Intraoperative physiologic variables and outcome in cardiac surgery: Part II. Neurologic outcome

Postoperative stroke in acute type A aortic dissection: incidence, outcomes, and perioperative risk factors

BACKGROUND

Despite advances in surgical techniques, the incidence of stroke following acute type A aortic dissection (ATAAD) repair remains markedly high, with substantial immediate and long-term adverse outcomes such as elevated mortality, extended hospital stays, and persistent neurological impairments. The complexity of managing ATAAD extends beyond the operation itself, highlighting a crucial gap in research concerning modifiable preoperative patient conditions and perioperative anesthetic management strategies.

OBJECTIVES

This investigation aimed to elucidate the incidence, consequences, and perioperative determinants of stroke following surgical intervention for acute type A aortic dissection (ATAAD).

METHODS

In a multicenter retrospective analysis, 516 ATAAD surgery patients were evaluated. The data included demographic information, clinical profiles, surgical modalities, and outcomes. The primary endpoint was postoperative stroke incidence, with hospital mortality and other complications serving as secondary endpoints.

RESULTS

Postoperative stroke occurred in 13.6% of patients (70 out of 516) and was associated with significant extension of the ICU (median 10 vs. 5 days, P < 0.001) and hospital stay (median 18 vs. 12 days, P < 0.001). The following key independent stroke risk factors were identified: modified Frailty Index (mFI) ≥ 4 (odds ratio [OR]: 4.18, 95% confidence interval [CI]: 1.24-14.1, P = 0.021), common carotid artery malperfusion (OR: 3.76, 95% CI: 1.23-11.44, P = 0.02), pre-cardiopulmonary bypass (CPB) hypotension (mean arterial pressure ≤ 50 mmHg; OR: 2.17, 95% CI: 1.06-4.44, P = 0.035), ≥ 20% intraoperative decrease in cerebral regional oxygen saturation (rSO2) (OR: 1.93, 95% CI: 1.02-3.64, P = 0.042), and post-CPB vasoactive-inotropic score (VIS) ≥ 10 (OR: 2.24, 95% CI: 1.21-4.14, P = 0.01).

CONCLUSIONS

Postoperative stroke significantly increases ICU and hospital durations in ATAAD surgery patients. These findings highlight the critical need to identify and mitigate major risks, such as high mFI, common carotid artery malperfusion, pre-CPB hypotension, significant cerebral rSO2 reductions, and elevated post-CPB VIS, to improve outcomes and reduce stroke prevalence.

TRIAL REGISTRATION

Thai Clinical Trials Registry (TCTR20230615002). Date registered on June 15, 2023. Retrospectively registered.

Protease-Activated Receptors (PARs): Biology and Therapeutic Potential in Perioperative Stroke

Perioperative stroke is a devastating complication that occurs during surgery or within 30 days following the surgical procedure. Its prevalence ranges from 0.08 to 10% although it is most likely an underestimation, as sedatives and narcotics can substantially mask symptomatology and clinical presentation. Understanding the underlying pathophysiology and identifying potential therapeutic targets are of paramount importance. Protease-activated receptors (PARs), a unique family of G-protein-coupled receptors, are widely expressed throughout the human body and play essential roles in various physiological and pathological processes. This review elucidates the biology and significance of PARs, outlining their diverse functions in health and disease, and their intricate involvement in cerebrovascular (patho)physiology and neuroprotection. PARs exhibit a dual role in cerebral ischemia, which underscores their potential as therapeutic targets to mitigate the devastating effects of stroke in surgical patients.

Effect of Intraoperative Arterial Hypotension on the Risk of Perioperative Stroke After Noncardiac Surgery: A Retrospective Multicenter Cohort Study

BACKGROUND

Intraoperative cerebral blood flow is mainly determined by cerebral perfusion pressure and cerebral autoregulation of vasomotor tone. About 1% of patients undergoing noncardiac surgery develop ischemic stroke. We hypothesized that intraoperative hypotension within a range frequently observed in clinical practice is associated with an increased risk of perioperative ischemic stroke within 7 days after surgery.

METHODS

Adult noncardiac surgical patients undergoing general anesthesia at Beth Israel Deaconess Medical Center and Massachusetts General Hospital between 2005 and 2017 were included in this retrospective cohort study. The primary exposure was intraoperative hypotension, defined as a decrease in mean arterial pressure (MAP) below 55 mm Hg, categorized into no intraoperative hypotension, short (<15 minutes, median [interquartile range {IQR}], 2 minutes [1-5 minutes]) and prolonged (≥15 minutes, median [IQR], 21 minutes [17-31 minutes]) durations. The primary outcome was a new diagnosis of early perioperative ischemic stroke within 7 days after surgery. In secondary analyses, we assessed the effect of a MAP decrease by >30% from baseline on perioperative stroke. Analyses were adjusted for the preoperative STRoke After Surgery (STRAS) prediction score, work relative value units, and duration of surgery.

RESULTS

Among 358,391 included patients, a total of 1553 (0.4%) experienced an early perioperative ischemic stroke. About 42% and 3% of patients had a MAP of below 55 mm Hg for a short and a prolonged duration, and 49% and 29% had a MAP decrease by >30% from baseline for a short and a prolonged duration, respectively. In an adjusted analysis, neither a MAP <55 mm Hg (short duration: adjusted odds ratio [ORadj], 0.95; 95% confidence interval [CI], 0.85-1.07; P = .417 and prolonged duration: ORadj, 1.18; 95% CI, 0.91-1.55; P = .220) nor a MAP decrease >30% (short duration: ORadj, 0.97; 95% CI, 0.67-1.42; P = .883 and prolonged duration: ORadj, 1.30; 95% CI, 0.89-1.90; P = .176) was associated with early perioperative stroke. A high a priori stroke risk quantified based on preoperatively available risk factors (STRAS prediction score) was associated with longer intraoperative hypotension (adjusted incidence rate ratio, 1.04; 95% CI, 1.04-1.05; P < .001 per 5 points of the STRAS prediction score).

CONCLUSIONS

This study found no evidence to conclude that intraoperative hypotension within the range studied was associated with early perioperative stroke within 7 days after surgery. These findings emphasize the importance of perioperative cerebral blood flow autoregulation to prevent ischemic stroke.

A Comprehensive Review of Risk Factor, Mechanism, and Management of Left Ventricular Assist Device-Associated Stroke

The use of left ventricular assist devices (LVADs) has been increasing in the last decade, along with the number of patients with advanced heart failure refractory to medical therapy. Ischemic stroke and intracranial hemorrhage remain the leading causes of morbidity and mortality in LVAD patients. Despite the common occurrence and the significant outcome impact, underlying mechanisms and management strategies of stroke in LVAD patients are controversial. In this article, we review our current knowledge on pathophysiology and risk factors of LVAD-associated stroke, outline the diagnostic approach, and discuss treatment strategies.

Independent Predictors of Postoperative Stroke With Cardiopulmonary Bypass

OBJECTIVE

To assess predictive factors of postoperative stroke in cardiac surgery using cardiopulmonary bypass (CPB).

DESIGN

This study was a retrospective observational study.

SETTING

This study was conducted at a single institution (Liverpool Hospital, NSW, Australia).

PARTICIPANTS

All patients with CPB treated surgically at Liverpool Hospital, NSW, between January 2016 and December 2018 INTERVENTIONS: Patients underwent cardiac surgery with CPB.

MEASUREMENTS AND MAIN RESULTS

The primary outcome was cerebrovascular accident, or stroke. Univariate and multivariate analyses via Firth's logistic regression with regard to stroke were performed. The study comprised 1,092 patients over a three-year period. In this cohort, the stroke rate was 3.1%. Via univariate analysis of factors in relation to stroke post-CPB, recent or past stroke (odds ratio [OR] 5.43 v 2.32), diabetes mellitus (OR 1.92), dialysis dependence (OR 5.67), elective procedures (OR 0.34), aortic procedures (OR 4.02), bypass and cross-clamp times (OR 1.02 and 1.04), postoperative atrial fibrillation (OR 2.28), and hypoperfusion times all reached the significance level of p ≤ 0.1 to be included in the multivariate analysis. Multivariate analysis to find independent factors in relation to stroke yielded diabetes mellitus (OR 2.49; p = 0.025), dialysis dependence (OR 3.82; p = 0.03), aortic procedures (OR 3.93; p = 0.014), and elective procedures (OR 0.24; p = 0.026) as independently predictive or protective with regard to postoperative stroke.

CONCLUSIONS

Independent predictors of stroke in this single center cohort included dialysis dependence, diabetes, and aortic procedures. Elective procedures were shown to be an independent protective factor.

Association Between Coronary Artery Bypass Surgical Techniques and Postoperative Stroke

Background The impact of the coronary artery bypass grafting (CABG) technique (on- versus off-pump, single versus multiple aortic clamping) on postoperative neurological outcome remains a matter of controversy. The aim of this study was to assess the association between the incidence of postoperative stroke and the degree of aortic manipulation in one of the largest contemporary CABG series. Methods and Results A retrospective, multicenter, international study was conducted in 25 388 patients undergoing isolated CABG procedures with on-pump CABG (ONCAB) or off-pump CABG (OPCAB) technique including single or multiple aortic clamping. Postoperative stroke was defined as a postoperative neurological deficit lasting more than 24 hours and associated with evidence of a brain lesion on computed tomography. The degree of aortic manipulation was assumed to be higher for on-pump versus off-pump surgery and for multiple versus single or no aortic clamping. Logistic regression and propensity matching were used. ONCAB procedures were performed in 17 231 cases and OPCAB in 8157. The incidence of postoperative stroke was significantly lower in the OPCAB group even after propensity matching (0.4% OPCAB versus 1.2% ONCAB, P=0.02). In the ONCAB group (but not in the OPCAB arm) the use of single aortic clamping was associated with significantly reduced postoperative stroke rate (odds ratio, 0.05; 95% CI, 0.008 to 0.07 [P<0.001]). Conclusions OPCAB and the use of single aortic clamping in the ONCAB arm were associated with a reduced incidence of postoperative stroke. Our data confirm a strong association between aortic manipulation and neurological outcome after CABG surgery.

High variance of intraoperative blood pressure predicts early cerebral infarction after revascularization surgery in patients with Moyamoya disease

Few studies focused on the intraoperative blood pressure in Moyamoya disease (MMD) patients. We aimed to clarify whether or not it relates to early cerebral infarction after revascularization. We reviewed a retrospective cohort of Moyamoya disease from 2011 to 2018 in Beijing Tiantan Hospital, and patients with radiologically confirmed early postoperative infarction were included in the analysis. Controls were matched based on age, sex, and revascularization modality at a ratio of 1:5. Perioperative clinical factors and intraoperative blood pressure data were collected and analyzed. A total of 52 patients out of 1497 revascularization surgeries (3.5%) who experienced CT or MRI confirmed early postoperatively cerebral infarction, aged 38.46 ± 11.70; 26 were male (50.0%). Average real variability (ARV)-systolic blood pressure (SBP) (OR 3.29, p = 0.003), ARV-diastolic blood pressure (DBP) (OR 4.10, p = 0.005), ARV-mean arterial pressure (MAP) (OR 4.08, p = 0.004), and the maximum drops of DBP (OR 1.08, p = 0.003) and MAP (OR 1.06, p = 0.004) were associated with early postoperative infarction. In patients who experienced massive cerebral infarction, the maximum drops of DBP (OR 1.11, p = 0.004) and MAP (OR 1.11, p = 0.003) are independent risk factors, whereas ARVs of SBP (OR 3.90, p < 0.001), DBP (OR 4.69, p = 0.008), and MAP (OR 4.72, p = 0.003) are significantly associated with regional infarction. High variance of intraoperative blood pressure and drastic blood pressure decline are independent risk factors for postoperative infarction in MMD patients who underwent revascularization surgery. Maintaining stable intraoperative blood pressure is suggested to prevent early postoperative cerebral infarction in MMD patients.

Relationship Between the Ambulatory Arterial Stiffness Index and the Lower Limit of Cerebral Autoregulation During Cardiac Surgery

Background

Pulse pressure, the ambulatory arterial stiffness index (AASI), and the symmetric AASI are established predictors of adverse cardiovascular outcomes. However, little is known about their relationship to cerebral autoregulation. This study evaluated whether these markers of vascular properties relate to the lower limit of cerebral autoregulation (LLA).

Methods and Results

The LLA was determined during cardiac surgery with transcranial Doppler ultrasonography in 181 patients. All other variables were calculated from continuous intraoperative readings obtained before cardiopulmonary bypass. The LLA varied directly with the AASI (β=3.12 per 0.1 change in AASI, P<0.001) and to a lesser extent the symmetric AASI (β=2.02 per 0.1 change in symmetric AASI, P≤0.022), while peripheral pulse pressure was not significantly related (β=0.0, P>0.99). Logistic regression revealed that the likelihood of LLA being >65 mm Hg increased by 50% (95% confidence interval, 11%–102%, P=0.008) for every 0.1 increase in the AASI. The AASI was able to predict a LLA above certain thresholds (area under the curve receiver operating characteristic for AASI predicting an LLA >65 mm Hg: 0.60; 95% confidence interval, 0.51%–0.68%, P=0.043). Incorporating additional variables improved the model's predictive ability (area under the curve for AASI predicting a LLA >65 mm Hg: 0.75; 95% confidence interval, 0.68–0.82, P=0.036).

Conclusions

These data indicate that the LLA is related to the mechanical properties of the vasculature as represented by the AASI. The AASI can be used to predict LLA threshold levels during cardiac surgery. It is now possible to link elevations in the LLA with an increased AASI as determined from readily accessible intraoperative variables.

Sequential regression measurement error models with application

Sequential regression approaches can be used to analyze processes in which covariates are revealed in stages. Such processes occur widely, with examples including medical intervention, sports contests and political campaigns. The naïve sequential approach involves fitting regression models using the covariates revealed by the end of the current stage, but this is only practical if the number of covariates is not too large. An alternative approach is to incorporate the score (linear predictor) from the model developed at the previous stage as a covariate at the current stage. This score takes into account the history of the process prior to the stage under consideration. However, the score is a function of fitted parameter estimates and, therefore, contains measurement error. In this article, we propose a novel technique to account for error in the score. The approach is demonstrated with application to the sprint event in track cycling and is shown to reduce bias in the estimated effect of the score and avoid unrealistically extreme predictions.

Perfusion Pressure Cerebral Infarct (PPCI) trial - the importance of mean arterial pressure during cardiopulmonary bypass to prevent cerebral complications after cardiac surgery: study protocol for a randomised controlled trial

Background

Debilitating brain injury occurs in 1.6–5 % of patients undergoing cardiac surgery with cardiopulmonary bypass. Diffusion-weighted magnetic resonance imaging studies have reported stroke-like lesions in up to 51 % of patients after cardiac surgery. The majority of the lesions seem to be caused by emboli, but inadequate blood flow caused by other mechanisms may increase ischaemia in the penumbra or cause watershed infarcts. During cardiopulmonary bypass, blood pressure can be below the lower limit of cerebral autoregulation. Although much debated, the constant blood flow provided by the cardiopulmonary bypass system is still considered by many as appropriate to avoid cerebral ischaemia despite the low blood pressure.

Methods/design

The Perfusion Pressure Cerebral Infarct trial is a single-centre superiority trial with a blinded outcome assessment. The trial is randomising 210 patients with coronary vessel and/or valve disease and who are undergoing cardiac surgery with the use of cardiopulmonary bypass. Patients are stratified by age and surgical procedure and are randomised 1:1 to either an increased mean arterial pressure (70–80 mmHg) or ‘usual practice’ (40–50 mmHg) during cardiopulmonary bypass.

The cardiopulmonary bypass pump flow is fixed and set at 2.4 L/minute/m² body surface area plus 10–20 % in both groups.

The primary outcome measure is the volume of the new ischaemic cerebral lesions (in mL), expressed as the difference between a baseline, diffusion-weighted, magnetic resonance imaging scan and an equal scan conducted 3–6 days postoperatively. Secondary endpoints are the total number of new ischaemic cerebral lesions, postoperative cognitive dysfunction at discharge and 3 months postoperatively, diffuse cerebral injury evaluated by magnetic resonance spectroscopy and selected biochemical markers of cerebral injury.

The sample size will enable us to detect a 50 % reduction in the primary outcome measure in the intervention compared to the control group at a significance level of 0.05 and with a power of 0.80.

Discussion

This is the first clinical randomised study to evaluate whether the mean arterial pressure level during cardiopulmonary bypass influences the development of brain injuries that are detected by diffusion-weighted magnetic resonance imaging.

Trial registration

ClinicalTrials.gov, NCT02185885. Registered on 7 July 2014.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-016-1373-6) contains supplementary material, which is available to authorized users.

The Effect of Patient-Specific Cerebral Oxygenation Monitoring on Postoperative Cognitive Function: A Multicenter Randomized Controlled Trial

BACKGROUND

Indices of global tissue oxygen delivery and utilization such as mixed venous oxygen saturation, serum lactate concentration, and arterial hematocrit are commonly used to determine the adequacy of tissue oxygenation during cardiopulmonary bypass (CPB). However, these global measures may not accurately reflect regional tissue oxygenation and ischemic organ injury remains a common and serious complication of CPB. Near-infrared spectroscopy (NIRS) is a noninvasive technology that measures regional tissue oxygenation. NIRS may be used alongside global measures to optimize regional perfusion and reduce organ injury. It may also be used as an indicator of the need for red blood cell transfusion in the presence of anemia and tissue hypoxia. However, the clinical benefits of using NIRS remain unclear and there is a lack of high-quality evidence demonstrating its efficacy and cost effectiveness.

OBJECTIVE

The aim of the patient-specific cerebral oxygenation monitoring as part of an algorithm to reduce transfusion during heart valve surgery (PASPORT) trial is to determine whether the addition of NIRS to CPB management algorithms can prevent cognitive decline, postoperative organ injury, unnecessary transfusion, and reduce health care costs.

METHODS

Adults aged 16 years or older undergoing valve or combined coronary artery bypass graft and valve surgery at one of three UK cardiac centers (Bristol, Hull, or Leicester) are randomly allocated in a 1:1 ratio to either a standard algorithm for optimizing tissue oxygenation during CPB that includes a fixed transfusion threshold, or a patient-specific algorithm that incorporates cerebral NIRS monitoring and a restrictive red blood cell transfusion threshold. Allocation concealment, Internet-based randomization stratified by operation type and recruiting center, and blinding of patients, ICU and ward care staff, and outcome assessors reduce the risk of bias. The primary outcomes are cognitive function 3 months after surgery and infectious complications during the first 3 months after surgery. Secondary outcomes include measures of inflammation, organ injury, and volumes of blood transfused. The cost effectiveness of the NIRS-based algorithm is described in terms of a cost-effectiveness acceptability curve. The trial tests the superiority of the patient-specific algorithm versus standard care. A sample size of 200 patients was chosen to detect a small to moderate target difference with 80% power and 5% significance (two tailed).

RESULTS

Over 4 years, 208 patients have been successfully randomized and have been followed up for a 3-month period. Results are to be reported in 2015.

CONCLUSIONS

This study provides high-quality evidence, both valid and widely applicable, to determine whether the use of NIRS monitoring as part of a patient-specific management algorithm improves clinical outcomes and is cost effective.

TRIAL REGISTRATION

International Standard Randomized Controlled Trial Number (ISRCTN): 23557269; http://www.isrctn.com/ISRCTN23557269 (Archived by Webcite at http://www.webcitation.org/6buyrbj64).

Use of Blood Products and Diseased Ascending Aorta Are Determinants of Stroke After Off-Pump Coronary Artery Bypass Grafting

OBJECTIVE

To examine the effect of blood products on the occurrence of stroke after coronary artery surgery.

DESIGN

Institutional retrospective analysis.

SETTING

University hospital.

PARTICIPANTS

One thousand three hundred fourteen patients undergoing coronary artery surgery.

INTERVENTIONS

Off-pump coronary artery bypass grafting (OPCAB). Epiaortic ultrasound was performed in all patients.

MEASUREMENTS AND MAIN RESULTS

Complete pre-, intra- and postoperative data including the number of transfused blood products as well as the timing, type, and course of stroke were available in all patients. Postoperative stroke occurred in 23 patients (1.8%). Logistic regression identified transfusion of platelets (3.6% v 1.1%, p = 0.003, OR 3.34, 95%CI 1.46-7.67) and diseased ascending aorta (3.0% v 1.2%, p = 0.022, OR 2.64, 95% CI 1.15-6.06) as independent predictors of stroke. When these variables were adjusted for CHA2DS2VASc (p = 0.005, OR 1.44, 95% CI 1.12-1.86), only transfusion of platelets (p = 0.012, OR 2.91, 95% CI 1.26-6.70) was associated with stroke. Neither nadir hematocrit on the day of surgery nor nadir hematocrit during the perioperative period was an independent predictor of stroke. Chi-squared automatic interaction detection analysis identified solvent/detergent-treated plasma (Octaplas; Octapharma AG, Lachen, Switzerland) units >2 and platelet units >4 along with diseased ascending aorta as independent predictors of stroke. The stroke rate was 8.9% in patients receiving >2 units of Octaplas and having a diseased ascending aorta. In patients receiving ≤2 units of Octaplas, the stroke rate was as high as 3.8% in patients receiving >4 units of platelets.

CONCLUSIONS

The results of this study indicated that atherosclerosis of the ascending aorta as well as transfusion of platelets and/or Octaplas were independent predictors of stroke after OPCAB.

[Epidemiology of cerebral perioperative vascular accidents]

OBJECTIVES

Stroke is a well-described postoperative complication, after carotid and cardiac surgery. On the contrary, few studies are available concerning postoperative stroke in general non-cardiac non-carotid surgery. The high morbid-mortality of stroke justifies an extended analysis of recent literature.

ARTICLE TYPE

Systematic review.

DATA SOURCES

Firstly, Medline and Ovid databases using combination of stroke, cardiac surgery, carotid surgery, general non-cardiac non-carotid surgery as keywords; secondly, national and European epidemiologic databases; thirdly, expert and French health agency recommendations; lastly, reference book chapters.

RESULTS

In cardiac surgery, with an incidence varying from 1.2 to 10% according to procedure complexity, stroke occurs peroperatively in 50% of cases and during the first 48 postoperative hours for the others. The incidence of stroke after carotid surgery is 1 to 20% according to the technique used as well as operator skills. Postoperative stroke is a rare (0.15% as mean, extremes around 0.02 to 1%) complication in general surgery, it occurs generally after the 24-48th postoperative hours, exceptional peroperatively, and 40% of them occurring in the first postoperative week. It concerned mainly aged patient in high-risk surgeries (hip fracture, vascular surgery). Postoperative stroke was associated to an increase in perioperative mortality in comparison to non-postoperative stroke operated patients.

CONCLUSION

Postoperative stroke is a quality marker of the surgical teams' skill and has specific onset time and induces an increase of postoperative mortality.

Stroke after coronary artery surgery: a single center report

Stroke or cerebrovascular accident (CVA) is a devastating complication of coronary surgery. In this report, the incidence, and correlates of CVA following isolated coronary artery bypass grafting (CABG) surgery were evaluated. Data were collected retrospectively. Between 2006 and 2009, 855 patients underwent isolated CABG surgery. CVA was defined as any new neurological deficit lasting more than 24 hours. Univariate and multivariate analyses were utilized as appropriate. The incidence of CVA was 1.4% (n = 12). Age, previous CVA, and emergency surgery were correlated by univariate analysis. Multivariate analysis revealed age, previous CVA, and chronic renal impairment as predictors of CVA. Ten (83.3%) of the 12 patients were diagnosed to have CVA in the first 24 hours. Length of hospital stay was 20.9 ± 20.34 days for CVA patients and 9.2 ± 5.17 days for non-CVA patients (p ≤ 0.001). There were 4 (33.3%) deaths in CVA group and 27 (3.2%) for non-CVA patients (p = 0.001). Postoperative CVA is a major contributor to mortality, prolonged hospitalization, and other adverse postoperative complications. Further studies are needed to develop better strategies to minimize the occurrence of CVA among patients undergoing CABG.

Perioperative stroke

It is increasingly recognized that one can identify a higher risk patient for perioperative stroke. The risk of stroke around the time of operative procedures is fairly substantial and it is recognized that patients initially at risk for vascular events are those most likely to have this risk heightened by invasive procedures. Higher risk patients include those of advanced age and there is a cumulative risk, over time, of coexistent hypertension, atherosclerosis, diabetes mellitus, cardiac disease and clotting disorders. There are a number of possible mechanisms associated with the procedure (e.g., preoperative hypercoagulability, holding of antithrombic therapy at the time of the procedure and cardiac arrhythmia) that can promote a thrombo-embolic event. Examples of these include: direct mechanical trauma to extracranial vessels related to operations on the head and neck; and vascular injury as a consequence of vascular and innovative endovascular procedures affecting the cerebral circulation (e.g., carotid endarterectomy, extracranial or intracranial angioplasty with stenting, and use of the MERCI clot retrieval device), as well as various endovascular methods that have been developed to obliterate cerebral aneurysms and arteriovenous malformations as an alternative to surgical clipping and surgical resection, respectively.

Low serum sodium level during cardiopulmonary bypass predicts increased risk of postoperative stroke after coronary artery bypass graft surgery

OBJECTIVE

Rapid decreases in serum sodium levels are associated with altered mental status, seizures, and coma. During cardiac surgery, serum sodium levels decrease rapidly when cardiopulmonary bypass is initiated because cardiopulmonary bypass causes hemodilution. However, whether this decrease influences neurologic outcome after cardiac surgery remains unclear. We investigated whether the average serum sodium level during cardiopulmonary bypass is independently predictive of postoperative stroke or 30-day all-cause mortality in patients who undergo primary coronary artery bypass grafting.

METHODS

In a single-institution, retrospective cohort of 2348 consecutive patients who underwent primary, isolated coronary artery bypass grafting, sequential multivariate logistic regression was performed to determine the threshold below which the average serum sodium level during cardiopulmonary bypass independently predicts postoperative stroke or early death. To further test the validity of this threshold and to control for selection bias, stepwise multivariate logistic regression was also performed on propensity score-matched patients (n = 924).

RESULTS

An average serum sodium level less than 130 mEq/L during cardiopulmonary bypass was independently predictive of stroke, both in the entire study cohort (1.44% vs 2.92%; odds ratio, 2.09; 95% confidence interval, 1.1-4.1; P = .03) and in the propensity-matched patients (0.9% vs 3.0%; odds ratio, 4.1; 95% confidence interval, 1.3-13.0; P = .02). The average serum sodium level during cardiopulmonary bypass was not independently associated with early death, regardless of what threshold value was used.

CONCLUSIONS

An average serum sodium level of less than 130 mEq/L during cardiopulmonary bypass is independently associated with an increased risk of postoperative stroke in patients who undergo primary coronary artery bypass grafting.

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.

Anemia and red blood cell transfusion in neurocritical care

INTRODUCTION

Anemia is one of the most common medical complications to be encountered in critically ill patients. Based on the results of clinical trials, transfusion practices across the world have generally become more restrictive. However, because reduced oxygen delivery contributes to 'secondary' cerebral injury, anemia may not be as well tolerated among neurocritical care patients.

METHODS

The first portion of this paper is a narrative review of the physiologic implications of anemia, hemodilution, and transfusion in the setting of brain-injury and stroke. The second portion is a systematic review to identify studies assessing the association between anemia or the use of red blood cell transfusions and relevant clinical outcomes in various neurocritical care populations.

RESULTS

There have been no randomized controlled trials that have adequately assessed optimal transfusion thresholds specifically among brain-injured patients. The importance of ischemia and the implications of anemia are not necessarily the same for all neurocritical care conditions. Nevertheless, there exists an extensive body of experimental work, as well as human observational and physiologic studies, which have advanced knowledge in this area and provide some guidance to clinicians. Lower hemoglobin concentrations are consistently associated with worse physiologic parameters and clinical outcomes; however, this relationship may not be altered by more aggressive use of red blood cell transfusions.

CONCLUSIONS

Although hemoglobin concentrations as low as 7 g/dl are well tolerated in most critical care patients, such a severe degree of anemia could be harmful in brain-injured patients. Randomized controlled trials of different transfusion thresholds, specifically in neurocritical care settings, are required. The impact of the duration of blood storage on the neurologic implications of transfusion also requires further investigation.

Temporal pattern of strokes after on-pump and off-pump coronary artery bypass graft surgery

BACKGROUND

The incidence of strokes has not decreased after coronary artery bypass graft surgery (CABG). The purpose of this study is to identify incidence, risk factors, and temporal pattern of strokes after on-pump and off-pump CABG.

METHODS

We analyzed 2,516 consecutive patients who underwent first elective isolated CABG. The primary endpoint was strokes within 30 days. The temporal onset of the deficits was classified by consensus as either an "early stroke," which is present just after emergence from anesthesia, or a "delayed stroke," which is present after first awaking from surgery without a neurologic deficit.

RESULTS

More than half of strokes (29 of 46; 63%) were delayed strokes. Patients undergoing off-pump CABG had significantly lower risk of early stroke (0.1% versus 1.1%, p = 0.0009), whereas the incidence of delayed strokes was not different significantly (0.9% versus 1.4%, p = 0.3484) between patients undergoing on-pump and off-pump CABG. In multivariate analyses, undergoing off-pump CABG was an independent protective factor for all strokes (relative risk 0.29, 95% confidence interval: 0.14 to 0.56, p = 0.0005) and early strokes (relative risk 0.05, 95% confidence interval: 0.003 to 0.24, p < 0.0001), but it was not an independent protective factor for delayed strokes (relative risk 0.54, 95% confidence interval: 0.24 to 1.17, p = 0.1210).

CONCLUSIONS

Undergoing off-pump CABG reduces the incidence of perioperative stroke mainly by minimizing early strokes; however, the risk of delayed strokes is not different between patients undergoing on-pump and off-pump CABG.

A comparative analysis of predictive models of morbidity in intensive care unit after cardiac surgery - part I: model planning

Background

Different methods have recently been proposed for predicting morbidity in intensive care units (ICU). The aim of the present study was to critically review a number of approaches for developing models capable of estimating the probability of morbidity in ICU after heart surgery. The study is divided into two parts. In this first part, popular models used to estimate the probability of class membership are grouped into distinct categories according to their underlying mathematical principles. Modelling techniques and intrinsic strengths and weaknesses of each model are analysed and discussed from a theoretical point of view, in consideration of clinical applications.

Methods

Models based on Bayes rule, k-nearest neighbour algorithm, logistic regression, scoring systems and artificial neural networks are investigated. Key issues for model design are described. The mathematical treatment of some aspects of model structure is also included for readers interested in developing models, though a full understanding of mathematical relationships is not necessary if the reader is only interested in perceiving the practical meaning of model assumptions, weaknesses and strengths from a user point of view.

Results

Scoring systems are very attractive due to their simplicity of use, although this may undermine their predictive capacity. Logistic regression models are trustworthy tools, although they suffer from the principal limitations of most regression procedures. Bayesian models seem to be a good compromise between complexity and predictive performance, but model recalibration is generally necessary. k-nearest neighbour may be a valid non parametric technique, though computational cost and the need for large data storage are major weaknesses of this approach. Artificial neural networks have intrinsic advantages with respect to common statistical models, though the training process may be problematical.

Conclusion

Knowledge of model assumptions and the theoretical strengths and weaknesses of different approaches are fundamental for designing models for estimating the probability of morbidity after heart surgery. However, a rational choice also requires evaluation and comparison of actual performances of locally-developed competitive models in the clinical scenario to obtain satisfactory agreement between local needs and model response. In the second part of this study the above predictive models will therefore be tested on real data acquired in a specialized ICU.

Intraoperative hyperglycemia and cognitive decline after CABG

BACKGROUND

Neurocognitive dysfunction (NCD) continues to occur in a significant number of patients after cardiac procedures. The factors influencing its incidence and severity are not completely known. We hypothesized that hyperglycemia, which is known to exacerbate other forms of cerebral injury, may exacerbate NCD after cardiac operations.

METHODS

A total of 525 patients having on-pump coronary artery bypass graft (CABG) procedures underwent cognitive testing at baseline and 6 weeks postoperatively. Multivariable linear regression was used to determine the relationship between NCD and intraoperative hyperglycemia (glucose > or = 200 mg/dL). Diabetic and nondiabetic patients were analyzed separately to eliminate a possible confounding effects between diabetes and hyperglycemia.

RESULTS

In the nondiabetic patients, even after controlling for age, years of education, and baseline cognitive function, hyperglycemia was associated with a decrease in cognitive function at 6 weeks (p = 0.0351). Hyperglycemia had no effect on cognitive function in diabetic patients, however.

CONCLUSIONS

These findings suggest that in nondiabetic patients undergoing CABG operations, intraoperative hyperglycemia is associated with an increased risk of NCD.

Impaired cerebral autoregulation distal to carotid stenosis/occlusion is associated with increased risk of stroke at cardiac surgery with cardiopulmonary bypass

OBJECTIVES

Severe carotid stenosis and occlusion are associated with an increased risk of stroke during and after cardiac surgery with cardiopulmonary bypass. Relevance of an impaired cerebral autoregulation caused by stenosis/occlusion is unknown.

METHODS

We prospectively assessed the incidence of stroke in relation to severity of carotid disease and corresponding autoregulatory reserve in 2797 patients who had coronary artery bypass graft and/or valve surgery with cardiopulmonary bypass. Patients underwent preoperative carotid sonography and, in case of severe extracranial disease, transcranial Doppler sonography with carbon dioxide stimulation to assess cerebrovascular reserve capacity.

RESULTS

Sixty-seven (2.4%) patients had an ischemic stroke, which was fatal in 5. Anterior hemispheric stroke occurred in 42 (1.9%) patients with no/low-grade stenosis, 6 (1.8%) with medium-grade stenosis, 1 (0.6%) with high-grade stenosis/occlusion and normal autoregulation, and 3 (27.3%) with high-grade stenosis/occlusion and exhausted autoregulatory reserve. Increased risk was observed in patients with high-grade stenosis/occlusion and exhausted autoregulatory reserve also after adjustment for potential confounders (adjusted odds ratio [OR] 28.3, 95% confidence interval [CI] 5.8-139.1). Stroke risk was not increased in patients with stenosis/occlusion and normal autoregulation (1.5%, adjusted OR 0.6, 95% CI 0.2-1.6).

CONCLUSIONS

Cerebrovascular reserve capacity evaluated by preoperative transcranial Doppler carbon dioxide testing is a major determinant of stroke risk in patients with carotid artery stenosis/occlusion undergoing cardiac surgery with cardiopulmonary bypass. Its assessment facilitates identification of patients with an excess perioperative stroke risk.

[Neurological complications in cardiac surgery post-operative period]

The incidence of neurological complications after cardiac surgery continues to be elevated, although this is variable in the different studies published, fundamentally because of the different populations studied and the different definitions of neurological dysfunction. The etiology of these alterations is attributed to a multifactorial origin, aortic artherosclerosis, cerebral hypoperfusion and inflammatory phenomenon secondary to the technique. This review arises from the recognition of the personal, economic, and socio-health care repercussion entailed by these complications, with high rates of mortality and morbidity recorded, and it tries to give an objective view of the current literature on the subject. Having knowledge of the risk markers and understanding the pathogenesis is important to try to plan strategies that may minimize the appearance and development of these complications and contribute to the decrease of their serious consequences. The data and the experience obtained by our group are shown at the end of the review.

Intracerebral Hemorrhage Treated with External Ventricular Drainage Following Coronary Bypass Surgery

BACKGROUND

Intracerebral hemorrhagic brain injury after open heart surgery is a rare complication. We report a case of acute intraventricular hemorrhage after coronary bypass surgery.

METHODS

The brain computed tomography revealed intraventricular bleeding in the patient and urgent external ventricular drainage was performed by neurosurgeons.

RESULTS

The clinical findings disappeared after the drainage.

CONCLUSION

Early diagnosis and treatment is important in preventing organic brain damage in this complication.

Indications for Blood Transfusion in Cardiac Surgery

In addition to its life-saving effect in hemorrhagic shock, transfusion of allogenic packed red blood cells can be beneficial in situations where a critically low hematocrit is contributing to a state of oxygen-supply dependency. These benefits are countered by the risks of transfusion-associated lung injury, transfusion-associated immunomodulation, and cellular hypoxia after RBC transfusion. The critical hematocrit is patient and organ specific, and varies intraoperatively according to the duration and temperature of bypass, as well as for a variable postoperative period. Future randomized studies must prospectively evaluate regional indicators of tissue oxygenation in transfusion algorithms.

Prevention of Ischemic Neurologic Injury With Intraoperative Monitoring of Selected Cardiovascular and Cerebrovascular Procedures: Roles of Electroencephalography, Somatosensory Evoked Potentials, Transcranial Doppler, and Near-Infrared Spectroscopy

All neuromonitoring techniques, although imperfect, provide useful information for monitoring cardiothoracic and carotid vascular operations. They may be viewed as providing complementary information, which may help surgical technique and, as a result, possibly improve clinical outcomes. As of this writing, the efficacy of TCD and NIRS monitoring during cardiothoracic and vascular surgery cannot be considered established. Well designed, prospective, adequately powered, double-blind, and randomized outcome studies are needed to determine the optimal neurologic monitoring modality (or modalities), in specific surgical settings.

Predicting and preventing adverse neurologic outcomes with cardiac surgery

Adverse neurologic outcomes after cardiac surgery can have devastating consequences, among them increased mortality risk and, among survivors, loss of independence and a diminished quality of life. They also represent a burden on the health-care system, requiring prolonged hospitalizations and additional aftercare and, therefore, greater costs. Adverse outcomes are classified by their severity. Frank stroke is the most serious. This complication is associated with patient age; however, the presence of significant ascending aortic disease represents the greatest hazard. Multivariable analysis also indicates that prior neurologic events, diabetes, chronic obstructive pulmonary disease, preoperative status, and diffuse vascular disease are predictive. The second type of adverse cerebral outcome includes neurocognitive abnormalities such as memory loss and diminished emotional health. The strongest predictors of these abnormalities are hypertension and a history of alcohol use, as well as age. These predictive factors have been incorporated into the Multicenter Study of Perioperative Ischemia stroke-risk index, which clinicians can use to better assess the risk of adverse neurologic events. Clinical research examining the relationship between the predictive variables for neurologic adverse events and cerebral blood flow has suggested some surgical strategies for minimizing risk, such as limiting manipulation of the ascending aorta. The benefits of strategies such as using low or high mean arterial pressures and manipulating pump flow remain unclear. Off-pump coronary bypass surgery has been proposed as a means of reducing neurologic risk, but its effectiveness is unproved in this area. One pharmacologic strategy, the administration of aprotinin, has been shown to reduce the incidence of stroke in high-risk patients.

Cardiopulmonary bypass management and neurologic outcomes: an evidence-based appraisal of current practices

Neurologic complications after cardiac surgery are of growing importance for an aging surgical population. In this review, we provide a critical appraisal of the impact of current cardiopulmonary bypass (CPB) management strategies on neurologic complications. Other than the use of 20-40 microm arterial line filters and membrane oxygenators, newer modifications of the basic CPB apparatus or the use of specialized equipment or procedures (including hypothermia and "tight" glucose control) have unproven benefit on neurologic outcomes. Epiaortic ultrasound can be considered for ascending aorta manipulations to avoid atheroma, although available clinical trials assessing this maneuver are limited. Current approaches for managing flow, arterial blood pressure, and pH during CPB are supported by data from clinical investigations, but these studies included few elderly or high-risk patients and predated many other contemporary practices. Although there are promising data on the benefits of some drugs blocking excitatory amino acid signaling pathways and inflammation, there are currently no drugs that can be recommended for neuroprotection during CPB. Together, the reviewed data highlight the deficiencies of the current knowledge base that physicians are dependent on to guide patient care during CPB. Multicenter clinical trials assessing measures to reduce the frequency of neurologic complications are needed to develop evidence-based strategies to avoid increasing patient morbidity and mortality.

A multivariate Bayesian model for assessing morbidity after coronary artery surgery

Introduction

Although most risk-stratification scores are derived from preoperative patient variables, there are several intraoperative and postoperative variables that can influence prognosis. Higgins and colleagues previously evaluated the contribution of preoperative, intraoperative and postoperative predictors to the outcome. We developed a Bayes linear model to discriminate morbidity risk after coronary artery bypass grafting and compared it with three different score models: the Higgins' original scoring system, derived from the patient's status on admission to the intensive care unit (ICU), and two models designed and customized to our patient population.

Methods

We analyzed 88 operative risk factors; 1,090 consecutive adult patients who underwent coronary artery bypass grafting were studied. Training and testing data sets of 740 patients and 350 patients, respectively, were used. A stepwise approach enabled selection of an optimal subset of predictor variables. Model discrimination was assessed by receiver operating characteristic (ROC) curves, whereas calibration was measured using the Hosmer-Lemeshow goodness-of-fit test.

Results

A set of 12 preoperative, intraoperative and postoperative predictor variables was identified for the Bayes linear model. Bayes and locally customized score models fitted according to the Hosmer-Lemeshow test. However, the comparison between the areas under the ROC curve proved that the Bayes linear classifier had a significantly higher discrimination capacity than the score models. Calibration and discrimination were both much worse with Higgins' original scoring system.

Conclusion

Most prediction rules use sequential numerical risk scoring to quantify prognosis and are an advanced form of audit. Score models are very attractive tools because their application in routine clinical practice is simple. If locally customized, they also predict patient morbidity in an acceptable manner. The Bayesian model seems to be a feasible alternative. It has better discrimination and can be tailored more easily to individual institutions.

Advanced neurologic monitoring for cardiac surgery

Cardiac surgery (CS) with cardiopulmonary bypass (CPB) is currently the most common surgery in the United States. Understanding, avoiding, and preventing postoperative complications, including neurologic deficits following CS, represents a great public and economic benefit for society, especially considering our aging population. There is a critical need to identify new strategies that will prevent harmful events during and after CS. At present, experience with neurophysiologic techniques includes the ability to measure cerebral blood flow velocity/emboli and regional cerebral venous oxygen saturation by transcranial Doppler ultrasound, and by near-infrared spectroscopy, respectively. Continuous monitoring of these variables along with systemic hemodynamics will provide a better understanding of mechanisms of brain and other organ injury during CPB. Neuroprotective interventions based on multimodality neurologic monitoring would ideally eliminate postoperative complications and improve patient outcomes.

Stroke After Coronary Artery Bypass Grafting

BACKGROUND

Despite the continuing improvements in surgical and cardiopulmonary bypass techniques during cardiac surgery, stroke remains a devastating complication. This study aimed to identify the preoperative and intraoperative risk factors for developing a perioperative stroke in patients undergoing coronary artery bypass graft surgery on cardiopulmonary bypass.

METHODS

A total of 4,380 consecutive patients who received isolated coronary artery grafting on cardiopulmonary bypass between 1992 and 2002 were included. The sample contained three cardiopulmonary bypass temperature strategies: hypothermic (< 31 degrees C, n = 1,853), tepid (32-35 degrees C, n = 1,088), and normothermic (> 36 degrees C, n = 1,439). Outcome measures reported include stroke incidence, 30-day mortality, and hospital length of stay.

RESULTS

The incidence of stroke was 1.2% (n = 51). Stroke patients were older, were more likely to be diabetic, hypertensive, have creatinine levels greater than 0.12 mmol/L, and have a history of stroke than those who did not have stroke (p < 0.05). Multivariate logistic regressions identified diabetes (p = 0.01), history of stroke (p = 0.04), and older age (p = 0.05) as independent predictors of stroke for all patients. The 30-day mortality for stroke patients was ten times greater than that of those who did not suffer stroke (17.6 vs 1.7%).

CONCLUSIONS

Diabetes, history of stroke, and older age were identified as risk factors for stroke after coronary bypass; the temperature at which cardiopulmonary bypass was performed was not significant.

Low Hematocrit During Cardiopulmonary Bypass is Associated With Increased Risk of Perioperative Stroke in Cardiac Surgery

BACKGROUND

The relationship between degree of hemodilution during cardiopulmonary bypass (CPB) and perioperative stroke has not been fully elucidated. The objective of this observational study was to evaluate the relationship between nadir hematocrit during CPB and perioperative stroke while adjusting for variables known to have an association with stroke and anemia.

METHODS

Perioperative data were prospectively collected on 10,949 consecutive patients who underwent cardiac surgery with CPB from 1999 to 2004 at a quaternary care hospital. Stroke was defined as a persistent neurologic deficit, consistent with a central nervous system lesion, occurring within 30 days of operation. Stroke was classified as perioperative if patients awoke from anesthesia with neurologic symptoms and postoperative if patients awoke without symptoms. Multivariable logistic regression analysis was used to control for confounding variables to obtain the independent relationship between nadir hematocrit during CPB and perioperative stroke.

RESULTS

The prevalence of perioperative stroke was 1.0% (n = 110). An additional 50 patients had postoperative stroke. Nadir hematocrit during CPB was an independent predictor of perioperative stroke. After controlling for confounding variables, each percent decrease in hematocrit was associated with a 10% increase in the odds of suffering perioperative stroke (95% confidence interval, 4% to 18%; p = 0.002). The model was accurate (c-index = 0.85) and reliable (Hosmer-Lemeshow test p = 0.4).

CONCLUSIONS

There is an independent, direct association between degree of hemodilution during CPB and risk of perioperative stroke. Prospective randomized clinical trials comparing different degrees of hemodilution during CPB are required to determine whether this is a cause-effect relationship or a simple association.

Anesthesia and Neurocerebral Monitoring for Aortic Dissection

Patients presenting to the operating room for repair of aortic dissection are challenging in all aspects of their care. Without exception, they require a multidisciplinary team approach. This article will review some of the specific challenges faced by anesthesiologists and neurologists when confronted with such a diagnosis. Specifically, we will discuss the myriad anesthetic issues that present in the preoperative stage and continue into the postoperative period. Neurologic complications during dissection repair result in increased morbidity and mortality. A variety of neurophysiologic monitoring techniques exist that may reduce this risk and will be discussed in detail. Finally, we will present some "controversies in care," emphasizing that our respective fields continue to grow, learn, and improve what information we have on the morbidity and mortality of aortic dissection.

Intraoperative hyperglycemia and perioperative outcomes in cardiac surgery patients

OBJECTIVE

To estimate the magnitude of association between intraoperative hyperglycemia and perioperative outcomes in patients who underwent cardiac surgery.

PATIENTS AND METHODS

We conducted a retrospective observational study of consecutive adult patients who underwent cardiac surgery between June 10, 2002, and August 30, 2002, at the Mayo Clinic, a tertiary care center in Rochester, Minn. The primary independent variable was the mean intraoperative glucose concentration. The primary end point was a composite of death and infectious (sternal wound, urinary tract, sepsis), neurologic (stroke, coma, delirium), renal (acute renal failure), cardiac (new-onset atrial fibrillation, heart block, cardiac arrest), and pulmonary (prolonged pulmonary ventilation, pneumonia) complications developing within 30 days after cardiac surgery.

RESULTS

Among 409 patients who underwent cardiac surgery, those experiencing a primary end point were more likely to be male and older, have diabetes mellitus, undergo coronary artery bypass grafting, and receive insulin during surgery (P< or =.05 for all comparisons). Atrial fibrillation (n=105), prolonged pulmonary ventilation (n=53), delirium (n=22), and urinary tract infection (n=16) were the most common complications. The initial, mean, and maximal intraoperative glucose concentrations were significantly higher in patients experiencing the primary end point (P<.01 for all comparisons). In multivariable analyses, mean and maximal glucose levels remained significantly associated with outcomes after adjusting for potentially confounding variables, including postoperative glucose concentration. Logistic regression analyses indicated that a 20-mg/dL increase in the mean intraoperative glucose level was associated with an increase of more than 30% in outcomes (adjusted odds ratio, 1.34; 95% confidence Interval, 1.10-1.62).

CONCLUSION

Intraoperative hyperglycemia is an independent risk factor for complications, including death, after cardiac surgery.

Brain injury after adult cardiac surgery

Despite remarkable progress in surgical, cardiopulmonary bypass and anaesthetic techniques during the last three decades, brain damage remains an important complication of adult cardiac surgery. Effective brain protection strategies are already implemented today, but ongoing research is needed to meet the challenges faced in operating on increasingly old and disabled patients. The incidence of brain injury may be reduced by modifying the surgical procedure according to carotid duplex scanning and epiaortic echocardiography, by using techniques to reduce microembolization during cardiopulmonary bypass and by optimizing patient temperature during and after surgery. Increased knowledge will aid in choosing the best procedure or combination of procedures in each case to ensure that risks do not outweigh benefits.

The influence of hemodilution on outcome after hypothermic cardiopulmonary bypass: results of a randomized trial in infants

BACKGROUND

We hypothesized that cognitive impairment and hemodynamic instability after infant cardiac surgery with cardiopulmonary bypass might be exacerbated by hemodilution.

METHODS

In a single-center randomized trial with blinded assessment of outcomes, we compared use of 2 hemodilution protocols during hypothermic cardiopulmonary bypass with infant cardiac surgery. The primary perioperative end point was lowest cardiac index in the first 24 hours postoperatively, and primary end points at age 1 year were scores on the Psychomotor Development Index and Mental Developmental Index of the Bayley Scales.

RESULTS

Among 147 subjects, 74 were assigned to the lower-hematocrit strategy (21.5% +/- 2.9%, mean +/- SD at onset of low-flow bypass) and 73 to the higher-hematocrit strategy (27.8% +/- 3.2%). In intent-to-treat analyses the lower-hematocrit group had lower nadirs of cardiac index (P =.02), higher serum lactate levels 60 minutes after cardiopulmonary bypass (P =.03), and a greater percentage increase in total body water on the first postoperative day (P =.006). Blood product use and adverse events were similar in the 2 groups. At age 1 year (113 children), the lower-hematocrit group had worse scores on the Psychomotor Development Index (81.9 +/- 15.7 vs 89.7 +/- 14.7, P =.008), as well as more Psychomotor Development Index scores at least 2 SDs below the population mean (16/56 [29%] vs 5/53 [9%], P =.01). The groups had similar Mental Developmental Index scores and findings on neurologic examination. Inferences using hematocrit as a continuous variable were similar to those based on intent-to-treat analyses.

CONCLUSIONS

Hemodilution to a hematocrit level in wide use for cardiopulmonary bypass and thought to be safe is associated with adverse perioperative and developmental outcomes in infants.

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

OBJECTIVE

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

DESIGN

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

RESULTS

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

CONCLUSIONS

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

The impact of asymptomatic carotid artery disease on the intraoperative course of coronary artery bypass surgery

Asymptomatic carotid artery stenosis (CAS) may result in neurological injury after coronary artery bypass surgery, but routine preoperative carotid screening is not undisputed. We studied whether routinely determined carotid duplex results, beyond detecting high-risk patients, additionally influence intraoperative course. One hundred and eight patients without new signs of impaired cerebral circulation were investigated. Anesthesiology, perfusionist records, and patient files were reviewed for patient characteristics, intraoperative variables and postoperative neurological sequelae. There was a higher incidence of prior cerebrovascular events and peripheral artery disease in CAS patients (p < 0.05). Pulsatile flow was employed more frequently in this group (p < 0.05). Severe hyperventilation, hyperglycemia, hemodilution, hyperthermia, and lactacidosis were avoided in both groups. However, labile hemodynamics of CAS patients required more corrective interventions (p < 0.05). There was also a tendency toward greater mortality. Stroke and transient ischemic attack (TIA) occurred in two patients without CAS. Since CAS was associated with a greater degree of cardiovascular instability requiring frequent measures to control hemodynamics, positive duplex results should heighten vigilance. Although CAS does not appear to be the major source of cerebral ischemia, it involves significant comorbidity.

Coronary-artery bypass surgery and the brain: persisting concerns

Mortality after coronary-artery bypass surgery (CABS) has fallen steadily over recent years. Concern remains, however, about the effect of this surgery on the brain. The problem of brain damage after CABS is multifactorial, involving microembolism, disturbed perfusion, metabolic derangement, and inflammatory responses. Microemboli numbers have been linked to the likelihood of neuropsychological deterioration after surgery. Risk factors for cerebral changes after CABS include older age, gender, neurological disease, diabetes, and calcification of the aorta. These risk factors are important because, in comparison with the early 1990s, patients undergoing CABS are now older and tend to have a greater number of comorbid conditions. Changes in surgical technique, such as the introduction of arterial-line filters and membrane oxygenators, have led to a reduction of both microemboli and neuropsychological disturbance. However, the problem persists, prompting further studies on surgical technique and neuroprotective strategies.

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.