Attempted control of hyperglycemia during cardiopulmonary bypass fails to improve neurologic or neurobehavioral outcomes in patients without diabetes mellitus undergoing coronary artery bypass grafting

Postoperative cognitive dysfunction: a concept analysis

BACKGROUND

Post-operative cognitive dysfunction (POCD) is a concern for clinicians that often presents post-surgery where generalized anesthesia has been used. Its prevalence ranges from 36.6% in young adults to 42.4% in older individuals. Conceptual clarity for POCD is lacking in the currently body literature. Our two-fold purpose of this concept analysis was to (1) critically appraise the various definitions, while also providing the best definition, of POCD and (2) narratively synthesize the attributes, surrogate or related terms, antecedents (risk factors), and consequences of the concept.

METHOD

The reporting of our review was guided by the PRISMA statement and the 6-step evolutionary approach to concept analysis developed by Rodgers. Three databases, including Medline, CINAHL, and Web of Science, were searched to retrieve relevant literature on the concept of POCD. Two independent reviewers conducted abstract and full-text screening, data extraction, and appraisal. The review process yielded a final set of 86 eligible articles.

RESULT

POCD was defined with varying severities ranging from subtle-to-extensive cognitive changes (1) affecting single or multiple cognitive domains that manifest following major surgery (2), is transient and reversible, and (3) may last for several weeks to years. The consequences of POCD may include impaired quality of life, resulting from withdrawal from the labor force, increased patients' dependencies, cognitive decline, an elevated risk of dementia, rising healthcare costs, and eventual mortality.

CONCLUSION

This review resulted in a refined definition and comprehensive analysis of POCD that can be useful to both researchers and clinicians. Future research is needed to refine the operational definitions of POCD so that they better represent the defining attributes of the concept.

Perioperative Glycemic Management in Cardiac Surgery: A Narrative Review

Diabetes and hyperglycemic events in cardiac surgical patients are associated with postoperative morbidity and mortality. The causes of dysglycemia, the abnormal fluctuations in blood glucose concentrations, in the perioperative period include surgical stress, surgical techniques, medications administered perioperatively, and patient factors. Both hyperglycemia and hypoglycemia lead to poor outcomes after cardiac surgery. While trying to control blood glucose concentration tightly for better postoperative outcomes, hypoglycemia is the main adverse event. Currently, there is no definite consensus on the optimum perioperative blood glucose concentration to be maintained in cardiac surgical patients. This review provides an overview of perioperative glucose homeostasis, the pathophysiology of dysglycemia, factors that affect glycemic control in cardiac surgery, and current practices for glycemic control in cardiac surgery.

Intraoperative Glycemic Variability and Mean Glucose are Predictors for Postoperative Delirium After Cardiac Surgery: A Retrospective Cohort Study

Purpose

Postoperative delirium (POD) is a common but serious complication after cardiac surgery and is associated with various short- and long-term outcomes. In this study, we investigated the effects of intraoperative glycemic variability (GV) and other glycemic variables on POD after cardiac surgery.

Patients and Methods

A retrospective single-center cohort analysis was conducted using data from electronic medical record from 2018 to 2020. A total of 705 patients undergoing coronary artery bypass graft surgery and/or valve surgery, and/or aortic replacement surgery were included in the analysis. Intraoperative GV was assessed with a coefficient of variation (CV), which was defined as the standard deviation of five intraoperative blood glucose measurements divided by the mean. POD assessment was performed three times a day in the ICU and twice a day in the ward until discharge by trained medical staff. POD was diagnosed if any of the Confusion Assessment Method for the Intensive Care Unit was positive in the ICU, and the Confusion Assessment Method was positive in the ward. Multivariable logistic regression was used to identify associations between intraoperative GV and POD.

Results

POD occurred in 306 (43.4%) patients. When intraoperative glycemic CV was compared as a continuous variable, the delirium group had higher intraoperative glycemic CV than the non-delirium group (22.59 [17.09, 29.68] vs 18.19 [13.00, 23.35], p < 0.001), and when intraoperative glycemic CV was classified as quartiles, the incidence of POD increased as intraoperative glycemic CV quartiles increased (first quartile 29.89%; second quartile 36.67%; third quartile 44.63%; and fourth quartile 62.64%, p < 0.001). In the multivariable logistic regression model, patients in the third quartile of intraoperative glycemic CV were 1.833 times (OR 1.833, 95% CI: 1.132–2.967, p = 0.014), and patients in the fourth quartile of intraoperative glycemic CV were 3.645 times (OR 3.645, 95% CI: 2.235–5.944, p < 0.001) more likely to develop POD than those in the first quartile of intraoperative glycemic CV.

Conclusion

Intraoperative blood glucose fluctuation, manifested by intraoperative GV, is associated with POD after cardiac surgery. Patients with a higher intraoperative GV have an increased risk of POD.

2021 ACC/AHA/SCAI Guideline for Coronary Artery Revascularization: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines

AIM

The guideline for coronary artery revascularization replaces the 2011 coronary artery bypass graft surgery and the 2011 and 2015 percutaneous coronary intervention guidelines, providing a patient-centric approach to guide clinicians in the treatment of patients with significant coronary artery disease undergoing coronary revascularization as well as the supporting documentation to encourage their use.

METHODS

A comprehensive literature search was conducted from May 2019 to September 2019, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, the Cochrane Collaboration, CINHL Complete, and other relevant databases. Additional relevant studies, published through May 2021, were also considered.

STRUCTURE

Coronary artery disease remains a leading cause of morbidity and mortality globally. Coronary revascularization is an important therapeutic option when managing patients with coronary artery disease. The 2021 coronary artery revascularization guideline provides recommendations based on contemporary evidence for the treatment of these patients. The recommendations present an evidence-based approach to managing patients with coronary artery disease who are being considered for coronary revascularization, with the intent to improve quality of care and align with patients' interests.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

PROSPERO REGISTRATION NUMBER

CRD42019140844.

Insulin Use and Clinical Outcomes in Patients Undergoing Coronary Artery Bypass Graft Surgery

Objective

To describe insulin use and postoperative glucose control in patients undergoing coronary artery bypass graft (CABG) surgery.

Methods

We examined 2,390 patients with and without diabetes enrolled in the Contemporary Analysis of Perioperative Cardiovascular Surgical Care (CAPS-Care) Study who underwent CABG surgery (01/2004 - 06/2005) to describe postoperative insulin use, variation in insulin use across different hospitals, and associated in-hospital complications and clinical outcomes. Logistic regression was used to assess the adjusted relationship between insulin use and clinical outcomes.

Results

Overall, insulin was used in 82% (n=1,959) of patients, including 95% (n=1,203) with diabetes (n=1,258) and 67% (n=756) without diabetes (n=1,132). Continuous insulin was used in 35.5% of patients in the operating room and in 56% in the intensive care unit. Continuous insulin use varied significantly among centers from 8-100% in patients with diabetes. When compared with all patients not receiving insulin, insulin use in patients without diabetes was associated with a higher rate of death or major complication (adjusted odds ratio [OR]=1.54; 95% confidence interval [CI] 1.15-2.04; P=0.003). In patients with diabetes, insulin use was not associated with a higher risk of adverse outcomes (adjusted OR=1.01; 95% CI 0.52-1.98; P=0.98).

Conclusion

The postoperative use of insulin is high among CABG patients in the United States of America. Insulin use in patients without diabetes was associated with worse clinical outcomes compared to patients (both with and without diabetes) who did not receive insulin. Further investigation is needed to determine the optimal use of postoperative insulin after CABG.

Outcomes of type A intramural hematoma: Influence of diabetes mellitus

OBJECTIVES

We aimed to investigate whether uncomplicated type A intramural hematoma (IMHA) patients with type 2 diabetes mellitus (DM) who underwent a "wait-and-watch strategy" and tight glycemic control had similar clinical outcomes as patients without DM who received the same treatment strategy.

METHODS

Between January 2010 and December 2016, uncomplicated IMHA patients with and without diabetes mellitus were included and were propensity score-matched to improve the balance between the two groups. Cox proportional hazard models were constructed to identify the specific factors associated with aorta-related mortality. The Fine-Gray model for the competing risk analysis was used to estimate the aorta-related and nonaorta-related mortality in different groups during the follow-up period.

RESULTS

A total of 109 IMHA patients were included in this study, and 66 patients were included after matching. Patients without DM experienced significantly more aorta-related adverse events (51.6% vs 13.3%; P = .001) and reinterventions than patients in the DM group (29.0% vs 6.7%; P = .023). Cox regression analysis revealed that a higher matrix metalloproteinase-9 level (hazard ratio [HR], 1.70; 95% confidence interval [CI], 1.39-2.09; P < .001) and larger maximum aortic diameter (HR, 1.41; 95% CI, 1.11-1.80; P = .005) were associated with higher aorta-related mortality. The competing risk analysis revealed a significantly higher aorta-related mortality during the follow-up period in the no DM group than in the DM group (36.4%; 95% CI, 11.6%-82.3%; P = .0294).

CONCLUSIONS

Uncomplicated IMHA patients with DM (receiving the "wait-and-watch strategy" and tight glycemic control) may have lower aorta-related mortality and rates of aorta-related adverse events and reinterventions than the no DM group.

Perioperative Management of the Diabetic Patient Referred to Cardiac Surgery

Currently there is a progressive increase in the prevalence of diabetes in a referred for cardiovascular surgery. Benefits of glycemic management (< 180 mg/dL) in diabetic patients compared to patients without diabetes in perioperative cardiac surgery. The purpose of this study is to present recommendations based on international evidence and adapted to our clinical practice for the perioperative management of hyperglycemia in adult patients with and without diabetes undergoing cardiovascular surgery. This update is based on the latest current literature derived from articles and guidelines regarding perioperative management of diabetic patients to cardiovascular surgery.

Neurocognitive Function after Cardiac Surgery: From Phenotypes to Mechanisms

For half a century, it has been known that some patients experience neurocognitive dysfunction after cardiac surgery; however, defining its incidence, course, and causes remains challenging and controversial. Various terms have been used to describe neurocognitive dysfunction at different times after cardiac surgery, ranging from "postoperative delirium" to "postoperative cognitive dysfunction or decline." Delirium is a clinical diagnosis included in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). Postoperative cognitive dysfunction is not included in the DSM-5 and has been heterogeneously defined, though a recent international nomenclature effort has proposed standardized definitions for it. Here, the authors discuss pathophysiologic mechanisms that may underlie these complications, review the literature on methods to prevent them, and discuss novel approaches to understand their etiology that may lead to novel treatment strategies. Future studies should measure both delirium and postoperative cognitive dysfunction to help clarify the relationship between these important postoperative complications.

Glycemic control in patients undergoing coronary artery bypass graft surgery: Clinical features, predictors, and outcomes

PURPOSE

Critically ill patients with hyperglycemia have worse prognosis. The degree to which glycemic control is achieved following CABG surgery and the association with clinical outcomes is not well understood.

MATERIALS AND METHODS

We studied patients undergoing higher risk CABG surgery at 55 US hospitals. Good glycemic control was defined as 70-180mg/dL in the first 24h postoperatively. Generalized estimating equations logistic regression models were used to assess the relationship between glycemic control and clinical outcomes after adjusting for baseline characteristics.

RESULTS

Among 2032 patients only 297 (15%) had good glycemic control in the perioperative period, with 2% having at least one BS below 70, 63% having at least one BS above 180, and 9% having both. Patients with good glycemic control had lower rates of the risk-adjusted composite outcome of mortality and major complications (OR=0.66; 95% CI 0.46-0.93, p=0.02). Hypoglycemic events occurred in 250 (12%) patients, ranging among hospitals from 2% to 58%, p<0.001 and was not associated with hospitals' overall rate of good glucose control.

CONCLUSIONS

Achieving glycemic control following high risk CABG was associated with lower operative mortality and morbidity, yet achieved in only 15% of patients. Hospitals varied considerably in their ability to achieve good glycemic control.

Blood glucose management in the patient undergoing cardiac surgery: A review

Both diabetes mellitus and hyperglycemia per se are associated with negative outcomes after cardiac surgery. In this article, we review these associations, the possible mechanisms that lead to adverse outcomes, and the epidemiology of diabetes focusing on those patients requiring cardiac surgery. We also examine outpatient and perioperative management of diabetes with the same focus. Finally, we discuss our own efforts to improve glycemic management of patients undergoing cardiac surgery at our institution, including keys to success, results of implementation, and patient safety concerns.

Safety and efficacy of intensive intraoperative glycaemic control in cardiopulmonary bypass surgery: a randomised trial

BACKGROUND

This study aimed to determine the safety and efficacy of intraoperative intensive glycaemic treatment with modified glucose-insulin-potassium solution by hyperinsulinemic normoglycaemic clamp in cardiopulmonary bypass surgery patients. We hypothesised that the treatment would reduce infection rates in this group of patients.

METHODS

A prospective, randomised, double-blind trial was conducted in cardiopulmonary bypass surgery patients. A total of 199 adult patients (out of a planned 400) were randomly allocated to intensive or conventional treatment with target glucose levels of 4.4-8.3 mmol/l and < 13.8 mmol/l, respectively. The primary outcomes were clinical infection and cytokine levels, including interleukin (IL)-6 and IL-10. The secondary outcomes were morbidity and mortality.

RESULTS

The study was terminated early because of safety concerns (hypoglycaemia). The clinical post-operative infection rate was 17% in the intensive group and 13% in the conventional group (P = 0.53). The proportion of patients with hypoglycaemia was significantly higher in the intensive group (23%) compared with the conventional group (3%) (P < 0.001). Morbidity and mortality rates were similar for both groups. Anaesthetic duration > 2 h (vs. ≤ 2 h), pre-operative IL-6 level > 15 pg/ml (vs. ≤ 15 pg/ml) and post-operative IL-6 level 56-110 pg/ml (vs. ≤ 55 pg/ml) were independent predictors for post-operative infection.

CONCLUSIONS

Intraoperative intensive glycaemic treatment significantly increased the risk of hypoglycaemia, but its effect on post-operative infection by clinical assessment could not be determined. Anaesthetic duration, pre-operative and post-operative IL-6 levels can independently predict post-operative infection.

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.

[What should no longer be seen when performing a CPB]

Cardiac surgery and cardiopulmonary bypass (CPB) have made significant progress in recent years. Despite these efforts, adverse events continue to occur during surgery. From recent studies of incidents and accidents during CPB, this article focuses on critical recommendations to respect when in charge of a CPB. Some facts are based only on data unsupported by scientific research. Others have not proven their benefit in terms of postoperative morbidity or mortality. The management of anticoagulation, hematocrit, pump flow, and the temperature is discussed. Finally, the importance of teamwork especially in terms of cohesion and communication is highlighted.

Implementation of an intraoperative glycemic control protocol for cardiac surgery in a high-acuity academic medical center: an observational study

STUDY OBJECTIVE

To examine the effect on morbidity and mortality of an established intraoperative insulin protocol in cardiac surgical patients.

DESIGN

Retrospective observational study.

SETTING

Single-center, 782 bed, metropolitan academic hospital.

PATIENTS

1,616 adult patients undergoing cardiac surgical procedures with cardiopulmonary bypass (CPB).

INTERVENTIONS

An intraoperative, intravenous (IV) insulin protocol designed to maintain blood glucose values less than 150 mg/dL was implemented.

MEASUREMENTS

Blood glucose was evaluated on entry to the operating room, every 30 minutes during CPB, and at least once after discontinuation of CPB. Blood glucose values were followed postoperatively, as dictated by institutional policy.

MAIN RESULTS

Intraoperative predictors of 30-day mortality using multivariate logistic regression included hyperglycemia on initiation of CPB (OR 1.0, P = 0.05). The strongest predictor of 30-day mortality was the development of postoperative renal failure requiring hemodialysis (OR 3.26, P = 0.001).

CONCLUSIONS

Implementation of an intraoperative IV insulin protocol, while associated with improved glycemic control, was not associated with improved outcomes. While improved glycemic control on initiating CPB was associated with decreased 30-day mortality, the effect was small. Implementation of our insulin protocol was highly associated with decreased renal failure postoperatively. Further prospective studies are warranted to better establish causality.

Glycemic Control during Coronary Artery Bypass Graft Surgery

Hyperglycemia, which occurs in the perioperative period during cardiac surgery, has been shown to be associated with increased morbidity and mortality. The management of perioperative hyperglycemia during coronary artery bypass graft surgery and all cardiac surgical procedures has been the focus of intensive study in recent years. This report will paper the pathophysiology responsible for the detrimental effects of perioperative hyperglycemia during cardiac surgery, show how continuous insulin infusions in the perioperative period have improved outcomes, and discuss the results of trials designed to determine what level of a glycemic control is necessary to achieve optimal clinical outcomes.

How important is glycemic control during coronary artery bypass?

In summary, poor perioperative glycemic control in patients undergoing CABG is associated with increased morbidity and mortality. Maintaining serum glucose less than or equal to 180 mg/dL in patients with diabetes during CABG reduces morbidity and mortality, lowers the incidence of wound infections, reduces hospital length of stay, and enhances long-term survival. In nondiabetic patients undergoing CABG surgery, maintaining serum glucose less than 180 mg/dL has also resulted in improved perioperative outcomes. More aggressive glycemic control (80-120 mg/dL) provides no added improvement in CABG patients with less than or equal to 3 days of ICU care in the absence of ventilatory support or multiorgan failure. Although the precise value for achieving glycemic control in the perioperative period is the subject of much debate, the benefits of perioperative glycemic control with continuous insulin infusions in patients undergoing CABG is no longer debatable.

Management of hyperglycemia during the perioperative period

Hyperglycemia is frequently encountered in the inpatient setting and is distinctly associated with poor clinical outcomes. Recent literature suggests an association between stringent glycemic control and increased mortality, thus keeping optimal glycemic targets a relevant subject of debate. In the surgical population, hyperglycemia with or without diabetes mellitus may be unrecognized. Factors contributing to hyperglycemia in the hospital include critical illness, use of certain drugs, use of enteral or parenteral nutrition, and variability in oral or nutritional intake as can occur when patients are prepared for procedures or surgery. A sensible approach to managing hyperglycemia in this population includes preoperative recognition of diabetes mellitus and risks for inpatient hyperglycemia. Judicious control of glycemia during the pre-, intra-, and postoperative time periods with avoidance of hypoglycemia mandates the need for a strategy for patient management that extend to time of discharge. We review the consequences of uncontrolled perioperative hyperglycemia, discuss current clinical guidelines and recent controversies, and provide practical tools for glycemic control in the surgical population.

Perioperative management of blood glucose during open heart surgery in infants and children

The perioperative management of blood glucose has been controversial since clinical associations between hyperglycemia and adverse outcomes were first reported more than two decades ago. Despite some early evidence supporting a causal relationship between hyperglycemia and adverse outcomes, prospective trials of tight glycemic control have been inconclusive, except in selected populations, like adult diabetics. These trials have consistently reported dramatic increases in the incidence and severity of hypoglycemia, which may also have associated adverse outcomes. Bedside glucose monitors typically used to manage glucose have increasingly been found to introduce systematic inaccuracies. Relevant studies of infants and children undergoing cardiac surgery are considerably fewer in number, requiring clinicians to extrapolate from other clinical conditions and patient populations.

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.

Neurocognitive dysfunction following cardiac surgery

Postoperative neurocognitive decline (POCD) is the most frequently reported form of brain injury in the cardiac surgery setting. Even though most patients recover over a period of several months, recovery is variable and often transient, and early decline may be a marker of neurocognitive dysfunction after several years. Recent studies, however, suggest that late neurocognitive decline after coronary artery bypass graft surgery may not be specific to the use of cardiopulmonary bypass. Large prospective, longitudinal trials with appropriate controls remain necessary to identify how patient characteristics, disease progression, and surgical and anesthetic technique contribute to aging-related neurocognitive decline. This article reviews the current literature on the etiology of POCD following cardiac surgery, discusses strategies to reduce patient risk, and provides some insight into some controversies that merit continued investigation.

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.

Peri-operative hyperglycemia: a consideration for general surgery?

BACKGROUND

Intraoperative hyperglycemia in cardiac and neurosurgical patients is significantly associated with morbidity. Little is known about the perioperative glycemic profile or its impact in other surgical populations or in nondiabetic patients.

METHODS

A systematic review of blood glucose values during major general surgical procedures reported since 1980 was conducted. Data extracted included blood glucose measures, study sample size, gender distribution, age grouping, study purpose, surgical procedure, anesthetic details, and infusion regime. Excluded studies were those with subjects with diabetes insipidus, insulin-treated diabetes, renal or hepatic failure, adrenal gland tumors or dysfunction, pregnancy, and emergency or trauma surgery.

RESULTS

Blood glucose levels rose significantly with the induction of anesthesia (P < .001) in nondiabetic patients. At incision, 2 hours, 4 hours, and 6 hours, 30%, 40%, 38%, and 40% of studies, respectively, reported hyperglycemia.

CONCLUSIONS

Factors that confound or protect against significant rises in perioperative glycemic levels in nondiabetic patients were identified. The findings facilitate investigating the impact of hyperglycemia on general surgical outcomes.

Scientific principles and clinical implications of perioperative glucose regulation and control

Development of hyperglycemia after major operations is very common and is modulated by many factors. These factors include perioperative metabolic state, intraoperative management of the patient, and neuroendocrine stress response to surgery. Acute insulin resistance also develops perioperatively and contributes significantly to hyperglycemia. Hyperglycemia is associated with poor outcomes in critically ill and postsurgical patients. A majority of the investigations use the term "hyperglycemia" very loosely and use varying thresholds for initiating treatment. Initial studies demonstrated improved outcomes in critically ill, postsurgical patients who received intensive glycemic control (IGC) (target serum glucose <110 mg/dL). These results were quickly extrapolated to other clinical areas, and IGC was enthusiastically recommended in the perioperative period. However, there are few studies investigating the value of intraoperative glycemic control. Moreover, recent prospective trials have not been able to show the benefit of IGC; neither an appropriate therapeutic glycemic target nor the true efficacy of perioperative glycemic control has been fully determined. Practitioners should also appreciate technical nuances of various glucose measurement techniques. IGC increases the risk of hypoglycemia significantly, which is not inconsequential in critically ill patients. Until further specific data are accumulated, it is prudent to maintain glucose levels <180 mg/dL in the perioperative period, and glycemic control should always be accompanied by close glucose monitoring.

Pilot evaluation of a prototype critical care blood glucose monitor in normal volunteers

BACKGROUND

Availability of a highly accurate in-hospital automated blood glucose (BG) monitor could facilitate implementation of intensive insulin therapy protocols through effective titration of insulin therapy, improved BG control, and avoidance of hypoglycemia. We evaluated a functional prototype BG monitor designed to perform frequent automated blood sampling for glucose monitoring.

METHODS

Sixteen healthy adult volunteer subjects had intravenous catheter insertions in a forearm or hand vein and were studied for 8 hours. The prototype monitor consisted of an autosampling unit with a precise computer-controlled reversible syringe pump and a glucose analytical section. BG was referenced against a Yellow Springs Instrument (YSI) laboratory analyzer. Sampling errors for automated blood draws were assessed by calculating the percent of failed draws, and BG data were analyzed using the Bland and Altman technique.

RESULTS

Out of 498 total sample draws, unsuccessful draws were categorized as follow: 11 (2.2%) were due to autosampler technical problems, 21 (4.2%) were due to catheter-related failures, and 37 (7.4%) were BG meter errors confirmed by a glucometer-generated error code. Blood draw difficulties or failures related to the catheter site (e.g., catheter occlusion or vein collapse) occurred in 6/15 (40%) subjects. Mean BG bias versus YSI was 0.20 +/- 12.6 mg/dl, and mean absolute relative difference was 10.4%.

CONCLUSIONS

Automated phlebotomy can be performed in healthy subjects using this prototype BG monitor. The BG measurement technology had suboptimal accuracy based on a YSI reference. A more accurate BG point-of-care testing meter and strip technology have been incorporated into the future version of this monitor. Development of such a monitor could alleviate the burden of frequent BG testing and reduce the risk of hypoglycemia in patients on insulin therapy.

Brain protection in cardiac surgery

Brain injury is a major source of patient morbidity after cardiac surgery, and is associated with prolonged hospitalization, excessive operative mortality, high hospital costs, and altered quality of life. Frequency and the clinical manifestations depend on multiple factors, including the completeness and timing of neurologic testing. Ischemic brain infarctions may or may not be associated with stroke or postoperative neurocognitive dysfunction, but the long-term implications of these lesions on neurologic function have not yet been extensively evaluated. This article reviews the current views on the pathophysiologic basis of cerebral injury after cardiac surgery and provides a summary of measures aimed at reducing its occurrence.

Dynamic tight glycemic control during and after cardiac surgery is effective, feasible, and safe

BACKGROUND

Tight blood glucose control reduces mortality and morbidity in critically ill patients, but intraoperative glucose control during cardiac surgery is often difficult, and risks hypoglycemia. In this study, we evaluated the safety and efficacy of a nurse-driven insulin protocol (the Aalst Glycemia Insulin Protocol) for achieving a target glucose level of 80-110 mg/dL during cardiac surgery and in the intensive care unit (ICU).

METHODS

We included 483 nondiabetics and 168 diabetics scheduled for cardiac surgery with cardiopulmonary bypass. To anticipate rapid perioperative changes in insulin requirement and/or sensitivity during surgery, we developed a dynamic algorithm presented in tabular form, with rows representing blood glucose ranges and columns representing insulin dosages based on the patients' insulin sensitivity. The algorithm adjusts insulin dosage based on blood glucose level and the projected insulin sensitivity (e.g., reduced sensitivity during cardiopulmonary bypass and normalizing sensitivity after surgery).

RESULTS

A total of 18,893 blood glucose measurements were made during and after surgery. During surgery, the mean glucose level in nondiabetic patients was within targeted levels except during (112 +/- 17 mg/dL) and after rewarming (113 +/- 19 mg/dL) on cardiopulmonary bypass. In diabetics, blood glucose was decreased from 121 +/- 40 mg/dL at anesthesia induction to 112 +/- 26 mg/dL at the end of surgery (P < 0.05), with 52.9% of patients achieving the target. In the ICU, the mean glucose level was within targeted range at all time points, except for diabetics upon ICU arrival (113 +/- 24 mg/dL). Of all blood glucose measurements (operating room and ICU), 68.0% were within the target, with 0.12% of measurements in nondiabetics and 0.18% in diabetics below 60 mg/dL. Hypoglycemia < 50 mg/dL was avoided in all but four (0.6%) patients (40 mg/dL was the lowest observed value).

CONCLUSIONS

The Aalst Glycemia Insulin Protocol is effective for maintaining tight perioperative blood glucose control during cardiac surgery with minimal risk of hypoglycemia.

Neuroprotection during cardiac surgery

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

Effect of perioperative insulin infusion on surgical morbidity and mortality: systematic review and meta-analysis of randomized trials.7

OBJECTIVE

To conduct a systematic review and meta-analysis of randomized controlled trials (RCTs) to evaluate the effect of perioperative insulin infusion on outcomes important to patients.

PATIENTS AND METHODS

We used 6 search strategies including an electronic database search of MEDLINE, EMBASE, and Cochrane CENTRAL, from their inception up to May 1, 2006, and included RCTs of perioperative insulin infusion (with or without glucose targets) measuring outcomes in patients undergoing any surgery. Pairs of reviewers working independently assessed the methodological quality and characteristics of included trials and abstracted data on perioperative outcomes (ie, outcomes that occurred during hospitalization or within 30 days of surgery).

RESULTS

We identified 34 eligible trials. In the 14 trials that assessed mortality, there were 68 deaths among 2192 patients randomized to insulin infusion compared with 98 deaths among 2163 patients randomized to control therapy (random-effects pooled relative risk, 0.69; 95% confidence interval [CI], 0.51-0.94; 99% CI, 0.46-1.04; I2, 0%; 95% CI, 0.0%-47.4%). Hypoglycemia increased in the intensively treated group (20 trials, 119/1470 patients in insulin infusion vs 48/1476 patients in control group; relative risk, 2.07; 95% CI, 1.29-3.32; 99% CI, 1.09-3.88; I2, 31.5%; 95% CI, 0.0%-59.0%). No significant effect was seen in any other outcomes. The available mortality data represent only 40% of the optimal information size required to reliably detect a plausible treatment effect; potential methodological and reporting biases weaken inferences.

CONCLUSION

Perioperative insulin infusion may reduce mortality but increases hypoglycemia in patients who are undergoing surgery; however, mortality results require confirmation in large and rigorous RCTs.

Mechanisms of cerebral injury from cardiac surgery

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