Neurologic changes during critical illness: brain imaging findings and neurobehavioral outcomes

Acute Abnormalities Identified on Brain Magnetic Resonance Imaging in Patients with Sepsis

BACKGROUND

Sepsis often codevelops with brain damage, and the mechanisms underlying sepsis-related brain damage have been elucidated. However, only a few studies have reported the diagnostic imaging assessments for brain damage in sepsis. Therefore, in this study, we analyzed the brain magnetic resonance (MR) imaging (MRI) findings of patients with sepsis.

METHODS

This single-center prospective observational study included 71 patients with sepsis who underwent brain MRI, regardless of the presence or absence of shocks and acute neurological abnormalities. The MR images were classified according to the presence or absence of acute cerebral ischemia and leukoencephalopathy, with normal findings indicating neither condition.

RESULTS

The MR images of 18 patients (25.3%) showed acute cerebral ischemia and leukoencephalopathy. Furthermore, 44 patients (62.0%) had only leukoencephalopathy. In terms of patient demographic characteristics and neurological outcomes, significant differences were noted among patients with acute cerebral ischemia findings, those with leukoencephalopathy findings, and those with neither. There were significant differences in age (P = 0.0296), neurological findings (P = 0.0057), number of days in the intensive care unit (P = 0.0239), acute disseminated intravascular coagulation score during hospitalization (P = 0.0363), and the Katz index at discharge or transfer (P = 0.0020) among these groups.

CONCLUSIONS

Among patients with sepsis, 25.3% showed acute cerebral ischemia findings on brain MRI, regardless of illness severity, including hypoxia and hypotension, and presence of shock. Abnormal MRI findings were also observed in patients without acute brain dysfunction. Importantly, abnormal brain MRI findings were associated with worse neurological outcomes.

Management of severe acute encephalopathy in the ICU: an expert consensus statement from the french society of intensive care medicine

INTRODUCTION

Acute encephalopathy in the ICU poses significant diagnostic, therapeutic, and prognostic challenges. Standardized expert guidelines on acute encephalopathy are needed to improve diagnostic methods, therapeutic decisions, and prognostication.

METHODS

The experts conducted a review of the literature, analysed it according to the GRADE (Grading of Recommendation, Assessment, Development and Evaluation) methodology and made proposals for guidelines, which were rated by other experts. Only expert opinions with strong agreement were selected.

RESULTS

The synthesis of expert work and the application of the GRADE method resulted in 39 recommendations. Among the 39 formalized recommendations, 1 had a high level of evidence (GRADE 1 +) and 10 had a low level of evidence (GRADE 2 + or 2-). These recommendations describe indication for ICU admission, use of clinical scores and EEG for diagnosis, detection of complications, and prognostication. The remaining 28 recommendations were based on expert consensus. These recomandations describe common indications for blood and CSF studies, neuroimaging, use of neuromonitoring, and provide guidelines for management in the acute phase.

CONCLUSION

This expert consensus statement aims to provide a structured framework to enhance the consistency and quality of care for ICU patients presenting with acute encephalopathy. By integrating high-quality evidence with expert opinion, it offers a pragmatic approach to addressing the complex nature of acute encephalopathy in the ICU, promoting best practices in patient care and facilitating future research in the field.

The role of peripheral inflammatory insults in Alzheimer's disease: a review and research roadmap

Peripheral inflammation, defined as inflammation that occurs outside the central nervous system, is an age-related phenomenon that has been identified as a risk factor for Alzheimer's disease. While the role of chronic peripheral inflammation has been well characterized in the context of dementia and other age-related conditions, less is known about the neurologic contribution of acute inflammatory insults that take place outside the central nervous system. Herein, we define acute inflammatory insults as an immune challenge in the form of pathogen exposure (e.g., viral infection) or tissue damage (e.g., surgery) that causes a large, yet time-limited, inflammatory response. We provide an overview of the clinical and translational research that has examined the connection between acute inflammatory insults and Alzheimer's disease, focusing on three categories of peripheral inflammatory insults that have received considerable attention in recent years: acute infection, critical illness, and surgery. Additionally, we review immune and neurobiological mechanisms which facilitate the neural response to acute inflammation and discuss the potential role of the blood-brain barrier and other components of the neuro-immune axis in Alzheimer's disease. After highlighting the knowledge gaps in this area of research, we propose a roadmap to address methodological challenges, suboptimal study design, and paucity of transdisciplinary research efforts that have thus far limited our understanding of how pathogen- and damage-mediated inflammatory insults may contribute to Alzheimer's disease. Finally, we discuss how therapeutic approaches designed to promote the resolution of inflammation may be used following acute inflammatory insults to preserve brain health and limit progression of neurodegenerative pathology.

Brain Volume Changes after COVID-19 Compared to Healthy Controls by Artificial Intelligence-Based MRI Volumetry

Cohort studies that quantify volumetric brain data among individuals with different levels of COVID-19 severity are presently limited. It is still uncertain whether there exists a potential correlation between disease severity and the effects of COVID-19 on brain integrity. Our objective was to assess the potential impact of COVID-19 on measured brain volume in patients with asymptomatic/mild and severe disease after recovery from infection, compared with healthy controls, using artificial intelligence (AI)-based MRI volumetry. A total of 155 participants were prospectively enrolled in this IRB-approved analysis of three cohorts with a mild course of COVID-19 (n = 51, MILD), a severe hospitalised course (n = 48, SEV), and healthy controls (n = 56, CTL) all undergoing a standardised MRI protocol of the brain. Automated AI-based determination of various brain volumes in mL and calculation of normalised percentiles of brain volume was performed with mdbrain software, using a 3D T1-weighted magnetisation-prepared rapid gradient echo (MPRAGE) sequence. The automatically measured brain volumes and percentiles were analysed for differences between groups. The estimated influence of COVID-19 and demographic/clinical variables on brain volume was determined using multivariate analysis. There were statistically significant differences in measured brain volumes and percentiles of various brain regions among groups, even after the exclusion of patients undergoing intensive care, with significant volume reductions in COVID-19 patients, which increased with disease severity (SEV > MILD > CTL) and mainly affected the supratentorial grey matter, frontal and parietal lobes, and right thalamus. Severe COVID-19 infection, in addition to established demographic parameters such as age and sex, was a significant predictor of brain volume loss upon multivariate analysis. In conclusion, neocortical brain degeneration was detected in patients who had recovered from SARS-CoV-2 infection compared to healthy controls, worsening with greater initial COVID-19 severity and mainly affecting the fronto-parietal brain and right thalamus, regardless of ICU treatment. This suggests a direct link between COVID-19 infection and subsequent brain atrophy, which may have major implications for clinical management and future cognitive rehabilitation strategies.

Neurological complications of sepsis

PURPOSE OF REVIEW

Sepsis, defined as life-threatening organ dysfunction caused by a dysregulated host response to infection, is a leading cause of hospital and ICU admission. The central and peripheral nervous system may be the first organ system to show signs of dysfunction, leading to clinical manifestations such as sepsis-associated encephalopathy (SAE) with delirium or coma and ICU-acquired weakness (ICUAW). In the current review, we want to highlight developing insights into the epidemiology, diagnosis, prognosis, and treatment of patients with SAE and ICUAW.

RECENT FINDINGS

The diagnosis of neurological complications of sepsis remains clinical, although the use of electroencephalography and electromyography can support the diagnosis, especially in noncollaborative patients, and can help in defining disease severity. Moreover, recent studies suggest new insights into the long-term effects associated with SAE and ICUAW, highlighting the need for effective prevention and treatment.

SUMMARY

In this manuscript, we provide an overview of recent insights and developments in the prevention, diagnosis, and treatment of patients with SAE and ICUAW.

Delirium-related psychiatric and neurocognitive impairment and the association with post-intensive care syndrome-A narrative review

INTRODUCTION

Delirium is common among patients admitted to the intensive care unit (ICU) and its impact on the neurocognitive and psychiatric state of survivors is of great interest. These new-onset or worsening conditions, together with physical alterations, are called post-intensive care syndrome (PICS). Our aim is to update on the latest screening and follow-up options for psychological and cognitive sequelae of PICS.

METHOD

This narrative review discusses the occurrence of delirium in ICU settings and the relatively new concept of PICS. Psychiatric and neurocognitive morbidities that may occur in survivors of critical illness following delirium are addressed. Future perspectives for practice and research are discussed.

RESULTS

There is no "gold standard" for diagnosing delirium in the ICU, but two extensively validated tools, the confusion assessment method for the ICU and the intensive care delirium screening checklist, are often used. PICS complaints are frequent in ICU survivors who have suffered delirium and have been recognized as an important public health and socio-economic problem worldwide. Depression, anxiety, post-traumatic stress disorder, and long-term cognitive impairment are recurrently exhibited. Screening tools for these deficits are discussed, as well as the suggestion of early assessment after discharge and at 3 and 12 months.

CONCLUSIONS

Delirium is a complex but common phenomenon in the ICU and a risk factor for PICS. Its diagnosis is challenging with potential long-term adverse outcomes, including psychiatric and cognitive difficulties. The implementation of screening and follow-up protocols for PICS sequelae is warranted to ensure early detection and appropriate management.

Texture Feature-Based Machine Learning Classification on MRI Image for Sepsis-Associated Encephalopathy Detection: A Pilot Study

Objective

The objective of this study was to assess the performance of combining MRI-based texture analysis with machine learning for differentiating sepsis-associated encephalopathy (SAE) from sepsis alone.

Method

Sixty-six MRI-T1WI images of an SAE patient and 125 images of patients with sepsis alone were collected. Frontal lobe, brain stem, hippocampus, and amygdala were selected as regions of interest (ROIs). 279 texture features of each ROI were obtained using MaZda software. After the dimension reduction, 30 highly discriminative features of each ROI were adopted to differentiate SAE from sepsis alone using the CatBoost model.

Results

The classification models of frontal, brain stem, hippocampus, and amygdala were constructed. The classification accuracy was above 0.83, and the area under the curve (AUC) exceeded 0.90 in the validation set.

Conclusion

The texture features differed between SAE patients and patients with sepsis alone in different anatomical locations, suggesting that MRI-based texture analysis with machine learning might be helpful in differentiating SAE from sepsis alone.

Relationship between brain volume reduction during the acute phase of sepsis and activities of daily living in elderly patients: A prospective cohort study

Brain damage in acute sepsis may be associated with poor long-term outcomes that impair reintegration into society. We aimed to clarify whether brain volume reduction occurs during the acute phase of sepsis in patients with acute brain damage. In this prospective, noninterventional observational study, brain volume reduction was evaluated by comparing head computed tomography findings at admission with those obtained during hospitalization. We examined the association between brain volume reduction and performance of the activities of daily living in 85 consecutive patients (mean age, 77 ± 12.7 years) with sepsis or septic shock. The bicaudate ratio increased in 38/58 (65.5%) patients, Evans index increased in 35/58 (60.3%) patients, and brain volume by volumetry decreased in 46/58 (79.3%) patients from the first to the second measurement, with significant increases in the bicaudate ratio (P < 0.0001) and Evans index (P = 0.0005) and a significant decrease in the brain volume by volumetry (P < 0.0001). The change rate for brain volume by volumetry was significantly correlated with the Katz index (ρ = -0.3790, P = 0.0094). In the acute phase of sepsis in this sample of older patients, 60-79% of patients showed decreased brain volumes. This was associated with a decreased capacity for performing activities of daily living.

Posterior Reversible Encephalopathy in Sepsis-Associated Encephalopathy: Experience from a Single Center

BACKGROUND

Sepsis-associated encephalopathy (SAE) is frequently encountered in sepsis and is often accompanied by neuroimaging findings indicating ischemia, hemorrhage, and edema. Posterior reversible encephalopathy syndrome (PRES) has been vastly underrecognized in previously reported cohorts of patients with sepsis and SAE. Our aim was to determine the prevalence and distinguishing clinical, neuroimaging, and electroencephalography features of PRES in SAE.

METHODS

In this prospective observational study, patients with radiologically identified PRES were selected from a consecutively enrolled cohort of 156 patients with SAE and assessed for neurological outcome using the extended Glasgow Outcome Scale for 12 months. Patients with SAE and PRES and other types of brain lesions were compared in terms of clinical and diagnostic workup features.

RESULTS

Fourteen of 156 patients (8.9%) were determined to be radiologically compatible with PRES, whereas 48 patients displayed other types of acute brain lesions. Patients with PRES often showed lesions in atypical regions, including frontal lobes, the corpus callosum, and the basal ganglia. Source of infection was mostly gram-negative bacteria originating from pneumonia or intraabdominal infections. Patients with PRES were not different from other patients with SAE with brain lesions in terms of features of sepsis and neurological outcome. However, patients with PRES showed increased prevalence of seizures and intraabdominal source of infection.

CONCLUSIONS

PRES is highly prevalent in SAE, often encompasses unusual brain regions, and usually presents with generalized seizures. Patients with SAE and PRES do not appear to have distinguishing clinical and diagnostic workup features. However, generalized seizures may serve as warning signs for presence of PRES in patients with SAE.

Adapting the UK Biobank Brain Imaging Protocol and Analysis Pipeline for the C-MORE Multi-Organ Study of COVID-19 Survivors

SARS-CoV-2 infection has been shown to damage multiple organs, including the brain. Multiorgan MRI can provide further insight on the repercussions of COVID-19 on organ health but requires a balance between richness and quality of data acquisition and total scan duration. We adapted the UK Biobank brain MRI protocol to produce high-quality images while being suitable as part of a post-COVID-19 multiorgan MRI exam. The analysis pipeline, also adapted from UK Biobank, includes new imaging-derived phenotypes (IDPs) designed to assess the possible effects of COVID-19. A first application of the protocol and pipeline was performed in 51 COVID-19 patients post-hospital discharge and 25 controls participating in the Oxford C-MORE study. The protocol acquires high resolution T1, T2-FLAIR, diffusion weighted images, susceptibility weighted images, and arterial spin labelling data in 17 min. The automated imaging pipeline derives 1,575 IDPs, assessing brain anatomy (including olfactory bulb volume and intensity) and tissue perfusion, hyperintensities, diffusivity, and susceptibility. In the C-MORE data, IDPs related to atrophy, small vessel disease and olfactory bulbs were consistent with clinical radiology reports. Our exploratory analysis tentatively revealed some group differences between recovered COVID-19 patients and controls, across severity groups, but not across anosmia groups. Follow-up imaging in the C-MORE study is currently ongoing, and this protocol is now being used in other large-scale studies. The protocol, pipeline code and data are openly available and will further contribute to the understanding of the medium to long-term effects of COVID-19.

Dutch multicentre, prospective follow-up, cohort study comparing the neurological and neuropsychological sequelae of hospitalised non-ICU- and ICU-treated COVID-19 survivors: a study protocol

INTRODUCTION

Owing to the novelty of COVID-19, there are still large knowledge gaps concerning its effect on the brain and the resulting impact on peoples' lives. This large-scale prospective follow-up study investigates COVID-19-associated brain damage, neuropsychological dysfunction and long-term impact on the well-being of patients and their close ones. It is hypothesised that structural brain damage and cognitive dysfunction primarily occur in severely ill patients, as compared with moderately ill patients. Cognitive complaints, emotional distress and impact on well-being are hypothesised to be less dependent on illness severity.

METHODS AND ANALYSIS

For this multicentre study, 200 patients with COVID-19 (100 intensive care unit (ICU) patients and 100 non-ICU patients) formerly hospitalised in one of the six recruiting hospitals during the first European infection wave (ie, March to June 2020) and their close ones will be recruited. At minimally 6 months posthospital discharge, patients will perform a set of neuropsychological tests and are subjected to a 3T MRI scan. Patients and close ones will fill out a set of questionnaires, also at minimally 6 months posthospital discharge and again another 6 months thereafter. Data related to COVID-19 hospitalisation will be extracted from the patients' medical records. MRI abnormalities will ultimately be related to neuropsychological test performance and questionnaire outcomes.

ETHICS AND DISSEMINATION

Ethics approval was granted by the medical research ethics committee of Maastricht University Medical Centre and Maastricht University (NL75102.068.20). The project is sponsored by The Brain Foundation Netherlands. Findings will be presented at national and international conferences, as well as published in peer-reviewed scientific journals.

TRIAL REGISTRATION NUMBER

NCT04745611.

Basic research and clinical progress of sepsis-associated encephalopathy

Sepsis-associated encephalopathy (SAE), a major cerebral complication of sepsis, occurs in 70% of patients admitted to the intensive care unit (ICU). This condition can cause serious impairment of consciousness and is associated with a high mortality rate. Thus far, several experimental screenings and radiological techniques (e.g., electroencephalography) have been used for the non-invasive assessment of the structure and function of the brain in patients with SAE. Nevertheless, the pathogenesis of SAE is complicated and remains unclear. In the present article, we reviewed the currently available literature on the epidemiology, clinical manifestations, pathology, diagnosis, and management of SAE. However, currently, there is no ideal pharmacological treatment for SAE. Treatment targeting mitochondrial dysfunction may be useful in the management of SAE.

Brain Volume Changes in Patients with Acute Brain Dysfunction Due to Sepsis

BACKGROUND

Sepsis-induced brain dysfunction (SIBD) is often encountered in sepsis patients and is related to increased morbidity. No specific tests are available for SIBD, and neuroimaging findings are often normal. In this study, our aim was to analyze the diagnostic value of volumetric analysis of the brain structures and to find out its significance as a prognostic measure.

METHODS

In this prospective observational study, brain magnetic resonance imaging (MRI) sections of 25 consecutively enrolled SIBD patients (17 with encephalopathy and 8 with coma) and 22 healthy controls underwent volumetric evaluation by an automated segmentation method.

RESULTS

Ten SIBD patients had normal MRI, and 15 patients showed brain lesions or atrophy. The most prominent volume reduction was found in cerebral and cerebellar white matter, cerebral cortex, hippocampus, and amygdala, whereas deep gray matter regions and cerebellar cortex were relatively less affected. SIBD patients with normal MRI showed significantly reduced volumes in hippocampus and cerebral white matter. Caudate nuclei, putamen, and thalamus showed lower volume values in non-survivor SIBD patients, and left putamen and right thalamus showed a more pronounced volume reduction in coma patients.

CONCLUSIONS

Volumetric analysis of the brain appears to be a sensitive measure of volumetric changes in SIBD. Volume reduction in specific deep gray matter regions might be an indicator of unfavorable outcome.

Brain MRI after critical care admission: A longitudinal imaging study

PURPOSE

To investigate the association between episodes of critical care hospitalizations and delirium with structural brain changes in older adults.

MATERIALS AND METHODS

We included Mayo Clinic Study of Aging participants ≥60 years old at the time of study enrollment (October 29, 2004, through September 11, 2017) with available brain MRI and 'amyloid' positron emission tomography (PET) scans. We tested the hypothesis that a) intensive care unit (ICU) admission is associated with greater cortical thinning and atrophy in entorhinal cortex, inferior temporal cortex, middle temporal cortex, and fusiform cortex (Alzheimer''s disease-signature regions); b) atrophy in hippocampus and corpus callosum; c) delirium accelerates these changes; and d) ICU admission is not associated with increased deposition of cortical amyloid.

RESULTS

ICU admission was associated with cortical thinning in temporal, frontal, and parietal cortices, and decreases in hippocampal/corpus callosum volumes, but not Alzheimer''s disease-signature regions. For hippocampal volume, and 10 of 14 cortical thickness measurements, the change following ICU admission was significantly more pronounced for those who experienced delirium. ICU admission was not associated with an increased amyloid burden.

CONCLUSIONS

Critical care hospitalization is associated with accelerated brain atrophy in selected brain regions, without increases in amyloid deposition, suggesting a pathogenesis based on neurodegeneration unrelated to Alzheimer''s pathway.

Natural History of Cognitive Impairment in Critical Illness Survivors. A Systematic Review

Long-term cognitive impairment is common among ICU survivors, but its natural history remains unclear. In this systematic review, we report the frequency of cognitive impairment in ICU survivors across various time points after ICU discharge that were extracted from 46 of the 3,350 screened records. Prior studies used a range of cognitive instruments, including subjective assessments (10 studies), single or screening cognitive test such as Mini-Mental State Examination or Trail Making Tests A and B (23 studies), and comprehensive cognitive batteries (26 studies). The mean prevalence of cognitive impairment was higher with objective rather than subjective assessments (54% [95% confidence interval (CI), 51–57%] vs. 35% [95% CI, 29–41%] at 3 months after ICU discharge) and when comprehensive cognitive batteries rather than Mini-Mental State Examination were used (ICU discharge: 61% [95% CI, 38–100%] vs. 36% [95% CI, 15–63%]; 12 months after ICU discharge: 43% [95% CI, 10–78%] vs. 18% [95% CI, 10–20%]). Patients with acute respiratory distress syndrome had higher prevalence of cognitive impairment than mixed ICU patients at ICU discharge (82% [95% CI, 78–86%] vs. 48% [95% CI, 44–52%]). Although some studies repeated tests at more than one time point, the time intervals between tests were arbitrary and dictated by operational limitations of individual studies or chosen cognitive instruments. In summary, the prevalence and temporal trajectory of ICU-related cognitive impairment varies depending on the type of cognitive instrument used and the etiology of critical illness. Future studies should use modern comprehensive batteries to better delineate the natural history of cognitive recovery across ICU patient subgroups and determine which acute illness and treatment factors are associated with better recovery trajectories.

Vasopressor Therapy and the Brain: Dark Side of the Moon

Sepsis, a leading cause of morbidity and mortality, is caused by a deregulated host response to pathogens, and subsequent life-threatening organ dysfunctions. All major systems, including the cardiovascular, respiratory, renal, hepatic, hematological, and the neurological system may be affected by sepsis. Sepsis associated neurological dysfunction is triggered by multiple factors including neuro-inflammation, excitotoxicity, and ischemia. Ischemia results from reduced cerebral blood flow, caused by extreme variations of blood pressure, occlusion of cerebral vessels, or more subtle defects of the microcirculation. International guidelines comprehensively describe the initial hemodynamic management of sepsis, revolving around the normalization of systemic hemodynamics and of arterial lactate. By contrast, the management of sepsis patients suffering from brain dysfunction is poorly detailed, the only salient point being mentioned is that sedation and analgesia should be optimized. However, sepsis and the hemodynamic consequences thereof as well as vasopressors may have severe untoward neurological consequences. The current review describes the general neurological complications, as well as the consequences of vasopressor therapy on the brain and its circulation and addresses methods for cerebral monitoring during sepsis.

Challenges in conducting long-term outcomes studies in critical care

PURPOSE OF REVIEW

Evaluating longer term mortality, morbidity, and quality of life in survivors of critical illness is a research priority. This review details the challenges of long-term follow-up studies of critically ill patients and highlights recently proposed methodological solutions.

RECENT FINDINGS

Barriers to long-term follow-up studies of critical care survivors include high rates of study attrition because of death or loss to follow-up, data missingness from experienced morbidity, and lack of standardized outcome as well as reporting of key covariates. A number of recent methods have been proposed to reduce study patients attrition, including minimum data set selection and visits to transitional care or home settings, yet these have significant downsides as well. Conducting long-term follow-up even in the absence of such models carries a high expense, as personnel are very costly, and patients/families require reimbursement for their time and inconvenience.

SUMMARY

There is a reason why many research groups do not conduct long-term outcomes in critical care: it is very difficult. Challenges of long-term follow-up require careful consideration by study investigators to ensure our collective success in data integration and a better understanding of underlying mechanisms of mortality and morbidity seen in critical care survivorship.

Diagnosing acute brain dysfunction due to sepsis

Developments in the management of critically ill patients suffering organ dysfunctions have demonstrated that brain is the prominent organ to be effected during critical illness. Acute brain dysfunction due to pathologic neuroinflammatory processes associated with sepsis is commonly seen and related to morbidity and mortality in the ICU treatment. Studies reported that survivors of sepsis may suffer long-term cognitive dysfunction that affects quality of life. However, there are no specific approaches to diagnose acute brain dysfunction in the early phase to target protective measures. In recent years, imaging methods and biomarkers are the most important issues of studies. This review will address the current diagnostic approaches to acute brain dysfunction related to sepsis.

Assessing the relationship between near-infrared spectroscopy-derived regional cerebral oxygenation and neurological dysfunction in critically ill adults: a prospective observational multicentre protocol, on behalf of the Canadian Critical Care Trials Group

INTRODUCTION

Survivors of critical illness frequently exhibit acute and chronic neurological complications. The underlying aetiology of this dysfunction remains unknown but may be associated with cerebral ischaemia. This study will use near-infrared spectroscopy to non-invasively quantify regional cerebral oxygenation (rSO₂) to assess the association between poor rSO₂ during the first 72 hours of critical illness with delirium severity, as well as long-term sensorimotor and cognitive impairment among intensive care unit (ICU) survivors. Further, the physiological determinants of rSO₂ will be examined.

METHODS AND ANALYSIS

This multicentre prospective observational study will consider adult patients (≥18 years old) eligible for enrolment if within 24 hours of ICU admission, they require mechanical ventilation and/or vasopressor support. For 72 hours, rSO₂ will be continuously recorded, while vital signs (eg, heart rate) and peripheral oxygenation saturation will be concurrently captured with data monitoring software. Arterial and central venous gases will be sampled every 12 hours for the 72 hours recording period and will include: pH, PaO2, PaCO2, and haemoglobin concentration. Participants will be screened daily for delirium with the confusion assessment method (CAM)-ICU, whereas the brief-CAM will be used on the ward. At 3 and 12 months post-ICU discharge, neurological function will be assessed with the Repeatable Battery for the Assessment of Neuropsychological Status and KINARM sensorimotor and cognitive robot-based behavioural tasks.

ETHICS AND DISSEMINATION

The study protocol has been approved in Ontario by a central research ethics board (Clinical Trials Ontario); non-Ontario sites will obtain local ethics approval. The study will be conducted under the guidance of the Canadian Critical Care Trials Group (CCCTG) and the results of this study will be presented at national meetings of the CCCTG for internal peer review. Results will also be presented at national/international scientific conferences. On completion, the study findings will be submitted for publication in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT03141619.

Structural Brain Changes in Delirium: An Integrative Review

Delirium is a serious complication of acute illness. Little is known, however, regarding the neurobiology of delirium, largely due to challenges in studying the complex inpatient population. Neuroimaging is one noninvasive method that can be used to study structural and functional brain abnormalities associated with delirium. The purpose of this integrative literature review was to examine the content and quality of current structural neuroimaging evidence in delirium. After meeting inclusion criteria, 11 articles were included in the review. Commonly noted structural abnormalities were impaired white matter integrity, brain atrophy, ischemic lesions, edema, and inflammation. Findings demonstrated widespread alterations in several brain structures. Limitations of the studies in this review included small sample sizes, inappropriate or questionable delirium measurements, and failure to consider confounding variables. This review provides insight into possible structural changes responsible for the signs and symptoms seen in patients with delirium, but more high-quality studies are needed.

Targeting the Blood-Brain Barrier to Prevent Sepsis-Associated Cognitive Impairment

Sepsis is a systemic inflammatory disease resulting from an infection. This disorder affects 750 000 people annually in the United States and has a 62% rehospitalization rate. Septic symptoms range from typical flu-like symptoms (eg, headache, fever) to a multifactorial syndrome known as sepsis-associated encephalopathy (SAE). Patients with SAE exhibit an acute altered mental status and often have higher mortality and morbidity. In addition, many sepsis survivors are also burdened with long-term cognitive impairment. The mechanisms through which sepsis initiates SAE and promotes long-term cognitive impairment in septic survivors are poorly understood. Due to its unique role as an interface between the brain and the periphery, numerous studies support a regulatory role for the blood-brain barrier (BBB) in the progression of acute and chronic brain dysfunction. In this review, we discuss the current body of literature which supports the BBB as a nexus which integrates signals from the brain and the periphery in sepsis. We highlight key insights on the mechanisms that contribute to the BBB's role in sepsis which include neuroinflammation, increased barrier permeability, immune cell infiltration, mitochondrial dysfunction, and a potential barrier role for tissue non-specific alkaline phosphatase (TNAP). Finally, we address current drug treatments (eg, antimicrobials and intravenous immunoglobulins) for sepsis and their potential outcomes on brain function. A comprehensive understanding of these mechanisms may enable clinicians to target specific aspects of BBB function as a therapeutic tool to limit long-term cognitive impairment in sepsis survivors.

Neuroimaging Findings in Sepsis-Induced Brain Dysfunction: Association with Clinical and Laboratory Findings

BACKGROUND

Incidence and patterns of brain lesions of sepsis-induced brain dysfunction (SIBD) have been well defined. Our objective was to investigate the associations between neuroimaging features of SIBD patients and well-known neuroinflammation and neurodegeneration factors.

METHODS

In this prospective observational study, 93 SIBD patients (45 men, 48 women; 50.6 ± 12.7 years old) were enrolled. Patients underwent a neurological examination and brain magnetic resonance imaging (MRI). Severity-of-disease scoring systems (APACHE II, SOFA, and SAPS II) and neurological outcome scoring system (GOSE) were used. Also, serum levels of a panel of mediators [IL-1β, IL-6, IL-8, IL-10, IL-12, IL-17, IFN-γ, TNF-α, complement factor Bb, C4d, C5a, iC3b, amyloid-β peptides, total tau, phosphorylated tau (p-tau), S100b, neuron-specific enolase] were measured by ELISA. Voxel-based morphometry (VBM) was employed to available patients for assessment of neuronal loss pattern in SIBD.

RESULTS

MRI of SIBD patients were normal (n = 27, 29%) or showed brain lesions (n = 51, 54.9%) or brain atrophy (n = 15, 16.1%). VBM analysis showed neuronal loss in the insula, cingulate cortex, frontal lobe, precuneus, and thalamus. Patients with abnormal MRI findings had worse APACHE II, SOFA, GOSE scores, increased prevalence of delirium and mortality. Presence of MRI lesions was associated with reduced C5a and iC3b levels and brain atrophy was associated with increased p-tau levels. Regression analysis identified an association between C5a levels and presence of lesion on MRI and p-tau levels and the presence of atrophy on MRI.

CONCLUSIONS

Neuronal loss predominantly occurs in limbic and visceral pain perception regions of SIBD patients. Complement breakdown products and p-tau stand out as adverse neuroimaging outcome markers for SIBD.

Fructose-1,6-bisphosphate preserves glucose metabolism integrity and reduces reactive oxygen species in the brain during experimental sepsis

Sepsis is one of the main causes of hospitalization and mortality in Intensive Care Units. One of the first manifestations of sepsis is encephalopathy, reported in up to 70% of patients, being associated with higher mortality and morbidity. The factors that cause sepsis-associated encephalopathy (SAE) are still not well known, and may be multifactorial, as perfusion changes, neuroinflammation, oxidative stress and glycolytic metabolism alterations. Fructose-1,6-bisphosphate (FBP), a metabolite of the glycolytic route, has been reported as neuroprotective agent. The present study used an experimental sepsis model in C57BL/6 mice. We used in vivo brain imaging to evaluate glycolytic metabolism through microPET scans and the radiopharmaceutical ¹⁸F-fluoro-2-deoxy-D-glucose (¹⁸F-FDG). Brain images were obtained before and 12 h after the induction of sepsis in animals with and without FBP treatment. We also evaluated the treatment effects in the brain oxidative stress by measuring the production of reactive oxygen species (ROS), the activity of catalase (CAT) and glutathione peroxidase (GPx), and the levels of fluorescent marker 2'7'-dichlorofluorescein diacetate (DCF). There was a significant decrease in brain glucose metabolism due to experimental sepsis. A significant protective effect of FBP treatment was observed in the cerebral metabolic outcomes. FBP also modulated the production of ROS, evidenced by reduced CAT activity and lower levels of DCF. Our results suggest that FBP may be a possible candidate in the treatment of SAE.

Brain Tissue Oxygenation in Patients with Septic Shock: a Feasibility Study

BACKGROUND

Delirium is common in critically ill patients and its presence is associated with increased mortality and increased likelihood of poor cognitive function among survivors. However, the cause of delirium is unknown. The purpose of this study was to demonstrate the feasibility of using near-infrared spectroscopy (NIRS) to assess brain tissue oxygenation in patients with septic shock, who are at high risk of developing delirium.

METHODS

This prospective observational study was conducted in a 33-bed general medical surgical intensive care unit (ICU). Patients with severe sepsis or septic shock were eligible for recruitment. The FORESIGHT NIRS monitor was used to assess brain tissue oxygenation in the frontal lobes for the first 72 hours of ICU admission. Physiological data was also recorded. We used the Confusion Assessment Method-ICU to screen for delirium.

RESULTS

From March 1st 2014-September 30th 2014, 10 patients with septic shock were recruited. The NIRS monitor captured 81% of the available data. No adverse events were recorded. Brain tissue oxygenation demonstrated significant intra- and inter-individual variability in the way it correlated with physiological parameters, such as mean arterial pressure, heart rate, and peripheral oxygen saturation. Mean brain tissue oxygen levels were significantly lower in patients who were delirious for the majority of their ICU stay.

CONCLUSION

It is feasible to record brain tissue oxygenation with NIRS in patients with septic shock. This study provides the infrastructure necessary for a larger prospective observational study to further examine the relationship between brain tissue oxygenation, physiological parameters, and acute neurological dysfunction.

Functional brain imaging in survivors of critical illness: A prospective feasibility study and exploration of the association between delirium and brain activation patterns

PURPOSE

We undertook this pilot prospective cohort investigation to examine the feasibility of functional magnetic resonance imaging (fMRI) assessments in survivors of critical illness and to analyze potential associations between delirium and brain activation patterns observed during a working memory task (N-back) at hospital discharge and 3-month follow-up.

MATERIALS AND METHODS

At hospital discharge and 3 months later, fMRI assessed subjects' functional activity during an N-back task. Multiple linear regression was used to examine associations between duration of delirium and brain activity, and elastic net regression was used to assess the relationship between brain activation patterns at 3 months and cognitive outcomes at 12 months.

RESULTS

Of 47 patients who underwent fMRI at discharge, 38 (80%) completed the protocol; of 37 who underwent fMRI at 3 months, 34 (91%) completed the protocol. At discharge, the mean (SD) percentage of correct responses on the most challenging version (the N2 version) of the N-back task was 70.4 (23.2; range of 20-100) compared with 76 (23.4; range of 33-100) at 3 months. No association was observed between delirium duration in the hospital and brain region activity in any brain region at discharge or 3 months after adjusting for relevant covariates (P values across all 11 brain regions of interest were >.25).

CONCLUSIONS

Our data support the feasibility of using fMRI in survivors of critical illness at 3-month follow-up but not at discharge. In this small study, delirium was not associated with distinct or abnormal brain activation patterns, although overall performance on a cognitive task of working memory was poorer than observed in other cohorts of individuals with medically related executive dysfunction, mild cognitive impairment, and mild traumatic brain injury.

Cognitive decline after sepsis

The modern era of sepsis management is characterised by a growing number of patients who survive in the short term and are discharged from hospital. Increasing evidence suggests that these survivors exhibit long-term neurological sequelae, particularly substantial declines in cognitive function. The exact prevalence and outcomes of these neuropsychological sequelae are unclear. The mechanisms by which sepsis induces cognitive dysfunction probably include vascular injuries and neuroinflammation that are mediated by systemic metabolism disorders and overwhelming inflammation, a disrupted blood-brain barrier, oxidative stress, and severe microglial activation, particularly within the limbic system. Interventions targeting the blood-brain barrier, glial activation, and oxidative stress have shown promise in prevention of cognitive dysfunction in various experimental models of sepsis. The next step should be to translate these favourable effects into positive clinical results.

Predictors of hippocampal atrophy in critically ill patients

BACKGROUND AND PURPOSE

Hippocampal atrophy is presumably one morphological sign of critical illness encephalopathy; however, predictors have not yet been determined.

METHODS

The data for this report derived from patients treated at the intensive care units (ICUs) of the University Hospital in Bonn in the years 2004-2006. These patients underwent structural magnetic resonance imaging 6-24 months after discharge. Volumes (intracranial, whole brain, white matter, grey matter, cerebral spinal fluid, bilateral hippocampus) were compared with healthy controls. Pro-inflammatory parameters and ICU scoring systems were explored in conjunction with brain volumes. Cut-scores were defined to differentiate patients with high from those with low inflammatory response.

RESULTS

Hippocampal and white matter volume were reduced in critically ill patients compared with healthy controls. Procalcitonin showed a very strong correlation (r = -0.903, P = 0.01) and interleukin-6 a moderate correlation (r = -0.538, P = 0.031) with hippocampal volume, but not with other brain volumes. C-reactive protein was linked to grey matter volume. There was no correlation with systemic inflammatory response syndrome criteria (body temperature, heart rate, respiratory rate, white blood cell count) or for hippocampal or whole brain volume. Furthermore, parameters representing severity of disease (APACHE II score, SOFA score, duration of stay and duration of mechanical ventilation) were not associated with hippocampal or other brain volumes.

CONCLUSIONS

This analysis suggests that high levels of procalcitonin and interleukin-6 in the blood serum of critically ill patients are associated with a high likelihood of hippocampal atrophy irrespective of the severity of disease measured by ICU scoring systems and other inflammatory parameters.

Pattern of brain injury in the acute setting of human septic shock

Background

Sepsis-associated brain dysfunction has been linked to white matter lesions (leukoencephalopathy) and ischemic stroke. Our objective was to assess the prevalence of brain lesions in septic shock patients requiring magnetic resonance imaging (MRI) for an acute neurologic change.

Method

Seventy-one septic shock patients were included in a prospective observational study. Patients underwent daily neurological examination. Brain MRI was obtained in patients who developed focal neurological deficit, seizure, coma, or delirium. Electroencephalogy was performed in case of coma, delirium, or seizure. Leukoencephalopathy was graded and considered present when white matter lesions were either confluent or diffuse. Patient outcome was evaluated at 6 months with the Glasgow Outcome Scale (GOS).

Results

We included 71 patients with median age of 65 years (56 to 76) and SAPS II at admission of 49 (38 to 60). MRI was indicated on focal neurological sign in 13 (18%), seizure in 7 (10%), coma in 33 (46%), and delirium in 35 (49%). MRI was normal in 37 patients (52%) and showed cerebral infarcts in 21 (29%), leukoencephalopathy in 15 (21%), and mixed lesions in 6 (8%). EEG malignant pattern was more frequent in patients with ischemic stroke or leukoencephalopathy. Ischemic stroke was independently associated with disseminated intravascular coagulation (DIC), focal neurologic signs, increased mortality, and worse GOS at 6 months.

Conclusions

Brain MRI in septic shock patients who developed acute brain dysfunction can reveal leukoencephalopathy and ischemic stroke, which is associated with DIC and increased mortality.

Imaging in sepsis-associated encephalopathy--insights and opportunities

Sepsis-associated encephalopathy (SAE) refers to a clinical spectrum of acute neurological dysfunction that arises in the context of sepsis. Although the pathophysiology of SAE is incompletely understood, it is thought to involve endothelial activation, blood-brain barrier leakage, inflammatory cell migration, and neuronal loss with neurotransmitter imbalance. SAE is associated with a high risk of mortality. Imaging studies using MRI and CT have demonstrated changes in the brains of patients with SAE that are also seen in disorders such as stroke. Next-generation imaging techniques such as magnetic resonance spectroscopy, diffusion tensor imaging and PET, as well as experimental imaging modalities, provide options for early identification of patients with SAE, and could aid in identification of pathophysiological processes that represent possible therapeutic targets. In this Review, we explore the recent literature on imaging in SAE, relating the findings of these studies to pathological data and experimental studies to obtain insights into the pathophysiology of sepsis-associated neurological dysfunction. Furthermore, we suggest how novel imaging technologies can be used for early-stage proof-of-concept and proof-of-mechanism translational studies, which may help to improve diagnosis in SAE.

Neuroimaging after critical illness: implications for neurorehabilitation outcome

Survivors of critical illness frequently have severe and long-lasting cognitive impairments and psychiatric disorders, which adversely affect functional outcomes including return to work, and quality of life. While data regarding cognitive outcomes has increased over the last 15 years, neuroimaging data in medical and surgical critical populations is extremely limited. The abrupt development of new significant cognitive impairments after critical illness along with abnormalities on neuroimaging suggest that critical illness results in new acquired brain injury, similar to that observed in other acquired brain injuries. Abnormalities on neuroimaging including cortical and subcortical lesions, brain atrophy, and white matter hyperintensities (WMH) which occur in widely distributed brain regions. Patients admitted to neurorehabilitation who received critical care related to their primary diagnosis may have sustained neurological injury from the nonspecific effects of their critical illness and as demonstrated in this review, generalized, non-specific neuroimaging findings may be observed and quantified. Given the high prevalence rate of cognitive impairments in this population, neuroimaging is important to help elucidate neuropathology of critical illness acquired brain injury and may be beneficial in guiding rehabilitation outcomes in this population.

[Lung protective ventilation in ARDS]

Mechanical ventilation (MV) is one of the most essential cornerstones of intensive care therapy. Although of pivotal importance for many patients suffering from respiratory insufficiency MV itself may further induce pathophysiological processes due to the mechanical stress exerted on the lungs. Particularly during one of the most distinctive forms of acute respiratory failure, acute respiratory distress syndrome (ARDS), a tremendous impairment of the lungs occurs characterized by heterogeneous damage where normally aerated areas coexist with consolidated and collapsed areas. Although MV is necessary for the treatment of severe hypoxemia it causes damage not only in the lungs but also in other organs due to a secondary inflammatory process in the lungs. To reduce these reactions an evidence-based concept of lung protective ventilation is essential.

The association between brain volumes, delirium duration, and cognitive outcomes in intensive care unit survivors: the VISIONS cohort magnetic resonance imaging study*

OBJECTIVE

Delirium duration is predictive of long-term cognitive impairment in intensive care unit survivors. Hypothesizing that a neuroanatomical basis may exist for the relationship between delirium and long-term cognitive impairment, we conducted this exploratory investigation of the associations between delirium duration, brain volumes, and long-term cognitive impairment.

DESIGN, SETTING, AND PATIENTS

A prospective cohort of medical and surgical intensive care unit survivors with respiratory failure or shock.

MEASUREMENTS

Quantitative high resolution 3-Tesla brain magnetic resonance imaging was used to calculate brain volumes at discharge and 3-month follow-up. Delirium was evaluated using the confusion assessment method for the intensive care unit; cognitive outcomes were tested at 3- and 12-month follow-up. Linear regression was used to examine associations between delirium duration and brain volumes, and between brain volumes and cognitive outcomes.

RESULTS

A total of 47 patients completed the magnetic resonance imaging protocol. Patients with longer duration of delirium displayed greater brain atrophy as measured by a larger ventricle-to-brain ratio at hospital discharge (0.76, 95% confidence intervals [0.10, 1.41]; p = .03) and at 3-month follow-up (0.62 [0.02, 1.21], p = .05). Longer duration of delirium was associated with smaller superior frontal lobe (-2.11 cm(3) [-3.89, -0.32]; p = .03) and hippocampal volumes at discharge (-0.58 cm(3) [-0.85, -0.31], p < .001)--regions responsible for executive functioning and memory, respectively. Greater brain atrophy (higher ventricle-to-brain ratio) at 3 months was associated with worse cognitive performances at 12 months (lower Repeatable Battery for the Assessment of Neuropsychological Status score -11.17 [-21.12, -1.22], p = .04). Smaller superior frontal lobes, thalamus, and cerebellar volumes at 3 months were associated with worse executive functioning and visual attention at 12 months.

CONCLUSIONS

These preliminary data show that longer duration of delirium is associated with smaller brain volumes up to 3 months after discharge, and that smaller brain volumes are associated with long-term cognitive impairment up to 12 months. We cannot, however, rule out that smaller preexisting brain volumes explain these findings.

The relationship between delirium duration, white matter integrity, and cognitive impairment in intensive care unit survivors as determined by diffusion tensor imaging: the VISIONS prospective cohort magnetic resonance imaging study*

OBJECTIVE

Evidence is emerging that delirium duration is a predictor of long-term cognitive impairment in intensive care unit survivors. Relationships between 1) delirium duration and brain white matter integrity, and 2) white matter integrity and long-term cognitive impairment are poorly understood and could be explored using magnetic resonance imaging.

DESIGN, SETTING, PATIENTS

A two-center, prospective cohort study incorporating delirium monitoring, neuroimaging, and cognitive testing in intensive care unit survivors.

MEASUREMENTS

Delirium was evaluated with the Confusion Assessment Method for the Intensive Care Unit and cognitive outcomes were tested at 3 and 12-month follow-up. Following the intensive care unit stay, fractional anisotropy, a measure of white matter integrity, was calculated quantitatively using diffusion tensor imaging with a 3-T magnetic resonance imaging scanner at hospital discharge and 3-month follow-up. We examined associations between 1) delirium duration and fractional anisotropy and 2) fractional anisotropy and cognitive outcomes using linear regression adjusted for age and sepsis.

RESULTS

A total of 47 patients with a median age of 50 yrs completed the diffusion tensor imaging-magnetic resonance imaging protocol. Greater duration of delirium (3 vs. 0 days) was associated with lower fractional anisotropy (i.e., reduced fractional anisotropy = white matter disruption) in the genu (-0.02; p = .04) and splenium (-0.01; p = .02) of the corpus callosum and anterior limb of the internal capsule (-0.02; p =.01) at hospital discharge. These associations persisted at 3 months for the genu (-0.02; p =.02) and splenium (-0.01; p = .004). Lower fractional anisotropy in the anterior limb of internal capsule at discharge and in genu of corpus callosum at three months was associated with worse cognitive scores at 3 and 12 months.

CONCLUSIONS

In this pilot investigation, delirium duration in the intensive care unit was associated with white matter disruption at both discharge and 3 months. Similarly, white matter disruption was associated with worse cognitive scores up to 12 months later. This hypothesis-generating investigation may help design future studies to explore these complex relationships in greater depth.

Predicting cognitive sequelae in survivors of critical illness with cognitive screening tests

RATIONALE

Survivors of critical illness have a high rate of cognitive impairments that may persist years after hospital discharge. Data are lacking regarding whether cognitive screening tests administered at hospital discharge can be used to predict which critically ill patients are likely to have long-term cognitive sequelae.

OBJECTIVES

This prospective study assessed whether two cognitive screening tests, the Mini-Mental State Examination (MMSE) and Mini-Cog, administered at hospital discharge, predict cognitive sequelae in survivors of critical illness 6 months after hospital discharge.

METHODS

Seventy critically ill patients completed the MMSE and Mini-Cog just before hospital discharge. Of these 70 patients, 53 completed a neuropsychological battery 6 months after hospital discharge.

MEASUREMENTS AND MAIN RESULTS

At hospital discharge, 45 patients (64%) had impaired performance on the MMSE (score < 27, mean = 24.4) and 32 (45%) on the Mini-Cog. Twenty-seven patients (39%) were impaired on both the MMSE and Mini-Cog, whereas only 20 patients (28%) had scores in the normal range on both tests. Cognitive sequelae occurred in 57% of survivors (30 of 53) at 6 months, with predominant dysfunction in the memory (38%) and executive (36%) domains. Logistic regression analyses showed that neither the MMSE nor the Mini-Cog predicted cognitive sequelae at 6 months.

CONCLUSIONS

A large number of critically ill survivors had cognitive impairments, as assessed by the MMSE and Mini-Cog, at hospital discharge. However, the MMSE and Mini-Cog scores did not predict long-term cognitive sequelae at 6-month follow-up and cannot be used as surrogate endpoints for long-term cognitive impairment.

Sepsis-associated encephalopathy: not just delirium

Sepsis is a major cause of mortality and morbidity in intensive care units. Organ dysfunction is triggered by inflammatory insults and tissue hypoperfusion. The brain plays a pivotal role in sepsis, acting as both a mediator of the immune response and a target for the pathologic process. The measurement of brain dysfunction is difficult because there are no specific biomarkers of neuronal injury, and bedside evaluation of cognitive performance is difficult in an intensive care unit. Although sepsis-associated encephalopathy was described decades ago, it has only recently been subjected to scientific scrutiny and is not yet completely understood. The pathophysiology of sepsis-associated encephalopathy involves direct cellular damage to the brain, mitochondrial and endothelial dysfunction and disturbances in neurotransmission. This review describes the most recent findings in the pathophysiology, diagnosis, and management of sepsis-associated encephalopathy and focuses on its many presentations.