Risk factors for cerebral injury and cardiac surgery

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.

The Effect of Circadian Melatonin Levels on Inflammation and Neurocognitive Functions Following Coronary Bypass Surgery

PURPOSE

In this study, the relationship between the plasma levels of melatonin and intercellular adhesion molecule-1 (ICAM-1), which plays role in several intercellular interactions including inflammatory and immune responses, and early neurocognitive functions associated with ischaemia-reperfusion injury during open heart surgery is examined.

METHODS

Forty patients who were to undergo elective coronary artery bypass grafting (CABG) were divided into two groups, those who underwent their operations at 8 AM (group I; n = 20) and those who underwent their operations at 1 PM (group II; n = 20). Blood samples were collected prior to surgery (S1), when the aortic cross clamp was removed (S2) and 4 (S3) and 24 h after the surgery (S4). Neuropsychiatric assessment was conducted one day before and seven days after surgery.

RESULTS

Melatonin levels measured during and after surgery were also significantly higher in Group 1. ICAM-1 levels were significantly lower in Group 1 at S2 and S3. Significant deterioration was observed in postoperative neurocognitive function compared with preoperative functions in Group 2 more than Group 1.

CONCLUSION

We hypothesise that the greater preservation of neurocognitive functions in the morning patients is associated with elevated melatonin levels, which reduce the damage from ischaemia-reperfusion injury.

Selective Screening for Asymptomatic Carotid Artery Disease Prior to Isolated Heart Valve Surgery

Objective

To assess the yield of screening for asymptomatic carotid artery disease prior to isolated heart valve surgery (IHVS).

Methods

Retrospective analysis of the preoperative carotid duplex scans performed in neurologically asymptomatic patients who underwent IHVS between 2003 and 2006 was performed. Internal carotid artery (ICA) stenosis of 70% was considered significant. Patients with concomitant coronary artery disease were excluded.

Results

A total of 177 patients underwent IHVS (one valve in 165 and 2 valves in 12 patients). No or minor ICA disease detected in 172 patients. Four patients (2.25%) had significant unilateral ICA stenosis and 1 patient (0.56%) had unilateral ICA occlusion. Three patients (1.69%) suffered postoperative stroke, while 2 patients (1.1%) suffered transient ischemic attacks. All neurologically affected patients had normal preoperative carotid duplex. The in-hospital mortality was 4.5%.

Conclusion

Prevalence of significant ICA disease is low in patients undergoing IHVS. This population does not benefit from preoperative carotid screening.

Technology insight: brain MRI and cardiac surgery--detection of postoperative brain ischemia

Annually, an estimated 1 million patients undergo heart surgery worldwide. Unfortunately, stroke continues to be a frequent complication of cardiac surgery, with the specific cerebrovascular risk depending upon the particular surgical procedure performed. Neuroimaging has an integral role in the initial evaluation and management of patients who present with acute stroke symptoms following cardiac surgery. The aim of this paper is to review the role brain MRI has in detecting postoperative brain ischemia in these patients. Multimodal MRI--using diffusion-weighted MRI (DWI), perfusion-weighted MRI, and gradient-recalled echo imaging--has an excellent capacity to identify and delineate the size and location of acute ischemic strokes as well as intracerebral hemorrhages. This differentiation is critical in making appropriate treatment decisions in the acute setting, such as determining patient eligibility for thrombolytic or hemodynamic therapies. At present, DWI offers prognostic value in patients with strokes following cardiac surgery. Additionally, DWI could be a valuable tool for evaluating stroke preventive measures as well as therapeutic interventions in patients undergoing CABG surgery.

Apolipoprotein E e4 Allele and Neurobehavioral Status After On-Pump Coronary Artery Bypass Grafting

Abstract Background and Aim: The presence of apolipoprotein E epsilon4 allele is being considered as a risk factor for cognitive decline after cardiac surgery. We sought the effect of apolipoprotein E epsilon4 allele on neurobehavioral status after on-pump coronary artery bypass grafting.

METHODS

Prior to the operation, neurologic examination and neurobehavioral cognitive status test (COGNISTAT) were performed. Both procedures were repeated on the day of discharge and 3 months after surgery. Apolipoprotein E epsilon4 allele positive and apolipoprotein E epsilon4 allele negative patients' performance on COGNISTAT were compared.

RESULTS

There was no statistically significant demographic and operative data difference between two groups. No neurological impairment was observed on examinations. There was no statistically significant neurocognitive decline difference between two groups' postoperative performances.

CONCLUSIONS

It seems that apolipoprotein E epsilon4 allele may not affect neurobehavioral status in the intermediate period after on-pump coronary artery bypass grafting.

Off-pump coronary artery bypass grafting reduces postoperative neurologic complications

OBJECTIVE

Complications occurring after coronary artery bypass graft (CABG) surgery, particularly neurologic damage, have been mainly correlated with the use of cardiopulmonary bypass (CPB). The aim of this work was to compare postoperative outcomes of patients undergoing CABG surgery, with or without the use of CPB, focusing on neurologic events.

DESIGN

Observational study.

SETTING

University tertiary care hospital.

PARTICIPANTS

Two thousand seven hundred and forty consecutive patients who underwent CABG surgery in the period January 1998 to January 2003.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

For 738 patients, the operation was performed off-pump (OP group), and for 2002 patients CPB was used (CPB group). OP and CPB groups were compared with regard to preoperative status, anesthetic management, and postoperative outcomes, by means of univariate and multivariate analyses. Surgeons' propensity to operate off-pump was based on patients' age, renal conditions, and hemodynamics. Univariate and multivariate analyses showed that CPB was associated with a higher incidence of type I neurologic events compared with OP technique (2.1% versus 0.9%, odds ratio [OR]: 2.6, 95% confidence interval [CI], 1.2-5.9). A history of previous stroke (OR: 2.7, 95% CI, 1.2-5.9) and advanced age (OR: 1.06 per year, 95% CI, 1.02-1.09) were additional independent predictors of postoperative type I neurologic events.

CONCLUSIONS

In the authors' experience, off-pump CABG surgery offers some benefits compared with CPB in respect to major neurologic complications.

Sleep, memory, and learning in off-pump coronary artery bypass patients

In this study, I examined sleep, memory, and learning in off-pump coronary artery bypass (OPCAB) patients. Sixty-six men and women aged >or=60 years wore actigraphs to record sleep and completed sleep diaries for two 24-hour periods following OPCAB surgery. Prior to discharge from the hospital, participants completed the Pittsburgh Sleep Quality Index (PSQI) and Rey Auditory Verbal Learning Test. No significant correlations were found between habitual sleep, sleep time, efficiency, number, and duration of awakenings, daytime napping, or memory and learning. Nighttime sleep was short with frequent disturbances, and daytime sleep accounted for half the daily sleep time. Participants scored low in learning and delayed recall. These findings suggest the need to assess sleep and cognition in patients recovering from OPCAB surgery.

Neuropsychological Outcome After Percutaneous Coronary Intervention or Coronary Artery Bypass Grafting

Background— Coronary artery bypass surgery (CABG) has been associated with a range of neurological and neuropsychological complications from stroke to cognitive problems such as memory and problem solving disturbance. However, little is known about the impact of percutaneous coronary intervention (PCI) on neuropsychological outcome.

Methods and Results— In the Stent or Surgery Trial (SoS), 988 patients were randomized in equal proportions between PCI supported by stent implantation and CABG. As a substudy of this trial, we undertook an evaluation of neurological and neuropsychological outcomes after intervention. A clinical examination and neuropsychological assessment consisting of 5 tests (Digit Span Forwards and Backwards, Visual Reproduction, Bourdon, and Block Design) were performed at baseline and 6 and 12 months after the procedure. A total of 145 patients were included in the substudy analysis: 77 in the PCI group and 68 in the CABG group. One patient in the PCI arm had a stroke. There was no significant difference between treatment groups at 6 and 12 months for any of the 5 tests. The mean change from baseline was also similar in both groups.

Conclusions— We were not able to demonstrate an important and significant difference in neuropsychological outcome in patients treated with different revascularization strategies. This important finding needs to be examined in further research.

Cerebral embolism in off-pump coronary artery bypass grafting

A 64-year-old woman with a history of cerebral infarction from chronic occlusion of the middle cerebral artery presented with acute myocardial infarction. Double, off-pump coronary artery bypass grafting could not prevent stroke caused by atheroembolism from the ascending aorta. The risk of stroke from atheroembolism should be taken into consideration when planning coronary artery bypass grafting.

Risk factor analysis of early and delayed cerebral complications after cardiac surgery

OBJECTIVE

To report the incidence, severity, and possible risk factors for early and delayed cerebral complications.

DESIGN

Retrospective study.

SETTING

Linköping University Hospital, Sweden.

PARTICIPANTS

Consecutive patients who underwent cardiac surgery in the period July 1996 through June 2000 (n = 3,282).

INTERVENTIONS

A standard cardiopulmonary bypass (CPB) technique was used for most patients. Postoperative anticoagulant treatment included heparin or anti-Xa dalteparin. Patients undergoing coronary artery bypass graft surgery received acetylsalicylic acid, and patients undergoing valve surgery received warfarin.

MEASUREMENTS AND MAIN RESULTS

Cerebral complications occurred in 107 patients (3.3%). Of these, 60 (1.8%) were early, and 33 (1.0%) were delayed, and in 14 (0.4%) patients the onset was unknown. There were 37 variables in univariate analysis (p < 0.15) and 14 variables in multivariate analysis (p < 0.05) associated with cerebral complications. Predictors of early cerebral complications were older age, preoperative hypertension, aortic aneurysm surgery, prolonged CPB time, hypotension at CPB completion and soon after CPB, and postoperative arrhythmia and supraventricular tachyarrhythmia. Predictors of delayed cerebral complications were female gender, diabetes, previous cerebrovascular disease, combined valve surgery and coronary artery bypass graft surgery, postoperative supraventricular tachyarrhythmia, and prolonged ventilator support. Early cerebral complications seem to be more serious, with more permanent deficits and a higher overall mortality (35.0% v 18.2%).

CONCLUSION

Most cerebral complications had an early onset. The results of this study suggest that aggressive antiarrhythmic treatment and blood pressure control may imfurther prove the cerebral outcome after cardiac surgery.

The utility of preoperative routine carotid artery duplex scanning in patients undergoing aortic valve replacement

Patients with aortic valve disease (AVD) typically have a cardiac murmur that radiates to the neck and may be indistinguishable from a cervical bruit secondary to carotid artery occlusive disease. The purpose of this report was to determine the prevalence of significant asymptomatic carotid artery occlusive disease in patients undergoing aortic valve replacement (AVR). All patients scheduled for AVR were prospectively studied. Preoperative carotid artery color-flow duplex was performed in all patients. A total of 204 patients were included in the study and significant carotid disease (>50% stenosis of the internal carotid artery) was found in 17 (8%). In patients with isolated aortic valve disease, 4/129 (3%) had significant stenosis. Of the patients with concurrent aortic valve and coronary artery disease, 13/75 (17%) had significant stenosis. The incidence of significant carotid stenosis in patients with aortic valve disease was over five fold higher in patients with concurrent coronary artery disease (3% vs. 17%, p <0.001). The yield of routine carotid duplex scanning for patients undergoing isolated AVR is low. However, in the subset of patients with concurrent coronary disease, the yield is higher. This finding supports the use of routine carotid duplex scanning in patients with coexistent aortic valve and coronary artery disease.

Feasibility and risks of heart surgery in very elderly: analysis of 200 consecutive patients of 80 years and above

A continuing increase in the number of very elderly patients with symptomatic heart disease referred for cardiac surgery has been observed in the past. Since 1990 all patients of 80 years and above have been included in a prospective study. We report on the results of the first 200 consecutive patients (mean age: 82.2+/-2.1 years). Operative procedures ranged from isolated myocardial revascularization and valve replacement to very complex operations. In a majority of patients, the operations had to be performed as urgent or emergency cases because of advanced heart disease. Overall 30 day mortality was 9.5%. More than two thirds of patients needed treatment of perioperative complications. During long-term follow-up, cardiac surgery in octogenarians has proved to be very effective with excellent functional status and quality of life. Because of favorable results elderly patients should not be denied the benefits of cardiac surgery requiring utilization of significant medical resources.

Beating heart surgery or conventional CABG: are neurologic outcomes different?

Although there has been much debate about the causes of neurologic complications associated with coronary artery bypass grafting (CABG), there is good evidence linking such complications with some of the pathophysiologic changes associated with use of conventional cardiopulmonary bypass (CPB). Several studies indicate that it is possible to significantly lower risk of stroke and other central nervous system (CNS) morbidity in patients undergoing CPB for CABG by application of selected techniques and equipment modifications. The resurgence of interest in coronary revascularization by using beating heart surgery (BHS) offers a unique opportunity to evaluate neurologic outcome independent of CPB. Currently, BHS would appear to significantly reduce morbidity in the elderly and to decrease the costs and resource use in coronary revascularization patients. It is hoped that by understanding the mechanisms of CNS injury associated with CABG, techniques can be developed to decrease the risk of neurologic injury associated with coronary revascularization, whether or not CPB is used. Definitive conclusions regarding outcomes after best practice CPB or BHS await large-scale, risk-stratisfied multicenter trials.

Reconstructive surgery of the extracranial arteries

The first carotid endarterectomy (CEA) is usually accredited to Eastcott who reported in 1954 the successful incision of a diseased carotid bulb with end-to-end anastomosis of the internal carotid artery (ICA) to the common carotid artery (CCA). During the following years surgeons were quick to adopt and improve the intuitively attractive procedure. But by the early to mid 1980s several leading neurologists began to question the growing number of CEAs performed at that time. Six major CEA trials were then designed which are now completed or nearing completion. Most conclusive data are available from the North American Symptomatic Carotid Endarterectomy Trial (NASCET) for symptomatic carotid disease, and from the Asymptomatic Carotid Atherosclerosis Study (ACAS) for asymptomatic carotid disease. The key result of these studies is that CEA is beneficial to high grade symptomatic and asymptomatic carotid stenosis. While the benefit in symptomatic disease is clear, it may be negligible in asymptomatic patients suffering from other medical conditions, the most important being coronary artery disease. Since the conclusions from the different studies vary significantly, guidelines and recommendations with regard to CEA have been issued by a number of interest groups, so-called consensus conferences. The best known guidelines are published by the American Heart Association (AHA). However, the practice of interest groups to issue guidelines is currently being criticized, the main reason being that interest groups have different ideas and all claim the right to issue guidelines. At present we recommend CEA for symptomatic high-grade stenosis in patients without significant coincident disease. With regard to asymptomatic stenosis we suggest surgery to otherwise healthy patients if the stenosis is very narrow or progressive. Preoperative evaluation has changed over the years. Currently we recommend duplex sonography in combination with intra- and extracranial magnetic resonance angiography (MRA). Concurrent coronary artery disease is a major consideration in the perioperative management, and the use of a specific algorithm is recommended. Surgery is performed under general anaesthesia with intraoperative monitoring such as electroencephalography (EEG) and transcranial Doppler (TCD). A temporary intraluminal shunt is used selectively if after cross-clamping the flow velocity in the middle cerebral artery (MCA) falls to below 30 to 40% of baseline. For years we employed routine barbiturate neuroprotection during cross-clamping. At the present time we use barbiturate selectively, if the flow velocity in the MCA falls to below 30 to 40% of baseline and if the use of a temporary intraluminal shunt is not possible due to difficult anatomic conditions. The reason to abandon systematic barbiturate protection was to accelerate recovery from anaesthesia. Our patients are monitored overnight on the ICU or a surveillance unit. Routine hospitalization after surgery is 5 to 7 days with a control duplex sonography being performed prior to discharge. A number of details with regard to surgical technique and perioperative management are a matter of discussion. Our surgical routine is described here step by step. Such management resulted in 6 major complications among the 402 cases with 4 of cardiopulmonary and 2 of cerebrovascular origin. For the future we can expect the development of percutaneous transluminal techniques competing with standard carotid endarterectomy. At the present time several comparative studies are under way. Irrespective of the technical approach to treat carotid stenosis, several other issues have to be clarified before long. One of the major unresolved items is the timing of treatment after completed stroke. In this regard prospective trials need to be performed. Although numerically not as important as carotid stenosis, vertebral artery (VA) and subclavian artery (SA) stenoses are more and more accepted as indication for surgical

Combined Surgery for cardiac and carotid disease: management and results of a rational approach

OBJECTIVES

The aim of the present study was to apply a rational plan for simultaneous cardiac and carotid surgery in high-risk patients.

MATERIALS AND METHODS

A consecutive series of 89 patients with coexisting severe cardiac and carotid disease were operated on during a 5-year period with routinary carotid shunting, moderate hypothermia and balanced anaesthesia. The combined surgical procedures were coronary artery by-pass grafts (CABG) + carotid endarterectomy (CEA) in 81 patients, CABG + CEA + aortic valve replacement (AVR) in four patients, and four cases of CEA + AVR. RESSULTS: Two deaths (2%), three acute myocardial infarctions (3%) and one (1%) major stroke occurred in five patients during the perioperative (30 days) period for a combined rate of death and/or disabling stroke of 3%. There were five reversible neurological deficits. Carotid and aortic mean clamping times were 9 and 60 min respectively. Patients were discharged after a mean length of stay in Intensive Care Unit (ICU) of 131 h and 7 days of hospitalisation post-ICU.

CONCLUSIONS

Based on our results, combined interventions of CEA and CABG can be performed with an acceptable morbidity and mortality when severe carotid stenosis is associated with advanced, symptomatic cardiac disease. The management of these patients needs careful and appropriate pre-intra and post-operative assessment and timing aimed to reduce the ischaemic injuries, both cardiac and cerebral, especially during CBP time.

Issues associated with the identification of cognitive change following coronary artery bypass grafting

OBJECTIVE

Coronary artery bypass grafting (CABG) is a surgical procedure used to treat individuals with ischaemic heart disease and to relieve angina. Disruption to the central nervous system (CNS) has frequently been reported by patients who have undergone CABG.

METHOD

The following paper is a review of the literature that has examined the effects of CABG on the CNS.

RESULTS AND CONCLUSIONS

It becomes apparent that issues about the incidence and severity of post-CABG cognitive decline are still unresolved. First, the cause of post-CABG CNS change has not yet been established, although the presence of changes to brain microvasculature as a result of the presence of microemboli appears to be a likely factor. Second, while some studies have reported high rates of poor performance on neuropsychological tests postoperatively, these reports are often subject to confounds such as variability in postoperative testing intervals, the definition of decline and the neuropsychological test batteries used. Finally, improvements in surgical techniques and changes in patient characteristics may have changed the real nature and prevalence of post-CABG cognitive decline. The review finishes with a series of recommendations for the neuropsychological study of CABG.

Neurocognitive dysfunction after coronary artery bypass surgery: a systematic review

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Serum S100 protein as a marker of cerebral damage during cardiac surgery

The identification of a serum marker to assist in the diagnosis of cerebral injury after cardiac surgery is potentially useful. S100 protein is an early marker of cerebral damage. It is released after cardiac surgery performed under cardiopulmonary bypass (CPB). Its level is correlated with the duration of CPB, deep circulatory arrest and aortic cross-clamping. Increased levels of S100 protein are correlated with the age of the patient and the number of microemboli, especially during aortic cannulation. Perioperative cerebral complications such as stroke, delayed awakening and confusion are associated with increased levels of S100 protein directly after bypass and from 15 to 48 h after it. In addition, increased levels of S100 protein are related to neuropsychological dysfunction after cardiac surgery. S100 protein has early and late release patterns after CPB; the early pattern may be due to sub-clinical brain injury. The late release pattern may be due to perioperative cerebral complications. Patients undergoing intracardiac operations combined with coronary artery bypass surgery are more susceptible to brain injury and have higher levels of S100 after CPB. Furthermore, adults and children undergoing deep circulatory arrest are more susceptible to brain injury, in terms of higher S100 protein release after CPB. Serum S100 protein levels are reduced after using arterial line filtration and covalent-bonded heparin to coat the inner surface of the CPB circuit.

Continuing controversy in the management of concomitant coronary and carotid disease: an overview

OBJECTIVES

To perform an analytical overview of the risk factors, pathogenesis of stroke and the strategies for the management of concomitant coronary artery disease and carotid artery stenosis (CAS). Four strategies were analysed; CABG in the presence of CAS, combined (CE+CABG), reverse (CABG+CE<3 months) and prior staged (CE+CABG<3 months).

METHODS

A literature search formed the basis of a reference database. Outcome was assessed by the 30-day permanent stroke and mortality rate for the different approaches. Accrued rates of permanent stroke and mortality rate were expressed in terms of mean stroke and mortality rate (MSR, MMR). Data was analysed comparatively and expressed in terms of P value, odds ratio and confidence limits.

RESULTS

33 different risk factors for stroke at CABG were identified. Significant factors included: ascending aortic atheroma, emergency procedures, impaired left ventricular function, cardioplegia and peripheral vascular disease. Risk of stroke at CABG increased with higher grade CAS (50 vs. 80%, P=0.009). Pathogenesis of stroke at CABG is multifactorial; the role of flow limiting CAS is controversial and other mechanisms are implicated. Analysis of the four strategies revealed that in the Prior Stage (n=573) the MSR was 1.5% and MMR 5.9%, in the Unprotected CABG+CAS series the MSR was 3.8% (n=840) and MMR (n=596) 4.4%, in the Reverse stage series (n=83) the MSR was 2.4%, and MMR 4.8%. For Combined procedures (n=3,295) the MSR was 3.9% and MMR 4.5%. Comparative analysis indicated a significant reduction in stroke for Prior vs. Combined (1.5 vs. 3.9%, P=0.007, odds 0.39, CI 0.2-0.77) with a higher mortality (5.9 vs. 4.5%, P=0.1, odds 1.41, Cl 0.96-2.06, NS). The stroke rate in the Prior stage also remained significantly lower compared to the Unprotected CABG group both mixed (P=0.015) and asymptomatic CAS (P=0.047). When total risks (MSR+MMR), were analysed, similar results were found between the groups; Prior 7.4%, Reverse stage 7.2%, Combined 8.4%, Unprotected CABG+ >50% CAS 11.5%.

CONCLUSIONS

Stroke at CABG is due to multiple risk factors, one of which is high-grade carotid stenosis. Pathophysiology of stroke, although multifactorial, supports embolism rather than flow limitation as the primary mechanism. Lack of randomised trials has made it impossible to draw firm conclusions regarding the best management strategy. There was no significant difference in the overall stroke and mortality risk between the various strategies, however, subgroup analysis suggests that, when carefully selected, patients do better by staging the operations. In our opinion patients without severe cardiac disease should be considered for Prior staging and the rest for Combined procedure. The role of reverse staging needs further evaluation.

An in vitro evaluation of a new cannula tip design compared with two clinically established cannula-tip designs regarding aortic arch vessel perfusion characteristics

We investigated in vitro aortic arch vessel perfusion characteristics of single and multiple jet-stream cannulae and a new dispersion stream tip aortic cannula. Pressures and flows of all arch vessels were measured while directing cannulae jets at the different arch vessels using 6 l/min pump flow. The highest increase in pressure above the set systemic level of 80 mmHg and increase in flow above the set normal flow distribution in the arch vessels occurred in the jet-streamed arch vessels with the single stream cannula. The values were as follows: 29 mmHg and 118 ml/min for the innominate artery, 28 mmHg and 42 ml/min for the left common carotid artery, and 25 mmHg and 54 ml/min for the left subclavian artery. The dispersion stream cannula showed increases in pressure and flow, followed by the multiple stream cannula. Aortic cannula tips and the orientation of jets are potential sources of imbalances of arch vessel perfusion with possible clinical implications regarding perfusion of arch vessels during extracorporeal circulation.

Minimally Invasive Cardiac Surgery: Impact on Resource Usage, Costs, Length of Stay, and Return to Function

"Minimally invasive" approaches to coronary artery surgery include a number of procedures, most of which avoid the use of extracorporeal circulation. Economic considerations have contributed to the rising interest in these techniques. This article reviews current literature and potential ways in which these procedures may reduce overall costs. Several studies have reported decreased mean length of stay and overall hospital costs in patients undergoing off-bypass or "beating heart" procedures. Most of these studies have included small numbers of patients and have lacked long-term follow-up data. Prospective randomized trials are needed to conclusively establish these early findings. Copyright© 1999 by W. B. Saunders Company.

Bilateral cerebral emboli monitoring during extracorporeal circulation

Microembolism generated during extracorporeal circulation is thought to be responsible for stroke and neuropsychological deficits. Before one can investigate the pathogenetic role in more detail, reproducible and reliable quantitative methods need to be developed. In several previous studies, microemboli detection was performed unilaterally. We questioned if this reflects the bihemispheric embolic load. In 42 patients undergoing coronary artery bypass grafting, bilateral embolus detection was performed during extracorporeal circulation. The side-to-side correlation of microembolus counts was strong (0.91), but there was a significant difference in number (p < 0.01) comparing left and right emboli. The side of higher embolus counts cannot be predicted in the individual because either side may show higher counts. Doubling the unilateral count may deviate from the bilateral count by as much as 51% in the individual patient. The total embolic load to the brain during extracorporeal circulation cannot be precisely predicted from unilateral transcranial insonation alone.

Cardiovascular surgery in the elderly

The elderly segment of the population is increasing rapidly, and surgeons are more frequently being requested to operate on this group of patients. A number of reports suggest that elderly patients have a significantly higher incidence of operative mortality and 30-day hospital mortality as compared with younger patients. Elderly patients also had a significantly higher increased incidence of complications, such as renal failure, prolonged ventilation, and incidence of strokes and postoperative cardiac arrest. Regarding coronary artery disease, elderly patients are more acutely sick on admission, are more likely to have triple-vessel disease, more likely have comorbid disease, and are usually less likely to receive an internal mammary artery graft. The presence of valvular disorders with concomitant coronary disease (especially mitral ischemic related valve disease) increases operative time, morbidity, and mortality. Efforts must continue to be made to gather data on outcomes of cardiac surgery in the elderly. Consideration must be given to modify the operative approach that minimizes cardiopulmonary bypass time, mitigates the multisystem organ injury associated with cardiopulmonary bypass, and decreases the likelihood of embolization from the ascending aorta. Future efforts must be made to develop measures to decrease the complications rate identified in elderly patients.

Carotid disease in patients scheduled for coronary artery bypass: analysis of 678 patients

The purpose of this article is to investigate the frequency of carotid disease and to identify high-risk groups among patients scheduled for isolated coronary artery bypass grafting (CABG) procedures under nonemergent conditions. A total of 678 consecutive patients underwent preoperative carotid artery duplex scanning (CADS) before CABG procedures. Morphology of carotid artery was determined and five groups were formed. Age, sex, cervical bruit, diabetes mellitus (DM), hypertension, smoking, history of cerebrovascular event (CVE), peripheral vascular disease (PVD), and severity of coronary artery disease were investigated to describe the high-risk group for carotid artery disease. In 41% of patients carotid examination produced normal findings; 46.2% had less than 60% luminal stenoses, 7.1% had 60-79% stenoses, 4.6% had 80-99% stenoses, and 1.2% had total occlusion. Previous cerebral ischemic events (CVE) (p<0.05), hypertension (p < 0.01), smoking (p < 0.01), advanced age (p < 0.01), and female sex (p < 0.01) were identified as high-risk factors for carotid artery stenoses. There was a linear association between carotid disease and coronary disease (p < 0.05). Documentation of previous CVE, hypertension, smoking, advanced age, female sex, and severe coronary artery disease may be helpful in identifying patients at high risk for carotid artery stenoses.

A dual-vent left heart deairing technique markedly reduces carotid artery microemboli

BACKGROUND

Cerebral embolization, mainly bubbles, follows aortic declamping in left heart valve operations. Embolization is not prevented by conventional left heart deairing methods. We have validated a "dual-vent" deairing technique, which uses high-flow left ventricular and aortic venting from the working heart into the cardiopulmonary bypass venous line before aortic declamping.

METHODS

After left heart valve replacement, intraoperative color-flow Doppler echocardiography was used to monitor the right common carotid embolic activity in 58 consecutive patients who underwent conventional deairing (group 1), 14 consecutive patients who underwent deairing by the dual-vent technique (group 2), and 4 patients who received nonvented coronary artery bypass grafting who did not require deairing (group 3).

RESULTS

The median emboli count recorded after aortic declamping was 1,647 (range, 342 to 6,852) and 101 (range, 0 to 865) in the group 1 and 2 patients, respectively (p < 0.0001). The efficacy of the dual-vent technique improved throughout the series: in the last 7 patients, the emboli counts often approached the very low levels seen in group 3 patients (median, 8; range, 1 to 16).

CONCLUSIONS

Cerebral embolization after aortic declamping in left heart valve operations was significantly reduced by this dual-vent deairing technique.

Effect of aortic cannula characteristics and blood velocity on transcranial doppler-detected microemboli during cardiopulmonary bypass

OBJECTIVES

Cerebral microemboli are responsible to a large extent for the neuropsychiatric deficits after cardiac surgery. Differences in cannula size during cardiopulmonary bypass (CPB) will result in different velocities of blood exiting the aortic cannula. This study determined whether the number of transcranial Doppler (TCD)-detected emboli in the middle cerebral artery (MCA) during CPB correlated with blood speed or the direction of flow as determined by the shape of the aortic cannula.

DESIGN

Patients were studied prospectively for evidence of TCD-detected emboli. If patients met the inclusion criteria, the choice of cannula was determined by surgical preference.

SETTING

All studies were conducted at a single tertiary care academic cardiac surgery hospital by a single observer.

PARTICIPANTS

Thirty-two patients undergoing first-time elective aortocoronary bypass surgery who were free of neurologic dysfunction or peripheral vascular disease and weighed 60 to 85 kg were studied. Patients who had other concurrent cardiac operations or who were in cardiogenic shock were excluded.

INTERVENTIONS

Three aortic cannula types for elective aortocoronary bypass surgery were used: 24F curved (n = 19), 24F straight (n = 6), and 22F straight (n = 7), with internal diameters (IDs) of 7.2, 6.6, and 5.9 mm, respectively. TCD-detected emboli were identified in the MCA.

MEASUREMENTS AND MAIN RESULTS

The rate of TCD-detected emboli (0.02 to 11.4 emboli per minute) was not related to the velocity of blood (46 to 77 cm/s) and was not affected by the choice of either a straight or curved aortic cannula.

CONCLUSIONS

The choice of a straight or curved aortic cannula or of a 24F versus 22F cannula may not be important with respect to the number of cerebral microemboli.

Cerebral complications after coronary artery bypass and heart valve surgery: risk factors and onset of symptoms

OBJECTIVES

Cerebral complications continue to be a major cause of morbidity after cardiac surgery. Earlier studies have mainly focused on intraoperative events, but symptoms may also occur later in the postoperative period. The purpose of this study was to determine the incidence and risk factors of focal neurologic complications and timing of cerebral symptoms.

DESIGN

A retrospective study.

SETTING

Linköping University Hospital.

PARTICIPANTS

Two thousand four hundred eighty patients who underwent cardiac surgery from 1992 to 1995.

INTERVENTIONS

Standard cardiopulmonary bypass (CPB) technique was used in all patients. Anticoagulant treatment included heparin and patients with coronary artery surgery were also administered acetylsalicylic acid and valve-surgery patients received warfarin or dicumarol.

MEASUREMENTS AND MAIN RESULTS

Seventy-five patients (3%) had focal neurologic deficits and/or confusion postoperatively. In 32 patients (43%), the onset was not intraoperative but occurred later in the postoperative period. The lowest incidence of cerebral complications was found in patients who underwent single-valve replacement (1.2%) and the highest incidence was found in patients who underwent combined procedures (valve and coronary artery surgery; 7.6%). Patients greater than 70 years of age had a complication rate of 4.1% compared with 2.5% in patients aged 70 years and less (p < 0.05). The incidence of diabetes mellitus was 11.4% in the entire series, but was more common (18.7%; p < 0.05) in patients with cerebral symptoms. Also, 5.9% of all patients had a history of cerebrovascular disease compared with 14.7% (p < 0.01) of patients with cerebral complications.

CONCLUSION

Cerebral complications may be delayed after cardiac surgery, suggesting causes of cerebral damage other than intraoperative events. Valve-surgery patients had the lowest incidence and patients with combined procedures had the highest incidence of cerebral complications. Advanced age, diabetes mellitus, and preexisting cerebrovascular disease increased the risk.

Synergistic sedation with propofol and midazolam in intensive care patients after coronary artery bypass grafting

OBJECTIVES

To evaluate and compare the clinical efficacy, impact on hemodynamics, safety profiles, and cost of combined administration of propofol and midazolam (synergistic sedation) vs. midazolam and propofol administered as sole agents, for sedation of mechanically ventilated patients after coronary artery bypass grafting.

DESIGN

Prospective, controlled, randomized, double-blind clinical trial.

SETTING

Intensive care unit of SCIAS-Hospital de Barcelona.

PATIENTS

Seventy-five mechanically ventilated patients who underwent coronary artery bypass graft surgery under low-dose opioid anesthesia.

INTERVENTIONS

According to the double-blind method, patients were randomly assigned to receive propofol (n = 25), midazolam (n = 25), or propofol combined with midazolam (n = 25). Infusion rates were adjusted to stay between 8 and 11 points on Glasgow Coma Score modified by Cook and Palma.

MEASUREMENTS AND MAIN RESULTS

Mean +/- SD duration of sedation was 14.4 +/- 1.5 hrs, 14.1 +/- 1.1 hrs, and 14.7 +/- 1.9 hrs for the propofol, midazolam, and synergistic groups, respectively. The induction dose was 0.55 +/- 0.05 mg/kg for propofol as sole agent, 0.05 +/- 0.01 mg/kg for midazolam as sole agent, and 0.22 +/- 0.03 mg/kg for propofol administered in combination with 0.02 +/- 0.00 mg/kg of midazolam (p = .001). The maintenance dose was 1.20 +/- 0.03 mg/kg/hr for propofol as sole agent, 0.08 +/- 0.01 mg/kg/hr for midazolam as sole agent, and 0.50 +/- 0.09 mg/kg/hr for propofol administered in combination with 0.03 +/- 0.01 mg/kg/hr of midazolam (p < .001). All sedative regimens achieved similar efficacy in percentage of hours of adequate sedation (93% for propofol, 88% for midazolam, and 90% for the synergistic group, respectively). After induction, both propofol and midazolam groups had significant decreases in systolic blood pressure, diastolic blood pressure, left atrial pressure, and heart rate. Patients in the synergistic group had significant bradycardia throughout the study, without impairment in other hemodynamic parameters. Patients sedated with propofol or synergistic regimen awoke sooner and could be extubated before those patients sedated with midazolam (0.9 +/- 0.3 hrs and 1.2 +/- 0.6 hrs vs. 2.3 +/- 0.8 hrs, respectively, p = .01). Synergistic sedation produced cost savings of 28% with respect to midazolam and 68% with respect to propofol.

CONCLUSIONS

In the study conditions, the new synergistic treatment with propofol and midazolam administered together is an effective and safe alternative for sedation, with some advantages over the conventional regimen with propofol or midazolam administered as sole agents, such as absence of hemodynamic impairment, >68% reduction in maintenance dose, and lower pharmaceutical cost.

Minimally invasive port-access mitral valve surgery

OBJECTIVES

This study evaluates the feasibility of video-assisted minimally invasive mitral valve surgery by means of the Port-Access system. The aim of the study was to minimize surgical access and to develop a video-assisted surgical technique.

METHODS

The Port-Access system allows for closed chest endoluminal aortic clamping, cardioplegic arrest, and decompression of the heart. The mitral valve was either repaired (n = 28) or replaced (n = 23) in 51 patients by means of a minimally invasive approach through a right lateral minithoracotomy and under videoscopic guidance.

RESULTS

Mean length of incision was 5.4 +/- 1.8 cm (range 3.8 to 8 cm). Mean duration of operation, cardiopulmonary bypass, and crossclamp time was 196 +/- 53, 133 +/- 52, and 72 +/- 27 minutes, respectively. Median intubation time was 25.5 hours (range 5 to 264 hours). Median duration of intensive care and hospital stay was 2 days (range 1 to 36 days) and 13 days (10 to 36 days), respectively. Hospital mortality was 9.8% (5/51). Overall morbidity was relatively high. In two patients acute retrograde aortic dissection led to conversion of the procedure. At follow-up (261 +/- 13 days), three patients required reoperation for paravalvular leakage. Baseline mean Duke activity index score was 19.3 +/- 11.3 before the operation and increased to 23.2 +/- 10 at 6 weeks' and 24.2 +/- 10.3 at 12 weeks' follow-up, respectively.

CONCLUSION

The Port-Access system allows for video-assisted minimally invasive replacement and complex repair of the mitral valve through a right lateral minithoracotomy. However, morbidity and mortality associated with this novel technique were high.

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

BACKGROUND AND PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

What is 'minimally invasive' coronary bypass surgery? Experience with a variety of surgical revascularization procedures for single-vessel disease

BACKGROUND

Although the use of small incisions is theoretically appealing, it has been argued that the true advantage of minimally invasive approaches to myocardial revascularization lies in the avoidance of cardiopulmonary bypass.

METHODS

Of 25 patients referred for surgical revascularization of single-vessel coronary disease, 20 elected to undergo a minimally invasive coronary artery bypass grafting (MICABG) procedure, while 5 opted to have conventional surgery with cardiopulmonary bypass (CPB). Patients having MICABG underwent single-vessel revascularization without CPB, via limited anterior thoracotomy, hemisternotomy, or median sternotomy. Intraoperatively, hemodynamics, anastomotic time, and total operative time were recorded. Postoperatively, length of hospital stay, incidence of myocardial infarction, indexes of end-organ function, and morbidity rates were recorded. In addition, patient questionnaires were used to assess subjective end points such as postoperative pain, wound drainage, and quality of life.

RESULTS

Fifteen of 20 patients undergoing MICABG underwent revascularization without CPB, while 4 were converted to standard coronary artery bypass grafting with CPB due to technical reasons and 1 for intraoperative ventricular fibrillation. Patients undergoing MICABG had no perioperative myocardial infarctions, while those having CPB had two infarctions (20%). Furthermore, there were no differences in length of stay or postoperative morbidity among the various approaches, while the MICABG procedures, especially via median sternotomy, were associated with shorter operative times.

CONCLUSIONS

The advantage of MICABG lies mainly in the avoidance of CPB. Thus, we advocate that surgeons initially utilize the median sternotomy and limited skin incision for MICABG to assure adequate exposure, technical precision, and patient safety. After a reasonable level of technical proficiency and experience are attained, the limited anterior thoracotomy approach can be used.

Subglottic stenosis complicating cardiac surgery in children

OBJECTIVE

To highlight the incidence of subglottic stenosis (SGS) as a complication of surgery for congenital heart disease and the role of single-stage laryngotracheoplasty in treating this complication.

DESIGN

Retrospective case series.

SETTING

University-based referral center specializing in surgery for congenital heart disease and complex airway problem management.

INTERVENTION

Laryngotracheal reconstruction (LTR).

MAIN OUTCOME MEASURE

Successful airway expansion.

RESULTS

At last follow-up, 87.5% (7 of 8) of patients remain free of obstructive airway symptoms.

CONCLUSION

SGS can complicate surgery for congenital heart disease in children. Single-stage LTR is an effective treatment modality for this problem.

Minimally invasive coronary artery bypass grafting decreases hospital stay and cost

OBJECTIVE

The authors performed a retrospective cost analysis for patients undergoing revascularization of their left anterior descending (LAD) coronary artery either by standard coronary artery bypass grafting (CABG), percutaneous transluminal coronary angioplasty (PTCA), or minimally invasive coronary artery bypass grafting (MICABG).

SUMMARY BACKGROUND DATA

Minimally invasive CABG has become a safe and effective alternative treatment for single-vessel coronary artery disease. However, the acceptance of this procedure as a routine alternative for the treatment of coronary artery disease will depend on both long-term graft patency rates as well as a competitive market cost.

METHODS

The authors conducted a retrospective analysis of three patient groups undergoing LAD coronary revascularization from January 1995 to July 1996. Ten patients were selected randomly from this period after PTCA of an LAD lesion with or without stenting. Nine patients underwent standard CABG on cardiopulmonary bypass with a left internal mammary artery. Nine patients received MICABG via a limited left anterior thoracotomy and left internal mammary artery to LAD grafting without the use of cardiopulmonary bypass.

RESULTS

Percutaneous transluminal coronary angioplasty (n = 10) was unsuccessful in two patients. One patient in the MICABG group (n = 9) was converted successfully to conventional CABG because of an intramyocardial LAD and dilated left ventricle. There was no operative morbidity or mortality in any group. Average length of stay postprocedure was decreased significantly for both the MICABG and PTCA groups when compared with that of conventional CABG (n = 9) (2.7 + 0.26, p = 0.009, and 2.6 + 0.54, p = 0.006, vs. 4.8 + 0.46, respectively). Total hospital costs for the MICABG and PTCA groups were significantly less when compared with those of standard CABG ($10,129 + 1104, p = 0.0028, and $9113 + 3,039, p = 0.0001, vs. $17,816 + 1043, respectively). There were no statistically significant differences between the MICABG and PTCA groups.

CONCLUSIONS

The final role of minimally invasive CABG is unclear. This procedure is clearly cost effective when compared with that of PTCA and conventional CABG. The long-term patency rates for MICABG will determine its overall efficacy.

Neurological outcome in a porcine model of descending thoracic aortic surgery. Left atrial-femoral artery bypass versus clamp/repair

BACKGROUND AND PURPOSE

In a porcine model of thoracic aortic cross-clamping (AoXC), we compared the incidence and severity of paraplegia with two surgical techniques: left atrial-femoral artery (LA-FA) bypass (BP group; n = 9) and clamp/repair (CR group; n = 8). The descending thoracic aorta was clamped near its origin and distal to the third intercostal artery for 30 minutes. The intervening three intercostal arteries were ligated and divided.

METHODS

All animals received methohexital anesthesia and were hyperventilated to a Paco2 of 28 to 32 mm Hg. Animals in the CR group received mannitol, and after AoXC, proximal hypertension was controlled with phlebotomy. In the BP group, proximal hypertension was controlled with LA-FA bypass using a centrifugal pump (Biomedicus 520C). Proximal mean arterial pressure, distal mean arterial pressure, central venous pressure, and cerebrospinal fluid pressure were measured; radioactive microspheres were injected at baseline, at AoXC + 5 minutes, at AoXC + 20 minutes, at AoXC off + 5 minutes, and after resuscitation. Neurological function was assessed at 24 hours. The animals were killed, and the spinal cord was removed to determine spinal cord blood flow. Histological cross sections of the lumbar spinal cord were stained with cresyl violet/acid fuchsin and then examined with light microscopy to determine the ratio of altered to total spinal cord neurons.

RESULTS

Fifteen animals survived (one death in each group) and were assessed neurologically at 24 hours after AoXC. Despite better distal perfusion and lumbar spinal cord blood flow in the BP group, during AoXC, and at AoXC off + 5 minutes, there was no significant difference in the severity of spinal cord ischemic injury between groups as assessed neurologically by Tarlov score (P = .90, Mann-Whitney U test). As well, the ratio of altered to total lumbar spinal cord neurons did not differ between groups (P = .24).

CONCLUSIONS

In this chronic porcine model, distal circulatory support with LA-FA bypass afforded better distal perfusion and improved lumbar spinal cord blood flow but did not influence the severity of spinal cord ischemic injury when compared with a clamp/repair technique.

Cerebral blood flow in the diabetic patient

Diabetes is a major risk factor for cardiovascular disease. Coronary revascularization utilizing cardiopulmonary bypass (CPB) is frequently required for the diabetic patient. Nondiabetic individuals can autoregulate cerebral blood flow (CBF) through metabolic and perfusion pressure mechanisms during CPB. However, it has been reported that diabetic patients have impaired CBF autoregulation during CPB. It is possible, therefore, that impaired CBF autoregulation may contribute to postoperative neuropsychologic dysfunction. The mechanisms for this defect may reside in impaired endothelial-dependent responses in the diabetic that are related to morphological and functional changes linking the vascular endothelium and the vascular smooth muscle. The morphological changes occurring in the diabetic include microangiopathy and macroangiopathy which are characterized by endothelial cell (EC) hyperplasia and basement membrane thickening. Also, significant functional changes in local control of vascular tone, such as an imbalance in the synthesis and secretion of vasoactive factors by the EC and abnormal reactivity of the vascular smooth muscle, are seen in the diabetic when compared to the nondiabetic. More specifically, vascular responses to both calcium-dependent pathways of vasoconstriction and nitric oxide pathways of vasorelaxation have been shown to significantly differ between the diabetic and nondiabetic. The emphasis of this discussion is to examine the molecular mechanisms by which diabetes alters vascular function, with emphasis placed on regulation of cerebral artery blood flow during CPB.

The role of neuromonitoring in cardiovascular surgery

This review describes the techniques currently used for quantitative neurophysiologic measurement during cardiac surgery and their potential impact on clinical outcome. Electroencephalography (EEG) characterizes cerebrocortical neuronal electrical activity and was part of some of the earliest cardiopulmonary bypass procedures, yet today it is not widespread use. Each of the common misunderstandings regarding a supposed limitation of this technology is explained. Its major genuine shortcoming, a lack of selectivity, may now be overcome with the combined use of additional monitoring modalities. The influence of intracranial hemodynamics on observed EEG changes may be determined continuously and noninvasively with transcranial Doppler (TCD) ultrasound. TCD provides an indication of sudden change in either blood flow or vascular resistance as well as the detection of emboli. In addition, the metabolic status of cortical neurons can be monitored by regional cerebral venous oxygen saturation (rCVOS) using noninvasive transcranial near-infrared spectroscopy. The % rCVOS tends to remain remarkably stable over a wide range of temperatures, perfusion pressures, and anesthetic states. Marked change in either direction signifies a serious imbalance between oxygen delivery and consumption. Measurement of rCVOS does not require blood flow, pulsatile or otherwise, so that it offers the only means of monitoring during circulatory arrest. By characterizing the dynamic interplay among cerebral hemodynamics, metabolism, and electrogenesis, these technologies permit the rapid detection and correction of potentially hazardous conditions.