Intensive care medicine research agenda on cardiac arrest

Neuroimmune activation is associated with neurological outcome in anoxic and traumatic coma

The pathophysiological underpinnings of critically disrupted brain connectomes resulting in coma are poorly understood. Inflammation is potentially an important but still undervalued factor. Here, we present a first-in-human prospective study using the 18-kDa translocator protein (TSPO) radioligand 18F-DPA714 for PET imaging to allow in vivo neuroimmune activation quantification in patients with coma (n = 17) following either anoxia or traumatic brain injuries in comparison with age- and sex-matched controls. Our findings yielded novel evidence of an early inflammatory component predominantly located within key cortical and subcortical brain structures that are putatively implicated in consciousness emergence and maintenance after severe brain injury (i.e. mesocircuit and frontoparietal networks). We observed that traumatic and anoxic patients with coma have distinct neuroimmune activation profiles, both in terms of intensity and spatial distribution. Finally, we demonstrated that both the total amount and specific distribution of PET-measurable neuroinflammation within the brain mesocircuit were associated with the patient's recovery potential. We suggest that our results can be developed for use both as a new neuroprognostication tool and as a promising biometric to guide future clinical trials targeting glial activity very early after severe brain injury.

Wolf Creek XVII Part 8: Neuroprotection

Introduction

Post-cardiac arrest brain injury (PCABI) is the primary determinant of clinical outcomes for patients who achieve return of spontaneous circulation after cardiac arrest (CA). There are limited neuroprotective therapies available to mitigate the acute pathophysiology of PCABI.

Methods

Neuroprotection was one of six focus topics for the Wolf Creek XVII Conference held on June 14-17, 2023 in Ann Arbor, Michigan, USA. Conference invitees included international thought leaders and scientists in the field of CA resuscitation from academia and industry. Participants submitted via online survey knowledge gaps, barriers to translation, and research priorities for each focus topic. Expert panels used the survey results and their own perspectives and insights to create and present a preliminary unranked list for each category that was debated, revised and ranked by all attendees to identify the top 5 for each category.

Results

Top 5 knowledge gaps included developing therapies for neuroprotection; improving understanding of the pathophysiology, mechanisms, and natural history of PCABI; deploying precision medicine approaches; optimizing resuscitation and CPR quality; and determining optimal timing for and duration of interventions. Top 5 barriers to translation included patient heterogeneity; nihilism & lack of knowledge about cardiac arrest; challenges with the translational pipeline; absence of mechanistic biomarkers; and inaccurate neuro-triage and neuroprognostication. Top 5 research priorities focused on translational research and trial optimization; addressing patient heterogeneity and individualized interventions; improving understanding of pathophysiology and mechanisms; developing mechanistic and outcome biomarkers across post-CA time course; and improving implementation of science and technology.

Conclusion

This overview can serve as a guide to transform the care and outcome of patients with PCABI. Addressing these topics has the potential to improve both research and clinical care in the field of neuroprotection for PCABI.

Association between the Cardiac Arrest Hospital Prognosis (CAHP) score and reason for death after successfully resuscitated cardiac arrest

Individualize treatment after cardiac arrest could potentiate future clinical trials selecting patients most likely to benefit from interventions. We assessed the Cardiac Arrest Hospital Prognosis (CAHP) score for predicting reason for death to improve patient selection. Consecutive patients in two cardiac arrest databases were studied between 2007 and 2017. Reasons for death were categorised as refractory post-resuscitation shock (RPRS), hypoxic-ischaemic brain injury (HIBI) and other. We computed the CAHP score, which relies on age, location at OHCA, initial cardiac rhythm, no-flow and low-flow times, arterial pH, and epinephrine dose. We performed survival analyses using the Kaplan-Meier failure function and competing-risks regression. Of 1543 included patients, 987 (64%) died in the ICU, 447 (45%) from HIBI, 291 (30%) from RPRS, and 247 (25%) from other reasons. The proportion of deaths from RPRS increased with CAHP score deciles; the sub-hazard ratio for the tenth decile was 30.8 (9.8-96.5; p < 0.0001). The sub-hazard ratio of the CAHP score for predicting death from HIBI was below 5. Higher CAHP score values were associated with a higher proportion of deaths due to RPRS. This score may help to constitute uniform patient populations likely to benefit from interventions assessed in future randomised controlled trials.

Morbidity and Mortality in Critically Ill Children. II. A Qualitative Patient-Level Analysis of Pathophysiologies and Potential Therapeutic Solutions

OBJECTIVES

To describe at the individual patient level the pathophysiologic processes contributing to morbidity and mortality in PICUs and therapeutic additions and advances that could potentially prevent or reduce morbidity and mortality.

DESIGN

Qualitative content analysis of intensivists' conclusions on pathophysiologic processes and needed therapeutic advances formulated by structured medical record review.

SETTING

Eight children's hospitals affiliated with the Eunice Kennedy Shriver National Institute of Child Health and Human Development Collaborative Pediatric Critical Care Research Network.

PATIENTS

A randomly selected cohort of critically ill children with a new functional morbidity or mortality at hospital discharge. New morbidity was assessed using the Functional Status Scale and defined as worsening by two or more points in a single domain from preillness baseline.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 292 children, 175 (59.9%) had a new morbidity and 117 (40.1%) died. The most common pathophysiology was impaired substrate delivery (n = 158, 54.1%) manifesting as global or regional hypoxia or ischemia due to low cardiac output or cardiac arrest. Other frequent pathophysiologies were inflammation (n = 104, 35.6%) related to sepsis, respiratory failure, acute respiratory distress syndrome, or multiple organ dysfunction; and direct tissue injury (n = 64, 21.9%) including brain and spinal cord trauma. Chronic conditions were often noted (n = 156, 53.4%) as contributing to adverse outcomes. Drug therapies (n = 149, 51.0%) including chemotherapy, inotropes, vasoactive agents, and sedatives were the most frequently proposed needed therapeutic advances. Other frequently proposed therapies included cell regeneration (n = 115, 39.4%) mainly for treatment of neuronal injury, and improved immune and inflammatory modulation (n = 79, 27.1%).

CONCLUSIONS

Low cardiac output and cardiac arrest, inflammation-related organ failures, and CNS trauma were the most common pathophysiologies leading to morbidity and mortality in PICUs. A research agenda focused on better understanding and treatment of these conditions may have high potential to directly impact patient outcomes.

Are neurophysiologic tests reliable, ultra-early prognostic indices after cardiac arrest?

OBJECTIVES

Determining early and reliable prognosis in comatose subjects after cardiac arrest is a central component of post-cardiac arrest care both for developing realistic prognostic expectations for families, and for better determining which resources are mobilized or withheld for individual patients. The aim of the study was to evaluate the prognostic accuracy of EEG and SEP patterns during the very early period (within the first 6 h) after cardiac arrest.

METHODS

We retrospectively analysed comatose patients after CA, either inside or outside the hospital, in which prognostic evaluation was made during the first 6 h from CA. Prognostic evaluation comprised clinical evaluation (GCS and pupillary light reflex) and neurophysiological (electroencephalography (EEG) and somatosensory evoked potentials (SEP)) studies. Prognosis was evaluated with regards to likelihood of recovery of consciousness and also likelihood of failure to regain consciousness.

RESULTS

Forty-one comatose patients after cardiac arrest were included. All patients with continuous and nearly continuous EEG recovered consciousness. Isoelectric EEG was always associated with poor outcome. Burst-suppression, suppression and discontinuous patterns were usually associated with poor outcome although some consciousness recovery was observed. Bilaterally absent SEP responses were always associated with poor outcome. Continuous and nearly continuous EEG patterns were never associated with bilaterally absent SEP.

CONCLUSIONS

During the very early period following cardiac arrest (first 6 h), EEG and SEP maintain their high predictive value to predict respectively recovery and failure of recovery of consciousness. A very early EEG exam allows identification of patients with very high probability of a good outcome, allowing rapid use of the most appropriate therapeutic procedures.

A novel ultrasound-guided mouse model of sudden cardiac arrest

AIM

Mouse models of sudden cardiac arrest are limited by challenges with surgical technique and obtaining reliable venous access. To overcome this limitation, we sought to develop a simplified method in the mouse that uses ultrasound-guided injection of potassium chloride directly into the heart.

METHODS

Potassium chloride was delivered directly into the left ventricular cavity under ultrasound guidance in intubated mice, resulting in immediate asystole. Mice were resuscitated with injection of epinephrine and manual chest compressions and evaluated for survival, body temperature, cardiac function, kidney damage, and diffuse tissue injury.

RESULTS

The direct injection sudden cardiac arrest model causes rapid asystole with high surgical survival rates and short surgical duration. Sudden cardiac arrest mice with 8-min of asystole have significant cardiac dysfunction at 24 hours and high lethality within the first seven days, where after cardiac function begins to improve. Sudden cardiac arrest mice have secondary organ damage, including significant kidney injury but no significant change to neurologic function.

CONCLUSIONS

Ultrasound-guided direct injection of potassium chloride allows for rapid and reliable cardiac arrest in the mouse that mirrors human pathology without the need for intravenous access. This technique will improve investigators' ability to study the mechanisms underlying post-arrest changes in a mouse model.

Neurofilament light as an outcome predictor after cardiac arrest: a post hoc analysis of the COMACARE trial

Purpose

Neurofilament light (NfL) is a biomarker reflecting neurodegeneration and acute neuronal injury, and an increase is found following hypoxic brain damage. We assessed the ability of plasma NfL to predict outcome in comatose patients after out-of-hospital cardiac arrest (OHCA). We also compared plasma NfL concentrations between patients treated with two different targets of arterial carbon dioxide tension (PaCO₂), arterial oxygen tension (PaO₂), and mean arterial pressure (MAP).

Methods

We measured NfL concentrations in plasma obtained at intensive care unit admission and at 24, 48, and 72 h after OHCA. We assessed neurological outcome at 6 months and defined a good outcome as Cerebral Performance Category (CPC) 1–2 and poor outcome as CPC 3–5.

Results

Six-month outcome was good in 73/112 (65%) patients. Forty-eight hours after OHCA, the median NfL concentration was 19 (interquartile range [IQR] 11–31) pg/ml in patients with good outcome and 2343 (587–5829) pg/ml in those with poor outcome, p < 0.001. NfL predicted poor outcome with an area under the receiver operating characteristic curve (AUROC) of 0.98 (95% confidence interval [CI] 0.97–1.00) at 24 h, 0.98 (0.97–1.00) at 48 h, and 0.98 (0.95–1.00) at 72 h. NfL concentrations were lower in the higher MAP (80–100 mmHg) group than in the lower MAP (65–75 mmHg) group at 48 h (median, 23 vs. 43 pg/ml, p = 0.04). PaCO₂ and PaO₂ targets did not associate with NfL levels.

Conclusions

NfL demonstrated excellent prognostic accuracy after OHCA. Higher MAP was associated with lower NfL concentrations.

Electronic supplementary material

The online version of this article (10.1007/s00134-020-06218-9) contains supplementary material, which is available to authorized users.

Mind the gap: Knowledge deficits in evaluating young sudden cardiac death

Sudden cardiac arrest affects around half a million people aged under 50 years old annually, with a 90% mortality rate. Despite high patient numbers and clear clinical need to improve outcomes, many gaps exist in the evidence underpinning patients' management. Domains identifying the greatest barriers to conducting trials are the prehospital and forensic settings, which also provide care to the majority of patients. Addressing gaps in evidence along each point of the cardiac arrest trajectory is a key clinical priority.

Postcardiac arrest neurological prognostication with quantitative regional cerebral densitometry

PURPOSE

To quantitatively assess the severity of anoxic-ischemic brain injury early after cardiac arrest (CA) using a novel automated method applied to head computed tomography (HCT).

METHODS

Adult patients who were comatose and underwent HCT < 24 h after arrest were included in a retrospective analysis. Principal endpoint was unfavorable outcome (UO) defined as Cerebral Performance Category (CPC) of 3-5 at hospital discharge. We developed an automated processing algorithm for HCT images to be registered, atlas-segmented in 181 regions, and region-specific radiologic densities determined in Hounsfield Units. This approach was compared with an established manual method evaluating grey-white matter ratios (GWR). We tested univariable and multivariable prognostic models which integrated clinical and HCT features including densities in lobes and in nodes of cerebral networks linked to CA recovery.

RESULTS

Ninety-one patients were enrolled among whom 66 (73%) had an UO. HCTs were interpreted as normal or without acute abnormality by a neuroradiologist in 77 cases (85%). Compared to the favorable outcome group, UO patients had significantly lower densities in all lobes and in nodes of cerebral networks. A model combining clinical variables with the automated method applied to cerebral network nodes had the highest prognostic performance although not significantly different than the combined clinical-GWR method (AUC [95% CI] 0.94 [0.86-1.00] and 0.92 [0.83-1.00] respectively).

CONCLUSION

In comatose survivors of CA, automated quantitative analysis of HCT revealed very early multifocal changes in brain tissue density which are mostly overlooked on conventional neuroradiologic interpretation and are associated with neurological outcome.

Grafted Neural Progenitor Cells Persist in the Injured Site and Differentiate Neuronally in a Rodent Model of Cardiac Arrest-Induced Global Brain Ischemia

Hypoxic-ischemic brain injury is the leading cause of disability and death after successful resuscitation from cardiac arrest, and, to date, no specific treatment option is available to prevent subsequent neurofunctional impairments. The hippocampal cornu ammonis segment 1 (CA1) is one of the brain areas most affected by hypoxia, and its degeneration is correlated with memory deficits in patients and corresponding animal models. The aim of this work was to evaluate the feasibility of neural progenitor cell (NPC) transplantation into the hippocampus in a refined rodent cardiac arrest model. Adult rats were subjected to 12 min of potassium-induced cardiac arrest and followed up to 6 weeks. Histological analysis showed extensive neuronal cell death specifically in the hippocampal CA1 segment, without any spontaneous regeneration. Neurofunctional assessment revealed transient memory deficits in ischemic animals compared to controls, detectable after 4 weeks, but not after 6 weeks. Using stereotactic surgery, embryonic NPCs were transplanted in a subset of animals 1 week after cardiac arrest and their survival, migration, and differentiation were assessed histologically. Transplanted cells showed a higher persistence in the CA1 segment of animals after ischemia. Glia in the damaged CA1 segment expressed the chemotactic factor stromal cell-derived factor 1 (SDF-1), while transplanted NPCs expressed its receptor CXC chemokine receptor 4 (CXCR4), suggesting that the SDF-1/CXCR4 pathway, known to be involved in the migration of neural stem cells toward injured brain regions, directs the observed retention of cells in the damaged area. Using immunostaining, we could demonstrate that transplanted cells differentiated into mature neurons. In conclusion, our data document the survival, persistence in the injured area, and neuronal differentiation of transplanted NPCs, and thus their potential to support brain regeneration after hypoxic-ischemic injury. This may represent an option worth further investigation to improve the outcome of patients after cardiac arrest.

Moderate Hypothermia Modifies Coronary Hemodynamics and Endothelium-Dependent Vasodilation in a Porcine Model of Temperature Management

Background Hypothermia has been associated with therapeutic benefits including reduced mortality and better neurologic outcomes in survivors of cardiac arrest. However, undesirable side effects have been reported in patients undergoing coronary interventions. Using a large animal model of temperature management, we aimed to describe how temperature interferes with the coronary vasculature. Methods and Results Coronary hemodynamics and endothelial function were studied in 12 pigs at various core temperatures. Left circumflex coronary artery was challenged with intracoronary nitroglycerin, bradykinin, and adenosine at normothermia (38°C) and mild hypothermia (34°C), followed by either rewarming (38°C; n=6) or moderate hypothermia (MoHT; 32°C, n=6). Invasive coronary hemodynamics by Doppler wire revealed a slower coronary blood velocity at 32°C in the MoHT protocol (normothermia 20.2±11.2 cm/s versus mild hypothermia 18.7±4.3 cm/s versus MoHT 11.3±5.3 cm/s, P=0.007). MoHT time point was also associated with high values of hyperemic microvascular resistance (>3 mm Hg/cm per second) (normothermia 2.0±0.6 mm Hg/cm per second versus mild hypothermia 2.0±0.8 mm Hg/cm per second versus MoHT 3.4±1.6 mm Hg/cm per second, P=0.273). Assessment of coronary vasodilation by quantitative coronary analysis showed increased endothelium-dependent (bradykinin) vasodilation at 32°C when compared with normothermia (normothermia 6.96% change versus mild hypothermia 9.01% change versus MoHT 25.42% change, P=0.044). Results from coronary reactivity in vitro were in agreement with angiography data and established that endothelium-dependent relaxation in MoHT completely relies on NO production. Conclusions In this porcine model of temperature management, 34°C hypothermia and rewarming (38°C) did not affect coronary hemodynamics or endothelial function. However, 32°C hypothermia altered coronary vasculature physiology by slowing coronary blood flow, increasing microvascular resistance, and exacerbating endothelium-dependent vasodilatory response.

The optimal peripheral oxygen saturation may be 95-97% for post-cardiac arrest patients: A retrospective observational study

BACKGROUND

Current post-resuscitation guidelines recommend oxygen titration in adults with the return of spontaneous circulation after cardiac arrest. However, the optimal peripheral oxygen saturation (SpO₂) is still unclear for post-cardiac arrest care.

METHODS

We conducted a retrospective observational study of prospectively collected data of all cardiac arrest patients admitted to the intensive care units between 2014 and 2015. The main exposure was SpO₂, which were interfaced from bedside vital signs monitors as 1-min averages, and archived as 5-min median values. The proportion of time spent in different SpO₂ categories was included in separate multivariable regression models along with covariates. The primary outcome measure was hospital mortality and the proportion of discharged home as the secondary outcome was reported.

RESULTS

2836 post-cardiac arrest patients in ICUs of 156 hospitals were included. 1235 (44%) patients died during hospitalization and 818 (29%) patients discharged home. With multivariate regression analysis, the proportion of time spent in SpO₂ of ≤89%, 90%, 91%, and 92% were associated with higher hospital mortality. The proportion of time spent in SpO₂ of 95%, 96%, and 97% were associated with a higher proportion of discharged home outcome, but not associated with hospital mortality.

CONCLUSIONS

In this retrospective observational study, the optimal SpO₂ for patients admitted to the intensive care unit after cardiac arrest may be 95-97%. Further investigation is warranted to determine if targeting SpO₂ of 95-97% would improve patient-centered outcomes after cardiac arrest.

Quantitative versus standard pupillary light reflex for early prognostication in comatose cardiac arrest patients: an international prospective multicenter double-blinded study

Purpose

To assess the ability of quantitative pupillometry [using the Neurological Pupil index (NPi)] to predict an unfavorable neurological outcome after cardiac arrest (CA).

Methods

We performed a prospective international multicenter study (10 centers) in adult comatose CA patients. Quantitative NPi and standard manual pupillary light reflex (sPLR)—blinded to clinicians and outcome assessors—were recorded in parallel from day 1 to 3 after CA. Primary study endpoint was to compare the value of NPi versus sPLR to predict 3-month Cerebral Performance Category (CPC), dichotomized as favorable (CPC 1–2: full recovery or moderate disability) versus unfavorable outcome (CPC 3–5: severe disability, vegetative state, or death).

Results

At any time between day 1 and 3, an NPi ≤ 2 (n = 456 patients) had a 51% (95% CI 49–53) negative predictive value and a 100% positive predictive value [PPV; 0% (0–2) false-positive rate], with a 100% (98–100) specificity and 32% (27–38) sensitivity for the prediction of unfavorable outcome. Compared with NPi, sPLR had significantly lower PPV and significantly lower specificity (p  < 0.001 at day 1 and 2; p  = 0.06 at day 3). The combination of NPi ≤ 2 with bilaterally absent somatosensory evoked potentials (SSEP; n = 188 patients) provided higher sensitivity [58% (49–67) vs. 48% (39–57) for SSEP alone], with comparable specificity [100% (94–100)].

Conclusions

Quantitative NPi had excellent ability to predict an unfavorable outcome from day 1 after CA, with no false positives, and significantly higher specificity than standard manual pupillary examination. The addition of NPi to SSEP increased sensitivity of outcome prediction, while maintaining 100% specificity.

Electronic supplementary material

The online version of this article (10.1007/s00134-018-5448-6) contains supplementary material, which is available to authorized users.

A multicentre randomized pilot trial on the effectiveness of different levels of cooling in comatose survivors of out-of-hospital cardiac arrest: the FROST-I trial

PURPOSE

To obtain initial data on the effect of different levels of targeted temperature management (TTM) in out-of-hospital cardiac arrest (OHCA).

METHODS

We designed a multicentre pilot trial with 1:1:1 randomization to either 32 °C (n = 52), 33 °C (n = 49) or 34 °C (n = 49), via endovascular cooling devices during a 24-h period in comatose survivors of witnessed OHCA and initial shockable rhythm. The primary endpoint was the percentage of subjects surviving with good neurologic outcome defined by a modified Rankin Scale (mRS) score of ≤ 3, blindly assessed at 90 days.

RESULTS

At baseline, different proportions of patients who had received defibrillation administered by a bystander were assigned to groups of 32 °C (13.5%), 33 °C (34.7%) and 34 °C (28.6%; p = 0.03). The percentage of patients with an mRS ≤ 3 at 90 days (primary endpoint) was 65.3, 65.9 and 65.9% in patients assigned to 32, 33 and 34 °C, respectively, non-significant (NS). The multivariate Cox proportional hazards model identified two variables significantly related to the primary outcome: male gender and defibrillation by a bystander. Among the 43 patients who died before 90 days, 28 died following withdrawal of life-sustaining therapy, as follows: 7/16 (43.8%), 10/13 (76.9%) and 11/14 (78.6%) of patients assigned to 32, 33 and 34 °C, respectively (trend test p = 0.04). All levels of cooling were well tolerated.

CONCLUSIONS

There were no statistically significant differences in neurological outcomes among the different levels of TTM. However, future research should explore the efficacy of TTM at 32 °C.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov unique identifier: NCT02035839 ( http://clinicaltrials.gov ).

Mechanical CPR: Who? When? How?

In cardiac arrest, high quality cardiopulmonary resuscitation (CPR) is a key determinant of patient survival. However, delivery of effective chest compressions is often inconsistent, subject to fatigue and practically challenging.

Mechanical CPR devices provide an automated way to deliver high-quality CPR. However, large randomised controlled trials of the routine use of mechanical devices in the out-of-hospital setting have found no evidence of improved patient outcome in patients treated with mechanical CPR, compared with manual CPR. The limited data on use during in-hospital cardiac arrest provides preliminary data supporting use of mechanical devices, but this needs to be robustly tested in randomised controlled trials.

In situations where high-quality manual chest compressions cannot be safely delivered, the use of a mechanical device may be a reasonable clinical approach. Examples of such situations include ambulance transportation, primary percutaneous coronary intervention, as a bridge to extracorporeal CPR and to facilitate uncontrolled organ donation after circulatory death.

The precise time point during a cardiac arrest at which to deploy a mechanical device is uncertain, particularly in patients presenting in a shockable rhythm. The deployment process requires interruptions in chest compression, which may be harmful if the pause is prolonged. It is recommended that use of mechanical devices should occur only in systems where quality assurance mechanisms are in place to monitor and manage pauses associated with deployment.

In summary, mechanical CPR devices may provide a useful adjunct to standard treatment in specific situations, but current evidence does not support their routine use.

Research questions in pre-hospital trauma care

Noting that a variety of pre-hospital interventions can now be applied to treat traumatic injury, David J Lockey calls for research to determine which of these actually improve survival and reduce morbidity.

Improving CPR Performance

Cardiac arrest continues to represent a public health burden with most patients having dismal outcomes. CPR is a complex set of interventions requiring leadership, coordination, and best practices. Despite the widespread adoption of new evidence in various guidelines, the provision of CPR remains variable with poor adherence to published recommendations. Key steps health-care systems can take to enhance the quality of CPR and, potentially, to improve outcomes, include optimizing chest compressions, avoiding hyperventilation, encouraging intraosseous access, and monitoring capnography. Feedback devices provide instantaneous guidance to the rescuer, improve rescuer technique, and could impact patient outcomes. New technologies promise to improve the resuscitation process: mechanical devices standardize chest compressions, capnography guides resuscitation efforts and signals the return of spontaneous circulation, and intraosseous devices minimize interruptions to gain vascular access. This review aims at identifying a discreet group of interventions that health-care systems can use to raise their standard of cardiac resuscitation.