Central Nervous System Complications in Coronary Artery Bypass Graft Surgery

Photobiomodulation for Global Cerebral Ischemia: Targeting Mitochondrial Dynamics and Functions

Hypothermia is currently the only approved therapy for global cerebral ischemia (GCI) after cardiac arrest; however, it unfortunately has multiple adverse effects. As a noninvasive procedure, photobiomodulation (PBM) therapy has emerged as a potential novel treatment for brain injury. PBM involves the use of low-level laser light therapy to influence cell behavior. In this study, we evaluated the therapeutic effects of PBM treatment with an 808-nm diode laser initiated 6 h after GCI. It was noted that PBM dose-dependently protected against GCI-induced neuronal death in the vulnerable hippocampal CA1 subregion. Functional assessments demonstrated that PBM markedly preserved both short-term (a week) and long-term (6 months) spatial learning and memory function following GCI. Further mechanistic studies revealed that PBM post-treatment (a) preserved healthy mitochondrial dynamics and suppressed substantial mitochondrial fragmentation of CA1 neurons, by reducing the detrimental Drp1 GTPase activity and its interactions with adaptor proteins Mff and Fis1 and by balancing mitochondrial targeting fission and fusion protein levels; (b) reduced mitochondrial oxidative damage and excessive mitophagy and restored mitochondrial overall health status and preserved mitochondrial function; and (c) suppressed mitochondria-dependent apoptosome formation/caspase-3/9 apoptosis-processing activities. Additionally, we validated, in an in vitro ischemia model, that cytochrome c oxidase served as a key PBM target for mitochondrial function preservation and neuroprotection. Our findings suggest that PBM serves as a promising therapeutic strategy for the functional recovery after GCI, with mechanisms involving PBM's preservation on mitochondrial dynamics and functions and the inhibition of delayed apoptotic neuronal death in GCI.

Prosurvival NMDA 2A receptor signaling mediates postconditioning neuroprotection in the hippocampus

Ischemic postconditioning (Post C), which involves administration of a brief ischemia after the initial ischemic event, has been demonstrated to be strongly neuroprotective against global cerebral ischemia (GCI) and to improve cognitive outcome. To enhance understanding of the underlying mechanisms, the current study examined the role of NMDA receptors in mediating the beneficial effects of Post C (3 min ischemia) administered 2 days after GCI in adult male rats. The results revealed that Post C was strongly neuroprotective against GCI, and that this effect was blocked by administration of the NMDA receptor antagonist MK-801. Further work revealed that the NR2A-type NMDA receptors mediate the Post C beneficial effects as administration of a NR2A-preferring antagonist (NVP-A) blocked Post C neuroprotection and cognitive enhancement, while administration of a NR2B-preferring antagonist (Ro25) was without effect. Post C significantly up-regulated NR2A levels and phosphorylation of NR2A in the hippocampal CA1 region after Post C. Post C also increased Ca(2+) influx and activation/phosphorylation of CamKIIα at Thr(286), effects that were NR2A mediated as they were blocked by NVP-A. Phosphorylation of ERK and CREB was also increased by Post C, as were two downstream CREB-dependent prosurvival factors, brain derived neurotropic factor (BDNF) and Bcl2, effects that were blocked by the NR2A antagonist, NVP-A. Taken as a whole, the current study provides evidence that NR2A-activation and downstream prosurvival signaling is a critical mediator of Post C-induced neuroprotection and cognitive enhancement following GCI.

Genistein attenuates ischemic oxidative damage and behavioral deficits via eNOS/Nrf2/HO-1 signaling

Global cerebral ischemia, such as occurs following cardiac arrest, can lead to oxidative stress, hippocampal neuronal cell death, and cognitive defects. The current study examined the potential beneficial effect and underlying mechanisms of post-treatment with the naturally occurring isoflavonic phytoestrogen, genistein, which has been implicated to attenuate oxidative stress. Genistein (1 mg kg(-1)) was administered i.v. 5 min after reperfusion in rats subjected to four-vessel global cerebral ischemia (GCI). The results revealed that genistein exerted significant neuroprotection of hippocampal CA1 neurons following GCI, as evidenced by an increase in NeuN-positive neurons and the decrease in TUNEL-positive neurons. Furthermore, genistein treatment also resulted in significantly improved spatial learning and memory as compared to vehicle control animals. The beneficial effects of genistein appear to be mediated by an increase of phosphorylation/activation of eNOS, with subsequent activation of the antioxidant/detoxification Nrf2/Keap1 transcription system. Along these lines, genistein increased keap1 S-nitrosylation, with a corresponding nuclear accumulation and enhanced DNA binding activity of Nrf2. Genistein also enhanced levels of the Nrf2 downstream antioxidant protein, heme oxygenase (HO)-1, as compared to vehicle control groups. In accordance with its induction of Nrf2 activation, genistein exerted a robust attenuation of oxidative DNA damage and lipid peroxidative damage in hippocampal CA1 neurons after GCI, as measured by immunofluorescence staining of the oxidative stress markers, 8-hydroxy-2-deoxyguanosine (8-OHdG) and 4-Hydroxynonenal (4-HNE). Interestingly, the aforementioned effects of genistein were abolished by pretreatment with L-NAME, an inhibitor of eNOS activation. In conclusion, the results of the study demonstrate that low dose genistein can exert significant antioxidant, neuroprotective, and cognitive-enhancing effects in the hippocampal CA1 region following GCI. Mechanistically, the beneficial effects of genistein appear to be mediated by enhanced eNOS phosphorylation/activation and nitric oxide (NO)-mediated thiol modification of Keap1, with subsequent upregulation of the Nrf2/HO-1 antioxidative signaling pathway and a resultant attenuation of oxidative stress.

Is Alzheimer's disease a neurodegenerative or a vascular disorder? Data, dogma, and dialectics

The cause of Alzheimer's disease (AD) is unknown. This gap in knowledge has created a stumbling block in the search for a genuinely effective treatment or cure for this dementia. This article summarises the arguments for a causal role for either amyloid deposition or cerebrovascular pathology as the primary trigger in the development of non-genetic AD. A bare-bones survey of the published research reveals no compelling evidence that amyloid deposition is neurotoxic in human beings or that it results in neurodegenerative changes involving synaptic, metabolic, or neuronal loss in human or transgenic-mouse brains. By contrast, the data supporting AD as a primary vascular disorder are more convincing. Findings suggesting a vascular cause of AD come from epidemiological, neuroimaging, pathological, pharmacotherapeutic, and clinical studies. The consensus of these studies indicates that chronic brain hypoperfusion is linked to AD risk factors, AD preclinical detection and pharmacotherapeutic action of AD symptoms.

Rehabilitation of postcardiac surgery stroke patients. Progress, outcomes, and comparisons with other stroke patients

OBJECTIVE

To examine the demographics, progress, and functional outcomes of all postcardiac surgery stroke patients admitted to the rehabilitation unit of an acute, tertiary general hospital over a 5-yr period and to compare this cohort with an age-matched control group of other stroke patients admitted during the same period.

DESIGN

A retrospective chart review of 47 postcardiac surgery stroke and a matched control group of other stroke patients admitted to the rehabilitation unit.

RESULTS

The mean age of the postcardiac surgery stroke patients was 70.80 +/- 8.37 yr, with 60% of patients being male. Their average length of stay on the rehabilitation unit was 15.64 +/- 11.96 days. Mean admit FIM total score was 65.64 +/- 16.33, with a discharge FIM total score of 86.77 +/- 18.93. Mean admit FIM motor score was 41.47 +/- 9.45, with a discharge FIM motor of 60.74 +/- 13.20. The other stroke group had significantly greater admit FIM total (P = 0.03), admit motor (P = 0.001), and discharge motor (P = 0.025) scores. FIM efficiency and motor and cognitive gains were comparable between the two groups. Length of stay on the rehabilitation unit was approximately 2 days less (P = 0.224) for the other stroke cohort. Ultimately, 39 (83%) of the postcardiac surgery stroke patients were discharged to the community compared with 45 (96%) of the other stroke patients (P = 0.19).

CONCLUSIONS

The majority of postcardiac surgery stroke patients successfully completed a comprehensive inpatient rehabilitation program. They had lower admit FIM total scores and admit and discharge FIM motor scores than the other stroke group and were almost as likely to ultimately return to the community.

Alzheimer disease as a vascular disorder: nosological evidence

BACKGROUND

The main stumbling block in the clinical management and in the search for a cure of Alzheimer disease (AD) is that the cause of this disorder has remained uncertain until now.

SUMMARY OF REVIEW

Evidence that sporadic (nongenetic) AD is primarily a vascular rather than a neurodegenerative disorder is reviewed. This conclusion is based on the following evidence: (1) epidemiological studies showing that practically all risk factors for AD reported thus far have a vascular component that reduces cerebral perfusion; (2) risk factor association between AD and vascular dementia (VaD); (3) improvement of cerebral perfusion obtained from most pharmacotherapy used to reduce the symptoms or progression of AD; (4) detection of regional cerebral hypoperfusion with the use of neuroimaging techniques to preclinically identify AD candidates; (5) presence of regional brain microvascular abnormalities before cognitive and neurodegenerative changes; (6) common overlap of clinical AD and VaD cognitive symptoms; (7) similarity of cerebrovascular lesions present in most AD and VaD patients; (8) presence of cerebral hypoperfusion preceding hypometabolism, cognitive decline, and neurodegeneration in AD; and (9) confirmation of the heterogeneous and multifactorial nature of AD, likely resulting from the diverse presence of vascular risk factors or indicators of vascular disease.

CONCLUSIONS

Since the value of scientific evidence generally revolves around probability and chance, it is concluded that the data presented here pose a powerful argument in support of the proposal that AD should be classified as a vascular disorder. According to elementary statistics, the probability or chance that all these findings are due to an indirect pathological effect or to coincidental circumstances related to the disease process of AD seems highly unlikely. The collective data presented in this review strongly support the concept that sporadic AD is a vascular disorder. It is recommended that current clinical management of patients, treatment targets, research designs, and disease prevention efforts need to be critically reassessed and placed in perspective in light of these important findings.

Ischemic preconditioning acts upstream of GluR2 down-regulation to afford neuroprotection in the hippocampal CA1

Animals subjected to sublethal transient global ischemia (ischemic preconditioning) exhibit neuroprotection against subsequent global ischemia-induced neuronal death in the hippocampal CA1 (ischemic tolerance). The molecular mechanisms underlying ischemic tolerance are unclear. Here we report that ischemic preconditioning induced a small, transient down-regulation of GluR2 mRNA expression and greatly attenuated subsequent ischemia-induced GluR2 mRNA and protein down-regulation and neuronal death. Ischemic preconditioning and GluR2 antisense knockdown acted synergistically to increase cell death. Sublethal antisense knockdown did not protect against subsequent ischemic insults or antisense knockdown. These findings indicate that ischemic preconditioning acts at step(s) upstream from suppression of GluR2 gene expression to afford neuroprotection and implicate transcriptional regulation of GluR2 expression in the adaptive mechanisms associated with ischemic tolerance.

The AMPAR subunit GluR2: still front and center-stage

Abnormal influx of Ca(2+) through AMPA-type glutamate receptors (AMPARs) is thought to contribute to the neuronal death associated with a number of brain disorders. AMPARs exist as both Ca(2+)-impermeable and Ca(2+)-permeable channels. AMPARs are encoded by four genes designated GluR1 (GluR-A) through GluR4 (GluR-D). The presence of the GluR2 subunit renders heteromeric AMPA receptor assemblies Ca(2+)-impermeable. Molecular diversity of AMPARs under physiological and pathological conditions is generated by differential spatio-temporal patterns of GluR expression, by alternative RNA splicing and editing and by targeting and trafficking of receptor subunits at dendritic spines. The GluR2 gene is under transcriptional control by the RE1 element specific transcription factor, a gene silencing factor which renders it neuron-specific. GluR2 transcripts are edited by ADAR2 (double-stranded RNA-specific editase 1). AMPAR targeting and trafficking to spines are regulated by synaptic activity and are critical to synaptic plasticity. Recent studies involving animal models of transient forebrain ischemia and epilepsy show that GluR2 mRNA and GluR2 subunit expression are downregulated in vulnerable neurons prior to cell death. Ca(2+) imaging and electrical recording from individual pyramidal neurons in hippocampal slices reveal changes in AMPAR functional properties after ischemia. In slices from post-ischemia animals, CA1 neurons with robust action potentials exhibit greatly enhanced AMPA-elicited rises in intracellular Ca(2+). Excitatory postsynaptic currents in post-ischemic CA1 exhibit an enhanced Ca(2+)-dependent component that appears to be mediated by Ca(2+)-permeable AMPARs. These studies provide evidence for Ca(2+) influx through AMPARs in neurons destined to die. To examine whether acute GluR2 downregulation, even in the absence of a neurological insult, can induce neuronal death, we performed knockdown experiments in rats and gerbils with antisense oligonucleotides targeted to GluR2 mRNA. GluR2 antisense oligonucleotide induced neuronal cell death of pyramidal neurons and enhanced pathogenicity of brief ischemic episodes. These observations provide evidence for Ca(2+) influx through AMPARs in neurons destined to die and implicate Ca(2+)-permeable AMPARs in the pathogenesis of ischemia-induced neuronal death.

Strategy for reduction of stroke incidence in coronary bypass patients with cerebral lesions. Early results and mid-term morbidity using pulsatile perfusion

OBJECTIVES

Cerebral complication is an important factor affecting the outcome after coronary artery bypass surgery under cardiopulmonary bypass. One of the causes for cerebral complication is preoperative cerebrovascular stenotic lesion. Here, we have studied the effect of pulsatile perfusion on the rate of cerebral complication due to a cerebrovascular lesion in patients undergoing coronary arterial bypass graft under cardiopulmonary bypass.

METHODS

261 consecutive elective patients underwent operation using cardiopulmonary bypass for management of the atherosclerotic ascending aorta. Group 1 consisted of 62 patients with a cerebrovascular stenotic lesion (> or = 75%) identified on a magnetic resonance angiogram or multiple cerebral infarction diagnosed using a computer tomogram. Group 2 consisted of 199 patients diagnosed with no significant cerebral lesion. In Group 1, the systolic blood pressure during cardiopulmonary bypass was maintained at a level of 80 mmHg by means of pulsatile flow. In Group 2, non-pulsatile perfusion was used as usual.

RESULTS

The overall hospital mortality was 1.5%, and no mortality was caused by a cerebral event. Only one patient in Group 1 suffered from temporary hemiparalysis. A cerebral complication occurred in only 1.6% in Group 1, and 0.4% overall. The actuarial freedom from cerebrovascular accident after 54 months was 84.4% in Group 1, and 96.2% in Group 2 (p = 0.0011).

CONCLUSIONS

Management of the atherosclerotic ascending aorta and the use of pulsatile perfusion were helpful in preventing cerebral injury during CABG.

Intra- and postoperative factors determining neurological complications after surgery under deep hypothermic circulatory arrest: a retrospective somatosensory evoked potential study

OBJECTIVES

Intraoperative median nerve SEP monitoring uses the disappearance of cortical and brain stem activities as the criterion to determine that brain cooling is sufficient in deep hypothermic circulatory arrest (CA) surgery. This study presents the results of a retrospective SEP analysis of intraoperative events that engendered neurological complications.

METHODS

Median nerve SEP monitoring was performed on 58 consecutive patients who underwent surgery under deep hypothermic CA. The monitoring was retrospectively analyzed and compared with intraoperative events, and postoperative symptoms.

RESULTS

Intraoperative SEP abnormalities were observed in 9 out of the 16 patients who presented neurological complications. Among the 7 others, the abnormalities either were present preoperatively (n = 2), occurred postoperatively (n = 3) or only involved the lower limbs (n = 2). Although the mere inspection of the intraoperative SEPs was insufficient to determine the origin of the alterations, their comparison with intraoperative events facilitated the identification of hemodynamic factors in 7 cases and embolism in two cases. There were no patients in whom CA per se caused neurological complications.

CONCLUSIONS

Intraoperative SEP monitoring helps identify intraoperative events responsible for neurological complications and prevent these in subsequent procedures. However, the neurological complications of deep hypothermic CA can also be due to pre- or postoperative factors that escape the domain of intraoperative monitoring.

[The involvement of the brachial plexus in cardiac surgery with median sternotomy for the revascularization of the myocardium: clinical evaluation]

To evaluate the involvement of brachial plexus in cardiac surgery with median sternotomy for the revascularization of the myocardium 113 patients (87 men and 26 women) were clinically examined in the preoperative and between the fifth and eight post-operative days. The internal thoracic artery was used in 65 of the 113 patients. The electroneuromyography was not effected in any of the patients. A lesion of the brachial plexus was found in three patients though the internal thoracic artery was used in only one patient. We believe that factors such as posture of the patient, hypothermia, thoracic braces and use of the internal thoracic artery are relevant in the lesions. Hence one must be attentive to all the factors mentioned above so as to avoid or minimize the lesions.

Retrospective study of somatosensory evoked potential monitoring in deep hypothermic circulatory arrest

BACKGROUND

We evaluated the efficiency of median-nerve somatosensory evoked potentials (SEPs) monitoring in determining the optimal level of hypothermia in 62 consecutive patients operated on under deep hypothermic circulatory arrest (CA).

METHODS

CA was started at 1 degree C below the temperature at which both brainstem and cortical SEP components disappear. No additional method of cerebral protection was used.

RESULTS

New neurological complications were observed in 15 patients: long-lasting in 11 and transient in 4. A retrospective analysis of SEP monitoring identified the origin of the complications in 12 cases: early CA with incomplete cooling due to emergency (3 cases); inefficient retrograde perfusion through the femoral artery during cooling due to the dissection flap effect (4 cases); embolism during rewarming (2 cases); delayed embolism (2 cases); hemorrhagic shock (1 case). In 2 cases, neurological sequelae involved the lower limbs (extracerebral origin). One case without intraoperative SEP changes was neurologically abnormal preoperatively and did not change postoperatively. There were no cases with sequelae due to excessive CA duration.

CONCLUSIONS

The use of SEP monitoring to determine the optimal level of hypothermia efficiently prevents neurological sequelae of CA. It helps in monitoring the degree of cerebral protection during cooling (flap effect), and rewarming.

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.

[Sensitivity, specificity, and impact on the surgical strategy of the perioperative neuromonitoring of somatic evoked potentials in vascular surgery performed with circulatory arrest under deep hypothermia]

AIM

Median nerve somatosensory evoked potentials (SEP) monitoring performed in deep hypothermic circulatory arrest is useful in determining when brain cooling may sufficiently permit circulatory arrest, and to immediately indicate when brain injury occurs. The aim of this retrospective study, including 58 patients, is to determine SEP sensitivity, specificity and impact on the surgical strategy.

METHOD

Sensitivity was determined on patients presenting new neurological complications. Specificity was measured on the patients without any new neurological defect. The impact of intraoperative SEP on the surgical strategy was determined when the occurrence of SEP alterations had provoked a modification of the surgical procedure.

RESULTS

Five patients died intraoperatively due to non-neurological complications. Fourteen patients presented new neurological complications. SEP sensitivity reaches 64.3% when all the complications are included, but increases to 100% in our series if late postoperative complications, paraplegia and tibial posterior nerve lesion are excluded because median nerve SEP are not able to detect such complications. SEP monitoring was uneventful in the 39 patients whose did not present neurological complication: thus SEP specificity is absolute in our series. SEP had an impact on the surgical procedure whenever neurological complications due to hemodynamic disturbances occurred.

CONCLUSION

This retrospective study shows the interest of intraoperative SEP as an useful tool for promptly identifying and preventing the neurological complication of hypothermic circulatory arrest.

Rehabilitation of the post-cardiac surgery stroke patient: analysis of cognitive and functional assessment

OBJECTIVE

Determine whether, as expected, patients sustaining post-cardiac surgery stroke (PCS) (n = 19) differ from other stroke (OS) patients (n = 216).

DESIGN

A total of 235 stroke patients were surveyed. Therapist ratings of Functional Independence Measure (FIM) on admission to and discharge from a rehabilitation unit were compared. Cooperation with formal neuropsychologic evaluation was assessed.

SETTING

The rehabilitation unit of a tertiary care hospital.

PARTICIPANTS

Medical records for consecutive stroke patients were reviewed (January 1994 to December 1995). Groups did not differ in age, gender, or admission FIM.

INTERVENTIONS

Standardized neuropsychologic evaluation of seven cognitive domains was attempted for each patient referred to the neuropsychology service. All of the patients received FIM ratings on admission to and discharge from the rehabilitation unit.

OUTCOME MEASURES

Gain in FIM per week of rehabilitation unit stay (FIM efficiency) and discharge destination.

RESULTS

Contrary to expectations, PCS patients did not differ significantly from OS patients in FIM efficiency or discharge destination. However, PCS patients were significantly less able to cooperate with formal neuropsychologic testing, possibly secondary to their physical condition, higher-level cognitive deficits, or both.

CONCLUSION

Although PCS patients may sustain medical and cognitive deficits that interfere with exhaustive neuropsychologic evaluation, these deficits do not significantly interfere with functional progress in rehabilitation and should not make PCS patients ineligible for rehabilitation services.

Adenosine kinase inhibition protects brain against transient focal ischemia in rats

Endogenous adenosine released locally during cerebral ischemia is neuroprotective, and agents which decrease adenosine inactivation may potentiate its protective effects. The effects of 5'-deoxy-5-iodotubercidin (5'd-5IT), an inhibitor of the adenosine-catabolizing enzyme, adenosine kinase, were studied in male Wistar rats subjected to 2 h of transient middle cerebral artery occlusion. 5'd-5IT or the vehicle (10% DMSO in saline) was administered i.p. 30 min before, and 2 h and 6 h after the induction of middle cerebral artery occlusion. The infarct volume was determine using 2,3,5-triphenyltetrazolium chloride staining 48 h after middle cerebral artery occlusion. The infarct volume was significantly reduced in rats treated with 1.85 mg/kg x 3 (57% reduction, P < 0.001) or 1.0 mg/kg x 3 (34% reduction, P < 0.05), but not 0.3 mg/kg x 3 5'd-5IT compared to vehicle-treated rats. The reduction of infarct volume was accompanied by a significant improvement in behavioral measures of neurological deficit. These data further support a role of adenosine in neuroprotection and suggest that adenosine kinase inhibition may be a useful approach to the treatment of focal cerebral ischemia.

Predictors of stroke risk in coronary artery bypass patients

BACKGROUND

Stroke occurs after coronary artery bypass grafting with an incidence ranging between 0.8% and 5.2%. To identify factors associated with stroke, we prospectively examined a study cohort and tested findings in an independent validation sample.

METHODS

The study cohort comprised 456 patients undergoing coronary artery bypass grafting only, and the validation sample comprised 1,298 patients. Stroke was detected postoperatively by the study team and confirmed by neurologic consultation and computed tomographic scanning.

RESULTS

Five factors taken together were correlated with stroke: previous stroke, presence of carotid bruit, history of hypertension, increasing age, and history of diabetes mellitus. The only significant intraoperative factor was cardiopulmonary bypass time. Probabilities were calculated, and patients were placed into low, medium, and high stroke-risk groups. In the validation sample, this model was able to rank the majority of patients with stroke into the high-risk group.

CONCLUSIONS

These five factors taken together can identify the risk of stroke in patients having coronary artery bypass grafting. Recognition of the high-risk group will aid studies on the mechanism and prevention of stroke by modification of surgical procedures or pharmacologic intervention.

Delirium and cognitive disorders after cardiac operations: relationship to pre- and intraoperative quantitative electroencephalogram

We examined the incidence of delirium and cognitive disorders after cardiac operations and the related risk factors. The value of pre- and intraoperative QEEG was determined. Using the Mini-Mental State Examination and the Saskatoon Delirium Checklist, 321 patients were tested during the immediate postoperative period. Forty-four patients (14%) showed delirium, 68 (23%) cognitive disorders and 26 (9%) both. Significant risk factors for the development of cognitive disorders were age > or = 70 yr, female gender, duration of cardiopulmonary bypass > or = 2.5 h and aorta-cross-clamping > 70 min. Risk factors for delirium were age > or = 70 yr, female gender and Hb < 5 mmol 1(-1) intraoperatively. The preoperative QEEG showed significant differences between the groups with and without a cognitive disorder, while the intraoperative QEEG showed significant differences between the groups with and without delirium. Different risk factors for delirium and cognitive disorders are a possible explanation for the controversies in the literature, where neuropsychologic complications were grouped together. A low intraoperative Hb is an important risk factor for the development of delirium and can be treated. The preoperative QEEG may have prognostic significance in the occurrence of cognitive disorders, while the intraoperative QEEG may have prognostic significance in the occurrence of delirium.

Aortic atheromatosis and risks of cerebral embolization

With the advent of transesophageal echocardiography, aortic atheromatosis has emerged as an important source of cerebral embolization. Mobile atheromatous plaque in the ascending aorta and aortic arch has been shown to constitute a strong and independent risk factor in patients with stroke. In patients undergoing coronary bypass surgery, it is the single most important contributing factor to perioperative neurologic morbidity. Emboli originating in the heart, aorta, and proximal cerebral vasculature have been observed intraoperatively in patients undergoing coronary bypass surgery, especially when aortic clamps are released. The constitution of these emboli is unclear, although an indeterminate fraction undoubtedly represents dislodged atheromatous material. The impact of such embolization in terms of neurologic outcome is currently under investigation. Prevention of embolization from mobile aortic atheroma in patients undergoing cardiac surgery may require modification of surgical technique. Secondary prevention in patients with a history of embolization can only be determined once the natural history of such lesions is established.

Predictors of stroke after cardiac surgery

From January 1, 1988 to September 30, 1993, 44 of 2,455 patients undergoing cardiac surgery for acquired heart disease at our institution sustained an intraoperative or postoperative cerebrovascular accident (CVA). Demographic data, atherosclerosis risk factors, past medical history, cardiac catheterization reports, and intraoperative findings were retrospectively reviewed. The highest rate of CVA was in the sub-group of patients undergoing simultaneous myocardial revascularization and carotid endarterectomy (18.2%). The lowest rate was in a group of patients who underwent aortic valve replacement (0.9%). Severe aortic arch atherosclerosis with the presence of atheromatous material or calcinosis at the cannulation site was identified intraoperatively in 43.2% of patients with neurological complications and in 5% of the group without CVA (x2 = 18.1, p = 0.0001). Of 44 patients with CVA, 13.6% had a history of preoperative completed stroke. CPB time was 90.1 +/- 4.9 min vs. 71.6 +/- 3.7 min (p = 0.004), and aortic cross-clamping time was 54.5 +/- 3.2 min compared to 39.8 +/- 2.7 min (p = 0.001) in groups with and without postoperative stroke, respectively. Hypertension was an independent risk factor of postoperative CVA (x2 = 9.5, p = 0.02), but age was not. Neurological complications correlated with high operative mortality (38.6%) and prolonged postoperative hospital stays (35.1 +/- 5.3). These data describe predictors for the development of post-cardiopulmonary bypass CVA and identify a high-risk subgroup for neurological events. The preoperative recognition of risk factors is an essential step toward the reduction of morbidity and mortality.