Depth of anaesthesia and post-operative cognitive dysfunction

miR-182-5p Delivered by Plasma Exosomes Promotes Sevoflurane-Induced Neuroinflammation and Cognitive Dysfunction in Aged Rats with Postoperative Cognitive Dysfunction by Targeting Brain-Derived Neurotrophic Factor and Activating NF-κB Pathway

The objective of this study was to discuss the possible mechanism and effect of miR-182-5p delivered by plasma exosomes on sevoflurane-induced neuroinflammation and cognitive disorder in aged rats with postoperative cognitive dysfunction (POCD). Firstly, aged POCD rat models were constructed by sevoflurane anesthesia and superior mesenteric artery occlusion. Subsequently, exosomes and miR-182-5p were inhibited by injection of GW4869 and miR-182-5p-sponge, respectively. Then, exosomes were extracted from the plasma of rats in each group, followed by the determination of the morphology and diameters of exosomes as well as the expression of exosome markers CD63 and CD81 by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and Western blot. Besides, the Morris water maze (MWM) and fear conditioning test were used to evaluate the learning and memory ability of rats; Western blot to detect the expression levels of neurotrophic factors (brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF)) as well as NF-κB pathway-related proteins (p65 and p-p65) in rat hippocampal tissues or PC-12 cells; qRT-PCR to assess the expression levels of miR-182-5p and BDNF in rat plasma, plasma exosomes, hippocampal tissues, and PC-12 cells; ELISA to evaluate the levels of tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-1β in rat hippocampal tissues; and dual-luciferase reporter assay to verify the targeting relationship between miR-182-5p and BDNF. After examination, the results were obtained as follows. miR-182-5p expression was up-regulated in POCD rats and could be delivered by plasma exosomes. Inhibition of plasma exosomes or miR-182-5p could significantly ameliorate learning and memory disorders; decrease the levels of pro-inflammatory cytokines TNF-α, IL-6, and IL-1β; increase the expression of BDNF and NGF; and inhibit the activity of NF-κB signaling pathway in POCD rat hippocampus. In addition, miR-182-5p could also target and inhibit BDNF. All in all, miR-182-5p delivered by plasma exosomes promotes sevoflurane-induced neuroinflammation and cognitive dysfunction in aged POCD rats by targeting BDNF and activating the NF-κB pathway.

Is the analogue cognitive test from the ISPOCD equivalent to the digital cognitive test Mindmore? A protocol for a randomised cross-over study including qualitative interviews with self-reported healthy seniors

INTRODUCTION

Postoperative cognitive decline affects cognitive domains such as executive functions, memory, concentration and information processing. The analogue neuropsychological test developed by the International Study Group of Postoperative Cognitive Dysfunction (ISPOCD) is a well-established test for assessing cognitive performance. However, analogue tests are time-consuming, rarely cost-effective and can be at risk of administration bias. Digital solutions are comparable to analogue ones, have higher degrees of compliance and enable more standardised execution than analogue tests. Currently, there is a lack of recommendations for clinical evaluation of the patient's cognition in the perioperative setting, standard care usually means no cognitive assessments prior or after the surgery. There is a need to find an equivalent neuropsychological test to the ISPOCD to make it accessible and easier to implement in a clinical context for perioperative patients. This study aims to examine how healthy seniors perform on two neuropsychological tests, analogue versus digital and measure equivalency between tests with correlation analysis.

METHODS AND ANALYSIS

This study will use a randomised cross-over design, including qualitative interviews regarding test experiences. Healthy participants ≥60 years of age will be eligible to participate in the study. Cognitive function will be measured by using the ISPOCD test and the Mindmore digital test. The participants will self-report depressive symptoms with the Geriatric Depression Scale-15, user experience of the digital test using a modified version of the System Usability Scale and answer questionnaires targeting their experiences after the tests. Furthermore, according to the Swedish Quality of Recovery Scale, self-reported concentration difficulties will also be measured.

ETHICS AND DISSEMINATION

The study has been approved by the Swedish Ethical Review Authority (Dnr 2021-05486-01) and will follow the principles outlined in the 1964 Helsinki Declaration and its later amendments. Results from this study will be disseminated in peer-reviewed journals, at scientific conferences, and in social media.

TRIAL REGISTRATION NUMBER

2021-01095; ClinicalTrials.gov.

Comparison of digital games as a cognitive function assessment tool for current standardized neuropsychological tests

Objective

Cognitive dysfunction may occur postoperatively. Fast and efficient assessment of Postoperative Cognitive Dysfunction (POCD) can minimize loss of quality of life, and therefore, a study comparing a digital game with standard neuropsychological tests to assess executive, mnemonic, and attention functions to evaluate POCD seems to be relevant both for research and clinical practice.

Methods

A battery of standardized tests and a digital game (MentalPlus®) were administered to 60 patients at the Central Institute of Hospital das Clínicas in São Paulo (36 women and 24 men), with ages between 29 and 82 years, pre- and post-surgery performed under anesthesia. Correlation and linear regression model were used to compare the scores obtained from the standardized tests to the scores of the six executive and cognitive functions evaluated by the game (short- and long-term memory, selective and alternating attention, inhibitory control, and visual perception).

Results

After correlation analysis, a statistically significant result was found mainly for the correlation between the scores from the phase of the digital game assessing the visuoperception function and the scores from the A and B cards of the Stroop Test (p < 0.001, r = 0.99 and r = 0.64, respectively), and the scores from TMTA (p = 0.0046, r = 0.51). We also found a moderate correlation between the phase of the game assessing short-memory function and VVLT (p < 0.001, r = 0.41). No statistically significant correlations were found for the other functions assessed.

Conclusion

The digital game provided scores in agreement with standardized tests for evaluating visual perception and possibly short-term memory cognitive functions. Further studies are necessary to verify the correlation of other phases of the digital game with standardized tests assessing cognitive functions.

Patients' experiences of early postoperative cognition and its relation to cognitive decline and inflammatory responses: a protocol for a mixed-methods study

INTRODUCTION

In the early weeks after surgery, patients may experience cognitive changes and impaired memory and concentration-changes commonly referred to as postoperative cognitive decline. It is often the patient and/or a relative that initially detects a change in cognitive capacity after surgery, typically when resuming daily activities. We lack information about how patients experience early postoperative cognition (delayed neurocognitive recovery) and if these experiences can be reflected in biochemical pattern of inflammatory signalling molecules, cognitive function as well as on quality of postoperative recovery.

METHODS AND ANALYSIS

The study has a mixed-methods design that is integration of qualitative and quantitative data within a single investigation. Participants included will be patients aged ≥60 years that are undergoing major elective joint replacement surgery (n=40) and their relative. Patient's experience of his/her early cognition will be captured by interviews on postoperative day 13-16 during the follow-up visit. A relative will also be interviewed on the same day or the day after. Cognitive function will be measured preoperatively and on postoperative day 13-16 using the International Study Group of Postoperative Cognitive Dysfunction test battery. Symptoms/discomfort will be measured preoperatively and postoperatively (on postoperative day 1 and 2 and at the follow-up visit day 13-16) by the Swedish version of Quality of Recovery and by a visual analogue scale assessing pain intensity. Biomarkers will also be collected at the same time points. The findings from the interviews will be sorted out depending on group stratification (no delayed neurocognitive recovery and delayed neurocognitive recovery). The qualitative and quantitative findings will be compared to seek for similarities and differences.

ETHICS AND DISSEMINATION

The project has been approved by the Swedish Ethical Review Authority (2019-02968) and will follow the principles outlined in the 1964 Helsinki Declaration and its later amendments. Results from this study will be disseminated in peer-reviewed journals, scientific conferences and in social media.

Electroencephalography and Brain Oxygenation Monitoring in the Perioperative Period

Maintaining brain function and integrity is a pivotal part of anesthesiological practice. The present overview aims to describe the current role of the 2 most frequently used monitoring methods for evaluation brain function in the perioperative period, ie, electroencephalography (EEG) and brain oxygenation monitoring. Available evidence suggests that EEG-derived parameters give additional information about depth of anesthesia for optimizing anesthetic titration. The effects on reduction of drug consumption or recovery time are heterogeneous, but most studies show a reduction of recovery times if anesthesia is titrated along processed EEG. It has been hypothesized that future EEG-derived indices will allow a better understanding of the neurophysiological principles of anesthetic-induced alteration of consciousness instead of the probabilistic approach most often used nowadays.Brain oxygenation can be either measured directly in brain parenchyma via a surgical burr hole, estimated from the venous outflow of the brain via a catheter in the jugular bulb, or assessed noninvasively by near-infrared spectroscopy. The latter method has increasingly been accepted clinically due to its ease of use and increasing evidence that near-infrared spectroscopy-derived cerebral oxygen saturation levels are associated with neurological and/or general perioperative complications and increased mortality. Furthermore, a goal-directed strategy aiming to avoid cerebral desaturations might help to reduce these complications. Recent evidence points out that this technology may additionally be used to assess autoregulation of cerebral blood flow and thereby help to titrate arterial blood pressure to the individual needs and for bedside diagnosis of disturbed autoregulation.

Near Infrared Spectroscopy Based Clinical Algorithm Applicability During Spinal Neurosurgery and Postoperative Cognitive Disturbances

Background and Objectives: Postoperative cognitive disturbances (POCD) can significantly alter postoperative recovery. Inadequate intraoperative cerebral oxygen supply is one of the inciting causes of POCD. Near-infrared spectroscopy (NIRS) devices monitor cerebral oxygen saturation continuously and can help to guide intraoperative patient management. The aim of the study was to evaluate the applicability of the NIRS-based clinical algorithm during spinal neurosurgery and to find out whether it can influence postoperative cognitive performance. Materials and Methods: Thirty four patients scheduled for spinal neurosurgery were randomized into a study group (n = 23) and a control group (n = 11). We monitored regional cerebral oxygen saturation (rScO2) throughout surgery, using a NIRS device (INVOS 4100). If rScO2 dropped bilaterally or unilaterally by more than 20% from baseline values, or under an absolute value of 50%, the NIRS-based algorithm was initiated in the study group. In the control group, rScO2 was monitored blindly. To evaluate cognitive function, Montreal-Cognitive Assessment (MoCA) scale was used in both groups before and after the surgery. Results: In the study group, rScO2 dropped below the threshold in three patients and the NIRS-based algorithm was activated. Firstly, we verified correct positioning of the head; secondly, we increased mean systemic arterial pressure in the three patients by injecting repeated intravenous bolus doses of Ephedrine, ultimately resulting in an rScO2 increase above the approved threshold level. None of the three patients showed POCD. In the control group, one patient showed a drop in rScO2 of 34% from baseline and presented with a POCD. RScO2 drop occurred with other stable intraoperative measurements. Conclusions: A significant rScO2 drop may occur during spinal surgery in prone position despite other intraoperative measurements remaining stable, allowing it to stay otherwise unrecognized. Use of the NIRS-based clinical algorithm can help to avoid POCD in patients after spinal surgery.

BIS-guided deep anesthesia decreases short-term postoperative cognitive dysfunction and peripheral inflammation in elderly patients undergoing abdominal surgery

OBJECTIVES

Postoperative cognitive dysfunction (POCD) is a common clinical complication, with an underlying pathophysiology linked to heightened levels of neuroinflammation. However, it requires clarification as to whether the depth of anesthesia modulates postoperative cognitive dysfunction. This study investigated the association between depth of anesthesia and POCD in elderly patients undergoing abdominal surgery.

METHODS

A total of 120 patients aged 60 years or older who were planned for abdominal surgery under total intravenous anesthesia were included in this study. The depth of anesthesia was guided by monitoring Bispectral Index (BIS) data. All study participants completed a battery of nine neuropsychological tests before surgery and at 7 days and 3 months after surgery. POCD was calculated by using the reliable change index. Plasma concentration of C-reactive protein (CRP), interleukin (IL)-1β, IL-10, S-100β, and norepinephrine (NE) were measured.

RESULTS

The incidence of POCD at 7 days after surgery in the deep anesthesia group was 19.2% (10/52), which was significantly lower (p = 0.032) than the light anesthesia group 39.6% (21/53). The depth of anesthesia had no effect on POCD at 3 months after surgery (10.3% vs 14.6%, respectively, p = 0.558). Similarly, plasma levels of CRP and IL-1β in deep anesthesia group were lower than that in light anesthesia group at 7 days after surgery (p < 0.05), but not at 3 months after surgery (p > 0.05). There were no significant differences in the plasma concentration of IL-10, S-100β, and NE between the groups (p > 0.05).

CONCLUSIONS

Deep anesthesia under total intravenous anesthesia could decrease the occurrence of short-term POCD and inhibit postoperative peripheral inflammation in elderly patients undergoing abdominal surgery, compared with light anesthesia.

Effects of Memantine in a Mouse Model of Postoperative Cognitive Dysfunction

Persistent impairment in cognitive functioning postoperatively is reported by clinical and animal studies, and is labeled as postoperative cognitive dysfunction (POCD). Evidence points to an exaggerated neuroinflammatory response resulting from peripheral systemic inflammation after surgery, with subsequent cytokine-induced glutamatergic excitotoxicity and synaptic impairment. These immunological changes, among many others, are also observed in Alzheimer’s disease. Memantine is an N-methyl-D-aspartate receptor (NMDAR) antagonist commonly used to treat Alzheimer’s disease. Surprisingly, little research exists on the role of memantine in preventing POCD. The purpose of this study is to investigate the effects of memantine on a spectrum of cognitive functions postoperatively. Mice were divided into 3 groups and each received treatment for 4 weeks. Placebo groups received a placebo then underwent either a sham procedure or a laparotomy procedure. The memantine group received memantine hydrochloride then underwent a laparotomy procedure. Cognitive tests were performed on postoperative days (POD) 1 and 7. Compared to sham-operated mice, placebo groups that underwent a laparotomy procedure showed impaired memory in the Morris water maze test, higher anxiety-like behavior in the open field and the elevated plus maze tests, increased depression-like behavior in the tail suspension test, and lack of preference for social novelty in the three-chamber test. On the other hand, memantine-treated mice that underwent a laparotomy procedure showed enhanced memory on POD7, improved depression-like behavior on POD1 and POD7, enhanced preference for social novelty on POD1, and no improvement in anxiety-like behavior. These findings suggest a potential protective effect of memantine in mice postoperatively on memory, depression-like behavior, and preference for social novelty.

Ropivacaine for Intercostal Nerve Block Improves Early Postoperative Cognitive Dysfunction in Patients Following Thoracotomy for Esophageal Cancer

BACKGROUND Ropivacaine is commonly used as an intercostal nerve block, but its effects on postoperative cognitive dysfunction (POCD) have not previously been investigated. This study aimed to examine the effects of the use of ropivacaine as an intercostal nerve block on early POCD, postoperative analgesia, and inflammation in patients following thoracotomy for esophageal cancer. MATERIAL AND METHODS One hundred patients with esophageal cancer undergoing thoracotomy were randomly divided into a group with intercostal nerve block (group A) (n=50) and a control group (group B) (n=50). The cognitive function score and visual analog scale (VAS) scores for pain were measured at one hour before surgery (T1), two hours after surgery (T2), 12 hours after surgery (T3), and 24 hours after surgery (T4). Blood samples were collected at each time point, and plasma levels of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), IL-10, and S100-β were measured using an enzyme-linked immunosorbent assay (ELISA). Cognitive function was determined using the Mini-Mental State Examination (MMSE) scale. RESULTS The VAS scores in group A were significantly lower compared with group B (p<0.05). In the T2, T3, and T4 time points, group A had significantly increased MMSE scores compared with group B (p<0.05). Compared with group B, the levels of IL-6 and TNF-a were significantly decreased in group A at T3 and T4 (p<0.05), while the levels of IL-10 were significantly increased (p<0.05) when compared with group A. CONCLUSIONS The use of the intercostal nerve block, ropivacaine, improved early PCOD in patients following thoracotomy for esophageal cancer.

Possible neurotoxicity of the anesthetic propofol: evidence for the inhibition of complex II of the respiratory chain in area CA3 of rat hippocampal slices

Propofol is the most frequently used intravenous anesthetic for induction and maintenance of anesthesia. Propofol acts first and formost as a GABA_A-agonist, but effects on other neuronal receptors and voltage-gated ion channels have been described. Besides its direct effect on neurotransmission, propofol-dependent impairment of mitochondrial function in neurons has been suggested to be responsible for neurotoxicity and postoperative brain dysfunction. To clarify the potential neurotoxic effect in more detail, we investigated the effects of propofol on neuronal energy metabolism of hippocampal slices of the stratum pyramidale of area CA3 at different activity states. We combined oxygen-measurements, electrophysiology and flavin adenine dinucleotide (FAD)-imaging with computational modeling to uncover molecular targets in mitochondrial energy metabolism that are directly inhibited by propofol. We found that high concentrations of propofol (100 µM) significantly decrease population spikes, paired pulse ratio, the cerebral metabolic rate of oxygen consumption (CMRO₂), frequency and power of gamma oscillations and increase FAD-oxidation. Model-based simulation of mitochondrial FAD redox state at inhibition of different respiratory chain (RC) complexes and the pyruvate-dehydrogenase show that the alterations in FAD-autofluorescence during propofol administration can be explained with a strong direct inhibition of the complex II (cxII) of the RC. While this inhibition may not affect ATP availability under normal conditions, it may have an impact at high energy demand. Our data support the notion that propofol may lead to neurotoxicity and neuronal dysfunction by directly affecting the energy metabolism in neurons.

Processed electroencephalogram and evoked potential techniques for amelioration of postoperative delirium and cognitive dysfunction following non-cardiac and non-neurosurgical procedures in adults

BACKGROUND

Postoperative delirium (POD) and postoperative cognitive dysfunction (POCD) may complicate a patient's postoperative recovery in several ways. Monitoring of processed electroencephalogram (EEG) or evoked potential (EP) indices may prevent or minimize POD and POCD, probably through optimization of anaesthetic doses.

OBJECTIVES

To assess whether the use of processed EEG or auditory evoked potential (AEP) indices (bispectral index (BIS), narcotrend index, cerebral state index, state entropy and response entropy, patient state index, index of consciousness, A-line autoregressive index, and auditory evoked potentials (AEP index)) as guides to anaesthetic delivery can reduce the risk of POD and POCD in non-cardiac surgical or non-neurosurgical adult patients undergoing general anaesthesia compared with standard practice where only clinical signs are used.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase and clinical trial registry databases up to 28 March 2017. We updated this search in February 2018, but these results have not been incorporated in the review.

SELECTION CRITERIA

We included randomized or quasi-randomized controlled trials comparing any method of processed EEG or evoked potential techniques (entropy, BIS, AEP etc.) against a control group where clinical signs were used to guide doses of anaesthetics in adults aged 18 years or over undergoing general anaesthesia for non-cardiac or non-neurosurgical elective operations.

DATA COLLECTION AND ANALYSIS

We used the standard methodological procedures expected by Cochrane. Our primary outcomes were: occurrence of POD; and occurrence of POCD. Secondary outcomes included: all-cause mortality; any postoperative complications; and postoperative length of stay. We used GRADE to assess the quality of evidence for each outcome.

MAIN RESULTS

We included six randomized controlled trials (RCTs) with 2929 participants comparing processed EEG or EP indices-guided anaesthesia with clinical signs-guided anaesthesia. There are five ongoing studies and one study awaiting classification.Anaesthesia administration guided by the indices from a processed EEG (bispectral index) probably reduces the risk of POD within seven days after surgery with risk ratio (RR) of 0.71 (95% CI 0.59 to 0.85; number needed to treat for an additional beneficial outcome (NNTB) of 17, 95% CI 11 to 34; 2197 participants; 3 RCTs; moderate quality of evidence). Three trials also showed the lower rate of POCD at 12 weeks after surgery (RR 0.71, 95% CI 0.53 to 0.96; NNTB 38, 95% CI 21 to 289; 2051 participants; moderate-quality evidence), but it is uncertain whether processed EEG indices reduce POCD at one week (RR 0.84, 95% CI 0.69 to 1.02; 3 trials; 1989 participants; moderate-quality evidence), and at 52 weeks (RR 0.30, 95% CI 0.05 to 1.80; 1 trial; 59 participants; very low quality of evidence). There may be little or no effect on all-cause mortality (RR 1.01, 95% CI 0.62 to 1.64; 1 trial; 1155 participants; low-quality evidence). One trial suggested a lower risk of any postoperative complications with processed EEG (RR 0.51, 95% CI 0.37 to 0.71; 902 participants, moderate-quality evidence). There may be little or no effect on reduced postoperative length of stay (mean difference -0.2 days, 95% CI -2.02 to 1.62; 1155 participants; low-quality evidence).

AUTHORS' CONCLUSIONS

There is moderate-quality evidence that optimized anaesthesia guided by processed EEG indices could reduce the risk of postoperative delirium in patients aged 60 years or over undergoing non-cardiac surgical and non-neurosurgical procedures. We found moderate-quality evidence that postoperative cognitive dysfunction at three months could be reduced in these patients. The effect on POCD at one week and over one year after surgery is uncertain. There are no data available for patients under 60 years. Further blinded randomized controlled trials are needed to elucidate strategies for the amelioration of postoperative delirium and postoperative cognitive dysfunction, and their consequences such as dementia (including Alzheimer's disease (AD)) in both non-elderly (below 60 years) and elderly (60 years or over) adult patients. The one study awaiting classification and five ongoing studies may alter the conclusions of the review once assessed.

POCD in patients receiving total knee replacement under deep vs light anesthesia: A randomized controlled trial

Objectives

Clinical observation, as well as randomized controlled trials, indicated an increasing rate of postoperative cognitive dysfunction (POCD) with increasing depth of general anesthesia. However, the findings are subject to bias due to varying degree of analgesia. In this trial, we compared the rate of POCD between patients receiving light versus high anesthesia while holding analgesia comparable using nerve block.

Methods

Elderly patients (≧60 years) receiving elective total knee replacement were randomized to receive the surgery under general anesthesia at BIS 40-50 (LOBIS group) or BIS 55-65 (HIBIS group). The femoral nerve and the sciatic nerve were blocked under ultrasonic guidance in all patients before induction. Cognitive performance was assessed with Montreal cognitive assessment (MoCA) at the baseline and 1d, 3d, and 7d after the surgery. POCD was defined by Z score of >1.96 using cross-reference. The extubation time and recovery time were also compared.

Results

A total of 66 patients were randomized; 60 (n = 30 per group) completed trial as the protocol specified. POCD occurred in six patients (20%) in the LOBIS group vs. in one patient (3.3%) in the HIBIS group (Figure 3, p = .04). In all seven cases, the diagnosis of POCD was based on MoCA assessment on 1d after the surgery. Assessment in 3d and 7d after surgery did not reveal POCD in any case. Extubation time was longer in the LOBIS group (12.16 ± 2.58 vs. 5.77 ± 3.01 min in the HIBIS group (p < .001)). The time of comeback of directional ability was 13.47 ± 3.14 and 6.17 ± 3.23 min in the LOBIS and HIBIS groups, respectively (p < .001).

Conclusions

In elderly patients receiving a total knee replacement, lighter anesthesia could reduce the rate of POCD with complete analgesia during surgery.

Effect of sugammadex versus neostigmine/atropine combination on postoperative cognitive dysfunction after elective surgery

This study aimed to assess the effects of sugammadex and neostigmine/atropine on postoperative cognitive dysfunction (POCD) in adult patients after elective surgery. A randomised, double-blind controlled trial was carried out on 160 American Society of Anesthesiologists physical status I to III patients who were >40 years. The Mini-Mental State Evaluation, clock-drawing test and the Isaacs Set test were used to assess cognitive function at three timepoints: 1) preoperatively, 2) one hour postoperatively, and 3) at discharge. The anaesthetic protocol was the same for all patients, except for the neuromuscular block reversal, which was administered by random allocation using either sugammadex or neostigmine/atropine after the reappearance of T2 in the train-of-four sequence. POCD was defined as a decline ≥1 standard deviation in ≥2 cognitive tests. The incidence of POCD was similar in both groups at one hour postoperatively and at discharge (28% and 10%, in the neostigmine group, 23% and 5.4% in the sugammadex group, P=0.55 and 0.27 respectively). In relation to individual tests, a significant decline of clock-drawing test in the neostigmine group was observed at one hour postoperatively and at discharge. For the Isaacs Set test, a greater decline was found in the sugammadex group. These findings suggest that there are no clinically important differences in the incidence of POCD after neostigmine or sugammadex administration.

The anhepatic phase extended by temporary portocaval shunt does not affect anesthetic sensitivity and postoperative cognitive function: A case-control study

Temporary portocaval shunt (TPCS) prolongs the duration of the anhepatic phase, during which anesthetic sensitivity is highest among the 3 phases of living donor liver transplantation (LDLT). Cognitive dysfunction has been associated with increased anesthetic sensitivity and poor hepatic function. Therefore, we assessed anesthetic sensitivity to desflurane and perioperative cognitive function in patients undergoing LDLT, in whom the duration of the anhepatic phase was extended by TPCS to test the hypothesis that the prolonged anhepatic phase increases anesthetic sensitivity and causes postoperative cognitive decline.This case-control study was conducted in 67 consecutive patients undergoing LDLT from February 2014 to January 2016. Anesthesia was maintained at a 0.6 end-tidal age-adjusted minimum alveolar concentration of desflurane. The bispectral index (BIS) was maintained at less than 60 and averaged at 1-minute intervals. The mini-mental state examination (MMSE-KC) was performed 1 day before and 7 days after the LDLT. All parameters were compared between the patients undergoing TPCS (TPCS group) and the remaining patients (non-TPCS group).TPCS was performed in 16 patients (24%). TPCS prolonged the duration of the anhepatic phase (125.9 ± 29.4 vs 54.9 ± 20.5 minutes [mean ± standard deviation], P < 0.0001). The averaged BIS values during the 3 phases were comparable between the 2 groups. No significant interval changes in the averaged BIS values were observed during the 3 consecutive phases. Similarly, there were no significant differences in MMSE-KC score assessed 1 day before and 7 days after LDLT between the 2 groups. The preoperative MMSE-KC scores were unchanged postoperatively in the 2 groups.The extension of the anhepatic phase did not affect anesthetic sensitivity and postoperative cognitive function.

Original Research: Establishment of an early embolus-related cerebral injury model after cardiopulmonary bypass in miniature pigs

Embolus-related cerebral injury is still a serious adverse event after cardiopulmonary bypass (CPB). But there is no stable animal model for basic and clinical research purposes. We chose miniature pig to establish a stable animal model of embolus-related cerebral injury after CPB and verified the validity of results by correlating the histopathological findings with those of diffusion-weighted magnetic resonance imaging (DW-MRI). Based on different treatment regimens, 24 male miniature pigs were randomly assigned into four groups: Control, CPB, embolus, and CPB-embolus groups. DW-MRI was performed before and after surgery to diagnose and locate the brain lesions. Histopathological changes in brain tissues were examined using H&E and Nissl staining. All surgical procedures were uneventful with 100% postoperative survival of pigs. Two animals in the Embolus group and six animals in the CPB-embolus group showed signs of ischemic penumbra on DW-MRI performed 6 h after surgery. Consistent with the results of DW-MRI, histopathological examination showed necrosis and ischemic lesions. In this paper, we demonstrate the feasibility and validity of a pig model of embolus-related cerebral injury associated with CPB. This model may be used in the future for basic and translational research.

Can Intraoperative Processed EEG Predict Postoperative Cognitive Dysfunction in the Elderly?

PURPOSE

Postoperative cognitive dysfunction (POCD) is a serious and costly complication of the elderly; even mild impairment has the potential to impact overall well being. Anesthesiologists continue to search for ways to manipulate intraoperative technique to optimize postoperative cognition in the elderly. Depth of anesthesia during surgery is an area that has shown some promise for short-term outcomes, such as delirium. However, excessive depth has both positive and negative associations with longer-term POCD. We hypothesize that this uncertainty is due to the inability of median depth to capture the amount of burst suppression or electrical silence. In this study, our purpose was to identify the intraoperative processed EEG parameters that are most closely correlated with POCD.

METHODS

To explore the association of several processed EEG parameters with POCD, we performed a retrospective analysis of a cohort of 105 patients aged >68 years scheduled for major surgery under general anesthesia. Intraoperative medications, hemodynamics, processed EEG and cerebral oxygen saturation were recorded. All patients had a cognitive battery before surgery and repeated at 3 months afterward.

FINDINGS

One hundred and five patients enrolled and 77 (73.3%) patients completed the 3-month cognitive testing. The incidence of POCD was 27%; the median Bispectral Index value for patients who developed POCD was similar to patients who did not (46 vs 42 minutes). However, patients who developed POCD spent less time with Bispectral Index <45 minutes (82.8 vs 122.5 minutes, P = 0.01) and burst suppression (35 vs 96 minutes, P = 0.04). Hypotension, cerebral desaturation, and use of total intravenous anesthesia were similar between patients with and without POCD.

IMPLICATIONS

Patients who developed POCD spent less time in EEG burst suppression and less time in deep states. Burst suppression may be protective for POCD. Further work is needed to definitively identify the role of burst suppression in the context of other patient and intraoperative variables to prevent POCD.

Biomarkers of Brain Damage and Postoperative Cognitive Disorders in Orthopedic Patients: An Update

The incidence of postoperative cognitive dysfunction (POCD) in orthopedic patients varies from 16% to 45%, although it can be as high as 72%. As a consequence, the hospitalization time of patients who developed POCD was longer, the outcome and quality of life were worsened, and prolonged medical and social assistance were necessary. In this review the short description of such biomarkers of brain damage as the S100B protein, NSE, GFAP, Tau protein, metalloproteinases, ubiquitin C terminal hydrolase, microtubule-associated protein, myelin basic protein, α-II spectrin breakdown products, and microRNA was made. The role of thromboembolic material in the development of cognitive decline was also discussed. Special attention was paid to optimization of surgical and anesthetic procedures in the prevention of postoperative cognitive decline.

The influence of anesthesia and pain management on cognitive dysfunction after joint arthroplasty: a systematic review

BACKGROUND

Despite the overall success of total joint arthroplasty, patients undergoing this procedure remain susceptible to cognitive decline and/or delirium, collectively termed postoperative cognitive dysfunction. However, no consensus exists as to whether general or regional anesthesia results in a lower likelihood that a patient may experience this complication, and controversy surrounds the role of pain management strategies to minimize the incidence of postoperative cognitive dysfunction.

QUESTIONS/PURPOSES

We systematically reviewed the English-language literature to assess the influence of the following anesthetic and/or pain management strategies on the risk for postoperative cognitive dysfunction in patients undergoing elective joint arthroplasty: (1) general versus regional anesthesia, (2) different parenteral, neuraxial, or inhaled agents within a given type of anesthetic (general or regional), (3) multimodal anesthetic techniques, and (4) different postoperative pain management regimens.

METHODS

A systematic search was performed of the MEDLINE(®) and EMBASE™ databases to identify all studies that assessed the influence of anesthetic and/or pain management strategies on the risk for postoperative cognitive dysfunction after elective joint arthroplasty. Twenty-eight studies were included in the final review, of which 21 (75%) were randomized controlled (Level I) trials, two (7%) were prospective comparative (Level II) studies, two (7%) used a case-control (Level III) design, and three (11%) used retrospective comparative (Level III) methodology.

RESULTS

The evidence published to date suggests that general anesthesia may be associated with increased risk of early postoperative cognitive dysfunction in the early postoperative period as compared to regional anesthesia, although this effect was not seen beyond 7 days. Optimization of depth of general anesthesia with comprehensive intraoperative cerebral monitoring may be beneficial, although evidence is equivocal. Multimodal anesthesia protocols have not been definitively demonstrated to reduce the incidence of postoperative cognitive dysfunction. Nonopioid postoperative pain management techniques, limiting narcotics to oral formulations and avoiding morphine, appear to reduce the risk of postoperative cognitive dysfunction.

CONCLUSIONS

Both anesthetic and pain management strategies appear to influence the risk of early cognitive dysfunction after elective joint arthroplasty, although only one study identified differences that persisted beyond 1 week after surgery. Investigators should strive to use accepted, validated tools for the assessment of postoperative cognitive dysfunction and to carefully report details of the anesthetic and analgesic techniques used in future studies.

Should general anaesthesia be avoided in the elderly?

Surgery and anaesthesia exert comparatively greater adverse effects on the elderly than on the younger brain, manifest by the higher prevalence of postoperative delirium and cognitive dysfunction. Postoperative delirium and cognitive dysfunction delay rehabilitation, and are associated with increases in morbidity and mortality among elderly surgical patients. We review the aetiology of postoperative delirium and cognitive dysfunction in the elderly with a particular focus on anaesthesia and sedation, discuss methods of diagnosing and monitoring postoperative cognitive decline, and describe the treatment strategies by which such decline may be prevented.

Anaesthetic neurotoxicity and neuroplasticity: an expert group report and statement based on the BJA Salzburg Seminar

Although previously considered entirely reversible, general anaesthesia is now being viewed as a potentially significant risk to cognitive performance at both extremes of age. A large body of preclinical as well as some retrospective clinical evidence suggest that exposure to general anaesthesia could be detrimental to cognitive development in young subjects, and might also contribute to accelerated cognitive decline in the elderly. A group of experts in anaesthetic neuropharmacology and neurotoxicity convened in Salzburg, Austria for the BJA Salzburg Seminar on Anaesthetic Neurotoxicity and Neuroplasticity. This focused workshop was sponsored by the British Journal of Anaesthesia to review and critically assess currently available evidence from animal and human studies, and to consider the direction of future research. It was concluded that mounting evidence from preclinical studies reveals general anaesthetics to be powerful modulators of neuronal development and function, which could contribute to detrimental behavioural outcomes. However, definitive clinical data remain elusive. Since general anaesthesia often cannot be avoided regardless of patient age, it is important to understand the complex mechanisms and effects involved in anaesthesia-induced neurotoxicity, and to develop strategies for avoiding or limiting potential brain injury through evidence-based approaches.

Intracisternal interleukin-1 receptor antagonist prevents postoperative cognitive decline and neuroinflammatory response in aged rats

To investigate the role of the pro-inflammatory cytokine interleukin-1β (IL-1β) in postoperative cognitive dysfunction (POCD) in aged rats, we used laparotomy to mimic human abdominal surgery in adult (3 months) and aged (24 months) F344/BN rats. We demonstrated that memory consolidation of the hippocampal-dependent contextual fear-conditioning task is significantly impaired in aged but not young rats 4 d after surgery. Hippocampal-independent auditory-cued fear memory was not disrupted by laparotomy in either age group. The hippocampal-dependent memory impairment was paralleled by elevations of IL-1β in the hippocampus of aged animals 1 and 4 d after surgery. These findings support our substantial line of previous research showing that aged animals are more vulnerable to cognitive decline after a peripheral immune challenge. In addition, we demonstrated that a single intracisternal administration of interleukin-1 receptor antagonist (IL-1RA; 112 μg) at the time of surgery was sufficient to block both the behavioral deficit and the neuroinflammatory response. Injecting the same dose of IL-1RA peripherally failed to have a protective effect. These data provide strong support for the specific role of central, not peripheral, IL-1β in POCD. Furthermore, the long-lasting presence of IL-1RA in the brain (4 d) compared with in the blood (<24 h) underscores the value of intracisternal administration of IL-1RA for therapeutic purposes.

Gender-specific differences in the central nervous system's response to anesthesia

Males and females are physiologically distinct in their responses to various anesthetic agents. The brain and central nervous system (CNS), the main target of anesthesia, are sexually dimorphic from birth and continue to differentiate throughout life. Accordingly, gender has a substantial impact on the influence of various anesthetic agents in the brain and CNS. Given the vast differences in the male and female CNS, it is surprising to find that females are often excluded from basic and clinical research studies of anesthesia. In animal research, males are typically studied to avoid the complication of breeding, pregnancy, and hormonal changes in females. In clinical studies, females are also excluded for the variations that occur in the reproductive cycle. Being that approximately half of the surgical population is female, the exclusion of females in anesthesia-related research studies leaves a huge knowledge gap in the literature. In this review, we examine the reported sex-specific differences in the central nervous system's response to anesthesia. Furthermore, we suggest that anesthesia researchers perform experiments on both sexes to further evaluate such differences. We believe a key goal of research studying the interaction of the brain and anesthesia should include the search for knowledge of sex-specific mechanisms that will improve anesthetic care and management in both sexes.

Neurologic complications of anesthesia

Neurologic complications after anesthesia are relatively uncommon but occasionally severe. Intraoperative intracranial hypertension in patients with brain masses, delayed arousal, and postoperative delirium and cognitive dysfunction are among the main complications of general anesthesia. Neuropathy and transient gluteal and leg pain are the most frequent complications of regional blockade. Seizures are infrequent with both anesthesia modalities. Patients with primary neurologic disorders, such as neurodegenerative or neuromuscular conditions, can be at risk for specific complications, and the anesthesia plan must be cautiously adjusted in these patients. In the neurointensive care unit, the complications from large doses of anesthetic agents used for suppression of seizures or control of intracranial pressure are different from those seen perioperatively. Propofol infusion syndrome can be life-threatening when administered for those indications.

Thinking through postoperative cognitive dysfunction: How to bridge the gap between clinical and pre-clinical perspectives

Following surgery, patients may experience cognitive decline, which can seriously reduce quality of life. This postoperative cognitive dysfunction (POCD) is mainly seen in the elderly and is thought to be mediated by surgery-induced inflammatory reactions. Clinical studies tend to define POCD as a persisting, generalised decline in cognition, without specifying which cognitive functions are impaired. Pre-clinical research mainly describes early hippocampal dysfunction as a consequence of surgery-induced neuroinflammation. These different approaches to study POCD impede translation between clinical and pre-clinical research outcomes and may hamper the development of appropriate interventions. This article analyses which cognitive domains deteriorate after surgery and which brain areas might be involved. The most important outcomes are: (1) POCD encompasses a wide range of cognitive impairments; (2) POCD affects larger areas of the brain; and (3) individual variation in the vulnerability of neuronal networks to neuroinflammatory mechanisms may determine if and how POCD manifests itself. We argue that, for pre-clinical and clinical research of POCD to advance, the effects of surgery on various cognitive functions and brain areas should be studied. Moreover, in addition to general characteristics, research should take inter-relationships between cognitive complaints and physical and mental characteristics into account.

Isoflurane causes neocortical but not hippocampal-dependent memory impairment in mice

BACKGROUND

The aim of this study is to investigate the effect of general anaesthesia induced by isoflurane with buprenorphine on hippocampus-dependent and neocortex-dependent memory, respectively, in mice, and in addition, to compare the effects of such anaesthesia on these memory processes with the effects induced by lipopolysaccharide (LPS) administration on the same memory processes.

METHODS

To assess hippocampus-dependent memory, isoflurane (for 15 min) after buprenorphine injection, or LPS 100 μg/kg (intraperitoneally) was administered 24 h before or after fear conditioning. The effect of these treatments on hippocampus-dependent memory was assessed using contextual fear-conditioning tasks at day 4. To assess neocortex-dependent memory, isoflurane anaesthesia or LPS was given 72 h after contextual fear conditioning. Neocortex-dependent memory assessment was performed at day 32.

RESULTS

Unlike LPS injection, isoflurane with buprenorphine-induced anaesthesia does not impair freezing responses in hippocampus-dependent fear-conditioning memory tasks. On anterograde amnesia assessment: 49.67 ± 6.87% for the anaesthesia group and 54.5 ± 4.12% for the control group. On retrograde amnesia assessment: 47.16 ± 8.71% for the anaesthesia group and 54.5 ± 4.12% for control group; P > 0.05. Thus, neither isoflurane nor buprenorphine impair hippocampus-dependent memory. However, on the neocortex-dependent memory task, both isoflurane-induced anaesthesia and LPS-induced inflammation result in reduced freezing responses: 62.13 ± 5.80% for the anaesthesia group, 74.63 ± 5.69% for the LPS group, and 81.75 ± 3.26% for the control group; P < 0.05 compared with control group.

CONCLUSION

General anaesthesia induced by isoflurane with buprenorphine may result in impairment of neocortex-dependent memory in mouse. However, general anaesthesia so induced does not impair hippocampus-dependent memory in mouse in our experimental conditions.

Can anaesthetic technique effect postoperative outcome?

PURPOSE OF REVIEW

Conventional wisdom maintains that multiple aspects of surgical technique and management may affect postoperative outcome, while anaesthetic technique has little long-term effect on patient outcomes. There is accumulating evidence that, on the contrary, anaesthetic management may in fact exert a number of longer-term effects in postoperative outcome. Here, we review the most topical aspects of anaesthetic management which may potentially influence later postoperative outcomes.

RECENT FINDINGS

There is strong evidence that administration of supplemental oxygen and the avoidance of perioperative hypothermia, allogeneic blood transfusion, hyperglycaemia or large swings in blood glucose levels reduces postoperative infection rates. There is also some evidence that the use of regional anaesthesia techniques reduces chronic postsurgical pain and that avoidance of nitrous oxide reduces the long-term risk of myocardial infarction. Current evidence is equivocal regarding the effects of anaesthesia techniques and cancer recurrence. The instigation of perioperative beta-blockade in noncardiac surgery may not reduce perioperative adverse events or improve postoperative cardiovascular risk.

SUMMARY

Further prospective, large-scale human trials with long-term follow-up are required to clarify the association between anaesthesia and cancer recurrence, neurotoxicity and the developing brain and long-term postoperative cognitive dysfunction in the elderly.

The role of continuous peripheral nerve blocks

A continuous peripheral nerve block (cPNB) is provided in the hospital and ambulatory setting. The most common use of CPNBs is in the peri- and postoperative period but different indications have been described like the treatment of chronic pain such as cancer-induced pain, complex regional pain syndrome or phantom limb pain. The documented benefits strongly depend on the analgesia quality and include decreasing baseline/dynamic pain, reducing additional analgesic requirements, decrease of postoperative joint inflammation and inflammatory markers, sleep disturbances and opioid-related side effects, increase of patient satisfaction and ambulation/functioning improvement, an accelerated resumption of passive joint range-of-motion, reducing time until discharge readiness, decrease in blood loss/blood transfusions, potential reduction of the incidence of postsurgical chronic pain and reduction of costs. Evidence deriving from randomized controlled trials suggests that in some situations there are also prolonged benefits of regional anesthesia after catheter removal in addition to the immediate postoperative effects. Unfortunately, there are only few data demonstrating benefits after catheter removal and the evidence of medium- or long-term improvements in health-related quality of life measures is still lacking. This review will give an overview of the advantages and adverse effects of cPNBs.

Can postoperative cognitive dysfunction be avoided?

Postoperative cognitive dysfunction (POCD) refers to a postoperative decline in cognitive function compared with preoperative cognitive function. Diagnosis requires pre- and postoperative testing, the latter of which is usually performed both 7 days and 3 months postoperatively. Although several risk factors for POCD have been described, age is the only consistently reported risk factor. Postoperative cognitive dysfunction is often transient. It may last several months, and is associated with leaving the labor market prematurely and increased mortality. As the pathophysiology of POCD is still a matter of debate and is likely to be multifactorial, there are no widely accepted prophylactic and therapeutic interventions. In this article, we discuss POCD's definition, risk factors, long-term significance, and pathophysiology. We also present data on prophylactic interventions that have been investigated in clinical trials.

Lidocaine attenuates cognitive impairment after isoflurane anesthesia in old rats

Post-operative cognitive dysfunction (POCD) is a clinical phenomenon that has drawn significant attention from the public and scientific community. Age is a risk factor for POCD. However, the contribution of general anesthesia/anesthetics to POCD and the underlying neuropathology are not clear. Here, we showed that 18-month-old male Fisher 344 rats exposed to 1.2% isoflurane, a general anesthetic, for 2h had significant learning and memory impairments assessed at 2-4 weeks after isoflurane exposure. These isoflurane effects were attenuated by intravenous lidocaine (1.5mg/kg as a bolus and then 2mg/kg/h during isoflurane exposure), a local anesthetic that has neuroprotective effect. Exposure to isoflurane or isoflurane plus lidocaine did not change the neuronal and synaptic density as well as the expression of NeuN (a neuronal protein), drebrin (a dendritic spine protein), synaptophysin (a synaptic protein), activated caspase 3 and caspase-activated DNase in the hippocampus at 29 days after isoflurane exposure when cognitive impairment was present. Isoflurane and lidocaine did not affect the amount of β-amyloid peptide, total tau and phospho-tau in the cerebral cortex as well as interleukin-1β and tumor necrosis factor-α in the hippocampus at 29 days after isoflurane exposure. Thus, isoflurane induces learning and memory impairment in old rats. Lidocaine attenuates these isoflurane effects. Isoflurane may not cause long-lasting neuropathological changes.

Heat shock protein 72 overexpression prevents early postoperative memory decline after orthopedic surgery under general anesthesia in mice

BACKGROUND

Problems with learning and memory are common after surgery in the elderly and are associated with high morbidity. Heat shock protein 72 (Hsp72) confers neuroprotection against acute neurologic injury. We hypothesized that overexpression of Hsp72 would prevent the development of postoperative memory loss.

METHODS

C57BL/6 wild-type and Hsp72 overexpressing transgenic mice were randomly allocated to the following: control, isoflurane anesthesia alone, or tibial fracture during isoflurane anesthesia. Animals were trained 24 h before surgery using a fear conditioning protocol and assessed in their training environment and in a novel context on posttreatment days 1, 3, and 7. Microglial activation was assessed by immunostaining.

RESULTS

Adult male C57BL/6 wild-type mice exhibited reduced memory evidenced by a decreased percentage freezing time on days 1 and 3 after anesthesia alone (58.8 ± 5, 46.5 ± 5 mean ± SEM) and after surgery (53.4 ± 6, 44.1 ± 7), compared with controls (78.8 ± 5, 63.4 ± 6; P < 0.05 and P < 0.001, respectively). Hsp72 mice showed no difference by treatment on any day. Similarly, nonhippocampal-dependent memory was significantly impaired on days 1 and 3 after surgery and day 3 after anesthesia. The genotype effect was significant on days 1 and 7. CD68-immunopositive activated microglia in the hippocampus varied modestly with subregion and time; on day 7, there was a significant treatment effect with no genotype effect, with more activated microglia after surgery in all regions.

CONCLUSION

Hsp72 overexpression is associated with prevention of postoperative hippocampal-dependent and -independent memory deficit induced by anesthesia and/or surgery. Memory deficit is not correlated with numbers of activated hippocampal microglia.

Iatrogenic risk factors for Alzheimer's disease: surgery and anesthesia

Increasing evidence indicates that patients develop post-operative cognitive decline (POCD) following surgery. POCD is characterized by transient short-term decline in cognitive ability evident in the early post-operative period. This initial decline might be associated with increased risk of a delayed cognitive decline associated with dementia 3 to 5 years post-surgery. In some studies, the conversion rates to dementia are up to 70% in patients who are 65 years or older. The factors responsible for the increased risk of dementia are unclear; however, clinical studies investigating the prevalence of POCD and dementia following surgery do not show an association with the type of anesthesia or duration of surgery. Epidemiological studies from our group support this observation. The adjusted Hazard Ratios for developing dementia (or AD specifically) after prostate or hernia surgery were 0.65 (95% CI, 0.51 to 0.83, prostate) and 0.65 (95% CI, 0.49 to 0.85, hernia) for cohorts of subjects exposed to general anesthesia compared to those exposed only to local anesthesia. Animal studies suggest that prolonged exposure to some volatile-inhalational anesthetics increase production of amyloid-β and vulnerability to neurodegeneration, but these results are weakened by the absence of clinical support. Inflammation and a maladaptive stress response might also contribute to the pathophysiology of this disorder. Future research needs to identify predisposing factors, and then strategies to protect against POCD and subsequent dementia. The field also needs to adopt a more rigorous approach to codifying the frequency and extent of early and delayed post-operative cognitive decline.

Brief review: anesthetic neurotoxicity in the elderly, cognitive dysfunction and Alzheimer's disease

PURPOSE

Postoperative cognitive decline in the elderly has emerged as a major health concern. In addition, there is a growing interest in the potential relationship between general anesthetic exposure and the onset and progression of Alzheimer's disease (AD). The available evidence of a possible association between anesthesia, surgery, and long-term cognitive effects, including AD, deserves consideration. In this review, we summarize the evidence for anesthesia-induced neurotoxicity in the elderly, while highlighting the limitations of existing data, and we put the literature into perspective for the clinician.

PRINCIPAL FINDINGS

A growing body of evidence suggests that general anesthetics may be neurotoxic to both young and aging brains. Much of the evidence originates from in vitro and in vivo studies with cells, rodents, and nonhuman primates. Despite the animal data suggesting a relationship between anesthesia and neurotoxicity in the elderly, a definitive link remains elusive in humans.

CONCLUSIONS

The possible relation between anesthetic neurotoxicity, postoperative cognitive dysfunction, and AD remains elusive. It remains unclear whether postoperative cognitive decline in the elderly is related more to perioperative stress and related medical co-morbidities.