Cerebral embolization during cardiac surgery: impact of aortic atheroma burden

Postoperative Brain Attack: Current Perspectives and Future Directions

The incidence of stroke after cardiac surgery poses significant challenges. This expert review piece explores current knowledge, challenges, future directions, and offers insights into improving patient outcomes through optimal prevention, early recognition, and management strategies. By addressing the challenges and opportunities in this area, we can enhance patient care, reduce long-term disabilities, and improve the overall quality of life for affected individuals. This expert review aims to provide a comprehensive framework for managing postoperative stroke: mechanisms, risk factors, diagnosis, treatment, systems of care, and ethical considerations.

Targeted temperature management in cardiac surgery: a systematic review and meta-analysis on postoperative cognitive outcomes

BACKGROUND

Postoperative cognitive decline occurs commonly after cardiac surgery. The available literature is inconclusive on the role of intraoperative causal or protective factors.

METHODS

We systematically reviewed studies evaluating delayed neurocognitive recovery (DNR), postoperative neurocognitive disorder (NCD), stroke, and the mortality rates among patients undergoing hypothermic or normothermic cardiopulmonary bypass (CPB). We further performed a subgroup analysis for age, surgery type (coronary artery bypass grafting [CABG], valve surgery, or combined), and the mean arterial blood pressure (MAP) during CPB, and conducted a proportion meta-analysis after calculation of single proportions and confidence intervals (CIs).

RESULTS

We included a total of 58 studies with 9609 patients in our analysis. Among these, 1906 of 4010 patients (47.5%) had DNR, and 2071 of 7160 (28.9%) had postoperative NCD. Ninety of 4625 patients (2.0%) had a stroke, and 174 of 7589 (2.3%) died. There was no statistically significant relationship between the considered variables and DNR, NCD, stroke, and mortality. In the subgroup analysis comparing hypothermic with normothermic CPB, we found higher NCD rates after combined surgery; for normothermic CPB cases only, the rates of DNR and NCD were lower after combined surgery compared with CABG surgery. A MAP >70 mm Hg compared with MAP=50-70 mm Hg during CPB was associated with a lower rate of DNR.

CONCLUSIONS

Temperature, MAP during cardiopulmonary bypass age, and surgery type were not associated with neurocognitive disorders, stroke, and mortality in cardiac surgery. Normothermic cardiopulmonary bypass, particularly when performed with MAP >70 mm Hg, may reduce the risk of postoperative neurocognitive decline after cardiac surgery.

PROSPERO REGISTRATION NUMBER

CRD42019140844.

EACVI recommendations on cardiovascular imaging for the detection of embolic sources: endorsed by the Canadian Society of Echocardiography

Cardioaortic embolism to the brain accounts for approximately 15-30% of ischaemic strokes and is often referred to as 'cardioembolic stroke'. One-quarter of patients have more than one cardiac source of embolism and 15% have significant cerebrovascular atherosclerosis. After a careful work-up, up to 30% of ischaemic strokes remain 'cryptogenic', recently redefined as 'embolic strokes of undetermined source'. The diagnosis of cardioembolic stroke remains difficult because a potential cardiac source of embolism does not establish the stroke mechanism. The role of cardiac imaging-transthoracic echocardiography (TTE), transoesophageal echocardiography (TOE), cardiac computed tomography (CT), and magnetic resonance imaging (MRI)-in the diagnosis of potential cardiac sources of embolism, and for therapeutic guidance, is reviewed in these recommendations. Contrast TTE/TOE is highly accurate for detecting left atrial appendage thrombosis in patients with atrial fibrillation, valvular and prosthesis vegetations and thrombosis, aortic arch atheroma, patent foramen ovale, atrial septal defect, and intracardiac tumours. Both CT and MRI are highly accurate for detecting cavity thrombosis, intracardiac tumours, and valvular prosthesis thrombosis. Thus, CT and cardiac magnetic resonance should be considered in addition to TTE and TOE in the detection of a cardiac source of embolism. We propose a diagnostic algorithm where vascular imaging and contrast TTE/TOE are considered the first-line tool in the search for a cardiac source of embolism. CT and MRI are considered as alternative and complementary tools, and their indications are described on a case-by-case approach.

Aortic calcifications on routine preoperative chest X-ray and perioperative stroke during cardiac surgery: a nested matched case-control study

OBJECTIVES

Perioperative stroke in cardiac surgery is most often embolic in origin. Preoperative chest X-ray (CXR) is routinely used amongst others to screen for relevant aortic calcification, a potential source of embolic stroke. We performed a nested matched case-control study to examine the relationship between aortic calcifications on CXR and the occurrence of embolic stroke.

METHODS

Among all consecutive patients undergoing cardiac surgery in our hospital between January 2014 and July 2017, we selected all patients with perioperative embolic stroke (cases). Controls, all patients without perioperative stroke, were matched on age, sex and type of surgery. All preoperative CXRs were scored for aortic calcifications (none, mild, severe) in the ascending aorta, arch, aortic knob and descending aorta.

RESULTS

Out of the 3038 eligible patients, 27 cases were detected and 78 controls were selected. In the stroke group, mild-to-severe calcifications were found least often in the ascending aorta [9% of patients, 95% confidence interval (CI) 1-29%] and most frequently in the aortic knob (63% of patients, 95% CI 44-78%). The distribution of aortic calcification was comparable in cases versus controls.

CONCLUSIONS

Calcification burden was comparable between the cases and their matched controls. In our study population, CXR findings on aortic calcification were not related to the risk of embolic stroke. In these patients, the correlation between findings on the preoperative CXR and the risk of stroke might, therefore, be too weak to use the CXR directly for the assessment of the safety of manipulating the ascending aorta during surgery.

In vivo comparison of the optiflow and EZ glide aortic dispersion cannulas

OBJECTIVES

Morbidity associated with coronary artery bypass grafts and embolization during aortic cannulation is strongly related to patient characteristics/comorbidities, arterial cannulation site used and the shape of arterial cannulae tips. The desired features of an arterial cannula should be to mitigate the morbid effects of these cannulas and to focus on achieving higher blood flows with lower cannula pressures (CPs).

MATERIALS AND METHODS

To evaluate the in vivo performance of two aortic dispersion flow cannulas: the Optiflow (Sorin Group, Italy) and EZ Glide (Edwards Lifesciences). They were evaluated for CPs, pump-flow rates (FRs), and plasma-free hemoglobin (Hb) over a 12-month period. Data were collected in a prospective, randomized (1:1), nonblinded, monocentric study with a cohort of 30 patients (optiflow group N = 15; EZ Glide group N = 15).

RESULTS

The optiflow cannula was found to have decreasing CPs as the pump FRs were increased (112.3 ± 10.9 vs 131.1 ± 11.4 mm Hg; P < .001). Results indicated no significant differences between groups for increases in plasma free Hb (P = .41) and total microembolic signals counts during the period of cardiac surgery (P = .63).

CONCLUSIONS

Both optiflow and EZ Glide dispersion flow arterial cannulas performed well, but the optiflow cannula demonstrated an ability to increase pump FRs with lower arterial line and CPs than the EZ Glide cannula. This implies an ability to improve peripheral perfusion while reducing cannula shear stress and the risk of endothelial damage, thereby having the potential to reduce the risk of atherosclerotic plaque dislodgement.

Epiaortic Ultrasound for Assessment of Intraluminal Atheroma; Insights from the REGROUP Trial

OBJECTIVES

To assess the use of epiaortic ultrasound in contemporary cardiac surgery, as well as its impact on surgical cannulation strategy and cerebrovascular events.

DESIGN

Epiaortic ultrasound data was prospectively collected in the Randomized Endovein Graft Prospective (REGROUP) trial (VA Cooperative Studies Program #588, ClinicalTrials.gov, NCT01850082), which randomized 1,150 coronary artery bypass graft patients between 2014 and 2017 to endoscopic or open-vein graft harvest.

SETTING

Sixteen cardiac surgery programs within the Veterans Affairs Healthcare System with expertise at performing endoscopic vein-graft harvesting.

PARTICIPANTS

Veterans Affairs patients, greater than 18 years of age, undergoing elective or urgent coronary artery bypass grafting with cardiopulmonary bypass and cardioplegic arrest with at least one planned saphenous vein graft were eligible for enrollment.

INTERVENTIONS

Epiaortic ultrasound was performed by the surgeon using a high frequency (>7 MHz) ultrasound transducer. Two-dimensional images of the ascending aorta in multiple planes were acquired before aortic cannulation and cross-clamping.

MEASUREMENTS AND MAIN RESULTS

Epiaortic ultrasound was performed in 34.1% (269 of 790) of patients in REGROUP. Among these patients, simple intraluminal atheroma was observed in 21.9% (59 269), and complex intraluminal atheroma comprised 2.2% (6 of 269). The aortic cannulation or cross-clamp strategy was modified based on these findings in 7.1% of cases (19 of 269). There was no difference in stroke between patients who underwent epiaortic ultrasound and those who did not (1.9% v 1.2% p = 0.523).

CONCLUSIONS

Despite current guidelines recommending routine use of epiaortic ultrasound (IIa/B) to reduce the risk of stroke in cardiac surgery, in this contemporary trial, use remains infrequent, with significant site-to-site variability.

Does epiaortic ultrasound screening reduce perioperative stroke in patients undergoing coronary surgery? A topical review

Although the occurrence of stroke in patients undergoing coronary artery bypass grafting (CABG) is decreasing, it remains an important concern. Therefore, it is important to identify and adopt strategies that can decrease the incidence of stroke in these patients. One of the strategies that have demonstrated the potential to decrease the rate of post-CABG stroke is an assessment of aorta for atherosclerosis before surgery and changing the surgical plan accordingly to minimize the stroke risk. This assessment can be done through palpation of the aorta, transesophageal echocardiography (TEE), and epiaortic ultrasound scanning (EAS). EAS has shown superiority over both palpation and TEE for intraoperative evaluation of aorta. However, despite the evidence demonstrating reduced stroke rates with the EAS-guided approach, EAS is not yet the standard of care procedure in patients undergoing CABG. Therefore, we have reviewed the literature for evidence that supports the routine use of EAS in patients undergoing coronary surgery and have presented solutions to overcome the barriers to its routine use.

Spatially extended versus frontal cerebral near-infrared spectroscopy during cardiac surgery: a case series identifying potential advantages

Stroke due to hypoperfusion or emboli is a devastating adverse event of cardiac surgery, but early detection and treatment could protect patients from an unfavorable postoperative course. Hypoperfusion and emboli can be detected with transcranial Doppler of the middle cerebral artery (MCA). The measured blood flow velocity correlates with cerebral oxygenation determined clinically by near-infrared spectroscopy (NIRS) of the frontal cortex. We tested the potential advantage of a spatially extended NIRS in detecting critical events in three cardiac surgery patients with a whole-head fiber holder of the FOIRE-3000 continuous-wave NIRS system. Principle components analysis was performed to differentiate between global and localized hypoperfusion or ischemic territories of the middle and anterior cerebral arteries. In one patient, we detected a critical hypoperfusion of the right MCA, which was not apparent in the frontal channels but was accompanied by intra- and postoperative neurological correlates of ischemia. We conclude that spatially extended NIRS of temporal and parietal vascular territories could improve the detection of critically low cerebral perfusion. Even in severe hemispheric stroke, NIRS of the frontal lobe may remain normal because the anterior cerebral artery can be supplied by the contralateral side directly or via the anterior communicating artery.

Intraoperative Epi-Aortic Scans Reduce Adverse Neurological Sequelae in Elderly, High Risk Patients Undergoing Coronary Artery Bypass Surgery - a Propensity Matched, Cumulative Sum Control Analysis

BACKGROUND

Adverse neurological sequelae are a major cause of morbidity and mortality after coronary artery bypass (CABG) surgery, due to manipulation of an atherosclerotic aorta. The purpose of this study is to measure the impact of intraoperative epi-aortic scanning in reducing neurologic sequelae after CABG, and the patient subgroups that are benefitted the most.

METHODS

Patients that underwent first-time CABG from July 2010 to March 2014 (n=1,989) were retrospectively reviewed and stratified by history of intraoperative epi-aortic scan (n=350) or no scan (n=1,639). Baseline characteristics, rates of adverse neurological events, and overall survival were compared among groups in both matched and unmatched cohorts and tested using Student's t-test, chi² test, or log-rank test, respectively. Multivariable analysis using logistic regression was performed to identify potential predictors for neurological sequelae. Cumulative summation plots (CUSUM) were constructed to display the number of preventable adverse neurological events per consecutive patient that underwent CABG. A p≤0.05 was considered statistically significant.

RESULTS

The use of epi-aortic scan (OR: 0.29, 95% CI: 0.09-0.99, p=0.48) was an independent predictor of adverse events. Overall rates of stroke (0.29% vs 0.55%), postoperative confusional state (1.43% vs 3.42%), or both (1.71% vs 3.72%) were lower in those scanned. CUSUM scores were higher in scanned patients, especially in those with an age above 70 years or logistic Euroscore >2.

CONCLUSIONS

Intraoperative epi-aortic scan is an effective assessment tool for atherosclerotic burden in the ascending aorta and can guide surgical strategy to decrease adverse neurological outcomes, particularly in high risk and elderly patients.

Management of the Ascending Aorta in Routine Cardiac Surgery

It is well known that subtle neurologic and neuropsychologic adverse effects are associated with cardiac surgery. Microgaseous emboli may arise from the cardiac pulmonary bypass apparatus; however, most particulate emboli arise from the ascending aorta. Atherosclerosis of the ascending aorta may effect up to 38% of cardiac surgical patients greater than 50 years of age. In addition to avoiding cardiopulmonary bypass with off-pump procedures, avoiding manipulation of the ascending aorta in any way is also associated with a reduction in embolic complications. Epiaortic scanning is the most accurate way to assess the location and severity of atheromata in the ascending aorta. Management of the atheromatous ascending aorta may include changes to cannulation options for cardiopulmonary bypass, such as femoral or axillary cannulation. Complete avoidance of the cross-clamp may be entertained. Aorta cannulae incorporate a number of filtration and deflection devices that may offer some protection to the brachiocephalic vessels. In some cases, replacement of the ascending aorta under deep hypothermic circulatory arrest is appropriate. Avoidance of the ascending aorta by using arterial revascularization as sequential or Y grafts, or placing proximal anastomoses on the subclavian arteries, may allow for complete revascularization without touching the ascending aorta. A full appreciation of the information obtained with epiaortic scanning or transesophageal echocardiography allows for decisions to be made to tailor each procedure to the patient's unique needs and circumstances for optimal outcomes.

Cognitive Dysfunction After Cardiac Surgery: Revisiting Etiology

Cognitive dysfunction remains a frequent complication of cardiac surgery. Despite many years of research, few preventive strategies and no definitive therapeutic options exist for the management of this troublesome clinical problem. This shortcoming may be secondary to an incomplete understanding of the pathophysiology and etiology of cognitive loss after cardiac surgery; a better understanding of the etiology is essential to finding new therapies. The etiology of cognitive dysfunction after cardiac surgery is multifactorial and includes cerebral microembolization, global cerebral hypoperfusion, systemic and cerebral inflammation, cerebral temperature perturbations, cerebral edema, and possible blood-brain barrier dysfunction, all superimposed on genetic differences in patients that may make them more susceptible to injury or unable to repair from injury once it has occurred. This review expands on these potential etiologies in detailing the evidence for their existence.

Applied Neuromonitoring in Cardiac Surgery: Patient Specific Management

Various studies have demonstrated that over 50% of patients presenting for coronary revascularization surgery have evidence of extracranial or intracranial atherosclerotic disease. Although evidence is compelling that cerebral emboli are a major cause of perioperative central nervous system (CNS) morbidity in such patients, it is also apparent that alterations in cerebral perfusion pressure and blood flow can profoundly influence the extent of injury after an embolic insult. In this context, the recent studies demonstrating improved CNS outcomes with applied neuromonitoring in cardiac surgical patients can be understood as reflecting the optimization of CNS perfusion characteristics with potential amelioration of microembolic injury. This review critically evaluates and discusses the relevant characteristics of applied neuromonitoring techniques, including bispectral index (BIS), transcranial Doppler (TCD), and near infrared reflectance spectroscopy (NIRS) in the context of patients undergoing cardiac surgical procedures. Recent outcomes data regarding CNS and related morbidity and the influence of neuromonitoring in these groups are evaluated.

Retrospective evaluation of the effect of carotid artery stenosis on cerebral oxygen saturation during off-pump coronary artery bypasses grafting in adult patients

Background

It is unknown whether cerebral oxygenation in patients with carotid artery stenosis (CAS) undergoing off-pump coronary artery bypass grafting (CABG) differs from that in patients without CAS. Thus, the effect of the presence of CAS ≥ 50 % on cerebral oxygenation during off-pump CABG in adult patients was evaluated retrospectively.

Methods

Eleven patients with CAS ≥ 50 % and 14 patients without CAS ≥ 50 % were enrolled. Regional cerebral tissue oxygen saturation (rSO₂) was quantified using near-infrared spectroscopy. Mean arterial pressure, cardiac index, central venous pressure (CVP), and rSO₂ at specific points were collected, and significant changes in each parameter were detected using repeated analysis of variance. Mean rSO₂ and minimum rSO₂ during anastomosis were analyzed by one-way analysis of variance. Multiple logistic regression analysis was used to estimate the odds ratio (OR) with 95 % confidence interval (CI) for cerebral desaturation (a decrease in rSO₂ ≥ 10 % from preoperative value).

Results

Two patients with CAS ≥ 50 % who received complete carotid artery stenting preoperatively were excluded from the analyses. In both patients with and without CAS, a decrease in rSO₂ and cardiac index and an increase in CVP were observed during anastomosis. Mean (SD) maximum decrease in rSO₂ from preoperative value was 9.2 (12.7) % on the left side and 8.1 (11.7) % on the right side in patients with CAS ≥ 50 %, and 13.5 (11.3) % on the left side and 16.1 (9.8) % on the right side in patients without CAS ≥ 50 % (p = 0.316). Neurological complications were not identified in both patients with and without CAS ≥ 50 %. In multiple logistic regression analysis, CAS ≥ 50 % was not associated with an increased risk of cerebral desaturation (OR 0.160, 95 % CI 0.036–0.707, p = 0.016), and rSO₂ decreased with decreasing cardiac index < 2.0 l/min/m² (OR 3.287, 95 % CI 2.218–5.076, p < 0.001).

Conclusions

CAS ≥ 50 % was not an independent risk factor of cerebral desaturation during off-pump CABG. Our results suggest that maintaining cardiac output can prevent a decrease in cerebral oxygenation in both patients with and without CAS ≥ 50 %.

Serum S-100β and NSE levels after off-pump versus on-pump coronary artery bypass graft surgery

Background

We aimed to evaluate serum levels of S-100 beta (S-100β) and neuron specific enolase (NSE) in patients with coronary heart disease (CHD) after off-pump versus on-pump coronary artery bypass graft (CABG) surgery.

Methods

The PubMed (~2013) and the Chinese Biomedical Database (CBM) (1982 ~ 2013) were searched without language restrictions. After extraction of relevant data from selected studies, meta-analyses were conducted using STATA software (Version 12.0, Stata Corporation, College Station, Texas USA). Possible sources of heterogeneity were examined through univariate and multivariate meta-regression analyses and verified by Monte Carlo Simulation.

Results

Eleven studies with a total of 411 CHD patients met the inclusion criteria. Our meta-analysis showed no significant difference in serum S-100β and NSE levels between the on-pump group and the off-pump group before surgery. In the on-pump group, there was a significant difference in serum S-100β levels of CHD patients between before and after surgery, especially within the first 24 h after surgery. Furthermore, in the on-pump group, there was a significant difference in serum NSE levels of CHD patients between before and after surgery, particularly at 0 h after surgery. In the off-pump group, there was an obvious difference in serum S-100β levels between before and after surgery, especially within 24 h after surgery. Our results also demonstrated that serum S-100β and NSE levels of CHD patients in the on-pump group were significantly higher than those of patients in the off-pump group, especially within 24 h after surgery.

Conclusions

Our findings provide empirical evidence that off-pump and on-pump CABG surgeries may increase serum S-100β and NSE levels in CHD patients, which was most prominent within 24 h after on-pump CABG surgery.

Guidelines for the primary prevention of stroke: a statement for healthcare professionals from the American Heart Association/American Stroke Association

The aim of this updated statement is to provide comprehensive and timely evidence-based recommendations on the prevention of stroke among individuals who have not previously experienced a stroke or transient ischemic attack. Evidence-based recommendations are included for the control of risk factors, interventional approaches to atherosclerotic disease of the cervicocephalic circulation, and antithrombotic treatments for preventing thrombotic and thromboembolic stroke. Further recommendations are provided for genetic and pharmacogenetic testing and for the prevention of stroke in a variety of other specific circumstances, including sickle cell disease and patent foramen ovale.

Increasing severity of aortic atherosclerosis in coronary artery bypass grafting patients evaluated by transesophageal echocardiography

Background

Atherosclerotic disease in coronary artery bypass grafting (CABG) patients is a potential contributor to complications in the perioperative periods. This study was undertaken to better define how the frequency of aortic atheromatous disease among patients coming for CABG has evolved over the last decade.

Methods

Data from elective patients coming for CABG who underwent transesophageal echocardiography (TEE) examinations following induction of anesthesia were obtained for the years 2002 and 2009. Aortas were graded according to the method of Kronzon, with the following interpretations: normal = grade I, intimal thickening = 2, atheroma of less than 5 mm = 3, atheroma of > 5 mm = 4, and any mobile atheroma = 5. The data of 124 patients who underwent comprehensive exam of the aorta by one cardiac anesthesiologist were gathered and assigned into two groups based on the year TEE was done. Student’s t-test was used for statistical analysis. A P value < 0.05 was considered significant. The data were presented as mean ± SD.

Results

There was significant difference between group 2002 (2.05 ± 1.28) and group 2009 (2.59 ± 1.11) in atheroma grade (P = 0.013).

Conclusions

Patients coming for CABG in group 2009 exhibited significantly higher grades of aortic atheroma on TEE, compared to group 2002. Understanding the risk of atheroma in the elderly CABG population may help in altering surgical approaches to lessen the risk of catastrophic stroke. Potential options needing further study include the off-pump approach and modification of cross-clamp site and technique as well as other modalities.

Impact of different surgical strategies on perioperative protein S100β release in elderly patients undergoing coronary artery bypass grafting

OBJECTIVE

This study was designed to compare neurological injury-associated protein S100β release during three different treatment modalities, minimized closed circuit coronary artery bypass grafting (CABG) (MCABG), off-pump CABG (OPCAB), and conventional CABG (CCABG), comprising high-volume prime and cold crystalloid cardioplegia. Our working hypothesis was that fluid restriction as provided by MCABG may decrease neurological injury-associated protein S100β release.

METHODS

In this prospective trial, in a tertiary center, 30 surgical patients (aged >70 years, 25 men and 5 women) undergoing first-time elective CABG were enrolled. The inclusion criteria were three-vessel disease and elective surgery. The exclusion criteria were left ventricular ejection fraction of less than 30%, use of clopidogrel, carotid disease, or needing fewer than three distal anastomoses. Protein S100β concentrations, hematocrit (Ht) levels, and PO2 levels were measured after induction of anesthesia, 10 minutes after reperfusion, upon arrival at the intensive care unit, 3 hours postoperatively at the intensive care unit, and the next morning. Statistics consisted of areas under the curve, peak levels, and correlation and variance tests.

RESULTS

A significant negative correlation was found indicating higher S100β release at lower Ht levels and at lower PO2 levels in all study groups. The lowest S100β variance was measured during MCABG (Wilks Λ P = 0.052). The perioperative Ht was significantly higher in the MCABG group and in the OPCAB group compared with the CCABG group (P = 0.04 vs P < 0.01). At all time points, the S100β protein concentration showed no significant differences between the different surgical techniques. The mean (95% confidence interval) values of S100 area under the curve were the following: CCABG, 2.3 (1.06-3.5); MCABG, 1.44 (0.6-2.21); and OPCAB, 1.87 (1.5-2.19) [independent nonparametric Kruskal-Wallis test (P = 0.13)]. The mean (95% confidence interval) peak S100 values (calculated as the maximum value seen in a patient during the research period) were the following: CCABG, 1.07 (0.4-1.68); MCABG, 0.59 (0.28-0.90); and OPCAB, 0.83 (0.59-1.06) [independent nonparametric Kruskal-Wallis test (P = 0.22)].

CONCLUSIONS

Despite similar perioperative S100β protein release for all techniques studied, higher Ht and PO2 levels correlated with lower S100β release within all study groups. The low S100β variance during the fluid restrictive MCABG technique may be due to more efficient oxygen transport to the brain provided by significantly higher perioperative Ht levels. Further prospective data are required to better understand this complex issue.

Bad aorta

As its outcomes improve, cardiac surgery has been performed on more and more cases which were previously considered to be difficult to deal with. However, there are still a number of problems to be solved regarding surgery on patients with severe sclerotic lesions in the ascending aorta, which we collectively call "bad aorta". Concerning a preoperative assessment of the ascending aorta, our report revealed no relationship between the severity of calcification detected with a preoperative non-enhanced CT and the aortic lesion found during the surgery. Meanwhile, an intraoperative epiaortic ultrasound enables us to make high-quality evaluations of the aorta without imposing much burden on the patient. This modality may be essential for cardiac surgery. As for surgical management for bad aorta, quite a few methods have been reported to this point, but the overall operative mortality rate and cerebrovascular accident rate are relatively high, at a little <10 %, respectively. With the recent cross-clamping method under short-term total circulatory arrest (TCA), however, the results are much better; these rates total around 5 %. Further improvement is expected in the outcome of cardiac surgery on bad aorta cases by establishing a modality to evaluate sclerotic lesions in the ascending aorta with epiaortic ultrasound and by selecting a proper procedure for each case.

Influence of carotid injury in post-myocardial revascularization surgery and its late evolution

BACKGROUND

Approximately 30% of perioperative CVA of myocardial revascularization surgery (MRS) are a result of carotid injuries, without reduction of risk confirmed by perioperative intervention.

OBJECTIVES

Evaluate the impact of carotid disease and perioperative intervention in patients subjected to MRS.

METHODS

Observational, retrospective study, evaluating 1169 patients aged > 69 years undergoing MRS from January, 2006 and December, 2010, monitored, on average, for 49 months. All patients were subjected to ultrasonography of carotids before MRS. It was defined as carotid disease when lesion > 50%. The primary outcome was composed of CVA incidence, transitory ischemic accident (TIA) and death due CVA.

RESULTS

Prevalence of carotid disease was of 19.9% of patients. The incidence of primary outcome between unhealthy and healthy patients was of 6.5% and 3.7%, respectively (p = 0.0018). In the first 30 days, there were 18.2% of events. Were related to carotid disease: renal dysfunction (OR 2.03, IC95% 1.34-3.07; p < 0.01), peripheral arterial disease (OR 1.80, IC95% 1.22-2.65; p < 0.01) and previous myocardial infarction (OR 0.47, IC95% 0.35-0.65; p < 0.01). Regarding the primary outcome, were associated the previous TIA (OR 5.66, IC95% 1.67-6.35; p < 0.01) and renal dysfunction (OR 3.28, IC95% 1.67-6.45; p < 0.01). In patients with lesion >70%, perioperative carotid intervention demonstrated an incidence of 16% in primary outcome compared to 4.3% in conservatory treatment (p = 0.056) with no difference between percutaneous and surgical approaches (p = 0.516).

CONCLUSION

Carotid disease increases the risk of CVA, TIA or death due to CVA in MRS. However, the carotid intervention was not related to reduction of primary outcome.

Anatomic and flow dynamic considerations for safe right axillary artery cannulation

OBJECTIVES

Neuroprotection is of paramount interest in cardiac surgery. Right axillary artery cannulation is well established in aortic surgery because it significantly improves survival and outcome, but malperfusion of the right brain after direct cannulation has been reported. Anatomically, 4 vessel segments are potentially amenable for cannulation of the subclavian and axillary arteries. Clinical studies vary widely in dissection sites and cannulation techniques. We investigated critical flow dynamics in the right brain caused by arterial inflow after direct cannulation and specified cannulation positions that provide optimal cerebral perfusion.

METHODS

Distances from the lateral margin of the axillary artery and the subclavian artery to the origin of the vertebral artery were measured in 14 human corpses by a flexible ruler. We calculated the hemodynamics within the vertebral artery, depending on different positions of the cannula tip, in a computer-calculated model.

RESULTS

The mean distance from the axillary artery to the vertebral artery was 8.5 cm, and the mean distance from the subclavian artery to the vertebral artery was 6.7 cm. Computed flow calculations demonstrated reversed flow in the vertebral artery when the cannula tip was positioned too close to its orifice. To ensure safe supra-aortic flow, a cannula can be inserted securely up to 6.0 cm into the axillary artery and 4.2 cm into the subclavian artery.

CONCLUSIONS

Direct cannulation of the right axillary artery can lead to cerebral malperfusion, caused by an obstruction of the vertebral artery's orifice by the arterial cannula or a subclavian steal phenomenon due to flow reversal. The safety of direct axillary artery cannulation can be improved by a well-considered dissecting site and insertion length of the cannula.

Neurocognitive outcomes after cardiac surgery

PURPOSE OF REVIEW

To summarize recent studies of neurocognitive dysfunction after cardiac surgery, as well as to outline efforts and approaches toward advancing the field.

RECENT FINDINGS

Observational studies have improved our understanding of the incidence and the trajectory of cognitive decline after cardiac surgery; however, the magnitude of this neurocognitive change remains controversial because of the inconsistent definitions and the lack of a gold-standard diagnostic modality. Nonetheless, physicians commonly see patients with functional and cognitive impairments after cardiac surgery, which utilize healthcare resources and impact quality of life. Novel approaches have utilized advanced neuroimaging techniques as well as innovative monitoring modalities to improve the efficiency of neuroprotective strategies during cardiac surgery.

SUMMARY

Adverse cognitive and neurologic outcomes following cardiac surgery range from discrete neurocognitive deficits to severe neurologic injury such as stroke and even death. The elderly are at higher risk of suffering these outcomes and the public health dimension of this problem is expected to accelerate. Future studies should combine advanced neuroimaging with genomic, transcriptional, proteomic, and metabolomic profiling to improve our understanding of the pathophysiologic mechanisms and optimize the diagnosis, prevention, and treatment of neurocognitive injury.

Intraoperative epiaortic scanning for preventing early stroke after off-pump coronary artery bypass

BACKGROUND

Numerous studies have demonstrated the accuracy of epiaortic ultrasound scanning (EAS) for assessing ascending aortic disease. It remains unclear whether EAS changes the incidence of perioperative stroke after off-pump coronary artery bypass (OPCAB).

METHODS

We studied a retrospective cohort of 2292 patients who underwent isolated OPCAB from January 2001 to December 2011. Patients were retrospectively subdivided into two groups: the non-EAS group (n=1019) who underwent OPCAB under only intraoperative transoesophageal echocardiography and the EAS group (n=1273) who underwent OPCAB under EAS.

RESULTS

In the non-EAS group, 317 (31.1%) patients underwent OPCAB with partial aortic clamping and 702 (68.9%) underwent OPCAB without partial aorta clamping. In the EAS group, 301 (23.7%) patients underwent OPCAB with partial aortic clamping and 972 (76.3%) underwent OPCAB without partial aortic clamping. The incidence of early stroke was not different statistically between the EAS and non-EAS groups [non-EAS 1.7% (17/1019) vs EAS 0.8% (10/1273); P=0.052]. However, in the subgroups of patients with partial aorta clamping, the incidence of the early stroke was significantly lower in the EAS group [2.8% (9/317) vs 0.7% (2/301) P=0.041].

CONCLUSIONS

EAS has a significant clinical benefit in reducing the incidence of early stroke in cases of partial aortic clamping in OPCAB. Therefore, EAS should be considered in patients who need partial aortic clamping in OPCAB.

Clampless technique during coronary artery bypass grafting for proximal anastomoses in the hostile aorta

OBJECTIVE

The incidence of stroke in patients undergoing coronary artery bypass grafting increases sharply in the face of significant atherosclerotic disease of the ascending aorta. We use a technique that allows full revascularization for this cohort of patients, while minimizing cerebral embolic risk.

METHODS

Intraoperative epiaortic ultrasound was used to screen for moderate or severe atherosclerotic disease of the ascending aorta and to precisely identify safe areas for cannulation and proximal anastomoses. By using a mildly hypothermic fibrillating technique, distal revascularization was then performed without clamping the aorta. Proximal anastomoses were accomplished under brief periods of circulatory arrest.

RESULTS

We routinely use this technique and examined our results in 71 consecutive patients found to have grade 3 or greater atherosclerotic plaque of the ascending aorta. This represented approximately 10.0% of our total population who underwent coronary artery bypass grafting over a 32-month period from January 2007 to September 2009. One patient (1.4%) had a mild stroke that resolved, and there were no other neurologic complications.

CONCLUSIONS

We have found that clampless fibrillating heart surgery with circulatory arrest for proximal anastomoses is a safe and effective technique for revascularizing patients with significant ascending aortic disease who are at high risk for cerebral embolic complications.

The relation between atherosclerosis and the occurrence of postoperative delirium in vascular surgery patients

Old and frail patients undergoing vascular surgery seem at great risk of developing postoperative delirium (POD). The aim of this review was to identify risk factors for the development of POD in vascular surgery patients. Different aetiological factors have been identified, such as increased age, excessive blood transfusion, preoperative cognitive impairment and depression. Mounting evidence supports a role for inflammation and tobacco exposure in the development of POD. Vascular surgery patients differ from the general surgical population because they suffer from both loco-regional and systemic atherosclerosis. Although current scientific evidence cannot fully link both entities, evidence is growing that suggests a relationship between systemic and cerebrovascular atherosclerosis and the development of POD.

Seizures after cardiac surgery

INTRODUCTION

Cardiac surgery, mainly in the form of coronary artery bypass graft surgery, is known to be associated with a risk of injury to the central and peripheral nervous systems. The most commonly encountered central nervous system injury associated with cardiac surgery continues to be stroke, with seizures occurring less commonly but with significant consequences. Seizures in the cardiac surgery recovery unit (CSRU) always cause great concern to the attending physicians and families of the patient. Therefore, it is of critical importance that the attending physician has an accurate and efficient approach to the differential diagnosis, investigations, and management of these patients, who represent a unique group requiring specific investigations and management.

METHODS

A review and discussion of experience with seizures in the CSRU.

DISCUSSION

Cardiac surgery poses a significant threat to the nervous system through various mechanisms although newer technologies and surgical techniques have led to improved outcomes in recent years. Although the incidence of seizures remains low, the causes and management are relatively unique in this setting, including a probable "toxic syndrome" related to certain antibiotics or other perioperative drugs such as tranexamic acid. A targeted approach based on recognizing focal versus generalized seizures, a careful review of history and medications, and a focused workup will lead the clinician to choosing the most effective therapy when one is required. Special concerns regarding the side effect profile of phenytoin in this setting have led to valproate and levetiracetam becoming useful alternatives, which are effective and well tolerated. The incidence of nonconvulsive seizures in the CSRU remains to be elucidated with prospective monitoring studies, as does their effect on outcome.

Aortic atheroma and adverse cerebral outcome: risk, diagnosis, and management options

Aortic atheromatous disease is a common finding in the patient presenting for cardiac surgery. Adverse neurologic outcome has been closely linked to the extent of aortic atherosclerosis. In order to optimize perioperative outcomes, the location and severity of disease needs accurate characterization using multimodal techniques. Although various preoperative radiographic techniques have variably identified patients with significant atheroma, intraoperative echocardiographic imaging has proven most useful in localizing and characterizing the degree of aortic atheroma. Epiaortic assessment of the ascending aorta has been utilized in guiding surgical modifications and interventions aimed at reducing the risk of neurologic injury. Although no particular technique has been definitely studied, avoidance of the identifiable atheromatous aortic region has been a main feature of the various modifications employed to optimize neurologic outcome after cardiac surgery.

Avoiding stroke during cardiac surgery

The life saving benefits of cardiac surgery are frequently accompanied by negative side effects such as stroke, that occurs with an incidence of 2%-13% dependent to type of surgery. The etiology is most likely multifactorial with embolic events considered as main contributor. Although stroke presents a common complication, no guidelines for any routine use of pharmacological substances or non-pharmacological strategies exist to date. Non-pharmacological strategies include monitoring of brain oxygenation and perfusion with devices such as near infrared spectroscopy and Transcranial Doppler help. Epiaortic and transesophageal echocardiography visualize aorta pathology, enabling the surgeon to sidestep atheromatous segments. Additionally can the use of specially designed aortic cannulae and filters help to reduce embolization. Brain perfusion can be improved by using antero- or retrograde cerebral perfusion during deep hypothermic circulatory arrest, by tightly monitoring mean arterial blood pressure and hemodilution. Controlling perioperative temperature and glucose levels may additionally help to ameliorate secondary damage. Many pharmacological compounds have been shown to be neuroprotective in preclinical models, but clinical studies failed to confirm these results so far. Remacemide, an NMDA-receptor-antagonist showed a significant drug-based neuroprotection during cardiac surgery. Other substances currently assessed in clinical trials whose results are still pending are acadesine, an adenosine-regulating substance, the free radical scavenger edaravone and the local anesthetic lidocaine. Stroke remains as significant complication after cardiac surgery. Non-pharmacological strategies allow perioperative caregivers to detect injurious events and to ameliorate stroke and its sequelae. Considering the multi-factorial etiology though, stroke prevention will likely have to be addressed with an individualistic combination of different strategies and substances.

Postoperative cognitive dysfunction and aortic atheroma

BACKGROUND

The relationship of aortic atheroma to postoperative cognitive dysfunction (POCD), a common complication of coronary artery bypass graft surgery, has not been resolved. We undertook assessment of aortic atheroma using intraoperative ultrasonography and related the degree of aortic atheroma to POCD.

METHODS

Aortic atheroma was assessed using intraoperative transesophageal and epiaortic echocardiography in 311 patients who underwent coronary artery bypass graft surgery. Atheroma was graded from 0 (normal or minimal) to 3 (mobile or rough) in each of four quadrants of the proximal ascending to proximal descending thoracic aorta. Atheroma burden was defined as the atheroma score divided by the total possible score for that patient. Patients also completed a neuropsychological battery consisting of eight tests taken the week before surgery and at 1 week and 3 and 12 months afterward. Decreased cognitive function for each test was defined as an individual decrease of at least 1 standard deviation of the group baseline mean for that test, and POCD was defined as a decrease in two or more tests.

RESULTS

The atheroma burden (%) was greater in the patients with POCD. The difference was greatest at 1 week (10.4+/-14.7 versus 4.4+/-9.0, p=0.0002) and diminished progressively at 3 months (8.9+/-14.1 versus 5.4+/-10.1, p=0.06) and 12 months (6.6+/-12.0 versus 5.6+/-10.2, p=0.56). Multivariable analysis showed that atheroma burden strongly predicted POCD at 1 week.

CONCLUSIONS

Aortic atheroma burden predicts POCD at 1 week but has less impact on POCD as time progresses. Atheroma burden is highly correlated with age and may be a good predictor of early POCD.

Perioperative hypothermia: use and therapeutic implications

Perioperative cerebral ischemic insults are common in some surgical procedures. The notion that induced hypothermia can be employed to improve outcome in surgical patients has persisted for six decades. Its principal application has been in the context of cardiothoracic and neurosurgery. Mild (32-35 degrees C) and moderate (26-31 degrees C) hypothermia have been utilized for numerous procedures involving the heart, but intensive research has found little or no benefit to outcome. This may, in part, be attributable to confounding effects associated with rewarming and lack of understanding of the mechanisms of injury. Evidence of efficacy of mild hypothermia is absent for cerebral aneurysm clipping and carotid endarterectomy. Deep hypothermia (18-25 degrees C) during circulatory arrest has been practiced in the repair of congenital heart disease, adult thoracic aortas, and giant intracranial aneurysms. There is little doubt of the protective efficacy of deep hypothermia, but continued efforts to refine its application may serve to enhance its utility. Recent evidence that mild hypothermia is efficacious in out-of-hospital cardiac arrest has implications for patients incurring anoxic or global ischemic brain insults during anesthesia and surgery, or perioperatively. Advances in preclinical models of ischemic/anoxic injury and cardiopulmonary bypass that allow definition of optimal cooling strategies and study of cellular and subcellular events during perioperative ischemia can add to our understanding of mechanisms of hypothermia efficacy and provide a rationale basis for its implementation in humans.

[Neuromonitoring and neuroprotection in cardiac anaesthesia. Nationwide survey conducted by the Cardiac Anaesthesia Working Group of the German Society of Anaesthesiology and Intensive Care Medicine]

OBJECTIVE

The primary objective of this nationwide survey carried out in department of cardiac anesthesia in Germany was to identify current practice with regard to neuromonitoring und neuroprotection.

METHODOLOGY

The data are based on a questionnaire sent out to all departments of cardiac anesthesia in Germany between October 2007 und January 2008. The anonymized questionnaire contained 26 questions about the practice of preoperative evaluation of cerebral vessels, intra-operative use of neuromonitoring, the nature und application of cerebral protective measures, perfusion management during cardiopulmonary bypass, postoperative evaluation of neurological status, and training in the field of cerebral monitoring.

RESULTS

Of the 80 mailed questionnaires 55% were returned and 90% of department evaluated cerebral vessels preoperatively with duplex ultrasound. The methods used for intra-operative neuromonitoring are electroencephalography (EEG, 60%) for type A dissections (38.1%), for elective surgery on the thoracic and thoraco-abdominal aorta (34.1% and 31.6%, respectively) and in carotid surgery (43.2%) near infrared spectroscopy (40%), evoked potentials (30%) and transcranial Doppler sonography (17.5%), with some centers using combined methods. In most departments the central nervous system is not subjected to monitoring during bypass surgery, heart valve surgery, or minimally invasive surgery. Cerebral protective measures used comprise patient cooling on cardio-pulmonary bypass (CPB 100%), extracorporeal cooling of the head (65%) and the administration of corticosteroids (58%), barbiturates (50%) and antiepileptic drugs (10%). Neuroprotective anesthesia consists of administering inhalation anesthetics (32.5%; sevoflurane 76.5%) and intravenous anesthesia (20%; propofol and barbiturates each accounting for 46.2%). Of the departments 72.5% cool patients as a standard procedure for surgery involving cardiovascular arrest and 37.5% during all surgery using CPB. In 84.6% of department CPB flow equals calculated cardiac output (CO) under normothermia, while the desired mean arterial pressure (MAP) varies between 60 and 70 mmHg (43.9%) and between 50 and 60 mmHg (41.5%), respectively. At body temperatures less than 18 degrees C CPB flow is reduced below the calculated CO (70%) while 27% of departments use normothermic flow rates. The preferred MAP under hypothermia is between 50 and 60 mmHg (59%). The results of intra-operative neuromonitoring are documented on the anesthesia record (77%). In 42.5% of the departments postoperative neurological function is estimated by the anesthesiologist. Continuing education sessions pertaining to neuromonitoring are organized on a regular basis in 32.5% of the departments and in 37.5% individual physicians are responsible for their own neuromonitoring education.

CONCLUSION

The present survey data indicate that neuromonitoring and neuroprotective therapy during CPB is not standardized in cardiac anesthesiology departments in Germany. The systemic use of available methods to implement multimodal neuromonitoring would be desirable.

Safer aortic crossclamping during short-term moderate hypothermic circulatory arrest for cardiac surgery in patients with a bad ascending aorta

OBJECTIVE

Cardiac surgery in patients with severely atherosclerotic or porcelain ascending aorta is technically challenging, with markedly increased risk of atheroembolism. We describe a technique of meticulous crossclamping of a difficult aorta during short-term moderate hypothermic circulatory arrest.

METHODS

From 1997 to 2007, we found 40 patients (mean age, 70 +/- 8 years), including 14 patients undergoing hemodialysis, whose preoperative computed tomographic and intraoperative epiaortic ultrasonographic scans revealed eggshell calcification (n = 15) or protruding atheromas (n = 25) of the ascending aorta. They underwent cardiac surgery (aortic, 31 patients; mitral, 3 patients; both, 5 patients; and coronary alone, 1 patient) by means of meticulous crossclamping during hypothermic circulatory arrest for 3.4 +/- 1.5 minutes at a rectal temperature of 29.0 degrees C +/- 2.3 degrees C. During hypothermic circulatory arrest, we performed only internal inspection to identify the safe location of crossclamping in 21 patients, whereas we required debridement of calcification or atheroma by using the Cavitron Ultrasonic Surgical Aspirator (Tyco Healthcare, Mansfield, Mass) for safe crossclamping in 19 patients.

RESULTS

By using this technique, no patients died during the hospital stay. Stroke occurred in 1 (2.5%) patient, and transient agitation occurred in 1 patient. Re-exploration for bleeding was required in 1 patient, and wound infection occurred in 2 patients. During follow-up, with a median time of 5.2 years, the overall survival rates were 100%, 90%, and 76% at 1, 3, and 5 years, respectively. Three patients required reoperations during the follow-up period because of pseudoaneurysm in 2 patients and prosthetic valve infection in 1 patient.

CONCLUSION

Short-term moderate hypothermic circulatory arrest is quite useful for safe aortic crossclamping after internal inspection or debridement in high-risk patients with a severely atherosclerotic aorta.

Amounts of aortic atherosclerosis in patients with aortic stenosis as determined by transesophageal echocardiography

We quantified the graded amounts of aortic atherosclerosis (AA) in patients with aortic stenosis (AS) to better delineate the need for preprocedural risk stratification. Complex AA is strongly related to embolic events, especially during open heart surgery and catheterization. Despite the frequency of these procedures in patients with AS and the increased prevalence of atherosclerosis, current guidelines do not recommend screening for AA. Patients with concomitant transesophageal and transthoracic echocardiograms were retrospectively identified. AS and AA were graded by expert reviewers as mild, moderate, and severe according to established guidelines. Three hundred sixty patients (212 men, mean age 69 +/- 14 years) were identified, 186 (52%) without AS, 82 (23%) with mild AS, 55 (15%) with moderate AS, and 37 (10%) with severe AS. There was a strong graded positive association between AA and AS (p <0.00001). The prevalence of severe AA increased across grades of AS. Of all patients with severe AS, 54% had severe AA. Of patients with severe AS not referred for an embolic event, 57% had severe AA. The odds ratio for severe AA was 4.9 (95% confidence interval 2.3 to 10.3) in patients with severe AS compared with without AS. In conclusion, AS and AA are closely correlated. The majority of patients with severe AS have severe AA, even without previous thromboembolic events. This significant atherosclerotic burden may warrant preprocedural risk assessment with transesophageal echocardiography.

Neurological complications of cardiac surgery

Neurological injury resulting from cardiac surgery has a range of manifestations from focal neurological deficit to encephalopathy or coma. As the safety of drug-eluting stents comes into question, more patients will likely undergo coronary artery bypass graft surgery. These projections, along with the growing proportions of elderly patients and those with comorbidities, portend the potential for rising rates of perioperative neurological complications. The risk for neurological injury may be determined by the type of procedure, by patient-specific characteristics, and by the extent of cerebral embolization and hypoperfusion during and after surgery. Changes in surgical techniques, including the use of off-pump surgery, have not decreased rates of brain injury from cardiac surgery. When appropriate, modern neuroimaging techniques should be used in postoperative patients to confirm diagnosis, to provide information on potential etiology, to direct appropriate therapy, and to help in prognostication. Management of postoperative medications and early use of rehabilitation services is a recommended strategy to optimize the recovery for individuals with neurological injury after cardiac surgery.

Intraoperative cerebral high-intensity transient signals and postoperative cognitive function: a systematic review

BACKGROUND

Much attention in the literature has focused on the relationship between perioperative microemboli during cardiac and vascular surgery and postoperative cognitive decline. Transcranial Doppler ultrasonography (TCD) has been used to measure high-intensity transient signals (HITS), which represent microemboli during cardiac, vascular, and orthopedic surgery. The purpose of this study was to systematically examine the literature with respect to HITS and postoperative cognitive function.

METHODS

Systematic PubMed searches identified articles related to the use of TCD and cognitive function in the surgical setting.

RESULTS

The literature remains largely undecided on the role of HITS and cognitive impairment after surgery, with most studies being underpowered to show a relationship. Although the cognitive effects of HITS may be difficult to detect, subclinical microemboli present potential harm, which may be modifiable.

CONCLUSIONS

TCD represents a tool for intraoperative cerebral monitoring to reduce the number of HITS during surgery.

Epiaortic scanning modifies planned intraoperative surgical management but not cerebral embolic load during coronary artery bypass surgery

BACKGROUND

Patients with aortic atheroma are at increased risk for neurological injury after coronary artery bypass graft (CABG) surgery. We sought to determine the role of epiaortic ultrasound scanning for reducing cerebral embolic load, and whether its use leads to changes of planned intraoperative surgical management in patients undergoing CABG surgery.

METHODS

Patients >70-yr-of-age scheduled for CABG surgery were prospectively randomized to either an epiaortic scanning (EAS) group (aortic manipulation guided by epiaortic ultrasound) or a control group (manual aortic palpation without EAS). All patients received a comprehensive transesophageal echocardiographic examination. Transcranial Doppler (TCD) was used to monitor the middle cerebral arteries for emboli continuously from 2 min before aortic cannulation to 2 min after aortic decannulation. Neurological assessment was performed with the National Institute of Health stroke scale before surgery and at hospital discharge. The NEECHAM confusion scale was used for assessment and monitoring of patient global cognitive function on each day after surgery until hospital discharge.

RESULTS

Intraoperative surgical management was changed in 16 of 55 (29%) patients in the EAS group and in 7 of 58 (12%) patients in the control group (P = 0.025). These changes included adjustments of the ascending aorta cannulation site for cardiopulmonary bypass (CPB), the avoidance of aortic cross-clamping by using ventricular fibrillatory arrest during surgery, or by conversion to off-pump surgery. During surgery, 7 of 58 (12%) patients in the control group crossed over to the EAS group based on the results of manual aortic palpation. The median [range] TCD detected cerebral embolic count did not differ between the EAS and control groups during aortic manipulations (EAS, 11.5 [1-516] vs control, 22.0 [1-160], P = 0.91) or during CPB (EAS, 42.0 [4-516] vs control, 63.0 [5-758], P = 0.46). The NEECHAM confusion scores and National Institute of Health stroke scale scores were similar between the two groups.

CONCLUSIONS

These results show that the use of EAS led to modifications in intraoperative surgical management in almost one-third of patients undergoing CABG surgery. The use of EAS did not lead to a reduced number of TCD-detected cerebral emboli before or during CPB.

Neuroprotection during cardiac surgery

Cardiac surgery continues to be associated with significant adverse cerebral outcomes, ranging from stroke to cognitive decline. The underlying mechanism of the associated cerebral injury is incompletely understood but is believed to be primarily caused by cerebral embolism and hypoperfusion, exacerbated by ischemia/reperfusion injury. Extensive research has been undertaken in an attempt to minimize the incidence of perioperative cerebral injury, and both pharmacological and nonpharmacological strategies have been investigated. Although many agents demonstrated promise in preclinical studies, there is currently insufficient evidence from clinical trials to recommend the routine administration of any pharmacological agents for neuroprotection during cardiac surgery. The nonpharmacological strategies that can be recommended on the basis of evidence include transesophageal echocardiography and epiaortic ultrasound-guided assessment of the atheromatous ascending aorta with appropriate modification of cannulation, clamping or anastomotic technique and optimal temperature management. Large-scale randomized controlled trials are still required to address further the issues of optimal pH management, glycemic control, blood pressure management and hematocrit during cardiopulmonary bypass. Past, present and future directions in the field of neuroprotection in cardiac surgery will be discussed.

Mechanisms of cerebral injury from cardiac surgery

Cerebral injury is a frequent complication of cardiac surgery, and it has been associated with high mortality, morbidity, hospital costs; an increased likelihood of admission to a secondary care facility after hospital discharge; and impaired quality of life. This article examines postulated mechanisms for cerebral injury from cardiac surgery. Most emphasis has been placed in the past on the intraoperative interval as being the period of highest cerebral vulnerability. Many clinical cerebral events, however, occur in the postoperative period.