White-matter hyperintensities predict delirium after cardiac surgery

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.

Predictiveness of preoperative laboratory values for postoperative delirium

Background

Postoperative delirium (POD) is a common postoperative complication, especially in patients over 60 years, with an incidence ranging from 15% to 50%. In most cases, POD manifests in the first 5 days after surgery. Multiple contributing risk factors for POD have been detected. Besides the predisposing factors such as higher age, cognitive impairment, high blood pressure, atrial fibrillation, and past stroke, pathophysiological mechanisms like neuroinflammation are also considered as contributing factors.

Methods

In a subanalysis of the "PRe- Operative  Prediction of postoperative  DElirium by appropriate  SCreening" (PROPDESC) study, the preoperative laboratory values of sodium, potassium, total protein, hemoglobin concentration (Hgb), and white blood cells as well as the biomarkers creatinine, HbA1c, NT-pro-BNP, high sensitive Troponin T (hsTnT), and C-reactive protein (CRP) were assessed to investigate a possible relationship to the occurrence of POD.

Results

After correction for age, physical status classification, surgery risk after Johns Hopkins, and operative discipline (cardiac surgery vs. noncardiac surgery), male patients with a Hgb <13 g/dL had significantly higher odds for POD (p = 0.025). Furthermore, patients with CRP ≥ 10 mg/L, HbA1c value ≥ 8.5% as well as patients with hypernatraemia (>145 mmol/L) presented significantly higher odds to develop POD (p = 0.011, p < 0.001, and p = 0.021, respectively). A raised (>14-52 ng/L) or high (>52 ng/L) hsTnT value was also associated with a significantly higher chance for POD compared to the patient group with hsTnT <14 ng/L (p < 0.001 and p = 0.016, respectively).

Conclusions

Preoperative Hgb, CRP, HbA1c, sodium, and hsTnT could be used to complement and refine the preoperative screening for patients at risk for POD. Further studies should track these correlations to investigate the potential of targeted POD protection and enabling hospital staff to initiate POD-preventing measures in time.

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.

Effect of postoperative delirium after cardiovascular surgery on 5-year mortality

INTRODUCTION

Postoperative delirium is a common complication after cardiovascular surgery. A meta-analysis revealed that postoperative delirium was associated with cognitive decline and dementia, which may affect long-term mortality. However, few studies have reported the association between postoperative delirium after cardiovascular surgery and long-term postoperative mortality. Therefore, we investigated the effect of postoperative delirium on 5-year survival rates of patients who underwent cardiovascular surgery.

METHODS

We retrospectively reviewed the records of patients who underwent cardiovascular surgery with cardiopulmonary bypass from January 2016 to December 2019. Postoperative delirium was defined as an Intensive Care Delirium Screening score ≥ 3, which might include subclinical delirium. Cox proportional hazards modeling was performed to assess the association between postoperative delirium and mortality. Postoperative mortality in patients with and without delirium was assessed using the Kaplan-Meier method and compared using the log-rank test.

RESULTS

Postoperative delirium was observed in 562 (31.9%) of 1731 patients. There were more elderly patients, more emergent surgery procedures, longer operative time, and larger transfusion volume in the postoperative delirium group. Cox regression analyses showed that delirium (hazard ratio (HR), 1.501; 95% confidence interval (CI), 1.053-2.140; p = 0.025) and emergent surgery (HR, 3.380; 95% CI, 2.231-5.122; p < 0.001) are significantly associated with 5-year mortality. Among patients who underwent elective surgery, postoperative delirium (HR, 1.987; 95% CI, 1.135-3.481; p = 0.016) is significantly associated with 5-year mortality. Kaplan-Meier survival analysis revealed that patients with postoperative delirium had significantly higher 5-year mortality.

CONCLUSIONS

Patients with postoperative delirium after cardiovascular surgery have significantly higher 5-year mortality.

Cortical reactivity to transcranial magnetic stimulation predicts risk of post-stroke delirium

OBJECTIVE

Post-stroke delirium (PSD) is a frequent and with regard to outcome unfavorable complication in acute stroke. The neurobiological mechanisms predisposing to PSD remain poorly understood, and biomarkers predicting its risk have not been established. We tested the hypothesis that hypoexcitable or disconnected brain networks predispose to PSD by measuring brain reactivity to transcranial magnetic stimulation with electroencephalography (TMS-EEG).

METHODS

We conducted a cross-sectional study in 33 acute stroke patients within 48 hours of stroke onset. Brain reactivity to single-pulse TMS of dorsolateral prefrontal cortex, primary motor cortex and superior parietal lobule of the right hemisphere was quantified by response intensity, effective connectivity, perturbational complexity index (PCI^ST), and natural frequency of the TMS-EEG response. PSD development was clinically tracked every 8 hours before and for 7 days following TMS-EEG.

RESULTS

Fourteen patients developed PSD while 19 patients did not. The PSD group showed lower excitability, effective connectivity, PCI^ST and natural frequency compared to the non-PSD group. The maximum PCI^ST over all three TMS sites demonstrated largest classification accuracy with a ROC-AUC of 0.943. This effect was independent of lesion size, affected hemisphere and stroke severity. Maximum PCI^ST and maximum natural frequency correlated inversely with delirium duration.

CONCLUSIONS

Brain reactivity to TMS-EEG can unravel brain network states of reduced excitability, effective connectivity, perturbational complexity and natural frequency that identify acute stroke patients at high risk for development of delirium.

SIGNIFICANCE

Findings provide novel insight into the pathophysiology of pre-delirium brain states and may promote effective delirium prevention strategies in those patients at high risk.

Postoperative delirium in geriatric patients with hip fractures

Postoperative delirium (POD) is a frequent complication in geriatric patients with hip fractures, which is linked to poorer functional recovery, longer hospital stays, and higher short-and long-term mortality. Patients with increased age, preoperative cognitive impairment, comorbidities, perioperative polypharmacy, and delayed surgery are more prone to develop POD after hip fracture surgery. In this narrative review, we outlined the latest findings on postoperative delirium in geriatric patients with hip fractures, focusing on its pathophysiology, diagnosis, prevention, and treatment. Perioperative risk prediction, avoidance of certain medications, and orthogeriatric comprehensive care are all examples of effective interventions. Choices of anesthesia technique may not be associated with a significant difference in the incidence of postoperative delirium in geriatric patients with hip fractures. There are few pharmaceutical measures available for POD treatment. Dexmedetomidine and multimodal analgesia may be effective for managing postoperative delirium, and adverse complications should be considered when using antipsychotics. In conclusion, perioperative risk intervention based on orthogeriatric comprehensive care is the most effective strategy for preventing postoperative delirium in geriatric patients with hip fractures.

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.

Perivascular spaces visible on magnetic resonance imaging predict subsequent delirium in older patients

Background

It remains unknown whether perivascular spaces (PVS) are associated with delirium in older hospitalized patients. We aimed to determine the association between magnetic resonance imaging (MRI)-visible PVS and the risk of delirium in a cohort of older patients.

Methods

We consecutively recruited older patients (≥70 years) admitted to the Geriatric Department of West China Hospital between March 2016 and July 2017, and their imaging data within one year before admission were reviewed retrospectively. PVS was rated on axial T2-weighted images in the basal ganglia (BG) and centrum semiovale (CS) using the validated semiquantitative 4-point ordinal scale. Delirium was screened within 24 h of admission and three times daily thereafter, using the confusion assessment method. Binary logistic regression analyses were performed to investigate the associations between PVS and delirium.

Results

Among 114 included patients (mean age 84.3 years, 72.8% male), delirium occurred in 20 (17.5%). In patients with MRI examined within 6 months before admission, CS-PVS was found to be associated with delirium (odds ratio [OR] 3.88, 95% confidence interval [CI] 1.07-14.06, unadjusted; and OR 4.24, 95% CI 1.11-16.28, adjusted for age). The associations were enhanced and remained significant even after full adjustment of covariates (OR 7.16, 95% CI 1.16-44.32, adjusted for age, cognitive impairment, smoking, and Charlson Comorbidity Index). Similarly, the relationships between high CS-PVS and delirium were also strengthened after sequentially adjusting all variables of interest, with OR 4.17 (95% CI 1.04-16.73) in unadjusted model and OR 7.95 (95% CI 1.14-55.28) in fully-adjusted model. Adding CS-PVS to the established risk factors improved the risk reclassification for delirium (continuous net reclassification index 62.1%, P = 0.04; and integrated discrimination improvement 12.5%, P = 0.01).

Conclusions

CS-PVS on MRI acquired 6 months earlier predicts subsequent delirium in older patients and may have clinical utility in delirium risk stratification to enable proactive interventions.

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.

Impact of Inflammation on Cognitive Functioning After Electroconvulsive Therapy in Older Patients with Depression with and Without White Matter Hyperintensities

OBJECTIVE

Should we treat older, patients with depression with white matter hyperintensities (WMH) with electroconvulsive therapy (ECT)? WMH, inflammation, depression and cognitive functioning are suggested to be intertwined. Hence, this study investigates whether the association between inflammation and cognition is different in patients with depression with or without WMH.

METHODS

Cognitive functioning was assessed using the Mini-Mental State Examination during and after a course of ECT in 77 older patients with depression. Serum samples (C-reactive protein [CRP], interleukin-6 [IL-6], interleukin-10 [IL-10] and tumour necrosis factor-alpha [TNF-α]) and 3T magnetic resonance imaging were obtained prior to ECT.

RESULTS

An interaction effect was found for IL-10, but not for CRP, IL-6 or TNF-α.

CONCLUSION

In general, the association between inflammatory markers and cognition in patients with depression treated with ECT is not different in patients with WMH compared to patients without WMH.

Cerebral Vascular Dysfunctions Detected in Human Small Vessel Disease and Implications for Preclinical Studies

Cerebral small vessel disease (SVD) is highly prevalent and a common cause of ischemic and hemorrhagic stroke and dementia, yet the pathophysiology is poorly understood. Its clinical expression is highly varied, and prognostic implications are frequently overlooked in clinics; thus, treatment is currently confined to vascular risk factor management. Traditionally, SVD is considered the small vessel equivalent of large artery stroke (occlusion, rupture), but data emerging from human neuroimaging and genetic studies refute this, instead showing microvessel endothelial dysfunction impacting on cell-cell interactions and leading to brain damage. These dysfunctions reflect defects that appear to be inherited and secondary to environmental exposures, including vascular risk factors. Interrogation in preclinical models shows consistent and converging molecular and cellular interactions across the endothelial-glial-neural unit that increasingly explain the human macroscopic observations and identify common patterns of pathology despite different triggers. Importantly, these insights may offer new targets for therapeutic intervention focused on restoring endothelial-glial physiology.

Utility of white matter disease and atrophy on routinely acquired brain imaging for prediction of long-term delirium risk: population-based cohort study

Background

brain imaging done as part of standard care may have clinical utility beyond its immediate indication. Using delirium as an exemplar, we determined the predictive value of baseline brain imaging variables [white matter changes (WMC) and atrophy] for delirium risk on long-term follow-up after transient ischemic attack (TIA)/stroke in a population-based cohort study.

Methods

surviving TIA/stroke participants in the Oxford Vascular Study (OXVASC) were assessed prospectively for delirium during all hospitalisations over 6 months (2013–14). Using logistic regression, independent associations were determined between baseline OXVASC computed tomography or magnetic resonance brain imaging measures of WMC and cerebral atrophy (none/mild versus moderate/severe) and delirium adjusted for age, sex, baseline stroke severity, depression, illness severity and pre-admission cognition.

Results

among 1,565 TIA/stroke survivors with 194 hospital admissions (158 patients, mean/standard deviation age at admission = 79.2/11.5 years), delirium occurred in 59 (37%). WMC and atrophy on baseline imaging were associated with delirium [odds ratio (OR) = 3.41, 1.21–5.85, P = 0.001 and OR = 2.50, 1.23–5.08, P = 0.01 (unadjusted) and OR = 2.67, 1.21–5.85, P = 0.02 and OR = 2.18, 1.00–4.73, P = 0.05 (adjusted age and sex)]. Associations were strengthened when analyses were restricted to patients hospitalised within 5 years of baseline brain imaging [OR = 6.04, 2.39–15.24, P < 0.0001 and OR = 4.64, 1.46–14.82, P = 0.009 (unadjusted)] but only WMC remained significant after adjustment for all covariates including pre-admission cognition (OR = 4.83, 1.29–18.13, P = 0.02 for Mini-Mental State Examination and OR = 5.15, 1.26–21.09, P = 0.02 for Montreal Cognitive Assessment).

Conclusions

WMC and atrophy on brain imaging done up to 5 years earlier predicted delirium and may have clinical utility in risk stratification. Associations with WMC but not atrophy were independent of pre-admission cognitive impairment.

Longitudinal Study of the Association between General Anesthesia and Increased Risk of Developing Dementia

The association between exposure to general anesthesia (GA) and the risk of dementia is still undetermined. To investigate a possible link to the development of dementia in older people who have undergone GA, we analyzed nationwide representative cohort sample data from the Korean National Health Insurance Service. The study cohort comprised patients over 55 years of age who had undergone GA between January 2003 and December 2004 and consisted of 3100 patients who had undergone GA and 12,400 comparison subjects who had not received anesthesia. After the nine-year follow-up period, we found the overall incidence of dementia was higher in the patients who had undergone GA than in the comparison group (10.5 vs. 8.8 per 1000 person-years), with the risk being greater for women (adjusted HR of 1.44; 95% CI, 1.19–1.75) and those with comorbidities (adjusted HR of 1.39; 95% CI, 1.18–1.64). Patients who underwent GA showed higher risks for Alzheimer’s disease and vascular dementia (adjusted HR of 1.52; 95% CI, 1.27–1.82 and 1.64; 95% CI, 1.15–2.33, respectively). This longitudinal study using a sample cohort based on a nationwide population sample demonstrated a significant positive association between GA and dementia, including Alzheimer’s disease and vascular dementia.

Evaluation and Management of Delirium

Delirium, sometimes referred to as encephalopathy, is an acute confusional state that is both common in hospitalized patients and associated with poor outcomes. For patients, families, and caregivers, delirium can be a traumatic experience. While delirium is one of the most common diagnoses encountered by the consulting neurologist, the majority of the time it will have been previously unrecognized as such by the care team. Neurologic syndromes such as dementia or aphasia can either be misdiagnosed as delirium or may coexist with it, necessitating careful neurologic assessment. Once the diagnosis of delirium has been established, a careful evaluation for predisposing and precipitating factors can help uncover modifiable contributors, which should be addressed as part of a multicomponent, primarily nonpharmacologic intervention. Importantly, delirium management, which begins with comprehensive prevention, should emphasize the humanity of the delirious patient and the challenges of caring for this vulnerable population. When considered, delirium represents an important opportunity for the neurologist to substantially enhance patient care.

Why is delirium more frequent in the elderly?

An aging-related reduction in the brain's functional reserve may explain why delirium is more frequent in the elderly than in younger people insofar as the reserve becomes inadequate to cover the metabolic requirements that are critically increased by stressors. The aim of this paper is to review the normal aging-related changes that theoretically compromise complex mental activities, neuronal and synaptic densities, and the neurocomputational flexibility of the functional reserve. A pivotal factor is diminished connectivity, which is substantially due to the loss of synapses and should specifically affect association systems and cholinergic fibres in delirious patients. However, micro-angiopathy with impaired blood flow autoregulation, increased blood/brain barrier permeability, changes in cerebrospinal fluid dynamics, weakened mitochondrial performance, and a pro-inflammatory involution of the immune system may also jointly affect neurons and their synaptic assets, and even cause the progression of delirium to dementia regardless of the presence of co-existing plaques, tangles, or other pathological markers. On the other hand, the developmental growth in functional reserve during childhood and adolescence makes the brain increasingly resistant to delirium, and residual reserve can allow the elderly to recover. These data support the view that functional reserve is the variable that confronts stressors and governs the risk and intensity of and recovery from delirium. Although people of any age are at risk of delirium, the elderly are at greater risk because aging and age-dependent structural changes inevitably affect the brain's functional reserve.

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.

Preoperative MRI brain phenotypes are related to postoperative delirium in older individuals

The underlying structural correlates of predisposition to postoperative delirium remain largely unknown. A combined analysis of preoperative brain magnetic resonance imaging (MRI) markers could improve our understanding of the pathophysiology of delirium. Therefore, we aimed to identify different MRI brain phenotypes in older patients scheduled for major elective surgery, and to assess the relation between these phenotypes and postoperative delirium. Markers of neurodegenerative and neurovascular brain changes were determined from MRI brain scans in older patients (n = 161, mean age 71, standard deviation 5 years), of whom 24 (15%) developed delirium. A hierarchical cluster analysis was performed. We found six distinct groups of patients with different MRI brain phenotypes. Logistic regression analysis showed a higher odds of developing postoperative delirium in individuals with multi-burden pathology (n = 15 (9%), odds ratio (95% confidence interval): 3.8 (1.1-13.0)). In conclusion, these results indicate that different MRI brain phenotypes are related to a different risk of developing delirium after major elective surgery. MRI brain phenotypes could assist in an improved understanding of the structural correlates of predisposition to postoperative delirium.

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.

Preoperative brain MRI features and occurrence of postoperative delirium

OBJECTIVE

Delirium is a frequent complication after surgery with important negative outcomes for affected patients and society. However, it is still largely unknown why some patients have a predisposition for delirium and others not. To increase our understanding of the neural substrate of postoperative delirium, we studied the association between preoperative brain MRI features and the occurrence of delirium after major surgery.

METHODS

A group of 413 patients without dementia (Mean 72 years, SD: 5) was included in a prospective observational two-center study design. The study was conducted at Charité Universitätsmedizin (Berlin, Germany) and the University Medical Center Utrecht (Utrecht, The Netherlands). We measured preoperative brain volumes (total brain, gray matter, white matter), white matter hyperintensity volume and shape, brain infarcts and cerebral perfusion, and used logistic regression analysis adjusted for age, sex, intracranial volume, study center and type of surgery.

RESULTS

Postoperative delirium was present in a total of 70 patients (17%). Preoperative cortical brain infarcts increased the risk of postoperative delirium, although this did not reach statistical significance (OR (95%CI): 1.63 (0.84-3.18). Furthermore, we found a trend for an association of a more complex shape of white matter hyperintensities with occurrence of postoperative delirium (OR (95%CI): 0.97 (0.95-1.00)). Preoperative brain volumes, white matter hyperintensity volume, and cerebral perfusion were not associated with occurrence of postoperative delirium.

CONCLUSION

Our study suggests that patients with preoperative cortical brain infarcts and those with a more complex white matter hyperintensity shape may have a predisposition for developing delirium after major surgery.

Relationship between Deep White Matter Hyperintensities on Magnetic Resonance Imaging and Postoperative Cognitive Function Following Clipping of Unruptured Intracranial Aneurysm

To evaluate the effects on cognitive function of deep white matter hyperintensities (DWMHs) on magnetic resonance imaging (MRI) in patients treated surgically for unruptured intracranial aneurysms (UIAs). The subjects were 106 patients in whom a Wechsler adult intelligence scale-revised (WAIS-R) examination was performed 1 week before and 1 month after clipping surgery for asymptomatic UIAs. DWMH severity was evaluated on preoperative MR images by Fazekas scale, as follows: none (absence), mild (punctate foci), moderate (beginning confluence of foci), or severe (large confluent areas). A decrease of 7 or more points in intelligence quotient (IQ) postoperatively was considered deterioration. Fazekas score was none in 41 (none group), mild in 42 (mild group), moderate in 21, and severe in 2 patients (moderate/severe group). Patient characteristics, surgical factors, IQ change, and abnormal findings on postoperative MRI were compared among the groups. Although there was no statistically significant deterioration in IQ postoperatively in any group, the percentage of deteriorated patients was significantly higher in the moderate/severe group (34.8%) than in the other groups (4.9% in the none group, 7.1% in the mild group; p <0.01, p <0.05, respectively). Brain injury was observed more frequently on postoperative MR images in the moderate/severe group (17.4%) compared with the none group (2.4%; p = 0.052). The presence of moderate/severe DWMHs was an independent prognostic factor for postoperative cognitive dysfunction. In conclusion, the presence of moderate/severe DWMHs was a prognostic factor for postoperative cognitive dysfunction after surgery for UIAs.

The Future Directions of Research in Cardiac Anesthesiology

This article provides an overview of knowledge gaps that need to be addressed in cardiac anesthesia, including mitigating the inflammatory effects of cardiopulmonary bypass, defining myocardial infarction after cardiac surgery, improving perioperative neurologic outcomes, and the optimal management of patients undergoing valve replacement. In addition, emerging approaches to research conduct are discussed, including the use of new analytical techniques like machine learning, pragmatic trials, and adaptive designs.

Clinical and Neuroimaging Correlates of Post-Transplant Delirium

Delirium is common among adults undergoing hematopoietic stem cell transplantation (HCT), although the clinical and neuroimaging correlates of post-HCT delirium have not been adequately delineated. We therefore examined the frequency of delirium and neuroimaging correlates of post-transplant delirium in a retrospective cohort of 115 adults undergoing neuroimaging after allogeneic HCT. Delirium was established using previously validated methods for retrospective identification of chart-assessed postprocedural delirium. Chart reviews were independently conducted by a multidisciplinary team with expertise in HCT, psychiatry, and psychology on consecutive allogeneic HCT patients who underwent neuroimaging assessments and transplantation at a single center between January 2009 and December 2016. Neuroimaging markers of white matter damage and brain volume loss were also recorded. In total, 115 patients were included, ranging in age from 20 to 74 years (mean [SD] age, 49 [13]). Fifty-three patients (46%) developed post-HCT delirium. In an adjusted model, delirium incidence was associated with older age (odds ratio [OR], 1.92 [1.28, 2.87] per decade, P = .002), greater severity of white matter hyperintensities (OR, 1.95 [1.06, 3.57], P = .031), and conditioning intensity (OR, 6.37 [2.20, 18.45], P < .001) but was unrelated to cortical atrophy (P = .777). Delirium was associated with fewer hospital-free days (P = .023) but was not associated with overall survival (hazard ratio, 0.95 [0.56, 1.61], P = .844). Greater incidence of delirium following HCT was associated with greater age, microvascular burden, and conditioning intensity. Pre-HCT consideration of microvascular burden and other neuroimaging biomarkers of risk may be warranted.

The Future Directions of Research in Cardiac Anesthesiology

This article provides an overview of knowledge gaps that need to be addressed in cardiac anesthesia, including mitigating the inflammatory effects of cardiopulmonary bypass, defining myocardial infarction after cardiac surgery, improving perioperative neurologic outcomes, and the optimal management of patients undergoing valve replacement. In addition, emerging approaches to research conduct are discussed, including the use of new analytical techniques like machine learning, pragmatic trials, and adaptive designs.

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.

State of the clinical science of perioperative brain health: report from the American Society of Anesthesiologists Brain Health Initiative Summit 2018

Cognitive recovery after anaesthesia and surgery is a concern for older adults, their families, and caregivers. Reports of patients who were 'never the same' prompted a scientific inquiry into the nature of what patients have experienced. In June 2018, the ASA Brain Health Initiative held a summit to discuss the state of the science on perioperative cognition, and to create an implementation plan for patients and providers leveraging the current evidence. This group included representatives from the AARP (formerly the American Association of Retired Persons), American College of Surgeons, American Heart Association, and Alzheimer's Association Perioperative Cognition and Delirium Professional Interest Area. This paper summarises the state of the relevant clinical science, including risk factors, identification and diagnosis, prognosis, disparities, outcomes, and treatment of perioperative neurocognitive disorders. Finally, we discuss gaps in current knowledge with suggestions for future directions and opportunities for clinical and translational projects.

Cerebral microbleeds are not associated with postoperative delirium and postoperative cognitive dysfunction in older individuals

Background

Cerebral microbleeds (CMB) occur in the context of cerebral small vessel disease. Other brain MRI markers of cerebral small vessel disease are associated with the occurrence of postoperative delirium (POD) and postoperative cognitive dysfunction (POCD), but for CMB this is unknown. We aimed to study the association between CMB and the occurrence of POD and POCD in older individuals.

Methods

The current study consists of 65 patients (72±5 years) from the BIOCOG study, which is a prospective, observational study of patients who underwent an elective surgery of at least 60 minutes. Patients in the current study received a preoperative cerebral MRI scan including a 3D susceptibility-weighted imaging sequence to detect CMB. The occurrence of POD was screened for twice a day until postoperative day 7 by using the DSM-5, NuDesc, CAM, and CAM-ICU. The occurrence of POCD was determined by the reliable change index model at 7 days after surgery or discharge, respectively, and 3 months after surgery. Statistical analyses consisted of logistic regression adjusted for age and gender.

Results

A total of 39 CMB were detected in 17 patients (26%) prior to surgery. POD occurred in 14 out of 65 patients (22%). POCD at 7 days after surgery occurred in 11 out of 54 patients (20%) and in 3 out of 40 patients at the 3 month follow-up (8%). Preoperative CMB were not associated with the occurrence of POD (OR (95%-CI): 0.28 (0.05, 1.57); p = 0.147) or POCD at 7 days after surgery (0.76 (0.16, 3.54); p = 0.727) or at 3 months follow-up (0.61 (0.03, 11.64); p = 0.740).

Conclusion

We did not find an association between preoperative CMB and the occurrence of POD or POCD.

Trial registration

clinicaltrials.gov (NCT02265263) on 23 September 2014.

Neural Correlates of Sleep Disturbance in Alzheimer's Disease: Role of the Precuneus in Sleep Disturbance

Background:

Sleep disturbance may affect the development of Alzheimer’s disease (AD), but the neural correlates of sleep disturbance in AD have not been fully clarified.

Objective:

To examine the factors associated with sleep disturbance in AD.

Methods:

A retrospective study was performed in 63 patients with AD. None of the patients had been prescribed antidementia or psychoactive drugs, and all underwent brain magnetic resonance imaging (MRI) before medication. Sleep disturbance was defined as a score of at least 1 point on the sleep disturbance subscale of the Neuropsychiatric Inventory (NPI). Whole brain image analysis was performed using SPM8 and VBM8. A two-sample t-test was used to compare patients with AD with (n = 19) and without (n = 44) sleep disturbance, with age and gender included as covariates. The statistical thresholds were set to an uncorrected p-value of 0.001 at the voxel level and a corrected p-value of 0.05 at the cluster level. In addition, pineal gland volume (PGV) measured using MRI, and white matter hyperintensity (WMH) assessed with the modified Fazekas scale were compared between patients with AD with and without sleep disturbance using independent group t-tests.

Results:

In whole brain analysis, the precuneus volume in patients with AD with sleep disturbance was significantly smaller than those without sleep disturbance. There were no significant differences in PGV and WMH between the two groups.

Conclusion:

Sleep disturbance in AD was associated with reduction of precuneus volume. This suggests that the precuneus might be an important region in sleep disturbance in AD.

Depression Predicts Delirium After Coronary Artery Bypass Graft Surgery Independent of Cognitive Impairment and Cerebrovascular Disease: An Analysis of the Neuropsychiatric Outcomes After Heart Surgery Study

OBJECTIVE

Although depression is a known risk factor for delirium after coronary artery bypass graft (CABG) surgery, it is unclear whether this risk is independent of delirium risk attributable to cognitive impairment or cerebrovascular disease. This study examines depression, mild cognitive impairment (MCI), and cerebrovascular disease as post-CABG delirium risk factors.

METHODS

This prospective observational cohort study was performed in a tertiary-care academic hospital. Subjects were without dementia and undergoing CABG surgery. Preoperative cognitive assessment included Clinical Dementia Rating and neuropsychological battery; depression was assessed using Depression Interview and Structured Hamilton. Baseline intracranial stenosis was evaluated by transcranial Doppler of bilateral middle cerebral arteries (MCAs). Study psychiatrists assessed delirium on postoperative days 2-5 using the Confusion Assessment Method.

RESULTS

Our analytic sample comprised 131 subjects (average age: 65.8 ± 9.2years, 27% women). MCI prevalence was 24%, preoperative depression 10%, lifetime depression 35%, and MCA stenosis (≥50%) 28%. Sixteen percent developed delirium. Multivariate analysis revealed that age, MCI (odds ratio [OR]: 5.1; 95% confidence interval [CI]: 1.3-20.1), and preoperative depression (OR: 9.9; 95% CI: 1.3-77.9)-but not lifetime depression-predicted delirium. MCA stenosis and severity predicted delirium in univariate but not multivariate analysis. Right MCA stenosis severity predicted delirium severity, but left-sided stenosis severity did not.

CONCLUSION

We established that the risk of delirium attributable to depression extends beyond the potential moderating influence of cognitive impairment and cerebrovascular disease alone. Even mild depression and cognitive impairment before CABG deserve recognition for their effect on post-CABG cognitive health.

Best Practices for Postoperative Brain Health: Recommendations From the Fifth International Perioperative Neurotoxicity Working Group

As part of the American Society of Anesthesiology Brain Health Initiative goal of improving perioperative brain health for older patients, over 30 experts met at the fifth International Perioperative Neurotoxicity Workshop in San Francisco, CA, in May 2016, to discuss best practices for optimizing perioperative brain health in older adults (ie, >65 years of age). The objective of this workshop was to discuss and develop consensus solutions to improve patient management and outcomes and to discuss what older adults should be told (and by whom) about postoperative brain health risks. Thus, the workshop was provider and patient oriented as well as solution focused rather than etiology focused. For those areas in which we determined that there were limited evidence-based recommendations, we identified knowledge gaps and the types of scientific knowledge and investigations needed to direct future best practice. Because concerns about perioperative neurocognitive injury in pediatric patients are already being addressed by the SmartTots initiative, our workshop discussion (and thus this article) focuses specifically on perioperative cognition in older adults. The 2 main perioperative cognitive disorders that have been studied to date are postoperative delirium and cognitive dysfunction. Postoperative delirium is a syndrome of fluctuating changes in attention and level of consciousness that occurs in 20%-40% of patients >60 years of age after major surgery and inpatient hospitalization. Many older surgical patients also develop postoperative cognitive deficits that typically last for weeks to months, thus referred to as postoperative cognitive dysfunction. Because of the heterogeneity of different tools and thresholds used to assess and define these disorders at varying points in time after anesthesia and surgery, a recent article has proposed a new recommended nomenclature for these perioperative neurocognitive disorders. Our discussion about this topic was organized around 4 key issues: preprocedure consent, preoperative cognitive assessment, intraoperative management, and postoperative follow-up. These 4 issues also form the structure of this document. Multiple viewpoints were presented by participants and discussed at this in-person meeting, and the overall group consensus from these discussions was then drafted by a smaller writing group (the 6 primary authors of this article) into this manuscript. Of course, further studies have appeared since the workshop, which the writing group has incorporated where appropriate. All participants from this in-person meeting then had the opportunity to review, edit, and approve this final manuscript; 1 participant did not approve the final manuscript and asked for his/her name to be removed.

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.

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.

Cerebral blood flow MRI in the nondemented elderly is not predictive of post-operative delirium but is correlated with cognitive performance

Three-dimensional Arterial Spin Labeling (ASL) MRI was performed before surgery in a cohort of 146 prospectively enrolled subjects ≥ 70 years old scheduled to undergo elective surgery. We investigated the prospective association between ASL-derived measures of cerebral blood flow (CBF) before surgery with postoperative delirium incidence and severity using whole-brain and globally normalized voxel-wise analysis. We also investigated the cross-sectional association of CBF with patients' baseline performance on specific neuropsychological tests, and with a composite general cognitive performance measure (GCP). Out of 146 subjects, 32 (22%) developed delirium. We found no significant association between global and voxel-wise CBF with delirium incidence or severity. We found the most significant positive associations between CBF of the posterior cingulate and precuneus and the Hopkins Verbal Learning Test - Revised total score, Visual Search and Attention Test (VSAT) score and the GCP composite. VSAT score was also strongly associated with right parietal lobe CBF. ASL can be employed in a large, well-characterized older cohort to examine associations between CBF and age-related cognitive performance. Although ASL CBF measures in regions previously associated with preclinical Alzheimer's Disease were correlated with cognition, they were not found to be indicators of baseline pathology that may increase risk for delirium.

A Decrease in the Volume of Gray Matter as a Risk Factor for Postoperative Delirium Revealed by an Atlas-based Method

OBJECTIVE

Delirium is a common syndrome in older patients after surgery. Although an atrophic change in the whole brain may be a potential risk factor for postoperative delirium, the anatomically specific change related to the vulnerability still remains a significant issue.

DESIGN

Prospective study.

SETTING

University hospital.

PARTICIPANTS

116 consecutive patients who underwent elective cardiac operations.

MEASUREMENTS

Before the surgery, magnetic resonance imaging (MRI) was evaluated. The MRI data were processed to calculate the absolute volumes of the predefined region of interest using Statistical Parametrical Mapping 8 with an atlas-based method. The evaluated volume was expressed as the fraction (%) of the total intracranial volume. Postoperative delirium was diagnosed according to the DSM-IV criteria for delirium.

RESULTS

Delirium developed in 19 of 116 patients (16.4%) with an age range from 58 to 84 years. Based on a comparison with the age-controlled non-delirium patients (over 57 years; n = 65), a statistically significant reduction in the gray matter volume of the delirium patients was observed in the defined gyri of the temporal and limbic lobes. Moreover, a moderate value (>0.8) of area under the curve to predict postoperative delirium was revealed by receiver operating characteristic curve analysis of the gyri of temporal lobe.

CONCLUSIONS

The decreased volume of gray matter could be associated with the vulnerability to delirium after surgery. The atlas-based method would be a potential tool to pre-screen the brain structure of individual patients for the prediction of postoperative delirium.

Neural substrates of vulnerability to postsurgical delirium as revealed by presurgical diffusion MRI

Despite the significant impact of postoperative delirium on surgical outcomes and the long-term prognosis of older patients, its neural basis has not yet been clarified. In this study we investigated the impact of premorbid brain microstructural integrity, as measured by diffusion tensor imaging before surgery, on postoperative delirium incidence and severity, as well as the relationship among presurgical cognitive performance, diffusion tensor imaging abnormalities and postoperative delirium. Presurgical diffusion tensor imaging scans of 136 older (≥70 years), dementia-free subjects from the prospective Successful Aging after Elective Surgery study were analysed blind to the clinical data and delirium status. Primary outcomes were postoperative delirium incidence and severity during the hospital stay, as assessed by the Confusion Assessment Method. We measured cognition before surgery using general cognitive performance, a composite score based on a battery of neuropsychological tests. We investigated the association between presurgical diffusion tensor imaging parameters of brain microstructural integrity (i.e. fractional anisotropy, axial, mean and radial diffusivity) with postoperative delirium incidence and severity. Analyses were adjusted for the following potential confounders: age, gender, vascular comorbidity status, and general cognitive performance. Postoperative delirium occurred in 29 of 136 subjects (21%) during hospitalization. Presurgical diffusion tensor imaging abnormalities of the cerebellum, cingulum, corpus callosum, internal capsule, thalamus, basal forebrain, occipital, parietal and temporal lobes, including the hippocampus, were associated with delirium incidence and severity, after controlling for age, gender and vascular comorbidities. After further controlling for general cognitive performance, diffusion tensor imaging abnormalities of the cerebellum, hippocampus, thalamus and basal forebrain still remained associated with delirium incidence and severity. This study raises the intriguing possibility that structural dysconnectivity involving interhemispheric and fronto-thalamo-cerebellar networks, as well as microstructural changes of structures involved in limbic and memory functions predispose to delirium under the stress of surgery. While the diffusion tensor imaging abnormalities observed in the corpus callosum, cingulum, and temporal lobe likely constitute the neural substrate for the association between premorbid cognition, as measured by general cognitive performance, and postoperative delirium, the microstructural changes observed in the cerebellum, hippocampus, thalamus and basal forebrain seem to constitute a separate phenomenon that predisposes to postsurgical delirium independent of presurgical cognitive status.

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

PURPOSE

Delirium is common after cardiac surgery and is associated with adverse consequences, including cognitive decline. Identification of vulnerable older adults might allow for early implementation of delirium-prevention strategies. Brain MRI findings provide insight into structural brain changes that may identify vulnerable patients. The purpose of this study was to examine the association between brain MRI characteristics potentially associated with delirium vulnerability and the development of postoperative delirium in a nested cohort of patients undergoing cardiac surgery.

METHODS

We identified 79 cardiac surgery patients who had brain MRI imaging after cardiac surgery, as part of an ongoing randomized trial evaluating the efficacy of blood pressure management based on cerebral autoregulation monitoring versus standard management for improving neurological outcomes. Cerebral lateral ventricular size, cortical sulcal width, and white matter hyperintensities (WMH) on brain MRI scans were graded on a validated 0 to 9 scale, and categorized into tertiles. New ischemic lesions were characterized as present or absent. Delirium was assessed using a validated chart-review. Neuropsychological testing performed before surgery was used to establish preoperative cognitive baseline. Multivariable logistic regression was used to assess the independent association between MRI characteristics and postoperative delirium.

FINDINGS

The average age of patients was 70.1 ± 7.8 years old, and 72% were male. Twenty-eight of 79 (35.4%) patients developed postoperative delirium. Patients with delirium had higher unadjusted ventricular size (median 4 vs. 3, P = 0.003), and there was a trend towards higher sulcal sizes and WMH grades. Increasing tertiles of ventricular size (Odds Ratio [OR] 3.59; 95% Confidence Interval [CI] 1.59-8.12; P = 0.002) and sulcal size (OR 2.15; 95%CI 1.13-4.12; P = 0.02) were associated with postoperative delirium, with a trend for tertiles of WMH grade (OR 1.91; 95%CI 0.99-3.68; P = 0.05). In multivariable models adjusted for logistic EuroSCORE, baseline cognitive status, bypass time, and any postoperative complication, each tertile of ventricular size was associated with increased odds of postoperative delirium (OR 3.23 per tertile increase in ventricular size; 95%CI 1.21-8.60; P = 0.02). There were no differences in odds of delirium by tertiles of sulcal grade, tertiles of white matter grade, or presence of new ischemic lesions, in adjusted models.

IMPLICATIONS

Increased brain ventricular size was independently associated with delirium after cardiac surgery. These results suggest that cerebral atrophy may contribute to increased vulnerability for postoperative delirium. Baseline brain MRIs may be useful in identifying cardiac surgery patients at high risk for postoperative delirium, who might benefit from targeted perioperative approaches to prevent delirium. ClinicalTrials.gov identifier: NCT00981474.

Biomarkers of postoperative delirium and cognitive dysfunction

Elderly surgical patients frequently experience postoperative delirium (POD) and the subsequent development of postoperative cognitive dysfunction (POCD). Clinical features include deterioration in cognition, disturbance in attention and reduced awareness of the environment and result in higher morbidity, mortality and greater utilization of social financial assistance. The aging Western societies can expect an increase in the incidence of POD and POCD. The underlying pathophysiological mechanisms have been studied on the molecular level albeit with unsatisfying small research efforts given their societal burden. Here, we review the known physiological and immunological changes and genetic risk factors, identify candidates for further studies and integrate the information into a draft network for exploration on a systems level. The pathogenesis of these postoperative cognitive impairments is multifactorial; application of integrated systems biology has the potential to reconstruct the underlying network of molecular mechanisms and help in the identification of prognostic and diagnostic biomarkers.

Brain atrophy and white-matter hyperintensities are not significantly associated with incidence and severity of postoperative delirium in older persons without dementia

Postoperative delirium is a common complication in older people and is associated with increased mortality, morbidity, institutionalization, and caregiver burden. Although delirium is an acute confusional state characterized by global impairments in attention and cognition, it has been implicated in permanent cognitive impairment and dementia. The pathogenesis of delirium and the mechanisms leading to these disabling consequences remain unclear. The present study is the first to address the potential predisposing role of brain morphologic changes toward postoperative delirium in a large prospective cohort of patients undergoing elective surgery using state-of-the-art magnetic resonance imaging (MRI) techniques conducted before admission. We investigated the association of MRI-derived quantitative measures of white-matter damage, global brain, and hippocampal volume with the incidence and severity of delirium. Presurgical white-matter hyperintensities (WMHs), whole brain, and hippocampal volume were measured in 146 consecutively enrolled subjects, ≥70 years old, without dementia who were undergoing elective surgery. These 3 presurgical MRI indices were tested as predictors of incidence and severity of subsequent delirium. Out of 146 subjects, 32 (22%) developed delirium. We found no statistically significant differences in WMH, whole brain, or hippocampal volume between subjects with and without delirium. Both unadjusted and adjusted (age, gender, vascular comorbidity, and general cognitive performance) regression analyses demonstrated no statistically significant association between any of the MRI measures with respect to delirium incidence or severity. In persons without dementia, preexisting cerebral WMHs, general and hippocampal atrophy may not predispose to postoperative delirium or worsen its severity.

Neurological complications of cardiac surgery

As increasing numbers of elderly people undergo cardiac surgery, neurologists are frequently called upon to assess patients with neurological complications from the procedure. Some complications mandate acute intervention, whereas others need longer term observation and management. A large amount of published literature exists about these complications and guidance on best practice is constantly changing. Similarly, despite technological advances in surgical intervention and modifications in surgical technique to make cardiac procedures safer, these advances often create new avenues for neurological injury. Accordingly, rapid and precise neurological assessment and therapeutic intervention rests on a solid understanding of the evidence base and procedural variables.

Delirium in the cardiac surgical ICU

PURPOSE OF REVIEW

Evidence is emerging that delirium is associated with both short-term and long-term morbidity and mortality. This review highlights the epidemiology, outcomes, prevention and treatment strategies associated with delirium after cardiac surgery.

RECENT FINDINGS

The incidence of delirium after cardiac surgery is estimated to be 26-52%, with a significant percentage being hypoactive delirium. It is clear that without an appropriate structured test for delirium, the incidence of delirium will be underrecognized clinically. Delirium after cardiac surgery is associated with poor outcomes, including increased long-term mortality, increased risk of stroke, poor functional status, increased hospital readmissions and substantial cognitive dysfunction for 1 year following surgery. The effectiveness of prophylactic antipsychotics to reduce the risk of delirium is controversial, with data from recent small studies in noncardiac surgery potentially showing a benefit. Although antipsychotic medications are often used to treat delirium, the evidence that antipsychotics in cardiac surgery patients reduce duration of delirium or improve long-term outcomes following delirium is poor.

SUMMARY

Clinicians in the ICU must recognize the impact of delirium in predicting long-term outcomes for patients. Further research is needed in determining interventions that will be effective in preventing and treating delirium in cardiac surgical setting.

Fast-track surgery decreases the incidence of postoperative delirium and other complications in elderly patients with colorectal carcinoma

Objective

This study aims to investigate the role of fast-track surgery in preventing the development of postoperative delirium and other complications in elderly patients with colorectal carcinoma.

Methods

A total of 240 elderly patients with colorectal carcinoma (aged ≥70 years) undergoing open colorectal surgery was randomly assigned into two groups, in which the patients were managed perioperatively either with traditional or fast-track approaches. The length of hospital stay (LOS) and time to pass flatus were compared. The incidence of postoperative delirium and other complications were evaluated. Serum interleukin-6 (IL-6) levels were determined before and after surgery.

Results

The LOS was significantly shorter in the fast-track surgery (FTS) group than that in the traditional group. The recovery of bowel movement (as indicated by the time to pass flatus) was faster in the FTS group. The postoperative complications including pulmonary infection, urinary infection and heart failure were significantly less frequent in the FTS group. Notably, the incidence of postoperative delirium was significantly lower in patients with the fast track therapy (4/117, 3.4 %) than with the traditional therapy (15/116, 12.9 %; p = 0.008). The serum IL-6 levels on postoperative days 1, 2, and 3 in patients with the fast-track therapy were significantly lower than those with the traditional therapy (p < 0.001).

Conclusions

Compared to traditional perioperative management, fast-track surgery decreases the LOS, facilitates the recovery of bowel movement, and reduces occurrence of postoperative delirium and other complications in elderly patients with colorectal carcinoma. The lower incidence of delirium is at least partly attributable to the reduced systemic inflammatory response mediated by IL-6.

Neuropathogenesis of delirium: review of current etiologic theories and common pathways

Delirium is a neurobehavioral syndrome caused by dysregulation of neuronal activity secondary to systemic disturbances. Over time, a number of theories have been proposed in an attempt to explain the processes leading to the development of delirium. Each proposed theory has focused on a specific mechanism or pathologic process (e.g., dopamine excess or acetylcholine deficiency theories), observational and experiential evidence (e.g., sleep deprivation, aging), or empirical data (e.g., specific pharmacologic agents' association with postoperative delirium, intraoperative hypoxia). This article represents a review of published literature and summarizes the top seven proposed theories and their interrelation. This review includes the "neuroinflammatory," "neuronal aging," "oxidative stress," "neurotransmitter deficiency," "neuroendocrine," "diurnal dysregulation," and "network disconnectivity" hypotheses. Most of these theories are complementary, rather than competing, with many areas of intersection and reciprocal influence. The literature suggests that many factors or mechanisms included in these theories lead to a final common outcome associated with an alteration in neurotransmitter synthesis, function, and/or availability that mediates the complex behavioral and cognitive changes observed in delirium. In general, the most commonly described neurotransmitter changes associated with delirium include deficiencies in acetylcholine and/or melatonin availability; excess in dopamine, norepinephrine, and/or glutamate release; and variable alterations (e.g., either a decreased or increased activity, depending on delirium presentation and cause) in serotonin, histamine, and/or γ-aminobutyric acid. In the end, it is unlikely that any one of these theories is fully capable of explaining the etiology or phenomenologic manifestations of delirium but rather that two or more of these, if not all, act together to lead to the biochemical derangement and, ultimately, to the complex cognitive and behavioral changes characteristic of delirium.