Association between cerebrovascular carbon dioxide reactivity and postoperative short-term and long-term cognitive dysfunction in patients with diabetes mellitus

Risk Factors for Delirium and Cognitive Decline Following Coronary Artery Bypass Grafting Surgery: A Systematic Review and Meta-Analysis

Background

Coronary artery bypass grafting (CABG) is known to improve heart function and quality of life, while rates of surgery‐related mortality are low. However, delirium and cognitive decline are common complications. We sought to identify preoperative, intraoperative, and postoperative risk or protective factors associated with delirium and cognitive decline (across time) in patients undergoing CABG.

Methods and Results

We conducted a systematic search of Medline, PsycINFO, EMBASE, and Cochrane (March 26, 2019) for peer‐reviewed, English publications reporting post‐CABG delirium or cognitive decline data, for at least one risk factor. Random‐effects meta‐analyses estimated pooled odds ratio for categorical data and mean difference or standardized mean difference for continuous data. Ninety‐seven studies, comprising data from 60 479 patients who underwent CABG, were included. Moderate to large and statistically significant risk factors for delirium were as follows: (1) preoperative cognitive impairment, depression, stroke history, and higher European System for Cardiac Operative Risk Evaluation (EuroSCORE) score, (2) intraoperative increase in intubation time, and (3) postoperative presence of arrythmia and increased days in the intensive care unit; higher preoperative cognitive performance was protective for delirium. Moderate to large and statistically significant risk factors for acute cognitive decline were as follows: (1) preoperative depression and older age, (2) intraoperative increase in intubation time, and (3) postoperative presence of delirium and increased days in the intensive care unit. Presence of depression preoperatively was a moderate risk factor for midterm (1–6 months) post‐CABG cognitive decline.

Conclusions

This meta‐analysis identified several key risk factors for delirium and cognitive decline following CABG, most of which are nonmodifiable. Future research should target preoperative risk factors, such as depression or cognitive impairment, which are potentially modifiable.

Registration

URL: https://www.crd.york.ac.uk/prosp​ero/; Unique identifier: CRD42020149276.

Anesthesiology and cognitive impairment: a narrative review of current clinical literature

Background

The impact of general anesthesia on cognitive impairment is controversial and complex. A large body of evidence supports the association between exposure to surgery under general anesthesia and development of delayed neurocognitive recovery in a subset of patients. Existing literature continues to debate whether these short-term effects on cognition can be attributed to anesthetic agents themselves, or whether other variables are causative of the observed changes in cognition. Furthermore, there is conflicting data on the relationship between anesthesia exposure and the development of long-term neurocognitive disorders, or development of incident dementia in the patient population with normal preoperative cognitive function. Patients with pre-existing cognitive impairment present a unique set of anesthetic considerations, including potential medication interactions, challenges with cooperation during assessment and non-general anesthesia techniques, and the possibility that pre-existing cognitive impairment may impart a susceptibility to further cognitive dysfunction.

Main body

This review highlights landmark and recent studies in the field, and explores potential mechanisms involved in perioperative cognitive disorders (also known as postoperative cognitive dysfunction, POCD). Specifically, we will review clinical and preclinical evidence which implicates alterations to tau protein, inflammation, calcium dysregulation, and mitochondrial dysfunction. As our population ages and the prevalence of Alzheimer’s disease and other forms of dementia continues to increase, we require a greater understanding of potential modifiable factors that impact perioperative cognitive impairment.

Conclusions

Future research should aim to further characterize the associated risk factors and determine whether certain anesthetic approaches or other interventions may lower the potential risk which may be conferred by anesthesia and/or surgery in susceptible individuals.

Postoperative Cognitive Dysfunction after Coronary Artery Bypass Grafting

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

Associations of dyslipidaemia and lipid-lowering treatment with risk of postoperative cognitive dysfunction: a systematic review and meta-analysis

BACKGROUND

Lipid imbalance is linked to age-related cognitive impairment, but its role in postoperative cognitive dysfunction (POCD) is unknown. Here, we present a systematic review and meta-analysis on dyslipidaemia, lipid-lowering treatment and POCD risk.

METHODS

PubMed, Ovid SP and Cochrane databases were searched for longitudinal studies that reported on associations of any measure of dyslipidaemia and/or lipid-lowering treatment with POCD as relative risks (RRs) or ORs. Fixed-effects inverse variance models were used to combine effects.

RESULTS

Of 205 articles identified in the search, 17 studies on 2725 patients (grand mean age 67 years; mean age range 61-71 years) with follow-up periods of 1 day to 4 years (median 7 days; IQR 1-68 days) were included. Studies focused almost exclusively on hypercholesterolaemia as a measure of dyslipidaemia and on statins as lipid-lowering treatment. Across 12 studies on hypercholesterolaemia, we found no association with POCD risk (RR 0.93; 95% CI 0.80 to 1.08; P=0.34). Statin use before surgery was associated with a reduced POCD risk across eight studies (RR 0.81; 95% CI 0.67 to 0.98; P=0.03), but data on treatment duration were lacking.

CONCLUSION

Statin users appear to be at reduced risk of POCD although hypercholesterolaemia per se may not be associated with POCD risk. Trial studies are needed to evaluate the usefulness of statins in POCD prevention.

Cerebrovascular CO2 reactivity during isoflurane-nitrous oxide anesthesia in patients with chronic renal failure

PURPOSE

We assessed the cerebrovascular CO₂ reactivity (CO₂R) in chronic renal failure (CRF) patients without diabetes mellitus (DM), uncontrolled hypertension, peripheral vascular disease, or neurological disease under isoflurane-nitrous oxide anesthesia.

METHODS

Forty-nine patients undergoing surgery, including 36 CRF patients (30 receiving dialysis and six pre-dialysis patients) and 13 patients without CRF (controls). Middle cerebral artery flow velocity (VMCA) was measured by transcranial Doppler ultrasonography at an end-tidal CO₂ of 35 to 45 mmHg. CO₂R was calculated as an absolute value (change in VMCA per mmHg PaCO₂) and a relative value (absolute CO₂R/baseline VMCA × 100). Factors associated with CO₂R were evaluated simultaneously.

RESULTS

Despite no significant differences in the absolute and relative values of CO₂R between the CRF (mean 2.5 cm/s/mmHg; median 5.0%/mmHg) and control (2.4 cm/s/mmHg; 5.0%/mmHg) groups, blood urea nitrogen (BUN) concentrations in the CRF group correlated inversely with both absolute and relative CO₂R. BUN concentration was higher (mean 72 versus 53 mg/dl, p = 0.006) and relative CO₂R was lower (mean 2.6 versus 5.7%/mmHg, p = 0.011) in patients with pre-dialysis CRF (n = 6) versus CRF patients receiving dialysis (n = 30).

CONCLUSIONS

CO₂R in CRF patients was not significantly different from that in controls. However, in CRF patients with high BUN concentrations, CO₂R might be impaired, leading to reduced cerebrovascular reserve capacity. Because DM is a major cause of CRF and we excluded DM patients, our results might not be applicable to patients with DM-induced CRF.

Diabetes is associated with risk of postoperative cognitive dysfunction: A meta-analysis

BACKGROUND

Postoperative cognitive dysfunction (POCD) occurs frequently after surgery, particularly among older people. Diabetes, chronic hyperglycemia, and a history of hypoglycemia are related to cognitive impairment, but little is known about their roles in POCD. Here, we estimated their associations with risk of POCD on the basis of published epidemiological research.

METHODS

The PubMed and Cochrane databases were searched for longitudinal studies of adults undergoing surgery with reporting of associations of diabetes status, glycemic levels, and/or a history of hypoglycemia with risk of POCD as relative risks or odds ratios. Meta-analysis Of Observational Studies in Epidemiology (MOOSE) and Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines were followed.

RESULTS

The search identified 246 publications of which 14 met inclusion criteria, reporting on a total of 2642 patients (mean age 64 y). Follow-up periods spanned 1 day to 5 years. Overall, patients with diabetes had a 1.26-fold higher risk of POCD compared with diabetes-free patients (95% CI, 1.12-1.42). A single study assessed glycemic control in patients with diabetes and identified a higher hemoglobin A1c (HbA1c) level as associated with higher POCD risk (relative risk per percent higher HbA1c, 2.0; 95% CI, 1.4-2.6). We did not find studies on glycemic levels in the nondiabetic range or on hypoglycemia as potential predictors of POCD.

CONCLUSION

Patients with diabetes appear to have a higher risk of POCD compared with diabetes-free persons. Among patients with diabetes, POCD risk may further increase with poorer glycemic control as indexed by higher HbA1c. The roles of HbA1c levels among nondiabetic persons in POCD risk warrant further research.

Hypertension and Risk of Post-Operative Cognitive Dysfunction (POCD): A Systematic Review and Meta-Analysis

Background:

Post-operative cognitive dysfunction (POCD) occurs frequently after major surgery. Hypertension is well-established as a risk factor for age-related cognitive impairment, but it is unclear whether or not it also increases the risk of POCD.

Objective:

To evaluate the role of hypertension in POCD risk in a systematic review and meta-analysis.

Method:

PubMed, Ovid SP and the Cochrane Database of Systematic Reviews were searched for longitudinal studies of adults undergoing surgery with reporting of hypertension, blood pressure and/or anti-hypertensive treatment associations with POCD as relative risks or odds ratios. Fixed-effects meta-analyses were performed using Review Manager (version 5.3).

Results:

Twenty-four studies on 4317 patients (mean age 63 years) were included. None of the studies had set out to assess hypertension as a risk factor for POCD. Hypertension was used as a categorical predictor throughout and only 2 studies adjusted for potential confounders. Across all 24 studies, hypertension was not significantly associated with POCD risk (RR 1.01; 95% CI 0.93, 1.09; p=0.82), though among 8 studies with >75% males, we found hypertension associations with a 27% increased risk of POCD (RR 1.27, 95% CI 1.07, 1.49; p=0.005).

Conclusion:

Our findings do not support the hypothesis that hypertension is a risk factor for POCD. However, since none of the studies included in our analysis were hypothesis-driven and most did not adjust for potential confounders, further systematic investigations are needed to evaluate the role of hypertension in the epidemiology of POCD.

Forbidden word entropy of cerebral oximetric values predicts postoperative neurocognitive decline in patients undergoing aortic arch surgery under deep hypothermic circulatory arrest

Purpose:

Up to 53% of cardiac surgery patients experience postoperative neurocognitive decline. Cerebral oximetry is designed to detect changes in cerebral tissue saturation and therefore may be useful to predict which patients are at risk of developing neurocognitive decline.

Methods:

This is a retrospective analysis of a prospective study originally designed to determine if treatment of cerebral oximetry desaturation is associated with improvement in postoperative cognitive dysfunction in patients undergoing aortic reconstruction under deep hypothermic circulatory arrest. Cognitive function was measured, preoperatively and 3 months postoperatively, with 15 neuropsychologic tests administered by a psychologist; the individual test scores were summed and normalized. Bilateral cerebral oximetry data were stored and analyzed using measures of entropy. Cognitive decline was defined as any decrease in the summed normalized score from baseline to 3 months.

Results:

Seven of 17 (41%) patients suffered cognitive decline. There was no association between baseline cerebral oximetry and postoperative cognitive dysfunction. Nor were changes in oximetry values associated with cognitive decline. However, cognitive decline was associated with loss of forbidden word entropy (FwEn) (correlation: Rho ρ = 0.51, P = 0.037 for left cerebral oximetry FwEn and ρ = 0.54, P = 0.025 for right cerebral oximetry FwEn).

Conclusion:

Postoperative cognitive decline was associated with loss of complexity of the time series as shown by a decrease in FwEn from beginning to end of the case. This suggests that regulation of cerebral oximetry is different between those who do and those who do not develop cognitive decline.

[Association of cognitive impairments with carbohydrate and lipid metabolic parameters in type 2 diabetes mellitus patients undergoing coronary bypass surgery]

AIM. To comparatively analyze neuropsychological parameters in patients with coronary artery disease (CAD) depending on the presence of type 2 diabetes mellitus (DM) and to evaluate their relationship to carbohydrate and lipid metabolic parameters.

SUBJECTS AND METHODS

Fifty-two male patients with type 2 DM (mean age 58.0 ± 5.7 years) and 46 male patients without this condition (mean age 57.1 ± 6.2 years) were examined. Besides standard clinical examination, neurophysiological testing and determinations of glycated hemoglobin (HbA(1c),) and insulin concentrations, QUICKI index, and blood lipid profile were made.

RESULTS

The patients with DM differed from those without DM in the lower speeds of sensorimotor reactions during neurodynamic testing and in worse attention values. In the patients with type 2 DM, the worse neuropsychological status was associated with the higher plasma concentrations of glucose, insulin, HbA(1c), total cholesterol, low-density lipoproteins, and triglycerides and with the lower levels of high-density lipoproteins. These relationships were not observed in the patients without DM.

CONCLUSION

The patients with CAD concurrent with DM had a worse neurophysiological status than those without DM. Only the DM group demonstrated a relationship between cognitive impairments and carbohydrate metabolic markers. Carbohydrate and lipid metabolic disturbances may be assumed to make a negative contribution to the development of cognitive impairments in patients with CAD concurrent with type 2 DM.