Cerebral Perfusion and Cerebral Autoregulation after Cardiac Arrest

Risk factors for neurological disability outcomes in patients under extracorporeal membrane oxygenation following cardiac arrest: An observational study

OBJECTIVES

This study aimed to identify factors associated with neurological and disability outcomes in patients who underwent ECMO following cardiac arrest.

METHODS

This retrospective, single-center, observational study included adult patients who received ECMO treatment for in-hospital cardiac arrest (IHCA) or out-of-hospital cardiac arrest (OHCA) between February 2016 and March 2020. Factors associated with neurological and disability outcomes in these patients who underwent ECMO were assessed.

SETTING

Hamad General Hospital, Qatar.

MAIN OUTCOME MEASURES

Neurological disability outcomes were assessed using the Modified Rankin Scale (mRS) and the Cerebral Performance Category (CPC) scale.

RESULTS

Among the 48 patients included, 37 (77 %) experienced OHCA, and 11 (23 %) had IHCA. The 28-day survival rate was 14 (29.2 %). Of the survivors, 9 (64.3 %) achieved a good neurological outcome, while 5 (35.7 %) experienced poor neurological outcomes. Regarding disability, 5 (35.7 %) of survivors had no disability, while 9 (64.3 %) had some form of disability. The results showed significantly shorter median time intervals in minutes, including collapse to cardiopulmonary resuscitation (CPR) (3 vs. 6, P = 0.001), CPR duration (12 vs. 35, P = 0.001), CPR to extracorporeal cardiopulmonary resuscitation (ECPR) (20 vs. 40, P = 0.001), and collapse-to-ECPR (23 vs. 45, P = 0.001), in the good outcome group compared to the poor outcome group.

CONCLUSION

This study emphasizes the importance of minimizing the time between collapse and CPR/ECMO initiation to improve neurological outcomes and reduce disability in cardiac arrest patients. However, no significant associations were found between outcomes and other demographic or clinical variables in this study. Further research with a larger sample size is needed to validate these findings.

IMPLICATIONS FOR CLINICAL PRACTICE

The study underscores the significance of reducing the time between collapse and the initiation of CPR and ECMO. Shorter time intervals were associated with improved neurological outcomes and reduced disability in cardiac arrest patients.

Extracorporeal vs. conventional CPR for out-of-hospital cardiac arrest: A systematic review and meta-analysis

BACKGROUND

Out-of-hospital cardiac arrest (OHCA) remains a significant cause of mortality and morbidity worldwide. Extracorporeal cardiopulmonary resuscitation (ECPR) is a potential intervention for OHCA, but its effectiveness compared to conventional cardiopulmonary resuscitation (CCPR) needs further evaluation.

METHOD

We systematically searched PubMed, Embase, the Cochrane Library, Web of Science, and ClinicalTrials.gov for relevant studies from January 2010 to March 2023. Pooled meta-analysis was performed to investigate any potential association between ECPR and improved survival and neurological outcomes.

RESULTS

This systematic review and meta-analysis included two randomized controlled trials enrolling 162 participants and 10 observational cohort studies enrolling 4507 participants. The pooled meta-analysis demonstrated that compared to CCRP, ECPR did not improve survival and neurological outcomes at 180 days following OHCA (RR: 3.39, 95% CI: 0.79 to 14.64; RR: 2.35, 95% CI: 0.97 to 5.67). While a beneficial effect of ECPR was obtained regarding 30-day survival and neurological outcomes. Furthermore, ECPR was associated with a higher risk of bleeding complications. Subgroup analysis showed that ECPR was prominently beneficial when exclusively initiated in the emergency department. Additional post-resuscitation treatments did not significantly impact the efficacy of ECPR on 180-day survival with favorable neurological outcomes.

CONCLUSIONS

There is no high-quality evidence supporting the superiority of ECPR over CCPR in terms of survival and neurological outcomes in OHCA patients. However, due to the potential for bias, heterogeneity among studies, and inconsistency in practice, the non-significant results do not preclude the potential benefits of ECPR. Further high-quality research is warranted to optimize ECPR practice and provide more generalizable evidence. Clinical trial registration PROSPERO, https://www.crd.york.ac.uk/prospero/, registry number: CRD42023402211.

Cerebral Autoregulation: A Target for Improving Neurological Outcomes in Extracorporeal Life Support

Despite improvements in survival after illnesses requiring extracorporeal life support, cerebral injury continues to hinder successful outcomes. Cerebral autoregulation (CA) is an innate protective mechanism that maintains constant cerebral blood flow in the face of varying systemic blood pressure. However, it is impaired in certain disease states and, potentially, following initiation of extracorporeal circulatory support. In this review, we first discuss patient-related factors pertaining to venovenous and venoarterial extracorporeal membrane oxygenation (ECMO) and their potential role in CA impairment. Next, we examine factors intrinsic to ECMO that may affect CA, such as cannulation, changes in pulsatility, the inflammatory and adaptive immune response, intracranial hemorrhage, and ischemic stroke, in addition to ECMO management factors, such as oxygenation, ventilation, flow rates, and blood pressure management. We highlight potential mechanisms that lead to disruption of CA in both pediatric and adult populations, the challenges of measuring CA in these patients, and potential associations with neurological outcome. Altogether, we discuss individualized CA monitoring as a potential target for improving neurological outcomes in extracorporeal life support.

Survival, but not the severity of hypoxic-ischemic encephalopathy, is associated with higher mean arterial blood pressure after cardiac arrest: a retrospective cohort study

Background

This study investigates the association between the mean arterial blood pressure (MAP), vasopressor requirement, and severity of hypoxic-ischemic encephalopathy (HIE) after cardiac arrest (CA).

Methods

Between 2008 and 2017, we retrospectively analyzed the MAP 200 h after CA and quantified the vasopressor requirements using the cumulative vasopressor index (CVI). Through a postmortem brain autopsy in non-survivors, the severity of the HIE was histopathologically dichotomized into no/mild and severe HIE. In survivors, we dichotomized the severity of HIE into no/mild cerebral performance category (CPC) 1 and severe HIE (CPC 4). We investigated the regain of consciousness, causes of death, and 5-day survival as hemodynamic confounders.

Results

Among the 350 non-survivors, 117 had histopathologically severe HIE while 233 had no/mild HIE, without differences observed in the MAP (73.1 vs. 72.0 mmHg, pgroup = 0.639). Compared to the non-survivors, 211 patients with CPC 1 and 57 patients with CPC 4 had higher MAP values that showed significant, but clinically non-relevant, MAP differences (81.2 vs. 82.3 mmHg, pgroup < 0.001). The no/mild HIE non-survivors (n = 54), who regained consciousness before death, had higher MAP values compared to those with no/mild HIE (n = 179), who remained persistently comatose (74.7 vs. 69.3 mmHg, pgroup < 0.001). The no/mild HIE non-survivors, who regained consciousness, required fewer vasopressors (CVI 2.1 vs. 3.6, pgroup < 0.001). Independent of the severity of HIE, the survivors were weaned faster from vasopressors (CVI 1.0).

Conclusions

Although a higher MAP was associated with survival in CA patients treated with a vasopressor-supported MAP target above 65 mmHg, the severity of HIE was not. Awakening from coma was associated with less vasopressor requirements. Our results provide no evidence for a MAP target above the current guideline recommendations that can decrease the severity of HIE.

Association of blood pressure with neurologic outcome at hospital discharge after pediatric cardiac arrest resuscitation

BACKGROUND

Poor outcomes are associated with post cardiac arrest blood pressures <5th percentile for age. We aimed to study the relationship of mean arterial pressure (MAP) with favorable neurologic outcome following cardiac arrest and return of spontaneous circulation (ROSC).

METHODS

This retrospective, multi-center, observational study analyzed data from the Pediatric Resuscitation Quality Collaborative (pediRES-Q). Children (<18 years) who achieved ROSC following index in-hospital or out-of-hospital cardiac arrest and survived ≥6 hours were included. Lowest documented MAP within the first 6 hours of ROSC was percentile adjusted for age and categorized into six groups - Group I: <5th, II: 5-24th, III: 25-49th, IV: 50-74th, V: 75-94th; and VI: 95-100th percentile. Primary outcome was favorable neurologic status at hospital discharge, defined as PCPC score 1, 2, or no change from pre-arrest baseline. Multivariable logistic regression was performed to analyze the association of MAP group with favorable outcome, controlling for illness category (surgical-cardiac), initial rhythm (shockable), arrest time (weekend or overnight), age, CPR duration, and clustering by site.

RESULTS

787 patients were included: median [Q1,Q3] age 17.9 [4.8,90.6] months; male 58%; OHCA 21%; shockable rhythm 13%; CPR duration 7 [3,16] min; favorable neurologic outcome 54%. Median lowest documented MAP percentile for the favorable outcome group was 13 [3,43] versus 8 [1,37] for the unfavorable group. The distribution of blood pressures by MAP group was I: 37%, II: 28%, III: 13%, IV: 11%, V: 7%, and VI: 4%. Compared with patients in Group I (<5%ile), Groups II, III, and IV had higher odds of favorable outcome (aOR, 1.84 [95% CI, 1.24, 2.73]; 2.20 [95% CI, 1.32, 3.68]; 1.90 [95% CI, 1.12, 3.25]). There was no association between Groups V or VI and favorable outcome (aOR, 1.44 [95% CI, 0.75, 2.80]; 1.11 [95% CI, 0.47, 2.59]).

CONCLUSION

In the first 6-hours post-ROSC, a lowest documented MAP between the 5th-74th percentile for age was associated with favorable neurologic outcome compared to MAP <5th percentile for age.

Early stroke after left ventricular assist device implantation: role of right heart failure

Background

Both stroke and right heart failure (RHF) are common and serious complications after left ventricular assist device (LVAD) implantation. The objective of this study was to evaluate relation between stroke and RHF early after LVAD implantation.

Methods

This is a retrospective observational cohort study. From January 2012 to December 2020, patients who underwent LVAD implantation in a single-center were enrolled. Patients with a non-dischargeable LVAD or without follow-up data were excluded. Early stroke was defined as a stroke event within 6 months after implantation. Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) definition was used for the diagnosis of RHF.

Results

A total of 70 patients underwent LVAD implantation. Sixty-seven patients (95.7%) were successfully discharged and 16 patients (22.9%) died during follow-up. 14 patients (20.0%) experienced a stroke within 6 months after implantation, and 0.28 stroke events per patient-year occurred during follow-up. Postoperative RHF was more common in the stroke group (64.3% vs. 23.2%, P=0.008) and the median time from implantation to RHF was 1 day. In the Cox multivariable analysis, postoperative RHF [hazard ratio (HR): 5.063; 95% confidence interval (CI): 1.682-15.245; P=0.004], and cerebral perfusion pressure (CPP) on postoperative day (POD) 1 (HR: 0.923; 95% CI: 0.858-0.992; P=0.030) were independent predictors for early stroke. A CPP of 62 mmHg (sensitivity, 71.4%; specificity, 59.3%) was the cutoff value for early stroke according to the receiver operating characteristic (ROC) analysis.

Conclusions

RHF after LVAD implantation may be a risk factor for early stroke. Prevention and management of postoperative RHF with adequate CPP could prevent early stroke after LVAD implantation.

Neuroprotective-Neurorestorative Effects Induced by Progesterone on Global Cerebral Ischemia: A Narrative Review

Progesterone (P4) is a neuroactive hormone having pleiotropic effects, supporting its pharmacological potential to treat global (cardiac-arrest-related) cerebral ischemia, a condition associated with an elevated risk of dementia. This review examines the current biochemical, morphological, and functional evidence showing the neuroprotective/neurorestorative effects of P4 against global cerebral ischemia (GCI). Experimental findings show that P4 may counteract pathophysiological mechanisms and/or regulate endogenous mechanisms of plasticity induced by GCI. According to this, P4 treatment consistently improves the performance of cognitive functions, such as learning and memory, impaired by GCI. This functional recovery is related to the significant morphological preservation of brain structures vulnerable to ischemia when the hormone is administered before and/or after a moderate ischemic episode; and with long-term adaptive plastic restoration processes of altered brain morphology when treatment is given after an episode of severe ischemia. The insights presented here may be a guide for future basic research, including the study of P4 administration schemes that focus on promoting its post-ischemia neurorestorative effect. Furthermore, considering that functional recovery is a desired endpoint of pharmacological strategies in the clinic, they could support the study of P4 treatment for decreasing dementia in patients who have suffered an episode of GCI.

Association between time-dependent changes in cerebrovascular autoregulation after cardiac arrest and outcomes: A prospective cohort study

This prospective observational single-center cohort study aimed to determine an association between cerebrovascular autoregulation (CVAR) and outcomes in hypoxic-ischemic brain injury post-cardiac arrest (CA), and assessed 100 consecutive post-CA patients in Japan between June 2017 and May 2020 who experienced a return of spontaneous circulation. Continuous monitoring was performed for 96 h to determine CVAR presence. A moving Pearson correlation coefficient was calculated from the mean arterial pressure and cerebral regional oxygen saturation. The association between CVAR and outcomes was evaluated using the Cox proportional hazard model; non-CVAR time percent was the time-dependent, age-adjusted covariate. The non-linear effect of target temperature management (TTM) was assessed using a restricted cubic spline. Of the 100 participants, CVAR was detected using the cerebral performance category (CPC) in all patients with a good neurological outcome (CPC 1-2) and in 65 patients (88%) with a poor outcome (CPC 3-5). Survival probability decreased significantly with increasing non-CVAR time percent. The TTM versus the non-TTM group had a significantly lower probability of a poor neurological outcome at 6 months with a non-CVAR time of 18%-37% (p < 0.05). Longer non-CVAR time may be associated with significantly increased mortality in hypoxic-ischemic brain injury post-CA.

Cerebral hemodynamics after cardiac arrest: implications for clinical management

Following resuscitation from cardiac arrest, hypoxic ischemic brain injury (HIBI) ensues, which is the primary determinant of adverse outcome. The pathophysiology of HIBI can be compartmentalized into primary and secondary injury, resulting from cerebral ischemia during cardiac arrest and reperfusion following successful resuscitation, respectively. During the secondary injury phase, increased attention has been directed towards the optimization of cerebral oxygen delivery to prevent additive injury to the brain. During this phase, cerebral hemodynamics are characterized by early hyperemia following resuscitation and then a protracted phase of cerebral hypoperfusion termed "no-reflow" during which additional hypoxic-ischemic injury can occur. As such, identification of therapeutic strategies to optimize cerebral delivery of oxygen is at the forefront of HIBI research. Unfortunately, randomized control trials investigating the manipulation of arterial carbon dioxide tension and mean arterial pressure augmentation as methods to potentially improve cerebral oxygen delivery have shown no impact on clinical outcomes. Emerging literature suggests differential patient-specific phenotypes may exist in patients with HIBI. The potential to personalize therapeutic strategies in the critical care setting based upon patient-specific pathophysiology presents an attractive strategy to improve HIBI outcomes. Herein, we review the cerebral hemodynamic pathophysiology of HIBI, discuss patient phenotypes as it pertains to personalizing care, as well as suggest future directions.

EFFECTS OF M101-AN EXTRACELLULAR HEMOGLOBIN-APPLIED DURING CARDIOPULMONARY RESUSCITATION: AN EXPERIMENTAL RODENT STUDY

ABSTRACT

During and immediately after cardiac arrest, cerebral oxygen delivery is impaired mainly by microthrombi and cerebral vasoconstriction. This may narrow capillaries so much that it might impede the flow of red blood cells and thus oxygen transport. The aim of this proof-of-concept study was to evaluate the effect of M101, an extracellular hemoglobin-based oxygen carrier (Hemarina SA, Morlaix, France) derived from Arenicola marina , applied during cardiac arrest in a rodent model, on markers of brain inflammation, brain damage, and regional cerebral oxygen saturation. Twenty-seven Wistar rats subjected to 6 min of asystolic cardiac arrest were infused M101 (300 mg/kg) or placebo (NaCl 0.9%) concomitantly with start of cardiopulmonary resuscitation. Brain oxygenation and five biomarkers of inflammation and brain damage (from blood, cerebrospinal fluid, and homogenates from four brain regions) were measured 8 h after return of spontaneous circulation. In these 21 different measurements, M101-treated animals were not significantly different from controls except for phospho-tau only in single cerebellum regions ( P = 0.048; ANOVA of all brain regions: P = 0.004). Arterial blood pressure increased significantly only at 4 to 8 min after return of spontaneous circulation ( P < 0.001) and acidosis decreased ( P = 0.009). While M101 applied during cardiac arrest did not significantly change inflammation or brain oxygenation, the data suggest cerebral damage reduction due to hypoxic brain injury, measured by phospho-tau. Global burden of ischemia appeared reduced because acidosis was less severe. Whether postcardiac arrest infusion of M101 improves brain oxygenation is unknown and needs to be investigated.

Association of Arterial Spin Labeling Parameters With Cognitive Decline, Vascular Events, and Mortality in a Memory-Clinic Sample

BACKGROUND

Cognitive decline in older adults has been attributed to reduced cerebral blood flow (CBF). Recently, the spatial coefficient of variation (sCoV) of ASL has been proposed as a proxy marker of cerebrovascular insufficiency. We investigated the association between baseline ASL parameters with cognitive decline, incident cerebrovascular disease, and risk of vascular events and mortality.

DESIGN, SETTING, AND PARTICIPANTS

About 368 memory-clinic patients underwent three-annual neuropsychological assessments and brain MRI scans at baseline and follow-up. MRIs were graded for white matter hyperintensities (WMH), lacunes, cerebral microbleeds (CMBs), cortical infarcts, and intracranial stenosis. Baseline gray (GM) and white matter (WM) CBF and GM-sCoV were obtained with ExploreASL from 2D-EPI pseudo-continuous ASL images. Cognitive assessment was done using a validated neuropsychological battery. Data on incident vascular events (heart disease, stroke, transient ischemic attack) and mortality were obtained.

RESULTS

Higher baseline GM-sCoV was associated with decline in the memory domain over 3 years of follow-up. Furthermore, higher GM-sCoV was associated with a decline in the memory domain only in participants without dementia. Higher baseline GM-sCoV was associated with progression of WMH and incident CMBs. During a mean follow-up of 3 years, 29 (7.8%) participants developed vascular events and 18 (4.8%) died. Participants with higher baseline mean GM-sCoV were at increased risk of vascular events.

CONCLUSIONS

Higher baseline GM-sCoV of ASL was associated with a decline in memory and risk of cerebrovascular disease and vascular events, suggesting that cerebrovascular insufficiency may contribute to accelerated cognitive decline and worse clinical outcomes in memory clinic participants.

Targeted Temperature Management in Postresuscitation Care After Incorporating Results of the TTM2 Trial

Cardiac arrest still accounts for a substantial proportion of cardiovascular related deaths and is associated with a tremendous risk of neurological injury and, among the few survivors, poor quality of life. Critical determinants of survival and long‐term functional status after cardiac arrest are timely initiation of cardiopulmonary resuscitation and use of an external defibrillator for patients with a shockable rhythm. Outcomes are still far from satisfactory, despite ongoing efforts to improve cardiac arrest response systems, as well as elaborate postresuscitation algorithms. Targeted temperature management at the wide range between 32 °C and 36 °C has been one of the main therapeutic strategies to improve neurological outcome in postresuscitation care. This recommendation has been mainly based on 2 small randomized trials that were published 20 years ago. Most recent data derived from the TTM2 (Targeted Hypothermia Versus Targeted Normothermia After Out‐of‐Hospital Cardiac Arrest) trial, which included 1861 patients, challenge this strategy. It showed no benefit of targeted hypothermia at 33 °C over normothermia at 36 °C to 37.5 °C with fever prevention. Because temperature management at lower temperatures also correlated with an increased risk of side effects without any benefit in the TTM2 trial, a modification of the guidelines with harmonizing temperature management to normothermia might be necessary.

Characterization of cerebral blood flow during open cardiac massage in swine: Effect of volume status

Introduction: Patients in cardiac arrest treated with resuscitative thoracotomy and open cardiac massage (OCM) have high rates of mortality with poor neurological outcomes. The aim of this study is to quantitate cerebral perfusion during OCM using computed tomography perfusion (CTP) imaging in a swine model of normo- and hypovolemia.

Methods: Anesthetized swine underwent instrumentation with right atrial and aortic pressure catheters. A catheter placed in the ascending aorta was used to administer iodinated contrast and CTP imaging acquired. Cerebral blood flow (CBF; ml/100 g of brain) and time to peak (TTP; s) were measured. Animals were then euthanized by exsanguination (hypovolemic group) or potassium chloride injection (normovolemic group) and subjected to a clamshell thoracotomy, aortic cross clamping, OCM, and repeated CTP. Data pertaining to peak coronary perfusion pressure (pCoPP; mmHg) were collected and % CoPP > 15 mmHg (% CoPP; s) calculated post hoc.

Results: Normovolemic animals (n = 5) achieved superior pCoPP compared to the hypovolemic animals (n = 5) pCoPP (39.3 vs. 12.3, p < 0.001) and % CoPP (14.5 ± 1.9 vs. 30.9 ± 6.5, p < 0.001). CTP acquisition was successful and TTP elongated from spontaneous circulation, normovolemia to hypovolemia (5.7 vs. 10.8 vs. 14.8, p = 0.01). CBF during OCM was similar between hypovolemic and normovolemic groups (7.5 ± 8.1 vs. 4.9 ± 6.0, p = 0.73) which was significantly lower than baseline values (51.9 ± 12.1, p < 0.001).

Conclusion: OCM in normovolemia generates superior coronary hemodynamics compared to hypovolemia. Despite this, neither generates adequate CBF as measured by CTP, compared to baseline. To improve the rate of neurologically intact survivors, novel resuscitative techniques need to be investigated that specifically target cerebral perfusion as existing techniques are inadequate.

Optimal bispectral index level of sedation and cerebral oximetry in traumatic brain injury: a non-invasive individualized approach in critical care?

Background

Impaired cerebral autoregulation has been linked with worse outcomes, with literature suggesting that current therapy guidelines fail to significantly impact cerebrovascular reactivity. The cerebral oximetry index (COx_a) is a surrogate measure of cerebrovascular reactivity which can in theory be obtained non-invasively using regional brain tissue oxygen saturation and arterial blood pressure. The goal of this study was to assess the relationship between objectively measured depth of sedation through BIS and autoregulatory capacity measured through COx_a.

Methods

In a prospectively maintained observational study, we collected continuous regional brain tissue oxygen saturation, intracranial pressure, arterial blood pressure and BIS in traumatic brain injury patients. COx_a was obtained using the Pearson’s correlation between regional brain tissue oxygen saturation and arterial blood pressure and ranges from − 1 to 1 with higher values indicating impairment of cerebrovascular reactivity. Using BIS values and COx_a, a curve-fitting method was applied to determine the minimum value for the COx_a. The associated BIS value with the minimum COx_a is called BISopt. This BISopt was both visually and algorithmically determined, which were compared and assessed over the whole dataset.

Results

Of the 42 patients, we observed that most had a parabolic relationship between BIS and COx_a. This suggests a potential “optimal” depth of sedation where COx_a is the most intact. Furthermore, when comparing the BISopt algorithm with visual inspection of BISopt, we obtained similar results. Finally, BISopt % yield (determined algorithmically) appeared to be independent from any individual sedative or vasopressor agent, and there was agreement between BISopt found with COx_a and the pressure reactivity index (another surrogate for cerebrovascular reactivity).

Conclusions

This study suggests that COx_a is capable of detecting disruption in cerebrovascular reactivity which occurs with over-/under-sedation, utilizing a non-invasive measure of determination and assessment. This technique may carry implications for tailoring sedation in patients, focusing on individualized neuroprotection.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40635-022-00460-9.

An apoptosis inhibitor suppresses microglial and astrocytic activation after cardiac ischemia/reperfusion injury

OBJECTIVE

Microglial hyperactivation and apoptosis were observed following myocardial infarction and ischemia reperfusion (I/R) injury. This study aimed to test the hypothesis that the apoptosis inhibitor, Z-VAD, attenuates microglial and astrocytic hyperactivation and brain inflammation in rats with cardiac I/R injury.

MATERIALS AND METHODS

Rats were subjected to either sham or cardiac I/R operation (30 min-ischemia followed by 120-min reperfusion), rats in the cardiac I/R group were given either normal saline solution or Z-VAD at 3.3 mg/kg via intravenous injection 15 min prior to cardiac ischemia. Left ventricular ejection fraction (% LVEF) was determined during the cardiac I/R protocol. The brain tissues were removed and used to determine brain apoptosis, brain inflammation, microglial and astrocyte morphology.

RESULTS

Cardiac dysfunction was observed in rats with cardiac I/R injury as indicated by decreased %LVEF. In the brain, we found brain apoptosis, brain inflammation, microglia hyperactivation, and reactive astrogliosis occurred following cardiac I/R injury. Pretreatment with Z-VAD effectively increased %LVEF, reduced brain apoptosis, attenuated brain inflammation by decreasing IL-1β mRNA levels, suppressed microglial and astrocytic hyperactivation and proliferation after cardiac I/R injury.

CONCLUSION

Z-VAD exerts neuroprotective effects against cardiac I/R injury not only targeting apoptosis but also microglial and astrocyte activation.

Cerebral Blood Flow Hemispheric Asymmetry in Comatose Adults Receiving Extracorporeal Membrane Oxygenation

Peripheral veno-arterial extracorporeal membrane oxygenation (ECMO) artificially oxygenates and circulates blood retrograde from the femoral artery, potentially exposing the brain to asymmetric perfusion. Though ECMO patients frequently experience brain injury, neurologic exams and imaging are difficult to obtain. Diffuse correlation spectroscopy (DCS) non-invasively measures relative cerebral blood flow (rBF) at the bedside using an optical probe on each side of the forehead. In this study we observed interhemispheric rBF differences in response to mean arterial pressure (MAP) changes in adult ECMO recipients. We recruited 13 subjects aged 21–78 years (7 with cardiac arrest, 4 with acute heart failure, and 2 with acute respiratory distress syndrome). They were dichotomized via Glasgow Coma Scale Motor score (GCS-M) into comatose (GCS-M ≤ 4; n = 4) and non-comatose (GCS-M > 4; n = 9) groups. Comatose patients had greater interhemispheric rBF asymmetry (ASYM_rBF) vs. non-comatose patients over a range of MAP values (29 vs. 11%, p = 0.009). ASYM_rBF in comatose patients resolved near a MAP range of 70–80 mmHg, while rBF remained symmetric through a wider MAP range in non-comatose patients. Correlations between post-oxygenator pCO₂ or pH vs. ASYM_rBF were significantly different between comatose and non-comatose groups. Our findings indicate that comatose patients are more likely to have asymmetric cerebral perfusion.

Metformin-mediated mitochondrial protection post-cardiac arrest improves EEG activity and confers neuroprotection and survival benefit

Cardiac arrest (CA) produces global ischemia/reperfusion injury resulting in substantial multiorgan damage. There are limited efficacious therapies to save lives despite CA being such a lethal disease process. The small population of surviving patients suffer extensive brain damage that results in substantial morbidity. Mitochondrial dysfunction in most organs after CA has been implicated as a major source of injury. Metformin, a first-line treatment for diabetes, has shown promising results in the treatment for other diseases and is known to interact with the mitochondria. For the treatment of CA, prior studies have utilized metformin in a preconditioning manner such that animals are given metformin well before undergoing CA. As the timing of CA is quite difficult to predict, the present study, in a clinically relevant manner, sought to evaluate the therapeutic benefits of metformin administration immediately after resuscitation using a 10 min asphxyial-CA rat model. This is the first study to show that metformin treatment post-CA (a) improves 72 h survival and neurologic function, (b) protects mitochondrial function with a reduction in apoptotic brain injury without activating AMPK, and (c) potentiates earlier normalization of brain electrophysiologic activity. Overall, as an effective and safe drug, metformin has the potential to be an easily translatable intervention for improving survival and preventing brain damage after CA.

Individualized cerebral perfusion pressure in acute neurological injury: are we ready for clinical use?

PURPOSE OF REVIEW

Individualizing cerebral perfusion pressure based on cerebrovascular autoregulation assessment is a promising concept for neurological injuries where autoregulation is typically impaired. The purpose of this review is to describe the status quo of autoregulation-guided protocols and discuss steps towards clinical use.

RECENT FINDINGS

Retrospective studies have indicated an association of impaired autoregulation and poor clinical outcome in traumatic brain injury (TBI), hypoxic-ischemic brain injury (HIBI) and aneurysmal subarachnoid hemorrhage (aSAH). The feasibility and safety to target a cerebral perfusion pressure optimal for cerebral autoregulation (CPPopt) after TBI was recently assessed by the COGITATE trial. Similarly, the feasibility to calculate a MAP target (MAPopt) based on near-infrared spectroscopy was demonstrated for HIBI. Failure to meet CPPopt is associated with the occurrence of delayed cerebral ischemia in aSAH but interventional trials in this population are lacking. No level I evidence is available on potential effects of autoregulation-guided protocols on clinical outcomes.

SUMMARY

The effect of autoregulation-guided management on patient outcomes must still be demonstrated in prospective, randomized, controlled trials. Selection of disease-specific protocols and endpoints may serve to evaluate the overall benefit from such approaches.

Cervical Vagus Nerve Stimulation Improves Neurologic Outcome After Cardiac Arrest in Mice by Attenuating Oxidative Stress and Excessive Autophagy

BACKGROUND

Cerebral ischemia and reperfusion (I/R) induces oxidative stress and activates autophagy, leading to brain injury and neurologic deficits. Cervical vagus nerve stimulation (VNS) increases cerebral blood flow (CBF). In this study, we investigate the effect of VNS-induced CBF increase on neurologic outcomes after cardiac arrest (CA).

MATERIALS AND METHODS

A total of 40 male C57Bl/6 mice were subjected to ten minutes of asphyxia CA and randomized to vagus nerve isolation (VNI) or VNS treatment group. Eight mice received sham surgery and VNI. Immediately after resuscitation, 20 minutes of electrical stimulation (1 mA, 1 ms, and 10 Hz) was started in the VNS group. Electrocardiogram, blood pressure, and CBF were monitored. Neurologic and histologic outcomes were evaluated at 72 hours. Oxidative stress and autophagy were assessed at 3 hours and 24 hours after CA.

RESULTS

Baseline characteristics were not different among groups. VNS mice had better behavioral performance (ie, open field, rotarod, and neurologic score) and less neuronal death (p < 0.05, vs VNI) in the hippocampus. CBF was significantly increased in VNS-treated mice at 20 minutes after return of spontaneous circulation (ROSC) (p < 0.05). Furthermore, levels of 8-hydroxy-2'-deoxyguanosine in the blood and autophagy-related proteins (ie, LC-3Ⅱ/Ⅰ, Beclin-1, and p62) in the brain were significantly decreased in VNS mice. Aconitase activity was also reduced, and the p-mTOR/mTOR ratio was increased in VNS mice.

CONCLUSIONS

Oxidative stress induced by global brain I/R following CA/ROSC leads to early excessive autophagy and impaired autophagic flux. VNS promoted CBF recovery, ameliorating these changes. Neurologic and histologic outcomes were also improved.

Monitoring of cerebrovascular pressure reactivity in children may predict neurologic outcome after hypoxic-ischemic brain injury

OBJECTIVES

Impaired cerebral blood flow is a first-line reason of ischemic-hypoxic brain injury in children. The principal goal of intensive care management is to detect and prevent further cerebral blood flow deficits. This can be achieved by actively managing cerebral perfusion pressure (CPP) using input from cerebrovascular autoregulation (CAR). The main objective of the current study was to investigate CAR after cardiac arrest in children.

METHODS

Nineteen consecutive children younger than 18 years after cardiopulmonary resuscitation, in whom intracranial pressure (ICP) was continuously measured, were included. Blood pressure and ICP were continuously monitored via ICM + software and actively managed using the pressure reactivity index (PRx) to achieve and maintain an optimal CPP. Outcome was scored using the extended Glasgow outcome scale (eGOS) at discharge and 6 months.

RESULTS

Eight children died in hospital. At 6 months, further 4 children had an unfavorable (eGOS1-4) and 7 a favorable (eGOS5-8) outcome. Over the entire monitoring period, we found an elevated ICP (24.5 vs 7.4 mmHg), a lower CPP (50.3 vs 66.2 mmHg) and a higher PRx (0.24 vs - 0.01), indicating impaired CAR, in patients with unfavorable outcome. The dose of impaired autoregulation was significantly higher in unfavorable outcome (54.6 vs 29.3%). Analyzing only the first 72 h after cardiac arrest, ICP ≥ 10 mmHg and PRx > 0.2 correlated to unfavorable outcome.

CONCLUSIONS

Significant doses of impaired CAR within 72 h after resuscitation are associated with unfavorable outcome. The inability to restore autoregulation despite active attempts to do so as well as an elevated ICP may serve as a bad prognostic sign indicating a severe initial hypoxic-ischemic brain injury.

Cerebral perfusion and metabolism with mean arterial pressure 90 vs. 60 mmHg in a porcine post cardiac arrest model with and without targeted temperature management

AIM

To determine whether targeting a mean arterial pressure of 90 mmHg (MAP90) would yield improved cerebral blood flow and less ischaemia compared to MAP 60 mmHg (MAP60) with and without targeted temperature management at 33 °C (TTM33) in a porcine post-cardiac arrest model.

METHODS

After 10 min of cardiac arrest, 41 swine of either sex were resuscitated until return of spontaneous circulation (ROSC). They were randomised to TTM33 or no-TTM, and MAP60 or MAP90; yielding four groups. Temperatures were managed with intravasal cooling and blood pressure targets with noradrenaline, vasopressin and nitroprusside, as appropriate. After 30 min of stabilisation, animals were observed for two hours. Cerebral perfusion pressure (CPP), cerebral blood flow (CBF), pressure reactivity index (PRx), brain tissue pCO2 (PbtCO2) and tissue intermediary metabolites were measured continuously and compared using mixed models.

RESULTS

Animals randomised to MAP90 had higher CPP (p < 0.001 for both no-TTM and TTM33) and CBF (no-TTM, p < 0.03; TH, p < 0.001) compared to MAP60 during the 150 min observational period post-ROSC. We also observed higher lactate and pyruvate in MAP60 irrespective of temperature, but no significant differences in PbtCO2 and lactate/pyruvate-ratio. We found lower PRx (indicating more intact autoregulation) in MAP90 vs. MAP60 (no-TTM, p = 0.04; TTM33, p = 0.03).

CONCLUSION

In this porcine cardiac arrest model, targeting MAP90 led to better cerebral perfusion and more intact autoregulation, but without clear differences in ischaemic markers, compared to MAP60.

INSTITUTIONAL PROTOCOL NUMBER

FOTS, id 8442.

Increased cerebral endothelium-dependent vasodilation in rats in the postcardiac arrest period

Cardiovascular lability is common after cardiac arrest. We investigated whether altered endothelial function is present in cerebral and mesenteric arteries 2 and 4 h after resuscitation. Male Sprague-Dawley rats were anesthetized, intubated, ventilated, and intravascularly catheterized whereupon rats were randomized into four groups. Following 7 min of asphyxial cardiac arrest and subsequent resuscitation, cardiac arrest and sham rats were observed for either 2 or 4 h. Neuron-specific enolase levels were measured in blood samples. Middle cerebral artery segments and small mesenteric arteries were isolated and examined in microvascular myographs. qPCR and immunofluorescence analysis were performed on cerebral arteries. In cerebral arteries, bradykinin-induced vasodilation was inhibited in the presence of either calcium-activated K⁺ channel blockers (UCL1684 and senicapoc) or the nitric oxide (NO) synthase inhibitor, N^ω-nitro-L-arginine methyl ester hydrochloride (l-NAME), whereas the combination abolished bradykinin-induced vasodilation across groups. Neuron-specific enolase levels were significantly increased in cardiac arrest rats. Cerebral vasodilation was comparable between the 2-h groups, but markedly enhanced in response to bradykinin, NS309 (an opener of small and intermediate calcium-activated K⁺ channels), and sodium nitroprusside 4 h after cardiac arrest. Endothelial NO synthase and guanylyl cyclase subunit α-1 mRNA expression was unaltered after 2 h, but significantly decreased 4 h after resuscitation. In mesenteric arteries, the endothelium-dependent vasodilation was comparable between corresponding groups at both 2 and 4 h. Our findings show enhanced cerebral endothelium-dependent vasodilation 4 h after cardiac arrest mediated by potentiated endothelial-derived hyperpolarization and NO pathways. Altered cerebral endothelium-dependent vasodilation may contribute to disturbed cerebral perfusion after cardiac arrest.NEW & NOTEWORTHY This is the first study, to our knowledge, to demonstrate enhanced endothelium-dependent vasodilation in middle cerebral arteries in a cardiac arrest rat model. The increased endothelium-dependent vasodilation was a result of potentiated endothelium-derived hyperpolarization and endothelial nitric oxide pathways. Immunofluorescence microscopy confirmed the presence of relevant receptors and eNOS in cerebral arteries, whereas qPCR showed altered expression of genes related to guanylyl cyclase and eNOS. Altered endothelium-dependent vasoregulation may contribute to disturbed cerebral blood flow in the postcardiac arrest period.

Association of deranged cerebrovascular reactivity with brain injury following cardiac arrest: a post-hoc analysis of the COMACARE trial

BACKGROUND

Impaired cerebrovascular reactivity (CVR) is one feature of post cardiac arrest encephalopathy. We studied the incidence and features of CVR by near infrared spectroscopy (NIRS) and associations with outcome and biomarkers of brain injury.

METHODS

A post-hoc analysis of 120 comatose OHCA patients continuously monitored with NIRS and randomised to low- or high-normal oxygen, carbon dioxide and mean arterial blood pressure (MAP) targets for 48 h. The tissue oximetry index (TO_x) generated by the moving correlation coefficient between cerebral tissue oxygenation measured by NIRS and MAP was used as a dynamic index of CVR with TO_x > 0 indicating impaired reactivity and TO_x > 0.3 used to delineate the lower and upper MAP bounds for disrupted CVR. TO_x was analysed in the 0-12, 12-24, 24-48 h time-periods and integrated over 0-48 h. The primary outcome was the association between TO_x and six-month functional outcome dichotomised by the cerebral performance category (CPC1-2 good vs. 3-5 poor). Secondary outcomes included associations with MAP bounds for CVR and biomarkers of brain injury.

RESULTS

In 108 patients with sufficient data to calculate TO_x, 76 patients (70%) had impaired CVR and among these, chronic hypertension was more common (58% vs. 31%, p = 0.002). Integrated TO_x for 0-48 h was higher in patients with poor outcome than in patients with good outcome (0.89 95% CI [- 1.17 to 2.94] vs. - 2.71 95% CI [- 4.16 to - 1.26], p = 0.05). Patients with poor outcomes had a decreased upper MAP bound of CVR over time (p = 0.001), including the high-normal oxygen (p = 0.002), carbon dioxide (p = 0.012) and MAP (p = 0.001) groups. The MAP range of maintained CVR was narrower in all time intervals and intervention groups (p < 0.05). NfL concentrations were higher in patients with impaired CVR compared to those with intact CVR (43 IQR [15-650] vs 20 IQR [13-199] pg/ml, p = 0.042).

CONCLUSION

Impaired CVR over 48 h was more common in patients with chronic hypertension and associated with poor outcome. Decreased upper MAP bound and a narrower MAP range for maintained CVR were associated with poor outcome and more severe brain injury assessed with NfL. Trial registration ClinicalTrials.gov, NCT02698917 .

Trans-Ocular Brain Impedance Indices Predict Pressure Reactivity Index Changes in a Porcine Model of Hypotension and Cerebral Autoregulation Perturbation

BACKGROUND

Cerebrovascular autoregulation (CA) is a protective mechanism that enables the cerebral vasculature to automodulate tone in response to changes in cerebral perfusion pressure to ensure constant levels of cerebral blood flow (CBF) and oxygen delivery. CA can be impaired after neurological injury and contributes to secondary brain injury. In this study, we report novel impedance indices using trans-ocular brain impedance (TOBI) during controlled systemic hemorrhage and hypotension to assess CA in comparison with pressure reactivity index (PRx).

METHODS

Yorkshire swine were instrumented to record intracranial pressure (ICP), mean arterial pressure (MAP), and CBF. TOBI was recorded using electrocardiographic electrodes placed on the closed eyelids. Impedance changes (dz) were recorded in response to introducing an alternating current (0.4 mA) through the electrodes. MAP, ICP, and CBF were also measured. Animals were subjected to a controlled hemorrhage to remove 30-40% of each animal's total blood volume over 25-35 min. Hemorrhage was titrated to reach an MAP of approximately 35 mm Hg and end-tidal carbon dioxide above 28 mm Hg. PRx was calculated as a moving Pearson correlation between MAP and ICP. TOBI indices were calculated as the amplitude of the respiratory-induced changes in dz. DZx was calculated as a moving Pearson correlation between dz and MAP. TOBI indices (dz and DZx) were compared with hemodynamic indicators and PRx.

RESULTS

dz was shown to be highly correlated with MAP, ICP, cerebral perfusion pressure, and CBF (r =  - 0.823, - 0.723, - 0.813, and - 0.726), respectively (p < 0.0001). During hemorrhage, cerebral perfusion pressure and CBF had a mean percent decrease (standard deviation) from baseline of - 54.2% (12.5%) and - 28.3% (14.7%), respectively, whereas dz increased by 277% (268%). Receiver operator characteristics and precision-recall curves demonstrated high predictive performance of DZx when compared with PRx with an area under the curve above 0.82 and 0.89 for receiver operator characteristic and precision-recall curves, respectively, with high sensitivity and positive predictive power.

CONCLUSIONS

TOBI indices appear to track changes in PRx and hemodynamics that affect CA during hemorrhage-induced hypotension. TOBI may offer a suitable, less invasive surrogate to PRx for monitoring and assessing CA.

Prehospital, post-ROSC blood pressure and associated neurologic outcome

OBJECTIVE

To investigate the relationship between hypotension and neurologic outcome in adults with return of spontaneous circulation after out-of-hospital cardiac arrest.

METHODS

Blood pressure and medication data were extracted from adult patients who had ROSC after OHCA in Alameda County and matched with neurologic outcome using the CARES database from January 1, 2018 through July 1, 2019. We used univariate logistic regression with p ≤ 0.2 followed by multivariate logistic regression and reported an odds ratio with 95% confidence intervals.

RESULTS

Among the 781 adult patients who had ROSC after OHCA, 107 (13.7%) were noted to be hypotensive and 61 (57% of the hypotensive group) received vasopressors. Patients with a final prehospital blood pressure recording of <90 mmHg were more likely to have a poor neurologic outcome (adjusted odds ratio 2.13, adj p = 0.048). About twice as many patients who were not hypotensive had a good neurologic outcome compared to hypotensive patients who had a good neurologic outcome (23% to 10.3%). Additionally, patients who were hypotensive and did not receive vasopressors had a similar neurologic outcome compared to patients who did receive vasopressors.

CONCLUSION

Prehospital post-ROSC hypotension was associated with worse neurologic outcome and giving hypotensive patients vasopressors may not improve neurologic outcome in the prehospital setting.

Pharmacological Approach for Neuroprotection After Cardiac Arrest-A Narrative Review of Current Therapies and Future Neuroprotective Cocktail

Cardiac arrest (CA) results in global ischemia-reperfusion injury damaging tissues in the whole body. The landscape of therapeutic interventions in resuscitation medicine has evolved from focusing solely on achieving return of circulation to now exploring options to mitigate brain injury and preserve brain function after CA. CA pathology includes mitochondrial damage and endoplasmic reticulum stress response, increased generation of reactive oxygen species, neuroinflammation, and neuronal excitotoxic death. Current non-pharmacologic therapies, such as therapeutic hypothermia and extracorporeal cardiopulmonary resuscitation, have shown benefits in protecting against ischemic brain injury and improving neurological outcomes post-CA, yet their application is difficult to institute ubiquitously. The current preclinical pharmacopeia to address CA and the resulting brain injury utilizes drugs that often target singular pathways and have been difficult to translate from the bench to the clinic. Furthermore, the limited combination therapies that have been attempted have shown mixed effects in conferring neuroprotection and improving survival post-CA. The global scale of CA damage and its resultant brain injury necessitates the future of CA interventions to simultaneously target multiple pathways and alleviate the hemodynamic, mitochondrial, metabolic, oxidative, and inflammatory processes in the brain. This narrative review seeks to highlight the current field of post-CA neuroprotective pharmaceutical therapies, both singular and combination, and discuss the use of an extensive multi-drug cocktail therapy as a novel approach to treat CA-mediated dysregulation of multiple pathways, enhancing survival, and neuroprotection.

Cannulation strategies in type A aortic dissection: a novel insight narrative review

This review highlights vital details that can be easily overlooked and discuss how to identify and fix failed cannulation from another novel insight. Appropriate arterial cannulation strategy during cardiopulmonary bypass (CPB) in Stanford type A aortic dissection (AAD) is highly necessary to reach satisfactory perfusion effects and appreciable clinical outcomes. Despite several previously published reviews on cannulation strategies in AAD, most focus on the advantages and disadvantages by comparing various cannulation strategies. In fact, most of evidence came from retrospective studies. More importantly, however, some important details and novel approaches maybe overlooked due to variety reasons. These overlooked details also make sense in clinical practice. Papers related to cannulation refer to type AAD were retrieved and analyzed from the PubMed and Medline database. The key words such as “aortic dissection”, “cannula”, “cannulation”, “cannulation strategy”, “cerebral perfusion”, “type I aortic dissection” were conducted and analyzed. In addition, we looked at some new and very significant specific perfusion techniques such as anterograde cerebral perfusion combined with retrograde inferior vena caval perfusion (RIVP) and reperfusion via the right carotid artery before surgery. The arterial cannulation site and strategy should be determined individually. Monitoring measures are very necessary in the whole procedure.

Comparison of femoral and carotid arteries in terms of pulse check in cardiopulmonary resuscitation: A prospective observational study

BACKGROUND

There is no gold standard pulse localisation for pulse check in cardiopulmonary resuscitation.

AIM

To compare the femoral and carotid arteries in terms of pulse check in cardiopulmonary resuscitation and recommend the most appropriate pulse localisation in advanced life support guidelines and cardiopulmonary resuscitation training programmes.

MATERIALS AND METHODS

We prospectively conducted the study with patients who developed non-traumatic cardiopulmonary arrest between September 2018 and March 2019. The pulse check team was established and divided into two groups, A and B. Both carotid and femoral arteries were checked simultaneously for pulse by members of groups A and B, with the groups alternating between sites to avoid bias. We used some criteria to make pulse detection more effective. These were ETCO2, rhythm and cardiac ultrasonography.

RESULTS

We evaluated 1289 pulse checks in 102 patients. As a result of the statistical analysis with manual palpations and pulses criteria, which we used to detected the presence of a pulse in CPR, we found that the sensitivity of the carotid artery was significantly higher than that of the femoral artery (p = 0.017), with almost identical specificities.

CONCLUSION

The carotid artery should be recommended as the gold standard localisation for pulse checks in cardiopulmonary resuscitation in CPR training programmes and ACLS guidelines.

Impaired Autoregulation Following Resuscitation Correlates with Outcome in Pediatric Patients: A Pilot Study

In children with a traumatic brain injury, the duration of autoregulation impairment correlates with the neurological outcome. This pilot study explored whether a similar relation exists in nontraumatic hypoxic-ischemic brain injury following resuscitation.We investigated 11 children after resuscitation. Blood pressure and intracranial pressure (ICP) were monitored with ICM+ software and actively managed to maintain optimal cerebral perfusion pressure (CPP), using the pressure reactivity index (PRx). Outcomes were scored according to the Glasgow Outcome Scale.Three children died within 24 h. Three survivors had an unfavorable outcome and five had a favorable outcome. In the first 72 h, ICP and CPP values did not differ between, or predict, children with favorable or unfavorable outcomes. The duration of a PRx value ≥0.2 was significantly greater in children with an unfavorable outcome. A PRx value ≤0 was associated with a favorable outcome in all except one child. Children with an unfavorable outcome had areas of ischemic brain tissue on magnetic resonance imaging.The duration of poor autoregulation within the first 72 h is associated with an unfavorable outcome. Prognostic signs for insult severity are initially poor autoregulation plus inability to restore autoregulation despite active attempts to do so. Limited ischemia, especially in the basal ganglia, cannot be detected by ICP-based monitoring of autoregulation and may still result in an unfavorable outcome despite good global autoregulation.

Effect of Adrenaline on Cerebral Blood Oxygenation Measured by NIRS in a Rat Asphyxia Cardiac Arrest Model

Adrenaline is an important pharmacologic treatment during cardiac arrest (CA) for resuscitation. Recent studies suggest that adrenaline increases the likelihood of return of spontaneous circulation (ROSC) but does not contribute to improving neurological outcomes of CA. The mechanisms have not been elucidated yet. A bimodal increase in mean arterial pressure (MAP) is observed after adrenaline injection in rodent CA models (Okuma et al. Intensive Care Med Exp 7(1), 2019). In this study, we focused on alteration of systemic arterial pressure in conjunction with the measurement of cerebral blood oxygenation (CBO) such as oxyhemoglobin (Oxy-Hb), deoxyhemoglobin (Deoxy-Hb), and tissue oxygenation index (TOI) by near-infrared spectroscopy (NIRS). Male Sprague-Dawley rats were used. We attached NIRS between the nasion and the upper cervical spine. Rats underwent 10 minute asphyxia to induce CA. Then, cardiopulmonary resuscitation (CPR) was started, followed by a 20 μg/kg of bolus adrenaline injection at 30 seconds of CPR. This injection accelerated the first increase in MAP, and ROSC was observed with an abrupt increase in CBO. Interestingly, the second increase in MAP, once it exceeded a certain value, was accompanied by paradoxical decreases of Oxy-Hb and TOI while Deoxy-Hb increased. Based on this finding, we compared Oxy-Hb, Deoxy-Hb, and TOI at the first MAP ≈ 100 mmHg and the second MAP ≈ 100 mmHg. The average of Oxy-Hb and TOI from the 13 animals significantly decreased at the second increase in MAP over 100 mmHg while Deoxy-Hb significantly increased. NIRS identified a decrease in Oxy-Hb after ROSC. These findings may be a clue in understanding the mechanism of how and why adrenaline alters the neurological outcomes of CA post resuscitation.

Effect of Adrenaline on Cerebral Blood Oxygenation Measured by NIRS in a Rat Asphyxia Cardiac Arrest Model

Adrenaline is an important pharmacologic treatment during cardiac arrest (CA) for resuscitation. Recent studies suggest that adrenaline increases the likelihood of return of spontaneous circulation (ROSC) but does not contribute to improving neurological outcomes of CA. The mechanisms have not been elucidated yet. A bimodal increase in mean arterial pressure (MAP) is observed after adrenaline injection in rodent CA models [17]. In this study, we focused on alteration of systemic arterial pressure in conjunction with the measurement of cerebral blood oxygenation (CBO) such as oxyhemoglobin (Oxy-Hb), deoxyhemoglobin (Deoxy-Hb), and tissue oxygenation index (TOI) by near-infrared spectroscopy (NIRS). Male Sprague-Dawley rats were used. We attached NIRS between the nasion and the upper cervical spine. Rats underwent 10-minute asphyxia to induce CA. Then, cardiopulmonary resuscitation (CPR) was started, followed by a 20 μg/kg of bolus adrenaline injection at 30 seconds of CPR. This injection accelerated the first increase in MAP, and ROSC was observed with an abrupt increase in CBO. Interestingly, the second increase in MAP, once it exceeded a certain value, was accompanied by paradoxical decreases of Oxy-Hb and TOI, while Deoxy-Hb increased. Based on this finding, we compared Oxy-Hb, Deoxy-Hb, and TOI at the first MAP ≈ 100 mmHg and the second MAP ≈ 100 mmHg. The average of Oxy-Hb and TOI from the 13 animals significantly decreased at the second increase in MAP over 100 mmHg, while Deoxy-Hb significantly increased. NIRS identified a decrease in Oxy-Hb after ROSC. These findings may be a clue to understanding the mechanism of how and why adrenaline alters the neurological outcomes of CA post-resuscitation.

Predictive Value of Estimated Lean Body Mass for Neurological Outcomes after Out-of-Hospital Cardiac Arrest

Background: Postcardiac arrest patients with a return of spontaneous circulation (ROSC) are critically ill, and high body mass index (BMI) is ascertained to be associated with good prognosis in patients with a critically ill condition. However, the exact mechanism has been unknown. To assess the effectiveness of skeletal muscles in reducing neuronal injury after the initial damage owing to cardiac arrest, we investigated the relationship between estimated lean body mass (LBM) and the prognosis of postcardiac arrest patients. Methods: This retrospective cohort study included adult patients with ROSC after out-of-hospital cardiac arrest from January 2015 to March 2020. The enrolled patients were allocated into good- and poor-outcome groups (cerebral performance category (CPC) scores 1–2 and 3–5, respectively). Estimated LBM was categorized into quartiles. Multivariate regression models were used to evaluate the association between LBM and a good CPC score. The area under the receiver operating characteristic curve (AUROC) was assessed. Results: In total, 155 patients were analyzed (CPC score 1–2 vs. 3–5, n = 70 vs. n = 85). Patients’ age, first monitored rhythm, no-flow time, presumed cause of arrest, BMI, and LBM were different (p < 0.05). Fourth-quartile LBM (≥48.98 kg) was associated with good neurological outcome of postcardiac arrest patients (odds ratio = 4.81, 95% confidence interval (CI), 1.10–25.55, p = 0.04). Initial high LBM was also a predictor of good neurological outcomes (AUROC of multivariate regression model including LBM: 0.918). Conclusions: Initial LBM above 48.98kg is a feasible prognostic factor for good neurological outcomes in postcardiac arrest patients.

Positron Emission Tomography After Ischemic Brain Injury: Current Challenges and Future Developments

Positron emission tomography (PET) is widely used in clinical and animal studies, along with the development of diverse tracers. The biochemical characteristics of PET tracers may help uncover the pathophysiological consequences of cardiac arrest (CA) and ischemic stroke, which include cerebral ischemia and reperfusion, depletion of oxygen and glucose, and neuroinflammation. PubMed was searched for studies of the application of PET for "cardiac arrest," "ischemic stroke," and "targeted temperature management." Available studies were included and classified according to the biochemical properties involved and metabolic processes of PET tracers, and were summarized. The mechanisms of ischemic brain injuries were investigated by PET with various tracers to elucidate the pathological process from the initial decrease of cerebral blood flow (CBF) to the subsequent abnormalities in energy and oxygen metabolism, to the monitoring of inflammation. In general, the trends of cerebral blood flow and oxygen metabolism after ischemic attack are not unidirectional but closely related to the time point of injury and recovery. Glucose metabolism after injury showed significant differences in different brain regions whereas global cerebral metabolic rate of glucose (CMRglc) declined. PET monitoring of neuroinflammation shows comparable efficacy to immunostaining. The technology of PET targeting in brain metabolism and the development of tracers provide new tools to track and evaluate the brain's pathological changes after ischemic brain injury. Despite no existing evidence for an available PET-based prediction method, discoveries of new tracers are expected to provide more possibilities for the whole field.

The critically ill brain after cardiac arrest

Cardiac arrest can cause hypoxic-anoxic ischemic brain injury due to signaling cascades that lead to damaged cell membranes and vital cellular organelles, resulting in cell death in the setting of low or no oxygen. Some brain areas are more prone to damage than others, so patients with hypoxic-anoxic ischemic brain injury present with several outcomes, including reduced level of consciousness or alertness, memory deficits, uncoordinated movements, and seizures. Some patients may have mild deficits, while others may have such severe injury that it can progress to brain death. High-quality cardiopulmonary resuscitation is a proven technique to improve outcome after cardiac arrest, although morbidity and mortality remain high. Induced hypothermia, which involves artificially cooling the body immediately after cardiac arrest, may reduce injury to the brain and improve morbidity and mortality. Neuroprognostication after cardiac arrest is challenging and requires a multimodal approach involving clinical neurologic examinations, brain imaging, electrical studies to assess brain activity, and biomarkers to predict outcome.

Resuscitating the Globally Ischemic Brain: TTM and Beyond

Cardiac arrest (CA) afflicts ~ 550,000 people each year in the USA. A small fraction of CA sufferers survive with a majority of these survivors emerging in a comatose state. Many CA survivors suffer devastating global brain injury with some remaining indefinitely in a comatose state. The pathogenesis of global brain injury secondary to CA is complex. Mechanisms of CA-induced brain injury include ischemia, hypoxia, cytotoxicity, inflammation, and ultimately, irreversible neuronal damage. Due to this complexity, it is critical for clinicians to have access as early as possible to quantitative metrics for diagnosing injury severity, accurately predicting outcome, and informing patient care. Current recommendations involve using multiple modalities including clinical exam, electrophysiology, brain imaging, and molecular biomarkers. This multi-faceted approach is designed to improve prognostication to avoid "self-fulfilling" prophecy and early withdrawal of life-sustaining treatments. Incorporation of emerging dynamic monitoring tools such as diffuse optical technologies may provide improved diagnosis and early prognostication to better inform treatment. Currently, targeted temperature management (TTM) is the leading treatment, with the number of patients needed to treat being ~ 6 in order to improve outcome for one patient. Future avenues of treatment, which may potentially be combined with TTM, include pharmacotherapy, perfusion/oxygenation targets, and pre/postconditioning. In this review, we provide a bench to bedside approach to delineate the pathophysiology, prognostication methods, current targeted therapies, and future directions of research surrounding hypoxic-ischemic brain injury (HIBI) secondary to CA.

State-of-the-art considerations in post-arrest care

Cardiac arrest has a high rate of morbidity and mortality. Several advances in post-cardiac arrest management can improve outcome, but are time-dependent, placing the emergency physician in a critical role to both recognize the need for and initiate therapy. We present a novel perspective of both the workup and therapeutic interventions geared toward the emergency physician during the first few hours of care. We describe how the immediate care of a post-cardiac arrest patient is resource intensive and requires simultaneous evaluation for the underlying cause and intensive management to prevent further end organ damage, particularly of the central nervous system. The goal of the initial focused assessment is to rapidly determine if any reversible causes of cardiac arrest are present and to intervene when possible. Interventions performed in this acute period are aimed at preventing additional brain injury through optimizing hemodynamics, providing ventilatory support, and by using therapeutic hypothermia when indicated. After the initial phase of care, disposition is guided by available resources and the clinician's judgment. Transfer to a specialized cardiac arrest center is prudent in centers that do not have significant support or experience in the care of these patients.

Does 'heads-up' cardiopulmonary resuscitation improve outcomes for patients in out-of-hospital cardiac arrest? A systematic review

Introduction

Survival rates for patients in out-of-hospital cardiac arrest have remained around 10% in the United Kingdom for the past seven years. If outcomes are to be improved, research into new methods of advanced life support is required. One such method may be ‘heads-up’ cardiopulmonary resuscitation.

Methods:

A systematic review of literature exploring heads-up cardiopulmonary resuscitation was conducted in an attempt to identify its effects on survival to discharge and neurological outcome.

Results:

A comprehensive search of CINAHL, MEDLINE and Google Scholar was undertaken. Six papers were classed as sufficiently relevant for inclusion. Included studies were generally of low quality and none studied the effect of heads-up cardiopulmonary resuscitation on out-of-hospital cardiac arrest patients. Animal studies identified a significant reduction in intracranial pressure and increase in cerebral and coronary perfusion pressure for use of augmented heads-up cardiopulmonary resuscitation in the porcine model of cardiac arrest.

Conclusion:

Further research is required to analyse the effects and potential benefits of augmented heads-up cardiopulmonary resuscitation in out-of-hospital cardiac arrest.

Cerebrovascular autoregulation following cardiac arrest: Protocol for a post hoc analysis of the randomised COMACARE pilot trial

BACKGROUND

Approximately two-thirds of the mortality following out of hospital cardiac arrest is related to devastating neurological injury. Previous small cohort studies have reported an impaired cerebrovascular autoregulation following cardiac arrest, but no studies have assessed the impact of differences in oxygen and carbon dioxide tensions in addition to mean arterial pressure management.

METHODS

This is a protocol and statistical analysis plan to assess the correlation between changes in cerebral tissue oxygenation and arterial pressure as measure of cerebrovascular autoregulation, the tissue oxygenation index, in patients following out of hospital cardiac arrest and in healthy volunteers. The COMACARE study included 120 comatose survivors of out of hospital cardiac arrest admitted to ICU and managed with low-normal or high-normal targets for mean arterial pressure, arterial oxygen and carbon dioxide partial pressures. In addition, 102 healthy volunteers have been investigated as a reference group for the tissue oxygenation index. In both cohorts, the cerebral tissue oxygenation was measured by near infrared spectroscopy.

CONCLUSIONS

Cerebrovascular autoregulation is critical to maintain homoeostatic brain perfusion. This study of changes in autoregulation following out of hospital cardiac arrest over the first 48 hours, as compared to data from healthy volunteers, will generate important physiological information that may guide the rationale and design of interventional studies.

Management of post-cardiac arrest syndrome

Post-cardiac arrest syndrome is a complex and critical issue in resuscitated patients undergone cardiac arrest. Ischemic-reperfusion injury occurs in multiple organs due to the return of spontaneous circulation. Bundle of management practicies are required for post-cardiac arrest care. Early invasive coronary angiography should be considered to identify and treat coronary artery obstructive disease. Vasopressors such as norepinephrine and dobutamine are the first-line treatment for shock. Maintainance of oxyhemoglobin saturation greater than 94% but less than 100% is recommended to avoid fatality. Target temperature therapeutic hypothermia helps to resuscitated patients. Strict temperature control is required and is maintained with the help of cooling devices and monitoring the core temperature. Montorings include electrocardiogram, oxymetry, capnography, and electroencephalography (EEG) along with blood pressue, temprature, and vital signs. Seizure should be treated if EEG shows evidence of seizure or epileptiform activity. Clinical neurologic examination and magnetic resonance imaging are considered to predict neurological outcome. Glycemic control and metabolic management are favorable for a good neurological outcome. Recovery from acute kidney injury is essential for survival and a good neurological outcome.

Conventional and functional magnetic resonance imaging features of late subacute cortical laminar necrosis in a dog

Cerebral cortical laminar necrosis (CLN) is a consequence of severe hypoxic, ischemic, or hypoglycemic events. In humans, these cortical lesions show characteristic linear T1‐weighted (T1W) hyperintensity in the late subacute stage. Limited information reporting magnetic resonance imaging (MRI) findings in dogs affected by CLN is available. A 3‐year‐old Belgian Shepherd dog was referred 8 days after sudden onset of blindness after general anesthesia. Neurological examination showed central blindness and mild ataxia. Three‐Tesla MRI examination of the brain revealed bilateral asymmetrical areas of T2‐weighted hyperintensity within the occipital, parietal, temporal, and frontal cortex, involving gray and white matter. Furthermore, linear T1W‐hyperintense lesions were found in the cerebral cortex of the same areas and showed heterogeneous contrast enhancement. Perfusion‐weighted images revealed hyperperfusion in the affected regions. Lesions were compatible with subacute CLN with corresponding edema suspected to be secondary to anesthesia‐related brain hypoxia. Three‐Tesla MRI enabled identification of the laminar pattern of the cortical lesions.