Neural correlates of cognitive dysfunction after cardiac surgery

Profiles of cognitive impairment in chronic heart failure-A cluster analytic approach

Background

Cognitive impairment is a major comorbidity in patients with chronic heart failure (HF) with a wide range of phenotypes. In this study, we aimed to identify and compare different clusters of cognitive deficits.

Methods

The prospective cohort study "Cognition.Matters-HF" recruited 147 chronic HF patients (aged 64.5 ± 10.8 years; 16.2% female) of any etiology. All patients underwent extensive neuropsychological testing. We performed a hierarchical cluster analysis of the cognitive domains, such as intensity of attention, visual/verbal memory, and executive function. Generated clusters were compared exploratively with respect to the results of cardiological, neurological, and neuroradiological examinations without correction for multiple testing.

Results

Dendrogram and the scree plot suggested three distinct cognitive profiles: In the first cluster, 42 patients (28.6%) performed without any deficits in all domains. Exclusively, the intensity of attention deficits was seen in the second cluster, including 55 patients (37.4%). A third cluster with 50 patients (34.0%) was characterized by deficits in all cognitive domains. Age (p = 0.163) and typical clinical markers of chronic HF, such as ejection fraction (p = 0.222), 6-min walking test distance (p = 0.138), NT-proBNP (p = 0.364), and New York Heart Association class (p = 0.868) did not differ between clusters. However, we observed that women (p = 0.012) and patients with previous cardiac valve surgery (p = 0.005) prevailed in the "global deficits" cluster and the "no deficits" group had a lower prevalence of underlying arterial hypertension (p = 0.029). Total brain volume (p = 0.017) was smaller in the global deficit cluster, and serum levels of glial fibrillary acidic protein were increased (p = 0.048).

Conclusion

Apart from cognitively healthy and globally impaired HF patients, we identified a group with deficits only in the intensity of attention. Women and patients with previous cardiac valve surgery are at risk for global cognitive impairment when suffering HF and could benefit from special multimodal treatment addressing the psychosocial condition.

Relationship between post-operative cognitive dysfunction and regional cerebral oxygen saturation and β-amyloid protein

OBJECTIVE

To investigate the relationship between post-operative cognitive dysfunction (POCD) and regional cerebral oxygen saturation (rSO2) and β-amyloid protein (Aβ) in patients undergoing laparoscopic pancreaticoduodenectomy.

METHODS

Fifty patients undergoing elective laparoscopic pancreaticoduodenectomy received five groups of neuropsychological tests 1 d pre-operatively and 7 d post-operatively, with continuous monitoring of rSO2 intra-operatively. Before anesthesia induction (t0), at the beginning of laparoscopy (t1), and at the time of pneumoperitoneum 120 min (t2), pneumoperitoneum 240 min (t3), pneumoperitoneum 480 min (t4), the end of pneumoperitoneum (t5), and 24 h after surgery, jugular venous blood was drawn respectively for the measurement of Aβ by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Twenty-one cases of the fifty patients suffered from POCD after operation. We found that the maximum percentage drop in rSO2 (rSO(2, %max)) was significantly higher in the POCD group than in the non-POCD group. The rSO(2, %max) value of over 10.2% might be a potential predictor of neurocognitive injury for those patients. In the POCD group, the plasma Aβ levels after 24 h were significantly higher than those of pre-operative values (P<0.01). After 24 h, levels of plasma Aβ in the POCD group were significantly higher than those in the non-POCD group (P<0.01).

CONCLUSIONS

The development of POCD in patients undergoing laparoscopic pancreaticoduodenectomy is associated with alterations of rSO2 and Aβ. Monitoring of rSO2 might be useful in the prediction of POCD, and Aβ might be used as a sensitive biochemical marker to predict the occurrence of POCD.

Cognitive dysfunction after on-pump operations: neuropsychological characteristics and optimal core battery of tests

Postoperative cognitive dysfunction (POCD) is a mild form of perioperative ischemic brain injury, which emerges as memory decline, decreased attention, and decreased concentration during several months, or even years, after surgery. Here we present results of our three neuropsychological studies, which overall included 145 patients after on-pump operations. We found that the auditory memory span test (digit span) was more effective as a tool for registration of POCD, in comparison with the word-list learning and story-learning tests. Nonverbal memory or visuoconstruction tests were sensitive to POCD in patients after intraoperative opening of cardiac chambers with increased cerebral air embolism. Psychomotor speed tests (digit symbol, or TMT A) registered POCD, which was characteristic for elderly atherosclerotic patients. Finally, we observed that there were significant effects of the order of position of a test on the performance on this test. For example, the postoperative performance on the core tests (digit span and digit symbol) showed minimal impairment when either of these tests was administered at the beginning of testing. Overall, our data shows that the selection of tests, and the order of which these tests are administered, may considerably influence the results of studies of POCD.

Cognitive dysfunction after cardiac surgery: Pathophysiological mechanisms and preventive strategies

Despite improvements in surgical techniques and the implementation of effective brain protection strategies, the incidence of brain injury after cardiac surgery has remained relatively constant over the years as patients have become older and sicker. Cognitive dysfunction is the most common clinical manifestation of brain injury after cardiac surgery. Its occurrence is related to a combination of three factors that are often associated with cardiopulmonary bypass (CPB): embolism, hypoperfusion, and the inflammatory response. However, such factors and their potential cerebral consequences are not exclusive to CPB. Postoperative cognitive dysfunction also afflicts patients who undergo cardiac surgery without CPB as well as nonsurgery patients who undergo transcatheter interventions. There is growing evidence that patient-related factors such as the presence of (cerebro)vascular risk factors play an important role in both early and late postoperative cognitive dysfunction.

Remote ischemic preconditioning protects neurocognitive function of rats following cerebral hypoperfusion

BACKGROUND

Protection of remote ischemic preconditioning on neurocognitive function caused by bilateral common carotid artery occlusion has been investigated in rats.

MATERIAL/METHODS

Thirty-six male Sprague-Dawley rats were divided into 3 groups - control group (Group C, n=12), bilateral carotid arteries occlusion group (Group B, n=12) and remote ischemic precondition group (Group P, n=12). In Group P, remote ischemic preconditioning (RIPC) was performed on the right femoral artery with 3 cycles (10 min) of occlusion/perfusion. After 3 cycles of preconditioning, bilateral carotid arteries were occluded immediately for 60 min. In Group B, ischemic insults were conducted without RIPC. Sham surgeries were performed in Group C. Evaluation of memory and learning capacity was performed on days 5-8 after surgery by Morris water maze testing of spatial learning capacity (n=6 for each group). Apoptosis of cells in the hippocampus region was determined by TUNEL tests and Bcl-2 at this region was determined by ELISA 24 h and 9 days after vessel occlusion (n=6 for each group).

RESULTS

Neurocognitive tests showed that latency time was significantly longer in Group B than in Group P on day 7 (p=0.016) and day 8 (p=0.036). Moreover, frequency of platform crossings was significant less in group B than in the other 2 groups on day 9. Bcl-2 level was significantly increased in the hippocampal region of rats in Group P on days 1 and 9 after vessel occlusion. TUNEL test showed that apoptosis could be observed at 24 h after occlusion in Group B, but not in Group P and Group C. No apoptosis was observed on day 9.

CONCLUSIONS

Our results suggest that RIPC can protect neurocognitive function of rats after bilateral carotid occlusions, and that Bcl-2 may play an important role in this protective effect.

Electroencephalography as a tool for assessment of brain ischemic alterations after open heart operations

Cardiac surgery is commonly associated with brain ischemia. Few studies addressed brain electric activity changes after on-pump operations. Eyes closed EEG was performed in 22 patients (mean age: 45.2 ± 11.2) before and two weeks after valve replacement. Spouses of patients were invited to participate as controls. Generalized increase of beta power most prominent in beta-1 band was an unambiguous pathological sign of postoperative cortex dysfunction, probably, manifesting due to gamma-activity slowing (“beta buzz” symptom). Generalized postoperative increase of delta-1 mean frequency along with increase of slow-wave activity in right posterior region may be hypothesized to be a consequence of intraoperative ischemia as well. At the same time, significant changes of alpha activity were observed in both patient and control groups, and, therefore, may be considered as physiological. Unexpectedly, controls showed prominent increase of electric activity in left temporal region whereas patients were deficient in left hemisphere activity in comparison with controls at postoperative followup. Further research is needed in order to determine the true neurological meaning of the EEG findings after on-pump operations.

Executive Function Deficits in Acute Stroke

OBJECTIVES

To establish the frequency of executive dysfunction during acute hospitalization for stroke and to examine the relationship of that dysfunction to stroke severity and premorbid characteristics.

DESIGN

Inception cohort study.

SETTING

Inpatient wards at a Veterans Affairs hospital.

PARTICIPANTS

Consecutive sample of inpatients with radiologically or neurologically confirmed stroke. Final sample included 47 patients screened for aphasia and capable of neuropsychologic testing. Two nonstroke inpatient control samples (n=10 each) with either transient ischemic attack (TIA) or multiple stroke risk factors were administered the same research procedure and tests.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Composite cognitive impairment ratio (CIR), calculated from 8 scores indicative of executive function on 6 neuropsychologic tests by dividing number of tests completed into the number of scores falling below cutoff point, defined as 1.5 standard deviations below normative population mean.

RESULTS

Stroke patients had a mean CIR of .61, compared with .48 for TIAs and .44 for stroke-risk-only. Analysis of variance revealed that CIRs of stroke-risk-only patients but not TIAs were lower than those of the stroke patients (P=.02). Impairment frequencies were at least 50% for stroke patients on most test scores. The Symbol Digit Modalities Test (75% impairment) and a design fluency measure distinguished stroke from nonstroke patients. CIR was not related to stroke severity in the stroke patient sample, but was related to estimated premorbid intelligence.

CONCLUSIONS

Executive function deficits are common in stroke patients. The data suggest that limitations in information processing due to these deficits may require environmental and procedural accommodations to increase rehabilitation benefit.

Asymmetric Cerebral Embolic Load and Postoperative Cognitive Dysfunction in Cardiac Surgery

BACKGROUND

The aim of the study was to determine the effects of asymmetric cerebral embolic load on cognitive functions.

METHODS

Thirty-six open heart surgery (OH) and 26 coronary artery bypass grafting (CABG) patients were evaluated by neuropsychological and transcranial Doppler tests.

RESULTS

OH was associated with a significantly larger microembolic load in comparison to CABG. In OH patients, the microembolic load at the left middle cerebral artery correlated with a verbal memory decline, whereas the microembolic load at the right middle cerebral artery correlated with a nonverbal memory deficit. CABG patients also showed a postoperative verbal memory decline which correlated with cardiopulmonary bypass length but not with microembolic load.

CONCLUSION

Massive microembolic load during OH induces specific cognitive impairment in accordance to the brain region to which they are delivered. In atherosclerotic patients, the left temporal region is especially prone to perioperative ischemia.