Cerebral oxygenation in wake and during sleep and its relationship to cognitive function in community-dwelling older adults without sleep disordered breathing

Erythrocytes Functionality in SARS-CoV-2 Infection: Potential Link with Alzheimer's Disease

Coronavirus disease 2019 (COVID-19) is a rapidly spreading acute respiratory infection caused by SARS-CoV-2. The pathogenesis of the disease remains unclear. Recently, several hypotheses have emerged to explain the mechanism of interaction between SARS-CoV-2 and erythrocytes, and its negative effect on the oxygen-transport function that depends on erythrocyte metabolism, which is responsible for hemoglobin-oxygen affinity (Hb-O2 affinity). In clinical settings, the modulators of the Hb-O2 affinity are not currently measured to assess tissue oxygenation, thereby providing inadequate evaluation of erythrocyte dysfunction in the integrated oxygen-transport system. To discover more about hypoxemia/hypoxia in COVID-19 patients, this review highlights the need for further investigation of the relationship between biochemical aberrations in erythrocytes and oxygen-transport efficiency. Furthermore, patients with severe COVID-19 experience symptoms similar to Alzheimer's, suggesting that their brains have been altered in ways that increase the likelihood of Alzheimer's. Mindful of the partly assessed role of structural, metabolic abnormalities that underlie erythrocyte dysfunction in the pathophysiology of Alzheimer's disease (AD), we further summarize the available data showing that COVID-19 neurocognitive impairments most probably share similar patterns with known mechanisms of brain dysfunctions in AD. Identification of parameters responsible for erythrocyte function that vary under SARS-CoV-2 may contribute to the search for additional components of progressive and irreversible failure in the integrated oxygen-transport system leading to tissue hypoperfusion. This is particularly relevant for the older generation who experience age-related disorders of erythrocyte metabolism and are prone to AD, and provide an opportunity for new personalized therapies to control this deadly infection.

Cerebral Hypoxia: Its Role in Age-Related Chronic and Acute Cognitive Dysfunction

Postoperative cognitive dysfunction (POCD) has been reported with widely varying frequency but appears to be strongly associated with aging. Outside of the surgical arena, chronic and acute cerebral hypoxia may exist as a result of respiratory, cardiovascular, or anemic conditions. Hypoxia has been extensively implicated in cognitive impairment. Furthermore, disease states associated with hypoxia both accompany and progress with aging. Perioperative cerebral hypoxia is likely underdiagnosed, and its contribution to POCD is underappreciated. Herein, we discuss the various disease processes and forms in which hypoxia may contribute to POCD. Furthermore, we outline hypoxia-related mechanisms, such as hypoxia-inducible factor activation, cerebral ischemia, cerebrovascular reserve, excitotoxicity, and neuroinflammation, which may contribute to cognitive impairment and how these mechanisms interact with aging. Finally, we discuss opportunities to prevent and manage POCD related to hypoxia.

Association Among Preoperative Cognitive Performance, Regional Cerebral Oxygen Saturation, and Postoperative Delirium in Older Portuguese Patients

BACKGROUND

Postoperative delirium is common among older patients and preoperative identification of high-risk patients is widely recommended. The aim of this study was to assess whether preoperative cognitive performance using brief screening tools or regional cerebral oxygen saturation (Scto2) was associated with the development of postoperative delirium in older Portuguese patients undergoing elective surgery.

METHODS

Prospective observational cohort study where preoperative cognitive screening tools (Mini-Cog, Mini-Mental State Examination, verbal fluency) and Scto2 (INVOS 5100C; Medtronic, Ireland) were assessed in 238 patients ≥65 years old undergoing elective surgery between July 2017 and May 2019 at a tertiary academic center in Portugal. The primary outcome was postoperative delirium detected by the 3D-Confusion Assessment Method. Data were analyzed by univariate analysis and multivariable logistic regression.

RESULTS

Delirium was identified in 53 patients (22%); 162 patients (68%) had completed only 4 years of education. On multivariable analysis, probable cognitive impairment tested by the Mini-Cog (odds ratio [OR] = 1.57; 95% confidence interval [CI], 0.70-3.53; corrected P value >.999), by the Mini-Mental State Examination (OR = 2.75; 95% CI, 1.23-6.13; corrected P value = .052), and by the animal verbal fluency test (OR = 1.24; 95% CI, 0.49-3.16; corrected P value >.999) were not significantly associated with the development of postoperative delirium. In contrast, lower preoperative Scto2 (OR = 1.08; 95% CI, 1.02-1.14; corrected P value = .024 for each point decrease in Scto2) was associated with postoperative delirium.

CONCLUSIONS

We did not find enough evidence to suggest that poor preoperative cognitive performance was significantly associated with the development of postoperative delirium in an older Portuguese surgical population with an overall low level of formal education, but rather that preoperative Scto2 may be helpful in identifying patients at risk for delirium.

Effects of bupivacaine or levobupivacaine on cerebral oxygenation during spinal anesthesia in elderly patients undergoing orthopedic surgery for hip fracture: a randomized controlled trial

BACKGROUND

Bupivacaine and levobupivacaine have similar pharmacokinetic and pharmacodynamic characteristics, and are used regularly in spinal anesthesia. Whether potential differences in their hemodynamic and anesthetic profiles could determine a differential risk of complications in elderly subjects, is controversial. The main objective was to compare the effects of intrathecally administered levobupivacaine (LB) versus bupivacaine (B), on regional cerebral O2 saturation during spinal anesthesia, cognitive status and neurological complications in elderly patients undergoing surgery for hip fracture.

METHODS

This was a randomized, controlled, single blind study. 58 patients aged 70 or older undergoing surgery for hip fracture with spinal anesthesia were allocated with a 1:1 ratio to receive LB or B, combined with fentanyl 15 μg, by intrathecal route. The primary outcome was the proportion of intraoperative time with regional cerebral desaturation (≥20% reduction in regional cerebral oxygen saturation from baseline), monitored by near -infrared spectroscopy. Secondary endpoints included hemodynamic parameters, level of sensory and motor block, changes in Short Portable Mental Status Questionnaire (SPMSQ), and neurological complications.

RESULTS

The mean percentage of intraoperative time with desaturation in the B group was 6.1% (SD: 17.5) and 4.7% (SD: 11.9) in the left and right hemisphere respectively; in the LB group the mean was 4.8% (SD: 11.4) in the left hemisphere and 2.4% (SD: 8.3) in the right one. No statistically significant differences were found between treatment groups. The level of sensory block at the start of surgery was lower for LB than for B (Th10 vs Th8, p:0.047) and motor block at 15 min was lower for LB (2.5 vs 3, p:0.009). No differences in postoperative SPMSQ were observed. Neurological complications such as confusional state, agitation or disorientation were reported in 50% of patients in the B group and 21.4% of patients in the LB group, p = 0.05.

CONCLUSIONS

No statistically significant differences in regional cerebral oxygen saturation or hemodynamic parameters were observed between both treatment groups. Bupivacaine and levobupivacaine differed in sensory and motor block achieved. While no differences were observed in cognitive impairment measured by the SPMSQ between treatment groups neurological complications reported by the physician were more frequent with bupivacaine.

TRIAL REGISTRATION

European Union Clinical Trials Register ( EudraCT 2013-000846 -20 ) (April 9th, 2013). ClinicalTrials.gov ( NCT01960543 ) (September 23rd, 2013).

The relative effects of dexmedetomidine and propofol on cerebral blood flow velocity and regional brain oxygenation: A randomised noninferiority trial

BACKGROUND

Dexmedetomidine constricts cerebral blood vessels without a concomitant reduction in cerebral metabolic oxygen consumption. Its safety as a sedative in patients with neurological diseases thus remains uncertain.

OBJECTIVE

Our primary objective was to test the hypothesis that dexmedetomidine is noninferior to propofol as regards cerebral blood flow (CBF) velocity and brain oxygenation.

DESIGN

Unblinded randomised trial.

SETTING

Cleveland Clinic Hospital, Cleveland, from November 2010 to July 2013.

PATIENTS

Forty-four patients scheduled for insertion of a deep-brain stimulating electrodes.

INTERVENTIONS

Patients were randomised to receive either dexmedetomidine or propofol sedation during deep-brain stimulating electrode insertion.

MAIN OUTCOME MEASURES

Intraoperative CBF velocity was measured with transcranial Doppler, and brain oxygenation was assessed with near-infrared spectroscopy. Noninferiority of dexmedetomidine to propofol was defined as a less than 20% difference in means.

RESULTS

Twenty-three patients were given dexmedetomidine and 21 propofol. Baseline characteristics and operative management were similar in each group. Dexmedetomidine was noninferior to propofol on both CBF and brain oxygenation, confirming our primary hypothesis. For cerebral flood flow, the estimated ratio of means (dexmedetomidine/propofol) was 0.94 [90% CI: 0.84 to 1.05], P = 0.011 for noninferiority. For brain oxygenation, the estimated ratio of means was 0.99 [90% CI: 0.96 to 1.02], P < 0.001 for noninferiority. Superiority was not found for either primary outcome. Dexmedetomidine provided deeper sedation than propofol, with a difference of medians of 1 [90% CI: 0 to 2], P < 0.001 on the Observer's Assessment of Alertness/Sedation scale. No significant differences were observed in pulsatility index, cerebral perfusion pressure, number of hypertensive or apnoeic episodes.

CONCLUSION

Regional brain oxygenation and CBF velocity are comparably preserved during dexmedetomidine and propofol sedation. Thus, the use of dexmedetomidine in patients with movement disorders appears reasonable.

TRIAL REGISTRATION

The trial was registered at ClinicalTrials.gov (NCT 01200433).

Is baseline cerebral oximetry a better predictor than carotid scan for postoperative delirium in cardiac surgery?

Guidelines recommend screening patients for carotid-artery stenosis, but unfortunately, measurement of baseline cerebral oximetry levels is still not a routine practice prior to cardiac surgery. We report a 41-year-old woman who presented with a normal carotid scan and unexpectedly low baseline cerebral oximetry levels. She had delayed postoperative recovery and discharge from hospital following her coronary-artery bypass surgery. This case report reiterates the prognostic significance of cerebral oximetry in the preoperative checkup and the association of low intraoperative values to postoperative cerebral impairment. It can also be identified as a comparatively better tool for preventing cognitive disturbances after cardiac surgery.

Prevalence and risk factors for postoperative delirium in total joint arthroplasty patients: A prospective study

BACKGROUND

The aim of this prospective study was to investigate the incidence and clinical features of delirium after total joint arthroplasty, and to establish the potential risk factors for postoperative delirium.

METHODS

A total of 212 consecutive patients undergoing hip or knee arthroplasty, who met the inclusion and exclusive criteria were enrolled. The general characteristics, preoperative and postoperative hematological variables were documented respectively. According to the presence of delirium, all patients were divided into the delirium group and non-delirium group. Univariate and multivariate logistic regression were performed to identify the possible predictors for postoperative delirium.

RESULTS

At a minimum of 6months of follow-up, 35 patients were observed with postoperative delirium at an estimated total incidence of 16.5%. The incidence of delirium was statistically higher in hip arthroplasty (22.8%) than that in knee arthroplasty (7.1%). The multivariate regression analysis identified older age (OR=1.590, P=0.023), a history of stroke (OR=190.23, P=0.036), preoperative PaO₂ (OR=1.277, P=0.018) and equivalent fentanyl dose (OR=1.010, P=0.012) as the predictive factors for postoperative delirium after total joint arthroplasty.

CONCLUSIONS

The incidence of postoperative delirium after total joint arthroplasty is higher than expected. Based on our findings, we suggest that the surgeons should focus on those patients who have these risk factors and ensure the appropriate management to avoid postoperative delirium.

Transcranial doppler and near infrared spectroscopy in the perioperative period

PURPOSE OF REVIEW

Maintenance of adequate blood flow and oxygen to the brain is one of the principal endpoints of all surgery and anesthesia. During operations in general anesthesia, however, the brain is at particular risk for silent ischemia. Despite this risk, the brain still remains one of the last monitored organs in clincial anesthesiology.

RECENT FINDINGS

Transcranial Doppler (TCD) sonography and near-infrared spectroscopy (NIRS) experience a revival as these noninvasive technologies help to detect silent cerebral ischemia. TCD allows for quantification of blood flow velocities in basal intracranial arteries. TCD-derived variables such as the pulsatility index might hint toward diminished cognitive reserve or raised intracranial pressure. NIRS allows for assessment of regional cerebral oxygenation. Monitoring should be performed during high-risk surgery for silent cerebral ischemia and special circumstances during critical care medicine. Both techniques allow for the assessment of cerebrovascular autoregulation and individualized management of cerebral hemodynamics.

SUMMARY

TCD and NIRS are noninvasive monitors that anesthesiologists apply to tailor cerebral oxygen delivery, aiming to safeguard brain function in the perioperative period.

Disease-Targeted Treatment Improves Cognitive Function in Patients with Precapillary Pulmonary Hypertension

BACKGROUND

Patients with pulmonary hypertension (PH) may suffer from cognitive deficits that potentially relate to reduced oxygen delivery and cerebral tissue oxygenation (CTO).

OBJECTIVE

To evaluate the hypothesis that cognitive function improves with therapy, along with improved CTO.

METHODS

Twenty incident patients with arterial or chronic thromboembolic PH had CTO monitoring by near-infrared spectroscopy during diagnostic right heart catheterization. Cognitive tests [Trail Making Tests (TMTs), Victoria Stroop tests and the Five-Point Test (5PT)], the 6-min walk distance (6MWD) test, New York Heart Association (NYHA) class and health-related quality of life (HRQoL) were assessed and repeated after 3 months of disease-targeted medication.

RESULTS

At baseline, 45% of PH patients had cognitive deficits. At 3 months, the patients had improved on the TMT A and the Stroop 2 test [37 s (27; 55) versus 30 s (24; 42), p < 0.05, and 18 s (16; 22) versus 16 s (15; 20), p < 0.01], whereas CTO remained unchanged. Arterial oxygen saturation, NYHA class, 6MWD and HRQoL had also improved. Baseline CTO was the strongest predictor of cognitive function, even in multivariate analysis including age, 6MWD and HRQoL. Improvements in cognitive function were not associated with changes in CTO.

CONCLUSIONS

In patients with PH, 3 months of disease-targeted medication resulted in better cognitive function. Although CTO was the strongest predictor of cognitive function at baseline, it did not change during target therapy. The results of this pilot study should be confirmed in an adequately powered controlled trial.

Sleep, cognition, and normal aging: integrating a half century of multidisciplinary research

Sleep is implicated in cognitive functioning in young adults. With increasing age, there are substantial changes to sleep quantity and quality, including changes to slow-wave sleep, spindle density, and sleep continuity/fragmentation. A provocative question for the field of cognitive aging is whether such changes in sleep physiology affect cognition (e.g., memory consolidation). We review nearly a half century of research across seven diverse correlational and experimental domains that historically have had little crosstalk. Broadly speaking, sleep and cognitive functions are often related in advancing age, though the prevalence of null effects in healthy older adults (including correlations in the unexpected, negative direction) indicates that age may be an effect modifier of these associations. We interpret the literature as suggesting that maintaining good sleep quality, at least in young adulthood and middle age, promotes better cognitive functioning and serves to protect against age-related cognitive declines.

A change in sleep pattern may predict Alzheimer disease

OBJECTIVE

Sleep problems may adversely affect neuronal health. We examined a subjective report of change (reduced duration and/or depth) in sleep pattern in relation to subsequent risk of incident all-cause dementia and Alzheimer disease (AD) over 9 years.

METHODS

This longitudinal study used data from a population-based sample of 214 Swedish adults aged 75 and over who were dementia-free both at baseline and at first follow-up (3 years later). The sample was 80% female and, on average, 83.4 years of age at baseline. All participants underwent a thorough clinical examination to ascertain all-cause dementia and AD.

RESULTS

Forty percent of participants reported a change in sleep duration at baseline. Between the 6th and 9th year after baseline, 28.5% were diagnosed with all-cause dementia, 22.0% of whom had AD. Reduced sleep was associated with a 75% increased all-cause dementia risk (hazard ratio: 1.75; 95% confidence interval: 1.04-2.93; Wald = 4.55, df = 1, p = 0.035) and double the risk of AD (hazard ratio: 2.01; 95% confidence interval: 1.12-3.61; Wald = 5.47, df = 1, p = 0.019) after adjusting for age, gender, and education. The results remained after adjusting for lifestyle and vascular factors but not after adjusting for depressive symptoms. No evidence supported a moderating effect of the use of sleeping pills, and the sleep-dementia relationship remained after controlling for the presence of the apolipoprotein E ε4 allele.

CONCLUSION

Self-reported sleep problems may increase the risk for dementia, and depressive symptoms may explain this relationship. Future research should determine whether treatment, in particular, behavioral or nonpharmacologic treatment, may represent one avenue toward reduction of dementia risk in late life.

Obesity is associated with a lower resting oxygen saturation in the ambulatory elderly: results from the cardiovascular health study

BACKGROUND

The contribution of obesity to hypoxemia has not been reported in a community-based study. Our hypothesis was that increasing obesity would be independently associated with lower SpO2 in an ambulatory elderly population.

METHODS

The Cardiovascular Health Study ascertained resting SpO2 in 2,252 subjects over age 64. We used multiple linear regression to estimate the association of body mass index (BMI) with SpO2 and to adjust for potentially confounding factors. Covariates including age, sex, race, smoking, airway obstruction (based on spirometry), self reported diagnosis of emphysema, asthma, heart failure, and left ventricular function (by echocardiography) were evaluated.

RESULTS

Among 2,252 subjects the mean and median SpO2 were 97.6% and 98.0% respectively; 5% of subjects had SpO2 values below 95%. BMI was negatively correlated with SpO2 (Spearman R = -0.27, P < .001). The mean difference in SpO2 between the lowest and highest BMI categories (< 25 kg/m(2) and ≥ 35 kg/m(2)) was 1.33% (95% CI 0.89-1.78%). In multivariable linear regression analysis, SpO2 was significantly inversely associated with BMI (1.4% per 10 units of BMI, 95% CI 1.2-1.6, for whites/others, and 0.87% per 10 units of BMI, 95% CI 0.47-1.27, for African Americans).

CONCLUSIONS

We found a narrow distribution of SpO2 values in a community-based sample of ambulatory elderly. Obesity was a strong independent contributor to a low SpO2, with effects comparable to or greater than other factors clinically associated with lower SpO2.

Executive dysfunction in OSA before and after treatment: a meta-analysis

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) is a frequent and often underdiagnosed condition that is associated with upper airway collapse, oxygen desaturation, and sleep fragmentation leading to cognitive dysfunction. There is meta-analytic evidence that subdomains of attention and memory are affected by OSA. However, a thorough investigation of the impact of OSA on different subdomains of executive function is yet to be conducted. This report investigates the impact of OSA and its treatment, in adult patients, on 5 theorized subdomains of executive function.

DESIGN

An extensive literature search was conducted of published and unpublished materials, returning 35 studies that matched selection criteria. Meta-analysis was used to synthesize the results from studies examining the impact of OSA on executive functioning compared to controls (21 studies), and before and after treatment (19 studies); 5 studies met inclusion in both categories.

MEASUREMENTS

Research papers were selected which assessed 5 subdomains of executive function: Shifting, Updating, Inhibition, Generativity, and Fluid Reasoning.

RESULTS

All 5 domains of executive function demonstrated medium to very large impairments in OSA independent of age and disease severity. Furthermore, all subdomains of executive function demonstrated small to medium improvements with CPAP treatment.

DISCUSSION

Executive function is impaired across all five domains in OSA; these difficulties improved with CPAP treatment. Age and disease severity did not moderate the effects found; however, further studies are needed to explore the extent of primary and secondary effects, and the impact of age and premorbid intellectual ability (cognitive reserve).

Brazilian green propolis suppresses the hypoxia-induced neuroinflammatory responses by inhibiting NF-κB activation in microglia

Hypoxia has been recently proposed as a neuroinflammatogen, which drives microglia to produce proinflammatory cytokines, including interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and IL-6. Considering the fact that propolis has hepatoprotective, antitumor, antioxidative, and anti-inflammatory effects, propolis may have protective effects against the hypoxia-induced neuroinflammatory responses. In this study, propolis (50 μg/mL) was found to significantly inhibit the hypoxia-induced cytotoxicity and the release of proinflammatory cytokines, including IL-1β, TNF-α, and IL-6, by MG6 microglia following hypoxic exposure (1% O2, 24 h). Furthermore, propolis significantly inhibited the hypoxia-induced generation of reactive oxygen species (ROS) from mitochondria and the activation of nuclear factor-κB (NF-κB) in microglia. Moreover, systemic treatment with propolis (8.33 mg/kg, 2 times/day, i.p.) for 7 days significantly suppressed the microglial expression of IL-1β, TNF-α, IL-6, and 8-oxo-deoxyguanosine, a biomarker for oxidative damaged DNA, in the somatosensory cortex of mice subjected to hypoxia exposure (10% O2, 4 h). These observations indicate that propolis suppresses the hypoxia-induced neuroinflammatory responses through inhibition of the NF-κB activation in microglia. Furthermore, increased generation of ROS from the mitochondria is responsible for the NF-κB activation. Therefore, propolis may be beneficial in preventing hypoxia-induced neuroinflammation.

Piecing together phenotypes of brain injury and dysfunction in obstructive sleep apnea

Obstructive sleep apnea (OSA) is a highly prevalent condition that is associated with significant neurobehavioral impairments. Cognitive abnormalities identified in individuals with OSA include impaired verbal memory, planning, reasoning, vigilance, and mood. Therapy for OSA improves some but not all neurobehavioral outcomes, supporting a direct role for OSA in brain dysfunction and raising the question of irreversible injury from OSA. Recent clinical studies have refined the neurobehavioral, brain imaging, and electrophysiological characteristics of OSA, highlighting findings shared with aging and some unique to OSA. This review summarizes the cognitive, brain metabolic and structural, and peripheral nerve conduction changes observed in OSA that collectively provide a distinct phenotype of OSA brain injury and dysfunction. Findings in animal models of OSA provide insight into molecular mechanisms underlying OSA neuronal injury that can be related back to human neural injury and dysfunction. A comprehensive phenotype of brain function and injury in OSA is essential for advancing diagnosis, prevention, and treatment of this common disorder.

Use of near-infrared spectroscopy as a measure of cerebrovascular health in aging adults

Neuroimaging techniques assessing oxygenation of cerebral blood (such as near-infrared spectroscopy, NIRS) may reflect general cerebrovascular health, a factor not always considered in studies comparing younger and older adults. We examined whether baseline dorsolateral prefrontal cerebral oxygenation (measured by NIRS) was related to cardiovascular risk factors and cognitive test performance in healthy older adults. We found that cardiovascular risk factors are associated with both baseline dorsolateral prefrontal cortex cerebral oxygenation and memory performance. In addition, cardiovascular health factors were associated with memory performance, and the relationship between cerebral oxygenation and memory performance was explained by these cardiovascular health factors, supporting our contention that NIRS can reflect general cerebrovascular health in older adults. Results suggest that studies examining differences in cortical activation in older and younger adults should consider the potential confound of cardiovascular and cerebrovascular health when interpreting data from imaging methods based on oxygenated cerebral blood flow.

Dysfunctional nucleus tractus solitarius: its crucial role in promoting neuropathogenetic cascade of Alzheimer's dementia--a novel hypothesis

The pathophysiological mechanism(s) underlying Alzheimer's disease (AD) still remain unclear, and no disease-modifying or prophylactic therapies are currently available. Unraveling the fundamental neuropathogenesis of AD is an important challenge. Several studies on AD have suggested lesions in a number of CNS areas including the basal forebrain, hippocampus, entorhinal cortex, amygdale/insula, and the locus coeruleus. However, plausible unifying studies on the upstream factors that involve these heterogeneous regions and herald the onset of AD pathogenesis are not available. The current article presents a novel nucleus tractus solitarius (NTS) vector hypothesis that underpins several disparate biological mechanisms and neural circuits, and identifies relevant hallmarks of major presumptive causative factor(s) linked to the NTS, in older/aging individuals. Aging, obesity, infection, sleep apnea, smoking, neuropsychological states, and hypothermia-all activate inflammatory cytokines and oxidative stress. The synergistic impact of systemic proinflammatory mediators activates microglia and promotes neuroinflammation. Acutely, the innate immune response is protective defending against pathogens/toxins; however, when chronic, it causes neuroinflammation and neuronal dysfunction, particularly in brainstem and neocortex. The NTS in the brainstem is an essential multiple signaling hub, and an extremely important central integration site of baroreceptor, chemoreceptor, and a multitude of sensory afferents from gustatory, gastrointestinal, cardiac, pulmonary, and upper airway systems. Owing to persistent neuroinflammation, the dysfunctional NTS exerts deleterious impact on nucleus ambiguus, dorsal motor nucleus of vagus, hypoglossal, parabrachial, locus coeruleus and many key nuclei in the brainstem, and the hippocampus, entorhinal cortex, prefrontal cortex, amygdala, insula, and basal forebrain in the neocortex. The neuronal and synaptic dysfunction emanating from the inflamed NTS may affect its interconnected pathways impacting almost the entire CNS--which is already primed by neuroinflammation, thus promoting cognitive and neuropsychiatric symptoms. The upstream factors discussed here may underpin the neuropathopgenesis of AD. AD pathology is multifactorial; the current perspective underscores the value of attenuating disparate upstream factors--in conjunction with anticholinesterase, anti-inflammatory, immunosuppressive, and anti-oxidant pharmacotherapy. Amelioration of the NTS pathology may be of central importance in countering the neuropathological cascade of AD. The NTS, therefore, may be a potential target of novel therapeutic strategies.

Preoperative regional cerebral oxygen saturation is a predictor of postoperative delirium in on-pump cardiac surgery patients: a prospective observational trial

Introduction

Postoperative delirium is an important problem in patients undergoing major surgery. Cerebral oximetry is a non-invasive method to detect imbalances in the cerebral oxygen supply/demand-ratio. Low preoperative cerebral oxygen saturation (ScO₂) levels have been associated with postoperative delirium in non-cardiac surgery patients. The present prospective observational study determines the relationship between pre- and intra-operative ScO₂ levels and postoperative delirium in patients undergoing on-pump cardiac surgery.

Methods

After approval of the local ethical committee and written informed consent, N = 231 patients scheduled for elective/urgent cardiac surgery were enrolled. Delirium was assessed by the confusion-assessment-method for the intensive care unit (CAM-ICU) on the first three days after surgery. ScO₂ was obtained on the day before surgery, immediately before surgery and throughout the surgical procedure. Preoperative cognitive function, demographic, surgery related, and intra- and post-operative physiological data were registered.

Results

Patients with delirium had lower pre- and intra-operative ScO₂ readings, were older, had lower mini-mental-status-examination(MMSE) scores, higher additive EuroScore and lower preoperative haemoglobin-levels. The binary logistic regression identified older age, lower MMSE, neurological or psychiatric disease and lower preoperative ScO₂ as independent predictors of postoperative delirium.

Conclusions

The presented study shows that a low preoperative ScO₂ is associated with postoperative delirium after on-pump cardiac surgery.