Cerebral dysfunction after cardiac operations in elderly patients

Cognitive outcomes following coronary artery bypass grafting: A systematic review and meta-analysis of 91,829 patients

Background

Cognitive impairments, including delirium, are common after coronary artery bypass grafting (CABG) surgery, as described in over three decades of research. Our aim was to pool estimates across the literature for the first-time, relative to time (from pre- to post-CABG) and diagnosis (cognitive impairment, delirium and dementia).

Methods

A systematic search of four databases was undertaken. 215 studies incorporating data from 91,829 patients were used to estimate the prevalence of cognitive impairments pre- and post-CABG, including delirium and dementia post-CABG, using random effects meta-analyses.

Results

Pre-surgical cognitive impairment was seen in 19% of patients. Post-operatively, cognitive impairment was seen in around 43% of patients acutely; this resolved to 19% at 4–6 months and then increased to 25% of patients between 6-months to 1-year post-operatively. In the long term, between 1 and 5-years post-operatively, cognitive impairment increased and was seen in nearly 40% of patients. Post-operative delirium was apparent in 18% of CABG patients which increased to 24% when a diagnostic instrument was utilized alongside clinical criteria. Dementia was present in 7% of patients 5–7 years post-surgery.

Conclusion

The results of this meta-analysis demonstrate that cognitive impairment and delirium are major issues in CABG patients which require specific attention. It is imperative that appropriate methods for investigating cognitive impairment, and screening for delirium using a diagnostic instrument, occur in both pre-and post-CABG settings.

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This meta-analysis pooled results of 91,829 patients, including 215 studies.

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Cognitive impairment and delirium are seen in up to 40% of CABG patients.

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Appropriate methods investigating cognitive impairment are crucial post-CABG.

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Appropriate methods of screening for delirium are crucial post-CABG.

Dexmedetomidine during coronary artery bypass grafting surgery: is it neuroprotective?--A preliminary study

BACKGROUND

In the present study, we aimed to determine whether during coronary artery bypass grafting (CABG) surgery, dexmedetomidine has protective effects against cerebral ischemic injury.

METHOD

Twenty-four patients, aged 50-70 years, undergoing CABG surgery were randomized into two groups of 12 patients each: those receiving dexmedetomidine (group D) and those not receiving it (group C). As basal blood samples from arterial and jugular bulb catheters were drawn, dexmedetomidine (1 microg/kg bolus and infusion at a rate of 0.7 microg/kg/h) was administered to patients in group D. Arterial and jugular venous blood gas analyses, serum S-100B protein (S-100B), neuron-specific enolase (NSE) and lactate measurements were performed after induction, 10 min after the initiation of cardiopulmonary bypass (CPB), 1 min after declamping, at the end of CPB, at the end of the operation and 24 h after surgery. Mann-Whitney U- and Wilcoxon's tests were used for statistical analyses.

RESULTS

No significant between-group differences were found regarding arterial and jugular venous pH, PO(2), PCO(2) and O(2) saturations. S-100B, NSE and lactate levels were also similar between groups D and C. During the post-operative period, there were no clinically overt neurological complications in any patient.

CONCLUSION

Cerebral ischemia marker (S-100B, NSE, lactate) patterns were as expected during CPB; however, there were no differences between the groups, which led us to believe that during CABG surgery dexmedetomidine has no neuroprotective effects. Future studies with larger populations are recommended to further establish the effects of this drug.

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.

Relationship between cerebral injury and inflammatory responses in patients undergoing cardiac surgery with cardiopulmonary bypass

This study was performed to evaluate whether cytokines, adhesion molecules, ghrelin and S-100B are useful markers in predicting the cerebral infarction after cardiac surgery with cardioplumomary bypass (CPB). The patients (n=20) were classified into two groups; group A (n=4) showed postoperative organized cerebral damage, while group B (n=16) consisted of patients without occurrence of postoperative strokes. Before CPB, serum levels of S-100B in both groups A and B were low (<0.5 ng/mL), while ghrelin concentrations in group A (all patients had history of strokes) were much higher than those in group B. After CPB, when serum levels of S-100B in group A at 24h were higher than those in group B, ghrelin in group A at same time point showed high levels in comparison to group B. At 12 and 24h after CPB, levels of tumor necrosis factor (TNF)-alpha, interleukin-10 and soluble TNF-receptor I in group A were significantly higher than those in group B. In conclusion, it is considered that ghrelin as well as S-100B can be a useful marker for the prediction of stoke after CPB. Increase of TNF-alpha, interleukin-10 and soluble TNF-receptor I after CPB may be involved in the pathogenesis of stroke after CPB.

Neuropsychologic impairment after coronary bypass surgery: effect of gaseous microemboli during perfusionist interventions

OBJECTIVE

Neuropsychologic impairment is a common complication of coronary bypass surgery. Cerebral microemboli during cardiopulmonary bypass are the principal cause of cognitive deficits after coronary bypass grafting. We have previously demonstrated that the majority of cerebral emboli occur during perfusionist interventions (ie, during the injection of air into the venous side of the cardiopulmonary bypass circuit). The purpose of this study was to determine whether an increase in perfusionist interventions is associated with an increased risk of postoperative cognitive impairment.

METHODS

Patients undergoing elective coronary artery bypass grafting (n = 83) underwent a battery of neuropsychologic tests preoperatively and 3 months postoperatively. Patients were divided into 2 groups according to the median value of perfusionist interventions during cardiopulmonary bypass. Group 1 patients (n = 42) had fewer than 10 perfusionist interventions, and group 2 patients (n = 41) had 10 or more interventions.

RESULTS

The 2 groups of patients were similar for all preoperative, intraoperative, and postoperative variables, with the exception of longer cardiopulmonary bypass times in group 2 patients (P <.001). Group 2 patients had lower mean scores on 9 of 10 neuropsychologic tests, with 3 (Rey Auditory Verbal Learning, Digit Span, and Visual Span) being statistically significant. Group 2 patients had worse cognitive test scores, even when controlling for increased bypass times. Group 2 patients had a nonsignificant trend toward an increased prevalence of neuropsychologic impairment 3 months postoperatively.

CONCLUSIONS

Introduction of air into the cardiopulmonary bypass circuit by perfusionists, resulting in cerebral microembolization, may contribute to postoperative cognitive impairment.

Issues associated with the identification of cognitive change following coronary artery bypass grafting

OBJECTIVE

Coronary artery bypass grafting (CABG) is a surgical procedure used to treat individuals with ischaemic heart disease and to relieve angina. Disruption to the central nervous system (CNS) has frequently been reported by patients who have undergone CABG.

METHOD

The following paper is a review of the literature that has examined the effects of CABG on the CNS.

RESULTS AND CONCLUSIONS

It becomes apparent that issues about the incidence and severity of post-CABG cognitive decline are still unresolved. First, the cause of post-CABG CNS change has not yet been established, although the presence of changes to brain microvasculature as a result of the presence of microemboli appears to be a likely factor. Second, while some studies have reported high rates of poor performance on neuropsychological tests postoperatively, these reports are often subject to confounds such as variability in postoperative testing intervals, the definition of decline and the neuropsychological test batteries used. Finally, improvements in surgical techniques and changes in patient characteristics may have changed the real nature and prevalence of post-CABG cognitive decline. The review finishes with a series of recommendations for the neuropsychological study of CABG.

Serum S100 protein as a marker of cerebral damage during cardiac surgery

The identification of a serum marker to assist in the diagnosis of cerebral injury after cardiac surgery is potentially useful. S100 protein is an early marker of cerebral damage. It is released after cardiac surgery performed under cardiopulmonary bypass (CPB). Its level is correlated with the duration of CPB, deep circulatory arrest and aortic cross-clamping. Increased levels of S100 protein are correlated with the age of the patient and the number of microemboli, especially during aortic cannulation. Perioperative cerebral complications such as stroke, delayed awakening and confusion are associated with increased levels of S100 protein directly after bypass and from 15 to 48 h after it. In addition, increased levels of S100 protein are related to neuropsychological dysfunction after cardiac surgery. S100 protein has early and late release patterns after CPB; the early pattern may be due to sub-clinical brain injury. The late release pattern may be due to perioperative cerebral complications. Patients undergoing intracardiac operations combined with coronary artery bypass surgery are more susceptible to brain injury and have higher levels of S100 after CPB. Furthermore, adults and children undergoing deep circulatory arrest are more susceptible to brain injury, in terms of higher S100 protein release after CPB. Serum S100 protein levels are reduced after using arterial line filtration and covalent-bonded heparin to coat the inner surface of the CPB circuit.

Early release pattern of S100 protein as a marker of brain damage after warm cardiopulmonary bypass

Warm blood cardioplegia may be more beneficial to the heart than cold cardioplegia, but the effects of warm cardiopulmonary bypass and warm blood cardioplegia on the brain are controversial. S100 protein is an early marker of brain damage and has been detected after cold cardiopulmonary bypass. We studied S100 concentrations in 20 patients undergoing coronary artery bypass surgery before and after warm cardiopulmonary bypass (34-37 degrees C) using warm blood cardioplegia (37 degrees C) for all patients. The peak level of S100 protein occurred immediately after warm cardiopulmonary bypass, then decreased progressively until the last measurement at 4.5 h after bypass. The peak level appears to be dependent upon the age of the patient, with the following regression equation: y = -3.2 + 0.08x, where y is S100 protein concentration in microg.l-1 and x is patient age in years. Further studies are needed to investigate the clinical significance of this early release pattern. Patient age should be taken into account when studying S100 protein levels after cardiopulmonary bypass.

Cognitive decline after major noncardiac operations: a preliminary prospective study

BACKGROUND

Cardiac operations frequently are complicated by postoperative cognitive decline. Less common and less studied is postoperative cognitive decline after noncardiac surgery, so we determined its incidence, severity, and possible predictors.

METHODS

Twenty-nine patients who had thoracic and vascular procedures were studied. A neurocognitive test battery was administered preoperatively and 6 to 12 weeks postoperatively. A change score (preoperative minus postoperative) was calculated for each measure in each individual. Cognitive deficit (a measure of incidence) was defined as a 20% decrement in 20% or more of the completed tests. The average scores of all tests and the average decline (a measure of severity) were determined.

RESULTS

The incidence of cognitive deficit was 44.8%. Overall the severity of the decline was an average of 15% decline. In the 44.8% of patients who had cognitive deficit, the severity was 24.7%. Multivariable predictors of cognitive decline were age (for incidence and severity) and years of education (for severity).

CONCLUSIONS

Cognitive decline after noncardiac operations is a frequent complication of surgical procedures. The severity could preclude successful return to a preoperative lifestyle.

Predictors of neurological morbidity after coronary artery bypass surgery

OBJECTIVE

The aim of this study was to analyze the postoperative neurological complications after myocardial revascularization.

METHODS

We analyzed the pre-, peri- and postoperative data of 3834 patients who underwent a primary isolated bypass grafting between January 1987 and December 1995. Postoperative neurological complications (A) were divided into mild complications (B) and major complications (C).

RESULTS

The incidence of A increased, from 1.4% to 3.0%. Unifactor risk analysis identified: age > 75 years, peripheral vascular atherosclerosis, neurological pathology, aorta-pathology and perioperative myocardial infarction as risk factors for A. Perioperative myocardial infarction and neurological pathology for B; age > 75 years, peripheral vascular atherosclerosis, neurological pathology, perioperative myocardial infarction and aorta pathology for C. Multifactor risk regression analysis identified peripheral vascular atherosclerosis, neurological pathology, aorta-pathology, perioperative myocardial infarction and the time cohort 1993-1995 as independent predictors for A; perioperative myocardial infarction and the time cohort 1993-1995 for B; neurological pathology, aorta-pathology and perioperative myocardial infarction for C.

CONCLUSIONS

Peripheral vascular atherosclerosis, neurological pathology, aorta-pathology, the occurrence of a perioperative myocardial infarction and the time cohort 1993-1995 are identified as independent risk factors for neurological complications.

Regional cerebral blood flow during rewarming of cardiopulmonary bypass correlates with posthypothermic regional glucose use

BACKGROUND AND OBJECTIVES

Although global measurements of cerebral blood flow and metabolism during and after profoundly hypothermic cardiopulmonary bypass have been performed both in experimental animals and in human beings, little is known about their regional changes. The purpose of this study was to investigate the changes in regional cerebral blood flow during profoundly hypothermic cardiopulmonary bypass and regional cerebral glucose use after cardiopulmonary bypass.

METHODS

We measured regional cerebral blood flow with positron emission tomography during both the cooling (n=5) and rewarming (n=5) of hypothermic cardiopulmonary bypass in anesthetized dogs by continuously infusing 15O-labeled water. We altered the core temperature between 20 degrees and 37 degrees C. To assess the integrity of brain metabolism, we measured the regional cerebral glucose use by bolus injections of 18F-labeled 2-fluoro-2-deoxy-D-glucose.

RESULTS

Regional cerebral blood flow decreased homogeneously during cooling. The regional cerebral blood flow at 20 degrees C was about one fourth of that at 37 degrees C. In contrast, at 24 degrees, 28 degrees , and 32 degrees C during rewarming, there were significant interregional differences in the regional cerebral blood flow for given temperatures (p=0.0075, 0.034, and 0.048, respectively). These interregional differences disappeared after rewarming. Although the regional cerebral blood flow significantly correlated with the regional cerebral glucose use in the control condition at 37 degrees C without cardiopulmonary bypass (r=0.75; p=0.00012), this correlation disappeared after profoundly hypothermic cardiopulmonary bypass (r=0.204; p=0.388). Regional cerebral blood flow at 32 degrees C during rewarming positively correlated with the regional cerebral glucose use after cardiopulmonary bypass (r=0.655; p=0.0017).

CONCLUSION

The altered regional cerebral blood flow during rewarming of profoundly hypothermic cardiopulmonary bypass might affect regional brain metabolism.

Cerebral emboli and serum S100beta during cardiac operations

BACKGROUND

The glial protein S100beta has been used to estimate cerebral damage in a number of clinical settings. The purpose of this investigation was to determine the correlation between cerebral microemboli and S100beta levels during cardiac operations.

METHODS

Transcranial Doppler ultrasonography was used to measure emboli in the right middle cerebral artery. Emboli counts (n = 111) were divided into five time periods: (1) incision to aortic cannulation; (2) aortic cannulation to cross-clamp onset; (3) cross-clamp onset to cross-clamp release; (4) cross-clamp release to decannulation; and (5) decannulation to chest closure. The level of S100beta (n = 156) was measured at baseline, at the end of cardiopulmonary bypass, then 150 and 270 minutes after cross-clamp release.

RESULTS

The level of S100beta correlated with age, cardiopulmonary bypass time, cross-clamp time, and number of emboli at time period 2. Although cardiopulmonary bypass time was univariately associated with S100beta level, it became nonsignificant in a multivariable model that included age and cross-clamp time.

CONCLUSIONS

The correlation of S100beta level with emboli measured during cannulation (time period 2) supports the hypothesis that cannulation is a high-risk time period for cerebral injury.

Cerebral dysfunction after coronary artery bypass grafting done with mild or moderate hypothermia

OBJECTIVE

Ninety-nine patients undergoing elective coronary artery bypass grafting were enrolled in a prospective, randomized study to evaluate the incidence of cerebral dysfunction after "mild" or "moderate" hypothermia during cardiopulmonary bypass.

METHODS

Patients were evaluated before and after operation before hospital discharge and in some cases at follow-up at least 6 weeks later with a complete neurologic examination (85 patients) and a battery of standard neuropsychometric tests (86 patients).

RESULTS

Postoperative changes detected by neurologic examination consisted of the appearance of new primitive reflexes in both groups. No statistically significant differences in incidence were found. The neuropsychometric performances of the two groups were statistically similar by either event-rate or group-rate analysis.

CONCLUSIONS

There is no detectable difference in postoperative cerebral dysfunction in patients undergoing coronary artery bypass grafting who are supported by cardiopulmonary bypass with either mild or moderate hypothermia.

Comparison of serum S-100 beta levels during CABG and intracardiac operations

BACKGROUND

The risk of overt and subtle cerebral injury may be higher in intracardiac operation (ICO) rather than coronary artery bypass grafting (CABG). S-100 protein is a specific astroglial protein whose serum level increases after cerebral injury. Elevated serum levels of S-100 have been detected after adult cardiac operations and correlated with neurologic injury.

METHODS

The level of S-100 protein was measured serially over 24 hours in 40 patients (27 undergoing aortic valve replacement, 9 mitral valve replacement, 4 closure of atrial septal defect) undergoing ICO and 20 patients undergoing CABG.

RESULTS

The groups were similar with respect to age and cardiopulmonary bypass times. The S-100 level was not elevated before operation in any patient. Peak S-100 levels were reached at skin closure, when 35 of the ICO patients (88%) and 13 of the CABG patients (65%) had elevated S-100 levels. At skin closure peak S-100 levels were significantly greater in the ICO group (median [interquartile range], 0.76 [0.44-1.16] versus 0.3 [0-0.55] microgram/L; p < 0.01). At 5 hours S-100 levels were still elevated in 22 patients in the ICO group compared with 1 patient in the CABG group (p < 0.01), and at 24 hours 17 ICO patients had persistently elevated S-100 levels in comparison with 2 in the CABG group (p < 0.01). One valve patient had a stroke 24 hours after operation accompanied by a secondary increase in the S-100 level. There was no significant difference in postoperative S-100 levels between 5 patients in the ICO group with a prior history of stroke and those without. The peak S-100 level correlated with patient age (r = 0.59; p < 0.001) but not with the duration of cardiopulmonary bypass or core temperature during the operation.

CONCLUSIONS

Intracardiac operation results in a significantly greater elevation in S-100 levels than CABG. Elevated S-100 levels correlate with increasing patient age but not with the duration of cardiopulmonary bypass or intraoperative core temperature. These findings raise the possibility that ICO patients may be more vulnerable to even subtle levels of cerebral injury than CABG patients.

Neurologic assessment and cardiac surgery

Cerebral injury remains a significant complication of cardiac surgery. This complication is evaluated by clinical means that include a neurologic examination. In this report, the most important components of this type of evaluation are described. The neurologic complications of cardiac surgery can be determined by comparing structured preoperative and postoperative clinical evaluations. The neurologic examination must include a mental state examination, examination of cranial nerves, motor, sensory, and cerebellar systems, examination of gait and station, and deep tendon and primitive reflexes. The purpose of this report is to discuss the relevance of the neurologic examination in the assessment of cerebral injury after cardiac surgery, review the components of a structured neurologic examination, and explore the role of "quantitative" stroke scales as a research tool.