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

Long-term cognitive outcome after elective hip or knee total joint arthroplasty: A population-based observational study

BACKGROUND

One year after elective hip or knee total joint arthroplasty (TJA), >30% of older adults meet criteria for postoperative neurocognitive disorder. However, this is not contextualized with long-term cognitive outcomes in comparable surgical and nonsurgical controls. We analyzed population-based data to compare long-term cognitive outcomes in older adults after TJA, other surgeries, and with and without arthritis pain.

METHODS

This was a retrospective observational analysis of United States older adults in the Health and Retirement Study (HRS) who underwent elective TJA, or elective surgery without expected functional benefits (e.g., cholecystectomy; inguinal herniorrhaphy), between 1998 and 2018 at aged 65 or older. TJA recipients were also age- and sex-matched to nonsurgical controls who reported moderate-severe arthritic pain or denied pain, so that comparison groups included surgical and nonsurgical (pain-suffering and pain-free) controls. We modeled biennially-assessed memory performance, a measure of direct and proxy cognitive assessments, before and after surgery, normalized to the rate of memory decline ("cognitive aging") in controls to express effect size estimates as excess, or fewer, months of memory decline. We used linear mixed effects models adjusted for preoperative health and demographic factors, including frailty, flexibly capturing time before/after surgery (knots at -4, 0, 8 years; discontinuity at surgery).

RESULTS

There were 1947 TJA recipients (average age 74; 63% women; 1358 knee, 589 hip) and 1631 surgical controls (average age 76; 38% women). Memory decline 3 years after TJA was similar to surgical controls (5.2 [95% confidence interval, CI -1.2 to 11.5] months less memory decline in the TJA group, p = 0.11) and nonsurgical controls. At 5 years, TJA recipients experienced 5.0 [95% CI -0.9 to 10.9] months less memory decline than arthritic pain nonsurgical controls.

CONCLUSION

There is no systematic accelerated memory decline at 3 years after TJA compared with surgical or nonsurgical controls.

Cognitive and Cerebrospinal Fluid Alzheimer's Disease-related Biomarker Trajectories in Older Surgical Patients and Matched Nonsurgical Controls

BACKGROUND

Anesthesia and/or surgery accelerate Alzheimer's disease pathology and cause memory deficits in animal models, yet there is a lack of prospective data comparing cerebrospinal fluid (CSF) Alzheimer's disease-related biomarker and cognitive trajectories in older adults who underwent surgery versus those who have not. Thus, the objective here was to better understand whether anesthesia and/or surgery contribute to cognitive decline or an acceleration of Alzheimer's disease-related pathology in older adults.

METHODS

The authors enrolled 140 patients 60 yr or older undergoing major nonneurologic surgery and 51 nonsurgical controls via strata-based matching on age, sex, and years of education. CSF amyloid β (Aβ) 42, tau, and p-tau-181p levels and cognitive function were measured before and after surgery, and at the same time intervals in controls.

RESULTS

The groups were well matched on 25 of 31 baseline characteristics. There was no effect of group or interaction of group by time for baseline to 24-hr or 6-week postoperative changes in CSF Aβ, tau, or p-tau levels, or tau/Aβ or p-tau/Aβ ratios (Bonferroni P > 0.05 for all) and no difference between groups in these CSF markers at 1 yr (P > 0.05 for all). Nonsurgical controls did not differ from surgical patients in baseline cognition (mean difference, 0.19 [95% CI, -0.06 to 0.43]; P = 0.132), yet had greater cognitive decline than the surgical patients 1 yr later (β, -0.31 [95% CI, -0.45 to -0.17]; P < 0.001) even when controlling for baseline differences between groups. However, there was no difference between nonsurgical and surgical groups in 1-yr postoperative cognitive change in models that used imputation or inverse probability weighting for cognitive data to account for loss to follow up.

CONCLUSIONS

During a 1-yr time period, as compared to matched nonsurgical controls, the study found no evidence that older patients who underwent anesthesia and noncardiac, nonneurologic surgery had accelerated CSF Alzheimer's disease-related biomarker (tau, p-tau, and Aβ) changes or greater cognitive decline.

EDITOR’S PERSPECTIVE

Cognitive Training for Reduction of Delirium in Patients Undergoing Cardiac Surgery: A Randomized Clinical Trial

IMPORTANCE

Postoperative delirium is a common and impactful neuropsychiatric complication in patients undergoing coronary artery bypass grafting surgery. Cognitive training may enhance cognitive reserve, thereby reducing postoperative delirium.

OBJECTIVE

To determine whether preoperative cognitive training reduces the incidence of delirium in patients undergoing coronary artery bypass grafting.

DESIGN, SETTING, and PARTICIPANTS

This prospective, single-blind, randomized clinical trial was conducted at 3 university teaching hospitals in southeastern China with enrollment between April 2022 and May 2023. Eligible participants included those scheduled for elective coronary artery bypass grafting who consented and enrolled at least 10 days before surgery.

INTERVENTIONS

Participating patients were randomly assigned 1:1, stratified by site, to either routine care or cognitive training, which included substantial practice with online tasks designed to enhance cognitive functions including memory, imagination, reasoning, reaction time, attention, and processing speed.

MAIN OUTCOMES AND MEASURES

The primary outcome was occurrence of delirium during postoperative days 1 to 7 or until hospital discharge, diagnosed using the Confusion Assessment Method or the Confusion Assessment Method for Intensive Care Units. Secondary outcomes were postoperative cognitive dysfunction, delirium characteristics, and all-cause mortality within 30 days following the operation.

RESULTS

A total of 218 patients were randomized and 208 (median [IQR] age, 66 [58-70] years; 64 female [30.8%] and 144 male [69.2%]) were included in final analysis, with 102 randomized to cognitive training and 106 randomized to routine care. Of all participants, 95 (45.7%) had only a primary school education and 54 (26.0%) had finished high school. In the cognitive training group, 28 participants (27.5%) developed delirium compared with 46 participants (43.4%) randomized to routine care. Those receiving cognitive training were 57% less likely to develop delirium compared with those receiving routine care (adjusted odds ratio [aOR] 0.43; 95% CI, 0.23-0.77; P = .007). Significant differences were observed in the incidence of severe delirium (aOR, 0.46; 95% CI, 0.25-0.82; P = .01), median (IQR) duration of delirium (0 [0-1] days for cognitive training vs 0 [0-2] days for routine care; P = .008), and median (IQR) number of delirium-positive days (0 [0-1] days for cognitive training vs 0 [0-2] days for routine care; P = .007). No other secondary outcomes differed significantly.

CONCLUSIONS AND RELEVANCE

In this randomized trial of 208 patients undergoing coronary artery bypass grafting, preoperative cognitive training reduced the incidence of postoperative delirium. However, our primary analysis was based on fewer than 75 events and should therefore be considered exploratory and a basis for future larger trials.

Trial Registration

Chinese Clinical Trial Registry Identifier: ChiCTR2200058243.

Knowledge, attitudes, and practice toward postoperative cognitive dysfunction among anesthesiologists in China: a cross-sectional study

BACKGROUND

To investigate the knowledge, attitudes, and practice (KAP) toward postoperative cognitive dysfunction (POCD) among anesthesiologists in China.

METHODS

This cross-sectional study was conducted nationwide among Chinese anesthesiologists between December 2022 and January 2023. The demographic information and KAP scores of the respondents were collected using a web-based questionnaire. The mean KAP dimension scores ≥ 60% were considered good.

RESULTS

This study enrolled 1032 anesthesiologists (51.2% male). The mean total scores of knowledge, positive attitude, and positive practice were 9.3 ± 1.2 (max 12), 34.8 ± 3.3 (max 40), and 30.6 ± 6.7 (max 40), respectively. The knowledge items with correctness scores < 60% were "the anesthetic drugs that tend to cause POCD" (23.3%) and "Treatment of POCD" (40.3%). Multivariable analysis showed that ≥ 40 years old, master's degree or above, intermediate professional title (i.e., attending physician), senior professional title (i.e., chief physician), and working in tertiary hospitals were independently associated with adequate knowledge. Multivariable analysis showed that the attitude scores, middle professional title, and ≥ 16 years of experience were independently associated with good practice.

CONCLUSIONS

These results suggest that Chinese anesthesiologists have good knowledge, favorable attitudes, and good practice toward POCD. Still, some points remain to be improved (e.g., the drugs causing POCD and managing POCD) and should be emphasized in training and continuing education.

TRIAL REGISTRATION

ChiCTR2200066749.

The Association of Plasma Leptin, Soluble Leptin Receptor and Total and High-Molecular Weight Adiponectin With the Risk of Perioperative Neurocognitive Disorders

BACKGROUND

Perioperative neurocognitive disorders (NCD) are poorly characterized in terms of their risk factor profiles. Leptin and adiponectin are adipose-tissue-derived hormones with a role in inflammation and atherosclerosis whose function in perioperative NCD is unclear. Here, we used a cohort of older adults to examine the association of preoperative plasma concentrations of these biomarkers with the risk of perioperative NCD.

METHODS

Prospective analysis of 768 participants aged ≥ 65 years of the BioCog study. Blood was collected before surgery for measurement of plasma total and high-molecular-weight (hmw) adiponectin, leptin, and soluble leptin receptor (sOB-R). The free leptin index (FLI, leptin:sOB-R) was calculated. Postoperative delirium (POD) was assessed twice daily until postoperative day 7/discharge. Five hundred twenty-six patients (68.5%) returned for 3-month follow-up and provided data on postoperative cognitive dysfunction (POCD). POCD was defined as a decline on six neuropsychological tests that exceeded that of a nonsurgical control group. Logistic regression analyses examined the associations of each exposure with POD and POCD risk, in separate models adjusted for age, sex, fasting, surgery type, and body mass index (BMI).

RESULTS

Of 768 patients, 152 (19.8%) developed POD. Of 526 attendants of the follow-up, 54 (10.3%) had developed POCD. Leptin, sOB-R, and total and hmw adiponectin were each not associated with POD. For POCD, we observed reduced risk in patients in FLI quartile 4 compared with quartile 1 (odds ratio, 0.26; 95% CI 0.08, 0.89). Sensitivity analyses for the outcome POD revealed statistically significant interaction terms of sOB-R and total adiponectin with obesity (BMI≥30kg/m2 versus BMI<30kg/m2). For the outcome POCD, a higher sOB-R was associated with an increased risk in the obese subgroup (odds ratio, 4.00; 95% CI 1.01, 15.86).

CONCLUSIONS

We did not find consistent evidence for the role of leptin, its receptor, and total and hmw adiponectin in POD and POCD risk. Future research should be used to support or refute our findings and to fully characterize any differences in the associations of these hormones with POD/POCD between obese and nonobese individuals.

Dietary Restriction Improves Perioperative Neurocognitive Disorders by Inhibiting Neuroinflammation and Gut Microbial Dysbiosis

Anesthesia/surgery have been identified as potential factors contributing to perioperative neurocognitive disorders, with a notably heightened risk observed in aging populations. One of the primary drivers of this impairment is believed to be neuroinflammation, specifically inflammation of hippocampal microglia. Dietary restriction has demonstrated a favorable impact on cognitive impairment across various disorders, primarily by quelling neuroinflammation. However, the precise influence of dietary restriction on perioperative neurocognitive disorders remains to be definitively ascertained. This investigation aims to explore the effects of dietary restriction on perioperative neurocognitive disorders and propose innovative therapeutic strategies for their management. The model of perioperative neurocognitive disorder was induced through exploratory laparotomy under isoflurane anesthesia. Cognitive performance was evaluated using the open field test, Barnes maze test, and fear conditioning test. The enzyme-linked immunosorbent assay (ELISA) was employed to quantify concentrations of interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α) in both serum and hippocampal samples. The Western blot technique was utilized to assess expression levels of hippocampal PSD 95, Synaptophysin, TLR4, MyD88, and NF-kB p65. Microglial polarization was gauged using a combination of reverse transcription quantitative polymerase chain reaction (RT-qPCR) and immunofluorescence labeling techniques. We conducted 16S rRNA sequencing to investigate the impact of dietary restriction on the intestinal flora of aged mice following anesthesia/surgery. Our findings indicate that dietary restrictions have the potential to ameliorate anesthesia/surgery-induced cognitive dysfunction. This effect is achieved through the modulation of gut microbiota, suppression of inflammatory responses in hippocampal microglia, and facilitation of neuronal repair and regeneration.

Influence of Neostigmine on Early Postoperative Cognitive Dysfunction in Older Adult Patients Undergoing Noncardiac Surgery: A Double-Blind, Placebo-Controlled, Randomized Controlled Trial

BACKGROUND

The goal of this study was to investigate the efficacy of neostigmine on postoperative cognitive dysfunction (POCD) and determine its effect on systematic markers of oxidative stress in older patients.

METHODS

This double-blind placebo-controlled trial enrolled 118 elderly patients (≥65 years) undergoing noncardiac surgeries who were allocated to a neostigmine treatment group (0.04 mg/kg) or a placebo control group (normal saline) postoperatively. POCD was diagnosed if the Z -scores for the mini-mental state examination and the Montreal Cognitive Assessment were both ≤-1.96. Postoperative serum levels of malondialdehyde (MDA), superoxide dismutase (SOD), and brain-derived neurotrophic factor (BDNF) were also compared. Multivariable regression analysis with dose adjustment of atropine was used to demonstrate the influence of neostigmine on the incidence of POCD.

RESULTS

Patients receiving neostigmine had a significantly reduced incidence of POCD compared to patients who were treated with placebo on the first day after surgery (-22%, 95% confidence interval [CI], -37 to -7), but not on the third (8%, 95% CI, -4 to 20) or seventh day after surgery (3%, 95% CI, -7 to 13). Postoperative plasma MDA levels were significantly lower ( P = .016), but SOD and BDNF levels were increased ( P = .036 and .013, respectively) in the neostigmine group compared to the control group on the first day after surgery.

CONCLUSIONS

Neostigmine reduced POCD on the first day after noncardiac surgery in older patients. Neostigmine treatment inhibited oxidative stress and increased serum BDNF levels. There was no significant influence of neostigmine on POCD on the third or seventh day after surgery. The clinical influence of neostigmine on POCD should be further investigated.

Long-term cognitive outcomes after surgery and anesthesia: what we find depends on where we look

Purpose of review

To review how anecdote and narrative medicine, primary cohort studies, epidemiological studies, and the dementia literature can be bridged to understand long-term postoperative cognitive decline.

Recent findings

Primary cohort studies have measured recoverable declines in memory and executive function after major surgery, but less-appreciated sources also offer critical insights. Anecdote reveals that functionally-impactful cognitive decline may persist after physical recovery in some patients despite modern medications and monitoring, and that physicians are unprepared to address patients' cognitive concerns. However, epidemiological studies reproducibly demonstrate that elective surgery has no, or a negligible, average impact on cognition in older patients. Cognitively provocative factors - like medical hospital admissions or health factors like diabetes and smoking - are common in late life, and surgery likely contributes minimally to long-term cognitive change for most patients.

Summary

Patients should be reassured that, while anecdotes of durable cognitive change after surgery are easily accessible, most patients experience cognitive recovery after major surgery. However, those who do not recover deserve characterization of their symptoms and investigation of modifiable causes to facilitate cognitive recovery.

Research progress on the association between MicroRNA and postoperative cognitive dysfunction

Postoperative cognitive dysfunction (POCD) is a significant complication following surgery. The precise mechanisms underlying POCD remain elusive, although it is speculated that they involve central nervous system inflammation, oxidative stress and cellular apoptosis. MicroRNAs (miRNAs), a class of non-coding RNAs widely distributed in eukaryotes, have been implicated in the pathogenesis of neurodegenerative disorders and could potentially impact POCD. This review explores the association between miRNAs and POCD and provides an overview of the progress of current research on miRNAs in the pathogenesis, diagnosis, and treatment of POCD.

Sevoflurane anesthesia reduces the expression of inflammatory response genes and β-site amyloid precursor protein-cleaving enzyme in hippocampi of diabetic mice

Diabetes and inhaled anesthesia are associated with an increased likelihood of developing postoperative cognitive dysfunction in humans and animal models, but the mechanisms are unclear. This study aimed to investigate the effect and mechanism of sevoflurane anesthesia on cognitive function in diabetic (DM) mice. Spontaneously diabetic db/db and control db/m mice were subject to sevoflurane anesthesia or allowed to breathe air, respectively. The Morris water maze test as spatial learning and novel object recognition test as recognition memory were performed. The expression of inflammatory cytokines and neurotoxicity-related genes in the hippocampus of four groups was measured using real-time PCR. The expression level of neurotoxicity and neuroprotection-related proteins in DM mice hippocampus were estimated using Western blot assay. It is found that DM mice developed cognitive impairment; however, the cognitive impairment was not exacerbated in sevoflurane-exposed mice. Sevoflurane anesthesia led to a decrease in mRNA levels of inflammatory cytokines in DM mice hippocampi, including interleukin 17 (IL-17), C-C motif chemokine (CCL20), CCL7 as well as high mobility group box 1 and beta-site amyloid-β cleaving enzyme 1; and no effect was observed on the expression of neurotoxicity genes, including amyloid precursor protein, choline O-acetyltransferase, tumor necrosis factor, alpha-induced protein 1, B-cell lymphoma 2 and estrogen receptor 2. In addition, we observed elevated phosphorylation of cAMP response element-binding protein in DM mice exposed to sevoflurane anesthesia. In conclusion, sevoflurane did not exacerbate DM-associated cognitive impairment.

Electroacupuncture pretreatment preserves telomerase reverse transcriptase function and alleviates postoperative cognitive dysfunction by suppressing oxidative stress and neuroinflammation in aged mice

BACKGROUND

Elderly patients often exhibit postoperative cognitive dysfunction (POCD), a postsurgical decline in memory and executive function. Oxidative stress and neuroinflammation, both pathological characteristics of the aged brain, contribute to this decline. This study posits that electroacupuncture (EA) stimulation, an effective antioxidant and anti-inflammatory modality, may enhance telomerase reverse transcriptase (TERT) function, the catalytic subunit of telomerase known for its protective properties against cellular senescence and oxidative damage, to alleviate POCD in aged mice.

METHODS

The animal POCD model was created by subjecting aged mice to abdominal surgery, followed by EA pretreatment at the Baihui acupoint (GV20). Postoperative cognitive function was gauged using the Morris water maze (MWM) test. Hippocampal TERT mRNA levels and telomerase activity were determined through qPCR and a Telomerase PCR ELISA kit, respectively. Oxidative stress was assessed through superoxide dismutase (SOD), reactive oxygen species (ROS), and malondialdehyde (MDA) levels. Iba-1 immunostaining determined the quantity of hippocampal microglia. Additionally, western blotting assessed TERT, autophagy markers, and proinflammatory cytokines at the protein level.

RESULTS

Abdominal surgery in aged mice significantly decreased telomerase activity and TERT mRNA and protein levels, but increased oxidative stress and neuroinflammation and decreased autophagy in the hippocampus. EA-pretreated mice demonstrated improved postoperative cognitive performance, enhanced telomerase activity, increased TERT protein expression, improved TERT mitochondrial localization, and reduced oxidative damage, autophagy dysfunction, and neuroinflammation. The neuroprotective benefits of EA pretreatment were diminished following TERT knockdown.

CONCLUSIONS

Our findings underscore the significance of TERT function preservation in alleviating surgery-induced oxidative stress and neuroinflammation in aged mice. A novel neuroprotective mechanism of EA stimulation is highlighted, whereby modulation of TERT and telomerase activity reduces oxidative damage and neuroinflammation. Consequently, maintaining TERT function via EA treatment could serve as an effective strategy for managing POCD in elderly patients.

Anesthesia/surgery-induced learning and memory dysfunction by inhibiting mitophagy-mediated NLRP3 inflammasome inactivation in aged mice

Postoperative cognitive dysfunction (POCD) is a common postoperative complication, not only affects the quality of life of the elderly and increases the mortality rate, but also brings a greater burden to the family and society. Previous studies demonstrated that Nod-like receptor protein 3 (NLRP3) inflammasome participates in various inflammatory and neurodegenerative diseases. However, possible mitophagy mechanism in anesthesia/surgery-elicited NLRP3 inflammasome activation remains to be elucidated. Hence, this study clarified whether mitophagy dysfunction is related to anesthesia/surgery-elicited NLRP3 inflammasome activation. POCD model was established in aged C57BL/6 J mice by tibial fracture fixation under isoflurane anesthesia. Morris Water Maze (MWM) was used to evaluate learning and memory abilities. We found that in vitro experiments, lipopolysaccharide (LPS) significantly facilitated NLRP3 inflammasome activation and mitophagy inhibition in BV2 cells. Rapamycin restored mitophagy and improved mitochondrial function, and inhibited NLRP3 inflammasome activation induced by LPS. In vivo experiments, anesthesia and surgery caused upregulation of hippocampal NLRP3, caspase recruitment domain (ASC) and interleukin-1β (IL-1 β), and downregulation of microtubule-associated protein light chain 3II (LC3II) and Beclin1 in aged mice. Olaparib inhibited anesthesia/surgery-induced NLRP3, ASC, and IL-1β over-expression in the hippocampus, while upregulated the expression of LC3II and Beclin1. Furthermore, Olaparib improved cognitive impairment in older mice. These results revealed that mitophagy was involved in NLRP3 inflammasome-mediated anesthesia/surgery-induced cognitive deficits in aged mice. Overall, our results suggested that mitophagy was related in NLRP3 inflammasome-induced cognitive deficits after anesthesia and surgery in aged mice. Activating mitophagy may have clinical benefits in the prevention of cognitive impairment induced by anesthesia and surgery in elderly patients.

Genetic Ablation of Dentate Hilar Somatostatin-Positive GABAergic Interneurons is Sufficient to Induce Cognitive Impairment

Aging is often associated with a decline in cognitive function. A reduction in the number of somatostatin-positive (SOM+) interneurons in the dentate gyrus (DG) has been described in cognitively impaired but not in unimpaired aged rodents. However, it remains unclear whether the reduction in SOM + interneurons in the DG hilus is causal for age-related cognitive dysfunction. We hypothesized that hilar SOM+ interneurons play an essential role in maintaining cognitive function and that a reduction in the number of hilar SOM + interneurons might be sufficient to induce cognitive dysfunction. Hilar SOM+ interneurons were ablated by expressing a diphtheria toxin transgene specifically in these interneurons, which resulted in a reduction in the number of SOM+ /GAD-67+ neurons and dendritic spine density in the DG. C-fos and Iba-1 immunostainings were increased in DG and CA3, but not CA1, and BDNF protein expression in the hippocampus was decreased. Behavioral testing showed a reduced recognition index in the novel object recognition test, decreased alternations in the Y maze test, and longer latencies and path lengths in the learning and reversal learning phases of the Morris water maze. Our results show that partial genetic ablation of SOM+ hilar interneurons is sufficient to increase activity in DG and CA3, as has been described to occur with aging and to induce an impairment of learning and memory functions. Thus, partial ablation of hilar SOM + interneurons may be a significant contributing factor to age-related cognitive dysfunction. These mice may also be useful as a cellularly defined model of hippocampal aging.

Perioperative neurocognitive disorder changes in elderly diabetes patients within 30 days after surgery: a retrospective cohort study

BACKGROUND

Perioperative neurocognitive disorders (PND) are a common central nervous system complication that predominantly affects the elderly. PND after surgery includes postoperative delirium (POD), delayed neurocognitive recovery up to 30 days (DNR), and postoperative neurocognitive disorder up to 12 months. Diabetes is an important independent risk factor for PND. Over the years, few studies have assessed the incidence of PND and the difference in serum biomarkers between diabetic and non-diabetic patients. We sought to examine the difference in the incidence of PND between elderly diabetic and non-diabetic patients in China and identify the risk factors of PND in elderly diabetics.

METHODS

We conducted a secondary and exploratory data analysis from our prior studies, including patients aged 65 years or older who underwent non-cardiac elective surgery with general anesthesia. We used the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU) and Montreal Cognitive Assessment (MoCA) to assess patient cognition.

RESULTS

A total of 236 patients were analyzed; the incidence of PND was significantly higher in diabetic than in non-diabetic patients within 30 days (59.2% vs. 36.8%) (P = 0.022). Multivariate logistic regression analysis showed that the preoperative MoCA was an independent risk factor for PND (odds ratio, 0.88 [0.8 to 0.97]; P = 0.014), and Hosmer-Lemeshow tests showed that it could predict PND in diabetic patients (P = 0.360). According to the maximum Youden index, the optimal cutoff for preoperative MoCA was 21.5 points, yielding a specificity and sensitivity of 88.0% and 55.2% for PND. The levels of glial fibrillary acidic protein (GFAP) and Tau in diabetic patients before and after surgery were significantly higher than in non-diabetic patients among cases of PND (P = 0.002 and 0.011, respectively).

CONCLUSION

The incidence of PND is higher in diabetic than in non-diabetic patients in China, and preoperative MoCA is an independent risk factor for PND in diabetics. Meanwhile, the changes in GFAP and p-Tau in diabetic patients who experienced PND were significantly higher than in non-diabetic ones.

Effects of xenon anesthesia on postoperative neurocognitive disorders: a systematic review and meta-analysis

The latest clinical trials have reported conflicting outcomes regarding the effectiveness of xenon anesthesia in preventing postoperative neurocognitive dysfunction; thus, this study assessed the existing evidence. We searched the PubMed, Embase, Cochrane Library, and Web of Science databases from inception to April 9, 2023, for randomized controlled trials of xenon anesthesia in postoperative patients. We included English-language randomized controlled studies of adult patients undergoing surgery with xenon anesthesia that compared its effects to those of other anesthetics. Duplicate studies, pediatric studies, and ongoing clinical trials were excluded. Nine studies with 754 participants were identified. A forest plot revealed that the incidence of postoperative neurocognitive dysfunction did not differ between the xenon anesthesia and control groups (P = 0.43). Additionally, xenon anesthesia significantly shortened the emergence time for time to opening eyes (P < 0.001), time to extubation (P < 0.001), time to react on demand (P = 0.01), and time to time and spatial orientation (P = 0.04). However, the Aldrete score significantly increased with xenon anesthesia (P = 0.005). Postoperative complications did not differ between the anesthesia groups. Egger's test for bias showed no small-study effect, and a trim-and-fill analysis showed no apparent publication bias. In conclusion, xenon anesthesia probably did not affect the occurrence of postoperative neurocognitive dysfunction. However, xenon anesthesia may effectively shorten the emergence time of certain parameters without adverse effects.

Physical activity compensates for isoflurane-induced selective impairment of neuronal progenitor cell proliferation in the young adult hippocampus

General anesthesia is considered a risk factor for postoperative cognitive dysfunction. However, it is unclear what the neuronal and cognitive consequences of general anesthesia are and whether they can be treated. One possible pathomechanism is hippocampal neurogenesis. We investigated how the anesthetic isoflurane affects adult hippocampal neurogenesis and associated cognitive functions and whether the neurogenic stimulus of physical activity reverses isoflurane-induced changes. We exposed young adult mice to isoflurane (ISO) - half had access to a running wheel (ISO-RW). Both groups were compared with a control condition (CTR; CTR-RW). Cell proliferation and survival in the dentate gyrus of the hippocampus were quantified histologically 48 h and 3 weeks after anesthesia by bromodeoxyuridine incorporation. Cell phenotype was determined by expression of neuronal markers, and the extent of continuous endogenous neuronal proliferation was estimated from the number of doublecortin-positive cells. The Morris water maze was used to test hippocampus-dependent functions. We found that isoflurane decreased proliferation of neuronal progenitor cells, whereas survival of mature neurons remained intact. Consistent with intact neuronal survival, spatial memory associated with neurogenesis also proved intact in the Morris water maze despite isoflurane exposure. Physical activity attenuated the observed neuronal changes by preventing the decrease in newborn neuronal progenitor cells and the decline in continuous endogenous neuronal proliferation in isoflurane-treated animals. In conclusion, isoflurane selectively impairs neuronal proliferation but not survival or neurogenesis-linked cognition in adult mice. The observed adverse effects can be attenuated by physical activity, a cost-effective means of preventing the neurogenic consequences of general anesthesia.

ApoE Mimetic Peptides as Therapy for Traumatic Brain Injury

The lack of targeted therapies for traumatic brain injury (TBI) remains a compelling clinical unmet need. Although knowledge of the pathophysiologic cascades involved in TBI has expanded rapidly, the development of novel pharmacological therapies has remained largely stagnant. Difficulties in creating animal models that recapitulate the different facets of clinical TBI pathology and flaws in the design of clinical trials have contributed to the ongoing failures in neuroprotective drug development. Furthermore, multiple pathophysiological mechanisms initiated early after TBI that progress in the subacute and chronic setting may limit the potential of traditional approaches that target a specific cellular pathway for acute therapeutic intervention. We describe a reverse translational approach that focuses on translating endogenous mechanisms known to influence outcomes after TBI to develop druggable targets. In particular, numerous clinical observations have demonstrated an association between apolipoprotein E (apoE) polymorphism and functional recovery after brain injury. ApoE has been shown to mitigate the response to acute brain injury by exerting immunomodulatory properties that reduce secondary tissue injury as well as protecting neurons from excitotoxicity. CN-105 represents an apoE mimetic peptide that can effectively penetrate the CNS compartment and retains the neuroprotective properties of the intact protein.

The elderly in the post-anesthesia care unit

It is increasingly conceivable that elderly patients will be treated in perioperative settings as the world's population shifts toward an older age distribution. They are more prone to a variety of unfavorable outcomes as a consequence of the physiological changes that accompany aging and the coexistence of multiple medical conditions. Postoperative complications in elderly patients are linked to a large increase in morbidity and mortality and the burden placed on the healthcare system. Our goal is to determine how elderly patients' recovery after anesthesia differs from that of younger patients. In addition, we will discuss the main postoperative complications experienced by elderly patients and the measures that are utilized to limit the risk of these complications developing.

Effectiveness of cognitive interventions for adult surgical patients after general anaesthesia to improve cognitive functioning: A systematic review

AIMS AND OBJECTIVES

To examine the effectiveness of cognitive interventions after general anaesthesia to improve cognitive functioning.

BACKGROUND

The number of surgical procedures performed worldwide is large and growing. Postoperative cognitive dysfunction is a common complication associated with poor postoperative outcomes. A variety of cognitive interventions have been developed to maintain or improve cognitive function in one or more cognitive domains. Cognitive interventions have shown to be effective in healthy older populations, those with mild cognitive impairment, and those with heart failure. The impact of cognitive interventions in surgical patients after general anaesthesia is a relatively new focus of research and is therefore less well established.

METHODS

Seven bibliographic databases were searched in relation to 'surgery' and 'cognitive interventions'; no date or language limits were imposed. Studies including adult patients who were scheduled for, or who had undergone surgery under general anaesthesia, had a baseline cognitive assessment using a validated measurement, and had engaged with any cognition-based intervention were included. Full-text review for inclusion, quality assessment and data extraction were undertaken independently by two authors. This study is reported in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines.

RESULTS

A total of 550 papers were identified for possible inclusion, of which nine met the inclusion criteria and were included in the review. The majority were randomised controlled trials (RCTs) (n = 6 [66.7%]). Four studies used computerised cognitive interventions, while five used traditional cognitive interventions. Most of the studies used multi-domain cognitive training focusing on two or more domains (n = 7 [77.8%]) while two studies used single-domain cognitive training. Memory (n = 7 [77.8%]) and attention (n = 5 [55.6%]) were the cognitive domains most often targeted during the intervention.

CONCLUSIONS

The use of cognitive interventions demonstrated some efficacy in improving cognitive function after general anaesthesia, particularly those targeting memory.

RELEVANCE FOR CLINICAL PRACTICE

The findings of this review suggest that cognitive interventions show promise at improving cognitive performance in patients with POCD and could be usefully implemented in clinical practice to improve patient outcomes.

The Effect of Anaesthesia Management with Different Fresh Gas Flows on Cognitive Functions of Geriatric Patients: A Randomized Double-blind Study

Objective

The present study aimed to compare the effects of two different fresh gas flows (FGFs) (0.5 L min^-1 and 2 L min^-1) applied during maintenance of anaesthesia on recovery from anaesthesia and early cognitive functions in geriatric patients.

Methods

In this prospective, randomised, double-blind study, sixty patients were divided into two groups according to the amount of FGF. Minimal-flow anaesthesia (0.5 L min^-1 FGF) was applied to group I and medium-flow anaesthesia (2 L min^-1 FGF) was applied to group II during maintenance of anaesthesia. Following the termination of inhalation anaesthesia, recovery times were recorded. The evaluation of cognitive functions was performed using the Addenbrooke's Cognitive Examination (ACE-R).

Results

There was no significant difference between the two groups in terms of demographic characteristics and recovery (P > 0.05). There was no significant difference between the two groups in terms of the preoperative day, the first postoperative day, and the third postoperative day; ACE-R scores (P > 0.05). In group II, on the third postoperative day ACE-R scores were found to be significantly lower than the preoperative ACE-R scores (P=0.04). In group II, third postoperative day ACE-R memory sub-scores (14.53 ± 3.34) were found to be significantly lower than preoperative ACE-R memory sub-scores (15.03 ± 3.57) (P=0.04).

Conclusion

In geriatric patients, minimal-flow anaesthesia was not superior to medium-flow anaesthesia in terms of recovery properties and cognitive functions. Keeping in mind that hypoxaemia and changes in anaesthesia levels may occur with the reduction of FGF, both minimal- and medium-flow anaesthesia can be applied with appropriate monitoring without adverse effects on recovery and cognitive functions.

Sevoflurane and desflurane effects on early cognitive function after low-risk surgery: A randomized clinical trial

BACKGROUND AND OBJECTIVES

Deleterious effects on short-term and long-term quality of life have been associated with the development of postoperative cognitive dysfunction (POCD) after general anesthesia. Yet, the progress in the field is still required. Most of the studies investigate POCD after major surgery, so scarce evidence exists about the incidence and effect different anesthetics have on POCD development after minor procedures. In this study, we compared early postoperative cognitive function of the sevoflurane and desflurane patients who experienced a low-risk surgery of thyroid gland.

MATERIALS AND METHODS

Eighty-two patients, 40 years and over, with no previous severe cognitive, neurological, or psychiatric disorders, appointed for thyroid surgery under general anesthesia, were included in the study. In a random manner, the patients were allocated to either sevoflurane or desflurane study arms. Cognitive tests assessing memory, attention, and logical reasoning were performed twice: the day before the surgery and 24 h after the procedure. Primary outcome, magnitude of change in cognitive testing, results from baseline. POCD was diagnosed if postoperative score decreased by at least 20%.

RESULTS

Median change from baseline cognitive results did not differ between the sevoflurane and desflurane groups (-2.63%, IQR 19.3 vs. 1.13%, IQR 11.0; p = .222). POCD was detected in one patient (1.22%) of the sevoflurane group. Age, duration of anesthesia, postoperative pain, or patient satisfaction did not correlate with test scores. Intraoperative temperature negatively correlated with total postoperative score (r = -0.35, p = .007).

CONCLUSIONS

Both volatile agents proved to be equivalent in terms of the early cognitive functioning after low-risk thyroid surgery. Intraoperative body temperature may influence postoperative cognitive performance.

Stellate ganglion block alleviates postoperative cognitive dysfunction via inhibiting TLR4/NF-κB signaling pathway

Postoperative cognitive dysfunction (POCD) is common in aged patients after major surgery and is associated with increased risk of long-term morbidity and mortality. However, the underlying mechanism remains largely unknown and the clinical management of POCD is still controversial. Stellate ganglion block (SGB) is a clinical treatment for nerve injuries and circulatory issues. Recent evidence has identified the benefits of SGB in promoting learning and memory. We thus hypothesize that SGB could be effective in improving cognitive function after surgery. In present study, we established POCD model in aged rats via partial liver resection surgery. We found that the development of POCD was associated with the activation of toll-like receptor 4/nuclear factor kapa-B (TLR4/NF-κB) signaling pathway in the microglia in dorsal hippocampus, which induced the production of pro-inflammatory mediators (TNF-α, IL-1β, IL-6) and promoted neuroinflammation. More importantly, we showed evidence that preoperative treatment with SGB could inhibit microglial activation, suppress TLR4/NF-κB-mediated neuroinflammation and effectively attenuate cognitive decline after the surgery. Our study suggested that SGB may serve as a novel treatment to prevent POCD in elderly patients. As SGB is safe procedure widely used in clinic, our findings can be easily translated into clinical practice and benefit more patients.

Different Alterations of Hippocampal and Reticulo-Thalamic GABAergic Parvalbumin-Expressing Interneurons Underlie Different States of Unconsciousness

We traced the changes in GABAergic parvalbumin (PV)-expressing interneurons of the hippocampus and reticulo-thalamic nucleus (RT) as possible underlying mechanisms of the different local cortical and hippocampal electroencephalographic (EEG) microstructures during the non-rapid-eye movement (NREM) sleep compared with anesthesia-induced unconsciousness by two anesthetics with different main mechanisms of action (ketamine/diazepam versus propofol). After 3 h of recording their sleep, the rats were divided into two experimental groups: one half received ketamine/diazepam anesthesia and the other half received propofol anesthesia. We simultaneously recorded the EEG of the motor cortex and hippocampus during sleep and during 1 h of surgical anesthesia. We performed immunohistochemistry and analyzed the PV and postsynaptic density protein 95 (PSD-95) expression. PV suppression in the hippocampus and at RT underlies the global theta amplitude attenuation and hippocampal gamma augmentation that is a unique feature of ketamine-induced versus propofol-induced unconsciousness and NREM sleep. While PV suppression resulted in an increase in hippocampal PSD-95 expression, there was no imbalance between inhibition and excitation during ketamine/diazepam anesthesia compared with propofol anesthesia in RT. This increased excitation could be a consequence of a lower GABA interneuronal activity and an additional mechanism underlying the unique local EEG microstructure in the hippocampus during ketamine/diazepam anesthesia.

Postoperative delayed neurocognitive recovery: Evaluation of its incidence and correlation with intraoperative cerebral desaturation - A prospective observational study

BACKGROUND

Delayed neurocognitive recovery (DNR) is commonly seen in patients in the postoperative period. Literature has shown that monitoring cerebral desaturation intraoperatively can predict the development of DNR in elderly patients undergoing surgery in prone position. This prospective observational study was conducted in patients of all ages, with the primary objective to determine the incidence of DNR and its correlation with cerebral oximetry. The secondary objectives were to determine if intraoperative cerebral desaturation influenced the neuropsychometric variables from preoperative to postoperative period.

METHODS

This study included 61 patients, aged > 18 years undergoing spinal surgery in prone position. An evening before surgery and at 48 h postoperatively, patients were subjected to neuropsychological examination; Hindi Mental State Examination, Colour Trail Test 1 (CTT 1), CTT 2, Auditory Verbal Learning (AVLT) tests conducted by principal investigator (PI). DNR was defined as a 20% change in any of the test scores from the baseline. rSO₂ was recorded bilaterally every 10 min throughout surgery by an independent person. Cerebral desaturation was defined as a 20% drop in rSO₂ from the control value.

RESULTS

The incidence of DNR was 24.6%. The duration of anesthesia and cerebral desaturation were found to be independently predictive of DNR, with each hour of anesthesia causing a two-fold increase in the chances of development DNR (P = 0.019) and presence of cerebral desaturation causing a 6-fold increase (P = 0.039). CTT 1 and CTT 2 tests had significantly larger increase in test scores in the postoperative period, in patients with cerebral desaturation.

CONCLUSION

Duration of anesthesia and cerebral desaturation were factors predictive of the development of DNR in patients undergoing spine surgery in prone position.

Spinal Dexamethasone Effect on Cognitive Disorders After Hip Surgery

Background

Proximal femoral fractures (PrFF) are one of the most common causes of emergency admission in the elderly population. The majority of patients have pre-existing conditions that get worsened by unplanned surgery.

Objective

Purpose of this article was to evaluate if a is single shot of dexamethasone with levobupivacaine administered intrathecally reduces postoperative pain and cognitive complications in patients with proximal femoral fractures.

Methods

The study was performed at a level II trauma center which is a part of a teaching hospital with a catchment population of around 300,000 patients, the first author's affiliation. Around 500 PrFF are performed yearly in the center. All participants gave oral and written informed consent before randomization.

Results

In total, 60 patients with a PrFF, ASA status 2 or 3 were randomized into two groups for spinal anaesthesia as DLSA study group (received 8 mg of dexamethasone and 12.5 mg of 0.5 % levobupivacaine) or LSA control group (received 12.5 mg of 0,5 % levobupivacaine). Postoperative cognitive disturbance was evaluated using simplified Confusion Assessment Method (CAM) scale, pain intensity was measured using Visual Analogue Scale (VAS) and blood samples for defining cortisol concentrations were taken before and after the surgical procedure. The primary outcomes were effects of intrathecal dexamethasone on plasma cortisol affecting cognitive disturbances. Secondary outcomes included pain scores and length of hospital stay. The DLSA group demonstrated a reduced incidence of postoperative cognitive dysfunction (POCD), p=0.043, longer analgesia duration, p<0.001, decreased cortisol levels and shorter hospitalization p=0.045. Intrathecal dexamethasone was the only significant predictor of postoperative delirium, OR 7.76, p=0.019.

Conclusion

Single shot intrathecal administration of dexamethasone with levobupivacaine used in anaesthesia for proximal femoral fractures reduces the stress response by decreasing plasma cortisol concentrations prolonging analgesia. Complications such as delirium and POCD occurred with significantly lower frequency allowing better postoperative rehabilitation and shortening the hospitalization.

Is hospitalization a risk factor for cognitive decline in older age adults?

OBJECTIVES

Many studies document cognitive decline following specific types of acute illness hospitalizations (AIH) such as surgery, critical care, or those complicated by delirium. However, cognitive decline may be a complication following all types of AIH. This systematic review will summarize longitudinal observational studies documenting cognitive changes following AIH in the majority admitted population and conduct meta-analysis (MA) to assess the quantitative effect of AIH on post-hospitalization cognitive decline (PHCD).

METHODS

We followed Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. Selection criteria were defined to identify studies of older age adults exposed to AIH with cognitive measures. 6566 titles were screened. 46 reports were reviewed qualitatively, of which seven contributed data to the MA. Risk of bias was assessed using the Newcastle-Ottawa Scale.

RESULTS

The qualitative review suggested increased cognitive decline following AIH, but several reports were particularly vulnerable to bias. Domain-specific outcomes following AIH included declines in memory and processing speed. Increasing age and the severity of illness were the most consistent risk factors for PHCD. PHCD was supported by MA of seven eligible studies with 41,453 participants (Cohen's d = -0.25, 95% CI [-0.02, -0.49] I² 35%).

CONCLUSIONS

There is preliminary evidence that AIH exposure accelerates or triggers cognitive decline in the elderly patient. PHCD reported in specific contexts could be subsets of a larger phenomenon and caused by overlapping mechanisms. Future research must clarify the trajectory, clinical significance, and etiology of PHCD: a priority in the face of an aging population with increasing rates of both cognitive impairment and hospitalization.

Effect of Preoperative Oral Carbohydrates on Insulin Resistance in Older Adults Who Underwent Total Hip or Knee Arthroplasty: A Prospective Randomized Trial

INTRODUCTION

Preoperative carbohydrate drinks are recommended to reduce fasting time before surgery. Older adults are at risk of pulmonary aspiration and hyperglycemia after consuming carbohydrate drinks because of increased insulin resistance and delayed gastric emptying. We investigated the effects of oral carbohydrate drinks on perioperative insulin resistance, metabolic responses, and gastric volume in older adults.

METHODS

Fifty-six patients (aged more than 65 years) were randomly assigned to the control or carbohydrate (CHO) group. The CHO group received 400 mL of a carbohydrate drink 2 to 3 hours before anesthesia. The control group was allowed clear fluid intake 2 hours before anesthesia. Blood glucose and insulin levels were measured before intake of the carbohydrate drink and 1 hour postoperatively. Gastric volume was measured before spinal anesthesia. Insulin resistance was calculated using the homeostasis model assessment for insulin resistance.

RESULTS

Homeostasis model assessment for insulin resistance was not different between the control and CHO groups preoperatively (2.5 versus 3.3, P = 0.156) or postoperatively (2.6 versus 2.4, P = 0.817). Preoperative gastric volume was comparable between the control and CHO groups (35.5 versus 30.8 mL, P = 0.696).

DISCUSSION

Preoperative oral consumption of carbohydrates did not affect insulin resistance or gastric volume in older adults undergoing total knee or hip arthroplasty. Preoperative carbohydrate loading is safe in older adults undergoing total knee or hip arthroplasty.

DATA AVAILABILITY

The data that support the findings of this study are available from the corresponding author on reasonable request.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov (No. NCT04206189).

The potential link between obstructive sleep apnea and postoperative neurocognitive disorders: current knowledge and possible mechanisms

PURPOSE

This narrative review examines the current evidence on whether obstructive sleep apnea (OSA) is associated with postoperative delirium (POD) and postoperative cognitive dysfunction (POCD). The mechanisms that could predispose OSA patients to these disorders are also explored.

SOURCE

Relevant literature was identified by searching for pertinent terms in Medline®, Pubmed, ScopusTM, and Google scholar databases. Case reports, abstracts, review articles, original research articles, and meta-analyses were reviewed. The bibliographies of retrieved sources were also searched to identify relevant papers.

PRINCIPAL FINDINGS

Seven studies have investigated the association between OSA and POD, with mixed results. No studies have examined the potential link between OSA and POCD. If these relationships exist, they could be mediated by several mechanisms, including increased neuroinflammation, blood-brain barrier breakdown, cerebrovascular disease, Alzheimer's disease neuropathology, disrupted cerebral autoregulation, sleep disruption, sympathovagal imbalance, and/or disrupted brain bioenergetics.

CONCLUSION

There is very limited evidence that OSA plays a role in postoperative neurocognitive disorders because few studies have been conducted in the perioperative setting. Additional perioperative prospective observational cohort studies and randomized controlled trials of sleep apnea treatment are needed. These investigations should also assess potential underlying mechanisms that could predispose patients with OSA to postoperative neurocognitive disorders. This review highlights the need for more research to improve postoperative neurocognitive outcomes for patients with OSA.

Effect of dexmedetomidine on postoperative systemic inflammation and recovery in patients undergoing digest tract cancer surgery: A meta-analysis of randomized controlled trials

Perioperative immune function, postoperative cognitive function and prognosis are momentous issues for patients undergoing digestive tract cancer surgery. Studies have investigated the efficacy of dexmedetomidine (DEX) administration on these issues, but the results are inconsistent. Therefore, this meta-analysis aimed to summarize all the existing evidence and draw a conclusion more accurately on these associations. Trials were located through electronic searches of the PubMed, Embase, the Cochrane Library and Web of Science databases sources (from the establishment date of databases to April 2022). Bibliographies of the retrieved articles were checked. A total of 17 RCTs involving 1619 patients were included. The results showed that DEX decreased the level of C-reactive protein (SMD = -4.26, 95%CI: -6.16, -2.36), TNF-α (SMD = -4.22, 95%CI: -5.91, -2.54) and IL-6 (SMD = -2.71, 95%CI: -4.46, -0.97), and increased the level of IL-10 (SMD = 1.74, 95%CI: 0.25, 3.24). DEX also increased CD4+ T cells (SMD = 0.55, 95%CI: 0.29, 0.82) and CD4+/CD8+ ratio (SMD = 0.62, 95%CI: 0.24, 1.01). Thus, DEX was associated with alleviation of postoperative systemic inflammatory response and immune dysfunction. Furthermore, DEX increased mini-mental state examination scores at 12h (SMD = 1.10, 95%CI: 0.74,1.45), 24h (SMD = 0.85, 95%CI: 0.59, 1.11), 48h (SMD = 0.89, 95%CI: 0.50, 1.28) and 72h (SMD = 0.75, 95%CI: 0.38, 1.11) after surgery. DEX decreased the occurrence of postoperative cognitive dysfunction (POCD) at 24h (OR = 0.22, 95%CI: 0.11, 0.46) and 72h (OR = 0.39, 95%CI: 0.22, 0.68) after surgery. DEX decreased first flatus time (SMD = -1.55, 95%CI: -2.82, -0.27) and hospital stay (SMD = -1.23, 95%CI: -1.88, -0.59). Therefore, based on perioperative immune dysfunction alleviation, DEX attenuated POCD and potential neuroinflammation, improved postoperative recovery and clinical prognosis of patients undergoing digest tract cancer surgery. Further studies are necessary to elucidate the clinical application of DEX from an immunological perspective.

A Common Human Brain-Derived Neurotrophic Factor Polymorphism Leads to Prolonged Depression of Excitatory Synaptic Transmission by Isoflurane in Hippocampal Cultures

Multiple presynaptic and postsynaptic targets have been identified for the reversible neurophysiological effects of general anesthetics on synaptic transmission and neuronal excitability. However, the synaptic mechanisms involved in persistent depression of synaptic transmission resulting in more prolonged neurological dysfunction following anesthesia are less clear. Here, we show that brain-derived neurotrophic factor (BDNF), a growth factor implicated in synaptic plasticity and dysfunction, enhances glutamate synaptic vesicle exocytosis, and that attenuation of vesicular BDNF release by isoflurane contributes to transient depression of excitatory synaptic transmission in mice. This reduction in synaptic vesicle exocytosis by isoflurane was acutely irreversible in neurons that release less endogenous BDNF due to a polymorphism (BDNF Val66Met; rs6265) compared to neurons from wild-type mice. These effects were prevented by exogenous application of BDNF. Our findings identify a role for a common human BDNF single nucleotide polymorphism in persistent changes of synaptic function following isoflurane exposure. These short-term persistent alterations in excitatory synaptic transmission indicate a role for human genetic variation in anesthetic effects on synaptic plasticity and neurocognitive function.

Dexmedetomidine Mitigates Microglial Activation Associated with Postoperative Cognitive Dysfunction by Modulating the MicroRNA-103a-3p/VAMP1 Axis

Surgery-induced microglial activation is critical in mediating postoperative cognitive dysfunction (POCD) in elderly patients, where the important protective effect of dexmedetomidine has been indicated. However, the mechanisms of action of dexmedetomidine during the neuroinflammatory response that underlies POCD remain largely unknown. We found that lipopolysaccharide (LPS) induced substantial inflammatory responses in primary and BV2 microglial cells. The screening of differentially expressed miRNAs revealed that miR-103a-3p was downregulated in these cell culture models. Overexpression of miR-103a-3p mimics and inhibitors suppressed and enhanced the release of inflammatory factors, respectively. VAMP1 expression was upregulated in LPS-treated primary and BV-2 microglial cells, and it was validated as a downstream target of miR-103-3p. VAMP1-knockdown significantly inhibited the LPS-induced inflammatory response. Dexmedetomidine treatment markedly inhibited LPS-induced inflammation and the expression of VAMP1, and miR-103a-3p expression reversed this inhibition. Moreover, dexmedetomidine mitigated microglial activation and the associated inflammatory response in a rat model of surgical trauma that mimicked POCD. In this model, dexmedetomidine reversed miR-103a-3p and VAMP1 expression; this effect was abolished by miR-103a-3p overexpression. Taken together, the data show that miR-103a-3p/VAMP1 is critical for surgery-induced microglial activation of POCD.

Differential Cognitive Functioning and Benefit From Surgery in Patients Undergoing Coronary Artery Bypass Grafting and Carotid Endarterectomy

Background

Stenosing atherosclerosis in both coronary and carotid arteries can adversely affect cognition. Also their surgical treatments, coronary artery bypass grafting (CABG) and carotid endarterectomy (CEA), are associated with cognitive changes, but the mechanisms of cognitive decline or improvement may not be the same. This study was designed to compare the cognitive profile and outcome in patients undergoing surgical treatment for coronary or carotid disease.

Methods

A total of 100 CABG patients and 44 CEA patients were recruited in two previously reported studies. They were subjected to a comprehensive neuropsychological examination prior to surgery and in the acute (3-8 days) and stable (3 months) phase after operation. A group of 17 matched healthy controls were assessed with similar intervals. We used linear mixed models to compare cognitive trajectories within six functional domains between the CABG, CEA and control groups. Postoperative cognitive dysfunction (POCD) and improvement (POCI) were determined with the reliable change index method in comparison with healthy controls.

Results

Before surgery, the CEA patients performed worse than CABG patients or healthy controls in the domains of executive functioning and processing speed. The CABG patients exhibited postoperative cognitive dysfunction more often than the CEA patients in most cognitive domains in the acute phase but had regained their performance in the stable phase. The CEA patients showed more marked postoperative improvement in executive functioning than the CABG group in the acute phase, but the difference did not reach significance in the stable phase.

Conclusion

Our findings suggest that anterior cerebral dysfunction in CEA patients impairs preoperative cognition more severely than global brain dysfunction in CABG patients. However, CEA may have more beneficial effects on cognition than CABG, specifically in executive functions mainly operated by the prefrontal lobes. In addition, the results underline that POCD is a heterogeneous condition and dependent on type of revascularization surgery.

Short-term perioperative cognitive therapy combined with rehabilitation exercise reduces the incidence of neurocognitive disorder in elderly patients: a randomized controlled trial

BACKGROUND

To investigate whether short-term perioperative cognitive therapy combined with rehabilitation exercise decreases the incidence of neurocognitive disorder (NCD) in elderly patients who have undergone hip joint replacement surgery. This was a randomized, parallel controlled trial on elderly patients who underwent unilateral total hip joint replacement surgery at the Third Xiangya Hospital of Central South University.

METHODS

Patients in the perioperative cognitive therapy combined with rehabilitation exercise group underwent preoperative cognitive training and postoperative cognitive training, rehabilitation exercise, and standardized health care services; the control group received only postoperative standardized health care service. Patients with NCD were defined as those with two or more abnormalities on 11 neuropsychological tests. Of the 607 individuals that we screened, 86 (exercise, 50; control, 36) who completed the study were included.

RESULTS

The baseline characteristics were similar for the two groups. The incidence of NCD in the exercise group (10%, 5/50) was significantly lower than that in the control group (27.8%, 10/36) (P=0.032). The HVLT-R, HVLT-R delayed recall test, and HVLT-R recognition discriminating index were significantly improved in the exercise group compared with the control group (all P<0.05). Our findings highlight the clinical significance of perioperative cognitive exercise combined with rehabilitation exercise in preventing NCD among patients after surgery and anesthesia.

CONCLUSIONS

Our study indicates that perioperative cognitive therapy combined with rehabilitation exercise can effectively reduce the incidence of NCD in elderly patients after total hip joint replacement surgery.

Postoperative cognitive dysfunction in older surgical patients associated with increased healthcare utilization: a prospective study from an upper-middle-income country

Background

Perioperative neurocognitive disorder includes postoperative cognitive dysfunction (POCD) and postoperative delirium (POD). Concerning inconclusive consequences of POCD compared with POD, we explored the association between either POCD or POD and functional decline as well as healthcare utilization.

Methods

Patients aged at least 60 years who underwent a major operation were enrolled. POCD was defined as a decrease in the Montreal Cognitive Assessment (MoCA) score (≥ 2) 1 week after surgery. Postoperative delirium (POD) was defined according to the criteria of the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). The primary outcome was instrumental activities of daily living (IADLs) 3 months after discharge. Secondary outcomes were the length of stay (LOS), hospital cost, and factors that affected functional decline 3 months after surgery. The multivariate model, including potential confounding factors, namely age, gender, surgery type, and postoperative complications, was used to analyze possible factors that influenced a reduction in function, and the results were expressed by using adjusted relative risk (RR) and 95%CI.

Results

Two hundred eighty-nine patients with a mean age of 72 years were enrolled. The incidence of POCD at 1 week was 28.5%. At their 3-month follow-ups, the patients with POCD were not associated with IADL decline. Nevertheless, patients with POCD were more likely to need a prolonged LOS (11 days [1, 46] vs. 8 days [2, 42]; P = 0.01), and incur higher hospital costs (8973.43 USD [3481.69, 11 763.74] vs. 5913.62 USD [332.43, 19 567.33]; P < 0.001). Additionally, the patients experiencing POD demonstrated increased risks of reducing their IADLs (adjusted RR 2.33; 95% CI, 1.15–4.71; P = 0.02).

Conclusions

POCD at 1 week leaded to increase healthcare utilization in a middle-income country. POD during hospitalization was associated with a decline in function after surgery and increased health care utilization.

Trial registration

Thai Clinical Trials Registry TCTR20190115001.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12877-022-02873-3.

The Effects of Dexmedetomidine on Perioperative Neurocognitive Outcomes After Noncardiac Surgery: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Objective

The purpose of this review is to examine the effect of dexmedetomidine on delayed neurocognitive recovery (dNCR; cognitive dysfunction ≥1 week postoperative) after major noncardiac surgery.

Background

Dexmedetomidine (DEX) effectively reduces delirium in the intensive care unit and reportedly attenuates cognitive decline following major noncardiac surgery. Ascertaining the true effect on postoperative cognition is difficult because studies are limited by suboptimal selection of cognitive assessment tools, timing of testing, and criteria for defining significant cognitive decline.

Methods

Prospective randomized trials comparing perioperative DEX to placebo for major noncardiac surgery assessing cognitive function ≥1 week postoperative were included. Pediatric, nonhuman, and non-English trials, and those where executive function was not assessed were excluded. Data were abstracted by 3 reviewers independently and in parallel according to PRISMA guidelines. The a priori binary primary outcome is dNCR defined as cognitive function declining by the minimal clinically important difference or accepted alternate measure (eg, Reliable Change Index ≥1.96). Bias was assessed with the Cochrane Collaboration tool. Data were pooled using a random effects model.

Results

Among 287 citations identified, 26 (9%) met criteria for full-text retrieval. Eleven randomized trials (1233 participants) were included for qualitative analysis, and 7 trials (616 participants) were included for meta-analysis of dNCR. Dexmedetomidine did not reduce the incidence of dNCR significantly (OR 0.57, 95% CI 0.30-1.10, P = 0.09) compared with placebo. There was no difference in the incidence of delirium (OR 0.94, 95% CI 0.55-1.63, P = 0.83) and a higher incidence of hemodynamic instability (OR 2.11, 95% CI 1.22-3.65, P = 0.008).

Conclusions

Dexmedetomidine does not reduce dNCR 1 week after major noncardiac surgery. This meta-analysis does not yet support the use of perioperative DEX to improve short term cognitive outcomes at this time; trials underway may yet change this conclusion while larger trials are needed to refine the point estimate of effect and examine long-term cognitive outcomes.

General anesthesia bullies the gut: a toxic relationship with dysbiosis and cognitive dysfunction

Perioperative neurocognitive disorder (PND) is a common surgery outcome affecting up to a third of the elderly patients, and it is associated with high morbidity and increased risk for Alzheimer's disease development. PND is characterized by cognitive impairment that can manifest acutely in the form of postoperative delirium (POD) or after hospital discharge as postoperative cognitive dysfunction (POCD). Although POD and POCD are clinically distinct, their development seems to be mediated by a systemic inflammatory reaction triggered by surgical trauma that leads to dysfunction of the blood-brain barrier and facilitates the occurrence of neuroinflammation. Recent studies have suggested that the gut microbiota composition may play a pivotal role in the PND development by modulating the risk of neuroinflammation establishment. In fact, modulation of gut microbiome composition with pre- and probiotics seems to be effective for the prevention and treatment of PND in animals. Interestingly, general anesthetics seem to have major responsibility on the gut microbiota composition changes following surgery and, consequently, can be an important element in the process of PND initiation. This concept represents an important milestone for the understanding of PND pathogenesis and may unveil new opportunities for the development of preventive or mitigatory strategies against the development of these conditions. The aim of this review is to discuss how anesthetics used in general anesthesia can interact and alter the gut microbiome composition and contribute to PND development by favoring the emergence of neuroinflammation.

Spine Surgery Under Spinal vs General Anesthesia: Prospective Analysis of Quality of Life, Fatigue, and Cognition

BACKGROUND

There has recently been increasing interest in the use of spinal anesthesia (SA) for spine surgery. The literature that compared spine surgery under SA vs general anesthesia (GA) focused on safety, perioperative outcomes, and costs.

OBJECTIVE

To test if SA is associated with less postoperative fatigue, cognitive dysfunction, and better quality of life in patients undergoing lumbar spine surgery compared with GA.

METHODS

We conducted a prospective nonrandomized study in patients undergoing elective lumbar spine surgery under SA or GA by a single surgeon. Fatigue was assessed with the fatigue visual analog scale scale (0-10) and Chalder Fatigue Scale, quality of life with Medical Outcomes Study 12-item Short Form (SF-12), and differences in cognition with Mini-Mental State Examination. Patients were baselined before surgery and assessed again 1 mo after surgery.

RESULTS

Fifty patients completed the study, 25 underwent surgery under SA and 25 under GA. The groups were homogeneous for baseline clinical characteristics, with no differences in preoperative fatigue, quality of life, and cognition. At 1 mo after surgery, SA compared with GA had better fatigue scores: fatigue visual analog scale (2.9 ± 1.5 vs 5.9 ± 2.3 [P < .0001]) and Chalder Fatigue Scale (11.2 ± 3.1 vs 16.9 ± 3.9 [P < .0001]). One month postoperatively, we observed a significant difference in the SF-12 physical component, with SA having 38.8 ± 8.9 vs 29.4 ± 10.3 (P = .002). We did not observe significant postoperative differences in the SF-12 mental component or Mini-Mental State Examination.

CONCLUSION

Our study demonstrates that SA offers unique patient-centered advantages to GA for elective spine surgery. One month after surgery, patients who received SA had less postoperative fatigue and better quality of life.

Relationship Between Depression/Anxiety and Cognitive Function Before and 6 Weeks After Major Non-Cardiac Surgery in Older Adults

OBJECTIVE

To determine the relationship between affective measures and cognition before and after non-cardiac surgery in older adults.

METHODS

Observational prospective cohort study in 103 surgical patients age ≥ 60 years old. All participants underwent cognitive testing, Center for Epidemiologic Studies-Depression, and State Anxiety Inventory screening before and 6 weeks after surgery. Cognitive test scores were combined by factor analysis into 4 cognitive domains, whose mean was defined as the continuous cognitive index (CCI). Postoperative global cognitive change was defined by CCI change from before to after surgery, with negative CCI change indicating worsened postoperative global cognition and vice versa.

RESULTS

Lower global cognition before surgery was associated with greater baseline depression severity (Spearman's r = -0.30, p = 0.002) and baseline anxiety severity (Spearman's r = -0.25, p = 0.010), and these associations were similar following surgery (r = -0.36, p < 0.001; r = -0.26, p = 0.008, respectively). Neither baseline depression or anxiety severity, nor postoperative changes in depression or anxiety severity, were associated with pre- to postoperative global cognitive change.

CONCLUSIONS

Greater depression and anxiety severity were each associated with poorer cognitive performance both before and after surgery in older adults. Yet, neither baseline depression or anxiety symptoms, nor postoperative change in these symptoms, were associated with postoperative cognitive change.

Electroencephalogram-Based Complexity Measures as Predictors of Post-operative Neurocognitive Dysfunction

Physiologic signals such as the electroencephalogram (EEG) demonstrate irregular behaviors due to the interaction of multiple control processes operating over different time scales. The complexity of this behavior can be quantified using multi-scale entropy (MSE). High physiologic complexity denotes health, and a loss of complexity can predict adverse outcomes. Since postoperative delirium is particularly hard to predict, we investigated whether the complexity of preoperative and intraoperative frontal EEG signals could predict postoperative delirium and its endophenotype, inattention. To calculate MSE, the sample entropy of EEG recordings was computed at different time scales, then plotted against scale; complexity is the total area under the curve. MSE of frontal EEG recordings was computed in 50 patients ≥ age 60 before and during surgery. Average MSE was higher intra-operatively than pre-operatively (p = 0.0003). However, intraoperative EEG MSE was lower than preoperative MSE at smaller scales, but higher at larger scales (interaction p < 0.001), creating a crossover point where, by definition, preoperative, and intraoperative MSE curves met. Overall, EEG complexity was not associated with delirium or attention. In 42/50 patients with single crossover points, the scale at which the intraoperative and preoperative entropy curves crossed showed an inverse relationship with delirium-severity score change (Spearman ρ = -0.31, p = 0.054). Thus, average EEG complexity increases intra-operatively in older adults, but is scale dependent. The scale at which preoperative and intraoperative complexity is equal (i.e., the crossover point) may predict delirium. Future studies should assess whether the crossover point represents changes in neural control mechanisms that predispose patients to postoperative delirium.

Effects of inhalation and propofol anaesthesia on postoperative cognitive dysfunction in elderly noncardiac surgical patients: A systematic review and meta-analysis

BACKGROUND

Postoperative cognitive dysfunction (POCD) is a very common event in elderly noncardiac surgical patients. The effects of inhalational anaesthetics and propofol on the incidence of POCD and postoperative cognitive status at different time points after surgery are currently unclear.

METHODS

We searched the Embase, Medline, Cochrane Library, and Web of Science databases for randomized controlled trials (RCTs), in which inhalation anaesthesia and propofol anaesthesia were compared. The incidence of POCD or postoperative cognitive status was assessed in elderly patients undergoing noncardiac surgery.

RESULTS

Fifteen RCTs with 1854 patients were included in this meta-analysis. The incidence of POCD on postoperative Days 2-6 after propofol anaesthesia was markedly lower than that after inhalation anaesthesia (risk ratio (RR): 0.37, 95% confidence interval (CI): 0.15-0.88, P = .025), and Mini-Mental State Examination (MMSE) scores after propofol anaesthesia were substantially higher than those after inhalation anaesthesia (standard mean difference (SMD): 0.59, 95% CI: 0.07-1.11, P = .026). The levels of interleukin-6 (IL-6) and tumour necrosis factor-α (TNF-α) were much lower after propofol anaesthesia than after inhalation anaesthesia (SMD: -2.027, 95% CI: -3.748- -0.307, P = .021; SMD: -0.68, 95% CI: -0.93- -0.43, P < .001).

CONCLUSIONS

The moderate evidence from this meta-analysis shows that, in elderly noncardiac surgical patients, propofol anaesthesia is superior to inhalation anaesthesia for attenuating of early POCD incidence, and low-level evidence shows that cognitive status is higher and systemic inflammation is less severe after propofol anaesthesia in the early days after surgery.

LIMITATIONS

The sample size was not sufficiently large for systemic inflammation, and the tools to identify POCD were not uniform in the included studies.

Predictors of cognitive dysfunction after cardiac surgery: a systematic review

AIMS

Postoperative cognitive dysfunction (POCD) is often experienced by cardiac surgery patients; however, it is not known if some groups of patients experience this more frequently or severely than others.The aim of this systematic review was to identify preoperative and postoperative predictors of cognitive dysfunction in adults following cardiac surgery.

METHODS AND RESULTS

Eight bibliographic databases were searched (January 2005 to March 2021) in relation to cardiac surgery and cognition. Studies including adult patients who had undergone open cardiac surgery and using a validated measurement of cognitive function were included. Full-text review for inclusion, quality assessment, and data extraction were undertaken independently by two authors.A total of 2870 papers were identified, of which 36 papers met the inclusion criteria and were included in the review. The majority were prospective observational studies [n = 28 (75.7%)]. In total, 61 independent predictors (45 preoperative and 16 postoperative) were identified as significant in at least one study; advancing age and education level appear important. Age has emerged as the most common predictor of cognitive outcome.

CONCLUSION

Although a number of predictors of POCD have been identified, they have inconsistently been reported as significantly affecting cognitive outcome. Consistent with previous research, our findings indicate that older patients and those with lower educational levels should be prioritized when developing and trialling interventions to improve cognitive function. These findings are less than surprising if we consider the methodological shortcomings of included studies. It is evident that further high-quality research exploring predictors of POCD is required.

Multi-Order Brain Functional Connectivity Network-Based Machine Learning Method for Recognition of Delayed Neurocognitive Recovery in Older Adults Undergoing Non-cardiac Surgery

Objectives: Delayed neurocognitive recovery (DNR) seriously affects the post-operative recovery of elderly surgical patients, but there is still a lack of effective methods to recognize high-risk patients with DNR. This study proposed a machine learning method based on a multi-order brain functional connectivity (FC) network to recognize DNR.

Method: Seventy-four patients who completed assessments were included in this study, in which 16/74 (21.6%) had DNR following surgery. Based on resting-state functional magnetic resonance imaging (rs-fMRI), we first constructed low-order FC networks of 90 brain regions by calculating the correlation of brain region signal changing in the time dimension. Then, we established high-order FC networks by calculating correlations among each pair of brain regions. Afterward, we built sparse representation-based machine learning model to recognize DNR on the extracted multi-order FC network features. Finally, an independent testing was conducted to validate the established recognition model.

Results: Three hundred ninety features of FC networks were finally extracted to identify DNR. After performing the independent-sample T test between these features and the categories, 15 features showed statistical differences (P < 0.05) and 3 features had significant statistical differences (P < 0.01). By comparing DNR and non-DNR patients’ brain region connection matrices, it is found that there are more connections among brain regions in DNR patients than in non-DNR patients. For the machine learning recognition model based on multi-feature combination, the area under the receiver operating characteristic curve (AUC), accuracy, sensitivity, and specificity of the classifier reached 95.61, 92.00, 66.67, and 100.00%, respectively.

Conclusion: This study not only reveals the significance of preoperative rs-fMRI in recognizing post-operative DNR in elderly patients but also establishes a promising machine learning method to recognize DNR.

Regulatory role of microRNA-320 during off-pump coronary artery bypass grafting with dexmedetomidine adjunct anesthesia

The present study investigated the effects of dexmedetomidine on the expression level of microRNA-320 (miR-320) and neuroglobin (NGB) in patients undergoing off-pump coronary artery bypass grafting (OPCABG). A total of 40 patients undergoing OPCABG were recruited and randomly divided into the dexmedetomidine and normal saline groups (treated before anesthesia), respectively. The NGB levels in the blood samples before and after surgery were analyzed and compared. The CATH.a cells were cultured and induced with dexmedetomidine, and the NGB expression level was detected. CATH.a cells were treated with NGB and lipopolysaccharide (LPS), and the cell survival rate was determined. The miR-320 expression levels in the blood samples and dexmedetomidine-induced cells were detected. Dual-luciferase reporter assay was performed. Compared with control subjects, patients in the dexmedetomidine group had higher NGB levels in the blood. In the CATH.a cells, the dexmedetomidine treatment upregulated the NGB levels. Moreover, upon pre-incubation with NGB and LPS stimulation, dexmedetomidine elevated cell viability. Furthermore, miR-320 expression levels were significantly downregulated in the blood of patients in the dexmedetomidine group, as well as in the dexmedetomidine-induced cells. Dual-luciferase reporter assay confirmed that miRNA-320a directly targeted on NGB, and upregulated miRNA-320a in CATH.a cells decreased cell proliferation activity. Pre-administration of dexmedetomidine can decrease miR-320 expression level in the blood of patients undergoing OPCABG, stimulating the high expression of NGB and increasing the proliferation activity of neuronal cells, which may decrease the postoperative cognitive impairment.

Cerebrospinal Fluid Proteome Changes in Older Non-Cardiac Surgical Patients with Postoperative Cognitive Dysfunction

Background:

Postoperative cognitive dysfunction (POCD), a syndrome of cognitive deficits occurring 1–12 months after surgery primarily in older patients, is associated with poor postoperative outcomes. POCD is hypothesized to result from neuroinflammation; however, the pathways involved remain unclear. Unbiased proteomic analyses have been used to identify neuroinflammatory pathways in multiple neurologic diseases and syndromes but have not yet been applied to POCD.

Objective:

To utilize unbiased mass spectrometry-based proteomics to identify potential neuroinflammatory pathways underlying POCD.

Methods:

Unbiased LC-MS/MS proteomics was performed on immunodepleted cerebrospinal fluid (CSF) samples obtained before, 24 hours after, and 6 weeks after major non-cardiac surgery in older adults who did (n = 8) or did not develop POCD (n = 6). Linear mixed models were used to select peptides and proteins with intensity differences for pathway analysis.

Results:

Mass spectrometry quantified 8,258 peptides from 1,222 proteins in > 50%of patient samples at all three time points. Twelve peptides from 11 proteins showed differences in expression over time between patients with versus without

POCD (q < 0.05), including proteins previously implicated in neurodegenerative disease pathophysiology. Additionally, 283 peptides from 182 proteins were identified with trend-level differences (q < 0.25) in expression over time between these groups. Among these, pathway analysis revealed that 50 were from 17 proteins mapping to complement and coagulation pathways (q = 2.44^*10^–13).

Conclusion:

These data demonstrate the feasibility of performing unbiased mass spectrometry on perioperative CSF samples to identify pathways associated with POCD. Additionally, they provide hypothesis-generating evidence for CSF complement and coagulation pathway changes in patients with POCD.