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

Delayed CCL23 response is associated with poor outcomes after cardiac arrest

Chemokines, a family of chemotactic cytokines, mediate leukocyte migration to and entrance into inflamed tissue, contributing to the intensity of local inflammation. We performed an analysis of chemokine and immune cell responses to cardiac arrest (CA). Forty-two patients resuscitated from cardiac arrest were analyzed, and twenty-two patients who underwent coronary artery bypass grafting (CABG) surgery were enrolled. Quantitative antibody array, chemokines, and endotoxin quantification were performed using the patients blood. Analysis of CCL23 production in neutrophils obtained from CA patients and injected into immunodeficient mice after CA and cardiopulmonary resuscitation (CPR) were done using flow cytometry. The levels of CCL2, CCL4, and CCL23 are increased in CA patients. Temporal dynamics were different for each chemokine, with early increases in CCL2 and CCL4, followed by a delayed elevation in CCL23 at forty-eight hours after CA. A high level of CCL23 was associated with an increased number of neutrophils, neuron-specific enolase (NSE), worse cerebral performance category (CPC) score, and higher mortality. To investigate the role of neutrophil activation locally in injured brain tissue, we used a mouse model of CA/CPR. CCL23 production was increased in human neutrophils that infiltrated mouse brains compared to those in the peripheral circulation. It is known that an early intense inflammatory response (within hours) is associated with poor outcomes after CA. Our data indicate that late activation of neutrophils in brain tissue may also promote ongoing injury via the production of CCL23 and impair recovery after cardiac arrest.

Protocol for immunophenotyping out-of-hospital cardiac arrest patients

Immunophenotyping of out-of-hospital cardiac arrest (OHCA) patients is of increasing interest but has challenges. Here, we describe steps for the design of the clinical cohort, planning patient enrollment and sample collection, and ethical review of the study protocol. We detail procedures for blood sample collection and cryopreservation of peripheral blood mononuclear cells (PBMCs). We detail steps to modulate immune checkpoints in OHCA PBMC ex vivo. This protocol also has relevance for immunophenotyping other types of critical illness. For complete details on the use and execution of this protocol, please refer to Tamura et al. (2023).1.

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.

Effectiveness of Induced Hypothermia on the Prognosis of Post-cardiac Arrest Patients: A Scoping Literature Review

Cardiac arrest (CA) is one of the leading causes of death worldwide. Therapeutic hypothermia (TH) is hypothesized to be a reliable practice for better prognosis in post-cardiac arrest (PCA) patients. Medical subject headings (MeSH) terminology was used to search PubMed Central, Medline, and PubMed databases for articles on the use of hypothermia in PCA patients. We selected various clinical trials, meta-analyses and review articles with complete texts in the English language. PCA syndrome occurs after a CA where the body experiences a state of global ischemia and multi-system dysfunction due to the release of reactive oxygen species (ROS) and inflammatory mediators. Hypothermia slows down enzymatic reactions, reduces free radical production, conserves energy, and prevents the accumulation of metabolic waste products. Delaying the time to initiate targeted temperature management (TTM) increases the mortality of patients, the appropriate temperature for TTM has always been debatable. TTM also has various deleterious effects on various organ systems from shivering, and arrhythmias to life-threatening infections but the risks outweigh the benefits for the patients when hypothermia is introduced in PCA care. Our study compares the different modalities to initiate hypothermia from surface cooling devices to intravascular cooling devices, and the adverse effects of each method compared to another.

Escherichia coli-induced inflammatory responses are temperature-dependent in human whole blood ex vivo

Systemic inflammatory conditions are often associated with hypothermia or hyperthermia. Therapeutic hypothermia is used in post-cardiac arrest and some other acute diseases. There is a need for more knowledge concerning the effect of various temperatures on the acute inflammatory response. The complement system plays a crucial role in initiating the inflammatory response. We hypothesized that temperatures above and below the physiologic 37 °C affect complement activation and cytokine production ex vivo. Lepirudin-anticoagulated human whole blood from 10 healthy donors was incubated in the presence or absence of Escherichia coli at different temperatures (4 °C, 12 °C, 20 °C, 33 °C, 37 °C, 39 °C, and 41 °C). Complement activation was assessed by the terminal C5b-9 complement complex (TCC) and the alternative convertase C3bBbP using ELISA. Cytokines were measured using a 27-plex assay. Granulocyte and monocyte activation was evaluated by CD11b surface expression using flow cytometry. A consistent increase in complement activation was observed with rising temperature, reaching a maximum at 41 °C, both in the absence (C3bBbP p < 0.05) and presence (C3bBbP p < 0.05 and TCC p < 0.05) of E. coli. Temperature alone did not affect cytokine production, whereas incubation with E. coli significantly increased cytokine levels of IL-1β, IL-2, IL-6, IL-8, IFN-γ, and TNF at temperatures > 20 °C. Maximum increase occurred at 39 °C. However, a consistent decrease was observed at 41 °C, significant for IL-1β (p = 0.003). Granulocyte CD11b displayed the same temperature-dependent pattern as cytokines, with a corresponding increase in endothelial cell apoptosis and necrosis. Thus, blood temperature differentially determines the degree of complement activation and cytokine release.

ATP-induced hypothermia improves burn injury and relieves burn pain in mice

Thermal burn injury is a severe and life-threatening form of trauma that presents a significant challenge to clinical therapy. Therapeutic hypothermia has been shown to be beneficial in various human pathologies. Adenosine triphosphate (ATP) induces a hypothermic state that resembles hibernation-like suspended animation in mammals. This study investigates the potential protective role of ATP-induced hypothermia in thermal burn injury. Male C57BL/6 mice underwent a sham procedure or third-degree burn, and ATP-induced hypothermia was applied immediately or 1 h after burn injury. Our results show that ATP-induced hypothermia significantly improved burn depth progression and reduced collagen degradation. Moreover, hypothermia induced by ATP alleviated burn-induced hyperinflammatory responses and oxidative stress. Metabolomic profiling revealed that ATP-induced hypothermia reversed the shifts of metabolic profiles of the skin in burn mice. In addition, ATP-induced hypothermia relieved nociceptive and inflammatory pain, as observed in the antinociceptive test. Our findings suggest that ATP-induced hypothermia attenuates burn injury and provides new insights into first-aid therapy after thermal burn injury.

Association Between Procalcitonin Level at 72 Hours After Cardiac Arrest and Neurological Outcomes in Cardiac Arrest Survivors

The association between procalcitonin (PCT) level measured 72 hours after cardiac arrest (CA) and neurological outcomes is unknown. We aimed to examine the association of serial PCT levels up to 72 hours with neurological outcomes in patients who underwent targeted temperature management (TTM) after CA. This retrospective observational study included adult comatose patients with CA undergoing TTM (33℃ for 24 hours) at the Chonnam National University Hospital in Gwangju, Korea, between January 2018 and December 2020. PCT levels were measured at admission and at 24, 48, and 72 hours after CA. The presence of early-onset infections (within 7 days after CA) was confirmed by reviewing clinical, radiological, and microbiological data. The primary outcome was poor neurological outcomes at 6 months and was defined by cerebral performance category 3-5. Among the CA survivors, 118 were included and 67 (56.8%) had poor neurological outcomes. The PCT level at 72 hours in the poor outcome group (3.01 [0.88-12.71]) was higher than that in good outcome group (0.56 [0.18-1.32]). The multivariate analysis revealed that the PCT level at 72 hours (adjusted odds ratio 1.241; 95% confidence interval, 1.059-1.455) was independently associated with poor neurological outcomes, showed good performance for poor outcomes (area under the receiver operating characteristic curve of 0.823), and was not associated with early-onset infections. The PCT level at 72 hours after CA can be helpful in predicting prognosis, and it did not correlate with early-onset infections in the study.

Circulating Galectin-3 in Patients with Cardiogenic Shock Complicating Acute Myocardial Infarction Treated with Mild Hypothermia: A Biomarker Sub-Study of the SHOCK-COOL Trial

Background: Galectin-3 (Gal-3) is considered a potential cardiovascular inflammatory marker that may provide additional risk stratification for patients with acute heart failure. It is unknown whether mild therapeutic hypothermia (MTH) impacts Gal-3 levels. Therefore, this biomarker study aimed to investigate the effect of MTH on Gal-3. Methods: In the randomized SHOCK-COOL trial, 40 patients with cardiogenic shock (CS) complicating acute myocardial infraction (AMI) were randomly assigned to the MTH (33 °C) or control group in a 1:1 ratio. Blood samples were collected on the day of admission/day 1, day 2, and day 3. Gal-3 level kinetics throughout these time points were compared between the MTH and control groups. Additionally, potential correlations between Gal-3 and clinical patient characteristics were assessed. Multiple imputations were performed to account for missing data. Results: In the control group, Gal-3 levels were significantly lower on day 3 than on day 1 (day 1 vs. day 3: 3.84 [IQR 2.04−13.3] vs. 1.79 [IQR 1.23−3.50] ng/mL; p = 0.049). Gal-3 levels were not significantly different on any day between the MTH and control groups (p for interaction = 0.242). Spearman’s rank correlation test showed no significant correlation between Gal-3 levels and sex, age, smoking, body mass index (BMI), and levels of creatine kinase-MB, creatine kinase, C-reactive protein, creatinine, and white blood cell counts (all p > 0.05). Patients with lower Gal-3 levels on the first day after admission demonstrated a higher risk of all-cause mortality at 30 days (hazard ratio, 2.67; 95% CI, 1.11−6.42; p = 0.029). In addition, Gal-3 levels on day 1 had a good predictive value for 30-day all-cause mortality with an area under the receiver operating characteristic curve of 0.696 (95% CI: 0.513−0.879), with an optimal cut-off point of less than 3651 pg/mL. Conclusions: MTH has no effect on Gal-3 levels in patients with CS complicating AMI compared to the control group. In addition, Gal-3 is a relatively stable biomarker, independent of age, sex, and BMI, and Gal-3 levels at admission might predict the risk of 30-day all-cause mortality.

Mild Hypothermia Alleviates Complement C5a-Induced Neuronal Autophagy During Brain Ischemia-Reperfusion Injury After Cardiac Arrest

After restoration of spontaneous circulation (ROSC) following cardiac arrest, complements can be activated and excessive autophagy can contribute to the brain ischemia-reperfusion (I/R) injury. Mild hypothermia (HT) protects against brain I/R injury after ROSC, but the mechanisms have not been fully elucidated. Here, we found that HT significantly inhibited the increases in serum NSE, S100β, and C5a, as well as neurologic deficit scores, TUNEL-positive cells, and autophagic vacuoles in the pig brain cortex after ROSC. The C5a receptor 1 (C5aR1) mRNA and the C5a, C5aR1, Beclin 1, LC3-II, and cleaved caspase-3 proteins were significantly increased, but the P62 protein and the PI3K/Akt/mTOR pathway-related proteins were significantly reduced in pigs after ROSC or neuronal oxygen-glucose deprivation/reoxygenation. HT could significantly attenuate the above changes in NT-treated neurons. Furthermore, C5a treatment induced autophagy and apoptosis and reduced the PI3K/Akt/mTOR pathway-related proteins in cultured neurons, which could be reversed by C5aR1 antagonist PMX205. Our findings demonstrated that C5a could bind to C5aR1 to induce neuronal autophagy during the brain I/R injury, which was associated with the inhibited PI3K/Akt/mTOR pathway. HT could inhibit C5a-induced neuronal autophagy by regulating the C5a-C5aR1 interaction and the PI3K/Akt/mTOR pathway, which might be one of the neuroprotective mechanisms underlying I/R injury. The C5a receptor 1 (C5aR1) mRNA and the C5a, C5aR1, Beclin 1, LC3-II, and cleaved caspase-3 proteins were significantly increased, but the P62 protein and the PI3K/Akt/mTOR pathway-related proteins were significantly reduced in pigs after ROSC or neuronal oxygen-glucose deprivation/reoxygenation. Mild hypothermia (HT) could significantly attenuate the above changes in NT-treated neurons. Furthermore, C5a treatment induced autophagy and apoptosis and reduced the PI3K/Akt/mTOR pathway-related proteins in cultured neurons, which could be reversed by C5aR1 antagonist PMX205. Proposed mechanism by which HT protects against brain I/R injury by repressing C5a-C5aR1-induced excessive autophagy. Complement activation in response to brain I/R injury generates C5a that can interact with C5aR1 to inactivate mTOR, probably through the PI3K-AKT pathway, which can finally lead to autophagy activation. The excessively activated autophagy ultimately contributes to cell apoptosis and brain injury. HT may alleviate complement activation and then reduce C5a-induced autophagy to protect against brain I/R injury. HT, mild hypothermia; I/R, ischemia reperfusion.

Circulating Monocyte Chemoattractant Protein-1 in Patients with Cardiogenic Shock Complicating Acute Myocardial Infarction Treated with Mild Hypothermia: A Biomarker Substudy of SHOCK-COOL Trial

Background: There is evidence that monocyte chemoattractant protein-1 (MCP-1) levels reflect the intensity of the inflammatory response in patients with cardiogenic shock (CS) complicating acute myocardial infarction (AMI) and have a predictive value for clinical outcomes. However, little is known about the effect of mild therapeutic hypothermia (MTH) on the inflammatory response in patients with CS complicating AMI. Therefore, we conducted a biomarker study to investigate the effect of MTH on MCP-1 levels in patients with CS complicating AMI. Methods: In the randomized mild hypothermia in cardiogenic shock (SHOCK-COOL) trial, 40 patients with CS complicating AMI were enrolled and assigned to MTH (33 °C) for 24 h or normothermia at a 1:1 ratio. Blood samples were collected at predefined time points at the day of admission/day 1, day 2 and day 3. Differences in MCP-1 levels between and within the MTH and normothermia groups were assessed. Additionally, the association of MCP-1 levels with the risk of all-cause mortality at 30 days was analyzed. Missing data were accounted for by multiple imputation as sensitivity analyses. Results: There were differences in MCP-1 levels over time between patients in MTH and normothermia groups (P for interaction = 0.013). MCP-1 levels on day 3 were higher than on day 1 in the MTH group (day 1 vs day 3: 21.2 [interquartile range, 0.25–79.9] vs. 125.7 [interquartile range, 87.3–165.4] pg/mL; p = 0.006) and higher than in the normothermia group at day 3 (MTH 125.7 [interquartile range, 87.3–165.4] vs. normothermia 12.3 [interquartile range, 0–63.9] pg/mL; p = 0.011). Irrespective of therapy, patients with higher levels of MCP-1 at hospitalization tended to have a decreased risk of all-cause mortality at 30 days (HR, 2.61; 95% CI 0.997–6.83; p = 0.051). Conclusions: The cooling phase of MTH had no significant effect on MCP-1 levels in patients with CS complicating AMI compared to normothermic control, whereas MCP-1 levels significantly increased after rewarming. Trial registration: NCT01890317.

Complement Is Activated During Normothermic Machine Perfusion of Porcine and Human Discarded Kidneys

Background

The gap between demand and supply of kidneys for transplantation necessitates the use of kidneys from extended criteria donors. Transplantation of these donor kidneys is associated with inferior results, reflected by an increased risk of delayed graft function. Inferior results might be explained by the higher immunogenicity of extended criteria donor kidneys. Normothermic machine perfusion (NMP) could be used as a platform to assess the quality and function of donor kidneys. In addition, it could be useful to evaluate and possibly alter the immunological response of donor kidneys. In this study, we first evaluated whether complement was activated during NMP of porcine and human discarded kidneys. Second, we examined the relationship between complement activation and pro-inflammatory cytokines during NMP. Third, we assessed the effect of complement activation on renal function and injury during NMP of porcine kidneys. Lastly, we examined local complement C3d deposition in human renal biopsies after NMP.

Methods

NMP with a blood-based perfusion was performed with both porcine and discarded human kidneys for 4 and 6 h, respectively. Perfusate samples were taken every hour to assess complement activation, pro-inflammatory cytokines and renal function. Biopsies were taken to assess histological injury and complement deposition.

Results

Complement activation products C3a, C3d, and soluble C5b-9 (sC5b-9) were found in perfusate samples taken during NMP of both porcine and human kidneys. In addition, complement perfusate levels positively correlated with the cytokine perfusate levels of IL-6, IL-8, and TNF during NMP of porcine kidneys. Porcine kidneys with high sC5b-9 perfusate levels had significantly lower creatinine clearance after 4 h of NMP. In line with these findings, high complement perfusate levels were seen during NMP of human discarded kidneys. In addition, kidneys retrieved from brain-dead donors had significantly higher complement perfusate levels during NMP than kidneys retrieved from donors after circulatory death.

Conclusion

Normothermic kidney machine perfusion induces complement activation in porcine and human kidneys, which is associated with the release of pro-inflammatory cytokines and in porcine kidneys with lower creatinine clearance. Complement inhibition during NMP might be a promising strategy to reduce renal graft injury and improve graft function prior to transplantation.

Contemporary targeted temperature management: Clinical evidence and controversies

Advancements in cardiac arrest and post-cardiac arrest care have led to improved survival to hospital discharge. While survival to hospital discharge is an important clinical outcome, neurologic recovery is also a priority. With the advancement of targeted temperature management (TTM), the American Heart Association guidelines for post-cardiac arrest care recommend TTM in patients who remain comatose after return of spontaneous circulation (ROSC). Recently, the TTM2 randomized controlled trial found no significant difference in neurologic function and mortality at 6-months between traditional hypothermia to 33°C versus 37.5°C. While TTM has been evaluated for decades, current literature suggests that the use of TTM to 33° when compared to a protocol of targeted normothermia does not result in improved outcomes. Instead, perhaps active avoidance of fever may be most beneficial. Extracorporeal cardiopulmonary resuscitation and membrane oxygenation can provide a means of both hemodynamic support and TTM after ROSC. This review aims to describe the pathophysiology, physiologic aspects, clinical trial evidence, changes in post-cardiac arrest care, potential risks, as well as controversies of TTM.

Quality of targeted temperature management and outcome of out-of-hospital cardiac arrest patients: A post hoc analysis of the TTH48 study

BACKGROUND

No data are available on the quality of targeted temperature management (TTM) provided to out-of-hospital cardiac arrest (OHCA) patients and its association with outcome.

METHODS

Post hoc analysis of the TTH48 study (NCT01689077), which compared the effects of prolonged TTM at 33 °C for 48 h to standard 24-h TTM on neurologic outcome. Admission temperature, speed of cooling, rewarming rates, precision (i.e. temperature variability), overcooling and overshooting as post-cooling fever (i.e. >38.0 °C) were collected. A specific score, ranging from 1 to 9, was computed to define the "quality of TTM".

RESULTS

On a total of 352 patients, most had a moderate quality of TTM (n = 217; 62% - score 4-6), while 80 (23%) patients had a low quality of TTM (score 1-3) and only 52 (16%) a high quality of TTM (score 7-9). The proportion of patients with unfavorable neurological outcome (UO; Cerebral Performance Category of 3-5 at 6 months) was similar between the different quality of TTM groups (p = 0.90). Although a shorter time from arrest to target temperature and a lower proportion of time outside the target ranges in the TTM 48-h than in the TTM 24-h group, quality of TTM was similar between groups. Also, the proportion of patients with UO was similar between the different quality of TTM groups when TTM 48-h and TTM 24-h were compared.

CONCLUSIONS

In this study, high quality of TTM was provided to a small proportion of patients. However, quality of TTM was not associated with patients' outcome.

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.

Association of post-resuscitation inflammatory response with favorable neurologic outcomes in adults with in-hospital cardiac arrest

BACKGROUND

Early prediction of mortality in adults after in-hospital cardiac arrest (IHCA) remains vital to optimizing treatment strategies. Inflammatory cytokines specific to early prognostication in this population have not been well studied. We evaluated whether novel inflammatory cytokines obtained from adults with IHCA helped predict favorable neurologic outcome.

METHODS

The study population included adults with IHCA who underwent ACLS-guided resuscitation between March 2014 and May 2019 at an academic tertiary medical center. Peripheral blood samples were obtained within 6, 24, 48, 72, and 96 h of IHCA and analysis of 15 cytokines were performed. The primary outcome of interest was presence of favorable neurologic outcome at hospital discharge, defined as a Glasgow Outcome Score of 4 or 5.

RESULTS

Of the 105 adults with IHCA studied, 27 (25.7%) were noted to have survival with a favorable neurologic outcome while 78 (74.3%) did not. Patients who survived with favorable neurologic outcome were more often men (88.9% vs 61.5%, p = 0.008) and had higher rates of ventricular tachyarrhythmias as their initial rhythm (34.6% vs 11.7%, p = 0.018). Levels of interleukin (IL)-6, IL-8, IL-10, and Tumor Necrosis Factor (TNF)-R1 within 6 or 24 h were significantly lower in patients with favorable neurologic outcome compared with those who had unfavorable neurologic outcome. In multivariable analysis, IL-10 levels within 6 h was the only independent predictor of favorable neurologic outcomes [odds ratio (OR) 0.895, 95% confidence interval 0.805-0.996, p = 0.041].

CONCLUSION

In this contemporary observational study of adults with IHCA receiving ACLS-guided resuscitative and post-resuscitative care, inflammatory cytokines specific to early prognostication in adults with IHCA exist. Further larger scale studies examining the association of these inflammatory cytokines with prognosis are warranted.

Plasma proteomic changes during therapeutic hypothermia in resuscitated patients after cardiac arrest

Hypothermia is used for several h during cardiac and aortic surgery to protect ischemic organs. Therapeutic hypothermia (TH) is used for ≤24 h as a treatment for comatose patients after the return of spontaneous circulation (ROSC) following cardiac arrest. The proteomic approach may provide unbiased data on alterations in the abundance of proteins during TH. The objective of this study was to assess the effects of cooling/rewarming on the plasma proteome during TH after ROSC and to identify the mechanism underlying its therapeutic effects. A total of nine comatose adult patients, resuscitated shortly after cardiac arrest, were cooled to 34°C for 24 h and slowly rewarmed to 36°C. A quantitative gel-free proteomic analysis was performed using the isobaric tag for relative and absolute quantification labeling tandem mass spectrometry. Plasma samples were obtained prior to cooling and rewarming, and immediately after rewarming, from all patients during TH after ROSC. A total of 92 high-confidence proteins were identified. Statistically significant alterations were observed (>1.2-fold increase or <0.833-fold decrease) in the levels of 15 of those proteins (P=0.003–0.047), mainly proteins belonging to the acute-phase response or platelet degranulation. Unexpectedly, the levels of free hemoglobin (hemoglobin subunits α and β) were significantly downregulated during TH (P<0.05). The level of the terminal complement complex (SC5b-9) showed significant reduction after cooling (P=0.023). Although the acute-phase response proteins were upregulated, the abundance of complement proteins did not change, and the levels of SC5b-9 and free hemoglobin decreased during TH in patients after ROSC.

Pilot study on a rewarming rate of 0.15°C/hr versus 0.25°C/hr and outcomes in post cardiac arrest patients

Objective

Cerebral hemodynamic and metabolic changes may occur during the rewarming phase of targeted temperature management in post cardiac arrest patients. Yet, studies on different rewarming rates and patient outcomes are limited. This study aimed to investigate post cardiac arrest patients who were rewarmed with different rewarming rates after 24 hours of hypothermia and the association of these rates to the neurologic outcomes.

Methods

This study retrospectively investigated post cardiac arrest patients treated with targeted temperature management and rewarmed with rewarming rates of 0.15°C/hr and 0.25°C/hr. The association of the rewarming rate with poor neurologic outcomes (cerebral performance category score, 3 to 5) was investigated.

Results

A total of 71 patients were analyzed (0.15°C/hr, n=36; 0.25°C/hr, n=35). In the comparison between 0.15°C/hr and 0.25°C/hr, the poor neurologic outcome did not significantly differ (24 [66.7%] vs. 25 [71.4%], respectively; P=0.66). In the multivariate analysis, the rewarming rate of 0.15°C/hr was not associated with the 1-month neurologic outcome improvement (odds ratio, 0.54; 95% confidence interval, 0.16 to 1.69; P=0.28).

Conclusion

The rewarming rates of 0.15°C/hr and 0.25°C/hr were not associated with the neurologic outcome difference in post cardiac arrest patients.

The Role of Inflammatory Cytokines in Cardiac Arrest

Introduction:

Post-cardiac arrest syndrome (PCAS) is characterized by systemic ischemia/reperfusion injury, anoxic brain injury, and post-arrest myocardial dysfunction superimposed on a precipitating pathology. The role of inflammatory cytokines in cardiac arrest remains unclear.

Aims:

We aimed to describe, with an emphasis on clinical applications, what is known about the role of inflammatory cytokines in cardiac arrest.

Data Sources:

A PubMed literature review was performed for relevant articles. Only articles in English that studied cytokines in patients with cardiac arrest were included.

Results:

Cytokines play a crucial role in the pathogenesis of PCAS. Following cardiac arrest, the large release of circulating cytokines mediates the ischemia/reperfusion injury, brain dysfunction, and myocardial dysfunction seen. Interleukins, tumor necrosis factor, and matrix metalloproteinases all play a unique prognostic role in PCAS. High levels of inflammatory cytokines have been associated with mortality and/or poor neurologic outcomes. Interventions to modify the systemic inflammation seen in PCAS continue to be heavily studied. Currently, the only approved medical intervention for comatose patients following cardiac arrest is targeted temperature management. Medical agents, including minocycline and sodium sulfide, have demonstrated promise in animal models.

Conclusions:

The role of inflammatory cytokines for both short- and long-term outcomes is an important area for future investigation.

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.

Association between the neutrophil-to-lymphocyte ratio and neurological outcomes in patients undergoing targeted temperature management after cardiac arrest

PURPOSE

This study aimed to elucidate the association between the neutrophil-to-lymphocyte ratio (NLR) and neurological outcomes in out-of-hospital cardiac arrest (OHCA) patients treated with targeted temperature management (TTM).

MATERIALS AND METHODS

A retrospective study was performed on patients treated with TTM after OHCA. Patients were divided into two groups according to their calculated NLRs (NLR < 6 and NLR ≥ 6). The primary outcome was poor neurological outcome at 6 months as defined by a Cerebral Performance Category between 3 and 5.

RESULTS

A total of 216 were included and 131 subjects had poor neurological outcomes at 6 months. In the univariate model, NLRs ≥ 6 at 48 and 72 h after ROSC were associated with poor neurological outcomes (OR: 3.716, 95% CI: 1.243-11.114; OR: 7.429, 95% CI: 3.693-14.945, respectively). In the multivariate logistic regression analysis, an NLR ≥ 6 at 72 h was associated with poor neurological outcomes after adjusting for history of HTN, shockable rhythm, cardiac cause of arrest and time from collapse to ROSC and highest WBC, hs-CRP, lactate and pneumonia (OR = 3.299, 95% CI = 1.080-10.081).

CONCLUSIONS

An NLR ≥ 6 at 72 h after the ROSC is associated with poor neurological outcomes at 6 months after CA.

Significant Cytokine mRNA Expression Changes Immediately after Initiation of Cardiopulmonary Resuscitation

Introduction

The purpose of this study was to evaluate immediate immunological changes following cardiopulmonary resuscitation (CPR). mRNA expression levels of selected immunomodulatory cytokines in out-of-hospital cardiac arrest (OHCA) survivors were detected and correlated to clinical parameter.

Methods

OHCA survivors with sustained unconsciousness after return of spontaneous circulation (ROSC) were included. PAXgene whole blood samples were drawn immediately after initiation of CPR and subsequently after 6 h, 12 h, 24 h, 48 h, and 72 h. TNF-alpha, IL-8, IL-10, and IL-1ra mRNA levels were quantified by RT-qPCR and compared to multiple organ failure, 30-day survival, and the induction of therapeutic hypothermia (TH).

Results

25 patients (63 ± 15 years) were enrolled presenting a characteristic time-dependent cytokine profile in the early postresuscitation period. High initial TNF-alpha and IL-8 mRNA levels were followed by a significant decrease. IL-1ra mRNA levels significantly increased beginning after 6 h. Nonsurvivors showed significantly higher IL-8 mRNA levels immediately after CPR. TH induced significantly higher IL-1ra mRNA levels compared to normothermia.

Conclusion

Significant mRNA cytokine expression changes are already detectable immediately after initiation of CPR. These expressional changes are significantly different depending on 30-day survival. TH seems to attenuate proinflammatory immune reaction by a significant increase of IL-1ra mRNA levels. This trial is registered with DRKS00012940.

Targeted Temperature Management for 48 vs 24 Hours and Neurologic Outcome After Out-of-Hospital Cardiac Arrest: A Randomized Clinical Trial

IMPORTANCE

International resuscitation guidelines recommend targeted temperature management (TTM) at 33°C to 36°C in unconscious patients with out-of-hospital cardiac arrest for at least 24 hours, but the optimal duration of TTM is uncertain.

OBJECTIVE

To determine whether TTM at 33°C for 48 hours results in better neurologic outcomes compared with currently recommended, standard, 24-hour TTM.

DESIGN, SETTING, AND PARTICIPANTS

This was an international, investigator-initiated, blinded-outcome-assessor, parallel, pragmatic, multicenter, randomized clinical superiority trial in 10 intensive care units (ICUs) at 10 university hospitals in 6 European countries. Three hundred fifty-five adult, unconscious patients with out-of-hospital cardiac arrest were enrolled from February 16, 2013, to June 1, 2016, with final follow-up on December 27, 2016.

INTERVENTIONS

Patients were randomized to TTM (33 ± 1°C) for 48 hours (n = 176) or 24 hours (n = 179), followed by gradual rewarming of 0.5°C per hour until reaching 37°C.

MAIN OUTCOMES AND MEASURES

The primary outcome was 6-month neurologic outcome, with a Cerebral Performance Categories (CPC) score of 1 or 2 used to define favorable outcome. Secondary outcomes included 6-month mortality, including time to death, the occurrence of adverse events, and intensive care unit resource use.

RESULTS

In 355 patients who were randomized (mean age, 60 years; 295 [83%] men), 351 (99%) completed the trial. Of these patients, 69% (120/175) in the 48-hour group had a favorable outcome at 6 months compared with 64% (112/176) in the 24-hour group (difference, 4.9%; 95% CI, -5% to 14.8%; relative risk [RR], 1.08; 95% CI, 0.93-1.25; P = .33). Six-month mortality was 27% (48/175) in the 48-hour group and 34% (60/177) in the 24-hour group (difference, -6.5%; 95% CI, -16.1% to 3.1%; RR, 0.81; 95% CI, 0.59-1.11; P = .19). There was no significant difference in the time to mortality between the 48-hour group and the 24-hour group (hazard ratio, 0.79; 95% CI, 0.54-1.15; P = .22). Adverse events were more common in the 48-hour group (97%) than in the 24-hour group (91%) (difference, 5.6%; 95% CI, 0.6%-10.6%; RR, 1.06; 95% CI, 1.01-1.12; P = .04). The median length of intensive care unit stay (151 vs 117 hours; P < .001), but not hospital stay (11 vs 12 days; P = .50), was longer in the 48-hour group than in the 24-hour group.

CONCLUSIONS AND RELEVANCE

In unconscious survivors from out-of-hospital cardiac arrest admitted to the ICU, targeted temperature management at 33°C for 48 hours did not significantly improve 6-month neurologic outcome compared with targeted temperature management at 33°C for 24 hours. However, the study may have had limited power to detect clinically important differences, and further research may be warranted.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01689077.

Complement in renal transplantation: The road to translation

Renal transplantation is the treatment of choice for patients with end-stage renal disease. The vital role of the complement system in renal transplantation is widely recognized. This review discusses the role of complement in the different phases of renal transplantation: in the donor, during preservation, in reperfusion and at the time of rejection. Here we examine the current literature to determine the importance of both local and systemic complement production and how complement activation contributes to the pathogenesis of renal transplant injury. In addition, we dissect the complement pathways involved in the different phases of renal transplantation. We also review the therapeutic strategies that have been tested to inhibit complement during the kidney transplantation. Several clinical trials are currently underway to evaluate the therapeutic potential of complement inhibition for the treatment of brain death-induced renal injury, renal ischemia-reperfusion injury and acute rejection. We conclude that it is expected that in the near future, complement-targeted therapeutics will be used clinically in renal transplantation. This will hopefully result in improved renal graft function and increased graft survival.

Long-Term Effects of Induced Hypothermia on Local and Systemic Inflammation - Results from a Porcine Long-Term Trauma Model

Background

Hypothermia has been discussed as playing a role in improving the early phase of systemic inflammation. However, information on the impact of hypothermia on the local inflammatory response is sparse. We therefore investigated the kinetics of local and systemic inflammation in the late posttraumatic phase after induction of hypothermia in an established porcine long-term model of combined trauma.

Materials & Methods

Male pigs (35 ± 5kg) were mechanically ventilated and monitored over the study period of 48 h. Combined trauma included tibia fracture, lung contusion, liver laceration and pressure-controlled hemorrhagic shock (MAP < 30 ± 5 mmHg for 90 min). After resuscitation, hypothermia (33°C) was induced for a period of 12 h (HT-T group) with subsequent re-warming over a period of 10 h. The NT-T group was kept normothermic. Systemic and local (fracture hematoma) cytokine levels (IL-6, -8, -10) and alarmins (HMGB1, HSP70) were measured via ELISA.

Results

Severe signs of shock as well as systemic and local increases of pro-inflammatory mediators were observed in both trauma groups. In general the local increase of pro- and anti-inflammatory mediator levels was significantly higher and prolonged compared to systemic concentrations. Induction of hypothermia resulted in a significantly prolonged elevation of both systemic and local HMGB1 levels at 48 h compared to the NT-T group. Correspondingly, local IL-6 levels demonstrated a significantly prolonged increase in the HT-T group at 48 h.

Conclusion

A prolonged inflammatory response might reduce the well-described protective effects on organ and immune function observed in the early phase after hypothermia induction. Furthermore, local immune response also seems to be affected. Future studies should aim to investigate the use of therapeutic hypothermia at different degrees and duration of application.

Time-differentiated target temperature management after out-of-hospital cardiac arrest: a multicentre, randomised, parallel-group, assessor-blinded clinical trial (the TTH48 trial): study protocol for a randomised controlled trial

BACKGROUND

The application of therapeutic hypothermia (TH) for 12 to 24 hours following out-of-hospital cardiac arrest (OHCA) has been associated with decreased mortality and improved neurological function. However, the optimal duration of cooling is not known. We aimed to investigate whether targeted temperature management (TTM) at 33 ± 1 °C for 48 hours compared to 24 hours results in a better long-term neurological outcome.

METHODS

The TTH48 trial is an investigator-initiated pragmatic international trial in which patients resuscitated from OHCA are randomised to TTM at 33 ± 1 °C for either 24 or 48 hours. Inclusion criteria are: age older than 17 and below 80 years; presumed cardiac origin of arrest; and Glasgow Coma Score (GCS) <8, on admission. The primary outcome is neurological outcome at 6 months using the Cerebral Performance Category score (CPC) by an assessor blinded to treatment allocation and dichotomised to good (CPC 1-2) or poor (CPC 3-5) outcome. Secondary outcomes are: 6-month mortality, incidence of infection, bleeding and organ failure and CPC at hospital discharge, at day 28 and at day 90 following OHCA. Assuming that 50 % of the patients treated for 24 hours will have a poor outcome at 6 months, a study including 350 patients (175/arm) will have 80 % power (with a significance level of 5 %) to detect an absolute 15 % difference in primary outcome between treatment groups. A safety interim analysis was performed after the inclusion of 175 patients.

DISCUSSION

This is the first randomised trial to investigate the effect of the duration of TTM at 33 ± 1 °C in adult OHCA patients. We anticipate that the results of this trial will add significant knowledge regarding the management of cooling procedures in OHCA patients.

TRIAL REGISTRATION

NCT01689077.

Ischemia reperfusion injury as a modifiable therapeutic target for cardioprotection or neuroprotection in patients undergoing cardiopulmonary resuscitation

AIMS

We sought to review cellular changes that occur with reperfusion to try to understand whether ischemia-reperfusion injury (RI) is a potentially modifiable therapeutic target for cardioprotection or neuroprotection in patients undergoing cardiopulmonary resuscitation.

DATA SOURCES

Articles written in English and published in PubMed.

RESULTS

Remote ischemic conditioning (RIC) involves brief episodes of non-lethal ischemia and reperfusion applied to an organ or limb distal to the heart and brain. Induction of hypothermia involves cooling an ischemic organ or body. Both have pluripotent effects that reduce the potential harm associated with RI in the heart and brain by reduced opening of the mitochondrial permeability transition pore. Recent trials of RIC and induced hypothermia did not demonstrate these treatments to be effective. Assessment of the effect of these interventions in humans to date may have been modified by use of concurrent medications including propofol.

CONCLUSIONS

Ongoing research is necessary to assess whether reduction of RI improves patient outcomes.

Therapeutic Hypothermia After Cardiac Arrest

OPINION STATEMENT

Resuscitated cardiac arrest continues to carry a poor prognosis despite advances in medical care. One such advance, therapeutic hypothermia, is neuroprotective and has been demonstrated to improve clinical outcomes in patients who remain unresponsive despite return of spontaneous circulation after arrhythmogenic cardiac arrest. Two landmark randomized controlled trials, both reported in 2002, led to endorsements by major American and European guidelines for therapeutic hypothermia as a viable treatment option for the prevention of adverse outcomes related to anoxic encephalopathy. Since then, significant research has been conducted to better understand the optimum strategies to maximize the neuroprotective effects of hypothermia. However, dissemination of therapeutic hypothermia guideline recommendations into clinical practice has been slow and incomplete. In this review article, we discuss the historical background and physiologic rationale for therapeutic hypothermia, review the recent literature supporting this intervention, and outline practical considerations.

Changes in coagulation during therapeutic hypothermia in cardiac arrest patients

AIM

Therapeutic hypothermia improves neurological outcome in patients resuscitated after out-of-hospital cardiac arrest. The aim was to investigate whether therapeutic hypothermia induced impaired coagulation.

METHODS

Changes in coagulation were investigated in 22 out-of-hospital cardiac arrest patients treated with therapeutic hypothermia (33 ± 1 °C). Blood samples were obtained after 22 ± 2h of hypothermia and compared with normothermic samples drawn 48 h later. The coagulation was evaluated with thromboelastometry (ROTEM(®)) using a sensitive low-tissue-factor assay. Leukocytes, haemoglobin, haematocrit, platelet count, activated partial thromboplastin time (aPTT), thrombin time, international normalised ratio (INR) and fibrinogen were also measured. Clinical information including use of anti thrombotic drugs was systematically collected.

RESULTS

No significant changes were found in clotting time (p=0.21), clot formation time (p=0.26), time to maximum velocity (p=0.52) or maximum velocity (p=0.17) when results obtained at hypothermia were compared with results obtained at normothermia. Maximum clot firmness (p<0.01) and fibrinogen levels (p<0.01) were significantly higher in patients at normothermia. However, the fibrinogen levels were within the reference interval for all patients at both hypothermia and normothermia. Values of aPTT, thrombin time and INR at hypothermia and normothermia were not significantly different.

CONCLUSIONS

No substantial difference in coagulation was found in hypothermia compared with normothermia in out-of-hospital cardiac arrest patients. The results indicate that treatment with hypothermia does not impair coagulation.

CLINICALTRIALS IDENTIFIER

NCT02179021.

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.

Novel Uses of Targeted Temperature Management

Targeted temperature management has an established role in treating the post-cardiac arrest syndrome after out-of-hospital cardiac arrest with an initial rhythm of ventricular tachycardia/ventricular fibrillation. There is less certain benefit if the initial rhythm is pulseless electrical activity/asystole or for in-hospital cardiac arrest. Targeted temperature management may have a role as salvage modality for conditions causing intracranial hypertension, such as traumatic brain injury, hepatic encephalopathy, intracerebral hemorrhage, and acute stroke. There is variable evidence for its use early in these disorders to minimize secondary neurologic injury.

Effectiveness of lower target temperature therapeutic hypothermia in post-cardiac arrest syndrome patients with a resuscitation interval of ≤30 min

Background

Therapeutic hypothermia (TH) is a standard strategy to reduce brain damage in post-cardiac arrest syndrome (PCAS) patients. However, it is unknown whether the target temperature should be adjusted for PCAS patients in different states.

Methods

Participants in the J-PULSE-Hypo study database were divided into lower (32.0–33.5 °C; Group L) or moderate (34.0–35.0 °C; Group M) temperature groups. Primary outcome was a favourable neurological outcome (proportion of patients with a Glasgow-Pittsburgh Cerebral Performance Category [CPC] of 1–2 on day 30). We compared between the two groups and in subgroups of patients divided by age and resuscitation interval (interval from collapse to return of spontaneous circulation) by propensity score (PS) analysis.

Results

Overall, 467 participants were analysed. The proportions of patients with favourable neurological outcomes were as follows (Group L vs. Group M) (OR; Odds ratio): all patients, 64 % (n = 42) vs. 55 % ((n = 424) (PS; OR 1.381 (0.596–3.197)), P = 0.452) and resuscitation interval ≤ 30 min, 88 % (n = 24) vs. 64 % ((n = 281) (PS; OR 7.438 (1.769–31.272)), P = 0.007).

Conclusions

PCAS patients with a resuscitation interval of <30 min may be candidates for TH with a target temperature of <34 °C.

Trial registration

University Hospital Medical Information Network (UMIN) Clinical Trials Registry UMIN000001935; available at: https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr.cgi?function=brows&action=brows&type=summary&recptno=R000002348&language=J.

Cardiac arrest survivors treated with or without mild therapeutic hypothermia: performance status and quality of life assessment

BACKGROUND

Hypoxic-ischaemic encephalopathy is the main determinant of clinical outcome after cardiac arrest. The study was designed to determine long-term neurological and psychological status in cardiac arrest survivors, as well as to compare neuropsychological outcomes between patients treated with mild therapeutic hypothermia (MTH) and patients who did not undergo hypothermia treatment.

METHODS

The article describes a single-center, retrospective, observational study on 28 post-cardiac arrest adult patients treated in the cardiac intensive care unit who qualified for MTH vs. 37 control group patients, hospitalized at the same center following cardiac arrest in the preceding years and fulfilling criteria for induced hypothermia, but who were not treated due to unavailability of the method at that time. Disability Rating Scale (DRS), Barthel Index and RAND-36 were used to assess performance status and quality of life in both study groups after hospital discharge.

RESULTS

There were no statistically significant differences in physical functioning found between groups either at the end of hospital treatment or at long-term follow-up (DRS: p = 0.11; Barthel Index: p = 0.83). In long-term follow-up, MTH patients showed higher vitality (p = 0.02) and reported fewer complaints on role limitations due to emotional problems (p = 0.04) compared to the control group. No significant differences were shown between study groups in terms of physical capacity and independent functioning.

CONCLUSION

To conclude, in long-term follow-up, MTH patients showed higher vitality and reported fewer complaints on role limitations due to emotional problems compared to the control group. This suggest that MTH helps to preserve global brain function in cardiac arrest survivors. However, the results can be biased by a small sample size and variable observation periods.