Preoperative cognitive function as a risk factor of postoperative delirium in cancer surgeries: A systematic review and meta-analysis

Postoperative delirium (POD) after cancer surgeries can be a result of chemo brain, anesthesia, surgery duration, and preoperative cognitive impairment. Although older age and preoperative cognitive dysfunction were reported to increase the risk of POD in noncardiac surgery, the role of preoperative cognitive function and age in the development of POD after all types of cancer surgeries is not clear. This study aimed to determine the relationship between preoperative cognitive function and likelihood of POD after cancer surgeries. This study used three main online databases and followed PRISMA guidelines. English language original articles that examined preoperative cognitive function before solid tumor cancer surgery and assessed patients for postoperative delirium were included. We employed the random effect meta-analysis method. The overall incidence of POD ranged from 8.7% to 50.9%. The confusion assessment method was the most common tool used to assess delirium. Mini-mental state evaluation (MMSE), Mini-cog, and Montreal cognitive assessment were the most common tools to assess cognitive function. The pooled (total observation = 4676) random effects SMD was estimated at -0.84 (95% confidence interval [CI]: -1.30 to -0.31), indicating that lower MMSE scores before surgery are associated with a higher risk of POD. The pooled (total observation = 2668) random effects OR was estimated at 5.17 (95% CI: 2.51 to -10.63), indicating preoperative cognitive dysfunction can significantly predict the occurrence of POD after cancer surgeries. In conclusion, preoperative cognitive function is an independent and significant predictor of POD after solid tumor cancer surgeries.

Outcomes associated with postoperative cognitive dysfunction: a systematic review and meta-analysis

BACKGROUND

Postoperative cognitive dysfunction (POCD) manifests as a subtle decline in cognition, potentially leading to unfavourable postoperative outcomes. We explored the impact of POCD on physical function, length of hospital stay (LOS), dementia and mortality outcomes.

METHODS

PubMed and Scopus were searched until May 2023. All studies of major surgical patients that assessed POCD and outcomes of interest were included. POCD effects were stratified by surgery type (cardiac and noncardiac) and time of POCD assessment (<30 and ≥30 days postsurgery).

RESULTS

Of 2316 studies, 20 met the inclusion criteria. POCD was not associated with functional decline postsurgery. Patients who experienced POCD postcardiac surgery had an increased relative risk (RR) of death of 2.04 [(95% CI: 1.18, 3.50); I2 = 0.00%]. Sensitivity analyses showed associations with intermediate-term mortality among noncardiac surgical patients, with an RR of 1.84 [(95% CI: 1.26, 2.71); I2 = 0.00%]. Patients who developed POCD <30 days postcardiac and noncardiac surgeries experienced longer LOS than those who did not [mean difference (MD) = 1.37 days (95% CI: 0.35, 2.39); I2 = 92.38% and MD = 1.94 days (95% CI: 0.48, 3.40); I2 = 83.29%, respectively]. Postoperative delirium (POD) may contribute to the heterogeneity observed, but limited data were reported within the studies included.

CONCLUSIONS

Patients undergoing cardiac and noncardiac surgeries who developed POCD <30 days postsurgery had poorer outcomes and an increased risk of premature death. Early recognition of perioperative neurocognitive disorders in at-risk patients may enable early intervention. However, POD may confound our findings, with further studies necessary to disentangle the effects of POD from POCD on clinical outcomes.

The role of anesthesia in peri‑operative neurocognitive disorders: Molecular mechanisms and preventive strategies

Peri-operative neurocognitive disorders (PNDs) include postoperative delirium (POD) and postoperative cognitive dysfunction (POCD). Children and the elderly are the two populations most vulnerable to the development of POD and POCD, which results in both high morbidity and mortality. There are many factors, including neuroinflammation and oxidative stress, that are associated with POD and POCD. General anesthesia is a major risk factor of PNDs. However, the molecular mechanisms of PNDs are poorly understood. Dexmedetomidine (DEX) is a useful sedative agent with analgesic properties, which significantly improves POCD in elderly patients. In this review, the current understanding of anesthesia in PNDs and the protective effects of DEX are summarized, and the underlying mechanisms are further discussed.

Postoperative cognitive dysfunction: a concept analysis

BACKGROUND

Post-operative cognitive dysfunction (POCD) is a concern for clinicians that often presents post-surgery where generalized anesthesia has been used. Its prevalence ranges from 36.6% in young adults to 42.4% in older individuals. Conceptual clarity for POCD is lacking in the currently body literature. Our two-fold purpose of this concept analysis was to (1) critically appraise the various definitions, while also providing the best definition, of POCD and (2) narratively synthesize the attributes, surrogate or related terms, antecedents (risk factors), and consequences of the concept.

METHOD

The reporting of our review was guided by the PRISMA statement and the 6-step evolutionary approach to concept analysis developed by Rodgers. Three databases, including Medline, CINAHL, and Web of Science, were searched to retrieve relevant literature on the concept of POCD. Two independent reviewers conducted abstract and full-text screening, data extraction, and appraisal. The review process yielded a final set of 86 eligible articles.

RESULT

POCD was defined with varying severities ranging from subtle-to-extensive cognitive changes (1) affecting single or multiple cognitive domains that manifest following major surgery (2), is transient and reversible, and (3) may last for several weeks to years. The consequences of POCD may include impaired quality of life, resulting from withdrawal from the labor force, increased patients' dependencies, cognitive decline, an elevated risk of dementia, rising healthcare costs, and eventual mortality.

CONCLUSION

This review resulted in a refined definition and comprehensive analysis of POCD that can be useful to both researchers and clinicians. Future research is needed to refine the operational definitions of POCD so that they better represent the defining attributes of the concept.

Anaesthesia-related cognitive dysfunction following cardiothoracic surgery in late middle-age and younger adults: A scoping review

BACKGROUND

The incidence of postoperative cognitive dysfunction (POCD) is notably high after cardiac surgery, ranging from 25% to 30%, and is associated with a lower quality of life, increased patient dependency, and heightened mortality. Anaesthesia during cardiothoracic surgery significantly contributes to the risk of POCD in older adults by adversely affecting the brain, including reductions in blood flow and oxygen levels.

AIM

This review aimed to evaluate factors associated with anaesthesia-related postoperative cognitive dysfunction (POCD) among adults younger than 65 years who underwent cardiothoracic surgeries.

STUDY DESIGN

A systematic keyword search, following the scoping review framework, was performed in the PubMed and CINAHL databases. Original English-language studies that included adults younger than 65 years and addressed cognitive function after surgery along with anaesthesia management were included. Retrospective studies, animal research and in vitro and in vivo studies were excluded.

RESULTS

Twenty-three articles were included (65.2% interventional studies). All studies lacked theoretical or conceptual frameworks. Ketamine's neuroprotective potential is questionable, and intravenous lidocaine may be considered a possible early agent for preventing POCD, but long-term effectiveness is uncertain. Compared to inhalational anaesthesia, total intravenous anaesthesia (TIVA) may be related to a decreased incidence of POCD. Variation in POCD assessment impacted the lack of homogeneity in obtained data. Moreover, the shorter-term timing of POCD evaluation such as in early days after surgery could be greatly influenced by medication and delirium.

CONCLUSION

Although strategies such as TIVA, the use of neuroprotective anaesthetics and comprehensive preoperative assessments are suggested to prevent POCD, this multifactorial phenomenon cannot be explicitly attributed solely to anaesthetics or anaesthesia-related techniques. Use of standardized, reliable and valid tools for POCD assessment is encouraged for cross-study comparison.

RELEVANCE TO CLINICAL PRACTICE

Nurses and certified nurse anaesthetists must be aware of risk factors for postoperative delirium and POCD so they can assess patients before and after surgery. Patients and caregivers need to be educated about cognitive changes after surgery and advised to report them to their health care provider if they occur.

Middle aged CAMKII-Cre:Cbsfl/fl mice: a new model for studying perioperative neurocognitive disorders

Postoperative complications, such as perioperative neurocognitive disorders (PND), have become a major issue affecting surgical outcomes. However, the mechanism of PND remains unclear, and stable animal models of middle-aged PND are lacking. S-adenosylmethionine (SAM), a cystathionine beta-synthase (CBS) allosteric activator, can reduce the level of plasma homocysteine and prevent the occurrence of PND. However, the time and resource-intensive process of constructing models of PND in elderly animals have limited progress in PND research and innovative therapy development. The present study aimed to construct a stable PND model in middle-aged CAMKII-Cre:Cbsfl/fl mice whose Cbs was specifically knocked out in CAMKII positive neurons. Behavioral tests showed that these middle-aged mice displayed cognitive deficits which were aggravated by exploratory laparotomy under isoflurane anesthesia. Compared with typical PND mice which were 18-month-old, these middle-aged mice showed similar cognitive deficits after undergoing exploratory laparotomy under isoflurane anesthesia. Though there was no significant difference in the number of neurons in either the hippocampus or the cortex, a significant increase in numbers of microglia and astrocytes in the hippocampus was observed. These indicate that middle-aged CAMKII-Cre:Cbsfl/fl mice can be used as a new PND model for mechanistic studies and therapy development for PND.

Postoperative cognitive recovery and prevention of postoperative cognitive complications in the elderly patient

Elderly patients undergoing surgery are at higher risk of life-altering and costly complications. This challenge is increasingly recognized with the growing geriatric surgical population. Advanced age and comorbid conditions, such as disability and frailty that often develop with age, are all independent risk factors of postoperative morbidity and mortality. A common factor in this age group is cognitive impairment, which poses a challenge for the patient and clinician in the perioperative setting. It affects the capacity for informed consent and limits optimization before surgery; furthermore, an existing impairment may progress in severity during the perioperative period, and new onset of signs of delirium or postoperative cognitive dysfunction may arise during postoperative recovery. In this article, we aim to review the current literature examining the latest definitions, diagnostic criteria, and preventive strategies that may ameliorate postoperative cognitive complications.

Perioperative Neurocognitive Disorders in Adults Requiring Cardiac Surgery: Screening, Prevention, and Management

Neurocognitive changes are the most common complication after cardiac surgery, ranging from acute postoperative delirium to prolonged postoperative neurocognitive disorder. Changes in cognition are distressing to patients and families and associated with worse outcomes overall. This review outlines definitions and diagnostic criteria, risk factors for, and mechanisms of Perioperative Neurocognitive Disorders and offers strategies for preoperative screening and perioperative prevention and management of neurocognitive complications.

Preoperative Factors Predict Memory Decline After Coronary Artery Bypass Grafting or Percutaneous Coronary Intervention in an Epidemiological Cohort of Older Adults

Background Durable memory decline may occur in older adults after surgical (coronary artery bypass grafting [CABG]) or nonsurgical (percutaneous coronary intervention) coronary revascularization. However, it is unknown whether individual memory risk can be predicted. We reanalyzed an epidemiological cohort of older adults to predict memory decline at ≈1 year after revascularization. Methods and Results We studied Health and Retirement Study participants who underwent CABG or percutaneous coronary intervention at age ≥65 years between 1998 and 2015 and participated in ≥1 biennial postprocedure assessment. Using a memory score based on direct and proxy cognitive tests, we identified participants whose actual postprocedure memory score was 1-2 ("mild") or >2 ("major") SDs below expected postprocedure performance. We modeled probability of memory decline using logistic regression on preoperatively known factors and evaluated model discrimination and calibration. A total of 1390 participants (551 CABG, 839 percutaneous coronary intervention) underwent CABG/percutaneous coronary intervention at 75±6 years old; 40% were women. The cohort was 83% non-Hispanic White, 8.4% non-Hispanic Black, 6.4% Hispanic ethnicity, and 1.7% from other groups masked by the HRS (Health and Retirement Study) to preserve participant confidentiality. At a median of 1.1 (interquartile range, 0.6-1.6) years after procedure, 267 (19%) had mild memory decline and 88 (6.3%) had major memory decline. Factors predicting memory decline included older age, frailty, and off-pump CABG; obesity was protective. The optimism-corrected area under the receiver operator characteristic curve was 0.73 (95% CI, 0.71-0.77). A cutoff of 50% probability of memory decline identified 14% of the cohort as high risk, and was 94% specific and 30% sensitive for late memory decline. Conclusions Preoperative factors can be used to predict late memory decline after coronary revascularization in an epidemiological cohort with high specificity.

Extended anesthesia exposure for abdominal and pelvic procedures in older adults with colorectal cancer: Associations with chart dementia diagnoses

BACKGROUND

We hypothesized that cumulative anesthesia exposure over the course of routine treatment of colorectal cancer in older adults can increase long-term risk of Alzheimer's disease (AD), Alzheimer's disease-related dementias (ADRD), and other chronic neurocognitive disorders (CND).

METHODS

We conducted a SEER-Medicare-based retrospective cohort study of 84,770 individuals age 65 years and older diagnosed with colorectal cancer between 1998 and 2007 using a proportional hazards model with inverse probability weighted estimators. The primary exploratory variable was a time-variant measure of cumulative anesthesia exposure for abdominal and pelvic procedures, updated continuously.

RESULTS

Our primary outcomes, AD and ADRD, occurred in 6005/84,770 (7.1%) and 14,414/83,444 (17.3%) individuals respectively. No statistically significant association was found between cumulative anesthesia exposure and AD (hazard ratio [HR], 0.993; 95% CI, 0.973-1.013). However, it was moderately associated with the risk of ADRD (HR, 1.016; 95% CI, 1.004-1.029) and some secondary outcomes including most notably: cerebral degeneration (HR, 1.048; 95% CI, 1.033-1.063), hepatic encephalopathy (HR, 1.133; 95% CI, 1.101-1.167), encephalopathy-not elsewhere classified (HR,1.095; 95% CI: 1.076-1.115), and incident/perioperative delirium (HR, 1.022; 95% CI, 1.012-1.032). Furthermore, we observed an association between perioperative delirium and increased risk of AD (HR, 2.05; 95% CI, 1.92-2.09).

CONCLUSION

Cumulative anesthesia exposure for abdominal and pelvic procedures was not associated with increased risk of AD directly and had a small but statistically significant association with ADRD and a number of other CNDs. Cumulative anesthesia exposure was also associated with perioperative delirium, which had an independent adverse association with AD risk.

Postoperative Cognitive Dysfunction and Alzheimer’s Disease: A Transcriptome-Based Comparison of Animal Models

Background

Postoperative cognitive dysfunction (POCD) is a common complication characterized by a significant cognitive decline. Increasing evidence suggests an association between the pathogenesis of POCD and Alzheimer’s disease (AD). However, a comprehensive understanding of their relationships is still lacking.

Methods

First, related databases were obtained from GEO, ArrayExpress, CNGB, and DDBJ repositories. De novo analysis was performed on the raw data using a uniform bioinformatics workflow. Then, macro- and micro-level comparisons were conducted between the transcriptomic changes associated with AD and POCD. Lastly, POCD was induced in male C57BL/6j mice and the hippocampal expression levels of mRNAs of interest were verified by PCR and compared to those in AD congenic models.

Results

There was a very weak correlation in the fold-changes in protein-coding transcripts between AD and POCD. Overall pathway-level comparison suggested that AD and POCD are two disease entities. Consistently, in the classical AD pathway, the mitochondrial complex and tubulin mRNAs were downregulated in both the POCD hippocampus and cortex. POCD and AD hippocampi might share the same pathways, such as tryptophan metabolism, but undergo different pathological changes in phagosome and transferrin endocytosis pathways. The core cluster in the hippocampal network was mainly enriched in mitosis-related pathways. The hippocampal expression levels of genes of interest detected by PCR showed good consistency with those generated by high throughput platforms.

Conclusion

POCD and AD are associated with different transcriptomic changes despite their similar clinical manifestations. This study provides a valuable resource for identifying biomarkers and therapeutic targets for POCD.

Perioperative neurocognitive disorders: A narrative review focusing on diagnosis, prevention, and treatment

Perioperative neurocognitive disorders (NCDs) refer to neurocognitive abnormalities detected during the perioperative periods, including preexisting cognitive impairment, preoperative delirium, delirium occurring up to 7 days after surgery, delayed neurocognitive recovery, and postoperative NCD. The Diagnostic and Statistical Manual of Mental Disorders‐5th edition (DSM‐5) is the golden standard for diagnosing perioperative NCDs. Given the impracticality of using the DSM‐5 by non‐psychiatric practitioners, many diagnostic tools have been developed and validated for different clinical scenarios. The etiology of perioperative NCDs is multifactorial and includes predisposing and precipitating factors. Identifying these risk factors is conducive to preoperative risk stratification and perioperative risk reduction. Prevention for perioperative NCDs should include avoiding possible contributors and implementing nonpharmacologic and pharmacological interventions. The former generally includes avoiding benzodiazepines, anticholinergics, prolonged liquid fasting, deep anesthesia, cerebral oxygen desaturation, and intraoperative hypothermia. Nonpharmacologic measures include preoperative cognitive prehabilitation, comprehensive geriatric assessment, implementing fast‐track surgery, combined use of regional block, and sleep promotion. Pharmacological measures including dexmedetomidine, nonsteroidal anti‐inflammatory drugs, and acetaminophen are found to have beneficial effects. Nonpharmacological treatments are the first‐line measures for established perioperative NCDs. Pharmacological treatments are still limited to severely agitated or distressed patients.

Neuropsychological Tests in Post-operative Cognitive Dysfunction: Methods and Applications

Post-operative cognitive dysfunction (POCD) is a neurological complication that relatively frequently occurs in older people after anesthesia/surgery, with varying durations and significant differences in the severity of cognitive impairment. POCD is mainly characterized by memory loss mostly without consciousness disorders, accompanied by abnormal emotions, behaviors, and language, mostly without consciousness disorder. The clinical performance of POCD lacks specificity but can reflect the severity of cognitive impairment in patients. The diagnosis of POCD cannot be separated from the evaluation of perioperative cognitive function of patients, and the more popular and accepted method is neuropsychological tests (NPTs).

Intranasal administration of 40 and 80 units of insulin does not cause hypoglycemia during cardiac surgery: a randomized controlled trial

PURPOSE

Intranasal insulin administration may improve cognitive function in patients with dementia and may prevent cognitive problems after surgery. Although the metabolic effects of intranasal insulin in non-surgical patients have been studied, its influence on glucose concentration during surgery is unknown.

METHODS

We conducted a randomized, double-blind, placebo-contolled trial in patients scheduled for elective cardiac surgery. Patients with type 2 diabetes mellitus (T2DM) and non-T2DM patients were randomly allocated to one of three groups (normal saline, 40 international units [IU] of intranasal insulin, and 80 IU intranasal insulin). Insulin was given after the induction of general anesthesia. Glucose and plasma insulin concentrations were measured in ten-minute intervals during the first hour and every 30 min thereafter. The primary outcome was the change in glucose concentration 30 min after intranasal insulin administration.

RESULTS

A total of 115 patients were studied, 43 of whom had T2DM. In non-T2DM patients, 40 IU intranasal insulin did not affect glucose concentration, while 80 IU intranasal insulin led to a statistically significant but not clinically important decrease in blood glucose levels (mean difference, 0.4 mMol·L^-1; 95% confidence interval, 0.1 to 0.7). In T2DM patients, neither 40 IU nor 80 IU of insulin affected glucose concentration. No hypoglycemia (< 4.0 mMol·L^-1) was observed after intranasal insulin administration in any patients. In non-T2DM patients, changes in plasma insulin were similar in the three groups. In T2DM patients, there was an increase in plasma insulin concentrations ten minutes after administration of 80 IU of intranasal insulin compared with saline.

CONCLUSIONS

In patients with and without T2DM undergoing elective cardiac surgery, intranasal insulin administration at doses as high as 80 IU did not cause clinically important hypoglycemia.

TRIAL REGISTRATION

www.ClinicalTrials.gov (NCT02729064); registered 5 April 2016.

Time course of dementia following sepsis in German health claims data

Objective

We evaluated the short-, medium-, and long-term effects of sepsis on dementia incidence using German health claims data.

Methods

A total of 161,567 patients (65 years or older) were followed from 2004 to 2015 at quarterly intervals. Time since sepsis was categorized into 0 (the effective quarter of sepsis diagnosis), 1–8, and ≥9 quarters since the latest diagnosis of sepsis, taking into account admission to intensive care unit and controlling for delirium, surgery, age, sex, and comorbidities. Incident dementia was defined for all persons who did not have a validated dementia diagnosis in 2004 and 2005 and who received a first-time, valid diagnosis between 2006 and 2015.

Results

During the quarter of sepsis diagnosis, patients not admitted to intensive care had a 3.14-fold (95% CI 2.83–3.49) increased risk, and those with intensive care stay had a 2.22-fold (95% CI: 1.83–2.70) increased risk of receiving an incident dementia diagnosis compared with patients without sepsis. The impact of sepsis on incident dementia remained in the following 2 years, remitting only thereafter.

Conclusions

For sepsis survivors, medium-term dementia risk remains elevated, whereas long-term risk may reach the level of those without sepsis, even after controlling for delirium. These findings encourage identifying modifiable components of hospital and rehabilitation care.

NLRP3 inflammasomes are involved in the progression of postoperative cognitive dysfunction: from mechanism to treatment

Postoperative cognitive dysfunction (POCD) involves patient memory and learning decline after surgery. POCD not only presents challenges for postoperative nursing and recovery but may also cause permanent brain damage for patients, including children and the aged, with vulnerable central nervous systems. Its occurrence is mainly influenced by surgical trauma, anesthetics, and the health condition of the patient. There is a lack of imaging and experimental diagnosis; therefore, patients can only be diagnosed by clinical observation, which may underestimate the morbidity, resulting in decreased treatment efficacy. Except for symptomatic support therapy, there is a relative lack of effective drugs specific for the treatment of POCD, because the precise mechanism of POCD remains to be determined. One current hypothesis is that postoperative inflammation promotes the progression of POCD. Accumulating research has indicated that overactivation of NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasomes contribute to the POCD progression, suggesting that targeting NLRP3 inflammasomes may be an effective therapy to treat POCD. In this review, we summarize recent studies and systematically describe the pathogenesis, treatment progression, and potential treatment options of targeting NLRP3 inflammasomes in POCD patients.

Exogenous hydrogen sulfide alleviates surgery-induced neuroinflammatory cognitive impairment in adult mice by inhibiting NO signaling

Background

To investigate the effect and mechanisms of exogenous hydrogen sulfide in surgery-induced neuroinflammatory cognitive dysfunction.

Methods

C57BL/6 J male mice (n = 140) were used and randomly divided into seven groups: the sham group, surgery group, GYY4137 group, L-NAME group, surgery+GYY4137 group, surgery +L-NAME group, and surgery+GYY4137 + L-NAME group. After the interventions, open field tests (OFT) and the Morris water maze (MWM) test were conducted to evaluate learning and memory abilities in the mice. ELISAs, nitrate reductase assays, and Western blots (WB) were conducted to evaluate interleukin-1 beta (IL-1β), tumor necrosis factor-alpha (TNF-α), nitric oxide (NO), inducible nitric oxide synthase (iNOS), malondialdehyde (MDA), and antioxidant enzyme superoxide dismutase (SOD) levels. Furthermore, the expression level of microglial marker ionized calcium binding adaptor molecule 1 (IBA) in the hippocampal CA1 and CA3 areas was detected by an immunohistochemical (IHC) assay and apoptotic cells were observed using terminal deoxynucleotidyl transferase dUTP end-labeling (TUNEL) staining kits.

Results

We found that surgery induced neuroinflammatory cognitive dysfunction, oxidative stress, microglial activation, and cell apoptosis in the hippocampus. Moreover, following surgery, NO and iNOS levels were elevated in the hippocampus. Notably, all the effects caused by surgery were reversed by the H₂S donor GYY4137 or the iNOS inhibitor N(gamma)-nitro-L-arginine methyl ester (L-NAME). However, the combined application of GYY4137 and L-NAME was not superior to treatment with either agent alone and the effect of GYY4137 was similar to that of L-NAME.

Conclusion

The long-acting hydrogen sulfide donor GYY4137 had an ability to reversed the cognitive deficits and inflammation caused by carotid artery exposure surgery. This implies that NO signaling pathways might participate in this process. These results indicate that exogenous H₂S may be a promising therapy for POCD.

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.

Special Considerations for the Aging Brain and Perioperative Neurocognitive Dysfunction

Postoperative delirium and postoperative cognitive dysfunction (POCD) occur commonly in older adults after surgery and are frequently underrecognized. Delirium has been associated with worse outcomes, and both delirium and cognitive dysfunction increase the risk of long-term cognitive decline. Although the pathophysiology of delirium and POCD have not been clearly defined, risk factors for both include increasing age, lower levels of education, and baseline cognitive impairment. In addition, developing delirium increases the risk of POCD. This article examines interventions that may reduce the risk of developing delirium and POCD and improve long-term recovery and outcomes in the vulnerable older population.

Neuropsychological Functioning in Older Adults with Obesity: Implications for Bariatric Surgery

Bariatric surgery is the most effective approach to treating morbid obesity, resulting in decreased morbidity, mortality, and improved quality of life. Research on outcomes has generally been restricted to young and middle-aged adults, despite a growing epidemic of obesity in older adults. The use of bariatric surgery has been limited in older individuals, in part due to concerns that preexisting cognitive dysfunction increases the risk of poor post-surgical outcomes, including cognitive decline. The literature on the relationship between obesity and cognition in older adults is emerging, but fraught by several methodological limitations. While there is insufficient research to determine the nature of cognitive outcomes following bariatric surgery in older adults, the aim of this paper is to review the existing evidence and make the case for further study.

Neurocognitive Function after Cardiac Surgery: From Phenotypes to Mechanisms

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

Varenicline reduces DNA damage, tau mislocalization and post surgical cognitive impairment in aged mice

Postoperative cognitive dysfunction (POCD) occurs more frequently in elderly patients undergoing major surgery. Age associated cholinergic imbalance may exacerbate postoperative systemic and neuroinflammation, but the effect nicotinic acetylcholine receptor (nAchR) stimulation on the development of POCD remains unclear. Aged male C57BL/6N mice (18 months old) underwent a midline laparotomy or were exposed to sevoflurane anesthesia alone (4-5%), with or without concomitant varenicline, a partial nAchR, at 1 mg/kg/day. Laparotomy increased pro-inflammatory cytokines in the liver and hippocampus (IL-1β and MCP-1) and induced a decline in cognitive performance, indicated by lower discrimination index in the Novel Object Recognition test, greater error number and longer escape latency in the Y-maze test. Glia activation, aberrant tau phosphorylation (AT8) and accumulation of phosphorylated H2AX in the hippocampus were detectable up to postoperative day 14, with neuronal apoptosis seen in the hippocampus. Perioperative varenicline attenuated the cognitive decline and associated tau protein mislocalization, DNA damage and neuronal apoptosis. The modulation of JAK2/STAT3 signaling may play a critical role in this process. Neuroinflammation, tau phosphorylation and DNA damage contribute to the development of cognitive dysfunction following laparotomy. Cholinergic stimulation by varenicline attenuated these changes through preventing the mislocalization of phosphorylated tau and DNA damage.

Neuroanesthesiology Update

We provide a synopsis of innovative research, recurring themes, and novel experimental findings pertinent to the care of neurosurgical patients and critically ill patients with neurological diseases. We cover the following broad topics: general neurosurgery, spine surgery, stroke, traumatic brain injury, monitoring, and anesthetic neurotoxicity.

Anesthesia and the risk of dementia in the elderly

Cognitive complications are common after surgery in the elderly, and with an increased number of elderly patients undergoing surgery, a potential impact of anaesthesia and surgery on long term cognition, and especially dementia would be concerning. The question whether anaesthesia and surgery in itself induce structural changes in the brain and thereby cognitive deterioration, or reveal a preexisting cognitive impairment remains unresolved. Several studies show an increased risk of reversible cognitive impairment after surgery in the elderly, but the risk of inducing dementia remains speculative. Further studies are needed to elucidate this potential association. Meanwhile, elderly frail patients need to be closely followed including preoperative cognitive screening, since they are at increased risk of cognitive deterioration after surgery and discharge.

Preoperative dementia is associated with increased cost and complications after vascular surgery

OBJECTIVE

Dementia represents a major risk factor for medical complications and has been linked to higher rates of complication after surgery. Given the systemic nature of vascular disease, medical comorbidities significantly increase cost and complications after vascular surgery. We hypothesize that the presence of dementia is an independent predictor of increased postoperative complications and higher health care costs after vascular surgery.

METHODS

The Vascular Quality Initiative database was queried for all patients undergoing vascular surgery at a single academic medical center from 2012 to 2017. All modules were included (open abdominal aortic aneurysm, suprainguinal bypass, lower extremity bypass, amputation, carotid endarterectomy, endovascular aortic aneurysm repair, thoracic endovascular aortic aneurysm repair, and peripheral endovascular intervention). An institutional clinical data repository was queried to identify patients with International Classification of Diseases, Ninth Revision diagnosis codes for dementia as well as total hospital cost and long-term survival using Social Security records from the Virginia Department of Health. Hierarchical logistic and linear regression models were fit to assess risk-adjusted predictors of any complication and inflation-adjusted cost. Kaplan-Meier and Cox proportional hazards models were used for survival analysis.

RESULTS

A total of 2318 patients underwent vascular surgery and were captured by the Vascular Quality Initiative during the past 5 years, with 88 (3.8%) having a diagnosis of dementia. Patients with dementia were older and had higher rates of medical comorbidities, and the most common procedure was major amputation. In addition, dementia patients had a significantly higher rate of any complication (52% vs 16%; P < .0001) and increased 90-day mortality (14% vs 4.8%; P = .0002). Furthermore, dementia was associated with significant resource utilization, including preoperative length of stay (LOS), postoperative LOS, intensive care unit LOS, and inflation-adjusted total hospital cost (all P < .0001). Hierarchical modeling demonstrated that dementia was the strongest preoperative predictor for any complication (odds ratio, 8.64; P < .0001) and had the largest risk-adjusted impact on total hospital cost ($22,069; P < .0001). Finally, survival analysis demonstrated that dementia is independently associated with reduced survival after vascular surgery (hazard ratio, 1.37; P = .018).

CONCLUSIONS

This study demonstrated that dementia is one of the strongest predictors of any complication and increased hospital cost after vascular surgery. Given the high risk of clinical and financial maladies, patients with dementia should be carefully considered and counseled before undergoing vascular surgery.

Perioperative hyperglycemia and neurocognitive outcome after surgery: a systematic review

INTRODUCTION

Preliminary evidence suggest a possible relationship between perioperative hyperglycemia, postoperative delirium (POD) or cognitive dysfunction (POCD). We aim to present the available clinical evidence related to chronic (i.e. diabetes mellitus) or acute perioperative hyperglycemia as risk factors for POD/POCD.

EVIDENCE ACQUISITION

A literature search of EMBASE (via Ovid, 1974-present) online medical database and MEDLINE (via PubMed or Ovid, 1946-present) was performed. All types of clinical studies including randomized controlled trials, prospective, as well as retrospective cohort studies were screened. Clinical studies that reported original information on the relationship between diabetes mellitus (DM) and/or acute perioperative abnormal glucose levels and POD or POCD were selected. Reviews and editorials (i.e. articles not presenting original preclinical or clinical research) were excluded and case-reports were not considered for analysis.

EVIDENCE SYNTHESIS

Our search resulted in 2356 papers for screening, from which we selected 29 studies that met our inclusion criteria. DM was investigated in 24 observational papers, acute perioperative hyperglycemia in six observational studies and two randomized controlled trials examined the effect of perioperative glucose lowering on POD/POCD. Diabetes was associated with POD or POCD in 18/24 observational studies and 6/6 of the included observational studies found that perioperative hyperglycemia was associated with POD/POCD, independent of diabetes. The two randomized controlled trials had a different trial design and reported conflicting results.

CONCLUSIONS

According to the available evidence, DM and acute perioperative hyperglycemia may be associated with an increased risk for POD/POCD. These conclusions are based mostly on observational studies and deserve more and dedicated research. This systematic review may direct the design of future studies.

Anesthesia and Alzheimer disease – Current perceptions

Background and objectives

It has been speculated that the use of anesthetic agents may be a risk factor for the development of Alzheimer disease. The objective of this review is to describe and discuss pre-clinical and clinical data related to anesthesia and this disease.

Content

Alzheimer disease affects about 5% of the population over 65 years old, with age being the main risk factor and being associated with a high morbidity. Current evidence questions a possible association between anesthesia, surgery, and long-term cognitive effects, including Alzheimer disease. Although data from some animal studies suggest an association between anesthesia and neurotoxicity, this link remains inconclusive in humans. We performed a review of the literature in which we selected scientific articles in the PubMed database, published between 2005 and 2016 (one article from 1998 due to its historical relevance), in English, which address the possible relationship between anesthesia and Alzheimer disease. 49 articles were selected.

Conclusion

The possible relationship between anesthetic agents, cognitive dysfunction, and Alzheimer disease remains to be clarified. Prospective cohort studies or randomized clinical trials for a better understanding of this association will be required.

Associations Between Impaired Cerebral Blood Flow Autoregulation, Cerebral Oxygenation, and Biomarkers of Brain Injury and Postoperative Cognitive Dysfunction in Elderly Patients After Major Noncardiac Surgery

BACKGROUND

Increasing evidence links postoperative cognitive dysfunction (POCD) to surgery and anesthesia. POCD is recognized as an important neuropsychological adverse outcome in surgical patients, particularly the elderly. This prospective cohort study aimed to investigate whether POCD is associated with impaired intraoperative cerebral autoregulation and oxygenation, and increased levels of biomarkers of brain injury.

METHODS

Study subjects were patients ≥65 years of age scheduled for major noncardiac surgery. Cognitive function was assessed before and 1 week after surgery. POCD was diagnosed if a decline of >1 standard deviation of z-scores was present in ≥2 variables of the test battery. The incidence of POCD 1 week after surgery was modeled as a multivariable function of the index of autoregulation (MxA) and tissue oxygenation index (TOI), adjusting for baseline neuropsychological assessment battery (Consortium to Establish a Registry for Alzheimer's Disease-Neuropsychological Assessment Battery [CERAD-NAB]) total score and the maximum C-reactive protein (CRP) concentration. The biomarkers of brain injury neuron-specific enolase and S100β protein, age, and level of education were included in secondary multivariable logistic regression analyses.

RESULTS

Of the 82 patients who completed the study, 38 (46%) presented with POCD 1 week after surgery. In the multivariable regression analysis, higher intraoperative MxA (odds ratio [OR; 95% confidence interval (CI)], 1.39 [1.01-1.90] for an increase of 0.1 units, P = .08 after Bonferroni adjustment), signifying less effective autoregulation, was not associated with higher odds of POCD. The univariable logistic regression model for MxA yielded an association with POCD (OR [95% CI], 1.44 [1.06-1.95], P = .020). Tissue oxygenation index (1.12 [0.41-3.01] for an increase of 10%, P = 1.0 after Bonferroni adjustment) and baseline CERAD-NAB total score (0.80 [0.45-1.42] for an increase of 10 points, P = .45) did not affect the odds of POCD. POCD was associated with elevated CRP on postoperative day 2 (median [interquartile range]; 175 [81-294] vs 112 [62-142] mg/L, P = .033); however, the maximum CRP value (OR [95% CI], 1.35 [0.97-1.87] for a 2-fold increase, P = .07) had no distinct effect on POCD.

CONCLUSIONS

Impairment of intraoperative cerebral blood flow autoregulation is not predictive of early POCD in elderly patients, although secondary analyses indicate that an association probably exists.

Mind Over Matter? The Hidden Epidemic of Cognitive Dysfunction in the Older Surgical Patient

OBJECTIVE

The aim of this study was to highlight the vulnerability of the aging brain to surgery and anesthesia, examine postoperative cognitive outcomes, and recommend possible interventions.

BACKGROUND

Surgeons are facing increasingly difficult ethical and clinical decisions given the rapidly expanding aging demographic. Cognitive function is not routinely assessed either preoperatively or postoperatively. Potential short and long-term cognitive implications are rarely discussed with the patient despite evidence that postoperative cognitive impairment occurs in up to 65% of older patients. Furthermore, surgery may accelerate the trajectory of cognitive decline and dementia.

METHODS

An electronic search was conducted using Pubmed/Medline. References from selected studies were cross-referenced and relevant articles retrieved. Data were summarized in a narrative format.

RESULTS

There is a hidden epidemic of cognitive dysfunction in the perioperative setting. Up to 40% of patients who develop postoperative delirium (POD) never return to their preoperative cognitive baseline. POD can lead to postoperative cognitive dysfunction (POCD), a more prolonged cognitive impairment associated with longer length of hospital stay and cost, premature withdrawal from the workforce, and greater 1-year mortality. Standardized perioperative cognitive assessment is needed to enable progress. Improving outcomes will depend on a multifaceted approach, including correction of modifiable preoperative risk factors and prompt treatment of POD. Risk factors are discussed and possible interventional strategies are presented.

CONCLUSION

Closer preoperative collaboration between surgeons, geriatricians, and anesthetists will enable identification of complex at-risk older patients. A paradigm shift in the approach to management of the older surgical patient is critical to improve postoperative cognitive outcomes in modern surgery.

The effect of sugammadex on postoperative cognitive function and recovery

BACKGROUND AND OBJECTIVE

Sugammadex is the first selective relaxant binding agent. When compared with neostigmine, following sugammadex administration patients wake earlier and have shorter recovery times. In this study, we hypothesized that fast and clear awakening in patients undergoing general anesthesia has positive effects on cognitive functions in the early period after operation.

METHODS

Approved by the local ethical committee, 128 patients were enrolled in this randomized, prospective, controlled, double-blind study. Patients were allocated to either Sugammadex group (Group S) or the Neostigmine group (Group N). The primary outcome of the study was early postoperative cognitive recovery as measured by the Montreal Cognitive Assessment (MoCA) and Mini Mental State Examination (MMSE). After baseline assessment 12-24h before the operation. After the operation, when the Modified Aldrete Recovery Score was ≥9 the MMSE and 1h later the MoCA tests were repeated.

RESULTS

Although there was a reduction in MoCA and MMSE scores in both Group S and Group N between preoperative and postoperative scores, there was no statistically significant difference in the slopes (p>0.05). The time to reach TOF 0.9 was 2.19min in Group S and 6.47min in Group N (p<0.0001). Recovery time was 8.26min in Group S and 16.93min in Group N (p<0.0001).

CONCLUSION

We showed that the surgical procedure and/or accompanying anesthetic procedure may cause a temporary or permanent regression in cognitive function in the early postoperative period. However, better cognitive performance could not be proved in the Sugammadex compared to the Neostigmine.

Cognitive Functioning after Surgery in Middle-aged and Elderly Danish Twins

BACKGROUND

Postoperative cognitive dysfunction is common, but it remains unclear whether there are long-term adverse cognitive effects of surgery combined with anesthesia. The authors examined the association between exposure to surgery and level of cognitive functioning in a sample of 8,503 middle-aged and elderly twins.

METHODS

Results from five cognitive tests were compared in twins exposed to surgery, classified as major, minor, hip and knee replacement, or other, with those of a reference group without surgery using linear regression adjusted for sex and age. Genetic and shared environmental confounding was addressed in intrapair analyses of 87 monozygotic and 124 dizygotic same-sexed twin pairs in whom one had a history of major surgery and the other did not.

RESULTS

Statistically significantly lower composite cognitive score was found in twins with at least one major surgery compared with the reference group (mean difference, -0.27; 95% CI, -0.48 to -0.06), corresponding to one tenth of an SD, that is, a negligible effect size. In the intrapair analysis, the surgery-exposed co-twin had the lower cognitive score in 49% (95% CI, 42 to 56%) of the pairs. None of the other groups differed from the reference group except the knee and hip replacement group that tended to have higher cognitive scores (mean difference, 0.35; 95% CI, -0.18 to 0.87).

CONCLUSIONS

A history of major surgery was associated with a negligibly lower level of cognitive functioning. The supplementary analyses suggest that preoperative cognitive functioning and underlying diseases were more important for cognitive functioning in mid- and late life than surgery and anesthesia.

[The effect of sugammadex on postoperative cognitive function and recovery]

BACKGROUND AND OBJECTIVE

Sugammadex is the first selective relaxant binding agent. When compared with neostigmine, following sugammadex administration patients wake earlier and have shorter recovery times. In this study, we hypothesized that fast and clear awakening in patients undergoing general anesthesia has positive effects on cognitive functions in the early period after operation.

METHODS

Approved by the local ethical committee, 128 patients were enrolled in this randomized, prospective, controlled, double-blind study. Patients were allocated to either Sugammadex group (Group S) or the Neostigmine group (Group N). The primary outcome of the study was early postoperative cognitive recovery as measured by the Montreal Cognitive Assessment (MoCA) and Mini Mental State Examination (MMSE). After baseline assessment 12-24h before the operation. After the operation, when the Modified Aldrete Recovery Score was ≥9 the MMSE and 1h later the MoCA tests were repeated.

RESULTS

Although there was a reduction in MoCA and MMSE scores in both Group S and Group N between preoperative and postoperative scores, there was no statistically significant difference in the slopes (p>0.05). The time to reach TOF 0.9 was 2.19min in Group S and 6.47min in Group N (p<0.0001). Recovery time was 8.26min in Group S and 16.93min in Group N (p<0.0001).

CONCLUSION

We showed that the surgical procedure and/or accompanying anesthetic procedure may cause a temporary or permanent regression in cognitive function in the early postoperative period. However, better cognitive performance could not be proved in the Sugammadex compared to the Neostigmine.

Neuroprotective Effects Against POCD by Photobiomodulation: Evidence from Assembly/Disassembly of the Cytoskeleton

Postoperative cognitive dysfunction (POCD) is a decline in memory following anaesthesia and surgery in elderly patients. While often reversible, it consumes medical resources, compromises patient well-being, and possibly accelerates progression into Alzheimer's disease. Anesthetics have been implicated in POCD, as has neuroinflammation, as indicated by cytokine inflammatory markers. Photobiomodulation (PBM) is an effective treatment for a number of conditions, including inflammation. PBM also has a direct effect on microtubule disassembly in neurons with the formation of small, reversible varicosities, which cause neural blockade and alleviation of pain symptoms. This mimics endogenously formed varicosities that are neuroprotective against damage, toxins, and the formation of larger, destructive varicosities and focal swellings. It is proposed that PBM may be effective as a preconditioning treatment against POCD; similar to the PBM treatment, protective and abscopal effects that have been demonstrated in experimental models of macular degeneration, neurological, and cardiac conditions.

The impact of health literacy in the care of surgical patients: a qualitative systematic review

BACKGROUND

Inadequate health literacy affects more than 90 million Americans and it has been associated with adverse outcomes in the medicine field including increased hospitalization rates and greater mortality. Since surgical patients are often required to make complex decisions and adhere to complex instructions, health literacy may have a profound impact in the surgical practice. The main objective of the current study was to systematically evaluate the role of health literacy in surgical patients.

METHODS

A systematic search was performed to identify studies that evaluated the role of health literacy in the perioperative setting following the PRISMA guidelines. Only studies that examined health literacy using a validated instrument in the perioperative setting were included.

RESULTS

Ten studies including data on 1147 patients were included. The median (IQR) number of patients in the included studies was 101 (30 to 152). The majority of studies used the Short Test of Functional Literacy in adults (STOFHLA) to evaluate patients' health literacy. Five studies evaluated the patients preoperatively, four studies evaluated patients in the postoperative period and in one study the time of evaluation in relation to the surgical procedure was not defined. The lowest prevalence of inadequate health literacy was detected in kidney transplant patients, 6 out of 124 (5 %), while the highest prevalence of inadequate health literacy was detected in orthopedic patients having total joint replacement, 86 out of 126 (60 %). Inadequate health literacy in the preoperative period was associated with poor medical information comprehension and it may adversely affect adherence to preoperative medications and even modulate surgical disparities. Inadequate health literacy in the postoperative period was associated with poor comprehension of discharge instructions and worse kidney function in transplant recipients.

CONCLUSIONS

Health literacy seems to have a very significant impact in the care of surgical patients. More studies to establish the impact of poor health literacy on perioperative outcomes are needed.

Postoperative Cognitive Dysfunction: Minding the Gaps in Our Knowledge of a Common Postoperative Complication in the Elderly

Postoperative cognitive dysfunction (POCD) is a common complication associated with significant morbidity and mortality in elderly patients. There is much interest in and controversy about POCD, reflected partly in the increasing number of articles published on POCD recently. Recent work suggests surgery may also be associated with cognitive improvement in some patients, termed postoperative cognitive improvement (POCI). As the number of surgeries performed worldwide approaches 250 million per year, optimizing postoperative cognitive function and preventing/treating POCD are major public health issues. In this article, we review the literature on POCD and POCI, and discuss current research challenges in this area.