CEREBRAL DISORDERS AFTER OPEN-HEART OPERATIONS

Potential Markers of Neurocognitive Disorders After Cardiac Surgery: A Bibliometric and Visual Analysis

Background

Identifying useful markers is essential for diagnosis and prevention of perioperative neurocognitive disorders (PNDs). Here, we attempt to understand the research basis and status, potential hotspots and trends of predictive markers associated with PNDs after cardiac surgery via bibliometric analysis.

Methods

A total of 4,609 original research articles and reviews that cited 290 articles between 2001 and 2021 were obtained from the Web of Science Core Collection (WoSCC) as the data source. We used the software CiteSpace to generate and analyze visual networks of bibliographic information, including published years and journals, collaborating institutions, co-cited references, and co-occurring keywords.

Results

The number of annual and cumulative publications from 2001 to 2021 has been increasing on the whole. The Harvard Medical School was a very prolific and important institution in this field. The journal of Ann Thorac Surg (IF 4.33) had the most publications, while New Engl J Med was the most cited journal. Neuron-specific enolase (NSE), S100b and kynurenic acid (KYNA) were frequently discussed as possible markers of PNDs in many references. Cardiopulmonary bypass (CPB) was a keyword with high frequency (430) and sigma (6.26), and inflammation was the most recent burst keyword.

Conclusion

Potential markers of PNDs has received growing attention across various disciplines for many years. The research basis mainly focuses on three classic biomarkers of S100b, NSE, and KYNA. The most active frontiers are the inflammation-related biomarkers (e.g., inflammatory cells, cytokines, or mediators) and surgery-related monitoring parameters (e.g., perfusion, oxygen saturation, and the depth of anesthesia).

Early and late outcomes of surgical aortic valve replacement with sutureless and rapid-deployment valves versus transcatheter aortic valve implantation: Meta-analysis with reconstructed time-to-event data of matched studies

Sutureless/rapid-deployment (SURD) valves are options different from the stented prostheses included in the pivotal trials comparing surgical aortic valve replacement (AVR) and transcatheter aortic valve implantation (TAVI). We performed a meta-analysis with reconstructed time-to-event data of matched studies published by November 2021 to compare SURD-AVR and TAVI. Primary endpoints were 30-day mortality and overall survival in the follow-up. Secondary endpoints included: 30-day stroke, acute kidney injury (AKI), major bleeding, permanent pacemaker implantation (PPI), paravalvular leak (PVL), prosthesis-patient mismatch (PPM), postoperative aortic valve area (AVA), and mean gradients. Ten studies met our eligibility criteria, including a total of 5134 patients (2567 underwent SURD-AVR and 2567 underwent TAVI). Pooled risk of 30-day mortality did not favor any group (odds ratio [OR]: 0.69; 95% confidence interval [CI]: 0.31-1.53; p = 0.360). Patients undergoing SURD-AVR had lower risk of PVL (OR: 0.09; 95% CI: 0.05-0.17; p < 0.001). No statistically significant differences were observed for 30-day stroke, AKI, major bleeding, PPI, PPM, and postoperative AVA. In the follow-up, we observed a higher risk of mortality (hazard ratio: 1.74; 95% CI: 1.26-2.40; p < 0.001) with TAVI. Patients who underwent SURD-AVR experienced better survival, however, the interpretation of these results warrant caution due to the fact that SURD-AVR patients tended to be younger than TAVI patients. Structural heart surgeons and interventional cardiologists should consider initial risk and life expectancy when referring patients for one approach over the other.

Review of cerebral perfusion strategies for aortic surgery with application for minimally invasive approaches

Aortic arch and hemiarch surgery necessitate the temporary interruption of blood perfusion to the brain. Despite its complexity, hemiarch and ascending aortic surgery can be performed via a minimally invasive approach. Due to the higher risk of neurological injury during a circulatory arrest, several techniques were developed to further protect the brain during this surgery. We searched the Embase, Medline, and Cochrane databases and identified articles reporting outcomes of antegrade and retrograde cerebral perfusion strategies. Herein, we outline surgical approaches, intra-operative technical considerations, and clinical outcomes of hemiarch and ascending aortic surgery. Hemiarch and ascending aortic surgery is associated with a higher risk of mortality and morbidity. Attention to the optimal approach and cerebral protection strategy has been shown to significantly affect outcomes and mitigate risk.

Abnormal expression of circRNA_089763 in the plasma exosomes of patients with post‑operative cognitive dysfunction after coronary artery bypass grafting

Post-operative cognitive dysfunction (POCD) is a complication of the central nervous system characterized by mental disorders, anxiety, personality changes and impaired memory. POCD occurs frequently after coronary artery bypass grafting (CABG) and can severely affect quality of life for patients. To date, the development of POCD biomarkers remains a challenge. Alterations in the expression of non-coding RNAs from brain tissue and peripheral blood have been linked to POCD. The present study aimed to detect the differential circular RNAs (circRNAs) in plasma exosomes of patients with POCD after CABG. The relative expression levels of circRNAs were analyzed using circRNA microarray analysis in the plasma exosomes of patients with POCD. Differentially altered circRNAs (P<0.05, fold change >1.5) were validated by reverse transcription-quantitative PCR in the plasma exosomes of patients with POCD. The target genes of the microRNAs were predicted using bioinformatics analysis. The functions and signaling pathways of these target genes were investigated by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes analyses. The microarray results indicated that the levels of nine circRNAs in patients with POCD were higher than those in the control subjects; and six circRNAs were at a lower level than those in control subjects. The RT-qPCR results from patients with POCD showed that only circRNA_089763 of the 15 circRNAs identified was significantly increased compared with control subjects. circRNA target gene prediction and functional annotation analysis showed significant enrichment in several GO terms and pathways associated with POCD. The present study provides evidence for the abnormal expression of POCD-induced circRNA_089763 in human plasma exosomes, as well as the involvement of POCD.

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.

Optimal Position of Inferior Vena Cava Cannula in Pediatric Cardiac Surgery: A Prospective, Randomized, Controlled, Double-Blind Study

OBJECTIVE

To examine the authors' hypothesis that during the cardiopulmonary bypass (CPB) in children, the inferior vena cava cannula tip placed proximal to the right hepatic vein orifice would produce a higher venous drainage compared with that placed distally.

DESIGN

A prospective, randomized, controlled, double-blind study.

SETTING

Single university hospital.

PARTICIPANTS

Thirty-two patients aged <6years, scheduled for elective cardiac surgery using CPB for congenital heart disease.

INTERVENTIONS

Participants were randomized to 2 groups: the proximal group with the cannula tip placed proximally within 1cm of the right hepatic vein orifice and the distal group with the cannula placed distally within 1cm of the right hepatic vein orifice.

MEASUREMENTS AND MAIN RESULTS

The primary outcome of this study was the perfusion flow rate at the time of establishment of total CPB with cardioplegia. The authors initially planned to enroll 60 patients, but before reaching the target sample size, the authors terminated this study owing to patient safety, and 18 patients in the proximal group and 14 patients in the distal group finally were analyzed. No significant differences in patient characteristics were observed between the 2 groups. The mean perfusion flow rate in the proximal group was significantly greater (2.55 ± 0.27 L/min/m²) than that in the distal group (2.37 ± 0.20 L/min/m², p = 0.04).

CONCLUSION

The inferior vena cava cannula tip placed in the proximal position was clinically superior, compared with a distal placement, in producing higher perfusion flow in children.

Topographical distribution of perioperative cerebral infarction associated with transcatheter aortic valve implantation

BACKGROUND

Transcatheter aortic valve implantation (TAVI) is associated with a high incidence of cerebrovascular injury. As these injuries are thought to be primarily embolic, neuroprotection strategies have focused on embolic protection devices. However, the topographical distribution of cerebral emboli and how this impacts on the effectiveness of these devices have not been thoroughly assessed. Here, we evaluated the anatomical characteristics of magnetic resonance imaging (MRI)-defined cerebral ischemic lesions occurring secondary to TAVI to enhance our understanding of the distribution of cardioembolic phenomena.

METHODS

Forty patients undergoing transfemoral TAVI with an Edwards SAPIEN-XT valve under general anesthesia were enrolled prospectively in this observational study. Participants underwent brain MRI preprocedure, and 3 ± 1 days and 6 ± 1 months postprocedure.

RESULTS

Mean ± SD participant age was 82 ± 7 years. Patients had an intermediate to high surgical risk, with a mean Society of Thoracic Surgeons score of 6.3 ± 3.5 and EuroSCORE of 18.1 ± 10.6. Post-TAVI, there were no clinically apparent cerebrovascular events, but MRI assessments identified 83 new lesions across 19 of 31 (61%) participants, with a median ± interquartile range number and volume of 1 ± 2.8 lesions and 20 ± 190 μL per patient. By volume, 80% of the infarcts were cortical, 90% in the posterior circulation and 81% in the right hemisphere.

CONCLUSIONS

The distribution of lesions that we detected suggests that cortical gray matter, the posterior circulation, and the right hemisphere are all particularly vulnerable to perioperative cerebrovascular injury. This finding has implications for the use of intraoperative cerebral embolic protection devices, particularly those that leave the left subclavian and, therefore, left vertebral artery unprotected.

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.

Aortic Arch Atheroma: Stroke Reduction in Cardiac Surgical Patients

Cardiac surgery is increasingly performed on elderly patients with extensive coronary artery abnormalities who have impaired left ventricular function, decreased physiologic reserve, and multiple comorbid conditions. Considerable numbers of these patients develop perioperative neurologic complications ranging from subtle cognitive dysfunction to more evident postoperative confusion, delirium, and, less commonly, clinically apparent stroke. Magnetic resonance imaging studies have elucidated that a considerable number of patients have new ischemic brain infarcts, particularly after conventional coronary artery bypass graft surgery. Mechanisms of cerebral injury during and after cardiac surgery are discussed. Intraoperative transesophageal echocardiography and epiaortic scanning for detection of atheromatous disease of the proximal thoracic aorta is paramount in identifying patients at high risk from neurologic injury. It is important to recognize that our efforts to minimize neurologic injury should not be limited to the intraoperative period. Particular efforts should be directed to temperature management, glycemia control, and pharmacologic neuroprotection extending into the postoperative period. Preoperative magnetic resonance angiography may be of value for screening patients with significant atheroma of the proximal thoracic aorta. It is likely that for patients with no significant atheromatous disease, conventional coronary artery revascularization is the most effective long-term strategy, whereas patients with atheromatous thoracic aorta may be better managed with beating heart surgery, hybrid techniques, or medical therapy alone. Patient stratification based on the aortic atheromatic burden should be addressed in future trials designed to tailor treatment strategies to improve long-term outcomes of coronary heart disease and reduce the risks of perioperative neurologic injury.

Strategies to Protect the Brain During Cardiac Surgery

Despite significant advances in cardiopulmonary by pass (CPB) technology, surgical techniques, and anes thetic management, central nervous system (CNS) com plications remain a common and costly problem after CPB. Stroke is often considered a rare and unprevent able complication of cardiac surgery. Recent studies have shown that through the use of echocardiography and historical risk stratification strategies, we can de fine which patients are at substantially greater risk for CNS injury. Through enhanced understanding of the etiology of stroke and perioperative factors, which are associated with potential for neuroprotection or injury extension, there now exists a greater potential than ever to substantially reduce neurological injury associ ated with cardiac surgery. Strategies and theories of stratifying patients at risk and secondarily reducing that risk are described, as well as consideration for early postoperative assessment to allow treatment when events occur.

Detection, Prevention, and Management of Delirium in the Critically Ill Cardiac Patient and Patients Who Undergo Cardiac Procedures

Delirium is an acute change in cognitive functioning, characterized by inattention and associated with alterations in awareness and fluctuation in arousal, disorganized thinking, or altered level that preferentially affects older adult patients. In the acutely ill cardiac patient, the incidence of delirium has been reported as high as 73%, depending on the type and sensitivity of delirium assessment. Cardiac patients with delirium experience higher rates of in-hospital and longer-term mortality and are at risk for progressive cognitive impairment, loss of functional independence, and increased hospitalization costs. As such, delirium represents an undesirable outcome in cardiac patients. Care improvements such as identifying risk of delirium at time of admission or in the preoperative setting; training cardiologist, surgeons, anaesthesiologists and nurses to screen for delirium; implementing delirium prevention programs; and developing standardized delirium treatment protocols might reduce the incidence of delirium and its associated morbidity.

Improving Outcomes of Cardiac Surgery Through Cooperative Efforts: The Northern New England Experience

Coronary artery bypass graft (CABG) surgery is an effective procedure for relieving angina. In 1987, the Health Care Financing Administration published surgeon-specific mortality rates, prompting the formation of the Northern New England Cardiovascular Disease Study Group (NNECDSG). This regional collaborative of all medical centers performing cardiovascular procedures in northern New England began collecting data concerning patient and disease characteristics and adverse outcomes in an effort to improve the care provided to their patients. An initial quality improvement effort resulted in a 24% reduction in in-hospital mortality. Subsequent efforts have involved the development and implementation of quality improvement initiatives to redesign care to reduce further a patient's risk of mortality and other morbidities. More recently, we have adopted this model to reduce a patient's risk of neurologic injury. In this study, we are intensively monitoring patients intraoperatively with transcranial Doppler and near infrared spectroscopy as well as collecting hemodynamic data, and are synchronizing this data with a video of the surgical site. The goal of the study is to identify the association between clinical strategies and the development of the precursors of neurologic injury and use a quality improvement approach to redesign care to reduce occurrence of these precursors.

Analysis of microembolic particles originating in extracorporeal circuits

Silicone tubing is utilised increasingly in extracorporeal circulation (ECC), particularly for prolonged bypass in cases of left ventricular failure following open heart surgery. We compared the spectrum of particle formation in the EC circuit, due to roller pump damage, resulting from wear of silicone tubing with that of polyvinyl chloride (PVC) tubing. The EC circuit was primed with plasmalyte solution for pump runs of up to 24 hours. Samples of the perfusate were taken from either system at prefixed times. Number and size of the particles were determined by means of a Coulter counter, while their chemical composition was analysed by X-ray dispersion (EDXA). The tubing was examined by scanning electron microscopy. When using PVC tubing, the amount of particles of all sizes rose above acceptable standards shortly after activating the roller pump. Following this early upsurge, the number of particles continued to increase for the remainder of the pump run, albeit at a more moderate rate. The silicone tubing continuously generated a marked quantity of particular matter at a steadily increasing rate. Electron microscopic examination of the silicone tubing revealed multiple particles emanating from the inner surface of the tube. The results suggest that filtration of the initial priming fluid may be advisable before connecting the patient to an EC circuit using PVC tubing. The multitude of particles liberated by the silicone tubing implies that its usage in ECC should be curtailed. Utilisation of noncrushing head pumps is recommended in ECC.

Stroke after coronary artery surgery: a single center report

Stroke or cerebrovascular accident (CVA) is a devastating complication of coronary surgery. In this report, the incidence, and correlates of CVA following isolated coronary artery bypass grafting (CABG) surgery were evaluated. Data were collected retrospectively. Between 2006 and 2009, 855 patients underwent isolated CABG surgery. CVA was defined as any new neurological deficit lasting more than 24 hours. Univariate and multivariate analyses were utilized as appropriate. The incidence of CVA was 1.4% (n = 12). Age, previous CVA, and emergency surgery were correlated by univariate analysis. Multivariate analysis revealed age, previous CVA, and chronic renal impairment as predictors of CVA. Ten (83.3%) of the 12 patients were diagnosed to have CVA in the first 24 hours. Length of hospital stay was 20.9 ± 20.34 days for CVA patients and 9.2 ± 5.17 days for non-CVA patients (p ≤ 0.001). There were 4 (33.3%) deaths in CVA group and 27 (3.2%) for non-CVA patients (p = 0.001). Postoperative CVA is a major contributor to mortality, prolonged hospitalization, and other adverse postoperative complications. Further studies are needed to develop better strategies to minimize the occurrence of CVA among patients undergoing CABG.

Current readings: neurocognitive impairment and clinical implications after cardiac surgery

The earliest reports of cardiac surgery literatures reported evidence of neurocognitive decline, highlighted in the 1995 statement of Consensus on assessment of neurobehavioral outcomes after cardiac surgery. Until now, the magnitude and clinical importance of neurocognitive outcomes continues to fluctuate and lack clarity. The aim of this review is to evaluate the contemporary status of neurocognitive outcomes in relation to pre-existing impairment, revascularization strategy, broader cardiovascular pathophysiological processes, and any longer-term clinical implications. Five studies published between 2009 and 2013 were reviewed. A meta-analysis did not find differences between on- and off-pump procedures. In other studies, there was evidence for extensive preoperative neurocognitive impairments. Additional 2 studies showed that longer-term neurocognitive impairment, including dementia, was not dissimilar to nonsurgical patients with cardiovascular disease. Currently, there is no convincing evidence to suggest that cardiac surgery, and cardiopulmonary bypass in particular, has a causal role in progression to dementia, or long-term deficit, independent of pre-existing neurocognitive impairments and cardiovascular disease.

Neurological complications of cardiac surgery

As increasing numbers of elderly people undergo cardiac surgery, neurologists are frequently called upon to assess patients with neurological complications from the procedure. Some complications mandate acute intervention, whereas others need longer term observation and management. A large amount of published literature exists about these complications and guidance on best practice is constantly changing. Similarly, despite technological advances in surgical intervention and modifications in surgical technique to make cardiac procedures safer, these advances often create new avenues for neurological injury. Accordingly, rapid and precise neurological assessment and therapeutic intervention rests on a solid understanding of the evidence base and procedural variables.

Brain damage and cardiopulmonary bypass: is there really any association?

Brain damage, in the form of stroke and cognitive deficit associated with heart surgery, has long been attributed unquestioningly to cardiopulmonary bypass (CPB). The aim of this paper is to review the randomised control trials (RCT), systematic reviews and meta-analyses of studies, comparing patients who have undergone on- or off-pump coronary artery bypass grafting (CABG) surgeries that have used stroke or cognition as an outcome to determine whether CPB is associated with brain damage. Although not definitive, the evidence base to date strongly suggests that the incidence of stroke and the effect on cognition, if any, are no different whether CABG surgery is undertaken on- or off-pump. In addition and contrary to long-held beliefs, this review leads to the conclusion that CPB may well not be the cause of the brain damage associated with heart surgery.

Is carotid artery disease responsible for perioperative strokes after coronary artery bypass surgery?

The coronary and extracranial carotid vascular beds are often simultaneously affected by significant atherosclerotic disease, and stroke is one of the potential major complications of coronary artery surgery. As a result, there is no shortage of reports in the vascular surgery literature describing simultaneous coronary and carotid artery revascularizations. Generally, these reports have found this combination of operations safe, but have stopped short of proving that it is necessary. Intuitively, simultaneous carotid endarterectomy and coronary artery bypass surgery could be justified if most perioperative strokes were the result of a significant carotid stenosis, either directly or indirectly. At first glance this appears to be a fairly straightforward issue; however, much of the evidence on both sides of the argument is circumstantial. One significant problem in analyzing outcome by choice of treatment in patients presenting with both coronary and carotid disease is the multiple potential causes of stroke in coronary bypass patients, which include hemorrhage and atheroemboli from aortic atheromas during clamping. But this controversial subject is now open to discussion, and our debaters have been given the challenge to clarify the evidence to justify their claims.

Independent association between preoperative cognitive status and discharge location after cardiac surgery

BACKGROUND

Among cardiac surgery patients, those with impaired cognitive status before surgery may have longer postoperative stays than do patients with normal status and may require additional care upon discharge.

OBJECTIVES

To determine if preoperative scores on a screening measure for cognitive status (the Clock-in-the-Box), were associated with postoperative length of stay and discharge to a location other than home in patients who had cardiac surgery.

METHODS

A total of 181 consecutive patients scheduled for cardiac surgery at a single site were administered the Clock-in-the-Box as part of the preoperative evaluation. Scores on the Clock-in-the-Box tool, demographic and operative information, postoperative length of stay, and discharge location were collected retrospectively from medical records.

RESULTS

The mean age of the patients was 68.1 years (SD, 0.7), and 99% were men. Mean postoperative length of stay was 10.5 days (SD, 8.2), and 35 patients (19%) were discharged to a facility. Scores on the Clock-in-the-Box assessment were not associated with postoperative length of stay. Increasing age, living alone before surgery, and duration of cardiopulmonary bypass were associated with discharge to a facility and were used as covariates in adjusted analyses. After adjustment, better preoperative cognitive status reduced the risk of being discharged to a facility (adjusted relative risk, 0.93; 95% confidence interval, 0.89-0.98) after cardiac surgery.

CONCLUSIONS

Cognitive screening before cardiac surgery can identify patients with impaired cognitive status who are less likely than patients with normal cognitive status to return home after cardiac surgery.

Development of a unidimensional composite measure of neuropsychological functioning in older cardiac surgery patients with good measurement precision

The objective of this analysis was to develop a measure of neuropsychological performance for cardiac surgery and to assess its psychometric properties. Older patients (n = 210) underwent a neuropsychological battery using nine assessments. The number of factors was identified with variable reduction methods. Factor analysis methods based on item response theory were used to evaluate the measure. Modified parallel analysis supported a single factor, and the battery formed an internally consistent set (coefficient alpha = .82). The developed measure provided a reliable, continuous measure (reliability > .90) across a broad range of performance (-1.5 SDs to +1.0 SDs) with minimal ceiling and floor effects.

Predictive Model for Postoperative Delirium in Cardiac Surgical Patients

Delirium is a common complication following cardiac surgery, and the predictors of delirium remain unclear. The authors performed a prospective observational analysis to develop a predictive model for postoperative delirium using demographic and procedural parameters. A total of 112 adult postoperative cardiac surgical patients were evaluated twice daily for delirium using the Richmond Agitation-Sedation Scale (RASS) and Confusion Assessment Model for the ICU (CAM-ICU). The incidence of delirium was 34% (n = 38). Increased age (odds ratio [OR] = 2.5; 95% confidence interval [CI] = 1.6-3.9; P < .0001, per 10 years) and increased duration of surgery (OR = 1.3; 95% CI = 1.1-1.5; P = .0002, per 30 minutes) were independently associated with postoperative delirium. Gender, BMI, diabetes mellitus, preoperative ejection fraction, surgery type, length of cardiopulmonary bypass, intraoperative blood component administration, Acute Physiology and Chronic Health Evaluation II score, Sequential Organ Failure Assessment score, and Charlson Comorbidity Index, were not independently associated with postoperative delirium.

Detection and Elimination of Microemboli Related to Cardiopulmonary Bypass

Background— Neurobehavioral impairment is a common complication of coronary bypass surgery. Cerebral microemboli during cardiopulmonary bypass (CPB) are a principal mechanism of cognitive injury. The aim of this work was to study the occurrence of cerebral embolism during CPB and to evaluate the effectiveness of evidence-based CPB circuit component and process changes on the exposure of the patient to emboli.

Methods and Results— M-Mode Doppler was used to detect emboli in the inflow and outflow of cardiopulmonary circuit and in the right and left middle cerebral arteries. Doppler signals were merged into a single display to allow real-time associations between discrete clinical techniques and emboli detection. One hundred sixty-nine isolated coronary artery bypass grafting (CABG) patients were studied between 2002 and 2008. There was no statistical difference in median microemboli detected in the inflow of the CPB circuit, (Phase I, 931; Phase II, 1214; Phase III, 1253; Phase IV, 1125; F [3,158]=0.8, P =0.96). Significant changes occurred in median microemboli detected in the outflow of the CPB circuit across phases, (Phase I, 702; Phase II, 572; Phase III, 596; Phase IV, 85; F [3,157]=13.1, P <0.001). Significant changes also occurred in median microemboli detected in the brain across phases, (Phase I, 604; Phase II, 429; Phase III, 407; Phase IV, 138; F [3,153]=14.4, P <0.001). Changes in the cardiopulmonary bypass circuit were associated with an 87.9% (702 versus 85) reduction in median microemboli in the outflow of the CPB circuit ( P <0.001), and a 77.2% (604 versus 146) reduction in microemboli in the brain ( P <0.001).

Conclusions— Changes in CPB techniques and circuit components, including filter size and type of pump, resulted in a reduction in more than 75% of cerebral microemboli.

Derivation and validation of a preoperative prediction rule for delirium after cardiac surgery

BACKGROUND

Delirium is a common outcome after cardiac surgery. Delirium prediction rules identify patients at risk for delirium who may benefit from targeted prevention strategies, early identification, and treatment of underlying causes. The purpose of the present prospective study was to develop a prediction rule for delirium in a cardiac surgery cohort and to validate it in an independent cohort.

METHODS AND RESULTS

Prospectively, cardiac surgery patients > or =60 years of age were enrolled in a derivation sample (n=122) and then a validation sample (n=109). Beginning on the second postoperative day, patients underwent a standardized daily delirium assessment, and delirium was diagnosed according to the confusion assessment method. Delirium occurred in 63 (52%) of the derivation cohort patients. Multivariable analysis identified 4 variables independently associated with delirium: prior stroke or transient ischemic attack, Mini Mental State Examination score, abnormal serum albumin, and the Geriatric Depression Scale. Points were assigned to each variable: Mini Mental State Examination < or =23 received 2 points, and Mini Mental State Examination score of 24 to 27 received 1 point; Geriatric Depression Scale >4, prior stroke/transient ischemic attack, and abnormal albumin received 1 point each. In the derivation sample, the cumulative incidence of delirium for point levels of 0, 1, 2, and > or =3 was 19%, 47%, 63%, and 86%, respectively (C statistic, 0.74). The corresponding incidence of delirium in the validation sample was 18%, 43%, 60%, and 87%, respectively (C statistic, 0.75).

CONCLUSIONS

Delirium occurs frequently after cardiac surgery. Using 4 preoperative characteristics, clinicians can determine cardiac surgery patients' risk for delirium. Patients at higher delirium risk could be candidates for close postoperative monitoring and interventions to prevent delirium.

Neurological complications of cardiac surgery

Neurological injury resulting from cardiac surgery has a range of manifestations from focal neurological deficit to encephalopathy or coma. As the safety of drug-eluting stents comes into question, more patients will likely undergo coronary artery bypass graft surgery. These projections, along with the growing proportions of elderly patients and those with comorbidities, portend the potential for rising rates of perioperative neurological complications. The risk for neurological injury may be determined by the type of procedure, by patient-specific characteristics, and by the extent of cerebral embolization and hypoperfusion during and after surgery. Changes in surgical techniques, including the use of off-pump surgery, have not decreased rates of brain injury from cardiac surgery. When appropriate, modern neuroimaging techniques should be used in postoperative patients to confirm diagnosis, to provide information on potential etiology, to direct appropriate therapy, and to help in prognostication. Management of postoperative medications and early use of rehabilitation services is a recommended strategy to optimize the recovery for individuals with neurological injury after cardiac surgery.

Technology insight: brain MRI and cardiac surgery--detection of postoperative brain ischemia

Annually, an estimated 1 million patients undergo heart surgery worldwide. Unfortunately, stroke continues to be a frequent complication of cardiac surgery, with the specific cerebrovascular risk depending upon the particular surgical procedure performed. Neuroimaging has an integral role in the initial evaluation and management of patients who present with acute stroke symptoms following cardiac surgery. The aim of this paper is to review the role brain MRI has in detecting postoperative brain ischemia in these patients. Multimodal MRI--using diffusion-weighted MRI (DWI), perfusion-weighted MRI, and gradient-recalled echo imaging--has an excellent capacity to identify and delineate the size and location of acute ischemic strokes as well as intracerebral hemorrhages. This differentiation is critical in making appropriate treatment decisions in the acute setting, such as determining patient eligibility for thrombolytic or hemodynamic therapies. At present, DWI offers prognostic value in patients with strokes following cardiac surgery. Additionally, DWI could be a valuable tool for evaluating stroke preventive measures as well as therapeutic interventions in patients undergoing CABG surgery.

Preoperative predictors of delirium after cardiac surgery: a preliminary study

Preoperative risk factors of postoperative delirium were evaluated in 260 patients admitted for open heart surgery. The incidence of delirium was 11.5%. Independent predictors included cognitive impairment, atrial fibrillation, a history of peripheral vascular disease major depression and advanced age. Aforementioned factors might be helpful in predicting delirium following cardiac surgery.

Central nervous system injury associated with cardiac surgery

Millions of individuals with coronary artery or valvular heart disease have been given a new chance at life by heart surgery, but the potential for neurological injury is an Achilles heel. Technological advancements and innovations in surgical and anaesthetic technique have allowed us to offer surgical treatment to patients at the extremes of age and infirmity-the group at greatest risk for neurological injury. Neurocognitive dysfunction is a complication of cardiac surgery that can restrict the improved quality of life that patients usually experience after heart surgery. With a broader understanding of the frequency and effects of neurological injury from cardiac surgery and its implications for patients in both the short term and the long term, we should be able to give personalised treatments and thus preserve both their quantity and quality of life. We describe these issues and the controversies that merit continued investigation.

Magnesium as a neuroprotectant in cardiac surgery: A randomized clinical trial

OBJECTIVE

We sought to evaluate magnesium as a neuroprotectant in patients undergoing cardiac surgery with cardiopulmonary bypass.

METHODS

From February 2002 to September 2003, 350 patients undergoing elective coronary artery bypass grafting, valve surgery, or both were enrolled in a randomized, blinded, placebo-controlled trial to receive either magnesium sulfate to increase plasma levels 1(1/2) to 2 times normal during cardiopulmonary bypass (n = 174) or no intervention (n = 176). Neurologic function, neuropsychologic function, and depression were assessed preoperatively, at 24 and 96 hours after extubation (neurologic) and at 3 months (neuropsychologic, depression). Neurologic scores were analyzed using ordinal longitudinal methods, and neuropsychologic and depression inventory data were summarized by principal component analysis, followed by linear regression analysis using component scores as response variables.

RESULTS

Seven (2%) patients had a postoperative stroke, 2 (1%) in the magnesium and 5 (3%) in the placebo group (P = .4). Neurologic score was worse postoperatively in both groups (P < .0001); however, magnesium group patients performed better than placebo group patients (P = .0001), who had prolonged declines in short-term memory and reemergence of primitive reflexes. Three-month neuropsychologic performance and depression inventory score were generally better than preoperatively, with few differences between groups (P > .6); however, older age (P = .0006), previous stroke (P = .003), and lower education level (P = .0007) were associated with worse performance.

CONCLUSIONS

Magnesium administration is safe and improves short-term postoperative neurologic function after cardiac surgery, particularly in preserving short-term memory and cortical control over brainstem functions. However, by 3 months, other factors and not administration of magnesium influence neuropsychologic and depression inventory performance.

KTX 0101: a potential metabolic approach to cytoprotection in major surgery and neurological disorders

KTX 0101 is the sodium salt of the physiological ketone, D-beta-hydroxybutyrate (betaOHB). This neuroprotectant, which has recently successfully completed clinical Phase IA evaluation, is being developed as an intravenous infusion fluid to prevent the cognitive deficits caused by ischemic foci in the brain during cardiopulmonary bypass (CPB) surgery. KTX 0101 maintains cellular viability under conditions of physiological stress by acting as a "superfuel" for efficient ATP production in the brain and peripheral tissues. Unlike glucose, this ketone does not require phosphorylation before entering the TCA cycle, thereby sparing vital ATP stores. Although no reliable models of CPB-induced ischemia exist, KTX 0101 is powerfully cytoprotectant under the more severe ischemic conditions of global and focal cerebral ischemia, cardiac ischemia and lung hemorrhage. Neuroprotection has been demonstrated by reductions in infarct volume, edema, markers of apoptosis and functional impairment. One significant difference between KTX 0101 and other potential neuroprotectants in development is that betaOHB is a component of human metabolic physiology which exploits the body's own neuroprotective mechanisms. KTX 0101 also protects hippocampal organotypic cultures against early and delayed cell death in an in vitro model of status epilepticus, indicating that acute KTX 0101 intervention in this condition could help prevent the development of epileptiform foci, a key mechanism in the etiology of intractable epilepsy. In models of chronic neurodegenerative disorders, KTX 0101 protects neurons against damage caused by dopaminergic neurotoxins and by the fragment of beta-amyloid, Abeta(1-42), implying possible therapeutic applications for ketogenic strategies in treating Parkinson's and Alzheimer's diseases. Major obstacles to the use of KTX 0101 for long term therapy in chronic disorders, e.g., Parkinson's and Alzheimer's diseases, are the sodium loading problem and the need to administer it in relatively large amounts because of its rapid mitochondrial metabolism. These issues are being addressed by designing and synthesizing orally bioavailable multimers of betaOHB with improved pharmacokinetics.

Current State of Intraoperative Echocardiography

Intraoperative use of echocardiography is becoming more prevalent and is now considered an essential part of modern cardiac surgery. Echocardiography can be performed intraoperatively using transesophageal, epicardial or epiaortic, and substernal approaches. These techniques have a variety of applications in evaluating myocardial and valvular function, assessing aortic atheroma, and determining adequacy of various kinds of repair and reconstruction. Future applications will most likely involve more compact equipment, the implementation of epicardial and transesophageal real-time three-dimensional echocardiography, and better use of provocative methods of intraoperative testing.

Allogeneic blood transfusion requirements after minimally invasive versus conventional aortic valve replacement: a risk-Adjusted analysis

BACKGROUND

Aortic valve replacement (AVR) through a partial sternotomy (mini-AVR) has been suggested to significantly reduce postoperative morbidity compared with conventional AVR. This study sought to investigate whether mini-AVR patients require fewer transfusions than patients who had conventional AVR.

METHODS

Of 511 patients who had AVR, 56 had mini-AVR and 455 had conventional AVR. A matched-case logistic regression analysis was used to adjust for these imbalances between groups.

RESULTS

No patient in the mini-AVR cohort required conversion to a conventional AVR. Cardiopulmonary bypass time was longer in the mini-AVR group compared with the conventional AVR group, with a median of 102 minutes (range, 78 to 119 minutes) versus 75 minutes (range, 61 to 96 minutes; p < 0.01) in the conventional AVR group. A total of 31 patients (55%) in the mini-AVR group and 336 patients (74%) in the conventional sternotomy group required transfusions during their hospital stay (p < 0.01). After adjusting for differences in preoperative risk factors, year of operation, and surgeon, by matching on propensity score, the differences were not statistically significant (odds ratio = 0.84, 95% confidence interval = 0.40 to 1.75, p = 0.63).

CONCLUSIONS

Mini-AVR produces better wound cosmesis and less surgical trauma but requires more time to perform. Matched-case analysis failed to show a significant difference in blood transfusion requirements after mini-AVR compared with the conventional AVR approach.

Stroke after conventional versus minimally invasive coronary artery bypass

BACKGROUND

Postoperative stroke is a serious complication after coronary artery bypass grafting with cardiopulmonary bypass (on-pump), and portends higher morbidity and mortality. It is unknown whether an off-pump cardiopulmonary bypass (OPCAB) approach may yield a lower stroke rate over conventional on-pump coronary artery bypass grafting.

METHODS

From June 1994 to December 2000, OPCAB was performed in 2,320 patients and compared with 8,069 patients who had on-pump coronary artery bypass grafting, during the same period of time. The patients undergoing OPCAB were randomly matched to on-pump patients by propensity score. A logistic regression model was used to test the difference in the postoperative stroke rate between OPCAB and on-pump procedures controlling for the correlation between matched sets. A multiple logistic regression model predicting the risk of stroke adjusted by stroke risk factors and operation type was also computed.

RESULTS

Matches by propensity score were found for 72% of the patients undergoing OPCAB. Patients undergoing on-pump coronary artery bypass grafting were 1.8 (95% confidence interval 1.0 to 3.1, p = 0.03) times more likely to suffer a stroke postoperatively than OPCAB patients after controlling for preoperative risk factors through matching. Independent predictors of stroke identified from the multiple logistic model included on-pump operation (versus OPCAB operation), female gender, 4 to 6 vessels grafted (versus <4 grafts), hypertension, history of previous cerebrovascular accident, carotid artery disease, chronic obstructive pulmonary disease, and depressed ejection fraction.

CONCLUSIONS

Off-pump cardiopulmonary bypass avoids the risks of cardiopulmonary bypass and atrial trauma. A substantially lower stroke rate suggests that OPCAB is a neurologically safe treatment option for revascularization.

Coronary-artery bypass surgery and the brain: persisting concerns

Mortality after coronary-artery bypass surgery (CABS) has fallen steadily over recent years. Concern remains, however, about the effect of this surgery on the brain. The problem of brain damage after CABS is multifactorial, involving microembolism, disturbed perfusion, metabolic derangement, and inflammatory responses. Microemboli numbers have been linked to the likelihood of neuropsychological deterioration after surgery. Risk factors for cerebral changes after CABS include older age, gender, neurological disease, diabetes, and calcification of the aorta. These risk factors are important because, in comparison with the early 1990s, patients undergoing CABS are now older and tend to have a greater number of comorbid conditions. Changes in surgical technique, such as the introduction of arterial-line filters and membrane oxygenators, have led to a reduction of both microemboli and neuropsychological disturbance. However, the problem persists, prompting further studies on surgical technique and neuroprotective strategies.

Stroke after coronary artery bypass: incidence, predictors, and clinical outcome

BACKGROUND AND PURPOSE

Early postoperative stroke is a serious adverse event after coronary artery bypass grafting (CABG). This study sought to investigate risk factors, prevalence, and prognostic implications of postoperative stroke in patients undergoing CABG.

METHODS

We investigated the predictors of postoperative stroke (n=333, 2%) in 16 528 consecutive patients who underwent CABG between September 1989 and June 1999 in our institution. Predictors of postoperative stroke were identified by logistic regression analysis.

RESULTS

Among the preoperative and postoperative factors, significant correlates of stroke included (1) chronic renal insufficiency (P<0.001), (2) recent myocardial infarction (P=0.01), (3) previous cerebrovascular accident (P<0.001), (4) carotid artery disease (P<0.001), (5) hypertension (P<0.001), (6) diabetes (P=0.001), (7) age >75 years (P=0.008), (8) moderate/severe left ventricular dysfunction (P=0.01), (9) low cardiac output syndrome (P<0.001), and (10) atrial fibrillation (P<0.001). Postoperative stroke was associated with longer postoperative stay (11+/-4 versus 7+/-3 days for patients without stroke, P<0.001) and with higher in-hospital mortality (14% versus 2.7% for patients without stroke; P<0.001).

CONCLUSIONS

Stroke after CABG is associated with high short-term morbidity and mortality. Increased stroke risk can be predicted by preoperative and postoperative clinical factors.

Stroke during coronary bypass surgery: principal role of cerebral macroemboli

OBJECTIVE

The purpose of this study was to gain insight into the etiology of stroke during coronary bypass surgery.

METHODS

Retrospective review of prospectively gathered data on 6682 consecutive coronary bypass patients. Patients undergoing simultaneous procedures, including carotid endarterectomy, were excluded. We performed a systematic chart review of all patients who suffered a perioperative stroke. Predictors of stroke were determined with stepwise logistic regression analysis.

RESULTS

The prevalence of stroke was 1.5% (n=98). Stroke patients had significantly increased intensive care unit and hospital length of stays, as well as increased mortality when compared to patients without stroke (all P< 0.001). Independent predictors of stroke were (in decreasing order of magnitude): age >70 years, left ventricular ejection fraction <40%, previous stroke or transient ischemic attack, normothermic cardiopulmonary bypass, diabetes, and peripheral vascular disease. Chart review revealed that the probable cause of stroke was macroemboli, likely from ascending aorta atherosclerosis, in 37% of patients and unknown in 38% of patients. Computerized tomography (CT) scans were obtained in 79 patients (81%). Lesions detected by CT were consistent with a macroembolic etiology: nearly all lesions were ischemic in nature and located in the distribution of major cerebral arteries, particularly the middle cerebral artery.

CONCLUSIONS

Stroke is a devastating complication of coronary bypass surgery. Our multivariable risk factors for stroke, chart review, and CT findings all suggest that macroemboli, presumably from the ascending aorta, are the predominant cause of stroke during coronary bypass surgery. Future studies should be directed at minimizing the risk of embolization during cardiac surgery.

Cerebral infarction complicating Fontan surgery for cyanotic congenital heart disease

We report on four children who had cerebral vascular events in the first three months after the Fontan procedure for complex cyanotic congenital heart disease. Potential risk factors in these children included congestive heart failure, postoperative thrombocytosis, and cardiac arrhythmias. These cases suggest that children who undergo Fontan surgery may be at increased risk for cerebral infarction.

Coronary artery bypass performed without the use of cardiopulmonary bypass is associated with reduced cerebral microemboli and improved clinical results

STUDY OBJECTIVES

Strokes and neurocognitive dysfunction have been correlated with cerebral microemboli produced during cardiopulmonary bypass (CPB). The purpose of this study was to determine whether, and to what extent, off-pump coronary artery bypass (OPCAB) reduces the occurrence of cerebral microemboli compared with traditional coronary artery bypass grafting (CABG) with CPB and to compare clinical results.

DESIGN AND PATIENTS

A retrospective review of 137 patients undergoing elective CABG was performed, 70 of whom underwent traditional CABG and 67 of whom underwent OPCAB. Using transcranial Doppler ultrasonography, 40 patients (20 CABG, 20 OPCAB) were continuously monitored intraoperatively for the occurrence and pattern of cerebral microemboli.

SETTING

Private, university-affiliated tertiary care hospitals.

RESULTS

There was no statistical difference in the age, sex, or underlying comorbidities between those patients undergoing CABG and OPCAB. CABG patients did have a slightly lower preoperative ejection fraction (50.9% vs 55.5%, p = 0.03). Despite these similar preoperative characteristics, the OPCAB group experienced significant reductions in cerebral microemboli (27 vs 1,766, p = 0.003), transfusion requirements (29.9% vs 47.1%, p = 0.04), intubation time (3.3 vs 9.5 h, p < 0.001), ICU length of stay (1.5 vs 2.8 days, p = 0.02), and overall hospitalization (4.9 vs 6.6 days, p = 0.01) without an increase in mortality. Fewer strokes and deaths were observed in the OPCAB group, but these trends failed to reach statistical significance.

CONCLUSIONS

In similar patient populations, OPCAB was associated with significantly fewer cerebral microemboli and improved clinical results without an increase in mortality. We believe that these early results support OPCAB as a viable and potentially safer alternative to traditional CABG.

Neurologic complications of cardiac surgery

The average age of patients undergoing cardiac surgery and the number of comorbidities they possess will continue to increase as surgical technology advances. Toxic/metabolic encephalopathy, hemispheric strokes, hypoxic injury, and peripheral nerve lesions all can occur as a result of cardiac surgery. Therefore, an understanding of the neurologic risk, recognizable syndromes, and preventative measures will continue to be important. Careful preoperative assessment, operative risk factor reduction, and careful postoperative assessments and management may reduce the neurologic risk for cardiac surgery.