Perceptual and cognitive deficit following coronary artery bypass surgery

Interpreting studies of cognitive function following cardiac surgery: a guide for surgical teams

Patients with coronary disease and related health care providers are faced with confusing and often conflicting information with regards to the neurocognitive impact of different strategies for coronary revascularization. Studies involving the measurement of postoperative cognitive deficit (POCD) have significant limitations that may ultimately impact on their interpretation and clinical relevance. In this review, we have described the origin of these tests and delineated the rationale for the design of testing that is commonly used in cardiac surgery patients. In general, neurocognitive tests assess domains of memory/new learning, psychomotor speed/dexterity and attentional capacity/mental control. Pre- and post-intervention tests in each domain can be evaluated either by the measurement of mean change scores (Group Comparison Model) for the entire group as continuous data, or by using categorical or continuous data to examine patterns of individual decline (Individual Comparison Model). This latter approach requires a specific definition of what constitutes a decline, which can be criticized as being arbitrary. There are limitations to each of these approaches that necessitate that critical information in trial design is available to the reviewer to facilitate interpretation. For example, the impact of factors such as test/re-test reliability and practice effect can be mitigated by the use of an appropriately chosen control population. Liberal parlance of neurocognitive outcome as a rationale for therapeutic choice must be tempered by wise interpretation of these tests. It is only through the understanding of their limitations and the implications of trial design that we can translate these results to provide the best therapeutic options for our patients in unbiased manner.

Perceived Cognitive Function and Emotional Distress Following Coronary Artery Bypass Surgery

Many patients experience decrements in cognitive function and emotional adjustment following coronary artery bypass graft (CABG) surgery. Moreover, cognitive decline and emotional distress are often positively related. This study evaluated the cross-sectional and prospective associations of emotional and subjective cognitive complaints, to assess the hypothesis that they would be mutually reinforcing. Participants were 76 CABG patients recruited from Akron General Medical Center. Depression and anxiety symptoms and perceived cognitive difficulties were evaluated at a baseline postsurgical visit and re-assessed 5 months later. Emotional symptoms and perceived cognitive difficulties were significantly related both within and across time. After controlling for numerous potential confounds, baseline perceived cognitive difficulties predicted a more negative course of emotional symptoms during follow-up. Baseline emotional symptoms did not predict the course of perceived cognitive difficulties. Perceptions of cognitive decline may contribute to emotional distress in patients post-CABG.

Surgery of the thoracic aorta using deep hypothermic total circulatory arrest. Are there neurological consequences other than frank cerebral defects?

OBJECTIVE

Deep hypothermic total circulatory arrest has reduced primary morbidity and mortality in thoracic aortic surgery. Although frank neurological deficits have been proven to be a rare complication of this technique, the rate of subtle but irreversible neuropsychological disorders remains unknown.

METHODS

A total of 23 patients (15 male, 8 female) who had undergone surgery for dissection or aneurysm of the thoracic aorta using deep hypothermic total circulatory arrest (mean 25.5 min, range 10-75 min) were studied retrospectively. The mean follow-up was 17 months. The following psychometric tests were conducted: a computer-based test battery to assess tonic alertness and sustained attention, the trail making test (TMT part A and B), the Münchner Gedächtnistest and a verbal learning test. In addition, a cerebral dopamine D2 receptor scintigraphy (using the SPECT technique) was performed. For comparison, 10 healthy subjects were studied.

RESULTS

With regard to tonic alertness, 69.6 and 30.4% were below the 50th and 10th centiles, respectively, according to age- and education-corrected standard values. The impairment in sustained attention correlated significantly with the duration of the circulatory arrest. On the tests assessing short-term memory, the patients scored 30% below their age- and education-corrected peers. In terms of long-term memory, 60.9 and 39.1% of the patients were below one and two standard deviations, respectively. Concerning speed of information processing whilst 78.3% of the patients were below the 50th and 21.7% below the 10th centile. Indicative of some persistent and functional brain alteration, the dopamine D2 receptor binding was significantly reduced when compared with healthy subjects.

CONCLUSIONS

These data prove a substantial and chronic reduction of higher cognitive function in some of the patients who underwent cardiac surgery using deep hypothermic total circulatory arrest; this was accompanied by a depression of the cerebral dopamine D2 receptor binding.

Analysis and interpretation of neuropsychologic tests in cardiac surgery

Neuropsychologic assessment in the context of cardiac surgery is constrained by the clinical time available to see patients, and as such test selection needs to be carefully planned. Besides the time limitations, it differs from clinical neuropsychologic assessment primarily because it tends to involve at least two assessments, a comparison with performance before operation, and a limited number of tests. The analysis and design issues involved in both incidence studies and intervention studies are discussed in this article. Incidence studies customarily involve a single group assessed on at least two occasions and are designed to identify the numbers of individuals who show clear evidence of neuropsychologic changes after a cardiac operation. Intervention studies involve at least two groups where one factor (eg, surgical equipment) is varied systematically. The research on neuropsychologic deficits after cardiac operations has progressed from incidence studies, which involve a conventional definition of deficit, to intervention studies, in which specific test performance can be compared.