The Fallacy of Persistent Postoperative Cognitive Decline

General anesthesia is not associated with dementia in older adults with osteoarthritis for hip/knee replacements, a national population-based nested case-control study

BACKGROUND

Dementia is a prevalent neurological condition, yet the relationship between dementia and general anesthesia remains uncertain. The study aimed to explore the association between general anesthesia and dementia using a nationwide population-based database.

METHODS

The study extracted data from Taiwan's national health insurance, which encompassed the records of one million insured residents. A total of 59,817 patients aged 65 years and above, diagnosed with osteoarthritis between 2002 and 2010, were included. Among these patients, 3277 individuals with an initial diagnosis of dementia between 2004 and 2013 were matched with non-dementia patients based on age, gender, and the date of osteoarthritis diagnosis. Following a 1:2 random matching, the case group included 2171 patients with dementia, while the control group consisted of 4342 patients without dementia. The data was analyzed using conditional and unconditional logistic regressions.

RESULTS

No significant differences in the odds of dementia were found between individuals exposed to general and regional anesthesia during hip/knee replacement surgeries (OR = 1.11; 95%CI: 0.73-1.70), after adjusting for age, sex, and co-morbidities. Similarly, there were no significant differences in the odds of dementia based on different durations of anesthesia exposure (General: <2 h: OR = 0.91, 95%CI = 0.43-1.92; 2-4 h: OR = 1.21, 95%CI = 0.82-1.79; >4 h: OR = 0.39, 95%CI = 0.15-1.01; compared to no exposure. Regional: <2 h: OR = 1.18, 95%CI = 0.85-1.62; 2-4 h: OR = 0.9, 95%CI = 0.64-1.27; >4 h: OR = 0.55, 95%CI = 0.15-1.96; compared to no exposure). Likewise, no significant differences were observed in the odds of dementia based on the number of replacement surgeries (twice: OR = 0.74, 95%CI = 0.44-1.23, compared to once).

CONCLUSION

Neither general anesthesia nor regional anesthesia in hip/knee surgery was associated with dementia. Different numbers and durations of anesthesia exposure showed no significant differences in the odds for dementia.

Critical Assessment of the Neurological Complications during High-Risk Anesthesia Procedures

Damage to the peripheral and central nervous systems is frequently irreversible. Surgically induced neurological damage and anesthesia may result in catastrophic situations for patients and their families. The incidence of significant neurological complications during the perioperative period is examined in this article. In contrast to other organs like the kidney, heart, liver, lungs, and skeletal system, native neurological function cannot be replaced with artificial parts or devices soon. Ignoring brain function during the perioperative period has been a systemic problem in anesthesiology, even though the central and peripheral nervous systems are crucial. This bold claim is intended to draw attention to the fact that, unlike the circulatory and respiratory systems, which have been routinely monitored for decades, the brain and other neural structures do not have a standard monitoring during surgery and anesthesia. Given that the brain and spinal cord are the principal therapeutic targets of analgesics and anesthetics, this deficiency in clinical care is even more alarming. Organs that are notoriously hard to repair or replace after damage have, up until now, received comparatively little attention. In this article, a succinct overview of five neurological complications associated with surgery and anesthesia is presented. After critically reviewing the literature on the subject, the article is focused to common (delirium), controversial (postoperative cognitive decline), and potentially catastrophic (stroke, spinal cord ischemia, or postoperative visual loss) adverse events in the neurological surgery setting. The findings will increase awareness of major neurological complications to the involved surgical and anesthesia team and enhance preventive and treatment strategies during the perioperative period.

Novel Mechanisms of Perioperative Neurocognitive Disorders: Ferroptosis and Pyroptosis

Perioperative neurocognitive disorders (PNDs) are some of the most common postoperative complications among the elderly and susceptible individuals, which significantly worsens the clinical outcome of patients. However, the prevention and treatment strategies of PNDs are difficult to determine and implement since the pathogenesis of PNDs is not well understood. The development of living organisms is associated with active and organized cell death, which is essential for maintaining the homeostasis of life. Ferroptosis is a programmed cell death (different from apoptosis and necrosis) mainly caused by an imbalance in the generation and degradation of intracellular lipid peroxides due to iron overload. Pyroptosis is an inflammatory cell death characterized by the creation of membrane holes mediated by the gasdermin (GSDM) family, followed by cell lysis and the release of pro-inflammatory cytokines. Ferroptosis and pyroptosis are involved in the pathogenesis of various central nervous system (CNS) diseases. Furthermore, ferroptosis and pyroptosis are closely associated with the occurrence and development of PNDs. This review summarizes the main regulatory mechanisms of ferroptosis and pyroptosis and the latest related to PNDs. Based on the available evidence, potential intervention strategies that can alleviate PNDs by inhibiting ferroptosis and pyroptosis have also been provided.

Postoperative Delirium and Cognitive Dysfunction after General and Regional Anesthesia: A Systematic Review and Meta-Analysis

Background: Perioperative disorders of neurocognitive function are a set of heterogeneous conditions, which include transient post-operative delirium (POD) and more prolonged post-operative cognitive dysfunction (POCD). Since the number of annually performed surgical procedures is growing, we should identify which type of anesthesia is safer for preserving neurocognitive function. The purpose of this study was to compare the effect of general anesthesia (GA) and regional anesthesia (RA) in patients undergoing surgical procedures under general anesthesia and regional anesthesia. Material and methods: We searched for randomized controlled studies, which studied post-operative cognitive outcomes after general and regional anesthesia in the adult patient population. Results: Thirteen articles with 3633 patients: the RA group consisted of 1823 patients, and the GA group of 1810 patients, who were selected for meta-analysis. The overall effect of the model shows no difference between these two groups in terms of risk for post-operative delirium. The result is insensitive to the exclusion of any study. There was no difference between RA and GA in terms of post-operative cognitive dysfunction. Conclusions: There was no statistically significant difference between GA and RA in the incidence of POD. There was no statistically significant difference in the incidence of POCD per-protocol analysis, psychomotor/attention tests (preoperative/baseline, post-operative), memory tests (postoperatively, follow up), mini-mental state examination score 24 h postoperatively, post-operative reaction time three months postoperatively, controlled oral word association test, and digit copying test. There were no differences in the incidence of POCD in general and regional anesthesia at one week postoperatively, three months postoperatively, or total events (one week or three months). The incidence of post-operative mortality also did not differ between two groups.

Comparison of Postoperative Cognitive Decline Using the Mini-Mental State Examination and Montreal Cognitive Assessment After Minor Elective Surgery in Elderly

Introduction and aim

Postoperative cognitive dysfunction (POCD) is an important complication associated with increased morbidity, mortality, and reduced quality of life. Generally, studies have focused on major surgery so there is little evidence of the incidence of cognitive dysfunction in minor surgery. We aimed to compare the Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) in terms of detecting cognitive decline in elderly patients after elective inguinal herniorrhaphy procedure with general or spinal anesthesia.

Material and methods

This observational study was conducted from June 2014 to March 2015 at Ankara Numune Education and Research Hospital. The type of anesthesia was determined according to the anesthesiologist’s preference who is blind to the study. Patients were grouped according to anesthesia received: general or spinal anesthesia. The MMSE and MoCA were evaluated presurgery and 24 hours after the operation.

Results

The postoperative (24th hour) MMSE scores of patients (26.23±2.77) were significantly lower than the preoperative scores (27.17±1.93) in only the general anesthesia group (p =0.003). The postoperative (24th hour) MoCA scores (22.87±3.88 for general and 23.13±4.08 for spinal anesthesia) were significantly lower than the preoperative scores (24.32±3.19 for general and 24.35±2.84 for spinal anesthesia) in both the general and spinal anesthesia groups (p =0.000 and 0.019, respectively). The incidence of postoperative cognitive dysfunction was 32.9% using the MoCA and 15.2% using the MMSE (p=0,018).

Conclusion

Early POCD is an important problem after elective minor surgeries, even with spinal anesthesia, in elderly patients. The MoCA is an alternative tool that can be more sensitive than the MMSE to identify cognitive decline in elderly patients undergoing minor surgeries under both general and spinal anesthesia. 

Distinct and Dissociable EEG Networks Are Associated With Recovery of Cognitive Function Following Anesthesia-Induced Unconsciousness

The temporal trajectories and neural mechanisms of recovery of cognitive function after a major perturbation of consciousness is of both clinical and neuroscientific interest. The purpose of the present study was to investigate network-level changes in functional brain connectivity associated with the recovery and return of six cognitive functions after general anesthesia. High-density electroencephalograms (EEG) were recorded from healthy volunteers undergoing a clinically relevant anesthesia protocol (propofol induction and isoflurane maintenance), and age-matched healthy controls. A battery of cognitive tests (motor praxis, visual object learning test, fractal-2-back, abstract matching, psychomotor vigilance test, digital symbol substitution test) was administered at baseline, upon recovery of consciousness (ROC), and at half-hour intervals up to 3 h following ROC. EEG networks were derived using the strength of functional connectivity measured through the weighted phase lag index (wPLI). A partial least squares (PLS) analysis was conducted to assess changes in these networks: (1) between anesthesia and control groups; (2) during the 3-h recovery from anesthesia; and (3) for each cognitive test during recovery from anesthesia. Networks were maximally perturbed upon ROC but returned to baseline 30-60 min following ROC, despite deficits in cognitive performance that persisted up to 3 h following ROC. Additionally, during recovery from anesthesia, cognitive tests conducted at the same time-point activated distinct and dissociable functional connectivity networks across all frequency bands. The results highlight that the return of cognitive function after anesthetic-induced unconsciousness is task-specific, with unique behavioral and brain network trajectories of recovery.

Risk factors and predictive value of perioperative neurocognitive disorders in elderly patients with gastrointestinal tumors

BACKGROUND

This study aims to investigate the risk factors of perioperative neurocognitive disorders (PNDs) mainly including postoperative cognitive dysfunction (POCD) in elderly patients with gastrointestinal tumors, and evaluate its predictive value.

METHODS

A total of 222 eligible elderly patients (≥65 years) scheduled for elective gastroenterectomy under general anesthesia were enrolled. The cognitive function assessment was carried out 1 day before surgery and 7 days after surgery. Receiver operating characteristic curve analysis was performed to evaluate the predictive value of risk factors for early POCD. The risk factors for POCD were analyzed using univariate and multivariate logistic regression model.

RESULTS

Of all the 222 enrolled patients, 91 (41.0%) developed early POCD and 40 (18.0%) were identified as major POCD within 7 days after the surgery. Visual analogue score (VAS, 1st day, resting) ≥4 (OR = 7.618[3.231-17.962], P < 0.001) and alcohol exposure (OR = 2.398[1.174-4.900], P = 0.016) were independent risk factors for early POCD. VAS score (1st, resting) ≥4 (OR = 13.823[4.779-39.981], P < 0.001), preoperative white blood cell (WBC) levels ≥10 × 10*9/L (OR = 5.548[1.128-26.221], P = 0.035), blood loss ≥500 ml (OR = 3.317[1.094-10.059], P = 0.034), history of hypertension (OR = 3.046[1.267-7.322], P = 0.013), and neutrophil-lymphocyte ratio (NLR) ≥2 (OR = 3.261[1.020-10.419], P = 0.046) were independent risk factors for major POCD. Receiver operating characteristic curve analysis indicated that VAS score (1st day, resting) was a significant predictor for major POCD with a cut-off value of 2.68 and an area under the curve of 0.860 (95% confidence interval: 0.801-0.920, P < 0.001).

CONCLUSIONS

The risk factors for early POCD after gastroenterectomy included high VAS score (1st day, resting) and alcohol exposure. High VAS score, preoperative WBC levels ≥10 × 10*9/L, blood loss ≥500 ml, NLR ≥2, and history of hypertension were independent risk factors for major POCD. Among them, VAS score was one of the important predictors.

Cerebral Hypoxia: Its Role in Age-Related Chronic and Acute Cognitive Dysfunction

Postoperative cognitive dysfunction (POCD) has been reported with widely varying frequency but appears to be strongly associated with aging. Outside of the surgical arena, chronic and acute cerebral hypoxia may exist as a result of respiratory, cardiovascular, or anemic conditions. Hypoxia has been extensively implicated in cognitive impairment. Furthermore, disease states associated with hypoxia both accompany and progress with aging. Perioperative cerebral hypoxia is likely underdiagnosed, and its contribution to POCD is underappreciated. Herein, we discuss the various disease processes and forms in which hypoxia may contribute to POCD. Furthermore, we outline hypoxia-related mechanisms, such as hypoxia-inducible factor activation, cerebral ischemia, cerebrovascular reserve, excitotoxicity, and neuroinflammation, which may contribute to cognitive impairment and how these mechanisms interact with aging. Finally, we discuss opportunities to prevent and manage POCD related to hypoxia.

Recovery of consciousness and cognition after general anesthesia in humans

Understanding how the brain recovers from unconsciousness can inform neurobiological theories of consciousness and guide clinical investigation. To address this question, we conducted a multicenter study of 60 healthy humans, half of whom received general anesthesia for 3 hr and half of whom served as awake controls. We administered a battery of neurocognitive tests and recorded electroencephalography to assess cortical dynamics. We hypothesized that recovery of consciousness and cognition is an extended process, with differential recovery of cognitive functions that would commence with return of responsiveness and end with return of executive function, mediated by prefrontal cortex. We found that, just prior to the recovery of consciousness, frontal-parietal dynamics returned to baseline. Consistent with our hypothesis, cognitive reconstitution after anesthesia evolved over time. Contrary to our hypothesis, executive function returned first. Early engagement of prefrontal cortex in recovery of consciousness and cognition is consistent with global neuronal workspace theory.

Surgical Complications in Older Adults Predict Decline in Self-Perceived Cognitive Function in the Ensuing Year: A Cohort Study

BACKGROUND

Surgical complications are common among older adults and are potential indicators of poorer long-term outcomes. The authors examined the effects of in-hospital complications on changes in older adults' self-perceived cognitive function in the year after surgery.

METHOD

The authors conducted a prospective longitudinal study with 2,155 older adults (age ≥ 65) undergoing surgery, investigating the association between self-reported, in-hospital complications after surgery and Patient-Reported Outcomes Measurement Information System Applied Cognition-Abilities survey (4 items, cognitive function) at 30 days and 1 year after surgery. Surveys were scored on a continuous scale of 0-100, with higher scores representing better self-perceived cognitive functioning. Patient characteristics including demographics, type of complications, surgery type, pain, and activities of daily living were also collected.

RESULTS

Having one in-hospital complication was associated with a decrease of 1.79 points (95% confidence interval (CI): -2.78, -0.80), indicating lower self-perceived cognitive functioning at 1 year after surgery; having two or more in-hospital complications was associated with 2.82 point (95% CI: -4.50, -1.15) decrease at 1 year after surgery. Models specific to complication type indicated that respiratory [-3.04, (95% CI: -5.50, -0.57)], neural [-2.11, (95% CI: -3.97, -0.25)], and general complications [-2.39, (95% CI: -3.51, -1.28)] were associated with statistically significant decreases in cognitive function.

DISCUSSION

Older surgical patients who suffer in-hospital complications show greater decline in self-perceived cognitive function during the ensuing year. Geriatric specialists may be able to intervene in the immediate perioperative period to reduce complications and possibly mitigate cognitive decline among older adults.

Brain Aging and Anesthesia

Herein, the authors review the neuroanatomical and the neurophysiological aspects of the normal aging evolution based on the recent literature and briefly describe the difference between physiological and pathological brain aging, with consideration of the currently recommended anesthesia management of older patients. The population of elderly patients is growing drastically with advances in medicine that have prolonged the life span. One of the direct consequence has been a significant increase in the request for anesthesia care for older patients despite the type of surgery (cardiac vs noncardiac and mainly orthopedic). Because the brain of this category of patients undergoes a specific triple influence (immune, metabolic, and inflammatory), some particular physiological, anatomical, and structural modifications must be taken into account because they expose these patients more specifically to postoperative cognitive disturbances. To prevent type of adverse outcome, a better knowledge and understanding of these neurosciences must be promoted. The strategies developed to prevent such adverse outcomes include the determination and detection of significant at-risk patients and improvement in the titration of anesthesia to reduce exposure of anesthesia to these patients through an adapted anesthesia-induced unconsciousness that avoids, as much as possible, the risk of toxic overdose with an overly deep brain depression. To accomplish this, the unprocessed electroencephalogram (EEG) and its spectrogram may represent a significant improvement in monitoring, first by allowing for the rapid recognition of repetitive or persistent EEG suppression by the on-line reading of the raw EEG trace and second by allowing for the accurate determination of the adequate anesthetic-induced state, obtained in general in this category of patients by substantially lowered doses of anesthetic agents. This represents a new methodology for anesthesia titration that is adjusted on a more case-by-case basis and is related to the physiology of individual patients. A better understanding of aging-induced brain transformations remains the key regarding the improvement of the anesthetic management of the always growing population of elderly patients. The promotion of the unprocessed EEG may represent the best method of preventing the risk of anesthetic toxicity, including postoperative cognitive dysfunctions.

Association Between Exposure to General Versus Regional Anesthesia and Risk of Dementia in Older Adults

BACKGROUND/OBJECTIVES

Cognitive changes are commonly observed in older adults following surgical procedures. There are concerns that exposure to general anesthesia (GA) may contribute to an increased risk of Alzheimer's disease. Our study examined the associations between exposure to GA compared with regional anesthesia (RA) administered for elective surgical procedures and the development of dementia.

DESIGN

Population-based propensity matched retrospective cohort study.

SETTING

Linked administrative databases were accessed from ICES (formerly called the Institute for Clinical Evaluative Services) in Ontario, Canada.

PARTICIPANTS

We included all community-dwelling individuals aged 66 and older who underwent one of five elective surgical procedures in Ontario, Canada, between April 1, 2007, and March 31, 2011. Individuals with evidence of dementia preceding cohort entry were excluded. Individuals who received GA were matched within surgical procedures to those who received RA on age, sex, cohort entry year, and a propensity score to control for potential confounders.

MEASUREMENTS

The baseline characteristics of the study sample were compared before and after matching. Individuals were followed for up to 5 years following cohort entry for the occurrence of dementia using a validated algorithm. Cox proportional hazards analysis was used to determine the hazard ratio (HR) and 95% confidence interval (CI) for the association between anesthetic type and dementia. Subgroup and sensitivity analyses were undertaken.

RESULTS

A total of 7,499 matched pairs were included in the final analysis. Overall, no difference was observed in the risk of being diagnosed with dementia for individuals who received GA when compared with RA (HR = 1.0; 95% CI = .8-1.2). There was also no association between anesthesia and dementia in most subgroup and sensitivity analyses.

CONCLUSION

Elective surgery using GA was not associated with an overall elevated risk of dementia when compared with RA. Future studies are required to determine whether surgery is a risk factor for dementia irrespective of anesthetic technique.

Association of Surgical Hospitalization with Brain Amyloid Deposition: The Atherosclerosis Risk in Communities-Positron Emission Tomography (ARIC-PET) Study

BACKGROUND

As more older adults undergo surgery, it is critical to understand the long-term effects of surgery on brain health, particularly in relation to the development of Alzheimer's disease. This study examined the association of surgical hospitalization with subsequent brain β-amyloid deposition in nondemented older adults.

METHODS

The Atherosclerosis Risk in Communities-Positron Emission Tomography (ARIC-PET) study is a prospective cohort study of 346 participants without dementia who underwent florbetapir PET imaging. Active surveillance of local hospitals and annual participant contact were used to gather hospitalization and surgical information (International Classification of Disease, Ninth Revision, Clinical Modification codes) over the preceding 24-yr period. Brain amyloid measured using florbetapir PET imaging was the primary outcome. Elevated amyloid was defined as a standardized uptake value ratio of more than 1.2.

RESULTS

Of the 313 participants included in this analysis (age at PET: 76.0 [SD 5.4]; 56% female), 72% had a prior hospitalization, and 50% had a prior surgical hospitalization. Elevated amyloid occurred in 87 of 156 (56%) participants with previous surgical hospitalization, compared with 45 of 87 (52%) participants who had no previous hospitalization. Participants with previous surgical hospitalizations did not show an increased odds of elevated brain amyloid (odds ratio, 1.32; 95% CI, 0.72 to 2.40; P = 0.370) after adjusting for confounders (primary analysis). Results were similar using the reference group of all participants without previous surgery (hospitalized and nonhospitalized; odds ratio, 1.58; 95% CI, 0.96 to 2.58; P = 0.070). In a prespecified secondary analysis, participants with previous surgical hospitalization did demonstrate increased odds of elevated amyloid when compared with participants hospitalized without surgery (odds ratio, 2.10; 95% CI, 1.09 to 4.05; P = 0.026). However, these results were attenuated and nonsignificant when alternative thresholds for amyloid-positive status were used.

CONCLUSIONS

The results do not support an association between surgical hospitalization and elevated brain amyloid.

Perioperative Neurocognitive Disorder: State of the Preclinical Science

The purpose of this article is to provide a succinct summary of the different experimental approaches that have been used in preclinical postoperative cognitive dysfunction research, and an overview of the knowledge that has accrued. This is not intended to be a comprehensive review, but rather is intended to highlight how the many different approaches have contributed to our understanding of postoperative cognitive dysfunction, and to identify knowledge gaps to be filled by further research. The authors have organized this report by the level of experimental and systems complexity, starting with molecular and cellular approaches, then moving to intact invertebrates and vertebrate animal models. In addition, the authors' goal is to improve the quality and consistency of postoperative cognitive dysfunction and perioperative neurocognitive disorder research by promoting optimal study design, enhanced transparency, and "best practices" in experimental design and reporting to increase the likelihood of corroborating results. Thus, the authors conclude with general guidelines for designing, conducting and reporting perioperative neurocognitive disorder rodent research.

Lifetime surgical exposure, episodic memory, and forniceal microstructure in older adults

Introduction: Aging is associated with heterogeneous cognitive trajectories. There is considerable interest in identifying risk factors for pathological aging, with recent studies demonstrating a link between surgical procedures and proximal cognitive decline; however, the role of lifetime exposure to surgical procedures and cognitive function has been relatively unexplored. This pilot study aimed to evaluate the association between total lifetime surgical procedures and memory function in older adults. Methods: A cohort of 62 older adults underwent a neuropsychological evaluation and health history assessment. Self-reported lifetime surgical history was categorized as "cardiac" or "non-cardiac." General linear models were fit with demographics as nuisance covariates, and the total number of non-cardiac surgeries as our predictor of interest. Total scores on measures of episodic memory, language, working memory, fluency, and visuospatial function were separate outcome variables. In a secondary analysis, vascular risk factors were included as covariates. Diffusion tensor imaging was obtained for exploratory analyses of selected regions of interest. Results: The mean age of participants was 70, and 0-13 lifetime non-cardiac surgical procedures were reported. Higher numbers of lifetime non-cardiac surgical procedures were associated with worse verbal learning and memory (p = .04). The negative association between lifetime non-cardiac procedures and cognition was specific to memory. Exploratory analyses showed that higher number of lifetime non-cardiac procedures was related to lower FA in the fornix body (p = .02). Conclusions: These results of this pilot study suggest that greater lifetime exposure to surgery may be associated with worse verbal learning and memory in healthy older adults. These findings add to a growing body of literature suggesting that cumulative medical events may be risk factors for negative cognitive outcomes.

Road to Perioperative Medicine: A Perspective From China

With the development of anesthesiology, patient safety has been remarkably improved, but the postoperative mortality rate at 30 days is still as high as 0.56%-4%, and the morbidity is even higher. Three years ago, the Chinese Society of Anesthesiology proposed that the direction of the anesthesiology development should be changed to perioperative medicine in China. Anesthesiologists should pay more attention to the long-term outcome. In this article, we introduced what we have done, what the challenges are, and what we should do in the future with regard to the practice of perioperative medicine in China.

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.

Association between major surgical admissions and the cognitive trajectory: 19 year follow-up of Whitehall II cohort study

OBJECTIVE

To quantify the association between major surgery and the age related cognitive trajectory.

DESIGN

Prospective longitudinal cohort study.

SETTING

United Kingdom.

PARTICIPANTS

7532 adults with as many as five cognitive assessments between 1997 and 2016 in the Whitehall II study, with linkage to hospital episode statistics. Exposures of interest included any major hospital admission, defined as requiring more than one overnight stay during follow-up.

MAIN OUTCOMES MEASURES

The primary outcome was the global cognitive score established from a battery of cognitive tests encompassing reasoning, memory, and phonemic and semantic fluency. Bayesian linear mixed effects models were used to calculate the change in the age related cognitive trajectory after hospital admission. The odds of substantial cognitive decline induced by surgery defined as more than 1.96 standard deviations from a predicted trajectory (based on the first three cognitive waves of data) was also calculated.

RESULTS

After accounting for the age related cognitive trajectory, major surgery was associated with a small additional cognitive decline, equivalent on average to less than five months of aging (95% credible interval 0.01 to 0.73 years). In comparison, admissions for medical conditions and stroke were associated with 1.4 (1.0 to 1.8) and 13 (9.6 to 16) years of aging, respectively. Substantial cognitive decline occurred in 2.5% of participants with no admissions, 5.5% of surgical admissions, and 12.7% of medical admissions. Compared with participants with no major hospital admissions, those with surgical or medical events were more likely to have substantial decline from their predicted trajectory (surgical admissions odds ratio 2.3, 95% credible interval 1.4 to 3.9; medical admissions 6.2, 3.4 to 11.0).

CONCLUSIONS

Major surgery is associated with a small, long term change in the average cognitive trajectory that is less profound than for major medical admissions. The odds of substantial cognitive decline after surgery was about doubled, though lower than for medical admissions. During informed consent, this information should be weighed against the potential health benefits of surgery.

Brain metastases and treatment: multiplying cognitive toxicities

INTRODUCTION

Thirty per cent of cancer patients develop brain metastases, with multiple combination or sequential treatment modalities available, to treat systemic or central nervous system (CNS) disease. Most patients experience toxicities as a result of these treatments, of which cognitive impairment is one of the adverse events most commonly reported, causing major impairment of the patient's quality of life. Areas covered: This article reviews the role of cancer treatments in cognitive decline of patients with brain metastases: surgery, radiotherapy, chemotherapy, targeted therapies, immunotherapies and hormone therapy. Pathological and molecular mechanisms, as well as future directions for limiting cognitive toxicities are also presented. Other causes of cognitive impairment in this population are discussed in order to refine the benefit-risk balance of each treatment modality. Expert opinion: Cumulative cognitive toxicity should be taken into account, and tailored to the patient's cognitive risk in the light of the expected survival benefit. Standardization of cognitive assessment in this context is needed in order to better appreciate each treatment's responsibility in cognitive impairment, keeping in mind disease itself impacts cognition in this context.

Cognitive Outcomes After Heart Valve Surgery: A Systematic Review and Meta-Analysis

OBJECTIVES

To summarize evidence on cognitive outcomes after heart valve surgery; secondary aim, to examine whether aortic and mitral valve surgery are associated with different cognitive outcomes.

DESIGN

Preferred Reporting Items for Systematic Reviews and Meta-Analyses systematic review and meta-analysis.

SETTING

Cardiac surgery.

PARTICIPANTS

Individuals undergoing heart valve surgery.

MEASUREMENTS

We searched MEDLINE, EMBASE, and PsycINFO for peer-reviewed reports of individuals undergoing heart valve surgery who underwent pre- and postoperative cognitive assessment. Our initial search returned 1,475 articles, of which 12 were included. Postoperative cognitive results were divided into those from 1 week to 1 month (early outcomes, n_pooled  = 450) and from 2 to 6 months (intermediate outcomes; n_pooled  = 722). No studies with longer-term outcomes were identified.

RESULTS

Subjects had moderate early cognitive decline from baseline (Becker mean gain effect size (ES)=-0.39 ± 0.27) that improved slightly by 2 to 6 months (ES=-0.25 ± 0.38). Individuals undergoing aortic valve surgery-who were older on average than those undergoing mitral valve surgery (68 vs 57)-had greater early cognitive decline than those undergoing mitral valve surgery (ES=-0.68 vs -0.12), but both cohorts had similar decline 2 to 6 months postoperatively (ES=-0.27 vs -0.20).

CONCLUSIONS

Heart valve surgery is associated with cognitive decline over the 6 months after surgery, but outcomes beyond 6 months are unclear. These findings highlight the cognitive vulnerability of this population, especially older adults with aortic stenosis. © 2018 American Geriatrics Society and Wiley Periodicals, Inc. J Am Geriatr Soc 66:2327-2334, 2018.

Tools to screen and measure cognitive impairment after surgery and anesthesia

Cognition is essential to all aspects of our everyday life. Although we take our cognitive function for granted, the perioperative period is prone to several aggressions that might impair it. Postoperative cognitive dysfunction, has been the aim of many studies recently, and was shown to be very common with an incidence that can reach 40%, yielding not only impairment in cognition, but also longer hospital stays, higher costs and greater mortality. While several studies have revealed some of the mechanisms contributing to postoperative cognitive dysfunction, the search for the perfect instrument to screen and measure cognitive (dys)function has proven more elusive. The present paper aims to review several cognitive evaluation methods, discussing their advantages and disadvantages as well as their potential clinical applications in evaluating the dynamics of the recovery of cognitive function after anesthesia and surgery. The current availability of easy to use computerized tests might provide the tools necessary to identify patients at risk, and promptly provide them with the adequate course of action.

Cognitive decline in the middle-aged after surgery and anaesthesia: results from the Wisconsin Registry for Alzheimer's Prevention cohort

Surgery and anaesthesia might affect cognition in middle-aged people without existing cognitive dysfunction. We measured memory and executive function in 964 participants, mean age 54 years, and again four years later, by when 312 participants had had surgery and 652 participants had not. Surgery between tests was associated with a decline in immediate memory by one point (out of a maximum of 30), p = 0.013: memory became abnormal in 77 out of 670 participants with initially normal memory, 21 out of 114 (18%) of whom had had surgery compared with 56 out of 556 (10%) of those who had not, p = 0.02. The number of operations was associated with a reduction in immediate memory on retesting, beta coefficient (SE) 0.08 (0.03), p = 0.012. Working memory decline was also associated with longer cumulative operations, beta coefficient (SE) -0.01 (0.00), p = 0.028. A reduction in cognitive speed and flexibility was associated with worse ASA physical status, beta coefficient (SE) 0.55 (0.22) and 0.37 (0.17) for ASA 1 and 2 vs. 3, p = 0.035. However, a decline in working memory was associated with better ASA physical status, beta coefficient (SE) -0.48 (0.21) for ASA 1 vs. 3, p = 0.01.

Exercise Prevents Enhanced Postoperative Neuroinflammation and Cognitive Decline and Rectifies the Gut Microbiome in a Rat Model of Metabolic Syndrome

Introduction

Postoperative cognitive decline (PCD) can affect in excess of 10% of surgical patients and can be considerably higher with risk factors including advanced age, perioperative infection, and metabolic conditions such as obesity and insulin resistance. To define underlying pathophysiologic processes, we used animal models including a rat model of metabolic syndrome generated by breeding for a trait of low aerobic exercise tolerance. After 35 generations, the low capacity runner (LCR) rats differ 10-fold in their aerobic exercise capacity from high capacity runner (HCR) rats. The LCR rats respond to surgical procedure with an abnormal phenotype consisting of exaggerated and persistent PCD and failure to resolve neuroinflammation. We determined whether preoperative exercise can rectify the abnormal surgical phenotype.

Materials and methods

Following institutional approval of the protocol each of male LCR and male HCR rats were randomly assigned to four groups and subjected to isoflurane anesthesia and tibia fracture with internal fixation (surgery) or anesthesia alone (sham surgery) and to a preoperative exercise regimen that involved walking for 10 km on a treadmill over 6 weeks (exercise) or being placed on a stationary treadmill (no exercise). Feces were collected before and after exercise for assessment of gut microbiome. Three days following surgery or sham surgery the rats were tested for ability to recall a contextual aversive stimulus in a trace fear conditioning paradigm. Thereafter some rats were euthanized and the hippocampus harvested for analysis of inflammatory mediators. At 3 months, the remainder of the rats were tested for memory recall by the probe test in a Morris Water Maze.

Results

Postoperatively, LCR rats exhibited exaggerated cognitive decline both at 3 days and at 3 months that was prevented by preoperative exercise. Similarly, LCR rats had excessive postoperative neuroinflammation that was normalized by preoperative exercise. Diversity of the gut microbiome in the LCR rats improved after exercise.

Discussion

Preoperative exercise eliminated the metabolic syndrome risk for the abnormal surgical phenotype and was associated with a more diverse gut microbiome. Prehabilitation with exercise should be considered as a possible intervention to prevent exaggerated and persistent PCD in high-risk settings.

Lasting impact of general anaesthesia on the brain: mechanisms and relevance

General anaesthesia is usually considered to safely induce a reversible brain state allowing the performance of surgery under optimal conditions. An increasing number of clinical and experimental observations, however, suggest that anaesthetic drugs, especially when they are administered at the extremes of age, can trigger long-term morphological and functional alterations in the brain. Here, we review available mechanistic data linking general-anaesthesia exposure to impaired cognitive performance in both young and mature nervous systems. We also provide a critical appraisal of the translational value of animal models and highlight the important challenges that need to be addressed to strengthen the link between laboratory work and clinical investigations in the field of anaesthesia-neurotoxicity research.

Mild Cognitive Impairment and Exposure to General Anesthesia for Surgeries and Procedures: A Population-Based Case-Control Study

BACKGROUND

To examine whether exposure to general anesthesia for procedures at age ≥40 years is associated with prevalent mild cognitive impairment (MCI) in the elderly.

METHODS

A case-control study nested within a population-based cohort. Olmsted County, Minnesota, residents, aged 70-91 years, underwent baseline evaluations that included the Clinical Dementia Rating scale, a neurologic evaluation, and neuropsychologic testing. Individuals identified with MCI (cases) at enrollment were matched 1:2 on age, sex, education, and apolipoprotein genotype with participants who were cognitively normal at the time of the index visit. Medical records from age 40 years until the index visit were reviewed to determine exposures to general anesthesia. Conditional logistic regression, taking into account the matched set study design and adjusting for MCI risk factors, was used to assess whether exposure to anesthesia after the age of 40 years was associated with prevalent MCI.

RESULTS

A total of 387 Mayo Clinic Study of Aging participants (219 males, 168 females) were diagnosed with MCI at enrollment with mean age of 81 ± 5 years. Exposure to general anesthesia after the age of 40 years was not significantly associated with prevalent MCI when analyzed as a dichotomous variable (any versus none, adjusted odds ratio, 0.97 [95% confidence interval, 0.68-1.40]) or the number of exposures (odds ratio, 1.13 [0.74-1.72], 0.81 [0.53-1.22], and 1.03 [0.67-1.58] for 1, 2-3, and ≥4 exposures, respectively, with no exposure as the reference). Similar results were obtained for exposure to anesthesia after the age of 60 years and during 5, 10, and 20 years before the first visit.

CONCLUSIONS

Exposure to general anesthesia for procedures at age ≥40 years was not associated with prevalent MCI in the elderly.

Orthopedic surgery modulates neuropeptides and BDNF expression at the spinal and hippocampal levels

Pain is a critical component hindering recovery and regaining of function after surgery, particularly in the elderly. Understanding the role of pain signaling after surgery may lead to novel interventions for common complications such as delirium and postoperative cognitive dysfunction. Using a model of tibial fracture with intramedullary pinning in male mice, associated with cognitive deficits, we characterized the effects on the primary somatosensory system. Here we show that tibial fracture with pinning triggers cold allodynia and up-regulates nerve injury and inflammatory markers in dorsal root ganglia (DRGs) and spinal cord up to 2 wk after intervention. At 72 h after surgery, there is an increase in activating transcription factor 3 (ATF3), the neuropeptides galanin and neuropeptide Y (NPY), brain-derived neurotrophic factor (BDNF), as well as neuroinflammatory markers including ionized calcium-binding adaptor molecule 1 (Iba1), glial fibrillary acidic protein (GFAP), and the fractalkine receptor CX3CR1 in DRGs. Using an established model of complete transection of the sciatic nerve for comparison, we observed similar but more pronounced changes in these markers. However, protein levels of BDNF remained elevated for a longer period after fracture. In the hippocampus, BDNF protein levels were increased, yet there were no changes in Bdnf mRNA in the parent granule cell bodies. Further, c-Fos was down-regulated in the hippocampus, together with a reduction in neurogenesis in the subgranular zone. Taken together, our results suggest that attenuated BDNF release and signaling in the dentate gyrus may account for cognitive and mental deficits sometimes observed after surgery.

A call for comparative effectiveness research to learn whether routine clinical care decisions can protect from dementia and cognitive decline

Common diseases like diabetes, hypertension, and atrial fibrillation are probable risk factors for dementia, suggesting that their treatments may influence the risk and rate of cognitive and functional decline. Moreover, specific therapies and medications may affect long-term brain health through mechanisms that are independent of their primary indication. While surgery, benzodiazepines, and anti-cholinergic drugs may accelerate decline or even raise the risk of dementia, other medications act directly on the brain to potentially slow the pathology that underlies Alzheimer’s and other dementia. In other words, the functional and cognitive decline in vulnerable patients may be influenced by the choice of treatments for other medical conditions. Despite the importance of these questions, very little research is available. The Alzheimer’s Drug Discovery Foundation convened an advisory panel to discuss the existing evidence and to recommend strategies to accelerate the development of comparative effectiveness research on how choices in the clinical care of common chronic diseases may protect from cognitive decline and dementia.