Cognitive function after open-heart surgery: are postoperative neuropsychological deficits caused by cardiopulmonary bypass?

Preoperative preparation of the surgical patient with neurologic disease

This article emphasizes some key points in the preoperative evaluation of patients with neurologic disease. The amount of neurologic disease in the general population is a difficult number to assess accurately. This is, in part, because of the wide-sweeping scope of neurologic disease. The International Classification of Diseases has the highest number of conditions attributable to neurologic disease. Patients with neurologic disease are commonly encountered, and their illness is often complicated by significant comorbid disease. It is important to think of the patient as a whole rather than the sum of his or her systems. While it is tempting to consider the traditional preoperative evaluation from a "cardiac clearance" point of view, we must resist this urge, and evaluate which risk factors we can modify and hopefully mitigate to optimize the perioperative period.

Preoperative preparation of the surgical patient with neurologic disease

This article emphasizes some key points in the preoperative evaluation of patients with neurologic disease. The amount of neurologic disease in the general population is a difficult number to assess accurately. This is, in part, because of the wide-sweeping scope of neurologic disease. The International Classification of Diseases has the highest number of conditions attributable to neurologic disease. Patients with neurologic disease are commonly encountered, and their illness is often complicated by significant comorbid disease. It is important to think of the patient as a whole rather than the sum of his or her systems. While it is tempting to consider the traditional preoperative evaluation from a "cardiac clearance" point of view, we must resist this urge, and evaluate which risk factors we can modify and hopefully mitigate to optimize the perioperative period.

The angiotensin AT4 receptor subtype as a target for the treatment of memory dysfunction associated with Alzheimer's disease

Over recent years antihypertensive drugs, particularly angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs), have been reported to have beneficial effects upon cognitive impairment. Such findings suggest that pharmacological manipulation of angiotensin ligands may be of clinical importance in slowing or halting the cognitive deterioration seen in vascular dementia and Alzheimer's disease. The mechanism(s) underlying these improvements in cognitive function remains unclear; however, important leads are emerging. The angiotensin AT4 receptor subtype, discovered by our laboratory in 1992, influences several important behaviours and physiologies, including learning and memory, and may play a role in this cognitive improvement. This review initially describes the therapeutic drugs approved by the Federal Drug Administration and new approaches presently being developed to treat Alzheimer's disease-induced cognitive impairment. Next, the biologically-active angiotensin ligands and their respective receptor subtypes are discussed, followed by the roles of angiotensin II, angiotensin IV, ACE inhibitors and ARBs in cognitive function. We conclude with a working hypothesis concerning the importance of the AT4 receptor subtype as a new potential drug target for the treatment of Alzheimer's disease-associated memory loss.

Anaortic techniques reduce neurological morbidity after off-pump coronary artery bypass surgery

BACKGROUND

Stroke remains one of the most devastating complications of cardiac surgery. Advocates of off-pump coronary revascularisation (OPCAB) maintain that post-operative neurologic morbidity is reduced by avoiding aortic cannulation and cross-clamping, and by eliminating the systemic effects of cardiopulmonary bypass. We sought to determine whether completing off-pump coronary surgery without any aortic manipulation ("anaortic" technique) afforded any additional neurological protection, as compared to off-pump grafting in which the aorta was utilised for graft inflow.

METHODS

A comprehensive review of prospectively collected data was undertaken of all patients undergoing OPCAB in our institution between January 2002 and December 2006. Cases requiring intra-operative conversion to cardiopulmonary bypass were excluded from further analysis. Patients having OPCAB surgery with aortic manipulation were compared to those having OPCAB surgery without aortic manipulation. Multiple logistic regression was used to identify possible predictors of post-operative neurologic morbidity, with particular focus on the role of aortic manipulation.

RESULTS

During the period of review, 1758 patients underwent OPCAB, of which 1201 (68.3%) were completed without aortic manipulation, constituting the "anaortic" cohort. This group was compared with the remaining 557 patients, which included fashioning at least one aorto-conduit anastomosis, utilising either a side-biting aortic clamp or a no-clamp proximal anastomotic device. The two groups of patients were well-matched with respect to risk factors for adverse neurologic outcomes. Nine patients sustained focal neurological deficits (transient or permanent) in the peri-operative period, constituting a stroke rate of 0.51% for the entire series. The incidence of peri-operative neurological deficit in the anaortic group was 0.25% compared with 1.1% in the aortic manipulation group (odds ratio (OR) 0.23, 95% confidence interval (CI) 0.06-0.92, p=0.037). Advanced age was also associated with peri-operative neurological injury (OR 1.1, 95% CI 1.01-1.20, p=0.017).

CONCLUSIONS

Off-pump coronary artery surgery is associated with a low incidence of peri-operative stroke. Completing the surgical procedure without manipulating the ascending aorta in any way ("anaortic" technique) offers additional neurological protection and should be the goal in all suitable off-pump coronary cases.

The Cardiotomy Trial

Background— Reinfusion of unprocessed cardiotomy blood during cardiac surgery can introduce particulate material into the cardiopulmonary bypass circuit, which may contribute to postoperative cognitive dysfunction. On the other hand, processing of this blood by centrifugation and filtration removes coagulation factors and may potentially contribute to coagulopathy. We sought to evaluate the effects of cardiotomy blood processing on blood product use and neurocognitive functioning after cardiac surgery.

Methods and Results— Patients undergoing coronary and/or aortic valve surgery using cardiopulmonary bypass were randomized to receive unprocessed blood (control, n=134) or cardiotomy blood that had been processed by centrifugal washing and lipid filtration (treatment, n=132). Patients and treating physicians were blinded to treatment assignment. A strict transfusion protocol was followed. Blood transfusion data were analyzed using Poisson regression models. The treatment group received more intraoperative red blood cell transfusions (0.23±0.69 U versus 0.08±0.34 U, P =0.004). Both red blood cell and nonred blood cell blood product use was greater in the treatment group and postoperative bleeding was greater in the treatment group. Patients were monitored intraoperatively by transcranial Doppler and they underwent neuropsychometric testing before surgery and at 5 days and 3 months after surgery. There was no difference in the incidence of postoperative cognitive dysfunction in the 2 groups (relative risk: 1.16, 95% CI: 0.86 to 1.57 at 5 days postoperatively; relative risk: 1.05, 95% CI: 0.58 to 1.90 at 3 months). There was no difference in the quality of life nor was there a difference in the number of emboli detected in the 2 groups.

Conclusions— Contrary to expectations, processing of cardiotomy blood before reinfusion results in greater blood product use with greater postoperative bleeding in patients undergoing cardiac surgery. There is no clinical evidence of any neurologic benefit with this approach in terms of postoperative cognitive function.

Cognitive Function in Candidates for Coronary Artery Bypass Graft Surgery

BACKGROUND

While many studies have investigated cognitive impairments in patients after coronary artery bypass graft surgery, very few have closely evaluated presurgical cognitive functioning of bypass candidates.

METHODS

A battery of neuropsychologic tests was administered to a consecutive series of patients listed for bypass surgery (n = 109). Cognitive function of bypass candidates was compared with that of a healthy control group (n = 25) and published test norms.

RESULTS

Cognitive test scores in candidates for bypass were significantly lower than those of the control group on tests of attention, information processing speed, and verbal memory. Additionally, bypass candidates' cognitive test scores were significantly reduced compared with expected values derived from validated test norms, on all but one cognitive test.

CONCLUSIONS

Cognitive performances of candidates for bypass were significantly lower than those of a healthy control group and published cognitive test norms.

Pharmacological strategies for the prevention of Alzheimer's disease

This review examines key pharmacological strategies that have been clinically studied for the primary or secondary prevention of Alzheimer's disease. Much information (neuropsychological, genetic and imaging) is already available to characterise an individual's risk for developing Alzheimer's disease. However, regulatory pathways for obtaining a prevention indication are less well charted, and such trials tend to involve 3- to 7-year studies of 1000 - 5000 individuals, depending on baseline status. Treatments developed for prevention will also need to have superior safety. For these reasons, > 100 proprietary pharmacological products are currently being developed for an Alzheimer's disease treatment, but only a few are being studied for prevention. Randomised trial data are available for antihypertensive agents (calcium channel blockers, angiotensin-converting enzyme inhibitors), pravastatin, simvastatin, conjugated oestrogen, raloxifene, rofecoxib, CX516 (AMPA agonist) and cholinesterase inhibitors regarding efficacy for Alzheimer's disease prevention. At least four large prevention trials of conjugated oestrogen, selenium and vitamin E, Ginkgo biloba and statins are currently underway. Strategies using other agents have not yet been evaluated in Alzheimer's disease prevention clinical trials. These include anti-amyloid antibodies, active immunisation, selective secretase inhibitors and modulators, microtubule stabilisers (e.g., paclitaxel), R-flurbiprofen, xaliproden, ONO-2506, FK962 (somatostatin releaser), SGS 742 (GABA(B) antagonist), TCH 346 (apoptosis inhibitor), Alzhemedtrade mark, phophodiesterase inhibitors, rosiglitazone, leuprolide, interferons, metal-protein attenuating compounds (e.g., PBT2), CX717, rasagaline, huperzine A, antioxidants and memantine. Studies combining lifestyle modification and drug therapy have not been conducted. Full validation of surrogate markers for disease progression (such as amyloid imaging) should further facilitate drug development. Reducing the complexity of prevention trials and gaining regulatory consensus of design is a high priority for the field.

Neurologic Injury Associated with CABG Surgery: Outcomes, Mechanisms, and Opportunities for Improvement

Neurologic injuries, whether subtle or overt, are a major source of morbidity secondary to coronary artery bypass graft (CABG) surgery. A comprehensive review of research in the area of neurologic injury is provided. We conclude this article by providing insight regarding areas requiring further investigation in order to reduce sustainably the risk of these iatrogenic events among patient undergoing CABG surgery.

Cerebral cortical oxygenation changes during OPCAB surgery

BACKGROUND

We investigated the changes occurring in cerebral cortical oxygenation during off-pump coronary artery bypass (OPCAB) surgery using near infrared spectroscopy (NIRS).

METHODS

Measurement of cerebral cortical oxygenation changes included concentration of deoxygenated hemoglobin [HHb], oxygenated hemoglobin [O(2)Hb], changes in the redox status of the cytochrome c oxidase [Cyt-Ox], cerebral saturation as expressed by the tissue oxygenation index (TOI), and cerebral blood volume (CBV) as expressed by tissue hemoglobin index (THI). Measurements were performed in 23 consecutive patients during grafting of: left anterior descending (LAD setup 1; n = 23), posterior descending (PDA setup 2; n = 17), and Circumflex (Cx setup 3; n = 19) coronary arteries. Measurements were performed before any surgical manipulation (baseline), following positioning of the pressure stabilizer during construction of the distal anastomosis and 2 minutes after the completion of each distal anastomosis with the heart returned to its natural position.

RESULTS

There were no in-hospital deaths, neurologic deficits, or myocardial infarcts. Compared to baseline, during LAD grafting there was a marked reduction in [O(2)Hb] [-1.08 (-1.77 to -0.39), mean difference (95% CI) (p < 0.0008)], without a significant change in [HHb]. There was also a 4% reduction in cerebral saturation and a 3% fall in CBV (both p < 0.05). Setup 2 (PDA) was associated with a marked decrease of [O(2)Hb] [-1.92 (-2.95 to -0.88) mean difference (95% CI) (p < 0.0025)], which was accompanied by an increase in [HHb] [1.89 (1.00 to 2.77) mean difference (95% CI) (p < 0.0025)], and a 4% reduction in cerebral saturation (p < 0.0008). Grafting of the Cx was associated with a marked increase in [HHb] [2.85 (1.46 to 4.2) mean difference (95% CI) (p < 0.0025)], with no changes in [O(2)Hb], a 6% reduction in cerebral saturation, and a 12% increase in CBV (both p < 0.05). In all 3 settings, however, the changes were not associated with a modification in the redox state of [Cyt-Ox]. On returning to baseline condition, the changes in [O(2)Hb] and TOI observed in setup 1 persisted, and a significant reduction was observed in the redox state of the [Cyt-Ox] when compared with baseline [-0.08 (-0.14 to -0.02) mean difference (95% CI) (p < 0.002)]. For setups 2 and 3 there was recovery of the cerebral cortical oxygenation.

CONCLUSIONS

Grafting of the LAD on the beating heart is responsible for changes in cerebral cortical oxygenation which persist early after returning the heart to its natural position. Grafting of the Cx and PDA result in transient reversible changes. Trendelenburg positioning and right lateral tilting of the operating table during grafting of lateral and posterior walls might have a protective role in preventing cerebral cortical ischemia. Further studies are needed to assess the clinical importance of these observations.

Off-pump myocardial revascularization using the Octopus tissue stabilizer system

Off-pump coronary artery bypass surgery (OPCAB) has changed the approach to contemporary coronary surgery. Development of new surgical devices and techniques has reduced morbidity and mortality during off-pump surgery. From March 2000-April 2002, a total of 136 patients underwent open heart surgery using off-pump technique and fast-track anesthesia at Dedinje Cardiovascular Institute. Octopus Medtronic coronary stabilizer was used for stabilization of targeted vessel. Arterial grafts were used 169 times and saphenous vein 69 times. Average number of anastomoses was 1,830,73 per patient. One patient (0.74%) died. Three patients (2.21%) underwent surgery revision due to postoperative bleeding and one (0.74%) because of graft dysfunction. Perioperative myocardial infarction was registered 2 times (1.47%), pneumothorax 3 times (2.21%), postoperative arrhythmias 11 times (8.09%), transitory ischemic attack once (0.74%) and deep wound infection once (0.74%). Twelve patients (8.82%) required prolonged inotropic support. Angiographies early revealed patent grafts in 8 patients (5.88%). OPCAB is a safe and effective alternative approach to coronary artery revascularization. Use of coronary stabilizer has improved the safety and quality of OPCAB surgery.

In the eye of both patient and spouse: memory is poor 1 to 2 years after coronary bypass and angioplasty

BACKGROUND

The study aimed to investigate patient and spouse perception of cognitive functioning 1 to 2 years after coronary artery bypass grafting.

METHODS

Seventy-six married patients who had undergone coronary artery bypass grafting were selected and sex- and age-matched with 75 concurrent married patients who had undergone percutaneous transluminal coronary angioplasty. Couples received a letter of explanation and then completed telephone interviews. Forty-seven questions assessed memory, concentration, general health, social functioning, and emotional state. Response choices were: improved, unchanged, or deteriorated function after coronary artery bypass grafting/percutaneous transluminal coronary angioplasty.

RESULTS

Patients who had undergone coronary artery bypass grafting did not differ in subjective ratings on any measure from patients who had undergone percutaneous transluminal coronary angioplasty. There were no differences between spouses in the respective groups; spouse ratings also did not differ from patient ratings. Only in memory function did patients and spouses report a postprocedural decline.

CONCLUSIONS

No subjective differences were found in patients who had undergone either coronary artery bypass grafting or percutaneous transluminal coronary angioplasty. Spouse ratings agreed with each other and with patient ratings. Positive correlations were found between the questionnaire factors, suggesting that perceived health and well-being are associated with subjective cognition.

Predictors of stroke in the modern era of coronary artery bypass grafting: a case control study

BACKGROUND

Stroke is a rare but devastating complication after coronary artery bypass grafting (CABG) and its prevention remains elusive. We used a case control design to investigate the extent to which preoperative and perioperative factors were associated with occurrence of stroke in a cohort of consecutive patients undergoing myocardial revascularization.

METHODS

From April 1996 to March 2001, data from 4,077 patients undergoing CABG were prospectively entered into a database. The association of preoperative and perioperative factors with stroke was investigated by univariate analyses. Factors observed to be significantly associated with stroke in these analyses were further investigated using multiple logistic regression to estimate the strength of the associations with the occurrence of stroke, after taking account of the other factors.

RESULTS

During the study period, 4,077 patients underwent CABG and of these 923 (22.6%) had off-pump surgery. Forty-five patients suffered a perioperative stroke (1.1%). Overall there were 46 in-hospital deaths (1.1%), of whom 6 also suffered a stroke. Brain imaging of the stroke patients showed embolic lesions in 58%, watershed in 28%, and mixed in 14%. Multivariate regression analysis identified several preoperative factors as independent predictors of stroke, ie, age, unstable angina, serum creatinine greater than 150 mcg/ml, previous cerebrovascular accident (CVA), peripheral vascular disease (PVD), and salvage operation. When operative risk factors were added to the adjusted model, off-pump surgery was associated with a substantial, but not significant, protective effect against stroke (odds ratio = 0.56, 95% confidence interval 0.20 to 1.55). Survival for stroke patients was 93% and 78% at 1 and 5 years, respectively.

CONCLUSIONS

Overall incidence of stroke is relatively low in our series. Age, unstable angina, previous CVA, PVD, serum creatinine greater than 150 mcg/ml, and salvage operation are independent predictors of stroke. These factors should be taken into account when informing each individual patient on the possible risk of stroke and in the decision-making process on the surgical strategy.

Atypical cognitive profile in patients with depression after myocardial infarction

BACKGROUND

We evaluated the cognitive profile of 48 patients with major depression following their first myocardial infarction (MI).

METHODS

The cognitive performance of the patients was compared with the performance of 48 non-depressed MI patients and 48 healthy controls.

RESULTS

Depressed MI patients performed slower on a simple cognitive speed related measure compared with non-depressed MI patients and healthy controls. Attention and speed-related aspects of cognitive functioning were not affected. Surprisingly, (depressed) MI patients showed even better performances with respect to memory function.

LIMITATION

No patients with non-MI-related depression were included.

CONCLUSIONS

The cognitive profile of major depression after MI differs from that of non-cardiac-related depressive disorder, as described in the literature. This may reflect a different etiology of post MI depression from non-cardiac-related depression.

Postoperative cognitive dysfunction versus complaints: a discrepancy in long-term findings

This review describes the discrepancy in findings between postoperative cognitive performance and postoperative cognitive complaints long time after an operation under general anesthesia. Shortly (from 6 hr to 1 week) after an operation a decline in cognitive performance is reported in most studies. However, long time (from 3 weeks to 1-2 years) after an operation this is rarely found although some patients are still reporting cognitive complaints. In general this kind of research is suffering from severe methodological problems (use of insensitive tests, lack of control groups, lack of parallel tests, different definitions of cognitive decline). However, these problems cannot totally explain the discrepancy in findings in the long term. Thus, there are patients who have persistent cognitive complaints long time after an operation, that cannot be measured with cognitive tests. More psychological factors such as fixation on short-term cognitive dysfunction, mood, coping style, and personality are possible explanations for these cognitive complaints in the long term. As a consequence, these factors should be a topic in future research elucidating the persistence of these cognitive complaints long time after an operation under general anesthesia.

Off-pump coronary artery bypass grafting: new developments but a better outcome?

Off-pump coronary artery surgery is now performed safely and effectively without cardiopulmonary bypass. This review includes indications, approaches, anaesthetic and haemodynamic management, and compares the occurrence of postoperative complications and multiorgan dysfunction with conventional cardiac surgery.

Neurological and cognitive disorders after coronary artery bypass grafting

Cerebral injury is a major cause of mortality and morbidity of coronary artery bypass grafting. Stroke occurs in 3% of patients and is largely caused by embolization of atheromatous debris during manipulation of the diseased aorta. Cognitive impairment, which is predominantly caused by microembolization of gaseous and particulate matter, mainly generated by cardiotomy suction, is more common. Demonstration of similar cognitive impairment in patients operated on without cardiopulmonary bypass indicates that other pathophysiological mechanisms, such as anaesthesia and hypoperfusion, are also involved. Advances in medical, anesthetic, and surgical management have resulted in a reduction in the incidence of neurological injury in CABG patients over the past decade. On the other hand, an increasingly elderly population with more severe comorbidity, who are more prone to cerebral injury, are increasingly being referred for CABG. Possible mechanisms to reduce overt and subtle cerebral injury are discussed. The use of composite arterial grafts performed on the beating heart may be the most effective way of minimizing the risk of cerebral injury associated with CABG.

Developmental and neurologic effects of alpha-stat versus pH-stat strategies for deep hypothermic cardiopulmonary bypass in infants

OBJECTIVES

In a randomized single-center trial, we compared developmental and neurologic outcomes at 1 and 2 to 4 years of age in children who underwent reparative cardiac operations at less than 9 months of age after use of the alpha-stat versus pH-stat strategy during deep hypothermic cardiopulmonary bypass.

METHODS

Among 168 children eligible for follow-up, 1-year developmental evaluations were carried out on 111, neurologic evaluations on 110, and electroencephalographic evaluations on 102. Parents of 122 children completed questionnaires on behavior and development when children were 2 to 4 years of age.

RESULTS

The Psychomotor Development Index scores of the alpha-stat and pH-stat groups did not differ significantly (P =.97). For Mental Development Index scores, the treatment group effect differed according to diagnosis (P =.007). In the D -transposition of the great arteries (n = 59) and tetralogy of Fallot (n = 36) subgroups, the pH-stat group had slightly higher Mental Development Index scores than the alpha-stat group, although these differences were not statistically significant. In the ventricular septal defect subgroup (n = 16), the alpha-stat group had significantly higher scores. Psychomotor Development Index and Mental Development Index scores were significantly higher in the group with D -transposition of the great arteries than in the other 2 groups (P =.03 and P =.01, respectively). Across all diagnoses, Mental Development Index scores were significantly higher than Psychomotor Development Index scores (P <.001). Treatment group assignment was not significantly associated with abnormalities on neurologic examination (P =.70) or electroencephalographic examination (P =.77) at 1 year or with parents' ratings of children's development (P =.99) or behavior (P =.27) at age 2 to 4 years.

CONCLUSIONS

Use of alpha-stat versus pH-stat acid-base management strategy during reparative infant cardiac operations with deep hypothermic cardiopulmonary bypass was not consistently related to either improved or impaired early neurodevelopmental outcomes.

Pre-existing cognitive impairment as a factor influencing outcome after cardiac surgery

Conventional methodology to investigate cognitive impairment after coronary artery bypass graft (CABG) surgery leaves unclear the potential for pre-existing cognitive deficits to influence outcome. Individuals with pre-existing deficits may be more vulnerable to the effects of CABG, hence biasing the results of a typical prospective trial if account is not taken of their state. The present study examined the effect of pre-existing cognitive impairment upon cognitive outcome in 81 patients undergoing CABG. Patients performed the Stroop Neuropsychological Screening Test and other psychometric assessments prior to and at 6 days and 6 months after CABG. Those with pre-existing cognitive deficits were significantly more likely to display impairment at 6-day and 6-month follow-ups than were those without pre-existing deficits. Greater age and lower pre-morbid intelligence were also significant predictors of post-CABG deficit, confirming earlier findings. The results imply both that pre-existing cognitive impairments may render patients more vulnerable to post-operative deficits and that, in the absence of such pre-existing impairments, CABG surgery does not inevitably lead to later deficits. The study also replicated previous findings showing a similar influence of pre-existing depression upon emotional state after CABG. Overall, the results confirm the importance both of a patient's pre-existing cognitive and emotional states, and the methodology to assess them, in influencing outcome after cardiac surgery and the conclusions to be drawn as to the supposed adverse effects of the procedure.

Neurocognitive dysfunction after coronary artery bypass surgery: a systematic review

OBJECTIVE

Substantial, albeit scattered, evidence suggests that coronary artery bypass grafting may impair cognitive function. As methods and definitions differ greatly across studies, the reported incidence of cognitive decline after coronary bypass surgery varies widely as well. The aim of the present study was to systematically review those studies on cognitive decline that are relatively comparable and meet with certain quality criteria.

METHODS

Four electronic databases and the references of several abstract books and earlier reviews were used to identify relevant literature. Stringent criteria, based in part on the 1994 consensus meeting on assessment of neurobehavioral outcomes after cardiac surgery, were used to assess the studies that were found. In total, 256 different titles were found, of which 23 met with the formulated selection criteria.

RESULTS

Twelve cohort studies and eleven intervention studies were evaluated. A pooled analysis of six highly comparable studies yielded a proportion of 22.5% (95% confidence interval, 18.7%-26.4%) of patients with a cognitive deficit (a decrease of at least 1 standard deviation in at least two of nine or ten tests) 2 months after the operation.

CONCLUSIONS

Neurocognitive dysfunction is a frequently occurring complication of coronary artery bypass grafting. The etiologic contribution of cardiopulmonary bypass to this complication will remain unclear until a randomized trial that directly compares off-pump and on-pump bypass surgery is carried out.

Serum S-100 protein release and neuropsychologic outcome during coronary revascularization on the beating heart: a prospective randomized study

OBJECTIVES

Our purpose was to establish whether coronary revascularization on the beating heart without cardiopulmonary bypass is less harmful to the brain than conventional surgery with cardiopulmonary bypass as indicated by measures of cognitive function or by changes in serum concentrations of S-100 protein, a recognized biochemical marker of cerebral injury.

METHODS

We conducted a prospective randomized trial in which the assessors of the outcome measures were blind to the treatment received. Sixty patients without known neurologic abnormality, undergoing coronary revascularization, were prospectively randomized to 1 of 2 groups: (1) cardiopulmonary bypass (32 degrees C-34 degrees C) and cardioplegic arrest (on pump) with intermittent antegrade warm blood cardioplegia or (2) surgery on the beating heart (off pump). Neuropsychologic performance was assessed before and 12 weeks after the operation. Serum S-100 protein concentration was measured at intervals up to 24 hours after the operation.

RESULTS

The groups had similar preoperative characteristics. There were no deaths or major neurologic complications in either group, nor was there any difference between groups in the chosen index of neurologic deterioration. Serum S-100 protein concentrations were higher in the on-pump group at 30 minutes, but any such difference between groups had disappeared 4 hours later. The extent of the changes in S-100 protein was unrelated to the index of neuropsychologic deterioration.

CONCLUSIONS

The changes in S-100 protein concentration suggest that the brain and/or blood-brain barrier may be more adversely affected during coronary artery surgery with cardiopulmonary bypass than during surgery on the beating heart, but that this may not be reflected in detectable neuropsychologic deterioration at 12 weeks.

Is cardiopulmonary bypass still the cause of cognitive dysfunction after cardiac operations?

OBJECTIVE

The purpose of this study was to determine whether cognitive impairment is related to cardiopulmonary bypass.

METHODS

Twenty-five patients undergoing coronary artery bypass grafting without cardiopulmonary bypass were matched with 50 patients undergoing coronary artery bypass grafting with cardiopulmonary bypass. All patients received the same anesthetic regimen, and one surgeon performed all the operations. A battery of 10 standard tests of neuropsychologic function were performed before, at discharge, and 3 months after the operation. A comprehensive multidimensional measure of subjective health status was used as the primary clinical measure of functional outcome.

RESULTS

The groups were similar with respect to age, sex, and ventricular function and differed only in the need for a circumflex artery graft. Both groups showed significant improvement in the comprehensive multidimensional measure of subjective health status at 3 months. At discharge most neuropsychologic tests had deteriorated in both groups (the same 4 tests had deteriorated significantly in both groups, and an additional test had deteriorated significantly in the cardiopulmonary bypass group). At 3 months all but one test in the cardiopulmonary bypass group had returned to or exceeded baseline performance. The same 2 tests had improved significantly in both groups, and a further test had improved significantly in the group without cardiopulmonary bypass. At no specific time point was there a significant difference between the absolute or change scores between the groups on any of the tests.

CONCLUSIONS

The similar pattern of early decline and late recovery of cognitive function in patients undergoing coronary artery bypass grafting with and without cardiopulmonary bypass suggests that cardiopulmonary bypass is not the major cause of postoperative cognitive impairment. This merits consideration in deciding optimal treatment strategies in coronary revascularization.

Neurobehavioural sequelae of cardiopulmonary bypass

The development of coronary artery bypass grafting (CABG) and its effect on angina is the product of a series of technical and scientific advances. Despite these advances, however, adverse neurobehavioural outcomes continue to occur. Stroke is the most serious complication of CABG, but studies that have identified demographic and medical risk factors available before surgery are an important advance. Short-term cognitive deficits are common after CABG, but may not be specific to this procedure. However, deficits in some cognitive areas such as visuoconstruction persist over time, and may reflect parieto-occipital watershed area injury secondary to hypoperfusion or embolic factors. Risk factors for cognitive decline may be time dependent, with short-term studies identifying factors that differ from those of long-term studies. Patients with depression before surgery are likely to have persistent depression afterwards. However, depression does not account for the cognitive decline after CABG. Since CABG is increasingly done in older patients with more comorbidity, the challenge is to identify patients at risk of adverse neurocognitive outcomes and to protect them by modification of the surgical procedure or by effective medical therapy.

Beating versus arrested heart revascularization: evaluation of myocardial function in a prospective randomized study

OBJECTIVE

Conventional coronary artery bypass grafting (CABG) is both safe and effective. Nevertheless, the use of cardiopulmonary bypass (CPB) and cardioplegic arrest are associated with several adverse effects. Over the last 2 years there has been a revival of interest in performing CABG on the beating heart. In this prospective randomized study we evaluated the efficacy and safety of on and off pump coronary revascularization on myocardial function.

METHODS

Eighty patients (65 males, mean age 61+/-9.7 years) undergoing first time CABG were prospectively randomized to: (i) conventional revascularization with CPB at normothermia and cardioplegic arrest with intermittent warm blood cardioplegia (on pump) or (ii) beating heart revascularization (off pump). Troponin I (Tn I) release was serially measured as a specific marker of myocardial damage. Haemodynamic measurements as well as inotropic requirement, incidence of arrhythmia and postoperative myocardial infarction were also recorded.

RESULTS

There were no significant differences between the two groups in terms of age, sex, extent of disease, left ventricular function and number of grafts. There were no deaths or intraoperative myocardial infarctions in either group. Tn I release was constantly lower in the off pump group and this was significant at 1, 4, 12 and 24 h postoperatively. Furthermore, in this group there was a significantly reduced incidence of arrhythmias. Inotropic requirements were less in the off pump group but this did not reach statistical significance.

CONCLUSION

These results suggest that off pump coronary revascularization is a safe and effective strategy for myocardial revascularization. Myocardial injury as assessed by Tn I release is also reduced when compared with conventional coronary revascularization with CPB and cardioplegic arrest.

Late neurocognitive changes from neurological damage following coronary bypass surgery

A detailed case study with neuropsychological data over a 26-year period was used to explore the relationship between neurocognitive vulnerability preoperatively and subsequent neurocognitive decline identified several years postoperatively. Guidelines regarding the importance of neuropsychological assessment of intelligence, attention, memory, language, and visual-spatial planning and organizational skills are provided. Such evaluations clarify postoperative treatment planning because rehabilitation of cardiac patients with premorbid neurocognitive deficits poses special rehabilitation problems. With a detailed neurologic history as part of the preoperative evaluation, healthcare providers can identify acute and subtle risk factors for postoperative neurologic syndromes. This may lead to interventions designed to provide increased patient and family support.

Evaluating the Effects of Treatment for Medical Disorders: Has the Value of Neuropsychological Assessment Been Fully Realized?

Cognitive functioning can be affected by medical disorders and by the regimens used to treat them. To evaluate the cognitive risks and benefits of specific medical treatments, an increasing number of medical clinical trials have included a formal neuropsychological evaluation. This selective review has three goals: (a) to survey the range of assessment techniques used with different patient populations (e.g., those with diabetes, chronic obstructive pulmonary disease [COPD], hypertension, HIV, or cardiac disease) and treatment regimens (e.g., medical management, pharmacotherapy, surgery), (b) to demonstrate how cognitive outcome measures can contribute to an understanding of the value of certain treatments, and (c) to identify critical conceptual and methodological problems. The utility of this approach is incontrovertible-most large-scale medical trials have found either no adverse cognitive side effects or improved cognitive functioning following treatment. Nevertheless, before cognitive measures are routinely included in medical clinical trials, investigators will have to resolve problems that include the measurement of behavior change over time and the identification of clinically significant impairment.

Neuropsychological dysfunction after minimally invasive direct coronary artery bypass grafting

BACKGROUND

We compared postoperative neuropsychological dysfunction after minimally invasive direct coronary artery bypass grafting (MIDCAB) operation with coronary artery bypass graft operations using cardiopulmonary bypass.

METHODS

Neuropsychological assessment was performed preoperatively and before discharge on 7 patients undergoing MIDCAB procedures, 9 patients undergoing single-graft cardiopulmonary bypass operation, and 27 patients undergoing multiple-graft cardiopulmonary bypass operation. From a matched control group of 40 normal subjects reliable change indices were derived for each measure and used to determine the incidence of postoperative decline.

RESULTS

There was little difference between the MIDCAB and single-graft cardiopulmonary bypass groups on the incidence of neuropsychologic decline. However, the multiple-graft cardiopulmonary bypass group had a significantly higher incidence of decline than the MIDCAB and single-graft cardiopulmonary bypass groups on specific neuropsychologic measures, coupled with a significantly greater number of postoperative deteriorations per patient.

CONCLUSIONS

The elimination of cardiopulmonary bypass does not prevent neuropsychological dysfunction after cardiac operation as patients undergoing MIDCAB and single-graft cardiopulmonary bypass experience similar deteriorations in performance. However, the deterioration is markedly worsened when the number of surgical grafts is increased.

Microemboli in cerebral circulation and alteration of cognitive abilities in patients with mechanical prosthetic heart valves

BACKGROUND AND PURPOSE

It has been shown previously that cerebral microemboli may occur frequently in patients with a normal mechanical heart valve (MHV) without prior history of stroke. Some arguments strongly suggest that these microemboli have a gaseous origin. In other circumstances such as extracorporeal circulation or decompression in divers, it has been demonstrated that cerebral microbubbles could lead to some deterioration in cognitive functions. Therefore, we have studied attention and memory, which are among the most impaired cognitive functions as demonstrated in previous studies, in patients with an MHV.

METHODS

Three groups of 12 volunteers each were composed of patients with an MHV and embolic signals in the cerebral circulation (group 1), patients with biological prostheses (group 2), and healthy subjects (group 3). Groups were carefully matched for age and verbal intellectual abilities. For each group, a transcranial Doppler examination was performed and a set of cognitive tests assessing sustained and selective attention and episodic and working memory was administered.

RESULTS

The mean embolic rate was 29 per hour in patients with an MHV. No embolus was detected in the other 2 groups. Episodic memory was significantly modified in both groups 1 and 2 compared with the control group for tasks that required high-processing resources. Working memory performance was significantly decreased in MHV patients. No between-groups differences were observed for the other parameters.

CONCLUSIONS

Alteration of episodic memory can be attributed to a long-term effect of the surgical procedure. Deterioration of working memory can be related to the presence of cerebral microemboli in MHV patients.

Alterations of neuropsychological function and cerebral glucose metabolism after cardiac surgery are not related only to intraoperative microembolic events

BACKGROUND AND PURPOSE

High-intensity transient signals (HITS) during cardiac surgery are capable of causing encephalopathy and cognitive deficits. This study was undertaken to determine whether intraoperative HITS cause alterations of neuropsychological function (NPF) and/or cerebral glucose metabolism (CMRGlc), even in a low-risk patient group, and whether induced changes are interrelated.

METHODS

Eighteen patients without signs of cerebrovascular disease underwent elective coronary artery bypass grafting (CABG), and two of these additionally underwent valve replacement in normothermia. Intraoperatively, HITS were recorded by means of transcranial Doppler ultrasonography (TCD). Perioperatively, NPF and CMRGlc were assessed using a standardized complex test battery and positron emission tomography with 18F-2-fluoro-2-deoxy-D-glucose (FDG-PET), respectively.

RESULTS

Intraoperatively, the number of HITS ranged from 90 to 1710 per patient and hemisphere, more on the right side than on the left (P<.05). HITS occurred primarily during cardiopulmonary bypass (71.3%) and, to a lesser extent, during aortic manipulation (22.2%). Changes in global and regional CMRGlc between first (one day preoperatively) and second (8 to 12 days postoperatively) FDG-PET scans were mild. No correlations were found between the number of HITS, age of patient, duration of cardiac ischemia or cardiopulmonary bypass and the changes in CMRGlc. In patients with recorded HITS and a postoperative decrease of regional CMRGlc (n=11), the maximal decrease of rCMR Glc in each hemisphere below the individual global change of CMRGlc correlated with the number of HITS (r= -0.46, P<.05). Limitations in NPF occurred 8 to 12 days postoperatively, resolved within 3 months, and were not found to be correlated to the absolute number of HITS or changes in CMRGlc.

CONCLUSIONS

HITS during cardiac surgery can cause alterations of both NPF and CMRGlc, even in a low-risk patient group. However, the number of HITS and changes in NPF and CMRGlc are not necessarily interrelated, which indicates that (1) the location of brain damage related to HITS is more important for the development of NPF than is the absolute number of HITS, and (2) factors in addition to HITS might contribute to surgery-related brain damage.

Can cerebrovascular microemboli induce cognitive impairment in patients with prosthetic heart valves?

Doppler ultrasonography can be used to detect the presence of emboli in the cerebral arterial circulation. Emboli can be produced by different sources and can be of different nature: solid elements as thrombi, platelet aggregates or atheromatous material, or gaseous when they are produced during the decompression phase of diving or during extracorporeal circulation (ECC) procedures. A more recent source of emboli has been found in the mechanical prostheic heart valves (MHV). The emboli generated by MHV are likely of gaseous nature and are found in the middle cerebral artery blood flow at a variable rate, where they are detected by transcranial Doppler sonography. The mechanism of production of these microbubbles may be related to the rapid leaflet motion especially at closure when very high local pressure gradients appear, which may be able to provoke a release of the disolved blood gas. Solid element emboli constitute a major cause of cerebrovascular disease and particularly stroke. Conversely, gaseous emboli coming from ECC or MHV are considered as clinically silent. Nevertheless, cognitive alterations have been reported after ECC. As the MHV carriers are chronically submitted to embolic events, it can be assumed that cognitive impairments may occur also in these patients. A preliminary study was designed to inpatients attention and memory in patients with normally functioning MHV and microemboli, with biological prosthesis and in normal subjects. In the two groups of patients, episodic memory was significantly altered relatively to the control group. In the MHV carriers group, a significant decrease in working memory performance was observed relatively to the two other groups. These results confirm a long term effect of the microembolization occuring during ECC and point out the effect of the chronic exposition to microemboli.

Assessment of cognitive deterioration in individual patients following cardiac surgery: correcting for measurement error and practice effects

Assessment of cognitive change in individual patients may be confounded by unreliability of test scores and effects of repeated testing. An index correcting for both problems is proposed and compared with change indices that do not or do not adequately deal with measurement error and practice effects. These indices were used to examine cognitive deterioration in a sample of 63 patients undergoing cardiac surgery. It was demonstrated that for test measures with a low reliability, failure to correct for measurement error resulted in overestimation of deterioration rates. For test measures with a high reliability, but showing substantial practice effects, failure to correct for practice effects resulted in underestimation of deterioration rates. With the proposed index, cognitive deterioration shortly after cardiac surgery was most frequently observed for attention and psychomotor speed, less frequently for verbal fluency, and only occasionally for learning and memory.

Safe and effective method of stabilization for coronary artery bypass grafting on the beating heart

BACKGROUND

There is an emerging interest in performing coronary artery bypass grafting on the beating heart. This study examines the efficacy and safety of two types of coronary artery stabilizers developed to perform coronary artery bypass grafting on the beating heart.

METHODS

Four dogs underwent left internal mammary artery to left anterior descending artery anastomosis using a retractor-fixed stabilizer. Measurements of hemodynamic indices and range of motion of the targeted arteriotomy were done before and after application of the stabilizers. Patency of the anastomosis was evaluated by angiography. To clinically validate the safety of this stabilizer, we collected data on 150 patients from centers that had access to the retractor-fixed stabilizer.

RESULTS

All animals survived the procedure with no ischemic changes or hemodynamic alterations. A significant reduction in range of motion (mm) of the left anterior descending coronary artery was achieved after application of the stabilizers. Angiographic studies showed good anastomotic patency. Histologic examination showed no myocardial injury. Patient data revealed successful completion of the anastomosis, with conversion to sternotomy or cardiopulmonary bypass in 1 patient each. Intraoperative and postoperative myocardial infarctions occurred in 1 patient each, with one in-hospital death.

CONCLUSIONS

Significant stabilization of targeted coronary arteries allowing the performance of safe and reliable anastomosis on a beating heart can be achieved using the stabilizer.

Neuropsychologic change after cardiac surgery: a critical review

Studies that have examined neuropsychologic change after cardiac surgery address three main issues: (1) the incidence of cognitive change; (2) the identification of factors that put patients at higher risk; and (3) the evaluation of interventions to prevent these complications. This review attempts to bring together concerns associated with various study designs and to integrate the conclusions from these studies. Thirty-five studies have been examined in this review. Some of the difficulties encountered when quantifying the degree of cognitive change are related to study design, patient sampling, and deficit definition. Additionally, changing patient populations have influenced results reported from different health care settings. Increasing age and longer cardiopulmonary bypass times have been correlated with cognitive decline in a number of studies. Filtration devices and blood gas management techniques have decreased but not eliminated the number of patients who have cognitive decline. Cognitive change exists following cardiac procedures. Identification of a subgroup of patients at high risk for cognitive change has been difficult, possibly due to issues of study design. Design of future studies, which may include intraoperative or pharmacologic interventions, is dependent on identification of this high-risk group.