Preoperative 6-Minute Walk Distance Is Associated With Postoperative Cognitive Dysfunction

Outcomes associated with postoperative cognitive dysfunction: a systematic review and meta-analysis

BACKGROUND

Postoperative cognitive dysfunction (POCD) manifests as a subtle decline in cognition, potentially leading to unfavourable postoperative outcomes. We explored the impact of POCD on physical function, length of hospital stay (LOS), dementia and mortality outcomes.

METHODS

PubMed and Scopus were searched until May 2023. All studies of major surgical patients that assessed POCD and outcomes of interest were included. POCD effects were stratified by surgery type (cardiac and noncardiac) and time of POCD assessment (<30 and ≥30 days postsurgery).

RESULTS

Of 2316 studies, 20 met the inclusion criteria. POCD was not associated with functional decline postsurgery. Patients who experienced POCD postcardiac surgery had an increased relative risk (RR) of death of 2.04 [(95% CI: 1.18, 3.50); I2 = 0.00%]. Sensitivity analyses showed associations with intermediate-term mortality among noncardiac surgical patients, with an RR of 1.84 [(95% CI: 1.26, 2.71); I2 = 0.00%]. Patients who developed POCD <30 days postcardiac and noncardiac surgeries experienced longer LOS than those who did not [mean difference (MD) = 1.37 days (95% CI: 0.35, 2.39); I2 = 92.38% and MD = 1.94 days (95% CI: 0.48, 3.40); I2 = 83.29%, respectively]. Postoperative delirium (POD) may contribute to the heterogeneity observed, but limited data were reported within the studies included.

CONCLUSIONS

Patients undergoing cardiac and noncardiac surgeries who developed POCD <30 days postsurgery had poorer outcomes and an increased risk of premature death. Early recognition of perioperative neurocognitive disorders in at-risk patients may enable early intervention. However, POD may confound our findings, with further studies necessary to disentangle the effects of POD from POCD on clinical outcomes.

Perioperative Neurocognitive Disorders in Adults Requiring Cardiac Surgery: Screening, Prevention, and Management

Neurocognitive changes are the most common complication after cardiac surgery, ranging from acute postoperative delirium to prolonged postoperative neurocognitive disorder. Changes in cognition are distressing to patients and families and associated with worse outcomes overall. This review outlines definitions and diagnostic criteria, risk factors for, and mechanisms of Perioperative Neurocognitive Disorders and offers strategies for preoperative screening and perioperative prevention and management of neurocognitive complications.

Which Predictor, SctO2 or SstO2, Is more Sensitive for Postoperative Cognitive Dysfunction in Spine Surgery: A Prospective Observational Study?

OBJECTIVE

Patients undergoing spinal surgery in the prone position may experience venous stasis, often resulting in edema in dependent areas of the body, including the head, and increased postoperative cognitive dysfunction (POCD). Not only does POCD present challenges for post-operative care and recovery, it can also cause permanent damage to the patient's brain and increase mortality and social costs. We aimed to clarify the incidence of POCD in patients with hypertension after prone spine surgery and to further determine the association between intraoperative somatic tissue oxygen saturation (SstO2)/cerebral tissue oxygen saturation (SctO2) and POCD.

METHODS

Patients with hypertension scheduled for open prone spine surgery from January 2020 to April 2021 were included in this single-center, prospective, observational study. SctO2 and SstO2 were monitored by near-infrared spectroscopy continuously throughout the surgery. The primary outcome was POCD assessed using the Mini-Mental Status Examination (MMSE). The association of SstO2 and SctO2 with POCD was evaluated with unadjusted analyses and multivariable logistic regression.

RESULTS

One hundred and one of 112 identified patients were included, 28 (27.8%) of whom developed POCD. None of the investigated SctO2 indices were predictive of POCD. However, the patients with POCD had greater decreases in intraoperative absolute SstO2 and relative SstO2 than the patients without POCD (P = 0.037, P = 0.036). Moreover, three SstO2 indices were associated with POCD, including a greater absolute SstO2 decrease (P = 0.021), a greater relative SstO2 decrease (P = 0.032), and a drop below 90% of the baseline SstO2 (P = 0.002), independent of ASA III status, preoperative platelets and postoperative sepsis. In addition, there was no correlation between intraoperative SctO2 and intraoperative SstO2 or between their respective absolute declines.

CONCLUSION

Twenty-eight (27.7%) of 101 patients developed POCD in patients with hypertension undergoing prone spine surgery, and intraoperative SstO2 is associated with POCD, whereas SctO2 shows no association with POCD. This study may initially provide a valuable new approach to the prevention of POCD in this population.

The association between global cognitive function and walking capacity in individuals with broad ranges of cognitive and physical function: Are there sex differences?

Introduction

Cognitive function is known to be associated with physical function, where greater walking capacity has been shown to have moderate to strong correlations with global cognitive function and other various domains of cognition in older adults with and without chronic conditions. Biological sex may moderate the relationship between cognitive and physical function, but whether sex differences exist in this association has not been examined in an aging population. The purpose of this study was to examine the associations between global cognitive function (Montreal Cognitive Assessment; MoCA), walking capacity (6-Minute Walk Test distance; 6 MWT) and sex in an aging population with broad ranges of cognitive and physical function.

Methods

Participants were assessed for global cognitive function (MoCA) and walking capacity (6 MWT). Multivariable regression analyses were performed to examine the interaction of sex in the association between MoCA and 6 MWT. First, we presented the unadjusted model (Model 1), then the model adjusted for age, history of stroke, and height (Model 2). To determine if there were sex-based differences in the association between global cognitive function and walking capacity, we included sex and an interaction term between sex*6 MWT distance in Models 3 and 4.

Results

Twenty-three females and 36 males were included in the multivariable regression analyses, respectively. Our sample represented broad ranges of cognitive and physical function levels, where MoCA scores ranged from 13 to 30, and 6 MWT distances from 203 to 750 m. 6 MWT distance was associated with MoCA in models unadjusted (R2 = 0.17; F(1,56) = 11.4; p &lt; 0.01) and adjusted for age, stroke history, and height (R2 = 0.20; F(4,53) = 3.2; p = 0.02). No interaction with sex was found, but a main effect of sex was observed (R2 = 0.26; F(5,21) = 3.72; p = 0.03). When adjusting for age, height and history of stroke, males MoCA scores were 2.9 ± 1.3 less than the mean MoCA scores for females.

Discussion

Our findings confirm the positive relationship between cognitive and physical function in older adults. Notably, we also observed superior performance in global cognition among females that was consistent across a broad spectrum of walking capacity.

Identification of individuals at risk for postoperative cognitive dysfunction (POCD)

Postoperative cognitive dysfunction (POCD) is common, occurring in around 10-54% of individuals within first few weeks after surgery. Although the majority of POCD is less commonly persistent later than 3 months following surgery, the condition increases length of stay (LOS), mortality and long-term cognitive decline, raising the need for a broad screening to identify individuals at risk for POCD during the perioperative period. In this narrative review, we summarize preoperative, intraoperative and postoperative risk factors for POCD reported in last 5 years and discuss neuropsychological tools and potential biomarkers and time points for assessment that might be suitable for clinical use. We aim to provide crucial information for developing a strategy of routine screening for POCD, which may assist with better identification of at-risk individuals for early interventions. Very importantly, the utilization of a standardized strategy may also allow higher consistency and comparability across different studies.

Type 2 Diabetes Mellitus with Tight Glucose Control and Poor Pre-Injury Stair Climbing Capacity May Predict Postoperative Delirium: A Secondary Analysis

(1) Background: Previous evidence demonstrates that tight glycemic control and good physical function could reduce the risk of delirium. This study aimed to investigate whether the occurrence of postoperative delirium (POD) in older hip fracture surgery patients is associated with preoperative glycemic control factors or pre-injury physical performance. (2) Methods: Three-hundred and nine individuals aged over 65 years and scheduled for hip fracture surgery were included at a single center. Glycemic control factors and pre-injury physical performance were assessed preoperatively. The presence of delirium was assessed using the Confusion Assessment Method on postoperative hospitalization days. Univariate and multivariable logistic regression models and a risk prediction model of POD were established. (3) Results: Among the 309 patients, 52 (16.83%) experienced POD during the hospital stay. The numbers of pre-injury physical performance and type 2 diabetes mellitus (T2DM) patients were significantly different in the POD and non-POD groups. The multivariable model showed that development of delirium was significantly explained by preoperative fasting blood glucose (FBG) (OR 0.804, p = 0.004), stair climbing (OR 0.709, p = 0.003), T2DM (odds ratio (OR) 3.654, p = 0.001), and age-adjusted Charlson comorbidity index (ACCI) (OR 1.270, p = 0.038). The area under the receiver operating characteristic curve (AUROC) of the risk prediction model including those covariates was 0.770. (4) Conclusions: More older T2DM patients develop POD after hip fracture surgery than patients without T2DM. A simple assessment of preoperative FBG and pre-injury stair climbing capacity may identify those at high risk for the development of POD. Higher preoperative FBG and good pre-injury stair climbing capacity are protective factors for POD.

Predictors of cognitive dysfunction after cardiac surgery: a systematic review

AIMS

Postoperative cognitive dysfunction (POCD) is often experienced by cardiac surgery patients; however, it is not known if some groups of patients experience this more frequently or severely than others.The aim of this systematic review was to identify preoperative and postoperative predictors of cognitive dysfunction in adults following cardiac surgery.

METHODS AND RESULTS

Eight bibliographic databases were searched (January 2005 to March 2021) in relation to cardiac surgery and cognition. Studies including adult patients who had undergone open cardiac surgery and using a validated measurement of cognitive function were included. Full-text review for inclusion, quality assessment, and data extraction were undertaken independently by two authors.A total of 2870 papers were identified, of which 36 papers met the inclusion criteria and were included in the review. The majority were prospective observational studies [n = 28 (75.7%)]. In total, 61 independent predictors (45 preoperative and 16 postoperative) were identified as significant in at least one study; advancing age and education level appear important. Age has emerged as the most common predictor of cognitive outcome.

CONCLUSION

Although a number of predictors of POCD have been identified, they have inconsistently been reported as significantly affecting cognitive outcome. Consistent with previous research, our findings indicate that older patients and those with lower educational levels should be prioritized when developing and trialling interventions to improve cognitive function. These findings are less than surprising if we consider the methodological shortcomings of included studies. It is evident that further high-quality research exploring predictors of POCD is required.

Appropriate exercise level attenuates gut dysbiosis and valeric acid increase to improve neuroplasticity and cognitive function after surgery in mice

Postoperative cognitive dysfunction (POCD) affects the outcome of millions of patients each year. Aging is a risk factor for POCD. Here, we showed that surgery induced learning and memory dysfunction in adult mice. Transplantation of feces from surgery mice but not from control mice led to learning and memory impairment in non-surgery mice. Low intensity exercise improved learning and memory in surgery mice. Exercise attenuated surgery-induced neuroinflammation and decrease of gut microbiota diversity. These exercise effects were present in non-exercise mice receiving feces from exercise mice. Exercise reduced valeric acid, a gut microbiota product, in the blood. Valeric acid worsened neuroinflammation, learning and memory in exercise mice with surgery. The downstream effects of exercise included attenuating growth factor decrease, maintaining astrocytes in the A2 phenotypical form possibly via decreasing C3 signaling and improving neuroplasticity. Similar to these results from adult mice, exercise attenuated learning and memory impairment in old mice with surgery. Old mice receiving feces from old exercise mice had better learning and memory than those receiving control old mouse feces. Surgery increased blood valeric acid. Valeric acid blocked exercise effects on learning and memory in old surgery mice. Exercise stabilized gut microbiota, reduced neuroinflammation, attenuated growth factor decrease and preserved neuroplasticity in old mice with surgery. These results provide direct evidence that gut microbiota alteration contributes to POCD development. Valeric acid is a mediator for this effect and a potential target for brain health. Low intensity exercise stabilizes gut microbiota in the presence of insult, such as surgery.

Diagnostic Criteria of Postoperative Cognitive Dysfunction: A Focused Systematic Review

Postoperative Cognitive Dysfunction (POCD) is characterized by a deterioration in cognitive performance after surgery and is increasingly addressed in research studies. However, a uniform definition of POCD seems to be lacking, which is a major threat to clinical research in this area. We performed a focused systematic review to determine the current degree of heterogeneity in how POCD is defined across studies and to identify those diagnostic criteria that are used most commonly. The search identified 173 records, of which 30 were included. Neurocognitive testing was most commonly performed shortly before surgery and at 7 days postoperatively. A variety of neurocognitive tests were used to test a range of cognitive domains, including complex attention, language, executive functioning, perceptual-motor function, and learning and memory. The tests that were used most commonly were the Mini-Mental State Examination, the digit span test, the trail making test part A, and the digit symbol substitution test, but consensus on which test result would be considered “positive” for POCD was sparse. The results of this systematic review suggest the lack of a consistent approach towards defining POCD. However, commonalities were identified which may serve as a common denominator for deriving consensus-based diagnostic guidelines for POCD.

A prospective pilot study assessing levels of preoperative physical activity and postoperative neurocognitive disorder among patients undergoing elective coronary artery bypass graft surgery

Physical inactivity and a sedentary lifestyle are associated with a chronic low-level inflammatory state which has been implicated in the pathogenesis of cardiovascular disease. There is growing interest in exercise programs as part of surgical ‘prehabilitation’. We therefore studied preoperative physical activity levels of patients undergoing elective Coronary Artery Bypass Graft (CABG) surgery, and performed an exploratory analysis of the influence of physical activity on postoperative outcome. The Short Questionnaire to Assess Health (SQUASH) was used to assess physical activity among 100 patients, of mean (SD) age 65.4 (7.6) years. Additionally, handgrip strength was measured, and the get-up-and-go test was conducted. Anxiety, depression, and quality of life were assessed, and a computerised cognitive test battery was used to assess cognitive performance preoperatively, and three months after surgery. Preoperatively, 76% of patients met the recommended national guidelines for physical activity. The incidence of pre-existing medical conditions, and other pre-operative patient features were similar in active and inactive patients. Preoperative physical activity was significantly inversely related to the logistic EuroSCORE. The level of physical activity was also significantly inversely related with preoperative C-reactive protein (CRP) and peak postoperative CRP, but physical activity did not appear to be associated with any adverse postoperative outcomes or extended length of hospital stay. The incidence of postoperative neurocognitive disorder (PNCD) at 3 months postoperatively was 26%. Cognitive performance was not related with physical activity levels. In summary, this was the first study to assess activity levels of cardiac surgical patients with the SQUASH questionnaire. The majority of patients were physically active. Although physical activity was associated with lower levels of inflammation in this pilot study, it was not associated with an improved clinical or cognitive postoperative outcome.

[Heart or lung? : Diagnostics and management of unclear exertional dyspnea]

Exertional dyspnea is a nonspecific symptom with a variety of underlying causes. It can be challenging to differentiate a beginning cardiac disease from a pulmonary disease or from deconditioning alone. In the presence of obesity, the overall assessment is even more difficult. Rare diseases, such as pulmonary hypertension with dyspnea on exertion as the cardinal symptom are usually diagnosed late in the course of disease. The starting point of a successful evaluation is a thorough patient history. The combination of symptoms, clinical signs and findings leads to a preferred differential diagnosis. Readily available basic findings, such as physical examination, electrocardiogram (ECG), spirometry and laboratory tests help with the diagnosis. For unexplained causes, extended diagnostics such as echocardiography, blood gas analysis and finally special examinations are available. Cardiopulmonary exercise testing (CPET) and exercise echocardiography as well as right heart catheterization at rest and during exercise in the hands of experienced physicians allow an exact differentiation.