Marked activation of complement and leukocytes and an increase in the concentrations of soluble endothelial adhesion molecules during cardiopulmonary resuscitation and early reperfusion after cardiac arrest in humans

A Commentary on the Effect of Targeted Temperature Management in Patients Resuscitated from Cardiac Arrest

The members of the International Liaison Committee on Resuscitation (ILCOR) Advanced Life Support Task Force have written a comprehensive summary of trials of the effectiveness of induced hypothermia (IH) or targeted temperature management (TTM) in comatose patients after cardiac arrest (CA). However, in-depth analysis of these studies is incomplete, especially since there was no significant difference in primary outcome between hypothermia versus normothermia in the recently reported TTM2 trial. We critically appraise trials of IH/TTM versus normothermia to characterize reasons for the lack of treatment effect, based on a previously published framework for what to consider when the primary outcome fails. We found a strong biologic rationale and external clinical evidence that IH treatment is beneficial. Recent TTM trials mainly included unselected patients with a high rate of bystander cardiopulmonary resuscitation. The treatment was not applied as intended, which led to a large delay in achievement of target temperature. While receiving intensive care, sedative drugs were likely used that might have led to increased neurologic damage as were antiplatelet drugs that could be associated with increased acute stent thrombosis in hypothermic patients. It is reasonable to still use or evaluate IH treatment in patients who are comatose after CA as there are multiple plausible reasons why IH compared to normothermia did not significantly improve neurologic outcome in the TTM trials.

Neuroinflammation and the immune system in hypoxic ischaemic brain injury pathophysiology after cardiac arrest

Hypoxic ischaemic brain injury after resuscitation from cardiac arrest is associated with dismal clinical outcomes. To date, most clinical interventions have been geared towards the restoration of cerebral oxygen delivery after resuscitation; however, outcomes in clinical trials are disappointing. Therefore, alternative disease mechanism(s) are likely to be at play, of which the response of the innate immune system to sterile injured tissue in vivo after reperfusion has garnered significant interest. The innate immune system is composed of three pillars: (i) cytokines and signalling molecules; (ii) leucocyte migration and activation; and (iii) the complement cascade. In animal models of hypoxic ischaemic brain injury, pro-inflammatory cytokines are central to propagation of the response of the innate immune system to cerebral ischaemia-reperfusion. In particular, interleukin-1 beta and downstream signalling can result in direct neural injury that culminates in cell death, termed pyroptosis. Leucocyte chemotaxis and activation are central to the in vivo response to cerebral ischaemia-reperfusion. Both parenchymal microglial activation and possible infiltration of peripherally circulating monocytes might account for exacerbation of an immunopathological response in humans. Finally, activation of the complement cascade intersects with multiple aspects of the innate immune response by facilitating leucocyte activation, further cytokine release and endothelial activation. To date, large studies of immunomodulatory therapies have not been conducted; however, lessons learned from historical studies using therapeutic hypothermia in humans suggest that quelling an immunopathological response might be efficacious. Future work should delineate the precise pathways involved in vivo in humans to target specific signalling molecules.

Predictive value of soluble CD59 for poor 28-day neurological prognosis and all-cause mortality in patients after cardiopulmonary resuscitation: a prospective observatory study

BACKGROUND

sCD59, as a soluble form of CD59, is observed in multiple types of body fluids and correlated with the cell damage after ischemia/reperfusion injury. This study aims to observe the dynamic changes of serum sCD59 in patients after restoration of spontaneous circulation (ROSC) and explore the association of serum sCD59 with neurological prognosis and all-cause mortality in patients after ROSC.

METHODS

A total of 68 patients after ROSC were prospectively recruited and divided into survivors (n = 23) and non-survivors (n = 45) groups on the basis of 28-day survival. Twenty healthy volunteers were enrolled as controls. Serum sCD59 and other serum complement components, including sC5b-9, C5a, C3a, C3b, C1q, MBL, Bb, and pro-inflammatory mediators tumor necrosis factor (TNF)-α, interleukin-6 (IL-6), neurological damage biomarkers neuron-specific enolase (NSE) and soluble protein 100β (S100β) were measured by enzyme linked immunosorbent assay on day 1, 3, and 7 after ROSC. Neurologic outcome was assessed using cerebral performance category scores, with poor neurologic outcome defined as 3-5 points.

RESULTS

In the first week after ROSC, serum levels of sCD59, sC5b-9, C5a, C3a, C3b, C1q, MBL, Bb, TNF-α, IL-6, NSE and S100β were significantly elevated in patients after ROSC compared to healthy volunteers, with a significant elevation in the non-survivors compared to survivors except serum C1q and MBL. Serum sCD59 levels were positively correlated with serum sC5b-9, TNF-α, IL-6, NSE, S100β, SOFA score and APACHE II score. Moreover, serum sCD59 on day 1, 3, and 7 after ROSC could be used for predicting poor 28-day neurological prognosis and all-cause mortality. Serum sCD59 on day 3 had highest AUCs for predicting poor 28-day neurological prognosis [0.862 (95% CI 0.678-0.960)] and 28-day all-cause mortality [0.891 (95% CI 0.769-0.962)]. In multivariate logistic regression analysis, the serum level of sCD59_D1 was independently associated with poor 28-day neurological prognosis and all-cause mortality.

CONCLUSIONS

The elevated serum level of sCD59 was positively correlated with disease severity after ROSC. Moreover, serum sCD59 could have good predictive values for the poor 28-day neurological prognosis and all-cause mortality in patients after ROSC.

A randomized diet-induced weight-loss intervention reduces plasma complement C3: Possible implication for endothelial dysfunction

OBJECTIVE

Complement C3 and other components of the alternative pathway are higher in individuals with obesity. Moreover, C3 has been identified as a risk factor for cardiovascular disease. This study investigated whether, and how, a weight-loss intervention reduced plasma C3, activated C3 (C3a), and factor D and explored potential biological effects of such a reduction.

METHODS

The study measured plasma C3, C3a, and factor D by ELISA and measured visceral adipose tissue, subcutaneous adipose tissue, and intrahepatic lipid by magnetic resonance imaging in lean men (n = 25) and men with abdominal obesity (n = 52). The men with obesity were randomized to habitual diet or an 8-week dietary weight-loss intervention.

RESULTS

The intervention significantly reduced C3 (-0.15 g/L [95% CI: -0.23 to -0.07]), but not C3a or factor D. The C3 reduction was mainly explained by reduction in visceral adipose tissue but not subcutaneous adipose tissue or intrahepatic lipid. This reduction in C3 explained a part of the weight-loss-induced improvement of markers of endothelial dysfunction, particularly the reduction in soluble endothelial selectin and soluble intercellular adhesion molecule.

CONCLUSIONS

Diet-induced weight loss in men with abdominal obesity could be a way to lower plasma C3 and thereby improve endothelial dysfunction. C3 reduction may be part of the mechanism via which diet-induced weight loss could ameliorate the risk of cardiovascular disease in men with abdominal obesity.

Association between inflammatory markers and survival in comatose, resuscitated out-of-hospital cardiac arrest patients

OBJECTIVES

Prognostication after out-of-hospital cardiac arrest (OHCA) remains challenging. The inflammatory response after OHCA has been associated with increased mortality. This study investigates the associations and predictive value between inflammatory markers and outcome in resuscitated OHCA patients.

DESIGN

The study is based on post hoc analyses of a double-blind controlled trial, where resuscitated OHCA patients were randomized to receive either exenatide or placebo. Blood was analyzed for levels of inflammatory markers the day following admission. Primary endpoint was time to death for up to 180 days. Secondary endpoints included 180-day mortality and poor neurological outcome after 180 days, defined as a cerebral performance category (CPC) of 3 to 5.

RESULTS

Among 110 included patients we found significant associations between higher leucocyte quartile and increasing mortality in univariable analysis (OR 2.6 (95%CI 1.6-4.2), p < .001), as well as in multivariable analysis (OR 2.1 (95%CI 1.1-4.0), p = .02). A significant association was found between higher neutrophil quartile and increasing mortality in univariable analysis (OR 3.0 (95%CI 1.8-5.0), p < .001) as well as multivariable analysis (OR 2.4 (95%CI 1.2-4.6), p = .01). Leucocyte and neutrophil levels were predictive of poor outcome after 180 days with area under the receiver operating characteristics curves of 0.79 and 0.81, respectively. We found no associations between CRP and lymphocyte levels versus outcome.

CONCLUSIONS

Total leucocyte count and neutrophil levels measured the first day following OHCA were significantly associated with 180-day all-cause mortality and may potentially act as early predictors of outcome.

CLINICAL TRIAL REGISTRATION

www.clinicaltrials.gov, unique identifier: NCT02442791.

Complement activation is associated with poor outcome after out-of-hospital cardiac arrest

BACKGROUND

Cardiopulmonary resuscitation after cardiac arrest initiates a whole-body ischemia-reperfusion injury, which may activate the innate immune system, including the complement system. We hypothesized that complement activation and subsequent release of soluble endothelial activation markers were associated with cerebral outcome including death.

METHODS

Outcome was assessed at six months and defined by cerebral performance category scale (1-2; good outcome, 3-5; poor outcome including death) in 232 resuscitated out-of-hospital cardiac arrest patients. Plasma samples obtained at admission and day three were analysed for complement activation products C3bc, the soluble terminal complement complex (sC5b-9), and soluble CD14. Endothelial cell activation was measured by soluble markers syndecan-1, sE-selectin, thrombomodulin, and vascular cell adhesion molecule.

RESULTS

Forty-nine percent of the patients had good outcome. C3bc and sC5b-9 were significantly higher at admission compared to day three (p < 0.001 for both) and in patients with poor compared to good outcome (p = 0.03 and p < 0.001, respectively). Unadjusted, higher sC5b-9 at admission was associated with poor outcome (odds ratio 1.08 (95% CI 1.01-1.14), p = 0.024). Adjusted, sC5b-9 was still associated with outcome, but the association became non-significant when time to return-of-spontaneous-circulation above 25 min was included as a covariate. Endothelial cell activation markers increased from admission to day three, but only sE-selectin and thrombomodulin were significantly higher in patients with poor versus good outcome (p = 0.004 and p = 0.03, respectively) and correlated to sCD14 and sC5b-9/C3bc, respectively.

CONCLUSION

Complement system activation, reflected by sC5b-9 at admission, leading to subsequent endothelial cell activation, was associated with poor outcome in out-of-hospital cardiac arrest patients.

European Resuscitation Council and European Society of Intensive Care Medicine guidelines 2021: post-resuscitation care

The European Resuscitation Council (ERC) and the European Society of Intensive Care Medicine (ESICM) have collaborated to produce these post-resuscitation care guidelines for adults, which are based on the 2020 International Consensus on Cardiopulmonary Resuscitation Science with Treatment Recommendations. The topics covered include the post-cardiac arrest syndrome, diagnosis of cause of cardiac arrest, control of oxygenation and ventilation, coronary reperfusion, haemodynamic monitoring and management, control of seizures, temperature control, general intensive care management, prognostication, long-term outcome, rehabilitation and organ donation.

European Resuscitation Council and European Society of Intensive Care Medicine Guidelines 2021: Post-resuscitation care

The European Resuscitation Council (ERC) and the European Society of Intensive Care Medicine (ESICM) have collaborated to produce these post-resuscitation care guidelines for adults, which are based on the 2020 International Consensus on Cardiopulmonary Resuscitation Science with Treatment Recommendations. The topics covered include the post-cardiac arrest syndrome, diagnosis of cause of cardiac arrest, control of oxygenation and ventilation, coronary reperfusion, haemodynamic monitoring and management, control of seizures, temperature control, general intensive care management, prognostication, long-term outcome, rehabilitation, and organ donation.

Membrane Attack Complex in Myocardial Ischemia/Reperfusion Injury: A Systematic Review for Post Mortem Applications

The complement system has a significant role in myocardial ischemia/reperfusion injury, being responsible for cell lysis and amplification of inflammatory response. In this context, several studies highlight that terminal complement complex C5b-9, also known as the membrane attack complex (MAC), is a significant contributor. The MAC functions were studied by many researchers analyzing the characteristics of its activation in myocardial infarction. Here, a systematic literature review was reported to evaluate the principal features, advantages, and limits (regarding the application) of complement components and MAC in post mortem settings to perform the diagnosis of myocardial ischemia/infarction. The review was performed according to specific inclusion and exclusion criteria, and a total of 26 studies were identified. Several methods studied MAC, and each study contributes to defining better how and when it affects the myocardial damage in ischemic/reperfusion injury. The articles were discussed, focusing on the specificity, sensibility, and post mortem stability of MAC as a marker of myocardial ischemia/infarction, supporting the usefulness in routine post mortem investigations.

The complement lectin pathway protein MAp19 and out-of-hospital cardiac arrest: Insights from two randomized clinical trials

Aim:

Activation of the complement system is known to be a potent inducer of systemic inflammation, which is an important component of post-cardiac arrest syndrome. Mannan-binding-lectin associated protein of 19 kDa (MAp19) is suggested to be a regulatory component of the lectin pathway of complement activation. The aims of this study were to describe serial levels of MAp19 protein in comatose survivors of out-of-hospital cardiac arrest (OHCA), to evaluate the effect of two different regimes of targeted temperature management and to investigate the possible association between levels of MAp19 and mortality.

Methods:

In this post-hoc study, we analysed data from two large randomized controlled studies: ‘Targeted temperature management at 33 degrees C versus 36 degrees C after cardiac arrest’ (TTM) and ‘Targeted temperature management for 48 versus 24 h and neurological outcome after out-of-hospital cardiac arrest’ (TTH). We measured serial levels of MAp19 in 240 patients within 72 h after OHCA and in 82 healthy controls. The effect of targeted temperature management on MAp19 levels was analysed according to temperature allocation in main trials.

Results:

MAp19 levels were significantly lower in OHCA patients within 48 h after OHCA (p-values &lt;0.001) compared with healthy controls. A target temperature at 33°C compared with 36°C for 24 h was associated with significantly lower levels of MAp19 (–57 ng/mL (95% confidence interval (CI): –97 to −16 mg/mL), p=0.006). Target temperature at 33°C for 48 h compared with 24 h was not associated with a difference in MAp19 levels (–31 ng/mL (95% CI: –120 to 60 mg/mL), p=0.57). Low MAp19 levels at admission were associated with higher 30-day mortality (12% vs. 38%, plog-rank =0.0008), also in adjusted analysis (two-fold higher, hazard ratio =0.48 (95% CI: 0.31 to 0.75), p=0.001). Analysis of MAp19 levels at 24–72 h showed they were not associated with 30-day mortality.

Conclusion:

Survivors after OHCA have lower levels of MAp19 protein compared with healthy controls. A targeted temperature management at 33°C compared with 36°C was associated with significantly lower MAp19 levels, whereas target temperature at 33°C for 48 h compared with 24 h did not influence MAp19 protein levels. Low MAp19 levels at admission were independently associated with increased mortality.

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.

Xuezhikang improves the outcomes of cardiopulmonary resuscitation in rats by suppressing the inflammation response through TLR4/NF-κB pathway

BACKGROUND/AIMS

Xuezhikang (XZK), a red yeast rice extract with lipid-lowering effect, contains a family of naturally statins, such as lovastatin. In recent years, its effect beyond the regulation of lipids has also been received increasing attention. Therefore, the purpose of this study was to explore the protective effects and possible molecular mechanisms of XZK on brain injury after cardiac arrest (CA) and cardiopulmonary resuscitation (CPR), and to investigate whether it has a dose-dependent effect and the difference with lovastatin.

METHODS

Rats were treated with low-dose XZK (XZK-L, 20 mg/kg/d), high-dose XZK (XZK-H, 200 mg/kg/d) and lovastatin by gavage once daily for 2 weeks before CA. The levels of TNF-α, IL-6 and IL-1β were evaluated at 1, 4, and 72 h post-CA/CPR. The survival rate, neurological deficit score (NDS), and expression of TLR4, phosphorylated NF-κB and TNF-α in hippocampal tissues were evaluated at 72 h post-CA/CPR.

RESULTS

CA/CPR induced a significant increase in serum TNF-α, IL-6 and IL-1β, as well as increased expressions of TLR4, phosphorylated NF-κB and TNF-α in the hippocampus. Both low-dose and high-dose XZK treatment inhibited the expression of these inflammatory cytokines. In addition, it reduced the number of defibrillations and shortened the duration of CPR required for return of spontaneous circulation (ROSC). XZK treatment also improved neurological function and 72-hour survival rate in rats. However, high-dose XZK was superior to lovastatin in the suppression of IL-1β mRNA level and TNF-α protein level in hippocampal tissue after CPR. There were no significant differences observed among high-dose XZK, low-dose XZK and lovastatin groups in other respects.

CONCLUSION

These results indicated that XZK had a protective effect against brain injury post-CA/CPR. The mechanisms underlying the protective effects of XZK may be related to the suppressing of CA/CPR-induced inflammatory response through the inhibiting TLR4/NF-κB signaling pathway.

The complement lectin pathway after cardiac arrest

The lectin pathway (LP) of the complement system may initiate inflammatory reactions when body tissue is altered. We aimed to investigate the levels of the LP proteins in out-of-hospital cardiac arrest patients, and to compare these with healthy individuals. Furthermore, we aimed to clarify whether the duration of targeted temperature management influenced LP protein levels, and we further examined whether LP proteins were associated with 30-day mortality. We included 82 patients resuscitated from out-of-hospital cardiac arrest. The patients were randomly assigned to 24 or 48 hours of targeted temperature management at 33 ± 1°C. Blood samples were obtained 22, 46 and 70 hours after target temperature was reached. Levels of the LP proteins (mannan-binding lectin [MBL], M-ficolin, H-ficolin, collectin liver 1 [CL-L1], MBL-associated serine protease 1 [MASP-1], MASP-2, MASP-3 and MBL-associated protein of 44 kDa [MAp44]) were measured using time-resolved immunofluorometric assays. Data from 82 gender matched healthy individuals were used for comparison. Levels of CL-L1, MASP-1, MASP-2 and MAp44 were significantly higher, whereas M-ficolin levels were significantly lower in cardiac arrest patients compared with healthy individuals. MASP-2, MASP-3 and M-ficolin levels changed significantly when comparing 24 and 48 hours of targeted temperature management. The LP protein levels were not different between 30-day survivors and non-survivors after cardiac arrest. The differences in LP protein levels between patients and healthy individuals may indicate that cardiac arrest patients have an activated LP. Overall, the LP protein levels were not influenced by the duration of targeted temperature management, and the levels were not associated with 30-day mortality.

Predicting the outcomes for out-of-hospital cardiac arrest patients using multiple biomarkers and suspension microarray assays

Predicting the prognosis for cardiac arrest is still challenging. Combining biomarkers from diverse pathophysiological pathways may provide reliable indicators for the severity of injury and predictors of long-term outcomes. We investigated the feasibility of using a multimarker strategy with key independent biomarkers to improve the prediction of outcomes in cardiac arrest. Adult out-of-hospital cardiac arrest patients with sustained return of spontaneous circulation were prospectively enrolled in this study. Blood samples were taken at 2 and 24 hours after cardiac arrest. Suspension microarray assays were used to test 21 different biomarkers. A total of 99 patients were enrolled, 45 of whom survived to hospital discharge. We identified 11 biomarkers that, when combined with clinical variables and factors of APACHE II score and history of arrhythmia, were independent determinants for outcome of in-hospital mortality (concordance = 0.9249, standard error = 0.0779). Three biomarkers combined with APACHE II and age were independent determinants for favorable neurological outcome at hospital discharge (area under the receiver-operator characteristic curve, 0.938; 95% confidence interval, 0.854 ~ 1.0). In conclusion, a systemic multiple biomarker approach using suspension microarray assays can identify independent predictors and model the outcomes of cardiac arrest patients during the post-cardiac arrest period.

Predictive value of interleukin-6 in post-cardiac arrest patients treated with targeted temperature management at 33 °C or 36 °C

AIM

Post-cardiac arrest syndrome (PCAS) is characterized by systemic inflammation, however data on the prognostic value of inflammatory markers is sparse. We sought to investigate the importance of systemic inflammation, assessed by interleukin-6 (IL-6) in comatose survivors of out-of-hospital cardiac arrest.

METHODS

A total of 682 patients enrolled in the Target Temperature Management (TTM) trial, surviving >24h with available IL-6 data were included. IL-6 was measured on days 1, 2 and 3 after return of spontaneous circulation. Severity of PCAS was assessed daily by the Sequential Organ Failure Assessment score. Survival status was recorded at 30 days.

RESULTS

High levels of IL-6 at day 1-3 (all p<0.0001) were independently associated with severity of PCAS with no interaction of target temperature (all p=NS). IL-6 levels did not differ between temperature groups (p(interaction)=0.99). IL-6 levels at day 2 (p<0.0001) and day 3 (p<0.0001) were associated with crude mortality. Adjusted Cox proportional-hazards analysis showed that a two-fold increase of IL-6 levels at day 2 (HR=1.15 (95% CI: 1.07-1.23), p=0.0002) and day 3 (HR=1.18 (95% CI: 1.09-1.27), p<0.0001) were associated with mortality. IL-6 levels at day 3 had the highest discriminative value in predicting mortality (AUC=0.66). IL-6 did not significantly improve 30-day mortality prediction compared to traditional prognostic factors (p=0.08).

CONCLUSIONS

In patients surviving >24h following cardiac arrest, IL-6 levels were significantly elevated and associated with severity of PCAS with no significant influence of target temperature. High IL-6 levels were associated with increased mortality. Measuring levels of IL-6 did not provide incremental prognostic value.

Mild hypothermia inhibits systemic and cerebral complement activation in a swine model of cardiac arrest

Complement activation has been implicated in ischemia/reperfusion injury. This study aimed to determine whether mild hypothermia (HT) inhibits systemic and cerebral complement activation after resuscitation from cardiac arrest. Sixteen minipigs resuscitated from 8 minutes of untreated ventricular fibrillation were randomized into two groups: HT group (n=8), treated with HT (33°C) for 12 hours; and normothermia group (n=8), treated similarly as HT group except for cooling. Blood samples were collected at baseline and 0.5, 6, 12, and 24 hours after return of spontaneous circulation (ROSC). The brain cortex was harvested 24 hours after ROSC. Complement and pro-inflammatory markers were detected using enzyme-linked immunosorbent assay. Neurologic deficit scores were evaluated 24 hours after ROSC. C1q, Bb, mannose-binding lectin (MBL), C3b, C3a, C5a, interleukin-6, and tumor necrosis factor-α levels were significantly increased under normothermia within 24 hours after ROSC. However, these increases were significantly reduced by HT. Hypothermia decreased brain C1q, MBL, C3b, and C5a contents 24 hours after ROSC. Hypothermic pigs had a better neurologic outcome than normothermic pigs. In conclusion, complement is activated through classic, alternative, and MBL pathways after ROSC. Hypothermia inhibits systemic and cerebral complement activation, which may provide an additional mechanism of cerebral protection.

Impaired NO-mediated vasodilatation in rat coronary arteries after asphyxial cardiac arrest

BACKGROUND

Cardiovascular dysfunction after cardiac arrest is a common finding. It is unknown whether altered endothelium-mediated vasoreactivity contributes to this dysfunction. We hypothesised that cardiac arrest and resuscitation results in impaired endothelial function. This was addressed by measurements of inflammatory and endothelial plasma markers and of endothelium-dependent vasodilatation in coronary and mesenteric arteries in rats after cardiac arrest and resuscitation.

METHODS

Male Sprague Dawley rats underwent either asphyxia-induced cardiac arrest for 5 min and subsequent resuscitation (n = 30) or a sham procedure (control animals, n = 39). Animals were euthanised after 30 min or 2 h. Blood was analysed for TNF-α, IL-1β, IL-6, IL-10, sE-selectin, sP-selectin, sVCAM-1, ICAM-1, VEGF-α and vWF. Arterial rings of the left anterior descending coronary artery and mesenteric resistance arteries were mounted in microvascular myographs, and concentration-response curves were constructed.

RESULTS

The plasma levels of the endothelial markers, sP-selectin and vWF increased following cardiac arrest at both 30 min and 2 h. Acetylcholine-induced endothelium-dependent and mainly nitric oxide (NO)-mediated vasodilatation was impaired in the coronary arteries at 30 min, but not 2 h after resuscitation. Endothelium-derived hyperpolarisation (EDH)-type vasodilatation induced by NS309 and vasodilatation induced by the NO donor sodium nitroprusside was unaltered. In parallel with systemic hypotension, mesenteric arteries exhibited a larger response to NS309 2 h after resuscitation.

CONCLUSION

The present results show marked endothelial alterations after cardiac arrest and resuscitation reflected by increased endothelial plasma markers, impaired NO-mediated coronary vasodilatation in the early post-resuscitation phase and enhanced EDH-type vasodilatation in mesenteric arteries later in the post-resuscitation phase.

Seventy-two hours of mild hypothermia after cardiac arrest is associated with a lowered inflammatory response during rewarming in a prospective observational study

INTRODUCTION

Whole-body ischemia and reperfusion trigger a systemic inflammatory response. In this study, we analyzed the effect of temperature on the inflammatory response in patients treated with prolonged mild hypothermia after cardiac arrest.

METHODS

Ten comatose patients with return of spontaneous circulation after pulseless electrical activity/asystole or prolonged ventricular fibrillation were treated with mild therapeutic hypothermia for 72 hours after admission to a tertiary care university hospital. At admission and at 12, 24, 36, 48, 72, 96 and 114 hours, the patients' temperature was measured and blood samples were taken from the arterial catheter. Proinflammatory interleukin 6 (IL-6) and anti-inflammatory (IL-10) cytokines and chemokines (IL-8 and monocyte chemotactic protein 1), intercellular adhesion molecule 1 and complement activation products (C1r-C1s-C1inhibitor, C4bc, C3bPBb, C3bc and terminal complement complex) were measured. Changes over time were analyzed with the repeated measures test for nonparametric data. Dunn's multiple comparisons test was used for comparison of individual time points.

RESULTS

The median temperature at the start of the study was 34.3°C (33.4°C to 35.2°C) and was maintained between 32°C and 34°C for 72 hours. All patients were passively rewarmed after 72 hours, from (median (IQR)) 33.7°C (33.1°C to 33.9°C) at 72 hours to 38.0°C (37.5°C to 38.1°C) at 114 hours (P <0.001). In general, the cytokines and chemokines remained stable during hypothermia and decreased during rewarming, whereas complement activation was suppressed during the whole hypothermia period and increased modestly during rewarming.

CONCLUSIONS

Prolonged hypothermia may blunt the inflammatory response after rewarming in patients after cardiac arrest. Complement activation was low during the whole hypothermia period, indicating that complement activation is also highly temperature-sensitive in vivo. Because inflammation is a strong mediator of secondary brain injury, a blunted proinflammatory response after rewarming may be beneficial.

Effects of Chinese medicine shen-fu injection on the expression of inflammatory cytokines and complements during post-resuscitation immune dysfunction in a porcine model

OBJECTIVE

To investigate the action of Shen-Fu Injection (SFI) in regulating the expression of the serum complements and inflammatory cytokines synthesized and released in response to the stress of global ischemia accompanying cardiac arrest (CA) and resuscitation.

METHODS

Thirty pigs were randomly divided into the sham (n=6) and 3 returns of spontaneous circulation (ROSC) groups (n=24). After 8-min untreated ventricular fibrillation and 2-min basic life support, 24 pigs of the ROSC groups were randomized into three groups (n=8 per group), which received central venous injection of SFI (SFI group), epinephrine (EP group), or saline (SA group). Hemodynamic status and blood samples were obtained at 0, 0.5, 1, 2, 4, 6, 12, and 24 h after ROSC.

RESULTS

Serum concentrations of specific activation markers of the complement system C3, C4 and C5b-9 were increased during cardiopulmonary resuscitation through 24 h after ROSC. There were intense changes of various pro-inflammatory cytokines and anti-inflammatory cytokines as early as 0.5 h after CA. Compared with the EP and SA groups, SFI treatment reduced the proinflammatory cytokines levels of interleukin (IL)-6, IL-8 and tumor necrosis factor α (TNF-α, P<0.05), and increased the anti-inflammatory cytokine levels of IL-4 and IL-10 (P<0.05). Further, SFI treatment decreased the values of C3, C4 and C5b-9 compared with the EP and SA groups.

CONCLUSIONS

SFI, derived from the ancient Chinese medicine, has significant effects in attenuating post-resuscitation immune dysfunction by modulating the expression of complements and cytokines levels. The current study provided an experimental basis for the clinical application of a potential pharmacologic target for post resuscitation immune dysfunction.

Complement activation and its prognostic role in post-cardiac arrest patients

Cardiac arrest causes generalized ischaemia/hypoxia, and subsequent resuscitation inflicts reperfusion injury, the pathology of which is not fully understood. Moreover, predicting the prognosis of comatose, post-cardiac arrest patients is a complex clinical challenge. We hypothesized that the extent of complement activation might be a reliable predictor of mortality in this population. Forty-six comatose cardiac arrest patients were enrolled into our prospective cohort study, conducted in a tertiary care university clinic. All subjects were cooled to 32-34 °C body temperature for 24 h and then allowed to rewarm to normothermia. All patients underwent diagnostic coronary angiography. On admission, at 6 and 24 h, blood samples were taken from the arterial catheter. In these, complement products (C3a, C3, C4d, C4, SC5b9 and Bb) were measured by ELISA in blood samples. Patients were followed up for 30 days; 22 patients (47.8%) died by the end of this period. We observed that complement activation (determined as the C3a to C3 ratio) was higher in non-survivors than in survivors at each time point. In the multivariate Cox regression analysis, the C3a/C3 ratio determined 24 h after the initiation of therapeutic hypothermia predicted 30-day mortality regardless of age, sex and the APACHE II score. Complement activation occurs in post-cardiac arrest patients, and its extent correlates with 30-day survival. The C3a/C3 ratio might prove useful for estimating the prognosis of comatose post-cardiac arrest patients.

Impact of Toll-like receptor 2 deficiency on survival and neurological function after cardiac arrest: a murine model of cardiopulmonary resuscitation

BACKGROUND

Cardiac arrest (CA) followed by cardiopulmonary resuscitation (CPR) is associated with poor survival rate and neurofunctional outcome. Toll-like receptor 2 (TLR2) plays an important role in conditions of sterile inflammation such as reperfusion injury. Recent data demonstrated beneficial effects of the administration of TLR2-blocking antibodies in ischemia/reperfusion injury. In this study we investigated the role of TLR2 for survival and neurofunctional outcome after CA/CPR in mice.

METHODS

Female TLR2-deficient (TLR2(-/-)) and wild type (WT) mice were subjected to CA for eight min induced by intravenous injection of potassium chloride and CPR by external chest compression. Upon the beginning of CPR, n = 15 WT mice received 5 µg/g T2.5 TLR2 inhibiting antibody intravenously while n = 30 TLR2(-/-) and n = 31 WT controls were subjected to injection of normal saline. Survival and neurological outcome were evaluated during a 28-day follow up period. Basic neurological function, balance, coordination and overall motor function as well as spatial learning and memory were investigated, respectively. In a separate set of experiments, six mice per group were analysed for cytokine and corticosterone serum levels eight hours after CA/CPR.

RESULTS

TLR2 deficiency and treatment with a TLR2 blocking antibody were associated with increased survival (77% and 80% vs. 51% of WT control; both P < 0.05). Neurofunctional performance was less compromised in TLR2(-/-) and antibody treated mice. Compared to WT and antibody treated mice, TLR2(-/-) mice exhibited reduced IL-6 (both P < 0.05) but not IL-1β levels and increased corticosterone plasma concentrations (both P < 0.05).

CONCLUSION

Deficiency or functional blockade of TLR2 is associated with increased survival and improved neurofunctional outcome in a mouse model of CA/CPR. Thus, TLR2 inhibition could provide a novel therapeutic approach for reducing mortality and morbidity after cardiac arrest and cardiopulmonary resuscitation.

Effect of mild hypothermia on the coagulation-fibrinolysis system and physiological anticoagulants after cardiopulmonary resuscitation in a porcine model

The aim of this study was to evaluate the effect of mild hypothermia on the coagulation-fibrinolysis system and physiological anticoagulants after cardiopulmonary resuscitation (CPR). A total of 20 male Wuzhishan miniature pigs underwent 8 min of untreated ventricular fibrillation and CPR. Of these, 16 were successfully resuscitated and were randomized into the mild hypothermia group (MH, n = 8) or the control normothermia group (CN, n = 8). Mild hypothermia (33°C) was induced intravascularly, and this temperature was maintained for 12 h before pigs were actively rewarmed. The CN group received normothermic post-cardiac arrest (CA) care for 72 h. Four animals were in the sham operation group (SO). Blood samples were taken at baseline, and 0.5, 6, 12, 24, and 72 h after ROSC. Whole-body mild hypothermia impaired blood coagulation during cooling, but attenuated blood coagulation impairment at 72 h after ROSC. Mild hypothermia also increased serum levels of physiological anticoagulants, such as PRO C and AT-III during cooling and after rewarming, decreased EPCR and TFPI levels during cooling but not after rewarming, and inhibited fibrinolysis and platelet activation during cooling and after rewarming. Finally, mild hypothermia did not affect coagulation-fibrinolysis, physiological anticoagulants, or platelet activation during rewarming. Thus, our findings indicate that mild hypothermia exerted an anticoagulant effect during cooling, which may have inhibitory effects on microthrombus formation. Furthermore, mild hypothermia inhibited fibrinolysis and platelet activation during cooling and attenuated blood coagulation impairment after rewarming. Slow rewarming had no obvious adverse effects on blood coagulation.

[Post-resuscitation syndrome. Role of inflammation after cardiac arrest]

Cardiac arrest with subsequent cardiopulmonary resuscitation causes an ischemic reperfusion syndrome of the whole body resulting in localized damage of particularly sensitive organs, such as the brain and heart, together with systemic sequelae. The main factor is a generalized activation of inflammatory reactions resulting in symptoms similar in many aspects to those of sepsis. Systemic inflammation strengthens organ damage due to disorders in the macrocirculation and microcirculation due to metabolic imbalance as well as the effects of direct leukocyte transmitted tissue destruction. The current article gives an overview on the role of inflammation following cardiac arrest and presents in detail the underlying mechanisms, the clinical symptoms and possible therapeutic approaches.

Persistent peripheral and microcirculatory perfusion alterations after out-of-hospital cardiac arrest are associated with poor survival

OBJECTIVE

To evaluate sublingual microcirculatory and peripheral tissue perfusion parameters in relation to systemic hemodynamics during and after therapeutic hypothermia following out-of-hospital cardiac arrest.

DESIGN

Prospective observational study.

SETTING

Intensive cardiac care unit at a university teaching hospital.

SUBJECTS

We followed 80 patients, of whom 25 were included after out-of-hospital cardiac arrest.

INTERVENTION

In all patients, we induced therapeutic hypothermia to 33°C during the first 24 hrs of admission.

MEASUREMENTS AND MAIN RESULTS

Complete hemodynamic measurements were obtained directly on intensive cardiac care unit admission (baseline), during induced hypothermia (T1), directly after rewarming (T2), and another 24 hrs later (T3). In addition, the sublingual microcirculation was observed using sidestream dark-field imaging, and peripheral tissue perfusion was monitored with the peripheral perfusion index, capillary refill time, tissue oxygen saturation, and forearm-to-fingertip skin temperature gradient. During hypothermia, all sublingual microcirculatory parameters decreased significantly together with peripheral capillary refill time and the peripheral perfusion index, followed by a significant increase at T2. Changes in sublingual and peripheral tissue perfusion parameters were significantly related to changes in central body temperature, but not to changes in systemic hemodynamic variables such as cardiac index or mean arterial pressure. Surprisingly, these parameters were significantly lower in nonsurvivors (n=6) at admission and after rewarming. Persistent alterations in these parameters were related with the prevalence of organ dysfunction and were highly predictive of mortality.

CONCLUSIONS

Following out-of-hospital cardiac arrest, the early postresuscitation phase is characterized by abnormalities in sublingual microcirculation and peripheral tissue perfusion, which are caused by vasoconstriction due to induced systemic hypothermia and not by impaired systemic blood flow. Persistence of these alterations is associated with organ failure and death, independent of systemic hemodynamics.

C5a-mediated neutrophil dysfunction is RhoA-dependent and predicts infection in critically ill patients

Critically ill patients are at heightened risk for nosocomial infections. The anaphylatoxin C5a impairs phagocytosis by neutrophils. However, the mechanisms by which this occurs and the relevance for acquisition of nosocomial infection remain undetermined. We aimed to characterize mechanisms by which C5a inhibits phagocytosis in vitro and in critically ill patients, and to define the relationship between C5a-mediated dysfunction and acquisition of nosocomial infection. In healthy human neutrophils, C5a significantly inhibited RhoA activation, preventing actin polymerization and phagocytosis. RhoA inhibition was mediated by PI3Kδ. The effects on RhoA, actin, and phagocytosis were fully reversed by GM-CSF. Parallel observations were made in neutrophils from critically ill patients, that is, impaired phagocytosis was associated with inhibition of RhoA and actin polymerization, and reversed by GM-CSF. Among a cohort of 60 critically ill patients, C5a-mediated neutrophil dysfunction (as determined by reduced CD88 expression) was a strong predictor for subsequent acquisition of nosocomial infection (relative risk, 5.8; 95% confidence interval, 1.5-22; P = .0007), and remained independent of time effects as assessed by survival analysis (hazard ratio, 5.0; 95% confidence interval, 1.3-8.3; P = .01). In conclusion, this study provides new insight into the mechanisms underlying immunocompromise in critical illness and suggests novel avenues for therapy and prevention of nosocomial infection.

Disseminated intravascular coagulation or extended intravascular coagulation in massive pulmonary embolism

See also Leitner JM, Jilma B, Spiel AO, Sterz F, Laggner AN, Janata KM. Massive pulmonary embolism leading to cardiac arrest is associated with consumptive coagulopathy presenting as disseminated intravascular coagulation. This issue, pp 1477–82; Thachil J. DIC score predicts mortality in massive clot coagulopathy as a result of extensive pulmonary embolism: a rebuttal. This issue, pp 1657–8; Leitner JM, Janata-Schwatzek K, Spiel AO, Sterz F, Laggner AN, Jilma B. DIC score predicts mortality in massive clot coagulopathy as a result of extensive pulmonary embolism: reply to a rebuttal. This issue, pp 1658–9.

A comparison between head cooling begun during cardiopulmonary resuscitation and surface cooling after resuscitation in a pig model of cardiac arrest

OBJECTIVE

Employing transnasal head-cooling in a pig model of prolonged ventricular fibrillation, we compared the effects of 4 hrs of head-cooling started during cardiopulmonary resuscitation with those of 8 hrs of surface-cooling started at 2 hrs after resuscitation on 96-hr survival and neurologic outcomes.

DESIGN

Prospective controlled animal study.

SETTING

University-affiliated research laboratory.

SUBJECTS

Domestic pigs.

INTERVENTIONS

Twenty-four male pigs were subjected to 10 min of untreated ventricular fibrillation followed by 5 min of cardiopulmonary resuscitation. In the head-cooling group, hypothermia was started with cardiopulmonary resuscitation and continued for 4 hrs after resuscitation. In the surface-cooling group, systemic hypothermia with a cooling blanket was started, in accord with current clinical practices, at 2 hrs after resuscitation and continued for 8 hrs. Methods in the control animal studies were identical except for temperature interventions.

MEASUREMENTS AND MAIN RESULTS

All animals were resuscitated except for one animal in each of the surface-cooling and control groups. After 5 min of cardiopulmonary resuscitation, jugular vein temperature was significantly decreased in the head-cooled animals. However, there were no differences in pulmonary artery temperatures among the three groups at that time. Nevertheless, both head-cooled and surface-cooled animals had an improved 96-hr survival after resuscitation. Significantly better neurologic outcomes were observed in early head-cooled animals in the first 3 days after resuscitation.

CONCLUSION

Early head-cooling during cardiopulmonary resuscitation continuing for 4 hrs after resuscitation produced favorable survival and neurologic outcomes in comparison with delayed surface-cooling of 8 hrs duration.

Severe endothelial injury and subsequent repair in patients after successful cardiopulmonary resuscitation

INTRODUCTION

Ischemia and reperfusion after cardiopulmonary resuscitation (CPR) induce endothelial activation and systemic inflammatory response, resulting in post-resuscitation disease. In this study we analyzed direct markers of endothelial injury, circulating endothelial cells (CECs) and endothelial microparticles (EMPs), and endothelial progenitor cells (EPCs) as a marker of endothelial repair in patients after CPR.

METHODS

First we investigated endothelial injury in 40 patients after CPR, 30 controls with stable coronary artery disease (CAD), and 9 healthy subjects, who were included to measure CECs and EMPs. In a subsequent study, endothelial repair was assessed by EPC measurement in 15 CPR, 9 CAD, and 5 healthy subjects. Blood samples were drawn immediately and 24 hours after ROSC and analyzed by flow cytometry. For all statistical analyses P < 0.05 was considered significant.

RESULTS

There was a massive rise in CEC count in resuscitated patients compared to CAD (4,494.1 +/- 1,246 versus 312.7 +/- 41 cells/mL; P < 0.001) and healthy patients (47.5 +/- 3.7 cells/mL; P < 0.0005). Patients after prolonged CPR (>or=30 min) showed elevated CECs compared to those resuscitated for <30 min (6,216.6 +/- 2,057 versus 2,340.9 +/- 703.5 cells/mL; P = 0.13/ns). There was a significant positive correlation of CEC count with duration of CPR (R2= 0.84; P < 0.01). EMPs were higher immediately after CPR compared to controls (31.2 +/- 5.8 versus 19.7 +/- 2.4 events/microL; P = 0.12 (CAD); versus 15.0 +/- 5.2 events/microL; P = 0.07 (healthy)) but did not reach significance until 24 hours after CPR (69.1 +/- 12.4 versus 22.0 +/- 3.0 events/microL; P < 0.005 (CAD); versus 15.4 +/- 4.4 events/microL; P < 0.001 (healthy)). EPCs were significantly elevated in patients on the second day after CPR compared to CAD (1.16 +/- 0.41 versus 0.02 +/- 0.01% of lymphocytes; P < 0.005) and healthy (0.04 +/- 0.01; P < 0.005).

CONCLUSIONS

In the present study we provide evidence for a severe endothelial damage after successful CPR. Our results point to an ongoing process of endothelial injury, paralleled by a subsequent endothelial regeneration 24 hours after resuscitation.

Complement inhibition as a proposed neuroprotective strategy following cardiac arrest

Out-of-hospital cardiac arrest (OHCA) is a devastating disease process with neurological injury accounting for a disproportionate amount of the morbidity and mortality following return of spontaneous circulation. A dearth of effective treatment strategies exists for global cerebral ischemia-reperfusion (GCI/R) injury following successful resuscitation from OHCA. Emerging preclinical as well as recent human clinical evidence suggests that activation of the complement cascade plays a critical role in the pathogenesis of GCI/R injury following OHCA. In addition, it is well established that complement inhibition improves outcome in both global and focal models of brain ischemia. Due to the profound impact of GCI/R injury following OHCA, and the relative lack of effective neuroprotective strategies for this pathologic process, complement inhibition provides an exciting opportunity to augment existing treatments to improve patient outcomes. To this end, this paper will explore the pathophysiology of complement-mediated GCI/R injury following OHCA.

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".

Sivelestat treatment for acute respiratory distress syndrome in an infant

Resuscitation and acute cerebral damage after cardiopulmonary arrest often induce a systemic inflammatory response and subsequently cause multiple organ failure, including acute lung injury (ALI). Sivelestat has been reported to be effective for ALI associated with systemic inflammatory response syndrome (SIRS), but the effectiveness and safety of the drug for infants has not been confirmed. We report a 33-day-old infant who developed acute respiratory distress syndrome (ARDS) following hypoxic encephalopathy immediately after successful resuscitation from cardiopulmonary arrest. Sivelestat was administered continuously for 7 days with no adverse reactions, and consolidations on a chest radiograph were diminished and impaired oxygenation was markedly alleviated. Our experience suggests that intravenous sivelestat offers a new therapeutic strategy for infantile ARDS/ALI, but further investigation of the indication, administration period, and dosage is required.

Pronounced platelet hyperfunction in patients with cardiac arrest achieving restoration of spontaneous circulation

OBJECTIVE

Markers of platelet activation are increased in patients undergoing cardiopulmonary resuscitation. Hyperfunctional platelets may contribute to impairment of microcirculatory function and overall poor outcome despite restoration of spontaneous circulation (ROSC). Patients with myocardial infarction have hyperfunctional platelets, which predict the degree of myocardial necrosis. Thus, we hypothesized that platelets may be even more activated in patients whose myocardial infarction leads to cardiac arrest and compared them with patients whose cardiac arrest was due to a noncardiac origin.

DESIGN

Prospective observational study.

SETTING

Emergency department of a tertiary care hospital.

PATIENTS

One hundred four patients with witnessed cardiac arrest who achieved ROSC.

INTERVENTIONS

Blood sampling.

MEASUREMENTS AND MAIN RESULTS

We assessed collagen adenosine diphosphate closure time with the platelet function analyzer-100, and measured plasma levels of von Willebrand factor: ristocetin cofactor activity levels by turbidometry. Independent physicians diagnosed the origin of cardiac arrest. The majority of cardiac arrests were caused by myocardial ischemia. Invariably, collagen adenosine diphosphate closure time values (55 seconds; 95% confidence interval: 52-58 seconds) were much shorter in these patients compared with patients with other causes of cardiac arrest (110 seconds; 95% confidence interval: 84-135 seconds, p < 0.001). von Willebrand factor: ristocetin cofactor activity plasma levels were more than three-fold above normal values in both groups.

CONCLUSIONS

Patients with myocardial ischemia-triggered cardiac arrest had the highest degree of platelet hyperfunction under high shear rates, which was not solely due to increased von Willebrand factor. Future trials are necessary to clarify whether rapid, more aggressive antiplatelet therapy improves outcome after cardiac arrest.

Thrombolysis during resuscitation for out-of-hospital cardiac arrest

BACKGROUND

Approximately 70% of persons who have an out-of-hospital cardiac arrest have underlying acute myocardial infarction or pulmonary embolism. Therefore, thrombolysis during cardiopulmonary resuscitation may improve survival.

METHODS

In a double-blind, multicenter trial, we randomly assigned adult patients with witnessed out-of-hospital cardiac arrest to receive tenecteplase or placebo during cardiopulmonary resuscitation. Adjunctive heparin or aspirin was not used. The primary end point was 30-day survival; the secondary end points were hospital admission, return of spontaneous circulation, 24-hour survival, survival to hospital discharge, and neurologic outcome.

RESULTS

After blinded review of data from the first 443 patients, the data and safety monitoring board recommended discontinuation of enrollment of asystolic patients because of low survival, and the protocol was amended. Subsequently, the trial was terminated prematurely for futility after enrolling a total of 1050 patients. Tenecteplase was administered to 525 patients and placebo to 525 patients; the two treatment groups had similar clinical profiles. We did not detect any significant differences between tenecteplase and placebo in the primary end point of 30-day survival (14.7% vs. 17.0%; P=0.36; relative risk, 0.87; 95% confidence interval, 0.65 to 1.15) or in the secondary end points of hospital admission (53.5% vs. 55.0%, P=0.67), return of spontaneous circulation (55.0% vs. 54.6%, P=0.96), 24-hour survival (30.6% vs. 33.3%, P=0.39), survival to hospital discharge (15.1% vs. 17.5%, P=0.33), or neurologic outcome (P=0.69). There were more intracranial hemorrhages in the tenecteplase group.

CONCLUSIONS

When tenecteplase was used without adjunctive antithrombotic therapy during advanced life support for out-of-hospital cardiac arrest, we did not detect an improvement in outcome, in comparison with placebo. (ClinicalTrials.gov number, NCT00157261.)

Akt activates NOS3 and separately restores barrier integrity in H2O2-stressed human cardiac microvascular endothelium

The integrity of microvascular endothelium is an important regulator of myocardial contractility. Microvascular barrier integrity could be altered by increased reactive oxygen species (ROS) stress seen within minutes after cardiac arrest resuscitation. Akt and its downstream target nitric oxide (NO) synthase (NOS)3 can protect barrier integrity during ROS stress, but little work has studied these oxidant stress responses in human cardiac microvascular endothelial cells (HCMVEC). We, therefore, studied how ROS affects barrier function and NO generation via Akt and its downstream target NOS3 in HCMVEC. HCMVEC exposed to 500 microM H2O2 had increased Akt phosphorylation within 10 min at both Ser-473 and Thr-308 sites, an effect blocked by the phosphatidylinositol 3-kinase inhibitor LY-294002. H2O2 also induced NO generation that was associated with NOS3 Ser-1177 site phosphorylation and Thr-495 dephosphorylation, with Ser-1177 effects attenuated by LY-294002 and an Akt inhibitor, Akt/PKB signaling inhibitor-2 (API-2). H2O2 induced significant barrier disruption in HCMVEC within minutes, but recovery started within 30 min and normalized over hours. The NOS inhibitor Nomega-nitro-L-arginine methyl ester (200 microM) blocked NO generation but had no effect on H2O2-induced barrier permeability or the recovery of barrier integrity. By contrast, the Akt inhibitor API-2 abrogated HCMVEC barrier restoration. These results suggest that oxidant stress in HCMVEC activates NOS3 via Akt. NOS3/NO are not involved in the regulation of H2O2-affected barrier function in HCMVEC. Independent of NOS3 regulation, Akt proves to be critical for the restoration of barrier integrity in HCMVEC.

Neurological outcome and inflammation after cardiac arrest--effects of protein C in rats

BACKGROUND

The response of the human body to cardiac arrest (CA) and cardiopulmonary resuscitation is characterised by excessive coagulation, inadequate endogenous anti-coagulation and fibrinolysis as well as an inflammatory syndrome that closely resembles the immunological profile observed in patients with sepsis. Recombinant human activated protein C (rhAPC) has been found to be protective in severe sepsis and in animal models of stroke and spinal cord injury. In the present study, we evaluated the effects of rhAPC on neurological outcome after CA in rats.

METHODS

After 6 min of CA and subsequent cardiopulmonary resuscitation, male Wistar rats were randomized into 3 treatment groups: high dose rhAPC (2 mg/kg bolus and 0.1 mg/(kg h) for 6 h), low dose rhAPC (0.5 mg/kg and 0.025 mg/(kg h) for 6 h), and placebo (n=12 per treatment and reperfusion time). Neurological outcome was determined using a tape removal test and a composite neurological deficit score (NDS). As secondary measurements, we evaluated overall and neuronal survival, hippocampal caspase activity and inflammatory markers.

RESULTS

No difference between groups was found with the NDS. The tape removal test showed only a transitory improvement in the low dose group at 3 d after CA (P=0.041). No significant differences were observed for secondary measurements.

CONCLUSION

A clear and lasting effect of rhAPC on neurological outcome or inflammation after CA could not be shown in this study but the detailed analysis of the postresuscitation syndrome given here builds a firm basis for further research.

Insufficient production of urinary trypsin inhibitor for neutrophil elastase release after cardiac arrest

To investigate the relationship between the inflammatory responses and postresuscitation syndrome, we prospectively examined the serial changes of neutrophil elastase (NE), urinary trypsin inhibitor (UTI), and TNF-alpha) in successfully resuscitated patients after out-of-hospital cardiac arrest. This study included 36 patients with out-of-hospital cardiac arrests who were admitted to our intensive care unit after return of spontaneous circulation (ROSC). The 11 patients who restored to spontaneous circulation within 30 min after cardiac arrest were defined as the short cardiac arrest group. The 25 patients who restored to spontaneous circulation more than 30 min after cardiac arrest were defined as the long cardiac arrest group. Eight healthy volunteers served as control group. Daily plasma levels of NE, UTI, and TNF-alpha were measured from days 1 to 5 after ROSC. The releases of NE from activated neutrophil just after ROSC in the patients with long cardiac arrest were statistically higher than those of the short cardiac arrest group. There was a significant correlation between the NE levels and the duration of cardiac arrest. A high but insufficient production of UTI for NE release was observed on day 1, especially in the patients with a long duration of cardiac arrest. The cerebral performance category of the short cardiac arrest group was better than that of the long cardiac arrest group. Although high levels of TNF-alpha were sustained in the postresuscitation period, the levels of TNF-alpha were unrelated to the duration of cardiac arrest. In conclusion, a massive release of NE in proportion to the duration of cardiac arrest and an insufficient production of UTI for the NE release may contribute to the pathogenesis of postresuscitation syndrome after out-of-hospital cardiac arrest.

The effect of intracerebroventricular application of the caspase-3 inhibitor zDEVD-FMK on neurological outcome and neuronal cell death after global cerebral ischaemia due to cardiac arrest in rats

BACKGROUND

Global cerebral ischaemia after cardiac arrest (CA) leads to programmed cell death (PCD) with characteristic signs of apoptosis in selectively vulnerable areas of the brain. The activation of caspase-3, an executioner caspase, plays a key role in the apoptotic cascade. We, therefore, studied the effects of the application of the specific caspase-3 inhibitor zDEVD-FMK on neurological outcome and neuronal cell death after experimental CA in rats.

METHODS

A 6-min CA was induced in anaesthetised and mechanically ventilated male Wistar rats. After cardiopulmonary resuscitation (CPR) and restoration of spontaneous circulation (ROSC) the animals were randomised to two groups to receive a continuous intracerebroventricular (i.c.v.) infusion for 7 days of zDEVD-FMK or placebo (artificial cerebrospinal fluid, CSF). At 24h, 3 and 7 days after ROSC, animals were tested according to a neurological deficit score (NDS). Seven days after ROSC, coronal sections of the brain were taken at the dorsal hippocampal level and analysed with cresyl-violet staining, the TUNEL technique and a caspase activity assay. Viable and TUNEL-positive neurons were counted in the hippocampal CA-1 sector.

RESULTS

The NDS demonstrated severe deficits 1 and 3 days after ROSC, which resolved by 7 days with no difference between the two groups. At 7 days after ROSC neuronal death could be detected using cresyl-violet and TUNEL staining with no difference between the groups.

CONCLUSION

We conclude that zDEVD-FMK administration has no effect on neurological outcome and PCD after global cerebral ischaemia following CA in rats. Other mechanisms or pathways must be identified in the pathophysiology of PCD after CA.