 39°C (T-39), or 40°C (T 40) and 120 minutes of reperfusion. A Sham-operated group (n = 6) underwent only surgery. Restoration of spontaneous circulation (ROSC), survival, hemodynamics, and pupillary reactivity were recorded. Animals surviving to the end of the observation period were euthanized to assess fresh brain and heart mitochondrial functions (permeability transition and oxidative phosphorylation). Markers of brain and heart damages were also measured.

RESULTS

The duration of asphyxia required to induce CA was significantly lower in the T-40 group when compared to the T-38 group (P < .05). The rate of ROSC was >80% in all groups (P = nonsignificant [ns]). Survival significantly differed among the T-38, T-39, and T-40 groups: 10 (83%) of 12, 7 (58%) of 12, and 4 (33%) of 12, respectively (log-rank test, P = .027). At the end of the protocol, none of the animals in the T-40 group had pupillary reflexes compared to 8 (67%) of 12 in the T-38 group (P < .05). Troponin and protein S100B were significantly higher in the T-40 versus T-38 group (P < .05). Cardiac arrest significantly impaired both inner mitochondrial membrane integrity and oxidative phosphorylation in all groups. Brain mitochondria disorders were significantly more severe in the T-40 group compared to the T-38 group (P < .05).

CONCLUSION

Small changes in body temperature prior to asphyxial CA significantly influence brain mitochondrial functions and short-term outcomes in rabbits.

Anaesthetic Postconditioning at the Initiation of CPR Improves Myocardial and Mitochondrial Function in a Pig Model of Prolonged Untreated Ventricular Fibrillation

BACKGROUND

Anaesthetic postconditioning (APoC) attenuates myocardial injury following coronary ischaemia/reperfusion. We hypothesised that APoC at the initiation of cardiopulmonary resuscitation (CPR) will improve post resuscitation myocardial function along with improved mitochondrial function in a pig model of prolonged untreated ventricular fibrillation.

METHODS

In 32 pigs isoflurane anaesthesia was discontinued prior to induction of ventricular fibrillation that was left untreated for 15 min. At the initiation of CPR, 15 animals were randomised to controls (CON), and 17 to APoC with 2 vol% sevoflurane during the first 3 min CPR. Pigs were defibrillated after 4 min of CPR. After return of spontaneous circulation (ROSC), isoflurane was restarted at 0.8-1.5 vol% in both groups. Systolic and diastolic blood pressures were measured continuously. Of the animals that achieved ROSC, eight CON and eight APoC animals were randomised to have their left ventricular ejection fraction (LVEF%) assessed by echocardiography at 4h. Seven CON and nine APoC were randomised to euthanasia 15 min after ROSC to isolate mitochondria from the left ventricle for bioenergetic studies.

RESULTS

ROSC was achieved in 10/15 CON and 15/17 APoC animals. APoC improved haemodynamics during CPR and post-CPR LVEF%. Mitochondrial ATP synthesis, coupling of oxidative phosphorylation and calcium retention capacity were improved in cardiac mitochondria isolated after APoC.

CONCLUSIONS

In a porcine model of prolonged untreated cardiac arrest, APoC with inhaled sevoflurane at the initiation of CPR, is associated with preserved mitochondrial function and improved post resuscitation myocardial dysfunction. Approved by the Institutional Animal Care Committee of the Minneapolis Medical Research Foundation of Hennepin County Medical Center (protocol number 11-05).

Ubiquitous protective effects of cyclosporine A in preventing cardiac arrest-induced multiple organ failure

Opening of the mitochondrial permeability transition pore (mPTP) appears to be a pivotal event in myocardial ischemia-reperfusion (I/R) injury. Resuscitated cardiac arrest (CA) leads to the post-CA syndrome that encompasses, not only myocardial dysfunction, but also brain injury, failure of other organs (kidney, liver, or lung), and systemic response to I/R. We aimed to determine whether cyclosporine A (CsA) might prevent multiple organ failure following CA through a ubiquitous mPTP inhibition in each distant vital organ. Anesthetized New Zealand White rabbits were subjected to 15 min of CA and 120 min of reperfusion. At the onset of resuscitation, the rabbits received CsA, its non-immunosuppressive derivative NIM811, or vehicle (controls). Survival, hemodynamics, brain damage, organ injuries, and systemic I/R response were analyzed. Fresh mitochondria were isolated from the brain, heart, kidney, liver, and lung to assess both oxidative phosphorylation and permeability transition. CsA analogs significantly improved short-term survival and prevented multiple organ failure, including brain damage and myocardial dysfunction (P < 0.05 vs. controls). Susceptibility of mPTP opening was significantly increased in heart, brain, kidney, and liver mitochondria isolated from controls, while mitochondrial respiration was impaired (P < 0.05 vs. sham). CsA analogs prevented these mitochondrial dysfunctions (P < 0.05 vs. controls). These results suggest that CsA and NIM811 can prevent the post-CA syndrome through a ubiquitous mitochondrial protective effect at the level of each major distant organ.