Coronary-artery bypass surgery and the brain

Cognitive Performance Among Older Persons in Japan and the United States

OBJECTIVE

To compare cognitive performance among Japanese and American persons, aged 68 years and older, using two nationally representative studies and to examine whether differences can be explained by differences in the distribution of risk factors or in their association with cognitive performance.

DESIGN

Nationally representative studies with harmonized collection of data on cognitive functioning.

SETTING

Nihon University Japanese Longitudinal Study of Aging and the US Health and Retirement Study.

PARTICIPANTS

A total of 1953 Japanese adults and 2959 US adults, aged 68 years or older.

MEASUREMENTS

Episodic memory and arithmetic working memory are measured using immediate and delayed word recall and serial 7s.

RESULTS

Americans have higher scores on episodic memory than Japanese people (0.72 points on a 20-point scale); however, when education is controlled, American and Japanese people did not differ. Level of working memory was higher in Japan (0.36 on a 5-point scale) than in the United States, and the effect of education on working memory was stronger among Americans than Japanese people. There are no differences over the age of 85 years.

CONCLUSION

Even with large differences in educational attainment and a strong effect of education on cognitive functioning, the overall differences in cognitive functioning between the United States and Japan are modest. Differences in health appear to have little effect on national differences in cognition. J Am Geriatr Soc 68:354-361, 2020.

[Neurological aspects of chronic heart failure]

Chronic heart failure (CHF) is one of the leading causes of hospitalization, morbidity and mortality. Moreover, there is a high rate of neurological as well as neuropsychological comorbidities, namely ischemic stroke, structural brain alterations, cognitive impairment, sleep apnea and possible side-effects of HF medication such as delirium or (intracerebral) hemorrhage. The higher stroke risk in patients with HF increases further with age, concomitant arterial hypertension or atrial fibrillation (AF). In women the stroke risk increases with reduced ejection fraction (EF). In general stroke in HF patients is associated with a poor outcome and higher mortality, which is increased more than 2-fold. Furthermore, approximately 25-80% of all patients with CHF experience cognitive impairments such as decreased attention and concentration, memory loss, diminished psychomotor reaction time and decreased executive functions. Cognitive impairment in patients with HF has been linked to losses in gray matter, (silent) ischemic strokes, decreased cerebral perfusion and higher mortality. Moreover, sleep apnea occurs in more than half of all patients with CHF and reduced EF. However, prospective studies are needed to test whether early detection and optimal treatment of HF reduces the burden of neurological and neuropsychological sequelae.

Antithrombotic medication for cardioembolic stroke prevention

Embolism of cardiac origin accounts for about 20% of ischemic strokes. Nonvalvular atrial fibrillation is the most frequent cause of cardioembolic stroke. Approximately 1% of population is affected by atrial fibrillation, and its prevalence is growing with ageing in the modern world. Strokes due to cardioembolism are in general severe and prone to early recurrence and have a higher long-term risk of recurrence and mortality. Despite its enormous preventive potential, continuous oral anticoagulation is prescribed for less than half of patients with atrial fibrillation who have risk factors for cardioembolism and no contraindications for anticoagulation. Available evidence does not support routine immediate anticoagulation of acute cardioembolic stroke. Anticoagulation therapy's associated risk of hemorrhage and monitoring requirements have encouraged the investigation of alternative therapies for individuals with atrial fibrillation. New anticoagulants being tested for prevention of stroke are low-molecular-weight heparins (LMWH), unfractionated heparin, factor Xa inhibitors, or direct thrombin inhibitors like dabigatran etexilate and rivaroxaban. The later exhibit stable pharmacokinetics obviating the need for coagulation monitoring or dose titration, and they lack clinically significant food or drug interaction. Moreover, they offer another potential that includes fixed dosing, oral administration, and rapid onset of action. There are several concerns regarding potential harm, including an increased risk for hepatotoxicity, clinically significant bleeding, and acute coronary events. Therefore, additional trials and postmarketing surveillance will be needed.

Acute respiratory distress syndrome, sepsis, and cognitive decline: a review and case study

The objective of this investigation is to review existing research pertaining to cognitive impairment and decline following critical illness and describe a case involving a 49-year-old female with sepsis and acute respiratory distress syndrome (ARDS) with no prior neurologic history who, compared to baseline neuropsychological test data, experienced dramatic cognitive decline and brain atrophy following treatment in the medical intensive care unit (ICU) at Vanderbilt University Medical Center. The patient participated in detailed clinical interviews and underwent comprehensive neuropsychological testing and neurological magnetic resonance imaging (MRI) at approximately 8 months and 3.5 years after ICU discharge. Compared to pre-ICU baseline test data, her intellectual function declined approximately 2 standard deviations from 139 to 106 (from the 99 to the 61 percentile) on a standardized intelligence test 8 months post-discharge, with little subsequent improvement. Initial diffusion tensor brain magnetic resonance imaging (DT-MRI) at the end of ICU hospitalization showed diffuse abnormal hyperintense areas involving predominately white matter in both hemispheres and the left cerebellum. A brain MRI nearly 4 years after ICU discharge demonstrated interval development of profound and generalized atrophy with sulcal widening and ventricular enlargement. The magnitude of cognitive decline experienced by ICU survivors is difficult to quantify due to the unavailability of pre-morbid neuropsychological data. The current case, conducted on a patient with baseline neuropsychological data, illustrates the trajectory of decline occurring after critical illness and ICU-associated brain injury with marked atrophy and concomitant cognitive impairments.

Pathophysiology of delirium in the intensive care unit

Delirium, or acute brain dysfunction, is a life-threatening global disturbance in cognitive functioning that frequently manifests in critically ill patients. This review examines the current status of knowledge regarding the pathophysiology of delirium in the ICU, in particular, evaluating the role of iatrogenic factors such as sedatives and analgesic administration in brain dysfunction. This hypothesis is considered along with several other plausible mechanisms of ICU delirium, including sepsis, postoperative cognitive dysfunction, and changes in biomarkers and neurotransmitters. The review concludes by highlighting potential future directions in molecular genetics for the elucidation of delirium and its long-term consequences.

NMDA Receptor Antibodies Predict Adverse Neurological Outcome After Cardiac Surgery in High-Risk Patients

Background and Purpose— The goal of this study was to compare the predictive ability of S100B, N -methyl- d -aspartate (NMDA) receptor antibodies (NR2Ab) and C-reactive protein (CRP) for neurological deficits after cardiac surgery with cardiopulmonary bypass (CPB).

Methods— We investigated 557 high-risk adult patients who underwent coronary artery or valve replacement surgery using CPB as a substudy of a prospective, blinded, multicenter clinical trial. Serum concentrations of S100B (n=513 patients), NR2Ab (n=398) and CRP (n=510) were measured preoperatively, 24 and 48 hours after CPB. Neurological adverse events were assessed at baseline and postoperative days 1 and 2; neurocognitive function (mini-mental status examination) was assessed at baseline and on postoperative days 1, 7 and 28.

Results— Fifty-five (9.9%) patients had moderate or severe neurological adverse events (confusion/delirium, transient ischemic attack, or stroke) within 48 hours of CPB. Women had significantly more neurological complications than men (15.5% versus 7.8%; P =0.007). Ninety-six percent (24/25) of patients with NR2Ab concentrations ≥2.0 ng/mL preoperatively had neurological complications within 48 hours post-CPB, versus only 5.4% (20/373) of patients with NR2Ab concentrations <2.0 ng/mL, resulting in a 17.9-fold increase (95% CI, 11.6 to 27.6) in postoperative neurological complications for patients with high levels of NR2A antibodies. Preoperative serum S100B and CRP did not predict neurological complications from CPB. Decreased mini-mental status examination scores for orientation, attention and recall were associated with neurological adverse events early after CPB.

Conclusions— Preoperative serum concentrations of NR2Ab, but not S100B or CRP, are predictive of severe neurological adverse events after CPB. Patients with a positive NR2Ab test (≥2.0 ng/mL) preoperatively were nearly 18 times more likely to experience a postoperative neurological event than patients with a negative test (<2.0 ng/mL).

Limiting brain and lung damage after coronary artery bypass grafting: an alternative to conventional coronary artery bypass graft

The development of coronary artery bypass graft (CABG) for the treatment of coronary heart disease has resulted in reduced morbidity and mortality compared with medical therapy. Even with the rapid development of improved percutaneous interventions, CABG remains an important approach for treating patients with advanced coronary heart disease. However, recent studies and commentary reporting an alarmingly high incidence of subtle, cognitive decline following CABG have generated questions about whether these adverse outcomes could be lessened. Even after considerable study, there is no consensus as to the cause of brain and lung injury after CABG and cardiopulmonary bypass, nor an agreed upon, mechanistic approach to study its prevention. The potential causes of these adverse outcomes and a simple approach are described, involving the use of the cannulae, biventricular pulsatile flow pump, and a blood substitute to optimize the perfusion of brain and alveolar cells, minimize systemic microembolization, and limit post-CABG cognitive decline.

Psychiatric and psychosocial outcome of cardiac surgery with cardiopulmonary bypass: a prospective 12-month follow-up study

Little is known concerning the natural history of psychiatric morbidity, postoperative delirium, cognitive decline and health-related quality of life (HRQOL) in cardiac surgery patients and the impact of neurocognitive dysfunction on HRQOL after cardiac surgery with cardiopulmonary bypass (CPB). In a prospective study, we followed up for 1 year 30 of the original 34 patients who had undergone cardiac surgery with CPB. Patients were assessed preoperatively, before discharge, and at 1 year after surgery with the Structural Clinical Interview for DSM-IV and a series of neuropsychological tests. Psychometric scales were administered to evaluate cognitive functioning (Syndrom Kurztest), depressive symptomatology (Montgomery-Asberg Depression Rating Scale), posttraumatic stress symptoms (Posttraumatic Stress Syndrome 10-Questions Inventory) and HRQOL (SF-36 Health Status Questionnaire). Delirium Rating Scale (DRS) was used daily over the course of intensive care unit treatment. Postoperative delirium developed in 11 of the 34 patients (mean DRS rating scale score+/-S.D.: 20.36+/-6.22, range: 14-31). Short-term consequences of cardiac surgery included adjustment disorder with depressed features (n=11), posttraumatic stress disorder (n=6), major depression (n=6) and clinically relevant cognitive deficits (n=13). At 12 months, the severity of depression and anxiety disorders improved and returned to the preoperative level, and 6 out of the 30 followed-up patients displayed cognitive deficits. Our patients' HRQOL SF-36 self-reports significantly improved compared with baseline quality of life data. However, 1-year overall lower cognitive function scores were associated with lower HRQOL. Cardiac surgery with CPB is associated with improvements in HRQOL relative to the preoperative period, but the presence of cardiac surgery-related cognitive decline impairing HRQOL is a complication for a subgroup of cardiac surgical patients in the long-term outcome.

Neurologic Injury Associated with CABG Surgery: Outcomes, Mechanisms, and Opportunities for Improvement

Neurologic injuries, whether subtle or overt, are a major source of morbidity secondary to coronary artery bypass graft (CABG) surgery. A comprehensive review of research in the area of neurologic injury is provided. We conclude this article by providing insight regarding areas requiring further investigation in order to reduce sustainably the risk of these iatrogenic events among patient undergoing CABG surgery.

Perioperative management of patients with neurologic disease

Because many of the perioperative problems of the neurologic patient are predictable, they should be anticipated by the neurologist so that measures can be taken to prevent as many complications as possible and to recognize and manage those that cannot be prevented in a timely, efficient manner.

Mechanisms of Disease: The Blood-Brain Barrier

OBJECTIVE

The blood-brain barrier (BBB) is often perceived as a passive membrane. However, evidence has demonstrated that the BBB plays an active role in normal homeostasis and in certain disease processes.

METHODS

Approximately 300 peer-reviewed publications that discussed normal or abnormal BBB function were reviewed.

RESULTS

The role of the BBB and how it contributes to disorders of the central nervous system vary, depending on the specific disease process.

CONCLUSION

In health and disease and extending to old age, endothelial cells, neurons, and glia constitute a neurovascular unit that regulates the BBB. Advances toward penetrating the BBB must account for both normal and abnormal functions of the neurovascular unit.

Cerebral cortical oxygenation changes during OPCAB surgery

BACKGROUND

We investigated the changes occurring in cerebral cortical oxygenation during off-pump coronary artery bypass (OPCAB) surgery using near infrared spectroscopy (NIRS).

METHODS

Measurement of cerebral cortical oxygenation changes included concentration of deoxygenated hemoglobin [HHb], oxygenated hemoglobin [O(2)Hb], changes in the redox status of the cytochrome c oxidase [Cyt-Ox], cerebral saturation as expressed by the tissue oxygenation index (TOI), and cerebral blood volume (CBV) as expressed by tissue hemoglobin index (THI). Measurements were performed in 23 consecutive patients during grafting of: left anterior descending (LAD setup 1; n = 23), posterior descending (PDA setup 2; n = 17), and Circumflex (Cx setup 3; n = 19) coronary arteries. Measurements were performed before any surgical manipulation (baseline), following positioning of the pressure stabilizer during construction of the distal anastomosis and 2 minutes after the completion of each distal anastomosis with the heart returned to its natural position.

RESULTS

There were no in-hospital deaths, neurologic deficits, or myocardial infarcts. Compared to baseline, during LAD grafting there was a marked reduction in [O(2)Hb] [-1.08 (-1.77 to -0.39), mean difference (95% CI) (p < 0.0008)], without a significant change in [HHb]. There was also a 4% reduction in cerebral saturation and a 3% fall in CBV (both p < 0.05). Setup 2 (PDA) was associated with a marked decrease of [O(2)Hb] [-1.92 (-2.95 to -0.88) mean difference (95% CI) (p < 0.0025)], which was accompanied by an increase in [HHb] [1.89 (1.00 to 2.77) mean difference (95% CI) (p < 0.0025)], and a 4% reduction in cerebral saturation (p < 0.0008). Grafting of the Cx was associated with a marked increase in [HHb] [2.85 (1.46 to 4.2) mean difference (95% CI) (p < 0.0025)], with no changes in [O(2)Hb], a 6% reduction in cerebral saturation, and a 12% increase in CBV (both p < 0.05). In all 3 settings, however, the changes were not associated with a modification in the redox state of [Cyt-Ox]. On returning to baseline condition, the changes in [O(2)Hb] and TOI observed in setup 1 persisted, and a significant reduction was observed in the redox state of the [Cyt-Ox] when compared with baseline [-0.08 (-0.14 to -0.02) mean difference (95% CI) (p < 0.002)]. For setups 2 and 3 there was recovery of the cerebral cortical oxygenation.

CONCLUSIONS

Grafting of the LAD on the beating heart is responsible for changes in cerebral cortical oxygenation which persist early after returning the heart to its natural position. Grafting of the Cx and PDA result in transient reversible changes. Trendelenburg positioning and right lateral tilting of the operating table during grafting of lateral and posterior walls might have a protective role in preventing cerebral cortical ischemia. Further studies are needed to assess the clinical importance of these observations.

Reversal of the direction of internal carotid artery blood flow by occlusion of the common and external carotid arteries in a swine model

In a swine model, blood flow direction [antegrade (+) and retrograde (-)] and velocity were defined within the common (CCA), internal (ICA), and external (ECA) carotid arteries during CCA occlusion with and without ECA occlusion and blood aspiration. In seven anesthetized swine, Doppler recordings of blood flow direction and velocity were performed in the CCA, ICA, and ECA, before and after vessel(s) occlusion, and after passively and actively induced reversal of blood flow direction. Baseline ICA and ECA blood flow direction and velocities were 92 +/- 4 and 90 +/- 3 cm/sec; and, with CCA occlusion, the ICA velocity decreased to 30 +/- 2 cm/sec (P < 0.001). No flow (zero velocity) occurred with CCA and ECA occlusion. An artificial femoral arteriovenous fistula's continuous gradient passively reversed ICA blood flow direction (-), with the recorded blood's velocity (-24 +/- 4 cm/sec) increasing with continuous active aspiration to -90 +/- 6 cm/sec. Occlusion of the CCA occlusion alone was unable completely to halt ICA antegrade blood flow direction, while CCA and ECA occlusion completely stopped ICA antegrade flow. CCA and ECA occlusion, when coupled with an arteriovenous fistula arteriovenous and/or aspiration, resulted in ICA blood flow direction reversal, whose velocity could be actively augmented.

Reduced rate of microembolism by optimized aortic cannula position does not influence early postoperative cognitive performance in CABG patients

BACKGROUND AND PURPOSE

The number of microemboli as measured by Doppler ultrasound during coronary artery bypass grafting (CABG) can be reduced by positioning the arterial cannula into the aorta descendens. The aim of this study was to prospectively evaluate whether this alternative aortic cannulation procedure leads to better neuropsychologic outcome early after surgery along with embolus reduction.

METHODS

Sixty patients with elective CABG were randomized to either using a short aorta ascendens cannula or an elongated cannula placed in the aorta descendens. All patients were tested by seven neuropsychologic tests preoperatively. Intraoperative embolus detection could be performed by transcranial Doppler in 32 patients. The neuropsychologic tests could be repeated serially until the 9th postoperative day in 54 patients. Patient groups did not differ in terms of preoperative psychometric performance and of the surgical characteristics except cannula positioning. All data were analyzed by a blinded assessor.

RESULTS

Neuropsychologic test scores showed in all individual patients a transient decline with subsequent recovery, but did not differ significantly between the groups except for the letter cancellation test at discharge favoring the patients with the longer cannula (102.3 +/- 11.6 vs. 94.5 +/- 11.5 mean +/- SD; p = 0.025). In the subgroup who had Doppler sonography, neuropsychologic test scores did not differ between the groups. However, microembolic signals were markedly reduced in patients with the elongated cannula (median 174.5 vs. 413.0; p = 0.011).

CONCLUSIONS

Though reducing brain microembolism, use of an elongated aortic cannula does not appear to influence overall cognitive performance early after CABG in this pilot study.

Subsystem organ function during coronary surgery

Conventional coronary artery bypass grafting (CABG) carries a mortality rate of 1% to 2% in elective patients. However, despite advances in perfusion, anaesthetic, and surgical techniques cardiopulmonary bypass (CPB) is still associated with subsystem dysfunction. Off-pump coronary artery bypass grafting (OPCAB) has recently gained popularity as a potentially more physiological method to maintain the functional integrity of major organ systems. The review of observational reports, case-matched studies and prospective randomized trials seems to suggest that OPCAB surgery reduces postoperative subsystem organ dysfunction when compared with conventional coronary revascularisation.

Report of the substudy assessing the impact of neurocognitive function on quality of life 5 years after cardiac surgery

BACKGROUND AND PURPOSE

The importance of perioperative cognitive decline has long been debated. We recently demonstrated a significant correlation between perioperative cognitive decline and long-term cognitive dysfunction. Despite this association, some still question the importance of these changes in cognitive function to the quality of life of patients and their families. The purpose of our investigation was to determine the association between cognitive dysfunction and long-term quality of life after cardiac surgery.

METHODS

After institutional review board approval and patient informed consent, 261 patients undergoing cardiac surgery with cardiopulmonary bypass were enrolled and followed for 5 years. Cognitive function was measured with a battery of tests at baseline, discharge, and 6 weeks and 5 years postoperatively. Quality of life was assessed with well-validated, standardized assessments at the 5-year end point.

RESULTS

Our results demonstrate significant correlations between cognitive function and quality of life in patients after cardiac surgery. Lower 5-year overall cognitive function scores were associated with lower general health and a less productive working status. Multivariable logistic and linear regression controlling for age, sex, education, and diabetes confirmed this strong association in the majority of areas of quality of life.

CONCLUSIONS

Five years after cardiac surgery, there is a strong relationship between neurocognitive functioning and quality of life. This has important social and financial implications for preoperative evaluation and postoperative care of patients undergoing cardiac surgery.

Importance of risk communication and decision making in cardiovascular conditions in older patients: a discussion paper

Atrial fibrillation and aortic stenosis commonly present doctors and patients with difficult decisions about the risks and benefits of treatment options and are both often inappropriately undertreated. Patients may be confused by risk information and doctors may be aware of patients' limitations and use this to manipulate choices to the ones desired by the doctors. This paper examines the importance of risk communication and discusses difficulties that can arise in decision making in these two common cardiovascular conditions.