Association between cerebrospinal fluid biomarkers of neuronal injury or amyloidosis and cognitive decline after major surgery

Amyloid beta-induced mitochondrial dysfunction and endothelial permeability in cerebral microvascular endothelial cells: The protective role of dexmedetomidine

Postoperative cognitive dysfunction (POCD) is a common complication in patients who undergo anesthesia in different types of surgeries. Emerging evidence implicates elevated beta-amyloid (Aβ) in the pathogenesis of POCD. Meanwhile, Dexmedetomidine (DEX) has recently shown promise in reducing POCD incidence. This study aimed to elucidate the role of Aβ in inducing endothelial permeability in cerebral microvascular endothelial cells and the underlying mechanisms and testing the effects of DEX. We demonstrated that Aβ1-42, the prevalent Aβ form related to POCD, is cytotoxic to HBMECs, increasing transendothelial permeability and inducing mitochondrial dysfunction, as evidenced by elevated mitochondrial reactive oxygen species (ROS) and decreased ATP production and mitochondrial membrane potential. Furthermore, Aβ1-42 was shown to inhibit Sirt3, exacerbating mitochondrial dysfunction. Conversely, DEX was found to prevent Aβ1-42-induced mitochondrial dysfunction and permeability increases and preserved tight junction proteins in HBMECs.These findings suggest that DEX, as a Sirt3 activator, may offer a pharmacological strategy to mitigate Aβ1-42-related cerebral microvascular endothelial cell dysfunction and preserve cognitive function post-surgery.

Changes in circulating extracellular vesicle cargo are associated with cognitive decline after major surgery: an observational case-control study

BACKGROUND

Postoperative neurocognitive decline is a frequent complication triggered by unclear signalling mechanisms. This observational case-control study investigated the effects of hip or knee replacement surgery on the composition of circulating extracellular vesicles (EVs), potential periphery-to-brain messengers, and their association with neurocognitive outcomes.

METHODS

We mapped the microRNAome and proteome of plasma-derived EVs from 12 patients (six with good and six with poor neurocognitive outcomes at 3 months after surgery) at preoperative and postoperative timepoints (4, 8, 24, and 48 h). Complement C3-EV association was confirmed by flow cytometry in plasma- and cerebrospinal fluid (CSF)-derived EVs, with total plasma and CSF C3 and C3a concentrations determined using enzyme-linked immunosorbent assay.

RESULTS

Differential expression analysis found eight dysregulated EV microRNAs (miRNAs) exclusively in the poor neurocognitive outcomes group. Pathway analysis suggested potential downregulation of proliferative pathways and activation of extracellular matrix and inflammatory response pathways in EV target tissues. Proteome analysis revealed a time-dependent increase in immune-related EV proteins, including complement system proteins, notably EV surface-associated C3. Such upward kinetics was detected earlier in the poor neurocognitive outcomes group. Interestingly, CSF-derived EVs from the same group showed a drastic drop of C3 at 48 h with unchanged concentrations in the good neurocognitive outcomes group. Functionally, the complement system was activated in both patient groups in plasma, but only in the poor neurocognitive outcomes group in CSF.

CONCLUSIONS

Our findings highlight the impact of surgery on plasma- and CSF-derived EVs, particularly in patients with poor neurocognitive outcomes, indicating a potential role for EVs. The small sample size necessitates verification with a larger patient cohort.

Serum Neurofilament Light and Postoperative Delirium in Cardiac Surgery: A Preplanned Secondary Analysis of a Prospective Observational Study

BACKGROUND

Impaired cognition is a major predisposing factor for postoperative delirium, but it is not systematically assessed. Anesthesia and surgery may cause postoperative delirium by affecting brain integrity. Neurofilament light in serum reflects axonal injury. Studies evaluating the perioperative course of neurofilament light in cardiac surgery have shown conflicting results. The authors hypothesized that postoperative serum neurofilament light values would be higher in delirious patients, and that baseline concentrations would be correlated with patients' cognitive status and would identify patients at risk of postoperative delirium.

METHODS

This preplanned secondary analysis included 220 patients undergoing elective cardiac surgery with cardiopulmonary bypass. A preoperative cognitive z score was calculated after a neuropsychological evaluation. Quantification of serum neurofilament light was performed by the Simoa (Quanterix, USA) technique before anesthesia, 2 h after surgery, on postoperative days 1, 2, and 5. Postoperative delirium was assessed using the Confusion Assessment Method for Intensive Care Unit, the Confusion Assessment Method, and a chart review.

RESULTS

A total of 65 of 220 (29.5%) patients developed postoperative delirium. Delirious patients were older (median [25th percentile, 75th percentile], 74 [64, 79] vs. 67 [59, 74] yr; P < 0.001) and had lower cognitive z scores (-0.52 ± 1.14 vs. 0.21 ± 0.84; P < 0.001). Postoperative neurofilament light concentrations increased in all patients up to day 5, but did not predict delirium when preoperative concentrations were considered. Baseline neurofilament light values were significantly higher in patients who experienced delirium. They were influenced by age, cognitive z score, renal function, and history of diabetes mellitus. Baselines values were significantly correlated with cognitive z scores (r, 0.49; P < 0.001) and were independently associated with delirium whenever the patient's cognitive status was not considered (hazard ratio, 3.34 [95% CI, 1.07 to 10.4]).

CONCLUSIONS

Cardiac surgery is associated with axonal injury, because neurofilament light concentrations increased postoperatively in all patients. However, only baseline neurofilament light values predicted postoperative delirium. Baseline concentrations were correlated with poorer cognitive scores, and they independently predicted postoperative delirium whenever patient's cognitive status was undetermined.

EDITOR’S PERSPECTIVE

Associations between Alzheimer's disease biomarkers and postoperative delirium or cognitive dysfunction: A meta-analysis and trial sequential analysis of prospective clinical trials

BACKGROUND

The relationship between Alzheimer's disease biomarkers and postoperative complications, such as postoperative delirium (POD) and postoperative cognitive dysfunction (POCD), remains a subject of ongoing debate.

OBJECTIVE

This meta-analysis aimed to determine whether there is an association between perioperative Alzheimer's disease biomarkers and postoperative complications.

DESIGN

We conducted a meta-analysis of observational clinical studies that explored the correlation between Alzheimer's disease biomarkers and POD or POCD in patients who have undergone surgery, following PRISMA guidelines. The protocol was previously published (INPLASY: INPLASY202350001).

DATA SOURCES

A comprehensive search was conducted across PubMed, Embase, Web of Science, and Cochrane databases until March 2023.

ELIGIBILITY CRITERIA

Surgical patients aged at least 18 years, studies focusing on POD or POCD, research involving Alzheimer's disease biomarkers, including Aβ or tau in blood or cerebrospinal fluid (CSF), and availability of the full text.

RESULTS

Our meta-analysis included 15 studies: six focusing on POD and nine on POCD. The findings revealed a negative correlation between preoperative CSF β-amyloid 42 (Aβ42) levels and the onset of POD [mean difference -86.1, 95% confidence interval (CI), -114.15 to -58.05, I2 : 47%]; this association was strongly supported by trial sequential analysis (TSA). A similar negative correlation was discerned between preoperative CSF Aβ42 levels and the incidence of POCD (-165.01, 95% CI, -261.48 to -68.53, I2 : 95%). The TSA also provided robust evidence for this finding; however, the evidence remains insufficient to confirm a relationship between other Alzheimer's disease biomarkers [β-amyloid 40 (Aβ40), total tau (T-tau), phosphorylated tau (P-tau), and Aβ42/T-tau ratio] and POD or POCD.

CONCLUSION

The study results indicate a negative correlation between preoperative CSF Aβ42 levels and the occurrence of both POD and POCD. Future investigations are warranted to identify the predictive cutoff value of preoperative CSF Aβ42 for POD and POCD.

Association of perioperative plasma concentration of neurofilament light with delirium after cardiac surgery: a nested observational study

BACKGROUND

Neurofilament light is a blood-based biomarker of neuroaxonal injury that can provide insight into perioperative brain vulnerability and injury. Prior studies have suggested that increased baseline and postoperative concentrations of neurofilament light are associated with delirium after noncardiac surgery, but results are inconsistent. Results have not been reported in cardiac surgery patients, who are among those at highest risk for delirium. We hypothesised that perioperative blood concentrations of neurofilament light (both baseline and change from baseline to postoperative day 1) are associated with delirium after cardiac surgery.

METHODS

This study was nested in a trial of arterial blood pressure targeting during cardiopulmonary bypass using cerebral autoregulation metrics. Blood concentrations of neurofilament light were measured at baseline and on postoperative day 1. The primary outcome was postoperative delirium. Regression models were used to examine the associations between neurofilament light concentration and delirium and delirium severity, adjusting for age, sex, race, logistic European System for Cardiac Operative Risk Evaluation, bypass duration, and cognition.

RESULTS

Delirium occurred in 44.6% of 175 patients. Baseline neurofilament light concentration was higher in delirious than in non-delirious patients (median 20.7 pg ml-1 [IQR 16.1-33.2] vs median 15.5 pg ml-1 [IQR 12.1-24.2], P<0.001). In adjusted models, greater baseline neurofilament light concentration was associated with delirium (odds ratio, 1.027; 95% confidence interval, 1.003-1.053; P=0.029) and delirium severity. From baseline to postoperative day 1, neurofilament light concentration increased by 42%, but there was no association with delirium.

CONCLUSIONS

Baseline neurofilament light concentration, but not change from baseline to postoperative day 1, was associated with delirium after cardiac surgery.

Hypotension during transsphenoidal pituitary surgery associated with increase in plasma levels of brain injury markers

BACKGROUND

Patients undergoing pituitary surgery may experience short- and long-term postoperative morbidity. Intraoperative factors such as hypotension might be a contributing factor. Our aim was to investigate the association between intraoperative hypotension and postoperative plasma levels of tau, neurofilament light (NfL), and glial fibrillary acidic protein (GFAP) as markers of perioperative brain injury.

METHODS

Between June 2016 and October 2017, 35 patients from the Gothenburg Pituitary Tumor Study were included. For tau, NfL, and GFAP, concentrations were measured in plasma samples collected before and immediately following surgery, and on postoperative days 1 and 5. The difference between the highest postoperative value and the value before surgery was used for analysis (∆taupeak , ∆NfLpeak , ∆GFAPpeak ). Intraoperative hypotension was defined as the area under the curve of an absolute threshold below 70 mmHg (AUC70) and a relative threshold below 20% (AUC20%) of the baseline mean arterial blood pressure.

RESULTS

Plasma tau and GFAP were highest immediately following surgery and on day 1, while NfL was highest on day 5. There was a positive correlation between AUC20% and both ∆taupeak (r2  = .20, p < .001) and ∆NfLpeak (r2  = .26, p < .001). No association was found between AUC20% and GFAP or between AUC70 and ∆taupeak , ∆NfLpeak or ∆GFAPpeak .

CONCLUSION

Intraoperative relative, but not absolute, hypotension was associated with increased postoperative plasma tau and NfL concentrations. Patients undergoing pituitary surgery may be vulnerable to relative hypotension, but this needs to be validated in future prospective studies.

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

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

Age-dependent differences and similarities in the plasma proteomic signature of postoperative delirium

Delirium is an acute confusional state and a common postoperative morbidity. Prevalent in older adults, delirium occurs at other ages but it is unclear whether the pathophysiology and biomarkers for the condition are independent of age. We quantified expression of 273 plasma proteins involved in inflammation and cardiovascular or neurologic conditions in 34 middle-aged and 42 older patients before and one day after elective spine surgery. Delirium was identified by the 3D-CAM and comprehensive chart review. Protein expression was measure by Proximity Extension Assay and results were analyzed by logistic regression, gene set enrichment, and protein-protein interactions. Twenty-two patients developed delirium postoperatively (14 older; 8 middle-aged) and 89 proteins in pre- or 1-day postoperative plasma were associated with delirium. A few proteins (IL-8, LTBR, TNF-R2 postoperatively; IL-8, IL-6, LIF, ASGR1 by pre- to postoperative change) and 12 networks were common to delirium in both age groups. However, there were marked differences in the delirium proteome by age; older patients had many more delirium-associated proteins and pathways than middle-aged subjects even though both had the same clinical syndrome. Therefore, there are age-dependent similarities and differences in the plasma proteomic signature of postoperative delirium, which may signify age differences in pathogenesis of the syndrome.

Anesthesia outcomes in lysosomal disorders: CLN3 and GM1 gangliosidosis

Natural history studies of pediatric rare neurometabolic diseases are important to understand disease pathophysiology and to inform clinical trial outcome measures. Some data collections require sedation given participants' age and neurocognitive impairment. To evaluate the safety of sedation for research procedures, we reviewed medical records between April 2017 and October 2019 from a natural history study for CLN3 (NCT03307304) and one for GM1 gangliosidosis (NCT00029965). Twenty-two CLN3 individuals underwent 28 anesthetic events (age median 11.0, IQR 8.4-15.3 years). Fifteen GM1 individuals had 19 anesthetic events (9.8, 7.1-14.7). All participants had the American Society of Anesthesiology classification of II (8/47) or III (39/47). Mean sedation durations were 186 (SD = 54; CLN3) and 291 (SD = 33; GM1) min. Individuals with GM1 (6/19, 31%) were more frequently prospectively intubated for sedation (CLN3 3/28, 11%). Minor adverse events associated with sedation occurred in 8/28 (28%, CLN3) and 6/19 (32%, GM1) individuals, frequencies within previously reported ranges. No major adverse clinical outcomes occurred in 47 anesthetic events in pediatric participants with either CLN3 or GM1 gangliosidosis undergoing research procedures. Sedation of pediatric individuals with rare neurometabolic diseases for research procedures is safe and allows for the collection of data integral to furthering their understanding and treatment.

The multifaceted role of neurofilament light chain protein in non-primary neurological diseases

The advancing validation and exploitation of CSF and blood neurofilament light chain protein as a biomarker of neuroaxonal damage has deeply changed the current diagnostic and prognostic approach to neurological diseases. Further, recent studies have provided evidence of potential new applications of this biomarker also in non-primary neurological diseases. In the present review we summarize the state of the art, future perspectives, but also limitations, of neurofilament light chain protein as a CSF and blood biomarker in several medical fields, including intensive care medicine, surgery, internal medicine and psychiatry. In particular, neurofilament light chain protein is associated with the degree of neurological impairment and outcome in patients admitted to intensive care units or in the perioperative phase and it seems to be highly interconnected with cardiovascular risk factors. Beyond that, interesting diagnostic and prognostic insights have been provided by the investigation of neurofilament light chain protein in psychiatric disorders as well as in the current coronavirus disease-19 pandemic and in normal ageing. Altogether, current data outline a multifaceted applicability of CSF and blood neurofilament light chain protein ranging from the critical clinical setting to the development of precision medicine models suggesting a strict interplay between the nervous system pathophysiology and the health-illness continuum.

Relationship between postoperative biomarkers of neuronal injury and postoperative cognitive dysfunction: A meta-analysis

Early biomarkers are needed to identify patients at risk of developing postoperative cognitive dysfunction (POCD). Our objective was to determine neuronal injury-related biomarkers with predictive values for this condition. Six biomarkers (S100β, neuron-specific enolase [NSE], amyloid beta [Aβ], tau, neurofilament light chain, and glial fibrillary acidic protein) were evaluated. According to the first postoperative sampling time, observational studies showed that S100β was significantly higher in patients with POCD than in those without POCD (standardized mean difference [SMD]: 6.92, 95% confidence interval [CI]: 4.44-9.41). The randomized controlled trial (RCT) showed that S100β (SMD: 37.31, 95% CI: 30.97-43.64) and NSE (SMD: 3.50, 95% CI: 2.71-4.28) in the POCD group were significantly higher than in the non-POCD group. The pooled data of observational studies by postoperative sampling time showed significantly higher levels of the following biomarkers in the POCD groups than in the control groups: S100β levels at 1 hour (SMD: 1.35, 95% CI: 0.07-2.64), 2 days (SMD: 27.97, 95% CI: 25.01-30.94), and 9 days (SMD: 6.41, 95% CI: 5.64-7.19); NSE levels at 1 hour (SMD: 0.92, 95% CI: 0.25-1.60), 6 hours (SMD: 0.79, 95% CI: 0.12-1.45), and 24 hours (SMD: 0.84, 95% CI: 0.38-1.29); and Aβ levels at 24 hours (SMD: 2.30, 95% CI: 1.54-3.06), 2 days (SMD: 2.30, 95% CI: 1.83-2.78), and 9 days (SMD: 2.76, 95% CI: 2.25-3.26). The pooled data of the RCT showed that the following biomarkers were significantly higher in POCD patients than in non-POCD patients: S100β levels at 2 days (SMD: 37.31, 95% CI: 30.97-43.64) and 9 days (SMD: 126.37, 95% CI: 104.97-147.76) and NSE levels at 2 days (SMD: 3.50, 95% CI: 2.71-4.28) and 9 days (SMD: 8.53, 95% CI: 7.00-10.06). High postoperative levels of S100β, NSE, and Aβ may predict POCD. The relationship between these biomarkers and POCD may be affected by sampling time.

Perioperative Neurofilament Light Plasma Concentrations and Cognition before and after Cardiac Surgery: A Prospective Nested Cohort Study

BACKGROUND

Neurofilament light is a marker of neuronal injury and can be measured in blood. Postoperative increases in neurofilament light have been associated with delirium after noncardiac surgery. However, few studies have examined the association of neurofilament light changes with postdischarge cognition in cardiac surgery patients, who are at highest risk for neuronal injury and cognitive decline. The authors hypothesized that increased neurofilament light (both baseline and change) would be associated with worse neuropsychological status up to 1 yr after cardiac surgery.

METHODS

This observational study was nested in a trial of cardiac surgery patients, in which blood pressure during bypass was targeted using cerebral autoregulation monitoring. Plasma concentrations of neurofilament light were measured at baseline and postoperative day 1. Neuropsychological testing was performed at baseline, 1 month after surgery, and 1 yr after surgery. Primary outcomes were baseline and change from baseline in a composite z-score of all cognitive tests.

RESULTS

Among 167 patients, cognitive outcomes were available in 80% (134 of 167) and 61% (102 of 167) at 1 month and 1 yr after surgery, respectively. The median baseline concentration of neurofilament light was 18.2 pg/ml (interquartile range, 13.4 to 28.1), and on postoperative day 1 was 28.5 pg/ml (interquartile range, 19.3 to 45.0). Higher baseline log neurofilament light was associated with worse baseline cognitive z-score (adjusted slope, -0.60; 95% CI, -0.90 to -0.30; P < 0.001), no change in z-score from baseline to 1 month (0.11; 95% CI, -0.19 to 0.41; P = 0.475), and improvement in z-score from baseline to 1 yr (0.56; 95% CI, 0.31 to 0.81; P < 0.001). Whereas some patients had an improvement in cognition at 1 yr and others a decline, an increase in neurofilament light from baseline to postoperative day 1 was associated with a greater decline in cognition at 1 yr.

CONCLUSIONS

Higher baseline neurofilament light concentration was associated with worse baseline cognition but improvement in cognition at 1 yr. A postoperative increase in neurofilament light was associated with a greater cognitive decline at 1 yr.

EDITOR’S PERSPECTIVE

Mitigation of perioperative neurocognitive disorders: A holistic approach

William Morton introduced the world to ether anesthesia for use during surgery in the Bullfinch Building of the Massachusetts General Hospital on October 16, 1846. For nearly two centuries, the prevailing wisdom had been that the effects of general anesthetics were rapidly and fully reversible, with no apparent long-term adverse sequelae. Despite occasional concerns of a possible association between surgery and anesthesia with dementia since 1887 (Savage, 1887), our initial belief was robustly punctured following the publication in 1998 of the International Study of Post-Operative Cognitive Dysfunction [ISPOCD 1] study by Moller et al. (1998) in The Lancet, in which they demonstrated in a prospective fashion that there were in fact persistent adverse effects on neurocognitive function up to 3 months following surgery and that these effects were common. Since the publication of that landmark study, significant strides have been made in redefining the terminology describing cognitive dysfunction, identifying those patients most at risk, and establishing the underlying etiology of the condition, particularly with respect to the relative contributions of anesthesia and surgery. In 2018, the International Nomenclature Consensus Working Group proposed new nomenclature to standardize identification of and classify perioperative cognitive changes under the umbrella of perioperative neurocognitive disorders (PND) (Evered et al., 2018a). Since then, the new nomenclature has tried to describe post-surgical cognitive derangements within a unifying framework and has brought to light the need to standardize methodology in clinical studies and motivate such studies with hypotheses of PND pathogenesis. In this narrative review, we highlight the relevant literature regarding recent key developments in PND identification and management throughout the perioperative period. We provide an overview of the new nomenclature and its implications for interpreting risk factors identified by clinical association studies. We then describe current hypotheses for PND development, using data from clinical association studies and neurophysiologic data where appropriate. Finally, we offer broad clinical guidelines for mitigating PND in the perioperative period, highlighting the role of Brain Enhanced Recovery After Surgery (Brain-ERAS) protocols.

Risk assessment of perioperative neurocognitive disorders, where are we now?

PURPOSE OF REVIEW

Perioperative neurocognitive disorders (PNDs) are among the most frequent complications after surgery and are associated with considerable morbidity and mortality. We analysed the recent literature regarding risk assessment of PND.

RECENT FINDINGS

Certain genetic variants of the cholinergic receptor muscarinic 2 and 4, as well as a marked degree of frailty but not the kind of anaesthesia (general or spinal) are associated with the risk to develop postoperative delirium (POD). Models predict POD with a discriminative power, for example, area under the receiver operating characteristics curve between 0.52 and 0.94.

SUMMARY

Advanced age as well as preexisting cognitive, functional and sensory deficits remain to be the main risk factors for the development of PND. Therefore, aged patients should be routinely examined for both preexisting and new developing deficits, as recommended in international guidelines. Appropriate tests should have a high discrimination rate, be feasible to be administered by staff that do not require excessive training, and only take a short time to be practical for a busy outpatient clinic. Models to predict PND, should be validated appropriately (and externally if possible) and should not contain a too large number of predictors to prevent overfitting of models.

The Karolinska NeuroCOVID study protocol: Neurocognitive impairment, biomarkers and advanced imaging in critical care survivors

Background

This is the study plan of the Karolinska NeuroCOVID study, a study of neurocognitive impairment after severe COVID‐19, relating post‐intensive care unit (ICU) cognitive and neurological deficits to biofluid markers and MRI. The COVID‐19 pandemic has posed enormous health challenges to individuals and health‐care systems worldwide. An emerging feature of severe COVID‐19 is that of temporary and extended neurocognitive impairment, exhibiting a myriad of symptoms and signs. The causes of this symptomatology have not yet been fully elucidated.

Methods

In this study, we aim to investigate patients treated for severe COVID‐19 in the ICU, as to describe and relate serum‐, plasma‐ and cerebrospinal fluid‐borne molecular and cellular biomarkers of immune activity, coagulopathy, cerebral damage, neuronal inflammation, and degeneration, to the temporal development of structural and functional changes within the brain as evident by serial MRI and extensive cognitive assessments at 3–12 months after ICU discharge.

Results

To date, we have performed 51 3‐month follow‐up MRIs in the ICU survivors. Of these, two patients (~4%) have had incidental findings on brain MRI findings requiring activation of the Incidental Findings Management Plan. Furthermore, the neuropsychological and neurological examinations have so far revealed varying and mixed patterns. Several patients expressed cognitive and/or mental concerns and fatigue, complaints closely related to brain fog.

Conclusion

The study goal is to gain a better understanding of the pathological mechanisms and neurological consequences of this new disease, with a special emphasis on neurodegenerative and neuroinflammatory processes, in order to identify targets of intervention and rehabilitation.

Postoperative changes in cognition and cerebrospinal fluid neurodegenerative disease biomarkers

OBJECTIVE

Numerous investigators have theorized that postoperative changes in Alzheimer's disease neuropathology may underlie postoperative neurocognitive disorders. Thus, we determined the relationship between postoperative changes in cognition and cerebrospinal (CSF) tau, p-tau-181p, or Aβ levels after non-cardiac, non-neurologic surgery in older adults.

METHODS

Participants underwent cognitive testing before and 6 weeks after surgery, and lumbar punctures before, 24 h after, and 6 weeks after surgery. Cognitive scores were combined via factor analysis into an overall cognitive index. In total, 110 patients returned for 6-week postoperative testing and were included in the analysis.

RESULTS

There was no significant change from before to 24 h or 6 weeks following surgery in CSF tau (median [median absolute deviation] change before to 24 h: 0.00 [4.36] pg/mL, p = 0.853; change before to 6 weeks: -1.21 [3.98] pg/mL, p = 0.827). There were also no significant changes in CSF p-tau-181p or Aβ over this period. There was no change in cognitive index (mean [95% CI] 0.040 [-0.018, 0.098], p = 0.175) from before to 6 weeks after surgery, although there were postoperative declines in verbal memory (-0.346 [-0.523, -0.170], p = 0.003) and improvements in executive function (0.394, [0.310, 0.479], p < 0.001). There were no significant correlations between preoperative to 6-week postoperative changes in cognition and CSF tau, p-tau-181p, or Aβ42 changes over this interval (p > 0.05 for each).

INTERPRETATION

Neurocognitive changes after non-cardiac, non-neurologic surgery in the majority of cognitively healthy, community-dwelling older adults are unlikely to be related to postoperative changes in AD neuropathology (as assessed by CSF Aβ, tau or p-tau-181p levels or the p-tau-181p/Aβ or tau/Aβ ratios).

TRIAL REGISTRATION

clinicaltrials.gov (NCT01993836).

Long-term evidence of neonatal anaesthesia neurotoxicity linked to behavioural phenotypes in monkeys: where do we go from here?

Whether anaesthesia exposure early in life leads to brain damage with long-lasting structural and behavioural consequences in primates has not been conclusively determined. A study in the British Journal of Anaesthesia by Neudecker and colleagues found that 2 yr after early anaesthesia exposure, monkeys exhibited signs of chronic astrogliosis which correlate with behavioural deficits. Given the increasing frequency of exposure to anaesthetics in infancy in humans, clinical trials are greatly needed to understand how sedative/anaesthetic agents may be impacting brain and behaviour development.

Serum markers of brain injury can predict good neurological outcome after out-of-hospital cardiac arrest

PURPOSE

The majority of unconscious patients after cardiac arrest (CA) do not fulfill guideline criteria for a likely poor outcome, their prognosis is considered "indeterminate". We compared brain injury markers in blood for prediction of good outcome and for identifying false positive predictions of poor outcome as recommended by guidelines.

METHODS

Retrospective analysis of prospectively collected serum samples at 24, 48 and 72 h post arrest within the Target Temperature Management after out-of-hospital cardiac arrest (TTM)-trial. Clinically available markers neuron-specific enolase (NSE) and S100B, and novel markers neurofilament light chain (NFL), total tau, ubiquitin carboxy-terminal hydrolase L1 (UCH-L1) and glial fibrillary acidic protein (GFAP) were analysed. Normal levels with a priori cutoffs specified by reference laboratories or defined from literature were used to predict good outcome (no to moderate disability, Cerebral Performance Category scale 1-2) at 6 months.

RESULTS

Seven hundred and seventeen patients were included. Normal NFL, tau and GFAP had the highest sensitivities (97.2-98% of poor outcome patients had abnormal serum levels) and NPV (normal levels predicted good outcome in 87-95% of patients). Normal S100B and NSE predicted good outcome with NPV 76-82.2%. Normal NSE correctly identified 67/190 (35.3%) patients with good outcome among those classified as "indeterminate outcome" by guidelines. Five patients with single pathological prognostic findings despite normal biomarkers had good outcome.

CONCLUSION

Low levels of brain injury markers in blood are associated with good neurological outcome after CA. Incorporating biomarkers into neuroprognostication may help prevent premature withdrawal of life-sustaining therapy.