The Association of Brain MRI Characteristics and Postoperative Delirium in Cardiac Surgery Patients

Analysis of influencing factors for postoperative brain injury in patients with cardiac surgery

OBJECTIVE

To identify risk factors in people with heart disease prior to undergoing cardiac surgery and to provide a prediction model.

METHODS

106 patients who underwent cardiac surgery were selected by convenience sampling method. Case-control study design was used to divide them into control and observation groups according to whether there was postoperative brain injury. General demographic data, perioperative surgery, postoperative recovery, past medical history and preoperative conditions, laboratory test indicators were collected. Univariate and multivariate Logistic regression analyses were performed to select influencing factors. A nomogram model for predicting postoperative brain injury was established.

RESULTS

Univariate Logistic regression analysis showed that age, female, stroke, diabetes mellitus, perioperative administration of dexmedetomidine, intraoperative use of cardiopulmonary bypass were related factors for postoperative brain injury(p < 0.05). Multivariate Logistic regression analysis showed that females, history of stroke, and intraoperative use of cardiopulmonary bypass were risk factors, and perioperative administration of dexmedetomidine was protective factor(p < 0.05). Nomogram model was established with an AUC of 0.847 and accuracy of 84.7%.

CONCLUSION

Preoperative stroke history and females are risk factors for brain injury after coronary artery bypass grafting under cardiopulmonary bypass, and perioperative use of dexmedetomidine is protective factor.

Preoperative brain volume loss is associated with postoperative delirium in advanced heart failure patients supported by left ventricular assist device

Delirium is a common neurological complication in patients with advanced heart failure (ADHF) following left ventricular assist device (LVAD) implantation, significantly impacting recovery. This study aimed to analyze non-contrast computed tomography (CT) scans of the brain in ADHF patients undergoing LVAD implantation to determine the association between pre-existing brain atrophy and postoperative delirium. A study involving 166 ADHF patients was conducted from March 2020 to July 2023. Non-contrast CT scans were analyzed using advanced quantitative neuroimaging techniques before implantation. The primary marker assessed was the lateral ventricle fraction (LVF), with secondary markers including cortical gray matter fraction (cGMF), white matter fraction (WMF), basal ganglia fraction (BGF), and thalamus fraction (TLF). A total of 56 patients (33%) experienced postoperative delirium within two weeks of implantation. Patients with delirium were older and exhibited greater brain atrophy, indicated by higher LVF and lower cGMF, WMF, BGF, and TLF values. The occurrence of delirium was strongly associated with age, and ventricular enlargement, primarily in the lateral ventricles. LVF effectively predicted delirium development, regardless of age. Preoperative brain volumetric analysis, particularly of the lateral ventricles, may be crucial in identifying patients at risk for postoperative delirium, enhancing postoperative management, and improving outcomes for LVAD recipients.

The Pathophysiology and Biomarkers of Delirium

Delirium is a major disturbance in the mental state characterized by fluctuations in arousal, deficits in attention, distorted perception, and disruptions in memory and cognitive processing. Delirium affects approximately 18% to 25% of hospital inpatients, with even higher rates observed during critical illness. To develop therapies to shorten the duration and limit the adverse effects of delirium, it is important to understand the mechanisms underlying its presentation. Neuroimaging modalities such as magnetic resonance imaging (MRI), positron emission tomography, functional MRI, and near-infrared spectroscopy point to global atrophy, white matter changes, and disruptions in cerebral blood flow, oxygenation, metabolism, and connectivity as key correlates of delirium pathogenesis. Electroencephalography demonstrates generalized slowing of normal background activity, with pathologic decreases in variability of oscillatory patterns and disruptions in functional connectivity among specific brain regions. Elevated serum biomarkers of inflammation, including interleukin-6, C-reactive protein, and S100B, suggest a role of dysregulated inflammatory processes and cellular metabolism, particularly in perioperative and sepsis-related delirium. Emerging animal models that can mimic delirium-like clinical states will reveal further insights into delirium pathophysiology. The combination of clinical and basic science methods of exploring delirium shows great promise in elucidating its underlying mechanisms and revealing potential therapeutic targets.

The Relationship between Delirium and Dementia

Delirium and dementia are common causes of cognitive impairment in older adults. They are distinct but interrelated. Delirium, an acute confusional state, has been linked to the chronic and progressive loss of cognitive ability seen in dementia. Individuals with dementia are at higher risk for delirium, and delirium itself is a risk factor for incident dementia. Additionally, delirium in individuals with dementia can hasten underlying cognitive decline. In this review, we summarize recent literature linking these conditions, including epidemiological, clinicopathological, neuroimaging, biomarker, and experimental evidence supporting the intersection between these conditions. Strategies for evaluation and diagnosis that focus on distinguishing delirium from dementia in clinical settings and recommendations for delirium prevention interventions for patients with dementia are presented. We also discuss studies that provide evidence that delirium may be a modifiable risk factor for dementia and consider the impact of delirium prevention interventions on long-term outcomes.

Postoperative cognitive disorders and delirium in gynecologic surgery: Which surgery and anesthetic techniques to use to reduce the risk?

Despite their general good health, an increasing proportion of elderly individuals require surgery due to an increase in average lifespan. However, because of their increased vulnerability, these patients need to be handled carefully to make sure that surgery does not cause more harm than good. Age-related postoperative cognitive disorders (POCD) and postoperative delirium (POD), two serious consequences that are marked by adverse neuropsychologic alterations after surgery, are particularly dangerous for the elderly. In the context of gynecologic procedures, POCD and POD are examined in this narrative review. The main question is how to limit the rates of POCD and POD in older women undergoing gynecologic procedures by maximizing the risk-benefit balance. Three crucial endpoints are considered: (1) surgical procedures to lower the rates of POCD and POD, (2) anesthetic techniques to lessen the occurrence and (3) the identification of individuals at high risk for post-surgery cognitive impairments. Risks associated with laparoscopic gynecologic procedures include the Trendelenburg posture and CO2 exposure during pneumoperitoneum, despite statistical similarities in POD and POCD frequency between laparoscopic and laparotomy techniques. Numerous risk factors are associated with surgical interventions, such as blood loss, length of operation, and position holding, all of which reduce the chance of complications when they are minimized. In order to emphasize the essential role that anesthesia and surgery play in patient care, anesthesiologists are vital in making sure that anesthesia is given as sparingly and quickly as feasible. In addition, people who are genetically predisposed to POCD may be more susceptible to the disorder. The significance of a thorough strategy combining surgical and anesthetic concerns is highlighted in this article, in order to maximize results for senior patients having gynecologic surgery.

Infarct-related structural disconnection and delirium in surgical aortic valve replacement patients

OBJECTIVE

Although acute brain infarcts are common after surgical aortic valve replacement (SAVR), they are often unassociated with clinical stroke symptoms. The relationship between clinically "silent" infarcts and in-hospital delirium remains uncertain; obscured, in part, by how infarcts have been traditionally summarized as global metrics, independent of location or structural consequence. We sought to determine if infarct location and related structural connectivity changes were associated with postoperative delirium after SAVR.

METHODS

A secondary analysis of a randomized multicenter SAVR trial of embolic protection devices (NCT02389894) was conducted, excluding participants with clinical stroke or incomplete neuroimaging (N = 298; 39% female, 7% non-White, 74 ± 7 years). Delirium during in-hospital recovery was serially screened using the Confusion Assessment Method. Parcellation and tractography atlas-based neuroimaging methods were used to determine infarct locations and cortical connectivity effects. Mixed-effect, zero-inflated gaussian modeling analyses, accounting for brain region-specific infarct characteristics, were conducted to examine for differences within and between groups by delirium status and perioperative neuroprotection device strategy.

RESULTS

23.5% participants experienced postoperative delirium. Delirium was associated with significantly increased lesion volumes in the right cerebellum and temporal lobe white matter, while diffusion weighted imaging infarct-related structural disconnection (DWI-ISD) was observed in frontal and temporal lobe regions (p-FDR < 0.05). Fewer brain regions demonstrated DWI-ISD loss in the suction-based neuroprotection device group, relative to filtration-based device or standard aortic cannula.

INTERPRETATION

Structural disconnection from acute infarcts was greater in patients who experienced postoperative delirium, suggesting that the impact from covert perioperative infarcts may not be as clinically "silent" as commonly assumed.

Preclinical and translational models for delirium: Recommendations for future research from the NIDUS delirium network

Delirium is a common, morbid, and costly syndrome that is closely linked to Alzheimer's disease (AD) and AD-related dementias (ADRD) as a risk factor and outcome. Human studies of delirium have advanced our knowledge of delirium incidence and prevalence, risk factors, biomarkers, outcomes, prevention, and management. However, understanding of delirium neurobiology remains limited. Preclinical and translational models for delirium, while challenging to develop, could advance our knowledge of delirium neurobiology and inform the development of new prevention and treatment approaches. We discuss the use of preclinical and translational animal models in delirium, focusing on (1) a review of current animal models, (2) challenges and strategies for replicating elements of human delirium in animals, and (3) the utility of biofluid, neurophysiology, and neuroimaging translational markers in animals. We conclude with recommendations for the development and validation of preclinical and translational models for delirium, with the goal of advancing awareness in this important field.

Postoperative delirium is associated with grey matter brain volume loss

Delirium is associated with long-term cognitive dysfunction and with increased brain atrophy. However, it is unclear whether these problems result from or predisposes to delirium. We aimed to investigate preoperative to postoperative brain changes, as well as the role of delirium in these changes over time. We investigated the effects of surgery and postoperative delirium with brain MRIs made before and 3 months after major elective surgery in 299 elderly patients, and an MRI with a 3 months follow-up MRI in 48 non-surgical control participants. To study the effects of surgery and delirium, we compared brain volumes, white matter hyperintensities and brain infarcts between baseline and follow-up MRIs, using multiple regression analyses adjusting for possible confounders. Within the patients group, 37 persons (12%) developed postoperative delirium. Surgical patients showed a greater decrease in grey matter volume than non-surgical control participants [linear regression: B (95% confidence interval) = -0.65% of intracranial volume (-1.01 to -0.29, P < 0.005)]. Within the surgery group, delirium was associated with a greater decrease in grey matter volume [B (95% confidence interval): -0.44% of intracranial volume (-0.82 to -0.06, P = 0.02)]. Furthermore, within the patients, delirium was associated with a non-significantly increased risk of a new postoperative brain infarct [logistic regression: odds ratio (95% confidence interval): 2.8 (0.7-11.1), P = 0.14]. Our study was the first to investigate the association between delirium and preoperative to postoperative brain volume changes, suggesting that delirium is associated with increased progression of grey matter volume loss.

Perioperative considerations in patients with chemotherapy-induced cognitive impairment: a narrative review

Patients with cancer may suffer from a decline in their cognitive function after various cancer therapies, including surgery, radiation, and chemotherapy, and in some cases, this decline in cognitive function persists even years after completion of treatment. Chemobrain or chemotherapy-induced cognitive impairment, a well-established clinical syndrome, has become an increasing concern as the number of successfully treated cancer patients has increased significantly. Chemotherapy-induced cognitive impairment can originate from direct neurotoxicity, neuroinflammation, and oxidative stress, resulting in alterations in grey matter volume, white matter integrity, and brain connectivity. Surgery has been associated with exacerbating the inflammatory response associated with chemotherapy and predisposes patients to develop postoperative cognitive dysfunction. As the proportion of patients living longer after these therapies increases, the magnitude of impact and growing concern of post-treatment cognitive dysfunction in these patients has also come to the fore. We review the clinical presentation, potential mechanisms, predisposing factors, diagnostic methods, neuropsychological testing, and imaging findings of chemotherapy-induced cognitive impairment and its intersection with postoperative cognitive dysfunction.

The inter-relationship between delirium and dementia: the importance of delirium prevention

Delirium and dementia are two frequent causes of cognitive impairment among older adults and have a distinct, complex and interconnected relationship. Delirium is an acute confusional state characterized by inattention, cognitive dysfunction and an altered level of consciousness, whereas dementia is an insidious, chronic and progressive loss of a previously acquired cognitive ability. People with dementia have a higher risk of developing delirium than the general population, and the occurrence of delirium is an independent risk factor for subsequent development of dementia. Furthermore, delirium in individuals with dementia can accelerate the trajectory of the underlying cognitive decline. Delirium prevention strategies can reduce the incidence of delirium and associated adverse outcomes, including falls and functional decline. Therefore, delirium might represent a modifiable risk factor for dementia, and interventions that prevent or minimize delirium might also reduce or prevent long-term cognitive impairment. Additionally, understanding the pathophysiology of delirium and the connection between delirium and dementia might ultimately lead to additional treatments for both conditions. In this Review, we explore mechanisms that might be common to both delirium and dementia by reviewing evidence on shared biomarkers, and we discuss the importance of delirium recognition and prevention in people with dementia.

In this Review, Fong and Inouye explore mechanisms that might be common to both delirium and dementia. They present delirium as a possible modifiable risk factor for dementia and discuss the importance of delirium prevention strategies in reducing this risk.

Delirium and dementia are frequent causes of cognitive impairment among older adults and have a distinct, complex and interconnected relationship.

Delirium prevention strategies have been shown to reduce not only the incidence of delirium but also the incidence of adverse outcomes associated with delirium such as falls and functional decline.

Adverse outcomes associated with delirium, such as the onset of dementia symptoms in individuals with preclinical dementia, and/or the acceleration of cognitive decline in individuals with dementia might also be delayed by the implementation of delirium prevention strategies.

Evidence regarding the association of systemic inflammatory and neuroinflammatory biomarkers with delirium is variable, possibly as a result of co-occurring dementia pathology or disruption of the blood–brain barrier.

Alzheimer disease pathology, even prior to the onset of symptoms, might have an effect on delirium risk, with potential mechanisms including neuroinflammation and gene–protein interactions with the APOE ε4 allele.

Novel strategies, including proteomics, multi-omics, neuroimaging, transcranial magnetic stimulation and EEG, are beginning to reveal how changes in cerebral blood flow, spectral power and connectivity can be associated with delirium; further work is needed to expand these findings to patients with delirium superimposed upon dementia.

Silent Brain Infarction, Delirium, and Cognition in Three Invasive Cardiovascular Procedures: a Systematic Review

Silent brain infarctions (SBIs) are brain lesions noted on neuroimaging that are not associated with clinical symptoms. SBIs are associated with a number of vascular risk factors and are common following invasive cardiovascular procedures such as atrial fibrillation (AF) ablation, coronary artery bypass graft (CABG), and transcatheter aortic valve replacement (TAVR). Although not eliciting signs of clinical stroke, SBIs are associated with increased frailty, and motor and mood features. Less is known, however, about the relationship between SBI, cognition, and delirium following invasive cardiac procedures and most investigations into these relationships have been reported in large-scale epidemiological studies. In the current paper, we conducted a systematic review to evaluate evidence of a relationship between SBI, delirium, and cognitive decline following CABG, AF ablation, and TAVR. Twenty studies met inclusion criteria. In general, our review identified conflicting results for each cardiac procedure, with some studies suggesting a relationship between SBI, cognitive impairment, and delirium, whereas others showed no relationship between SBI, cognitive impairment, and delirium. Potential reasons for this discrepancy as well as suggestions for future research are discussed.

Silent cerebral ischemia detected by magnetic resonance imaging can predict postoperative delirium after total arch replacement for aneurysm

Objective

To identify whether preoperative magnetic resonance imaging findings of the brain can predict postoperative delirium in patients who undergo arch replacement for aneurysms.

Methods

Overall, 193 patients who underwent aortic replacement for the first time at a single institution between April 2014 and September 2020 were enrolled in this retrospective study. After we excluded patients with acute aortic dissection, no preoperative magnetic resonance imaging findings of the brain, and postoperative cerebral infarction, 50 patients were included and divided into 2 groups, according to their confusion scale results: postoperative delirium (group D) and nonpostoperative delirium (group ND). Preoperative magnetic resonance imaging findings of the brain were classified into lacunar stroke, periventricular hyperintensity, and deep subcortical white matter hyperintensity groups; the latter 2 groups were further classified based on the Fazekas scale, grade 0 to 3.

Results

There were 23 patients (46%) in group D and 27 (54%) in group ND. The mean age was significantly greater in group D than in group ND (75 vs 70 years; P = .007). The mean operative time was significantly longer in group D than in group ND (447 vs 384 minutes; P = .024). As for preoperative magnetic resonance imaging findings of the brain, there were significantly more lacunar stroke cases in group D than in group ND (P = .027). In multivariable logistic regression with stepwise selection, high-grade periventricular hyperintensity was significantly related to postoperative delirium (odds ratio, 9.38; 95% confidence interval, 1.55-56.56; P = .015).

Conclusions

Silent cerebral ischemia detected by preoperative magnetic resonance imaging of the brain was a significant risk factor for postoperative delirium.

Brain Network Dysfunction in Poststroke Delirium and Spatial Neglect: An fMRI Study

BACKGROUND AND PURPOSE

Delirium, an acute reduction in cognitive functioning, hinders stroke recovery and contributes to cognitive decline. Right-hemisphere stroke is linked with higher delirium incidence, likely, due to the prevalence of spatial neglect (SN), a right-brain disorder of spatial processing. This study tested if symptoms of delirium and SN after right-hemisphere stroke are associated with abnormal function of the right-dominant neural networks specialized for maintaining attention, orientation, and arousal.

METHODS

Twenty-nine participants with right-hemisphere ischemic stroke undergoing acute rehabilitation completed delirium and SN assessments and functional neuroimaging scans. Whole-brain functional connectivity of 4 right-hemisphere seed regions in the cortical-subcortical arousal and attention networks was assessed for its relationship to validated SN and delirium severity measures.

RESULTS

Of 29 patients, 6 (21%) met the diagnostic criteria for delirium and 16 (55%) for SN. Decreased connectivity of the right basal forebrain to brain stem and basal ganglia predicted more severe SN. Increased connectivity of the arousal and attention network regions with the parietal, frontal, and temporal structures in the unaffected hemisphere was also found in more severe delirium and SN.

CONCLUSIONS

Delirium and SN are associated with decreased arousal network activity and an imbalance of cortico-subcortical hemispheric connectivity. Better understanding of neural correlates of poststroke delirium and SN will lead to improved neuroscience-based treatment development for these disorders. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03349411.

Neuropsychiatric symptoms associated with cerebral small vessel disease: a systematic review and meta-analysis

BACKGROUND

Cerebral small vessel disease, a common cause of vascular dementia, is often considered clinically silent before dementia or stroke become apparent. However, some individuals have subtle symptoms associated with acute MRI lesions. We aimed to determine whether neuropsychiatric and cognitive symptoms vary according to small vessel disease burden.

METHODS

In this systematic review and meta-analysis, we searched MEDLINE, EMBASE, and PsycINFO for articles published in any language from database inception to Jan 24, 2020. We searched for studies assessing anxiety, apathy, delirium, emotional lability, fatigue, personality change, psychosis, dementia-related behavioural symptoms or cognitive symptoms (including subjective memory complaints), and radiological features of cerebral small vessel disease. We extracted reported odds ratios (OR), standardised mean differences (SMD), and correlations, stratified outcomes by disease severity or symptom presence or absence, and pooled data using random-effects meta-analyses, reporting adjusted findings when possible. We assessed the bias on included studies using the Risk of Bias for Non-randomized Studies tool. This study is registered with PROSPERO, CRD42018096673.

FINDINGS

Of 7119 papers identified, 81 studies including 79 cohorts in total were eligible for inclusion (n=21 730 participants, mean age 69·2 years). Of these 81 studies, 45 (8120 participants) reported effect estimates. We found associations between worse white matter hyperintensity (WMH) severity and apathy (OR 1·41, 95% CI 1·05-1·89) and the adjusted SMD in apathy score between WMH severities was 0·38 (95% CI 0·15-0·61). Worse WMH severity was also associated with delirium (adjusted OR 2·9, 95% CI 1·12-7·55) and fatigue (unadjusted OR 1·63, 95% CI 1·20-2·22). WMHs were not consistently associated with subjective memory complaints (OR 1·34, 95% CI 0·61-2·94) and unadjusted SMD for WMH severity between these groups was 0·08 (95% CI -0·31 to 0·47). Anxiety, dementia-related behaviours, emotional lability, and psychosis were too varied or sparse for meta-analysis; these factors were reviewed narratively. Overall heterogeneity varied from 0% to 79%. Only five studies had a low risk of bias across all domains.

INTERPRETATION

Apathy, fatigue, and delirium associated independently with worse WMH, whereas subjective cognitive complaints did not. The association of anxiety, dementia-related behaviours, emotional lability, and psychosis with cerebral small vessel disease require further investigation. These symptoms should be assessed longitudinally to improve early clinical detection of small vessel disease and enable prevention trials to happen early in the disease course, long before cognition declines.

FUNDING

Chief Scientist Office of the Scottish Government, UK Dementia Research Institute, Fondation Leducq, Stroke Association Garfield-Weston Foundation, Alzheimer's Society, and National Health Service Research Scotland.

Clinical utility of brain computed tomography in prediction of post-stroke delirium

Delirium is a common and serious complication of stroke. Early prediction of delirium is important for preventive strategies and close monitoring of high-risk patients. Pre-existing degenerative and vascular changes in the brain could predispose to delirium. We aimed to determine if computed tomography (CT)-based indices could provide additional information about a risk of stroke-associated delirium beyond easiest-to-access clinical predictors. Using semi-quantitative scales (global cortical atrophy, age-related white matter changes, and Scheltens scale), we assessed global and regional brain atrophy and white matter changes in 88 stroke patients with delirium and 142 patients without delirium matched for age and stroke severity. Patients with delirium had greater global and local brain atrophy (the right temporal region, the left parieto-occipital region, the right frontal and occipital horn, and the right and left temporal horn) than patients without delirium. Scores of white matter changes did not differ between groups with exception of greater white matter damage in the right parieto-occipital area in patients with delirium. The discriminatory properties of studied radiological indices were modest (areas under receiver operator curves: 0.58-0.64). CT-based indices of brain atrophy and white matter changes do not provide additional information about a risk of post-stroke delirium beyond the most important clinical predictors.

Perioperative covert stroke in patients undergoing coronary artery bypass graft surgery

Objectives

Covert stroke is a complication of coronary artery bypass graft surgery that is increasingly recognized as a serious problem. In noncardiac surgery settings, covert stroke is associated with the development of delirium, long-term cognitive decline, and future clinical stroke. Therefore, we sought to determine the feasibility of conducting a large, prospective cohort study of the influence of covert stroke on neurocognitive outcomes in patients undergoing coronary artery bypass graft surgery.

Methods

NeuroVISION Cardiac pilot was a prospective cohort study enrolling patients aged ≥21 years undergoing isolated coronary artery bypass graft surgery to receive diffusion-weighted magnetic resonance imaging of the brain after surgery to identify patients with covert stroke. Patients were screened for postoperative delirium in-hospital and were administered questionnaires of cognitive and global function (once before and twice after surgery). Regional cerebral oxygen saturation was recorded during surgery using near-infrared spectroscopy.

Results

Between March 27, 2017, and February 11, 2018, 50 of 66 patients enrolled (76%) completed the brain magnetic resonance imaging (1 patient per week). Among the 49 patients included in the analysis, 19 (39%; 95% confidence interval, 26%-53%) experienced perioperative covert stroke and 3 (6%) had a clinical stroke within 30 days of surgery. Postoperative delirium occurred in 5 (26%) patients with covert stroke and in 3 (10%) patients who did not experience covert stroke.

Conclusions

The NeuroVISION Cardiac pilot study established the feasibility of conducting a large, prospective cohort study of the determinants and consequences of covert stroke in patients undergoing coronary artery bypass graft surgery.

A Systematic Review of Delirium Biomarkers and Their Alignment with the NIA-AA Research Framework

OBJECTIVES

To identify whether delirium biomarkers aligned with the National Institute on Aging-Alzheimer's Association (NIA-AA) research framework, a conceptual model that describes the use of diagnostic biomarkers for Alzheimer's disease and other related dementias (ADRD).

DESIGN

Systematic review following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

SETTING

Acute care and outpatient settings.

PARTICIPANTS

Adults diagnosed with delirium.

METHODS AND MEASUREMENTS

MEDLINE, PsycInfo, Embase, and the Cochrane Library were searched for English-language studies published from January 2010 to February 2020. Studies included adults older than 18 years, identified delirium with a standardized assessment tool, and measured an ADRD biomarker. Independent reviewers determined whether an association between delirium and ADRD biomarker was found, the quality of biomarker data based on the REMARK (REporting recommendations for tumor MARKer prognostic studies) checklist, and the study bias based on the Newcastle-Ottawa Scale.

RESULTS

A total of 61,256 citations were identified; 113 studies were included. Most studies did not examine amyloid, tau, or neurodegeneration biomarkers. Delirium may be associated with neurodegeneration biomarkers, but few to no studies found an association with amyloid and tau biomarkers. Delirium was not consistently associated with inflammatory biomarkers. The quality of biomarker data was moderate, and the risk of bias was moderate to high. Studies often did not collect prehospital and posthospital cognitive data.

CONCLUSION

Most delirium diagnostic biomarker studies did not measure amyloid, tau, and/or neurodegenerative biomarkers, making characterization of the relationship between delirium and ADRD difficult. Future delirium biomarker diagnostic studies could improve the understanding of pathophysiologic links between delirium with other conditions affecting cognition.

Evaluating Mechanisms of Postoperative Delirium and Cognitive Dysfunction Following Elective Spine Surgery in Elderly Patients (CONFESS): Protocol for a Prospective Observational Trial

Background

Elderly people are at particular high risk for postoperative delirium (POD) following spine surgery, which is associated with longer hospital stays, higher costs, risk for delayed complications, long-term care dependency, and cognitive dysfunction (POCD). It is insufficiently understood which mechanisms and risk factors contribute to the development of POD and POCD following these major but plannable surgeries.

Objective

This study aims to identify modifiable risk factors in spine surgery. A better understanding thereof would help adapt medical management and surgical strategies to individual risk profiles.

Methods

This is a single-center observational study jointly conducted by the departments of neurosurgery, neurology, and anesthesiology at a tertiary care hospital in Germany. All patients aged 60 years and older presenting to the neurosurgery outpatient clinic or ward for elective spine surgery are screened for eligibility. Exclusion criteria include presence of neurodegenerative or history of psychiatric disease and medication with significant central nervous system activity (eg, antidepressants, antipsychotics, sedatives). Surgical and anesthetic procedures including duration of surgery as primary end point of this study are thoroughly documented. All patients are furthermore evaluated for their preoperative cognitive abilities by a number of tests, including the Consortium to Establish a Registry for Alzheimer's Disease Plus test battery. Physical, mental, and social health and well-being are assessed using the Patient-Reported Outcome Measurement Information System Profile 29 and Hospital Anxiety and Depression Scale. Patients additionally receive preoperative cerebrovascular ultrasound and structural and functional brain imaging. The immediate postoperative period includes screening for POD using the Nursing Delirium Screening Scale and validation through Diagnostic and Statistical Manual of Mental Disorders, 5th Edition, criteria. We furthermore investigate markers of (neuro)inflammation (eg, interleukins, C-reactive protein, tumor necrosis factor alpha). Preoperative examinations are repeated 3 months postoperatively to investigate the presence of POCD and its mechanisms. Statistical analyses will compare delirious and nondelirious patients for predictors of immediate (POD) and delayed (POCD) cognitive dysfunction.

Results

This is the first study to prospectively evaluate risk factors for POD and POCD in spine surgery. Recruitment is ongoing, and data collection is estimated to be finished with the inclusion of 200 patients by mid-2020.

Conclusions

The identification of mechanisms, possibly common, underlying POD and POCD would be a major step toward defining effective interventional strategies early in or even before the postoperative period, including the adaptation of surgical strategies to individual risk profiles.

Trial Registration

ClinicalTrials.gov NCT03486288; https://clinicaltrials.gov/ct2/show/NCT03486288

Cerebral Small Vessel, But Not Large Vessel Disease, Is Associated With Impaired Cerebral Autoregulation During Cardiopulmonary Bypass: A Retrospective Cohort Study

BACKGROUND

Impaired cerebral blood flow (CBF) autoregulation during cardiopulmonary bypass (CPB) is associated with stroke and other adverse outcomes. Large and small arterial stenosis is prevalent in patients undergoing cardiac surgery. We hypothesize that large and/or small vessel cerebral arterial disease is associated with impaired cerebral autoregulation during CPB.

METHODS

A retrospective cohort analysis of data from 346 patients undergoing cardiac surgery with CPB enrolled in an ongoing prospectively randomized clinical trial of autoregulation monitoring were evaluated. The study protocol included preoperative transcranial Doppler (TCD) evaluation of major cerebral artery flow velocity by a trained vascular technician and brain magnetic resonance imaging (MRI) between postoperative days 3 and 5. Brain MRI images were evaluated for chronic white matter hyperintensities (WMHI) by a vascular neurologist blinded to autoregulation data. "Large vessel" cerebral vascular disease was defined by the presence of characteristic TCD changes associated with stenosis of the major cerebral arteries. "Small vessel" cerebral vascular disease was defined based on accepted scoring methods of WMHI. All patients had continuous TCD-based autoregulation monitoring during surgery.

RESULTS

Impaired autoregulation occurred in 32.4% (112/346) of patients. Preoperative TCD demonstrated moderate-severe large vessel stenosis in 67 (25.2%) of 266 patients with complete data. In adjusted analysis, female sex (odds ratio [OR], 0.46; 95% confidence interval [CI], 0.25-0.86; P = .014) and higher average temperature during CPB (OR, 1.23; 95% CI, 1.02-1.475; P = .029), but not moderate-severe large cerebral arterial stenosis (P = .406), were associated with impaired autoregulation during CPB. Of the 119 patients with available brain MRI data, 42 (35.3%) demonstrated WMHI. The presence of small vessel cerebral vascular disease was associated with impaired CBF autoregulation (OR, 3.25; 95% CI, 1.21-8.71; P = .019) after adjustment for age, history of peripheral vascular disease, preoperative hemoglobin level, and preoperative treatment with calcium channel blocking drugs.

CONCLUSIONS

These data confirm that impaired CBF autoregulation is prevalent during CPB predisposing affected patients to brain hypoperfusion or hyperperfusion with low or high blood pressure, respectively. Small vessel, but not large vessel, cerebral vascular disease, male sex, and higher average body temperature during CPB appear to be associated with impaired autoregulation.

Cortical and subcortical changes in resting-state functional connectivity before and during an episode of postoperative delirium

OBJECTIVE

Delirium is an acute brain failure related to uncertain problems in neural connectivity, including aberrant functional interactions between remote cortical regions. This study aimed to elucidate the underlying neural mechanisms of delirium by clarifying the changes in resting-state functional connectivity induced by postoperative delirium using imaging data scanned before and after surgery.

METHOD

Fifty-eight patients with a femoral neck fracture were preoperatively scanned using resting-state functional magnetic resonance imaging. Twenty-five patients developed postoperative delirium, and 14 of those had follow-up scans during delirium. Eighteen patients without delirium completed follow-up scans 5 or 6 days after surgery. We assessed group differences in voxel-based connectivity, in which the seeds were the posterior cingulate cortex, medial prefrontal cortex and 11 subcortical regions. Connections between the subcortical regions were also examined.

RESULTS

The results showed four major findings during delirium. Both the posterior cingulate cortex and medial prefrontal cortex were strongly connected to the dorsolateral prefrontal cortex. The posterior cingulate cortex had hyperconnectivity with the inferior parietal lobule, whereas the medial prefrontal cortex had hyperconnectivity with the frontopolar cortex and hypoconnectivity with the superior frontal gyrus. Connectivity of the striatum with the anterior cingulate cortex and insula was increased. Disconnections were found between the lower subcortical regions including the neurotransmitter origins and the striatum/thalamus in the upper level.

CONCLUSIONS

Our findings suggest that cortical dysfunction during delirium is characterized by a diminution of the anticorrelation between the default mode network and task-positive regions, excessive internal connections in the posterior default mode network and a complex imbalance of internal connectivity in the anterior default mode network. These dysfunctions can be attributed to the loss of reciprocity between the default mode network and central executive network associated with defective function in the salience network, which might be closely linked to aberrant subcortical neurotransmission-related connectivity and striato-cortical connectivity.

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.

A systematic review of neuroimaging in delirium: predictors, correlates and consequences

OBJECTIVE

Neuroimaging advances our understanding of delirium pathophysiology and its consequences. A previous systematic review identified 12 studies (total participants N = 764, delirium cases N = 194; years 1989-2007) and found associations with white matter hyperintensities (WMH) and cerebral atrophy. Our objectives were to perform an updated systematic review of neuroimaging studies in delirium published since January 2006 and summarise the available literature on predictors, correlates or outcomes.

METHODS

Studies were identified by keyword and MeSH-based electronic searches of EMBASE, MEDLINE and PsycINFO combining terms for neuroimaging, brain structure and delirium. We included neuroimaging studies of delirium in adults using validated delirium assessment methods.

RESULTS

Thirty-two studies (total N = 3187, delirium N = 1086) met the inclusion criteria. Imaging included magnetic resonance imaging (MRI; N = 9), computed tomography (N = 4), diffusion tensor imaging (N = 3), transcranial Doppler (N = 5), near infrared spectroscopy (N = 5), functional-MRI (N = 2), single photon emission computed tomography (N = 1), proton MRI spectroscopy (N = 1), arterial spin-labelling MRI (N = 1) and 2-¹³ fluoro-2-deoxyglucose positron emission tomography (N = 1). Despite heterogeneity in study design, delirium was associated with WMH, lower brain volume, atrophy, dysconnectivity, impaired cerebral autoregulation, reduced blood flow and cerebral oxygenation and glucose hypometabolism. There was evidence of long-term brain changes following intensive care unit delirium.

CONCLUSIONS

Neuroimaging is now used more widely in delirium research due to advances in technology. However, imaging delirious patients presents challenges leading to methodological limitations and restricted generalisability. The findings that atrophy and WMH burden predict delirium replicates findings from the original review, while advanced techniques have identified other substrates and mechanisms that warrant further investigation.

Neurocognitive Function after Cardiac Surgery: From Phenotypes to Mechanisms

For half a century, it has been known that some patients experience neurocognitive dysfunction after cardiac surgery; however, defining its incidence, course, and causes remains challenging and controversial. Various terms have been used to describe neurocognitive dysfunction at different times after cardiac surgery, ranging from "postoperative delirium" to "postoperative cognitive dysfunction or decline." Delirium is a clinical diagnosis included in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). Postoperative cognitive dysfunction is not included in the DSM-5 and has been heterogeneously defined, though a recent international nomenclature effort has proposed standardized definitions for it. Here, the authors discuss pathophysiologic mechanisms that may underlie these complications, review the literature on methods to prevent them, and discuss novel approaches to understand their etiology that may lead to novel treatment strategies. Future studies should measure both delirium and postoperative cognitive dysfunction to help clarify the relationship between these important postoperative complications.

Safety and effectiveness of selective carotid angioplasty prior to cardiac surgery: a single-centre matched case-control study

OBJECTIVES

Reducing the rate of postoperative stroke after cardiac surgery remains challenging, especially in patients with occlusive cerebrovascular disease. Angioplasty in all patients with high-grade carotid artery stenosis has not been shown to be effective in reducing the post-surgical stroke rate. In this study, we present the initial results of a different approach using selective carotid angioplasty only in patients with poor intracranial collaterals.

METHODS

We conducted a single-centre study to assess the safety of this procedure. The postangioplasty complication rate of the study group was compared to that of patients who were scheduled for symptomatic carotid artery angioplasty. To determine the effectiveness of this procedure, the post-cardiac surgery complication rate of the study group was compared with that of the matched case controls.

RESULTS

Twenty-two patients were treated with selective carotid angioplasty without developing persistent major neurological complications. All patients except 1 patient subsequently underwent surgery without developing persistent major neurological disabilities. Two patients died of cardiogenic shock within 30 days.

CONCLUSIONS

Selective carotid angioplasty prior to cardiac surgery in patients with a presumed high risk of stroke was relatively safe and effective in this study group. Although this strategy does not prevent stroke in these high-risk patients, data suggest that this approach shifts the postoperative type of stroke from a severe haemodynamic stroke towards a minor embolic stroke with favourable neurological outcomes. Larger studies are needed to determine whether this strategy can effectively eliminate the occurrence of haemodynamic stroke after cardiac surgery.

Disruption of the ascending arousal system and cortical attention networks in post-stroke delirium and spatial neglect

Delirium is an acute attention and cognitive dysfunction, adversely affecting functional outcomes and mortality. As many as half of hospitalized right brain stroke survivors may develop delirium. Further, about 50% of right stroke patients experience spatial neglect, impairing safety and recovery. In this review we explore the brain mechanisms, which may explain the high incidence of delirium and spatial neglect after right-brain stroke. We suggest that brain networks for spatial attention and arousal, composed of ascending projections from the midbrain nuclei and integrating dorsal and ventral cortical and limbic components, may underlie impairments in delirium and spatial neglect. We propose that lateralized deficits in spatial neglect may arise because cortical and limbic components of these functional networks are disproportionally impaired by right-brain strokes, and that spatial neglect may lower the threshold for developing delirium. An improved understanding of the brain basis of delirium and spatial neglect could provide a critical biomarker for initiating preventive care in stroke patients at high risk of hospital morbidity and loss of independence.

MRI Markers of Neurodegenerative and Neurovascular Changes in Relation to Postoperative Delirium and Postoperative Cognitive Decline

Postoperative delirium (POD) and postoperative cognitive decline (POCD) are common in elderly patients. The aim of the present review was to explore the association of neurodegenerative and neurovascular changes with the occurrence of POD and POCD. Fifteen MRI studies were identified by combining multiple search terms for POD, POCD, and brain imaging. These studies described a total of 1,422 patients and were all observational in design. Neurodegenerative changes (global and regional brain volumes) did not show a consistent association with the occurrence of POD (four studies) or POCD (two studies). In contrast, neurovascular changes (white matter hyperintensities and cerebral infarcts) were more consistently associated with the occurrence of POD (seven studies) and POCD (five studies). In conclusion, neurovascular changes appear to be consistently associated with the occurrence of POD and POCD, and may identify patients at increased risk of these conditions. Larger prospective studies are needed to study the consistency of these findings and to unravel the underlying pathophysiological mechanisms.