Early natural course of transient encephalopathy after coronary artery bypass grafting

Intra-aortic balloon pump does not influence cerebral hemodynamics and neurological outcomes in high-risk cardiac patients undergoing cardiac surgery: an analysis of the IABCS trial

Background

The intra-aortic balloon pump (IABP) is often used in high-risk patients undergoing cardiac surgery to improve coronary perfusion and decrease afterload. The effects of the IABP on cerebral hemodynamics are unknown. We therefore assessed the effect of the IABP on cerebral hemodynamics and on neurological complications in patients undergoing cardiac surgery who were randomized to receive or not receive preoperative IABP in the ‘Intra-aortic Balloon Counterpulsation in Patients Undergoing Cardiac Surgery’ (IABCS) trial.

Methods

This is a prospectively planned analysis of the previously published IABCS trial. Patients undergoing elective coronary artery bypass surgery with ventricular ejection fraction ≤ 40% or EuroSCORE ≥ 6 received preoperative IABP (n = 90) or no IABP (n = 91). Cerebral blood flow velocity (CBFV) of the middle cerebral artery through transcranial Doppler and blood pressure through Finometer or intra-arterial line were recorded preoperatively (T1) and 24 h (T2) and 7 days after surgery (T3) in patients with preoperative IABP (n = 34) and without IABP (n = 33). Cerebral autoregulation was assessed by the autoregulation index that was estimated from the CBFV response to a step change in blood pressure derived by transfer function analysis. Delirium, stroke and cognitive decline 6 months after surgery were recorded.

Results

There were no differences between the IABP and control patients in the autoregulation index (T1: 5.5 ± 1.9 vs. 5.7 ± 1.7; T2: 4.0 ± 1.9 vs. 4.1 ± 1.6; T3: 5.7 ± 2.0 vs. 5.7 ± 1.6, p = 0.97) or CBFV (T1: 57.3 ± 19.4 vs. 59.3 ± 11.8; T2: 74.0 ± 21.6 vs. 74.7 ± 17.5; T3: 71.1 ± 21.3 vs. 68.1 ± 15.1 cm/s; p = 0.952) at all time points. Groups were not different regarding postoperative rates of delirium (26.5% vs. 24.2%, p = 0.83), stroke (3.0% vs. 2.9%, p = 1.00) or cognitive decline through analysis of the Mini-Mental State Examination (16.7% vs. 40.7%; p = 0.07) and Montreal Cognitive Assessment (79.16% vs. 81.5%; p = 1.00).

Conclusions

The preoperative use of the IABP in high-risk patients undergoing cardiac surgery did not affect cerebral hemodynamics and was not associated with a higher incidence of neurological complications.

Trial registrationhttp://www.clinicaltrials.gov (NCT02143544).

Neurocognitive Function after Cardiac Surgery: From Phenotypes to Mechanisms

For half a century, it has been known that some patients experience neurocognitive dysfunction after cardiac surgery; however, defining its incidence, course, and causes remains challenging and controversial. Various terms have been used to describe neurocognitive dysfunction at different times after cardiac surgery, ranging from "postoperative delirium" to "postoperative cognitive dysfunction or decline." Delirium is a clinical diagnosis included in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). Postoperative cognitive dysfunction is not included in the DSM-5 and has been heterogeneously defined, though a recent international nomenclature effort has proposed standardized definitions for it. Here, the authors discuss pathophysiologic mechanisms that may underlie these complications, review the literature on methods to prevent them, and discuss novel approaches to understand their etiology that may lead to novel treatment strategies. Future studies should measure both delirium and postoperative cognitive dysfunction to help clarify the relationship between these important postoperative complications.

[Acute and long-term cognitive consequences of treatment on intensive care units]

BACKGROUND

Following treatment on the intensive care unit (ICU) patients often suffer from acute and long-term cognitive deficits. This is true for patients of all age groups but especially for elderly patients who have undergone surgery and develop postoperative delirium (POD) or postoperative cognitive decline (POCD). Both are associated with severe limitations in the quality of life and long-term outcome.

OBJECTIVE

Which acute and long-term cognitive effects develop in ICU survivors and how do they influence the outcome? How can POD and POCD be differentiated?

METHOD

A selective literature search was carried out.

RESULTS

Following surgery POCD can develop within days to weeks, may persist for weeks or months and can lead to problems in attentiveness even under conditions of inconspicuous consciousness. Remission is possible but may take up to more than 12 months. The POD is a phenomenon characterized by disturbances of consciousness and problems in attention, beginning acutely hours and days postoperatively, can persist for days to weeks and remission can be expected within a few days. While POD often has an organic cause, such as an infection, the pathogenesis of POCD has not been sufficiently elucidated.

DISCUSSION

Both POD and particularly POCD can lead to a deterioration of cognition following ICU treatment. As efficient treatment still has to be developed preventive methods, such as preoperative screening for risk factors, thorough planning of operative and anesthetic techniques and compensation of risk factors as well as providing assistance to patients, e. g. by a trained nurse should be implemented in the clinical routine more often than is presently the case.

Postoperative cognitive dysfunction

BACKGROUND

Older patients in particular are vulnerable to memory disturbances and other types of cognitive impairment after surgical operations. In one study, roughly 12% of patients over age 60 had postoperative cognitive dysfunction (POCD) three months after surgery. This is an important issue in perioperative care as extensive surgery on older patients becomes more common.

METHOD

Selective review of the literature.

RESULTS

POCD is usually transient. It is diagnosed by comparing pre- and postoperative findings on psychometric tests. Its pathogenesis is multifactorial, with the immune response to surgery probably acting as a trigger. Factors that elevate the risk of POCD include old age, pre-existing cerebral, cardiac, and vascular disease, alcohol abuse, low educational level, and intra- and postoperative complications. The findings of multiple randomized controlled trials indicate that the method of anesthesia does not play a causal role for prolonged cognitive impairment. POCD is associated with poorer recovery and increased utilization of social financial assistance. It is also associated with higher mortality (hazard ratio 1.63, 95% confidence interval 1.11-2.38). Persistent POCD enters into the differential diagnosis of dementia.

CONCLUSION

POCD can markedly impair postoperative recovery. The findings of pertinent studies performed to date are difficult to generalize because of heterogeneous patient groups and different measuring techniques and study designs. Further investigation is needed to determine which test instruments are best for clinical use and which preventive strategies might lessen the incidence of POCD.

Diabetes severely affects attentional performance after coronary artery bypass grafting

Background

Diabetes is a risk factor for (micro) vascular damage of the brain, too. Therefore cognitive performance after coronary artery bypass grafting may be hypothesized worse in diabetics. To avoid observational errors a reliable tool for testing attentional performance was used. We evaluated whether diabetes mellitus disposes to distinct cognitive dysfunction after coronary artery bypass grafting (CABG).

Methods

Three aspects in attentional performance were prospectively tested with three different tests (alertness: composed of un-cued and cued reaction, divided attention, and selective attention) by a computerized tool one day before and seven days after CABG in a highly selected cohort of 30 males, 10 of whom had diabetes. Statistical comparisons were done with analysis of variance for repeated measurements and Fisher's LSD.

Results

Prior to CABG there was no statistically meaningful difference between diabetics and non-diabetics. Postoperatively, diabetic patients performed significantly worse than non-diabetics in tests for un-cued (p=0.01) and cued alertness (p=0.03). Test performance in divided attention was worse after CABG but independent of diabetes status. Selective attention was neither affected by diabetes status nor by CABG itself.

Conclusions

Diabetes may have an impact on cognitive performance after CABG. More severe deficits in alertness may point to underlying microvascular disease.

Cognitive trajectories after postoperative delirium

BACKGROUND

Delirium is common after cardiac surgery and may be associated with long-term changes in cognitive function. We examined postoperative delirium and the cognitive trajectory during the first year after cardiac surgery.

METHODS

We enrolled 225 patients 60 years of age or older who were planning to undergo coronary-artery bypass grafting or valve replacement. Patients were assessed preoperatively, daily during hospitalization beginning on postoperative day 2, and at 1, 6, and 12 months after surgery. Cognitive function was assessed with the use of the Mini-Mental State Examination (MMSE; score range, 0 to 30, with lower scores indicating poorer performance). Delirium was diagnosed with the use of the Confusion Assessment Method. We examined performance on the MMSE in the first year after surgery, controlling for demographic characteristics, coexisting conditions, hospital, and surgery type.

RESULTS

The 103 participants (46%) in whom delirium developed postoperatively had lower preoperative mean MMSE scores than those in whom delirium did not develop (25.8 vs. 26.9, P<0.001). In adjusted models, those with delirium had a larger drop in cognitive function (as measured by the MMSE score) 2 days after surgery than did those without delirium (7.7 points vs. 2.1, P<0.001) and had significantly lower postoperative cognitive function than those without delirium, both at 1 month (mean MMSE score, 24.1 vs. 27.4; P<0.001) and at 1 year (25.2 vs. 27.2, P<0.001) after surgery. With adjustment for baseline differences, the between-group difference in mean MMSE scores was significant 30 days after surgery (P<0.001) but not at 6 or 12 months (P=0.056 for both). A higher percentage of patients with delirium than those without delirium had not returned to their preoperative baseline level at 6 months (40% vs. 24%, P=0.01), but the difference was not significant at 12 months (31% vs. 20%, P=0.055).

CONCLUSIONS

Delirium is associated with a significant decline in cognitive ability during the first year after cardiac surgery, with a trajectory characterized by an initial decline and prolonged impairment. (Funded by the Harvard Older Americans Independence Center and others.).

Neuropsychological outcomes after coronary artery bypass grafting

Short- and long-term cognitive declines after cardiac surgery with cardiopulmonary bypass have been reported, but the frequency, severity, nature, and etiology of postoperative cognitive changes have been difficult to quantify. Current studies have corrected the principal methodological shortcoming of earlier studies by including control groups, and have shown that while early postoperative cognitive decline does occur in some patients, it is generally mild and reversible by 3 months after surgery. Late cognitive changes do occur, but comparison with patients undergoing off-pump surgery or those being treated medically suggests that these changes are not specific to CABG or more specifically to the use of cardiopulmonary bypass.

Pathophysiology of delirium in the intensive care unit

Delirium, or acute brain dysfunction, is a life-threatening global disturbance in cognitive functioning that frequently manifests in critically ill patients. This review examines the current status of knowledge regarding the pathophysiology of delirium in the ICU, in particular, evaluating the role of iatrogenic factors such as sedatives and analgesic administration in brain dysfunction. This hypothesis is considered along with several other plausible mechanisms of ICU delirium, including sepsis, postoperative cognitive dysfunction, and changes in biomarkers and neurotransmitters. The review concludes by highlighting potential future directions in molecular genetics for the elucidation of delirium and its long-term consequences.

Postcardiac Surgical Cognitive Impairment in the Aged Using Diffusion-Weighted Magnetic Resonance Imaging

BACKGROUND

Cardiac surgery is associated with cerebral dysfunction. While 1% to 2% of patients experience stroke, cognitive deficits are seen in more than half of patients. Given the high incidence of cognitive decline, it has become the endpoint of many cardiac surgery investigations. Because the elderly are at highest risk, this investigation sought to determine if there is a relationship between new ischemic changes demonstrated by diffusion-weighted magnetic resonance imaging (DW-MRI) and postoperative cognitive deficit in older patients.

METHODS

Fifty cardiac surgical patients (>65 years of age) underwent preoperative and postoperative neurocognitive examinations, including four to six week, postdischarge, follow-up. This evaluation assessed higher cortical function, memory, attention, concentration, and psychomotor performance. Objective evidence of acute cerebral ischemic events was identified using DW-MRI. Scans were analyzed by a neuroradiologist blinded to clinical status and cognitive outcomes.

RESULTS

Among patients with a mean age of 73 years, 88% demonstrated cognitive decline in the postoperative testing period while 32% showed evidence of acute perioperative cerebral ischemia by DW-MRI. At postdischarge follow-up, 30% of patients showed cognitive impairment. However, cognitive decline assessed postoperatively, or at a four to six week follow-up, was unrelated to the presence or absence of DW-MRI detected cerebral ischemia.

CONCLUSIONS

Postoperative neurocognitive impairment, assessed by standard means, is unrelated to acute cerebral ischemia detected by DW-MRI. This strongly suggests that cognitive decline after cardiac surgery is a function of underlying patient factors rather than perioperative ischemic events. This observation has broad implications for future investigation of strategies to prevent cardiac surgery-related neurologic injury.

Practice Effects Associated with the Repeated Assessment of Cognitive Function Using the CogState Battery at 10-minute, One Week and One Month Test-retest Intervals

There are many situations in which cognitive tests need to be administered on more than two occasions and at very brief test-retest intervals to detect change in group performance. However, previous literature has not specifically addressed these important issues. The main aim of the current study was to examine these two factors by using a computerized cognitive battery designed specifically for the repeated assessment of cognition (i.e., CogState) in healthy young adult individuals. A further aim of the study was to examine how many times the battery needed to be completed before performance, as measured by the battery, stabilized. Forty-five adults (age range: 18-40 years) completed the battery four times at 10-minute test-retest intervals, and a fifth time at an interval of one week. The results illustrated that when brief test-retest intervals were used (i.e., 10 minutes), performance stabilized after the second assessment, as significant practice effects were generally observed between the first and the second assessments. Practice effects were also observed on some of the tasks at a one-week test-retest interval. Due to these findings, 55 adults (age range: 18-40 years) completed the battery twice at 10-minute test-retest intervals (i.e., to eliminate the initial practice effect), and a third time at an interval of one month. No practice effects were observed. The implications of the results are discussed in terms of methods that can be adopted in order to minimize practice effects when this particular cognitive battery is used.

Unchanged rat brain amyloid precursor protein levels after exposure to benzodiazepines in vivo

BACKGROUND AND OBJECTIVE

Recent studies emphasize a positive correlation between (cardiac) surgical interventions and increased risk for developing Alzheimer's disease in the late postoperative period. Since amyloid precursor protein and its neurotoxic derivatives play key roles in the development of Alzheimer's dementia, the impact of several agents used in the intra- and perioperative period is examined.

METHOD

Amyloid precursor protein concentrations were assessed by semi-quantitative Western-immunoblot in brains of rats following intraperitoneal treatment with diazepam and midazolam.

RESULTS

There were no significant changes in the amyloid precursor protein concentrations.

CONCLUSION

Both diazepam and midazolam are considered to be relatively safe with respect to amyloid precursor protein metabolism.

Cognitive and neurobehavioral dysfunction after cardiac bypass procedures

From a cognitive standpoint, CABG as currently practiced appears to be safe for the great majority of patients, but transient changes involving memory, executive functions, and motor speed may still occur in a subset of patients during the first few days to weeks after CABG. The etiology most likely is multifactorial and includes a synergistic effect of microemboli, hypo-perfusion, and other variables associated with major surgery. Older age and degree of pre-existing cerebrovascular disease have been identified as important risk factors. The short-term cognitive changes appear to be reversible by 3 months after surgery for most patients. Late cognitive decline after CABG,occurring between 1 and 5 years after the surgery, has been well documented,but controlled studies demonstrating that this decline is specifically attributable to the use of cardiopulmonary bypass itself rather than to progression of underlying cerebrovascular disease or other age-related changes are pending.

Cardiopulmonary Rehabilitation and Cancer Rehabilitation. 1. Cardiac Rehabilitation Review

Cardiac rehabilitation includes not only the rehabilitation of people with ischemic heart disease but also those with congestive heart failure, heart transplantation, congenital heart disease, and other conditions. New advances in medical treatment have arisen, and there are new approaches in treatment, including alternative medicine and complementary care. New surgical approaches that help restore cardiac function have also been introduced, and rehabilitation professionals must be aware of these advances and be able to incorporate this knowledge into the practice of rehabilitation medicine.

OVERALL ARTICLE OBJECTIVES

(a) To identify major categories of cardiac disease, (b) to elucidate appropriate interventions and support for patients with coronary artery disease, (c) to describe the new interventions available for the treatment of cardiac disease, and (d) to describe the appropriate role of cardiac rehabilitation for people with various forms of cardiac disease.

Cognitive Outcomes Three Years After Coronary Artery Bypass Surgery: A Comparison of On-Pump Coronary Artery Bypass Graft Surgery and Nonsurgical Controls

BACKGROUND

Coronary artery bypass grafting has been associated with both early and late postoperative cognitive decline, but interpretation of previous studies has been limited by lack of appropriate control groups. We compared changes in cognitive performance from baseline to 3 years in patients undergoing coronary artery bypass grafting with those of a control group of patients with known risk factors for coronary artery disease but without surgery.

METHODS

Patients undergoing coronary artery bypass grafting (n = 140) and a demographically similar nonsurgical control group with coronary artery disease (n = 92) completed baseline neuropsychological assessment and were followed up prospectively at 3, 12, and 36 months. Cognitive performance was assessed with a battery of neuropsychological tests, measuring the cognitive domains of attention, language, verbal and visual memory, visuospatial, executive function, and psychomotor and motor speed. The statistical analyses were performed in two ways: using data from all tested individuals, and using a model imputing missing observations for individuals lost to follow-up.

RESULTS

Both the coronary artery bypass grafting and nonsurgical control groups improved from baseline to 1 year, with additional improvement between 1 and 3 years for some cognitive tests. The coronary artery bypass grafting group had statistically significantly greater improvement than the nonsurgical controls for some subtests, and had a comparable longitudinal course for the remainder of the subtests. Both study groups had a trend toward nonsignificant decline at 3 years on some measures, but the overall differences between groups over time were not statistically significant.

CONCLUSIONS

Prospective longitudinal neuropsychological performance of patients with coronary artery bypass grafting did not differ from that of a comparable nonsurgical control group of patients with coronary artery disease at 1 or 3 years after baseline examination. This finding suggests that previously reported late cognitive decline after coronary artery bypass grafting may not be specific to the use of cardiopulmonary bypass, but may also occur in patients with similar risk factors for cardiovascular and cerebrovascular disease.

Neurocognitive complications after coronary artery bypass surgery

Both short- and long-term cognitive changes continue to occur after coronary artery bypass grafting (CABG), but the pathophysiology of these neurobehavioral changes remains incompletely understood. The persistence of mild postoperative neurocognitive changes despite multiple improvements in the cardiopulmonary bypass procedure may be partially because of surgical populations being older and having more prevalent comorbid disease. The cause of the early postoperative changes is most likely multifactorial and may include ischemic injury from microemboli, hypoperfusion, and other factors resulting from major surgery. Several lines of evidence suggest that the late cognitive decline between 1 and 5 years after surgery may be secondary to high rates of cerebrovascular disease among candidates for CABG. A history of hypertension and other risk factors for vascular disease is known to be associated with increased risk for long-term cognitive decline in community-dwelling elderly individuals. Cerebrovascular risk factors are also associated with silent magnetic resonance imaging abnormalities in patients undergoing CABG. Thus, whereas both short- and long-term postoperative cognitive changes have been associated with CABG, only the short-term, transient changes appear to be directly related to the use of cardiopulmonary bypass.

Age effects of coronary artery bypass graft on cognitive status change among elderly male twins

Background: Research regarding long-term cognitive outcome following coronary artery bypass graft (CABG) is inconsistent, which may be due in part to differential genetic and environmental influences within most study samples.

Methods: The authors examined the effect of CABG on cognitive status change scores in members of the National Academy of Sciences–National Research Council Twins Registry of World War II veterans. Subjects were administered the modified Telephone Interview for Cognitive Status (TICS-m) at approximately 3-year intervals between 1990 and 2002 as part of an epidemiologic study of dementia.

Results: Based on co-twin control analyses using a repeated-measures analysis of variance matching twins discordant for CABG within the pair (n = 464 individuals) across three age categories (63 to 70, 71 to 73, 74 to 83), the authors found at follow-up that men who had CABG between ages 63 and 70 showed an increase in TICS-m scores and performed better than their co-twin who did not have the procedure. No significant differences were found within twin pairs for the older two age groups following CABG surgery. This age effect was replicated when comparing individuals positive for CABG surgery with nonfamilial, age- and education-matched controls who were negative for CABG.

Conclusions: In this study of twin pairs who share many genetic and environmental risks for cerebrovascular problems, the results suggest that timing of the CABG procedure may be important to predicting positive cognitive outcomes.

Detection of cognitive decline after coronary surgery: a comparison of computerized and conventional tests

BACKGROUND

Postoperative cognitive decline is a common complication after coronary artery bypass graft (CABG) surgery. Postoperative cognitive decline is defined on the basis of change in cognitive function detected with repeated assessments using neuropsychological tests. Therefore improvement in neuropsychological testing instruments may increase our understanding of postoperative cognitive decline.

METHODS

Fifty patients undergoing CABG surgery completed both a conventional and a computerized battery of tests before and 6 days after CABG surgery. Fifty age- and education-matched controls completed the same test batteries 6 days apart. The reliability and the sensitivity to postoperative cognitive decline were computed for each battery.

RESULTS

Both test batteries detected postoperative cognitive decline 6 days after CABG surgery. For the computerized battery, the reliability of the reaction times (intraclass correlation 0.89-0.92) was greater than for any test from the conventional battery (intraclass correlation 0.56-0.71), although accuracy measures were less reliable (intraclass correlation 0.61-0.89). The computerized battery detected all the cases of POCD identified by the conventional test battery and also five cases that were classified as normal by the conventional tests.

CONCLUSION

Computerized tests are suitable for measuring cognitive change after CABG surgery and may detect change in a greater proportion of patients 6 days after CABG surgery than conventional neuropsychological tests.

Perioperative management of patients with neurologic disease

Because many of the perioperative problems of the neurologic patient are predictable, they should be anticipated by the neurologist so that measures can be taken to prevent as many complications as possible and to recognize and manage those that cannot be prevented in a timely, efficient manner.

Reduced rate of microembolism by optimized aortic cannula position does not influence early postoperative cognitive performance in CABG patients

BACKGROUND AND PURPOSE

The number of microemboli as measured by Doppler ultrasound during coronary artery bypass grafting (CABG) can be reduced by positioning the arterial cannula into the aorta descendens. The aim of this study was to prospectively evaluate whether this alternative aortic cannulation procedure leads to better neuropsychologic outcome early after surgery along with embolus reduction.

METHODS

Sixty patients with elective CABG were randomized to either using a short aorta ascendens cannula or an elongated cannula placed in the aorta descendens. All patients were tested by seven neuropsychologic tests preoperatively. Intraoperative embolus detection could be performed by transcranial Doppler in 32 patients. The neuropsychologic tests could be repeated serially until the 9th postoperative day in 54 patients. Patient groups did not differ in terms of preoperative psychometric performance and of the surgical characteristics except cannula positioning. All data were analyzed by a blinded assessor.

RESULTS

Neuropsychologic test scores showed in all individual patients a transient decline with subsequent recovery, but did not differ significantly between the groups except for the letter cancellation test at discharge favoring the patients with the longer cannula (102.3 +/- 11.6 vs. 94.5 +/- 11.5 mean +/- SD; p = 0.025). In the subgroup who had Doppler sonography, neuropsychologic test scores did not differ between the groups. However, microembolic signals were markedly reduced in patients with the elongated cannula (median 174.5 vs. 413.0; p = 0.011).

CONCLUSIONS

Though reducing brain microembolism, use of an elongated aortic cannula does not appear to influence overall cognitive performance early after CABG in this pilot study.

Liberation From Mechanical Ventilation Following Heart Surgery

The definition of ventilator dependency following heart surgery has evolved from a requirement for mechanical ventilation for more than 48 hours to less than 24 hours. Minimization of risk factors assessed in the preoperative period and improved surical and anesthetic techniques lead to improved and shortned postoperative courses and decreased hospital lengths of stay. The management of ventilator dependency following heart surgery should be approached from the perspective of pre-intensive care unit, intensive care unit, and post-intensive care unit Issues. A thorough understanding of risk factors for adverse postoperative morbidity and mortality leads to foused intraoperative and postoperative management aimed at improved quality of life following surgery. Minimizing preoprative risks and matching the postoperative state with criteria for the ideal candidate for early extubation improves outcome and minimizes requirements for mechanical ventilation in the postoperative period. In the event of prolonged requirements for mechanical ventilation, correcting impediments to weanng from mechanical ventilation provides the best circumtances to facilitate the process of rehabilitation and liberaion from mechanical ventilation.

Cerebral oxygen saturation assessed by near-infrared spectroscopy during coronary artery bypass grafting and early postoperative cognitive function

BACKGROUND

Cerebral oxygen saturation (ScO2) can be assessed by near-infrared spectroscopy. We investigated the correlation between early postoperative cognitive performance and intraoperative ScO2 in a prospective observational setting.

METHODS

Forty-seven patients undergoing elective coronary artery bypass grafting with cardiopulmonary bypass underwent preoperative and postoperative neuropsychological evaluation. Patients were classified according to the presence or absence of postoperative cognitive dysfunction. Cognitive dysfunction was defined as an individual test score decrease of more than one standard deviation in two or more of the five tests. During operation ScO2 was continuously measured using an INVOS 4100 device. Cerebral oxygen saturation values were analyzed with reference to two cutoff points, which should reflect low cerebral oxygenation: an ScO2 less than 40% and a drop of more than 25% from individual baseline values. The duration and extent of ScO2 values below these two cutoff points was compared between the patients with and without cognitive dysfunction.

RESULTS

Sixteen patients (34%) showed postoperative cognitive dysfunction. Cerebral oxygen saturation values less than 40% occurred in 17 patients for a mean (+/- standard error of the mean) of 17.2 +/- 6.5 minutes, whereas a decrease of more than 25% from baseline values occurred in 37 patients for 52.7 +/- 7.8 minutes. The duration and extent below the two cutoff ScO2 values was similar in patients with and without cognitive dysfunction.

CONCLUSIONS

Intraoperative regional ScO2 as assessed by near-infrared spectroscopy with the INVOS 4100 device is not predictive for postoperative cognitive performance in patients undergoing coronary artery bypass grafting with cardiopulmonary bypass.

Serum creatinine patterns in coronary bypass surgery patients with and without postoperative cognitive dysfunction

Renal dysfunction is common after coronary artery bypass graft (CABG) surgery. We have previously shown that CABG procedures complicated by stroke have a threefold greater peak serum creatinine level relative to uncomplicated surgery. However, postoperative creatinine patterns for procedures complicated by cognitive dysfunction are unknown. Therefore, we tested the hypothesis that postoperative cognitive dysfunction is associated with acute perioperative renal injury after CABG surgery. Data were prospectively gathered for 282 elective CABG surgery patients. Psychometric tests were performed at baseline and 6 wk after surgery. Cognitive dysfunction was defined both as a dichotomous variable (cognitive deficit [CD]) and as a continuous variable (cognitive index). Forty percent of patients had CD at 6 wk. However, the association between peak percentage change in postoperative creatinine and CD (parameter estimate = -0.41; P = 0.91) or cognitive index (parameter estimate = -1.29; P = 0.46) was not significant. These data indicate that postcardiac surgery cognitive dysfunction, unlike stroke, is not associated with major increases in postoperative renal dysfunction.

IMPLICATIONS

We previously noted that patients with postcardiac surgery stroke also have greater acute renal injury than unaffected patients. However, in the same setting, we found no difference in renal injury between patients with and without cognitive dysfunction. Factors responsible for subtle postoperative cognitive dysfunction do not appear to be associated with clinically important renal effects.

Coronary-artery bypass surgery and the brain: persisting concerns

Mortality after coronary-artery bypass surgery (CABS) has fallen steadily over recent years. Concern remains, however, about the effect of this surgery on the brain. The problem of brain damage after CABS is multifactorial, involving microembolism, disturbed perfusion, metabolic derangement, and inflammatory responses. Microemboli numbers have been linked to the likelihood of neuropsychological deterioration after surgery. Risk factors for cerebral changes after CABS include older age, gender, neurological disease, diabetes, and calcification of the aorta. These risk factors are important because, in comparison with the early 1990s, patients undergoing CABS are now older and tend to have a greater number of comorbid conditions. Changes in surgical technique, such as the introduction of arterial-line filters and membrane oxygenators, have led to a reduction of both microemboli and neuropsychological disturbance. However, the problem persists, prompting further studies on surgical technique and neuroprotective strategies.

Brain microembolic counts during extracorporeal circulation depend on aortic cannula position

Thrombofibrinous and gaseous brain microemboli are commonly observed during extracorporeal circulation in patients undergoing cardiac surgery. Recent studies showed a preference of microemboli to the left hemisphere. We hypothesized that placement of the aortic cannula tip within the aorta descendens rather than in the aorta ascendens as commonly used reduces the number of microemboli to the brain and also reduces the side preference. Of 60 patients undergoing elective coronary artery bypass grafting primarily randomized to either a short aortic cannula (aorta ascendens) or an elongated one (aorta descendens), 29 (16 and 13) patients had complete and technically perfect continuous intraoperative transcranial Doppler sonography with embolus detection bilaterally. The number of high-intensity transient signals (HITS) was 994 +/- 2118 (mean +/- SD) for the short cannula group and was significantly lower with the elongated cannula (223 +/- 208; p < 0.02). HITS counts per min also differed significantly in favour of the aorta descendens group (p < 0.02), but there was an overlap. Thus, elongated cannulas can reduce, but not prevent microembolism to the brain. The side-to-side ratio of microemboli revealed more events in the left hemisphere, but this was similar in both groups. This suggests that individual anatomic factors may be responsible for this hemodynamically-mediated effect.

Similar neurobehavioral outcome after valve or coronary artery operations despite differing carotid embolic counts

OBJECTIVES

The interrelationships among coronary and valvular operations, microemboli, and neurobehavioral outcome are unclear. We hypothesized that adult patients undergoing cardiac valve operations would have more total emboli delivered to the brain than patients undergoing coronary artery bypass grafting and that this would associate with worse neurobehavioral outcomes.

METHODS

One hundred ninety-three patients undergoing coronary artery bypass grafting and 73 patients undergoing cardiac valve operations were compared. Patients received neurologic, neuro-ophthalmologic, and 11 standardized neurobehavioral tests preoperatively and 5 to 7 days, 1 month, and 6 months postoperatively. Left common carotid Doppler ultrasonographic embolus detection was performed intraoperatively. Repeated measures and logistic regression analyses of outcome were performed.

RESULTS

Patients undergoing either coronary or valve operations were well matched by age (61 +/- 10 and 59 +/- 12 years, respectively), but a significantly greater fraction of patients undergoing valve operations were female, diabetic, or had undergone previous cardiac operations. Neurobehavioral scores of patients undergoing either coronary artery bypass grafting or cardiac valve operations did not differ significantly at any time. Total embolus counts differed significantly: the median was 105 during coronary artery bypass grafting and 479 during cardiac valve operations (geometric means of 104 and 412, respectively; P =.0001). Significantly more emboli were detected in the patients undergoing cardiac valve operations after removal of the left ventricular vent and after separation from cardiopulmonary bypass, but comparable numbers of emboli were seen in the 2 groups before cardiopulmonary bypass. In both groups decreased neurobehavioral performance was apparent at 5 to 7 days, with improvement at 1 and 6 months. Increasing numbers of carotid emboli significantly associated with worse performance on the letter cancellation test. There were no significant differences between patients undergoing valve and coronary operations in neurobehavioral outcomes, strokes, transient ischemic attacks, or deaths.

CONCLUSIONS

The significantly greater number of emboli in the group of patients undergoing cardiac valve operations is likely the result of the entrainment of intracardiac air. The greater numbers of emboli during cardiac valve operations do not appear associated with a commensurately greater risk of adverse neurologic or neurobehavioral outcome.