Improvement of outcomes after coronary artery bypass. A randomized trial comparing intraoperative high versus low mean arterial pressure

Stroke associated with coronary artery bypass grafting

While coronary artery bypass grafting (CABG) has been playing a significant role in the revascularization for ischemic heart disease, neurological complications associated with CABG have been a primary concern. Stroke, although the incidence is low, is one of the most devastating complication of CABG. Many studies have identified the risk factors for stroke with CABG, such as prior stroke, carotid artery stenosis, aortic atherosclerosis, atrial fibrillation and cardiopulmonary bypass. Various rational approaches focusing on individual risk factor have been proposed for the stroke. Prophylactic carotid revascularization is an important strategy, and the diagnosis of carotid stenosis has to be established correctly. Prevention of emboli from aortic plaque is also an essential issue. Intraoperative monitoring with transesophageal or epiaortic ultrasound is useful to identify mobile atheromatous plaques and to select appropriate aortic manipulations. Maintenance of cerebral blood flow and blood pressure during cardiopulmonary bypass might be critical issues. Besides, there are conflicting two opinions regarding off-pump CABG; one supports an efficiency for the prevention of stroke while the other advocates no effect. This discrepancy might be explained by the difference of the risk of stroke in the population of the individual study and by the variation of the percentage of aortic clamping or aortic anastomosis in each study. Pharmaceutical therapies such as statin, preventive medication for atrial fibrillation, or antiplatelet are promising methods. Although it is hard to decrease the incidence of the stroke with any single countermeasure, sustained effort should be continued to overcome the stroke associated with CABG.

Hemoglobin Concentration Affects Electroencephalogram During Cardiopulmonary Bypass: An Indication for Neuro-Protective Values

Hemodilution during cardiopulmonary bypass (CPB) is widely used to decrease transfusion and improve microcirculation but has drawbacks, such as diminished hemoglobin levels. Among others, reduced brain oxygenation accounts for neurological adverse outcomes after CPB. The aim of the present study was to ascertain if and how continuous electroencephalogram (EEG) during CPB is affected by hematocrit level and what should be the minimum value to avoid significant frequency band shifts on the EEG. A comparative study design was used with 16 subjects undergoing elective mitral valve repair/replacement. EEG was continuously recorded during the surgical procedure (from anesthesia induction to 20 min after CPB end). Data were marked at relevant time points (T0: before CPB start; T1: after 30 min from CPB beginning; T2: at CPB end), and the following 2 min EEG analyzed with a fast Fourier transform to obtain relative power for delta, theta, alpha, and beta bands. A general linear model for repeated measure was used to study interactions of time (T0, T1, and T2, EEG frequency band, and topographical distribution. The relative powers for each electrode were calculated and represented using topographic maps. Power spectrum differences between time points (T2-T1; T2-T0; T1-T0) were calculated for each electrode, and differences >10%, considered indicative of neuronal sufferance, were included in further analysis. Cutoff hemoglobin values that maximize the proportion of correctly classified EEG band shifts were obtained by previous definition were obtained. At T2, diffuse EEG slowing in delta and theta bands was detected; a minor slowing over anterior regions was evident at T1 for the theta band. Decrements in EEG power greater than 10% were detected only for the delta band at T2. Hemoglobin concentration levels at which no slowing increase was evident were 9.4 mg/dL (Ht: 28.2%) at T1 and 9.2 mg/dL (Ht: 27.6%) at T2. EEG burst-suppression pattern related to a lesser degree of slowing at T2. In conclusion, we propose hemoglobin cutoff levels that prevent EEG slowing indicative of neuronal sufferance. In addition, burst-suppression EEG patterns offer higher central nervous system protection as measured on EEG.

The Charlson comorbidity index can be used prospectively to identify patients who will incur high future costs

Background

Reducing health care costs requires the ability to identify patients most likely to incur high costs. Our objective was to evaluate the ability of the Charlson comorbidity score to predict the individuals who would incur high costs in the subsequent year and to contrast its predictive ability with other commonly used predictors.

Methods

We contrasted the prior year Charlson comorbidity index, costs, Diagnostic Cost Group (DCG) and hospitalization as predictors of subsequent year costs from claims data of fund that provides comprehensive health benefits to a large union of health care workers. Total costs in the subsequent year was the principal outcome.

Results

Of the 181,764 predominantly Black and Latino beneficiaries, 70% were adults (mean age 45.7 years; 62% women). As the comorbidity index increased, total yearly costs increased significantly (P<.001). At lower comorbidity, the costs were similar across different chronic diseases. Using regression to predict total costs, top 5^th and 10^th percentile of costs, the comorbidity index, prior costs and DCG achieved almost identical explained variance in both adults and children.

Conclusions and Relevance

The comorbidity index predicted health costs in the subsequent year, performing as well as prior cost and DCG in identifying those in the top 5% or 10%. The comorbidity index can be used prospectively to identify patients who are likely to incur high costs.

Trial Registration

ClinicalTrials.gov NCT01761253

AKI associated with cardiac surgery

Approximately 18% of patients undergoing cardiac surgery experience AKI (on the basis of modern standardized definitions of AKI), and approximately 2%-6% will require hemodialysis. The development of AKI after cardiac surgery portends poor short- and long-term prognoses, with those developing RIFLE failure or AKI Network stage III having an almost 2-fold increase in the risk of death. AKI is caused by a variety of factors, including nephrotoxins, hypoxia, mechanical trauma, inflammation, cardiopulmonary bypass, and hemodynamic instability, and it may be affected by the clinician's choice of fluids and vasoactive agents as well as the transfusion strategy used. The risk of AKI may be ameliorated by avoidance of nephrotoxins, achievement of adequate glucose control preoperatively, and use of goal-directed therapy hemodynamic strategies. Remote ischemic preconditioning is an exciting future strategy, but more work is needed before widespread implementation. Unfortunately, there are no pharmacologic agents known to reduce the risk of AKI or treat established AKI.

Arterial pressure above the upper cerebral autoregulation limit during cardiopulmonary bypass is associated with postoperative delirium

BACKGROUND

Mean arterial pressure (MAP) below the lower limit of cerebral autoregulation during cardiopulmonary bypass (CPB) is associated with complications after cardiac surgery. However, simply raising empiric MAP targets during CPB might result in MAP above the upper limit of autoregulation (ULA), causing cerebral hyperperfusion in some patients and predisposing them to cerebral dysfunction after surgery. We hypothesized that MAP above an ULA during CPB is associated with postoperative delirium.

METHODS

Autoregulation during CPB was monitored continuously in 491 patients with the cerebral oximetry index (COx) in this prospective observational study. COx represents Pearson's correlation coefficient between low-frequency changes in regional cerebral oxygen saturation (measured with near-infrared spectroscopy) and MAP. Delirium was defined throughout the postoperative hospitalization based on clinical detection with prospectively defined methods.

RESULTS

Delirium was observed in 45 (9.2%) patients. Mechanical ventilation for >48 h [odds ratio (OR), 3.94; 95% confidence interval (CI), 1.72-9.03], preoperative antidepressant use (OR, 3.0; 95% CI, 1.29-6.96), prior stroke (OR, 2.79; 95% CI, 1.12-6.96), congestive heart failure (OR, 2.68; 95% CI, 1.28-5.62), the product of the magnitude and duration of MAP above an ULA (mm Hg h; OR, 1.09; 95% CI, 1.03-1.15), and age (per year of age; OR, 1.01; 95% CI, 1.01-1.07) were independently associated with postoperative delirium.

CONCLUSIONS

Excursions of MAP above the upper limit of cerebral autoregulation during CPB are associated with risk for delirium. Optimizing MAP during CPB to remain within the cerebral autoregulation range might reduce risk of delirium.

CLINICAL TRIAL REGISTRATION

clinicaltrials.gov NCT00769691 and NCT00981474.

Nocturnal systemic hypotension increases the risk of glaucoma progression

OBJECTIVE

The objective of this prospective, longitudinal study of patients with normal-tension glaucoma (NTG) was to determine whether patients with nocturnal hypotension are at greater risk for visual field (VF) loss over 12 months than those without nocturnal hypotension.

DESIGN

Prospective, longitudinal study.

PARTICIPANTS

Consecutive patients with NTG with at least 5 prior VF tests were screened for eligibility.

METHODS

The baseline evaluation assessed demographic and clinical characteristics, covering systemic comorbid conditions, including systemic hypertension. All oral and ophthalmologic medications were recorded. A complete ophthalmological examination was performed at baseline and follow-up. Patients had their blood pressure (BP) monitored every 30 minutes for 48 hours with an ambulatory recording device at baseline and 6 and 12 months.

MAIN OUTCOME MEASURES

The primary outcome was based on the global rates of VF progression by linear regression of the mean VF threshold sensitivity over time (decibels/year).

RESULTS

Eighty-five patients with NTG (166 eyes; mean age, 65 years; 67% were women) were included. Of the 85 patients, 29% had progressed in the 5 VFs collected before study enrollment. The nocturnal mean arterial pressure (MAP) was compared with the daytime MAP. Multivariate analysis showed that the total time that sleep MAP was 10 mmHg below the daytime MAP was a significant predictor of subsequent VF progression (P<0.02).

CONCLUSIONS

Cumulative nocturnal hypotension predicted VF loss in this cohort. Our data suggest that the duration and magnitude of decrease in nocturnal blood pressure below the daytime MAP, especially pressures that are 10 mmHg lower than daytime MAP, predict progression of NTG. Low nocturnal blood pressure, whether occurring spontaneously or as a result of medications, may lead to worsening of VF defects.

Neurological complications of cardiac surgery

As increasing numbers of elderly people undergo cardiac surgery, neurologists are frequently called upon to assess patients with neurological complications from the procedure. Some complications mandate acute intervention, whereas others need longer term observation and management. A large amount of published literature exists about these complications and guidance on best practice is constantly changing. Similarly, despite technological advances in surgical intervention and modifications in surgical technique to make cardiac procedures safer, these advances often create new avenues for neurological injury. Accordingly, rapid and precise neurological assessment and therapeutic intervention rests on a solid understanding of the evidence base and procedural variables.

Stroke after aortic valve surgery: results from a prospective cohort

BACKGROUND

The incidence and impact of clinical stroke and silent radiographic cerebral infarction complicating open surgical aortic valve replacement (AVR) are poorly characterized.

METHODS AND RESULTS

We performed a prospective cohort study of subjects ≥65 years of age who were undergoing AVR for calcific aortic stenosis. Subjects were evaluated by neurologists preoperatively and postoperatively and underwent postoperative magnetic resonance imaging. Over a 4-year period, 196 subjects were enrolled at 2 sites (mean age, 75.8±6.2 years; 36% women; 6% nonwhite). Clinical strokes were detected in 17%, transient ischemic attack in 2%, and in-hospital mortality was 5%. The frequency of stroke in the Society for Thoracic Surgery database in this cohort was 7%. Most strokes were mild; the median National Institutes of Health Stroke Scale was 3 (interquartile range, 1-9). Clinical stroke was associated with increased length of stay (median, 12 versus 10 days; P=0.02). Moderate or severe stroke (National Institutes of Health Stroke Scale ≥10) occurred in 8 (4%) and was strongly associated with in-hospital mortality (38% versus 4%; P=0.005). Of the 109 stroke-free subjects with postoperative magnetic resonance imaging, silent infarct was identified in 59 (54%). Silent infarct was not associated with in-hospital mortality or increased length of stay.

CONCLUSIONS

Clinical stroke after AVR was more common than reported previously, more than double for this same cohort in the Society for Thoracic Surgery database, and silent cerebral infarctions were detected in more than half of the patients undergoing AVR. Clinical stroke complicating AVR is associated with increased length of stay and mortality.

Increasing mean arterial pressure during cardiac surgery does not reduce the rate of postoperative acute kidney injury

Introduction:

We hypothesized that the optimization of renal haemodynamics by maintaining a high level of mean arterial blood pressure (MAP) during cardiopulmonary bypass (CPB) could reduce the rate of acute kidney injury (AKI) in high-risk patients.

Methods:

In this randomized, controlled study, we enrolled 300 patients scheduled for elective cardiac surgery under cardiopulmonary bypass. All had known risk factors of AKI: serum creatinine clearance between 30 and 60 ml/min for 1.73m2 or two factors among the following: age >60 years, diabetes mellitus, diffuse atherosclerosis. After a standardized fluid loading, the MAP was maintained between 75-85 mmHg during CPB with norepinephrine (High Pressure, n=147) versus 50-60 mmHg in the Control (n=145). AKI was defined by a 30% increased of serum creatinine (sCr). We further tested others definitions for AKI: RIFLE classification, 50% rise of sCr and the need for haemodialysis.

Results:

The pressure endpoints were achieved in both the High Pressure (79 ± 6 mmHg) and the Control groups (60 ± 6 mmHg; p<0.001). The rate of AKI did not differ by group (17% vs. 17%; p=1), whatever the criteria used for AKI. The length of stay in hospital (9.5 days [7.9-11.2] vs. 8.2 [7.1-9.4]) and the rate of death at day 28 (2.1% vs. 3.4%) and at six months (3.4% vs. 4.8%) did not differ between the groups.

Conclusion:

Maintaining a high level of MAP (on average) during normothermic CPB does not reduce the risk of postoperative AKI. It does not alter the length of hospital stay or the mortality rate.

The association of postcardiac surgery acute kidney injury with intraoperative systolic blood pressure hypotension

Background. Postoperative acute kidney injury (AKI) is associated with high mortality and substantial cost after aortocoronary bypass graft (CABG) surgery. We tested the hypothesis that intraoperative systolic blood pressure variation is associated with postoperative AKI. Methods. We gathered demographic, procedural, blood pressure, and renal outcome data for 7,247 CABG surgeries at a single institution between 1996 and 2005. A development/validation cohort methodology was randomly divided (66% and 33%, resp.). Peak postoperative serum creatinine rise relative to baseline (%ΔCr) was the primary AKI outcome variable. Markers reflective of intraoperative systolic blood pressure variation were derived for each patient including (1) peak and nadir values (absolute and relative to baseline) and (2) excursion episodes beyond selected thresholds (by duration, frequency, and duration × degree). Each marker of systolic blood pressure variation was then separately evaluated for association with AKI using linear regression models with adjustment for several known risk factors (age, aprotinin use, congestive heart failure, previous myocardial infarction, baseline creatinine, bypass time, diabetes, weight, concomitant valve surgery, gender, and preoperative pulse pressure). Results. An association was identified between systolic blood pressure relative to baseline and postoperative AKI (P < 0.006). Conclusions. In CABG surgery patients, intraoperative systolic blood pressure decrease relative to baseline systolic blood pressure is independently associated with postoperative AKI.

Elevated preoperative blood pressure predicts the intraoperative loss of SSEP neuromonitoring signals during spinal surgery

Intraoperative neuromonitoring of somatosensory evoked potentials (SSEPs) can allow identification of evolving neurologic deficit. However, SSEP deterioration is not always associated with postoperative deficit. Transient physiologic changes, including a decrease in blood pressure (BP), can result in signal deterioration, defined as a decrease in waveform amplitude of[50 %seen without neurologic deficit. This study examines the relationship between intraoperative BP decrease and SSEP neuromonitoring to determine whether hypertensive patients are more prone to decreases in BP and if such BP declines are associated with signal loss. We conducted a retrospective review of 43 lumbar laminectomy patients at Mount Sinai. Patients were categorized based on whether they had a previous hypertension diagnosis and if they presented with a first systolic BP of greater than 140 mmHg in the admission area on the morning of surgery, two groups that were not mutually exclusive. We measured BP drop by calculating fractional mean arterial pressure (fMAP, lowest MAP/baseline MAP) and change in BP.We identified patients' SSEP tracings in which signal amplitude decreased[50 %. After dividing patients' recording times into 5-min epochs, we calculated median MAP and whether SSEPs deteriorated in each epoch. We compared the likelihood of signal loss in hypertensives to patients presenting with elevated BP, calculating the odds ratio. Elevated BP prior to surgery is associated with lower fMAP (p = 0.007) and a larger intraoperative decrease in BP (p\0.001).A diagnosis of hypertension is not associated with lower fMAP orBP drop. Lower epoch fMAPis associated with signal loss (p = 0.0026). While the presence of preoperative elevated BP predicts SSEP abnormality (p = 0.0039), a diagnosis of hypertension does not. Elevated BP, not a hypertension diagnosis, is associated with intraoperative loss of SSEP signals. This effect of elevated BP on SSEPs may be due to the larger associated intraoperative BP decline.

Duration and magnitude of blood pressure below cerebral autoregulation threshold during cardiopulmonary bypass is associated with major morbidity and operative mortality

OBJECTIVES

Optimizing blood pressure using near-infrared spectroscopy monitoring has been suggested to ensure organ perfusion during cardiac surgery. Near-infrared spectroscopy is a reliable surrogate for cerebral blood flow in clinical cerebral autoregulation monitoring and might provide an earlier warning of malperfusion than indicators of cerebral ischemia. We hypothesized that blood pressure below the limits of cerebral autoregulation during cardiopulmonary bypass would be associated with major morbidity and operative mortality after cardiac surgery.

METHODS

Autoregulation was monitored during cardiopulmonary bypass in 450 patients undergoing coronary artery bypass grafting and/or valve surgery. A continuous, moving Pearson's correlation coefficient was calculated between the arterial pressure and low-frequency near-infrared spectroscopy signals and displayed continuously during surgery using a laptop computer. The area under the curve of the product of the duration and magnitude of blood pressure below the limits of autoregulation was compared between patients with and without major morbidity (eg, stroke, renal failure, mechanical lung ventilation >48 hours, inotrope use >24 hours, or intra-aortic balloon pump insertion) or operative mortality.

RESULTS

Of the 450 patients, 83 experienced major morbidity or operative mortality. The area under the curve of the product of the duration and magnitude of blood pressure below the limits of autoregulation was independently associated with major morbidity or operative mortality after cardiac surgery (odds ratio, 1.36; 95% confidence interval, 1.08-1.71; P = .008).

CONCLUSIONS

Blood pressure management during cardiopulmonary bypass using physiologic endpoints such as cerebral autoregulation monitoring might provide a method of optimizing organ perfusion and improving patient outcomes from cardiac surgery.

Pulsatile versus non-pulsatile flow to reduce cognitive decline after coronary artery bypass surgery: A randomized prospective clinical trial

BACKGROUND

In this prospective study, we aimed to compare the effect of pulsatile and non-pulsatile flow on the cognitive functions in patients undergoing coronary artery bypass surgery.

METHODS

Patients scheduled for their first coronary artery bypass surgery (n = 148) were randomly assigned to the pulsatile flow group (Group A, n = 75) or non-pulsatil group (Group B, n = 73). Cognitive performance was assessed with (MoCA) montreal cognitive assessment test performed by psychologists before coronary artery bypass surgery and 1 month after the operation.

RESULTS

Mild cognitive impairment was seen in 12 (16%) patients and serious cognitive impairment was seen in 1 (1.33%) patient in the pulsatile flow group. In the other group, mild cognitive impairment was detected in 23 (31.50%) patients and serious cognitive decline was found in 3 (4.10%) patients. Mean MoCA scores were 25.86 ± 2.62 in group A and 22.12 ± 2.20 in group B. The difference between two groups was statistically significant (P = 0.041).

CONCLUSIONS

We suggest that pulsatile flow has beneficial effects to decrease cognitive dysfunction in patients undergoing on-pump coronary artery bypass surgery.

Preoperative hematocrit concentration and the risk of stroke in patients undergoing isolated coronary-artery bypass grafting

Background. Identification and management of risk factors for stroke following isolated coronary artery bypass grafting (CABG) could potentially lower the risk of such serious morbidity. Methods. We retrieved data for 30-day stroke incidence and perioperative variables for patients undergoing isolated CABG and used multivariate logistic regression to assess the adjusted effect of preoperative hematocrit concentration on stroke incidence. Results. In 2,313 patients (mean age 65.9 years, 73.6% men), 43 (1.9%, 95% CI: 1.4–2.5) developed stroke within 30 days following CABG (74.4% within 6 days). After adjustment for a priori defined potential confounders, each 1% drop in preoperative hematocrit concentration was associated with 1.07 (95% CI: 1.01–1.13) increased odds for stroke (men, OR: 1.08, 95% CI: 1.01–1.16; women, OR: 1.02, 95% CI: 0.91–1.16). The predicted probability of stroke for descending preoperative hematocrit concentration exceeded 2% for values <37% (<37% for men (adjusted OR: 2.39, 95% CI: 1.08–5.26) and <38% for women (adjusted OR: 2.52, 95% CI: 0.53–11.98), with a steeper probability increase noted in men). The association between lower preoperative hematocrit concentration and stroke was evident irrespective of intraoperative transfusion use. Conclusion. Screening and management of patients with low preoperative hematocrit concentration may alter postoperative stroke risk in patients undergoing isolated CABG.

Attrition in longitudinal randomized controlled trials: home visits make a difference

Background

Participant attrition in longitudinal studies can introduce systematic bias, favoring participants who return for follow-up, and increase the likelihood that those with complications will be underestimated. Our aim was to examine the effectiveness of home follow-up (Home F/U) to complete the final study evaluation on potentially “lost” participants by: 1) evaluating the impact of including and excluding potentially “lost” participants (e.g., those who required Home F/U to complete the final evaluation) on the rates of study complications; 2) examining the relationship between timing and number of complications on the requirement for subsequent Home F/U; and 3) determining predictors of those who required Home F/U.

Methods

We used data from a randomized controlled trial (RCT) conducted from 1991–1994 among coronary artery bypass graft surgery patients that investigated the effect of High mean arterial pressure (MAP) (intervention) vs. Low MAP (control) during cardiopulmonary bypass on 5 complications: cardiac morbidity/mortality, neurologic morbidity/mortality, all-cause mortality, neurocognitive dysfunction and functional decline. We enhanced completion of the final 6-month evaluation using Home F/U.

Results

Among 248 participants, 61 (25%) required Home F/U and the remaining 187 (75%) received Routine F/U. By employing Home F/U, we detected 11 additional complications at 6 months: 1 major neurologic complication, 6 cases of neurocognitive dysfunction and 4 cases of functional decline. Follow-up of 61 additional Home F/U participants enabled us to reach statistical significance on our main trial outcome. Specifically, the High MAP group had a significantly lower rate of the Combined Trial Outcome compared to the Low MAP group, 16.1% vs. 27.4% (p=0.032). In multivariate analysis, participants who were ≥ 75 years (OR=3.23, 95% CI 1.52-6.88, p=0.002) or on baseline diuretic therapy (OR=2.44, 95% CI 1.14-5.21, p=0.02) were more likely to require Home F/U. In addition, those in the Home F/U group were more likely to have sustained 2 or more complications (p=0.05).

Conclusions

Home visits are an effective approach to reduce attrition and improve accuracy of study outcome reporting. Trial results may be influenced by this method of reducing attrition. Older participants, those with greater medical burden and those who sustain multiple complications are at higher risk for attrition.

Response of mean arterial pressure to temporary biventricular pacing after chest closure during cardiac surgery

OBJECTIVES

We have previously demonstrated that biventricular pacing increased cardiac output within 1 hour of weaning from cardiopulmonary bypass in selected patients. To assess the possible sustained benefit, we reviewed in the present study the effects of biventricular pacing on the mean arterial pressure after chest closure.

METHODS

A total of 30 patients (mean ejection fraction 35% ± 15%, mean QRS 119 ± 24 ms) underwent coronary bypass and/or valve surgery. The mean arterial pressure was maximized during biventricular pacing using atrioventricular delays of 90 to 270 ms and interventricular delays of +80 to -80 ms during 20-second intervals in random sequence. Optimized biventricular pacing was finally compared with atrial pacing at a matched heart rate and to a sinus rhythm during 30-second intervals. Vasoactive medication and fluid infusion rates were held constant. The arterial pressure was digitized, recorded, and integrated. Statistical significance was assessed using linear mixed effects models and Bonferroni's correction.

RESULTS

Optimized atrioventricular delay, ranging from 90 to 270 ms, increased the mean arterial pressure 4% versus nominal and 7% versus the worst (P < .001). Optimized interventricular delay increased pressure 3% versus nominal and 7% versus the worst. Optimized biventricular pacing increased the mean arterial pressure 4% versus sinus rhythm (78.5 ± 2.4 vs 75.1 ± 2.4 mm Hg; P = .002) and 3% versus atrial pacing (76.4 ± 2.7 mm Hg; P = .017).

CONCLUSIONS

Temporary biventricular pacing improves the hemodynamics after chest closure, with effects similar to those within 1 hour of bypass. Individualized optimization of atrioventricular delay is warranted, because the optimal delay was longer in 80% of our patients than the current recommendations for temporary postoperative pacing.

[Vasomotor tone and CBP : monitoring components, pratical and therapeutic approaches]

The vasomotor tone is an essential determinant of blood pressure. Vascular resistance is the result of a calculation including vasomotor tone, blood flow and blood viscosity. The vascular tone is modulated by the sympathetic system and the direct actions of drugs (patient's pathology, anaesthesia). The pressure and flow allow the vascular tone apprehension. A decrease in vasomotor tone lowers the mean arterial pressure and may cause an intense vasoplegia with arterial vascular resistance below than 800 dyn/s/cm(5) leading to a lack of tissue oxygenation. Vasomotor paralysis can be caused by the patient medications or an intense inflammatory reaction starting at the extracorporeal circulation onset. Monitoring parameters of extracorporeal circulation such as pressure, flow, arterial and venous oxygen saturation, blood level in the venous reservoir, and extensively blood gases, haemoglobin, CO(2) partial pressure level of the oxygenator vent, bispectral index, and oxygen saturation of cerebral tissue are reviewed. They will know the vasoplegia consequences and bear an indication of adequate tissue oxygenation. It may be obtained by using vasopressors (ephedrine, norepinephrine, terbutalin and vasopressin) methylene blue, increasing blood viscosity (erythrocytes) and blood flow, even by inducing hypothermia.

Stroke after coronary bypass surgery is mainly related to diffuse atherosclerotic disease

OBJECTIVE

This study aims to investigate the risk factors for postoperative stroke and analysis of outcome after coronary bypass surgery with cardiopulmonary bypass.

METHODS

Between 1999 and 2008, 3248 consecutive patients who underwent isolated coronary surgery with cardiopulmonary bypass were prospectively enrolled in the study. Demographic and perioperative data were analyzed. Postoperative stroke was defined as severe adverse neurological events including permanent deficits or cerebral lesions with radiological demonstration of cerebral infarction within the first postoperative month.

RESULTS

In total, 32 patients (0.9%) were determined with stroke. Univariate risk factors for postoperative stroke were determined as preoperative unstable angina (P = .006), Canadian Class of Angina (CCA) ≥ 3 (P = .001), preoperative creatinin level >1.2 mg/dL (P = .001), left main coronary artery disease (P = .04), chronic obstructive lung disease (P = .04), peripheral arterial disease (P < .001), New York Heart Association (NYHA) Class ≥ 3 (P = .004), preoperative renal insufficiency (P = .001), age > 65 years (P = .04), preoperative hypothyroidism (P = .02), postoperative low cardiac output state (P < .001), severe coronary artery disease requiring distal anastomosis ≥ 4 (P = .05), non-elective operation (P = .02), and body mass index ≥ 25 (P = .02). Multivariate analysis revealed peripheral arterial disease (odds ratio [OR], 5.2; 95% confidence interval [CI], 1.9-14.0; P = .001), severe coronary artery disease (OR, 3.1; 95% CI, 1.1-8.5; P = .02), and postoperative low cardiac output state (OR, 5.1; 95% CI, 1.4-18.2; P = .01) as the independent risk factors.

CONCLUSIONS

Stroke after coronary bypass surgery with cardiopulmonary bypass is mainly related to diffuse atherosclerotic disease.

The influence of mean arterial blood pressure during cardiopulmonary bypass on postoperative renal dysfunction in elderly patients

The aim of the study was to find out if there is an optimal mean arterial blood pressure (MABP) during cardiopulmonary bypass (CPB) for renal function in elderly patients during the early postoperative period. We analysed the data of 122 patients >70 years of age with normal preoperative renal function who had been subjected to coronary artery bypass grafting (CABG) procedures on CPB. Patients were divided into 3 groups, according to MABP during CPB: group MP (n=50) included patients whose MABP was maintained between 60-70 mmHg; group LP (n=36), the MABP was <60 mmHg; and group HP (n=36) where the MABP was >70 mmHg. The patients' clinical data were evaluated during the first three postoperative days. The rate of renal impairment (urine output <50ml/h) in the early postoperative period after cardiac surgery did not differ among the groups. Oliguria developed in 3 patients (6%) of the MP group, in 2 patients (5.6%) in the LP group and in 6 patients (16.7%) in the HP group (χ(2)=3.6, df=2, p=0.161). Evaluation of MABP on renal excretion showed that there was no difference in urine output among the groups. Serum creatinine levels at the end of the first postoperative day in groups MP, LP and HP were 102.7±20.1, 116.4±58.6 and 113.2±39.8 µmol/L, respectively (F=0.5, df=2, p=0.640). There were no significant differences among the groups at the end of the second and the third day either. Volume balance at the end of surgery and during the early postoperative period was similar in all groups. The need for diuretics did not differ among the groups. The length of postoperative hospital stay was not significantly different among the groups. Our study did not reveal any relationship between a MABP of 48-80 and postoperative renal dysfunction in elderly patients after CABG surgery.

Predicting the limits of cerebral autoregulation during cardiopulmonary bypass

BACKGROUND

Mean arterial blood pressure (MAP) targets are empirically chosen during cardiopulmonary bypass (CPB). We have previously shown that near-infrared spectroscopy (NIRS) can be used clinically for monitoring cerebral blood flow autoregulation. The hypothesis of this study was that real-time autoregulation monitoring using NIRS-based methods is more accurate for delineating the MAP at the lower limit of autoregulation (LLA) during CPB than empiric determinations based on age, preoperative history, and preoperative blood pressure.

METHODS

Two hundred thirty-two patients undergoing coronary artery bypass graft and/or valve surgery with CPB underwent transcranial Doppler monitoring of the middle cerebral arteries and NIRS monitoring. A continuous, moving Pearson correlation coefficient was calculated between MAP and cerebral blood flow velocity and between MAP and NIRS data to generate mean velocity index and cerebral oximeter index. When autoregulated, there is no correlation between cerebral blood flow and MAP (i.e., mean velocity and cerebral oximetry indices approach 0); when MAP is below the LLA, mean velocity and cerebral oximetry indices approach 1. The LLA was defined as the MAP at which mean velocity index increased with declining MAP to ≥ 0.4. Linear regression was performed to assess the relation between preoperative systolic blood pressure, MAP, MAP in 10% decrements from baseline, and average cerebral oximetry index with MAP at the LLA.

RESULTS

The MAP at the LLA was 66 mm Hg (95% prediction interval, 43 to 90 mm Hg) for the 225 patients in which this limit was observed. There was no relationship between preoperative MAP and the LLA (P = 0.829) after adjusting for age, gender, prior stroke, diabetes, and hypertension, but a cerebral oximetry index value of >0.5 was associated with the LLA (P = 0.022). The LLA could be identified with cerebral oximetry index in 219 (94.4%) patients. The mean difference in the LLA for mean velocity index versus cerebral oximetry index was -0.2 ± 10.2 mm Hg (95% CI, -1.5 to 1.2 mm Hg). Preoperative systolic blood pressure was associated with a higher LLA (P = 0.046) but only for those with systolic blood pressure ≤ 160 mm Hg.

CONCLUSIONS

There is a wide range of MAP at the LLA in patients during CPB, making estimation of this target difficult. Real-time monitoring of autoregulation with cerebral oximetry index may provide a more rational means for individualizing MAP during CPB.

Multimodal brain monitoring reduces major neurologic complications in cardiac surgery

OBJECTIVE

Although adverse neurologic outcomes are common complications of cardiac surgery, intraoperative brain monitoring has not received adequate attention. The aim of the present study was to evaluate the effectiveness of multimodal brain monitoring in the prevention of major brain injury and reducing the duration of mechanical ventilation, intensive care unit, and postoperative hospital stays after cardiac surgery.

DESIGN

A retrospective, observational, controlled study.

SETTING

A single-center regional hospital.

PARTICIPANTS

One thousand seven hundred twenty-one patients who had undergone cardiac surgery with cardiopulmonary bypass from July 2007 to July 2010. One hundred sixty-six patients with multimodal brain monitoring and a control group without brain monitoring (N = 1,555) were compared retrospectively.

INTERVENTIONS

Multimodal brain monitoring was performed for 166 patients, consisting of intraoperative recordings of somatosensory-evoked potentials, electroencephalography, and transcranial Doppler.

MEASUREMENTS AND MAIN RESULTS

The incidence of major neurologic complications and the duration of mechanical ventilation, intensive care unit, and postoperative hospital stays were considered. Patients with brain monitoring had a significantly lower incidence of perioperative major neurologic complications (0%) than those without monitoring (4.06%, p = 0.01) and required significantly shorter periods of mechanical ventilation (p = 0.001) and intensive care unit stays (p = 0.01) than controls. The length of postoperative hospital stays did not differ significantly between the 2 groups (p = 0.57).

CONCLUSIONS

This preliminary study suggests that multimodal brain monitoring can reduce the incidence of neurologic complications as well as hospital costs associated with post-cardiac surgery patient care. Furthermore, intraoperative brain monitoring provides useful information about brain functioning, blood flow velocity, and metabolism, which may guide the anesthesiologist during surgery.

Is carotid artery disease responsible for perioperative strokes after coronary artery bypass surgery?

The coronary and extracranial carotid vascular beds are often simultaneously affected by significant atherosclerotic disease, and stroke is one of the potential major complications of coronary artery surgery. As a result, there is no shortage of reports in the vascular surgery literature describing simultaneous coronary and carotid artery revascularizations. Generally, these reports have found this combination of operations safe, but have stopped short of proving that it is necessary. Intuitively, simultaneous carotid endarterectomy and coronary artery bypass surgery could be justified if most perioperative strokes were the result of a significant carotid stenosis, either directly or indirectly. At first glance this appears to be a fairly straightforward issue; however, much of the evidence on both sides of the argument is circumstantial. One significant problem in analyzing outcome by choice of treatment in patients presenting with both coronary and carotid disease is the multiple potential causes of stroke in coronary bypass patients, which include hemorrhage and atheroemboli from aortic atheromas during clamping. But this controversial subject is now open to discussion, and our debaters have been given the challenge to clarify the evidence to justify their claims.

The effect of blood pressure on cerebral outcome in a rat model of cerebral air embolism during cardiopulmonary bypass

OBJECTIVE

Higher mean arterial pressure during cardiopulmonary bypass may improve cerebral outcome associated with cerebral air embolism by increasing emboli clearance and collateral flow to salvage the ischemic penumbra. However, this may come at the expense of increased delivery of embolic load. This study was designed to investigate the influence of mean arterial pressures on cerebral functional and histologic outcome after cerebral air embolism during cardiopulmonary bypass in an established rat model.

METHODS

Male Sprague-Dawley rats were exposed to 90 minutes of normothermic cardiopulmonary bypass with 10 cerebral air embolisms (0.3 μL/bolus) injected repetitively. Rats were randomized to 3 groups (n = 10, each) that differed in mean arterial pressure management during cardiopulmonary bypass: 50 mm Hg (low mean arterial pressure), 60 to 70 mm Hg (standard mean arterial pressure), and 80 mm Hg (high mean arterial pressure). Neurologic score was assessed on postoperative days 3 and 7 when cerebral infarct volumes were determined. Cognitive function was determined with the Morris water maze test beginning on postoperative day 3 and continuing to postoperative day 7.

RESULTS

Neurologic score was better in high and standard mean arterial pressure groups versus low mean arterial pressure groups. High mean arterial pressure resulted in shorter water maze latencies compared with standard and low mean arterial pressure on postoperative days 6 and 7. Total infarct volume and number of infarct areas were not different among groups.

CONCLUSIONS

The use of higher mean arterial pressure during cardiopulmonary bypass in a rat model of cerebral air embolism conveyed beneficial effects on functional cerebral outcome with no apparent disadvantage of increased delivery of embolic load. Maintaining higher perfusion pressures in situations of increased cerebral embolic load may be considered as a collateral therapeutic strategy.

Animal models of cardiopulmonary bypass: development, applications, and impact

Neurologic and neurocognitive complications after cardiac surgery have been reported repeatedly. To better understand its etiology and design protective strategies, small animal models have been developed. This study describes the development of a survival rat cardiopulmonary bypass (CPB) model, along with the introduction of an appropriately sized oxygenator. This model led the way for even more complicated models with CPB, facilitating full cardiac arrest with anterograde cardioplegia administration, air embolization, and deep hypothermic circulatory arrest. In addition, the results of several of those rat CPB studies are summarized and their preclinical relevance is pointed out.

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.

Measurement of post-operative cognitive dysfunction after cardiac surgery: a systematic review

Post-operative cognitive dysfunction (POCD) is a decline in cognitive function from pre-operative levels, which has been frequently described after cardiac surgery. The purpose of this study was to examine the variability in the measurement and definitions for POCD using the framework of a 1995 Consensus Statement on measurement of POCD. Electronic medical literature databases were searched for the intersection of the search terms 'thoracic surgery' and 'cognition, dementia, and neuropsychological test.' Abstracts were reviewed independently by two reviewers. English articles with >50 participants published since 1995 that performed pre-operative and post-operative psychometric testing in patients undergoing cardiac surgery were reviewed. Data relevant to the measurement and definition of POCD were abstracted and compared with the recommendations of the Consensus Statement. Sixty-two studies of POCD in patients undergoing cardiac surgery were identified. Of these studies, the recommended neuropsychological tests were carried out in less than half of the studies. The cognitive domains measured most frequently were attention (n=56; 93%) and memory (n=57; 95%); motor skills were measured less frequently (n=36; 60%). Additionally, less than half of the studies examined anxiety and depression, performed neurological exam, or accounted for learning. Four definitions of POCD emerged: per cent decline (n=15), standard deviation decline (n=14), factor analysis (n=13), and analysis of performance on individual tests (n=12). There is marked variability in the measurement and definition of POCD. This heterogeneity may impede progress by reducing the ability to compare studies on the causes and treatment of POCD.

Central Nervous System Protection in Cardiac Surgery

Neurological dysfunction and stroke following cardiac surgery and thoracic surgery requiring hypothermic circulatory arrest is a well-defined problem. The original studies in CABG patients identified risk factors, such as prior stroke and lower educational level. There is older evidence suggesting that higher perfusion pressures during cardiopulmonary bypass are helpful. Hyperthermia during rewarming on cardiopulmonary bypass and postoperative hyperthermia have been associated with adverse cognitive outcomes. Glucose management intraoperatively remains controversial, but most now advocate for moderate glucose control using insulin, if required. The subset of patients having thoracic aortic surgery requiring periods of aortic discontinuity are particularly problematic. A cerebral protection strategy should be determined, and this may include hypothermic circulatory arrest, selective cerebral perfusion, or retrograde cerebral perfusion. All of these techniques have been associated with good surgical outcomes, but there is little information on cognitive outcomes of thoracic aortic surgery.

Lower perfusion pressure during hypothermic cardiopulmonary bypass is associated with decreased cerebral blood flow and impaired memory performance 6 months postoperatively

OBJECTIVES

We undertook to determine the influence of perfusion pressure during hypothermic cardiopulmonary bypass (CPB) on cerebral blood flow (CBF) and cognitive memory outcome at 6 months postoperatively.

METHODS

Nineteen patients who underwent hypothermic nonpulsatile CPB for elective coronary artery bypass (CAB) surgery were evaluated by (133)Xe measurement of the CBF and by the Incidental Memory Assessment for evaluating cognitive memory (IMTscore), both at baseline before the operation (T(1)) and again at 5 to 6 months postoperatively (T(2)).

RESULTS

Overall, the mean CBF fell significantly from 39 +/- 5 mL.(100 g)(-1).min(-1) at T(1) to 33 +/- 3 mL.(100 g)(-1).min(-1) at T(2) (P < .001). The decrease in CBF from T(1) to T(2) (DeltaCBF(2-1)) correlated with a significant reduction in the IMTscore from T1 to T2 (DeltaIMTscore(2-1)) (P < .001) and with a mean arterial pressure during CPB (MAPCPB) of <60 mm Hg (P = .05). Cluster analysis of DeltaCBF(2-1) and DeltaIMTscore(2-1) demonstrated that the patients with the greatest decrease in CBF showed the greatest decrease in IMTscore, whereas cluster analysis of DeltaCBF(2-1) and MAPCPB indicated that patients with a perfusion pressure maintained at a mean of <60 mm Hg during CPB were prone to a greater decrease in later postoperative CBF.

CONCLUSION

This study demonstrated that a MAPCPB of <60 mm Hg during CPB was associated with a significant decrease in CBF 6 months after CAB surgery and with an associated decrease in memory performance.

Role of surgical factors in strokes after cardiac surgery

Deficient neurological disorders after heart surgery are destructive and affect vital prognosis. They concern between 3% to 9% of patients and are related mainly to embolic episodes or brain perfusion defects. The causes of these mechanisms are numerous, but surgical procedures and cardiopulmonary bypass optimization reduce their occurrence significantly.

Safety of coronary artery bypass grafting in patients with bilateral total carotid occlusions

The presence of bilateral carotid artery occlusions in patients that require coronary artery bypass surgery is rare. Here, we report the successful coronary revascularization of two patients with cardiopulmonary bypass under moderate hypothermia. Routine preoperative carotid artery duplex sonographies revealed bilateral total internal carotid occlusions. However, no neurological deficits or abnormalities were found on clinical examination or brain computed tomography, respectively. The vertebral blood flows of both patients were also found to be highly increased. Following successful surgery, the postoperative courses were uneventful and patients were discharged from the hospital on the seventh postoperative day.

Early blood biomarkers predict organ injury and resource utilization following complex cardiac surgery

BACKGROUND

Patients undergoing complex cardiac surgery (thoracic aorta and valve) are at risk for organ failure and increased resource utilization. Neutrophil gelatinase-associated lipocalin (NGAL) has been found to be an early biomarker for renal injury. Multiplex cytokine immunoassays allow the evaluation of the early inflammatory response. We examined the relationship between early biomarker appearance (NGAL and multiplex cytokines) and organ injury and resource utilization.

MATERIALS AND METHODS

NGAL and multiplex cytokine immunoassays were performed at baseline, 1, 6, and 24 h following surgery on 38 patients undergoing thoracic aorta and valve operations. The mean age was 65 y with 26 males and 12 females. Acute kidney injury (AKIN definition), pulmonary failure (>24 h ventilation), and intensive care unit and hospital stays were examined.

RESULTS

One hour following complex cardiac surgery, the quartile of patients with the greatest IL-6 response had higher serum NGAL levels compared with the lowest quartile (347 versus 145 ng/mL, P=0.002), and 70% of these patients progressed to clinical kidney injury. Six hours following surgery, the quartile of patients with the greatest IL-10 response had higher serum NGAL compared with the lowest quartile (271 versus 160, P =0.04), more pulmonary failure (60% versus 10%, P =0.01), and longer ICU and hospital stays (P =0.001).

CONCLUSIONS

Patients with early elevated biomarkers of inflammation exhibited higher NGAL, more pulmonary failure, and greater resource utilization. Earlier identification of patients at risk for organ injury may allow for earlier intervention and reduce resource utilization.

The effect of angiotensin-converting enzyme inhibitor on hemodynamic instability in patients undergoing cardiopulmonary bypass: results of a dose-comparison study

BACKGROUND

Recently, hemodynamic instability including hypotension and its effect on the clinical outcome in patients treated with angiotensin-converting enzyme inhibitors (ACEIs) during coronary artery bypass graft (CABG) has been described. However, no analysis has examined the dose of ACEIs and its risk of hypotension. In this study, we tested the hypothesis that a higher dose of ACEIs could lead to increased episodes of hypotension.

METHODS

A total of 300 patients scheduled for CABG were studied prospectively. They were divided into 3 groups according to their preoperative use of different doses of ACEIs. The demographic and medical characteristics were compared between these 3 groups. During CABG and throughout the intensive care unit (ICU), vasoconstrictors were infused in patients undergoing hypotension (mean arterial pressure [MAP] < 65 mm Hg or >30% below baseline). The predictive factors responsible for hypotension were investigated separately using univariate and multivariate logistic regression models.

RESULTS

The 3 groups were similar with regard to the patients' demographic and medical characteristics. The patients treated with ACEIs were more likely to develop hypotension (73% of high dose and 47% of low dose) in the operating room than those without ACEIs (30%). However, in the ICU, there was no significant association between hemodynamic changes and ACEIstreated patients. Other independent risk factors identified for hypotension were ejection fraction, history of myocardial infarction, coronary grafting count, and pump time during surgery and/or ICU admission.

CONCLUSIONS

Hemodynamic changes during CABG were observed to be directly proportional to the dosage of ACEIs prescribed preoperatively.