Cognitive deficits following coronary artery bypass grafting: prevalence, prognosis, and therapeutic strategies

Progress in the correlation of postoperative cognitive dysfunction and Alzheimer's disease and the potential therapeutic drug exploration

Postoperative cognitive dysfunction (POCD) is a decrease in mental capacity that can occur days to weeks after a medical procedure and may become permanent and rarely lasts for a longer period of time. With the continuous development of research, various viewpoints in academic circles have undergone subtle changes, and the role of anesthesia depth and anesthesia type seems to be gradually weakened; Alzheimer's disease (AD) is a latent and progressive neurodegenerative disease in the elderly. The protein hypothesis and the synaptic hypothesis are well-known reasons. These changes will also lead to the occurrence of an inflammatory cascade. The exact etiology and pathogenesis need to be studied. The reasonable biological mechanism affecting brain protein deposition, neuroinflammation, and acetylcholine-like effect has a certain relationship between AD and POCD. Whereas there is still further uncertainty about the mechanism and treatment, and it is elusive whether POCD is a link in the continuous progress of AD or a separate entity, which has doubts about the diagnosis and treatment of the disease. Therefore, this review is based on the current common clinical characteristics of AD and POCD, and pathophysiological research, to search for their common points and explore the direction and new strategies for future treatment.

The risk of dementia after coronary artery bypass grafting in relation to age and sex

Introduction

We examined the long‐term risk of dementia after coronary artery bypass grafting (CABG) in relation to age and sex.

Methods

All CABG patients in Sweden 1992–2015 (n = 111,335), and matched controls (n = 222,396) were included in a population‐based study. Adjusted hazard ratios (aHR) for all‐cause dementia, vascular dementia, and Alzheimer's disease were calculated.

Results

There was no difference in the risk for all‐cause dementia between CABG patients and control subjects (aHR 0.98 [95% confidence interval 0.95 to 1.02]). CABG patients <65 years and 65 to 74 years had higher risk (aHR 1.29 [1.17–1.42] and 1.08 [1.02–1.13], respectively), and patients ≥75 years had lower risk (aHR 0.76 [0.71–0.81]). The highest risk was observed in women <65 years (aHR 1.64 [1.31–2.05]).

Discussion

Overall, the long‐term risk for all‐cause dementia does not differ between CABG patients and the general population. Younger patients have a higher risk, while older patients have a lower risk, compared to controls.

Assessment of adrenal reserve and secretion of cortisol in patients over 60 years of age undergoing cardiac surgery

Introduction

Cortisol level affects the prognosis of patients after cardiac surgery. Meanwhile, there are no clear guidelines for steroid supplementation after a cardiac operation. The relationship between age and blood cortisol levels has not been finally clarified.

Aim

Assessment of adrenal reserve and secretion of cortisol in patients over 60 years of age undergoing cardiac surgery.

Material and methods

The study included 20 patients of both sexes referred for cardiac surgery. A short ACTH synthetic stimulation test was carried out. Assessment of cortisol secretion was carried out in the morning on the day of surgery and the 1^st, 2^nd and 4^th days after surgery in blood samples.

Results

A result within the normal range for the adrenal reserve was found in 19 of the 20 patients enrolled in the study. The short Synacthen test predicted postoperative secretion of cortisol (p = 0.04, r = 0.047). A relationship between secretion of cortisol and patients’ age was observed (p = 0.03, r = 0.48). The concentration of cortisol on the 1^st postoperative day was correlated with the total dose of dopamine (p = 0.006, r = 0.58) and adrenaline (p = 0.04, r = 0.47). The concentration of cortisol on the day of the surgery correlated with the lactate concentration on day 2 (p = 0.04, r = 0.45). The concentration of lactates on day 1 correlated with total dose of dopamine (p = 0.01, r = 0.54).

Conclusions

A short Synacthen test allows one to predict secretion of cortisol after cardiac surgery. Greater secretion of cortisol after cardiac surgery may be associated with a more difficult postoperative course. There was no decrease in cortisol secretion with age.

Postoperative Cognitive Dysfunction after Coronary Artery Bypass Grafting

Postoperative cognitive dysfunction is a common complication following cardiac surgery. The incidence of cognitive dysfunction is more pronounced in patients receiving a cardiac operation than in those undergoing a non-cardiac operation. Clinical observations demonstrated that pulsatile flow was superior to nonpulsatile flow, and membrane oxygenator was superior to bubble oxygenator in terms of postoperative cognitive status. Nevertheless, cognitive assessments in patients receiving an on-pump and off-pump coronary artery bypass surgery have yielded inconsistent results. The exact mechanisms of postoperative cognitive dysfunction following coronary artery bypass grafting remain uncertain. The dual effects, neuroprotective and neurotoxic, of anesthetics should be thoroughly investigated. The diagnosis should be based on a comprehensive cognitive evaluation with neuropsychiatric tests, cerebral biomarker inspections, and electroencephalographic examination. The management strategies for cognitive dysfunction can be preventive or therapeutic. The preventive strategies of modifying surgical facilities and techniques can be effective for preventing the development of postoperative cognitive dysfunction. Investigational therapies may offer novel strategies of treatments. Anesthetic preconditioning might be helpful for the improvement of this dysfunction.

Longitudinal Changes in Regional Cerebral Perfusion and Cognition After Cardiac Operation

BACKGROUND

Cardiac operation has been associated with increased risk of postoperative cognitive decline, as well as dementia risk in the general population. Few studies, however, have examined the impact of coronary revascularization or valve replacement or repair operation on longitudinal cerebral perfusion changes or their association with cognitive function.

METHODS

We examined longitudinal changes in cerebral perfusion among 54 individuals with cardiac disease; 27 undergoing cardiac operation and 27 matched control patients. Arterial spin labeling magnetic resonance perfusion imaging was used to quantify cerebral blood flow within the anterior communicating artery, middle cerebral artery (MCA), and posterior communicating artery vascular territories before operation and postoperatively at 6 weeks and 1 year. Cognitive performance was examined during the same intervals by using a battery of tests that tapped memory, executive, information processing and upper extremity motor functions. Repeated measures, mixed models were used to examine for perfusion changes and the association between perfusion changes and cognition.

RESULTS

Significant postoperative increases in perfusion were observed at 6 weeks within the MCA vascular territory after cardiac operation (p = 0.035 for interaction). Perfusion changes were most notable in distal territories of the MCA and posterior communicating artery at 6 weeks, with no additional changes at 1 year. Postoperative increases in MCA perfusion at 6 weeks were associated with improved psychomotor speed (β = 0.35, p = 0.016), whereas no important differences were found between the groups in vascular territory perfusion and cognition at 1 year.

CONCLUSIONS

Cardiac operation is associated with important short-term increases in MCA perfusion with associated improvements in psychomotor speed.

Impact of cognitive performance on disease-related knowledge six months after multi-component rehabilitation in patients after an acute cardiac event

Background

Although associations between cardiovascular diseases and cognitive impairment are well known, the impact of cognitive performance on the success of patient education as a core component of cardiac rehabilitation remains insufficiently investigated so far.

Design

Prospective observational study in two inpatient cardiac rehabilitation centres between September 2014 and August 2015 with a follow-up six months after cardiac rehabilitation.

Method

At admission to and discharge from cardiac rehabilitation, the cognitive performance of 401 patients (54.5 ± 6.3 years, 80% men) following an acute coronary syndrome and/or coronary artery bypass graft was tested using the Montreal Cognitive Assessment. Patients’ disease-related knowledge was determined using a quiz (22 items for medical knowledge and 12 items for healthy lifestyle and behaviour) at both times and at follow-up. The change in knowledge after cardiac rehabilitation was analysed in multivariable regression models. Potentially influencing parameters (e.g. level of education, medication, cardiovascular risk factors, coronary artery bypass graft, comorbidities, exercise capacity) were considered.

Results

During cardiac rehabilitation, disease-related knowledge was significantly enhanced in both scales. At follow-up, the average level of medical knowledge was significantly reduced, while lifestyle knowledge remained at a stable level. The maintenance of knowledge after cardiac rehabilitation was predominantly predicted by prior knowledge, cognitive performance at discharge from cardiac rehabilitation and, in the case of medical knowledge, by coronary artery bypass graft.

Conclusion

Patient education in cardiac rehabilitation led to enhanced disease-related knowledge, but the maintenance of this essentially depended on patients’ cognitive performance, especially after coronary artery bypass graft. Therefore, patient education concepts in cardiac rehabilitation should be reconsidered and adjusted as needed.

Inflammatory markers in postoperative delirium (POD) and cognitive dysfunction (POCD): A meta-analysis of observational studies

Background

The aim of this study was to summarize and discuss the similarities and differences in inflammatory biomarkers in postoperative delirium (POD) and cognitive dysfunction (POCD).

Methods

A systematic retrieval of literature up to June 2017 in PubMed, Embase, the Cochrane Library, the China National Knowledge Infrastructure database, and the Wanfang database was conducted. Extracted data were analyzed with STATA (version 14). The standardized mean difference (SMD) and the 95% confidence interval (95% CI) of each indicator were calculated using a random effect model. We also performed tests of heterogeneity, sensitivity analysis, assessments of bias, and meta-regression in this meta-analysis.

Results

A total of 54 observational studies were included. By meta-analysis we found significantly increased C-reactive protein (CRP) (9 studies, SMD 0.883, 95% CI 0.130 to 1.637, P = 0.022 in POD; 10 studies, SMD -0.133, 95% CI -0.512 to 0.246, P = 0.429 in POCD) and interleukin (IL)-6 (7 studies, SMD 0.386, 95% CI 0.054 to 0.717, P = 0.022 in POD; 16 studies, SMD 0.089, 95% CI -0.133 to 0.311, P = 0.433 in POCD) concentrations in both POD and POCD patients. We also found that the SMDs of CRP and IL-6 from POCD patients were positively correlated with surgery type in the meta-regression (CRP: Coefficient = 1.555365, P = 0.001, 10 studies; IL-6: Coefficient = -0.6455521, P = 0.086, 16 studies).

Conclusion

Available evidence from medium-to-high quality observational studies suggests that POD and POCD are indeed correlated with the concentration of peripheral and cerebrospinal fluid (CSF) inflammatory markers. Some of these markers, such as CRP and IL-6, play roles in both POD and POCD, while others are specific to either one of them.

Subcortical hyperintensities in the cholinergic system are associated with improvements in executive function in older adults with coronary artery disease undergoing cardiac rehabilitation

OBJECTIVE

Coronary artery disease (CAD) is frequently accompanied by white matter hyperintensities and executive dysfunction. Because acetylcholine is important in executive function, these symptoms may be exacerbated by subcortical hyperintensities (SH) located in cholinergic (CH) tracts. This study investigated the effects of SH on cognitive changes in CAD patients undergoing a 48-week cardiac rehabilitation program.

METHODS

Fifty patients (age 66.5 ± 7.1 years, 84% male) underwent the National Institute of Neurological Disorders and Stroke - Canadian Stroke Network neurocognitive battery at baseline and 48 weeks. Patients underwent a 48-week cardiac program and completed neuroimaging at baseline. Subcortical hyperintensities in CH tracts were measured using Lesion Explorer. Repeated measures general linear models were used to examine interactions between SH and longitudinal cognitive outcomes, controlling for age, education, and max VO₂ change as a measure of fitness.

RESULTS

In patients with SH in CH tracts, there was a significant interaction with the Trail Making Test (TMT) part A and part B over time. Patients without SH improved on average 16.6 and 15.0% on the TMT-A and TMT-B, respectively. Patients with SH on average showed no improvements in either TMT-A or TMT-B over time. There were no significant differences in other cognitive measures.

CONCLUSION

These results suggest that CAD patients with SH in CH tracts improve less than those without SH in CH tracts, over 48 weeks of cardiac rehabilitation. Thus, SH in CH tracts may contribute to longitudinal cognitive decline following a cardiac event and may represent a vascular risk factor of cognitive decline. © 2017 The Authors. International Journal of Geriatric Psychiatry Published by John Wiley & Sons Ltd.

Task-related changes in degree centrality and local coherence of the posterior cingulate cortex after major cardiac surgery in older adults

OBJECTIVES

Older adults often display postoperative cognitive decline (POCD) after surgery, yet it is unclear to what extent functional connectivity (FC) alterations may underlie these deficits. We examined for postoperative voxel-wise FC changes in response to increased working memory load demands in cardiac surgery patients and nonsurgical controls.

EXPERIMENTAL DESIGN

Older cardiac surgery patients (n = 25) completed a verbal N-back working memory task during MRI scanning and cognitive testing before and 6 weeks after surgery; nonsurgical controls with cardiac disease (n = 26) underwent these assessments at identical time intervals. We measured postoperative changes in degree centrality, the number of edges attached to a brain node, and local coherence, the temporal homogeneity of regional functional correlations, using voxel-wise graph theory-based FC metrics. Group × time differences were evaluated in these FC metrics associated with increased N-back working memory load (2-back > 1-back), using a two-stage partitioned variance, mixed ANCOVA.

PRINCIPAL OBSERVATIONS

Cardiac surgery patients demonstrated postoperative working memory load-related degree centrality increases in the left dorsal posterior cingulate cortex (dPCC; p < .001, cluster p-FWE < .05). The dPCC also showed a postoperative increase in working memory load-associated local coherence (p < .001, cluster p-FWE < .05). dPCC degree centrality and local coherence increases were inversely associated with global cognitive change in surgery patients (p < .01), but not in controls.

CONCLUSIONS

Cardiac surgery patients showed postoperative increases in working memory load-associated degree centrality and local coherence of the dPCC that were inversely associated with postoperative global cognitive outcomes and independent of perioperative cerebrovascular damage.

Prevention of Coagulum Formation With Simultaneous Charge Delivery in Radiofrequency Ablation: A Canine Model

OBJECTIVES

This study reports on a novel method to prevent coagulum formation by continuously delivering a negative charge to the catheter tip to repel negatively charged fibrinogen molecules during RF ablation.

BACKGROUND

Radiofrequency (RF) ablation for cardiac arrhythmias is associated with a 70% incidence of coagulum formation on the catheter tip during ablation and a 10% incidence of thromboembolic events. Catheter tip thrombus can impede RF energy to the tissue, reducing efficacy and increasing procedure times.

METHODS

A novel circuit was built to deliver a negative, fixed-offset, direct current-based charge using a 9-V battery, placed in parallel with an RF delivery unit during RF ablation. In in vivo canine experiments, standard ablation catheters were advanced into atria and ventricles under fluoroscopic guidance. The presence of thrombus with and without RF delivery was identified with intracardiac echocardiography.

RESULTS

Scanning electron microscopy of the catheter tips showed clot coverage of the catheter tip to be 90% for noncharged catheters compared to 0% (p < 0.01) in negatively charged catheters. Volume of clot formed on the catheter tip decreased with increased amount of charge (140 ± 5.3 arbitrary units with no charge vs. 0 arbitrary units with a 100-μA current delivering negative charge, p < 0.01). Application of a negative charge did not affect the quality of the intracardiac electrogram or induce malignant ventricular arrhythmias.

CONCLUSIONS

Negative-charge delivery to ablation catheter tips and tissue during RF ablation is feasible and safe and can eliminate coagulum formation, potentially reducing thromboembolic complications.

Effect of piracetam on the cognitive performance of patients undergoing coronary bypass surgery: A meta-analysis

Cognitive impairments are observed in numerous patients following coronary bypass surgery, and piracetam are nootropic compounds that modulate cerebral functions by directly enhancing cognitive processes. The present meta-analysis was conducted to evaluate the protective effect of piracetam on the cognitive performance of patients undergoing coronary bypass surgery. The relevant studies were identified by searching Medline, EMBASE, PubMed and the Cochrane Library up to June 2013 and the pertinent bibliographies from the retrieved studies were reviewed. Data were selected from the studies according to predefined criteria. The meta-analysis included two randomized control trials involving 184 patients and including the Syndrom-Kurz test (SKT). Findings of the meta-analysis showed that following treatment the change from baseline observed in five SKT subtest scores, conducted with piracetam patients, indicated a significant advantage over those patients that were in the placebo group. The subtests included immediate pictured object recall, weighted mean difference (WMD)=0.91, 95% confidence interval (CI) 0.51–1.31, P<0.00001; delayed pictured object recall, WMD=0.74, 95% CI 0.19–1.28, P=0.008; delayed picture recognition, WMD=0.82, 95% CI 0.31–1.31, P=0.001; immediate word recall, WMD=0.87, 95% CI 0.47–1.28, P<0.0001; and letter interference, WMD=3.46, 95% CI −5.69 to −1.23, P=0.002. These results indicated that piracetam may have been effective in improving the short-term cognitive performance of patients undergoing coronary bypass surgery. High quality, well-controlled and longer randomized trials are required to corroborate this result.

Neurobehavioral assessment in forensic practice

There is a growing awareness among mental health practitioners that many mental disorders previously believed to be primarily behavioral in nature, reflecting character and environment, are actually grounded in brain mal-development or brain disorder. This growing awareness, influenced by the advent of new diagnostic procedures and measures, is also found among forensic practitioners. In this paper, we describe some of the elements involved in conducting a neurobehavioral assessment of cognitive functioning, particularly in capital cases, organizing this material in terms of the professional disciplines - social work, mitigation investigation, psychological, and medical - with which these methods are mainly identified. The paper concludes with a brief discussion of how to integrate the multiple areas of expertise to create an accurate understanding of the neurobehavioral functioning and capacity of the subject. This is the basis from which civil and criminal forensic opinions must emanate.

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.

Dementia and depression with ischemic heart disease: a population-based longitudinal study comparing interventional approaches to medical management

BACKGROUND

We compared the proportion of ischemic heart disease (IHD) patients newly diagnosed with dementia and depression across three treatment groups: percutaneous coronary intervention (PCI), coronary artery bypass grafting (CABG) and medical management alone (IHD-medical).

METHODS AND FINDINGS

De-identified, individual-level administrative records of health service use for the population of Manitoba, Canada (approximately 1.1 million) were examined. From April 1, 1993 to March 31, 1998, patients were identified with a diagnosis of IHD (ICD-9-CM codes). Index events of CABG or PCI were identified from April 1, 1998 to March 31, 2003. Outcomes were depression or dementia after the index event. Patients were followed forward to March 31, 2006 or until censored. Proportional hazards regression analysis was undertaken. Independent variables examined were age, sex, diabetes, hypertension and income quintile, medical management alone for IHD, or intervention by PCI or CABG. Age, sex, diabetes, and presence of hypertension were all strongly associated with the diagnosis of depression and dementia. There was no association with income quintile. Dementia was less frequent with PCI compared to medical management; (HR = 0.65; p = 0.017). CABG did not provide the same protective effect compared to medical management (HR = 0.90; p = 0.372). New diagnosis depression was more frequent with interventional approaches: PCI (n = 626; hazard ratio = 1.25; p = 0.028) and CABG (n = 1124, HR = 1.32; p = 0.0001) than non-interventional patients (n = 34,508). Subsequent CABG was nearly 16-fold higher (p<0.0001) and subsequent PCI was 22-fold higher (p<0.0001) for PCI-managed than CABG-managed patients.

CONCLUSIONS

Patients managed with PCI had the lowest likelihood of dementia-only 65% of the risk for medical management alone. Both interventional approaches were associated with a higher risk of new diagnosed depression compared to medical management. Long-term myocardial revascularization was superior with CABG. These findings suggest that PCI may confer a long-term protective effect from dementia. The mechanism(s) of dementia protection requires elucidation.

Preventive effect of gastrodin on cognitive decline after cardiac surgery with cardiopulmonary bypass: a double-blind, randomized controlled study

Cognitive decline is a common complication after cardiac surgery with cardiopulmonary bypass (CPB), but as such no pharmacological therapy has been shown to be efficacious in preventing the decline. However, gastrodin has been shown to have multi-pharmacological effects on neurological functions. We undertook this study to test the hypothesis that gastrodin would potentially prevent CPB-associated neurocognitive decline. We randomly assigned 200 patients undergoing mitral valve replacement surgery to receive either gastrodin (40 mg/kg) or saline after the induction of anesthesia and subsequently evaluated cognitive function before surgery, at discharge, and at 3rd month after surgery by using a battery of five neurocognitive tests, or adverse effects of gastrodin postoperatively. Neurocognitive decline in postoperative function was defined as a drop of 1 SD or more in the scores on tests of any one of the four domains of cognitive function. Cognitive decline occurred in 9% of the patients in the gastrodin group in contrast to 42% in the control group (P<0.01) at discharge. Cognitive outcome could be determined at 3rd month in 87 patients in the gastrodin group and 89 in the control group. Cognitive decline was detected in 6% in the gastrodin group and 31% in the control group (P<0.01). The incidences of possible adverse effects were similar between two groups. These results indicate that gastrodin is an effective and a safe drug for the prevention of neurocognitive decline in patients undergoing mitral valve replacement surgery with CPB.

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.

A Prospective 1-Year Study of Changes in Neuropsychological Functioning After Implantable Cardioverter-Defibrillator Surgery

Background—The testing of the implantable cardioverter-defibrillator (ICD), through the induction of repeated episodes of ventricular fibrillation, has been associated with disturbances in cerebral activity and increased levels of cytoplasmic enzymes. However, the neuropsychological outcomes of cerebral changes and their quality-of-life implications are unknown.

Methods and Results—Fifty-two ICD recipients completed standardized validated neuropsychological tests 1 to 3 days before ICD surgery and then 6 weeks, 6 months, and 12 months after surgery. They also completed psychometric tests measuring anxiety, depression, and quality of life. Between 31% and 39% of patients showed a significant neuropsychological impairment from their baseline function 6 weeks, 6 months, and 12 months after surgery. Ten percent of patients had late-onset deficits at 12 months only. Frequent areas of impairment were auditory and visual memory and attention. Neuropsychological impairment was not related to mood or quality of life at follow-up, although anxiety and depression predicted reduced quality of life.

Conclusions—ICD implantation is associated with neuropsychological impairment that dissipates for the majority of recipients after 12 months. Short-term memory function and attention are particularly vulnerable to changes in oxygen during ICD testing. Although anxiety and depression are prevalent, there is little evidence for the direct impact of mood on cognition, and deficits appear not to be associated with reduced quality of life. These results provide evidence for longitudinal outcomes of ICD surgery and have implications for patient rehabilitation and adjustment.

The angiotensin AT4 receptor subtype as a target for the treatment of memory dysfunction associated with Alzheimer's disease

Over recent years antihypertensive drugs, particularly angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs), have been reported to have beneficial effects upon cognitive impairment. Such findings suggest that pharmacological manipulation of angiotensin ligands may be of clinical importance in slowing or halting the cognitive deterioration seen in vascular dementia and Alzheimer's disease. The mechanism(s) underlying these improvements in cognitive function remains unclear; however, important leads are emerging. The angiotensin AT4 receptor subtype, discovered by our laboratory in 1992, influences several important behaviours and physiologies, including learning and memory, and may play a role in this cognitive improvement. This review initially describes the therapeutic drugs approved by the Federal Drug Administration and new approaches presently being developed to treat Alzheimer's disease-induced cognitive impairment. Next, the biologically-active angiotensin ligands and their respective receptor subtypes are discussed, followed by the roles of angiotensin II, angiotensin IV, ACE inhibitors and ARBs in cognitive function. We conclude with a working hypothesis concerning the importance of the AT4 receptor subtype as a new potential drug target for the treatment of Alzheimer's disease-associated memory loss.

Predicting risk of dementia in older adults: The late-life dementia risk index

OBJECTIVE

To develop a late-life dementia risk index that can accurately stratify older adults into those with a low, moderate, or high risk of developing dementia within 6 years.

METHODS

Subjects were 3,375 participants in the Cardiovascular Health Cognition Study without evidence of dementia at baseline. We used logistic regression to identify those factors most predictive of developing incident dementia within 6 years and developed a point system based on the logistic regression coefficients.

RESULTS

Subjects had a mean age of 76 years at baseline; 59% were women and 15% were African American. Fourteen percent (n = 480) developed dementia within 6 years. The final late-life dementia risk index included older age (1-2 points), poor cognitive test performance (2-4 points), body mass index <18.5 (2 points), > or =1 apolipoprotein E epsilon4 alleles (1 point), cerebral MRI findings of white matter disease (1 point) or ventricular enlargement (1 point), internal carotid artery thickening on ultrasound (1 point), history of bypass surgery (1 point), slow physical performance (1 point), and lack of alcohol consumption (1 point) (c statistic, 0.81; 95% confidence interval, 0.79-0.83). Four percent of subjects with low scores developed dementia over 6 years compared with 23% of subjects with moderate scores and 56% of subjects with high scores.

CONCLUSIONS

The late-life dementia risk index accurately stratified older adults into those with low, moderate, and high risk of developing dementia. This tool could be used in clinical or research settings to target prevention and intervention strategies toward high-risk individuals.

Rivastigmine for the prevention of postoperative delirium in elderly patients undergoing elective cardiac surgery--a randomized controlled trial

OBJECTIVE

Cardiac surgery is frequently followed by postoperative delirium, which is associated with increased 1-year mortality, late cognitive deficits, and higher costs. Currently, there are no recommendations for pharmacologic prevention of postoperative delirium. Impaired cholinergic transmission is believed to play an important role in the development of delirium. We tested the hypothesis that prophylactic short-term administration of oral rivastigmine, a cholinesterase inhibitor, reduces the incidence of delirium in elderly patients during the first 6 days after elective cardiac surgery.

DESIGN

: Double-blind, randomized, placebo-controlled trial.

SETTING

One Swiss University Hospital.

PATIENTS

One hundred twenty patients aged 65 or older undergoing elective cardiac surgery with cardiopulmonary bypass.

INTERVENTION

Patients were randomly assigned to receive either placebo or 3 doses of 1.5 mg of oral rivastigmine per day starting the evening before surgery and continuing until the evening of the sixth postoperative day.

MEASUREMENTS AND MAIN RESULTS

The primary predefined outcome was delirium diagnosed with the Confusion Assessment Method within 6 days postoperatively. Secondary outcome measures were the results of daily Mini-Mental State Examinations and clock drawing tests, and the use of a rescue treatment consisting of haloperidol and/or lorazepam in patients with delirium. Delirium developed in 17 of 57 (30%) and 18 of 56 (32%) patients in the placebo and rivastigmine groups, respectively (p = 0.8). There was no treatment effect on the time course of Mini-Mental State Examinations and clock drawing tests (p = 0.4 and p = 0.8, respectively). There was no significant difference in the number of patients receiving haloperidol (18 of 57 and 17 of 56, p = 0.9) or lorazepam (38 of 57 and 35 of 56, p = 0.6) in the placebo and rivastigmine groups, respectively.

CONCLUSION

This negative or, because of methodologic issues, possibly failed trial does not support short-term prophylactic administration of oral rivastigmine to prevent postoperative delirium in elderly patients undergoing elective cardiac surgery with cardiopulmonary bypass.

The cognitive consequences of critical illness: practical recommendations for screening and assessment

Critically ill patients are at risk for several secondary complications, including delirium and long-term cognitive impairment. The exact mechanisms of delirium and ICU-related cognitive decline are not fully understood; however, the authors review several recent investigations that have proposed plausible explanations. This article also includes several practical guidelines for the identification and management of delirium to aid in the development and implementation of clinical procedures that will lower the risk for ICU delirium and cognitive decline.

Neuropsychiatric consequences of coronary artery bypass grafting and noncardiovascular surgery

This paper rewiews findings regarding short- and long-term neuropsychiatnc consequences of coronary artery bypass grafting (CABG) and noncardiac surgery. Stroke is one of the potentially most serious complications of CABG; studies have identified some demographic and medical risk factors. Short-term neuropsychological deficits are common after CABG, but have been similarly documented in noncardiac surgery patients, and may therefore not be specific to this procedure. Neuropsychological deficits in some cognitive areas may persist over time. Patients with depression before surgery are likely to have persistent depression afterwards. Also, depression does not account for the cognitive decline after CABG. Conflicting findings, and the possible methodological limitations of current published studies, are presented and discussed.

Loss of IQ in the ICU brain injury without the insult

Critically ill patients are at high risk of developing serious neurological dysfunctions including delirium and long-term neurocognitive impairment. Here a novel mechanism is proposed for this highly deleterious condition. A growing body of evidence has shown that critical illness and its treatment can lead to de novo cerebral atrophy including white and grey matter abnormalities, delirium, and neurocognitive decline. In healthy individuals, normal and consistent connectivity between the posterior parietal cortex (PPC), medial temporal lobe (MTL) and prefrontal cortex (PFC) maintains consciousness and normal cognitive functioning. The circuit is innervated, activated and maintained by the ascending reticular activating system (ARAS) arising from the brainstem. As elderly individuals begin to show signs of grey matter atrophy in the PPC, MTL and PFC, functional connectivity between these regions remains intact; however, the strength of the connections is no longer robust as it once was in the healthy CNS. This circuit continues to be activated and maintained via the ARAS. Individuals treated in the ICU are subject to a number of medical and pharmacological challenges which may disrupt normal CNS connectivity. Serious illnesses such as sepsis, acute respiratory distress syndrome (ARDS), and acute lung injury (ALI), as well as sedative and analgesic medications commonly prescribed in the ICU have the potential to disrupt the functional link in the circuit described above. Minor fluctuations in the ARAS (i.e. hyper or hypo activation) may be sufficient in elderly individuals to cause a disruption which surpasses the critical threshold of functional connectivity necessary to maintain normal (i.e. non-delirious) consciousness. In combination with exposure to other ICU related threats to neurocognitive function, prolonged decoupling of this circuit may lead to deleterious neurodegenerative consequences such as excitotoxicity. Over time this has the potential to result in apoptosis and long-term cognitive impairment. Delirium appears to be a good candidate for the causal mechanism of ICU related cognitive decline and may be a critical point of intervention.

Assessing neurocognitive outcomes after critical illness: are delirium and long-term cognitive impairments related?

PURPOSE OF REVIEW

Critically ill patients have a high risk of developing neurologic dysfunction including delirium and long-term cognitive impairment. In this paper we examine possible relationships between delirium and long-term cognitive impairments and explore this in the context of critical illness.

RECENT FINDINGS

Critical illness and its treatment can lead to neurologic morbidity including neuropathological abnormalities, delirium, and cognitive impairments. The association between delirium and long-term cognitive impairments has been shown in a number of populations. Among intensive care unit cohorts, delirium appears to be one of many possible causes of cognitive impairments and may be a leading modifiable cause. The mechanisms of both delirium and intensive care unit related cognitive impairment remain unclear, although a variety of common mechanisms have been proposed.

SUMMARY

Potential neurologic consequences of critical illness include delirium and long-term cognitive impairments. Defining the extent of their association in intensive care unit cohorts is an important research priority due to the high prevalence of delirium and persistent cognitive impairments in critically ill patients. Future research should focus on strategies for the early identification of delirium and cognitive impairments, elucidating mechanisms of brain injury, and the development and implementation of therapeutic modalities designed to prevent or decrease delirium and cognitive morbidity.

Long-term neurocognitive function after critical illness

BACKGROUND

Until relatively recently, critical care practitioners have focused on the survival of their patients and not on long-term outcomes. The incidence of chronic neurocognitive dysfunction has been underestimated and underreported, and only recently has it been studied in critically ill patients. However, neurocognitive outcomes have been the subject of extensive investigation in other medical populations for many years.

METHODS

Review of the current literature regarding long-term neurocognitive outcomes following critical illness.

RESULTS

Data from studies to date indicate that critical illness can lead to significant neurocognitive impairments. The neurocognitive impairments persist for months and years, and may have important consequences for quality of life, the ability to return to work, overall functional ability, and substantial economic costs. The mechanisms of the neurocognitive impairments are not fully understood but likely include delirium, hypoxia, glucose dysregulation, metabolic derangements, inflammation, and the effects of sedatives and narcotics among other factors. The contributions of these factors may be particularly significant in patients with preexisting vulnerabilities for the development of cognitive impairments such as mild cognitive impairment, dementia, prior traumatic brain injury, or other comorbid disorders associated with neurocognitive impairments.

CONCLUSIONS

Current research indicates that neurocognitive sequelae following critical illness are common, may be permanent, and are associated with impairments in daily function, decreased quality of life, and an inability to return to work. Research needs to be done to better understand the prevalence, nature, risk factors, and nuances of the neurocognitive impairments observed in ICU survivors.

Piracetam Prevents Cognitive Decline in Coronary Artery Bypass: A Randomized Trial Versus Placebo

BACKGROUND

Coronary artery bypass grafting (CABG) can be associated with postoperative cognitive impairment and ischemic stroke. No effective treatment is currently available. The aim of this study was to evaluate the effectiveness of piracetam to treat the cognitive impairment after CABG in an investigator-initiated, double-blind, placebo-controlled, randomized clinical trial.

METHODS

Patients undergoing CABG (n = 98) were randomized to placebo (n = 48) or piracetam (n = 50). Study drugs were administered intravenously (150 mg/kg daily; 300 mg/kg on the day of surgery) from the day before surgery to 6 days after surgery, then orally (12 g/day) up to 6 weeks after surgery. Cognitive function was assessed before surgery (baseline) and 6 weeks after surgery (outcome) by using a battery of 12 neuropsychologic tests. The Spielberger Anxiety Inventory and the Beck Depression Inventory were also administered. The combined score derived from the standardized neuropsychologic assessments was analyzed by using an analysis of covariance with baseline and education as covariates.

RESULTS

Six weeks after surgery, the combined score indicated a statistically significant treatment effect in the per protocol population (1.848, p = 0.041) and a tendency towards statistical significance in the intent-to-treat population (1.624, p = 0.064) in the group treated with piracetam, but no statistically significant treatment effect was seen in the placebo. The state of anxiety measured by the Spielberger Anxiety Inventory was decreased in both groups (-9.27 and -6.37 in the placebo and piracetam groups, respectively).

CONCLUSIONS

Six weeks after CABG, cognition was significantly improved in patients treated with piracetam. Additional trials are required to confirm these effects.

The role of oxidative stress in postoperative delirium

AIM

This study aimed to determine a marker that predicts delirium using preoperative oxidative processes in patients undergoing cardiopulmonary bypass surgery.

METHOD

Twelve of the 50 patients included in the study showed signs of delirium during postoperative follow-up. The Delirium Rating Scale was used in patients with delirium according to DSM-IV-TR in the postoperative period. Venous blood samples were obtained from the patients the day before and the day after the surgery to determine plasma antioxidant enzyme levels.

RESULTS

While there were no differences in preoperative superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and malondialdehyde (MDA) levels in both groups, catalase (CAT) levels were significantly lower in the delirium group. Postoperative SOD and MDA levels were also higher in the delirium group, while the GSH-Px levels were found to be lower when compared with those during the preoperative period. In the nondelirium group, the postoperative MDA and GSH-Px levels were found to be lower than preoperative levels, and postoperative SOD levels were found to be higher than preoperative levels. CAT levels were lower in the delirium group when the pre- and postoperative levels were compared in both groups. The postoperative levels of SOD, GSH-Px and CAT in the nondelirium group and MDA in the delirium group were significantly higher than preoperative levels.

CONCLUSION

Patients with low preoperative CAT levels appeared to be more susceptible to delirium than patients with higher CAT levels.

Pharmacological strategies for the prevention of Alzheimer's disease

This review examines key pharmacological strategies that have been clinically studied for the primary or secondary prevention of Alzheimer's disease. Much information (neuropsychological, genetic and imaging) is already available to characterise an individual's risk for developing Alzheimer's disease. However, regulatory pathways for obtaining a prevention indication are less well charted, and such trials tend to involve 3- to 7-year studies of 1000 - 5000 individuals, depending on baseline status. Treatments developed for prevention will also need to have superior safety. For these reasons, > 100 proprietary pharmacological products are currently being developed for an Alzheimer's disease treatment, but only a few are being studied for prevention. Randomised trial data are available for antihypertensive agents (calcium channel blockers, angiotensin-converting enzyme inhibitors), pravastatin, simvastatin, conjugated oestrogen, raloxifene, rofecoxib, CX516 (AMPA agonist) and cholinesterase inhibitors regarding efficacy for Alzheimer's disease prevention. At least four large prevention trials of conjugated oestrogen, selenium and vitamin E, Ginkgo biloba and statins are currently underway. Strategies using other agents have not yet been evaluated in Alzheimer's disease prevention clinical trials. These include anti-amyloid antibodies, active immunisation, selective secretase inhibitors and modulators, microtubule stabilisers (e.g., paclitaxel), R-flurbiprofen, xaliproden, ONO-2506, FK962 (somatostatin releaser), SGS 742 (GABA(B) antagonist), TCH 346 (apoptosis inhibitor), Alzhemedtrade mark, phophodiesterase inhibitors, rosiglitazone, leuprolide, interferons, metal-protein attenuating compounds (e.g., PBT2), CX717, rasagaline, huperzine A, antioxidants and memantine. Studies combining lifestyle modification and drug therapy have not been conducted. Full validation of surrogate markers for disease progression (such as amyloid imaging) should further facilitate drug development. Reducing the complexity of prevention trials and gaining regulatory consensus of design is a high priority for the field.

A population-based study of the association between coronary artery bypass graft surgery (CABG) and cognitive decline: the Cache County study

BACKGROUND

The relationship between coronary artery bypass graft (CABG) surgery and cognitive decline remains uncertain, in particular with regard to whether there is delayed cognitive decline associated with this procedure.

METHODS

This was a population-based cohort study involving participants in the Cache County Study of Memory Health and Aging. At baseline the study enrolled 5,092 persons age 65 and older and followed them up three years later and again four years after that. Individuals who reported having undergone CABG surgery at study baseline or had this surgery in between follow-up waves were compared to individuals who never reported having the surgery. The main outcome measure was the Modified Mini Mental State (3MS). Multilevel models were used to examine the relationship between CABG surgery and cognitive decline over time.

RESULTS

Study participants who had CABG surgery evidenced 0.95 points of greater decline relative to baseline on the 3MS at the first follow-up interview after CABG, and an average of 1.9 points of greater decline at the second follow-up interview, than those without CABG (t = -2.51, df = 2,316, p = 0.0121), after adjusting for several covariates, including number of vascular conditions. This decline was restricted to individuals who were more than five years past the procedure and was not evident in the early years after the surgery.

CONCLUSIONS

CABG surgery is associated with accelerated cognitive decline more than five years after the procedure in a long-lived population. This decline is small and its clinical significance is uncertain. We could not find an association between CABG and decline in the first five post-operative years.

Understanding reported cognitive dysfunction in older adults with cardiovascular disease

Older adults with cardiovascular disease (CVD) often report experiencing significant cognitive dysfunction in everyday life and exhibit deficits on neuropsychological testing. However, the relationship between subjective and objective cognitive dysfunction is inconsistent across studies and requires closer examination. Participants included 84 older adults with documented CVD and no history of neurological or severe psychiatric disorder. All participants underwent echocardiogram and neuropsychological assessment and completed self-report measures of perceived cognitive dysfunction, depression, and health-related quality of life. Results showed that concerns regarding distractibility and sustained attention were most common. Level of reported cognitive dysfunction was significantly related to depressive symptoms, quality of life, and performance on multiple cognitive tests. Exploratory regression analyses showed that depressive symptoms, physical health-related quality of life, and speeded sustained attention predicted reports of cognitive dysfunction, whereas demographic variables, cardiac output, and other cognitive tests did not. Should they be replicated, these findings suggest that reports of cognitive dysfunction in older adults with CVD largely reflect depressive symptoms and reduced quality of life.

Stroke and Encephalopathy After Cardiac Surgery

Background and Purpose— As a result of advances in surgical, anesthetic, and medical management, cardiac surgery can now be performed on older, sicker patients, some of whom have had prior cardiac interventions. As surgical mortality has declined in recent years, attention has focused on the complications of stroke and encephalopathy after cardiac surgery.

Summary of Review— Patients with preexisting cerebrovascular disease are at increased risk for these untoward neurological outcomes, which are associated with longer lengths of hospital stay, higher costs, and greater mortality. The mechanisms underlying these neurological events may include microemboli and hypoperfusion during surgery, and postoperative atrial fibrillation. Predictive models, based on information available before surgery, allow identification of these “high risk” patients.

Conclusion— Establishing the degree of functionally significant vascular disease of the brain before surgery should be an essential part of the preoperative evaluation, particularly when modifications in surgical technique or novel neuroprotective agents are being evaluated.

Outcomes of coronary artery bypass graft surgery

This review article summarizes the major studies that have investigated the outcomes of coronary artery bypass graft surgery (CABG). The article includes a review of the literature in the areas of: history of CABG; indications for CABG; and measurement of quality of life following CABG, including prolongation of life, physical functioning (ie, relief from angina and dyspnea, physical activity, as well as complications of surgery and re-hospitalization), psychological functioning, and social functioning. Overall, the literature demonstrates that the outcomes of CABG have historically been measured in terms of mortality and morbidity; however, it has now been well recognized that adjustment to CABG is a multidimensional phenomenon that is not fully explained by medical factors. Therefore, in addition to studying mortality and morbidity outcomes following CABG many recent studies have identified that it is important to investigate various physical, psychological, and social variables that have a significant impact on post-operative adjustment to CABG.