Effects of Dexamethasone on Cognitive Decline after Cardiac Surgery

The Role of Neuroinflammation in Postoperative Cognitive Dysfunction: Moving From Hypothesis to Treatment

Postoperative cognitive dysfunction (POCD) is a common complication of the surgical experience and is common in the elderly and patients with preexisting neurocognitive disorders. Animal and human studies suggest that neuroinflammation from either surgery or anesthesia is a major contributor to the development of POCD. Moreover, a large and growing body of literature has focused on identifying potential risk factors for the development of POCD, as well as identifying candidate treatments based on the neuroinflammatory hypothesis. However, variability in animal models and clinical cohorts makes it difficult to interpret the results of such studies, and represents a barrier for the development of treatment options for POCD. Here, we present a broad topical review of the literature supporting the role of neuroinflammation in POCD. We provide an overview of the cellular and molecular mechanisms underlying the pathogenesis of POCD from pre-clinical and human studies. We offer a brief discussion of the ongoing debate on the root cause of POCD. We conclude with a list of current and hypothesized treatments for POCD, with a focus on recent and current human randomized clinical trials.

Neurocognitive Adverse Effects of Anesthesia in Adults and Children: Gaps in Knowledge

Numerous preclinical and clinical studies investigating the neurodevelopmental and neurocognitive effects of exposure to anesthesia and the combination of anesthesia and surgery have demonstrated histopathological and both temporary and long-term cognitive and behavioral effects at the extremes of the human age spectrum. Increasing coverage in the lay press for both our youngest and oldest patient populations has led to heightened concerns regarding the potential harmful side effects of almost all commonly used anesthetic drug regimens. Although the majority of information regarding anesthetic risks in the developing brain derives from preclinical work in rodents, research involving the aged brain has identified a well-defined postoperative cognitive phenotype in humans. While preclinical and clinical data appear to support some association between anesthesia and surgery and the development of detrimental cognitive changes in both the developing and the aged brain, correlation between anesthesia and surgery and poor neurological outcomes does not imply causation. Given this information, no single anesthetic or group of anesthetics can be recommended over any other in terms of causing or preventing negative neurocognitive outcomes in either population. This review summarizes the growing body of preclinical and clinical literature dedicated to the detrimental effects of anesthesia on both the developing and the aging brain.

Neurological outcome after minimal invasive coronary artery surgery (NOMICS): protocol for an observational prospective cohort study

INTRODUCTION

Adverse neurocognitive outcomes are still an important cause of morbidity and mortality after cardiac surgery. The most common neurocognitive disorders after conventional cardiac surgery are postoperative cognitive dysfunction (POCD), stroke and delirium. Minimal invasive cardiac procedures have recently been introduced into practice. Endoscopic coronary artery bypass grafting (Endo-CABG) is a minimal invasive cardiac procedure based on the conventional CABG procedure. Neurocognitive outcome after minimal invasive cardiac surgery, including Endo-CABG, has never been studied. Therefore, the main objective of this study is to examine neurocognitive outcome after Endo-CABG.

METHODS AND ANALYSIS

We will perform a prospective observational cohort study including 150 patients. Patients are categorised into three groups: (1) patients undergoing Endo-CABG, (2) patients undergoing a percutaneous coronary intervention and (3) a healthy volunteer group. All patients in the Endo-CABG group will be treated following a uniform, standardised protocol. To assess neurocognitive outcome after surgery, a battery of six neurocognitive tests will be administered at baseline and at 3-month follow-up. In the Endo-CABG group, a neurological examination will be performed at baseline and postoperatively and delirium will be scored at the intensive care unit. Quality of life (QOL), anxiety and depression will be assessed at baseline and at 3-month follow-up. Satisfaction with Endo-CABG will be assessed at 3-month follow-up. Primary endpoints are the incidence of POCD, stroke and delirium after Endo-CABG. Secondary endpoints are QOL after Endo-CABG, patient satisfaction with Endo-CABG and the incidence of anxiety and depression after Endo-CABG.

ETHICS AND DISSEMINATION

The neurological outcome after minimal invasive coronary artery surgery study has received approval of the Jessa Hospital ethics board. It is estimated that the trial will be executed from December 2016 to January 2018, including enrolment and follow-up. Analysis of data, followed by publication of the results, is expected in 2018.

TRIAL REGISTRATION NUMBER

NCT02979782.

Influence of the postoperative inflammatory response on cognitive decline in elderly patients undergoing on-pump cardiac surgery: a controlled, prospective observational study

Background

The role of non-infective inflammatory response (IR) in the aetiology of postoperative cognitive dysfunction (POCD) is still controversial. The aim of this controlled, prospective observational study was to assess the possible relationship between the grade of IR, defined by procalcitonin (PCT) changes, and development of POCD related to cardiac surgery.

Methods

Forty-two patients, who were ≥ 60 years of age and scheduled for elective cardiac surgery, were separated into the low inflammatory (LIR) and high inflammatory (HIR) response groups based on their PCT levels measured on the first postoperative day. A matched normative control group of 32 subjects was recruited from primary care practice. The PCT and C-reactive protein (CRP) levels were monitored daily during the first five postoperative days. The cognitive function and mood state were preoperatively tested with a set of five neurocognitive tests and two mood inventories and at the seventh postoperative day. The Reliable Change Index modified for practice (RCIp) using data from normative controls was applied to determine the significant decline in test performance.

Results

The LIR (n = 20) and HIR (n = 22) groups differed significantly in the PCT (p < 0.001) but not in the CRP time courses. The incidence of POCD at the first postoperative week was 35.7% in the cohort. The LIR and HIR groups did not vary in the RCIp Z scores of neurocognitive tests and frequencies of POCD (7 vs 8 cases, respectively, p > 0.05). Additionally, there was no difference in the mood states, anxiety levels and perioperative parameters known to influence the development of POCD.

Conclusions

In this study, the magnitude of the non-infective inflammatory response generated by on-pump cardiac surgery did not influence the development of POCD in the early postoperative period in elderly patients.

Surgery and Anesthesia Exposure Is Not a Risk Factor for Cognitive Impairment After Major Noncardiac Surgery and Critical Illness

OBJECTIVE

The aim of this study was to determine whether surgery and anesthesia exposure is an independent risk factor for cognitive impairment after major noncardiac surgery associated with critical illness.

SUMMARY OF BACKGROUND DATA

Postoperative cognitive impairment is a prevalent individual and public health problem. Data are inconclusive as to whether this impairment is attributable to surgery and anesthesia exposure versus patients' baseline factors and hospital course.

METHODS

In a multicenter prospective cohort study, we enrolled ICU patients with major noncardiac surgery during hospital admission and with nonsurgical medical illness. At 3 and 12 months, we assessed survivors' global cognitive function with the Repeatable Battery for the Assessment of Neuropsychological Status and executive function with the Trail Making Test, Part B. We performed multivariable linear regression to study the independent association of surgery/anesthesia exposure with cognitive outcomes, adjusting initially for baseline covariates and subsequently for in-hospital covariates.

RESULTS

We enrolled 1040 patients, 402 (39%) with surgery/anesthesia exposure. Median global cognition scores were similar in patients with surgery/anesthesia exposure compared with those without exposure at 3 months (79 vs 80) and 12 months (82 vs 82). Median executive function scores were also similar at 3 months (41 vs 40) and 12 months (43 vs 42). Surgery/anesthesia exposure was not associated with worse global cognition or executive function at 3 or 12 months in models incorporating baseline or in-hospital covariates (P > 0.2). Higher baseline education level was associated with better global cognition at 3 and 12 months (P < 0.001), and longer in-hospital delirium duration was associated with worse global cognition (P < 0.02) and executive function (P < 0.01) at 3 and 12 months.

CONCLUSIONS

Cognitive impairment after major noncardiac surgery and critical illness is not associated with the surgery and anesthesia exposure but is predicted by baseline education level and in-hospital delirium.

Cognitive decline associated with anesthesia and surgery in the elderly: does this contribute to dementia prevalence?

PURPOSE OF REVIEW

To provide an update on the current state of research investigating the effects of anesthesia and surgery on cognition in the elderly, including consideration of overlap with cognitive disorders in the community.

RECENT FINDINGS

The studies reviewed here identify detrimental effects of anesthesia and surgery on cognition in a proportion of elderly individuals. Animal models demonstrate an association between anesthetic agents and Alzheimer's disease pathology. Human studies demonstrate a high incidence of cognitive impairment preoperatively in the elderly and further decline postoperatively, with recent work showing that poor preoperative cognitive function is a key predictor for further postoperative decline. Results from retrospective studies into an association between Alzheimer's disease and prior anesthesia and surgery are equivocal, but there are some data to suggest an association with accelerated cognitive decline in the long term. Postoperative delirium is common and even in individuals with normal preoperative cognition is associated with long-term decline.

SUMMARY

Cognitive impairment in the elderly ultimately leads to a decline in function with high personal and societal costs. Following anesthesia and surgery, decline in cognition is observed in some individuals, which may represent vulnerability for future decline or may alter their cognitive trajectory. Recent work suggests factors that impact this decline and/or impair recovery include higher risk patients and subtle cognitive impairment preoperatively. Identifying these individuals is critical to determining opportunities for intervention and preventive strategies, and ultimately reducing the impact on functional decline. It remains unclear if anesthesia and surgery play a role in the onset or progression of mild cognitive impairment and dementia across the community. Recent work showing that preoperative impairment is a significant risk factor for decline indicates that routinely assessing cognition preoperatively would allow improved management including referral pathways for patients at risk, delirium prevention, specifically optimizing care and consideration of treatment options.

Impact of Methylprednisolone on Postoperative Quality of Recovery and Delirium in the Steroids in Cardiac Surgery Trial

Background

Inflammation after cardiopulmonary bypass may contribute to postoperative delirium and cognitive dysfunction. The authors evaluated the effect of high-dose methylprednisolone to suppress inflammation on the incidence of delirium and postoperative quality of recovery after cardiac surgery.

Methods

Five hundred fifty-five adults from three hospitals enrolled in the randomized, double-blind Steroids in Cardiac Surgery trial were randomly allocated to placebo or 250 mg methylprednisolone at induction and 250 mg methylprednisolone before cardiopulmonary bypass. Each completed the Postoperative Quality of Recovery Scale before surgery and on days 1, 2, and 3 and 1 and 6 months after surgery and the Confusion Assessment Method scale for delirium on days 1, 2, and 3. Recovery was defined as returning to preoperative values or improvement at each time point.

Results

Four hundred eighty-two participants for recovery and 498 participants for delirium were available for analysis. The quality of recovery improved over time but without differences between groups in the primary endpoint of overall recovery (odds ratio range over individual time points for methylprednisolone, 0.39 to 1.45; 95% CI, 0.08–2.04 to 0.40–5.27; P = 0.943) or individual recovery domains (all P &gt; 0.05). The incidence of delirium was 10% (control) versus 8% (methylprednisolone; P = 0.357), with no differences in delirium subdomains (all P &gt; 0.05). In participants with normal (51%) and low baseline cognition (49%), there were no significant differences favoring methylprednisolone in any domain (all P &gt; 0.05). Recovery was worse in patients with postoperative delirium in the cognitive (P = 0.004) and physiologic (P &lt; 0.001) domains.

Conclusions

High-dose intraoperative methylprednisolone neither reduces delirium nor improves the quality of recovery in high-risk cardiac surgical patients.

Enhanced neuroinflammation mediated by DNA methylation of the glucocorticoid receptor triggers cognitive dysfunction after sevoflurane anesthesia in adult rats subjected to maternal separation during the neonatal period

BACKGROUND

Mounting evidence indicates that children who experience abuse and neglect are prone to chronic diseases and premature mortality later in life. One mechanistic hypothesis for this phenomenon is that early life adversity alters the expression or functioning of the glucocorticoid receptor (GR) throughout the course of life and thereby increases sensitivity to inflammatory stimulation. An exaggerated pro-inflammatory response is generally considered to be a key cause of postoperative cognitive dysfunction (POCD). The aim of this study was to examine the effects of early life adversity on cognitive function and neuroinflammation after sevoflurane anesthesia in adult rats and to determine whether such effects are associated with the epigenetic regulation of GR.

METHODS

Wistar rat pups were repeatedly subjected to infant maternal separation (early life stress) from postnatal days 2-21. In adulthood, their behavior and the signaling of hippocampal pro-inflammatory factors and nuclear factor-kappa B (NF-κB) after sevoflurane anesthesia were evaluated. We also examined the effects of maternal separation (MS) on the expression of GR and the DNA methylation status of the promoter region of exon 1₇ of GR and whether behavioral changes and neuroinflammation after anesthesia were reversible when the expression of GR was increased by altering DNA methylation.

RESULTS

MS induced cognitive decline after sevoflurane inhalation in the Morris water maze and context fear conditioning tests and enhanced the release of cytokines and the activation of astrocyte intracellular NF-κB signaling induced by sevoflurane in the hippocampus of adult rats. Blocking NF-κB signaling by pyrrolidine dithiocarbamate (PDTC) inhibited the release of cytokines. MS also reduced the expression of GR and upregulated the methylation levels of the promoter region of GR exon 1₇, and such effects were reversed by treatment with the histone deacetylase inhibitor trichostatin A (TSA) in adult rats. Moreover, TSA treatment in adult MS rats inhibited the overactivation of astrocyte intracellular NF-κB signaling and the release of cytokines and alleviated cognitive dysfunction after sevoflurane anesthesia.

CONCLUSIONS

Early life stress induces cognitive dysfunction after sevoflurane anesthesia, perhaps due to the aberrant methylation of the GR gene promoter, which reduces the expression of the GR gene and facilitates exaggerated inflammatory responses.

Basics of cardiopulmonary bypass

Cardiopulmonary bypass (CPB) provides a bloodless field for cardiac surgery. It incorporates an extracorporeal circuit to provide physiological support in which venous blood is drained to a reservoir, oxygenated and sent back to the body using a pump. Team effort between surgeon, perfusionist and anaesthesiologist is paramount for the successful use of CPB. However, it also has its share of complications and strategies to reduce these complications are the area of the current research.

Deferoxamine regulates neuroinflammation and iron homeostasis in a mouse model of postoperative cognitive dysfunction

BACKGROUND

Postoperative cognitive dysfunction (POCD) is a common complication after surgery, especially amongst elderly patients. Neuroinflammation and iron homeostasis are key hallmarks of several neurological disorders. In this study, we investigated the role of deferoxamine (DFO), a clinically used iron chelator, in a mouse model of surgery-induced cognitive dysfunction and assessed its neuroprotective effects on neuroinflammation, oxidative stress, and memory function.

METHODS

A model of laparotomy under general anesthesia and analgesia was used to study POCD. Twelve to 14 months C57BL/6J male mice were treated with DFO, and changes in iron signaling, microglia activity, oxidative stress, inflammatory cytokines, and neurotrophic factors were assessed in the hippocampus on postoperative days 3, 7, and 14. Memory function was evaluated using fear conditioning and Morris water maze tests. BV2 microglia cells were used to test the anti-inflammatory and neuroprotective effects of DFO.

RESULTS

Peripheral surgical trauma triggered changes in hippocampal iron homeostasis including ferric iron deposition, increase in hepcidin and divalent metal transporter-1, reduction in ferroportin and ferritin, and oxidative stress. Microglia activation, inflammatory cytokines, brain-derived neurotropic factor impairments, and cognitive dysfunction were found up to day 14 after surgery. Treatment with DFO significantly reduced neuroinflammation and improved cognitive decline by modulating p38 MAPK signaling, reactive oxygen species, and pro-inflammatory cytokines release.

CONCLUSIONS

Iron imbalance represents a novel mechanism underlying surgery-induced neuroinflammation and cognitive decline. DFO treatment regulates neuroinflammation and microglia activity after surgery.

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

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

The Association of Brain MRI Characteristics and Postoperative Delirium in Cardiac Surgery Patients

PURPOSE

Delirium is common after cardiac surgery and is associated with adverse consequences, including cognitive decline. Identification of vulnerable older adults might allow for early implementation of delirium-prevention strategies. Brain MRI findings provide insight into structural brain changes that may identify vulnerable patients. The purpose of this study was to examine the association between brain MRI characteristics potentially associated with delirium vulnerability and the development of postoperative delirium in a nested cohort of patients undergoing cardiac surgery.

METHODS

We identified 79 cardiac surgery patients who had brain MRI imaging after cardiac surgery, as part of an ongoing randomized trial evaluating the efficacy of blood pressure management based on cerebral autoregulation monitoring versus standard management for improving neurological outcomes. Cerebral lateral ventricular size, cortical sulcal width, and white matter hyperintensities (WMH) on brain MRI scans were graded on a validated 0 to 9 scale, and categorized into tertiles. New ischemic lesions were characterized as present or absent. Delirium was assessed using a validated chart-review. Neuropsychological testing performed before surgery was used to establish preoperative cognitive baseline. Multivariable logistic regression was used to assess the independent association between MRI characteristics and postoperative delirium.

FINDINGS

The average age of patients was 70.1 ± 7.8 years old, and 72% were male. Twenty-eight of 79 (35.4%) patients developed postoperative delirium. Patients with delirium had higher unadjusted ventricular size (median 4 vs. 3, P = 0.003), and there was a trend towards higher sulcal sizes and WMH grades. Increasing tertiles of ventricular size (Odds Ratio [OR] 3.59; 95% Confidence Interval [CI] 1.59-8.12; P = 0.002) and sulcal size (OR 2.15; 95%CI 1.13-4.12; P = 0.02) were associated with postoperative delirium, with a trend for tertiles of WMH grade (OR 1.91; 95%CI 0.99-3.68; P = 0.05). In multivariable models adjusted for logistic EuroSCORE, baseline cognitive status, bypass time, and any postoperative complication, each tertile of ventricular size was associated with increased odds of postoperative delirium (OR 3.23 per tertile increase in ventricular size; 95%CI 1.21-8.60; P = 0.02). There were no differences in odds of delirium by tertiles of sulcal grade, tertiles of white matter grade, or presence of new ischemic lesions, in adjusted models.

IMPLICATIONS

Increased brain ventricular size was independently associated with delirium after cardiac surgery. These results suggest that cerebral atrophy may contribute to increased vulnerability for postoperative delirium. Baseline brain MRIs may be useful in identifying cardiac surgery patients at high risk for postoperative delirium, who might benefit from targeted perioperative approaches to prevent delirium. ClinicalTrials.gov identifier: NCT00981474.

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

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