Maintenance of Normoglycemia During Cardiac Surgery

Metabolic disturbance affects postoperative cognitive function in patients undergoing cardiopulmonary bypass

OBJECTIVES

Postoperative delirium is a common neuropsychiatric syndrome after coronary artery bypass grafting (CABG). We aimed to assess and compare clinical outcomes of CABG patients with delirium with a specific focus on the blood biochemical parameters.

METHODS

This investigation was carried out on the 90 eligible patients undergoing CABG. Delirium was measured using the Neecham confusion scale and assessed patients were divided into two groups of delirium (n = 43) and non-delirium (n = 47). Preoperative variables and intraoperative and postoperative outcomes were compared.

RESULTS

Delirium patients were older (p = 0.003) and had longer intubation time (p = 0.003). Non-delirium patients obtained a significantly higher Neecham confusion score (p = 0.001), and delirium patients experienced a hyperglycemic state at intraoperative (p = 0.004), intubation (p = 0.03), and extubation time (p = 0.02). Lower value of pH was seen at intubation (p = 0.03) and extubation periods (p = 0.001) in delirium group. A significant difference in base excess was observed between two groups at intubation (p = 0.04) and extubation periods (p = 0.004). Potassium level showed a significant decrease in delirium group at intubation (p = 0.01) and extubation periods (p = 0.001). Multivariate regression indicated that aging (OR = 1.08, p = 0.01), narcotic consumption (OR = 3.27, p = 0.05), DM (OR = 3.03, p=0.03), and prolonged intubation (OR = 1.18, p = 0.03) are predictors of delirium. Postoperative hyperglycemia (OR = 1.01, p = 0.002), low pH value (OR = 2.62, p = 0.02), and low potassium level (OR = 3.25, p = 0.03) are associated with development of delirium.

CONCLUSIONS

Postoperative metabolic disturbance and electrolyte imbalances are closely related to the development of delirium after CABG and need to be considered more carefully. Aging, DM, and preoperative use of narcotics are strong predictors of delirium following CABG.

Hyperinsulinemic Normoglycemia during Cardiac Surgery Reduces a Composite of 30-day Mortality and Serious In-hospital Complications: A Randomized Clinical Trial

BACKGROUND

Hyperinsulinemic normoglycemia augments myocardial glucose uptake and utilization. We tested the hypothesis that hyperinsulinemic normoglycemia reduces 30-day mortality and morbidity after cardiac surgery.

METHODS

This dual-center, parallel-group, superiority trial randomized cardiac surgical patients between August 2007 and March 2015 at the Cleveland Clinic, Cleveland, Ohio, and Royal Victoria Hospital, Montreal, Canada, to intraoperative glycemic management with (1) hyperinsulinemic normoglycemia, a fixed high-dose insulin and concomitant variable glucose infusion titrated to glucose concentrations of 80 to 110 mg · dl; or (2) standard glycemic management, low-dose insulin infusion targeting glucose greater than 150 mg · dl. The primary outcome was a composite of 30-day mortality, mechanical circulatory support, infection, renal or neurologic morbidity. Interim analyses were planned at each 12.5% enrollment of a maximum 2,790 patients.

RESULTS

At the third interim analysis (n = 1,439; hyperinsulinemic normoglycemia, 709, standard glycemic management, 730; 52% of planned maximum), the efficacy boundary was crossed and study stopped per protocol. Time-weighted average glucose concentration (means ± SDs) with hyperinsulinemic normoglycemia was 108 ± 20 versus 150 ± 33 mg · dl with standard glycemic management, P < 0.001. At least one component of the composite outcome occurred in 49 (6.9%) patients receiving hyperinsulinemic normoglycemia versus 82 (11.2%) receiving standard glucose management (P < efficacy boundary 0.0085); estimated relative risk (95% interim-adjusted CI) 0.62 (0.39 to 0.97), P = 0.0043. There was a treatment-by-site interaction (P = 0.063); relative risk for the composite outcome was 0.49 (0.26 to 0.91, P = 0.0007, n = 921) at Royal Victoria Hospital, but 0.96 (0.41 to 2.24, P = 0.89, n = 518) at the Cleveland Clinic. Severe hypoglycemia (less than 40 mg · dl) occurred in 6 (0.9%) patients.

CONCLUSIONS

Intraoperative hyperinsulinemic normoglycemia reduced mortality and morbidity after cardiac surgery. Providing exogenous glucose while targeting normoglycemia may be preferable to simply normalizing glucose concentrations.

Akt is a critical node of acute myocardial insulin resistance and cardiac dysfunction after cardiopulmonary bypass

AIMS

Acute myocardial insulin resistance is an independent risk factor for patients who undergo cardiac surgery with cardiopulmonary bypass (CPB). However, the underlying mechanism of insulin resistance during CPB has not been fully investigated.

MATERIALS AND METHODS

To explore the role of myocardial insulin resistance on the cardiac function and its underlying mechanism, CPB operation and pharmacological intervention were applied in mini pigs, and myocardial insulin signaling, glucose uptake, ATP production and cardiac function were examined.

KEY FINDINGS

Our data showed that CPB elicited not only hyperglycemia and hyperinsulinemia, but also inactivated Akt, and impaired the transposition of membrane glucose transporter-4 (GLUT-4), reduced glucose uptake and ATP production in the myocardium as well, which in turn was accompanied with cardiac dysfunction. Meanwhile, linear correlations were established among reduced myocardial glucose uptake, ATP production, and depressed cardiac systolic or diastolic function. Reactivation of Akt by SC79, an Akt agonist, partially alleviated myocardial insulin resistance and restored post CPB cardiac function via augmenting myocardial glucose uptake and ATP production.

SIGNIFICANCE

These findings revealed that acute myocardial insulin resistance due to inactivation of Akt played a key role in cardiac dysfunction post CPB via suppressing glucose metabolism related energy supply.

Parenteral amino acid supplementation with high-dose insulin prevents hypoaminoacidemia during cardiac surgery

OBJECTIVES

Surgery triggers a stress response that produces insulin resistance and hyperglycemia. During cardiac surgery, the administration of high-dose insulin along with dextrose titration maintains normoglycemia, but dramatically decreases plasma amino acids (AAs) compared with preoperative fasting levels. Hypoaminoacidemia limits protein synthesis and prevents anabolic responses after surgery. We investigated whether parenteral infusion of AAs during and immediately after cardiac surgery would prevent hypoaminoacidemia in patients who receive high-dose insulin therapy.

METHODS

Sixteen patients undergoing coronary artery bypass grafting surgery were randomly allocated to receive AAs with % kcal equivalent to either 20% (n = 8) or 35% (n = 8) of their measured resting energy expenditure (REE). Insulin was infused at a constant rate of 5 mU/(kg × min), whereas dextrose was titrated to maintain normoglycemia during and until 5 h after surgery. Plasma AA concentrations were measured at baseline before and after surgery.

RESULTS

Compared with the 20% AA group after surgery, AA concentrations were significantly higher in the 35% AA group for 12 of 20 AAs (P < 0.032), including all branched-chain AAs. In the 20% AA group, total essential AAs decreased by 21% and nonessential AAs decreased by 14% after surgery compared with preoperative fasting levels. In contrast, giving 35% AAs prevented this unfavorable decrease in AAs, and in fact allowed for a 23% and 12% increase in essential and nonessential AAs, respectively.

CONCLUSIONS

AA supplementation at 35% REE, but not 20% REE, can effectively prevent hypoaminoacidemia caused by high-dose insulin therapy during cardiac surgery.

Sitagliptin for the prevention of stress hyperglycemia in patients without diabetes undergoing coronary artery bypass graft (CABG) surgery

AIMS

To determine if treatment with sitagliptin, a dipeptidyl peptidase-4 inhibitor, can prevent stress hyperglycemia in patients without diabetes undergoing coronary artery bypass graft (CABG) surgery.

METHODS

We conducted a pilot, double-blinded, placebo-controlled randomized trial in adults (18-80 years) without history of diabetes. Participants received sitagliptin or placebo once daily, starting the day prior to surgery and continued for up to 10 days. Primary outcome was differences in the frequency of stress hyperglycemia (blood glucose (BG) >180 mg/dL) after surgery among groups.

RESULTS

We randomized 32 participants to receive sitagliptin and 28 to placebo (mean age 64±10 years and HbA1c: 5.6%±0.5%). Treatment with sitagliptin resulted in lower BG levels prior to surgery (101±mg/dL vs 107±13 mg/dL, p=0.01); however, there were no differences in the mean BG concentration, proportion of patients who developed stress hyperglycemia (21% vs 22%, p>0.99), length of hospital stay, rate of perioperative complications and need for insulin therapy in the intensive care unit or during the hospital stay.

CONCLUSION

The use of sitagliptin during the perioperative period did not prevent the development of stress hyperglycemia or need for insulin therapy in patients without diabetes undergoing CABG surgery.

Evaluation and Perioperative Management of the Diabetic Patient

Diabetes mellitus is a devastating disease that has reached epidemic proportions. The surgical patient with diabetes is at increased risk for developing complications when compared with patients without diabetes. A comprehensive preoperative work-up must be performed, including ancillary studies, with optimization of the patient's glucose levels during the perioperative period to decrease the chance of developing surgical complications. A multispecialty team approach for the care of patients with diabetes should be used to produce successful surgical outcomes.

Diabetes and elevated preoperative HbA1c level as risk factors for postoperative delirium after cardiac surgery: an observational cohort study

INTRODUCTION

Postoperative delirium (POD) is a common complication of cardiac surgery associated with increased mortality, morbidity, and long-term cognitive dysfunction. Diabetic patients, especially those with poor diabetes control and long-standing hyperglycemia, may be at risk of developing delirium. The aim of this study was to analyze whether the occurrence of POD in cardiac surgery is associated with diabetes or elevated preoperative glycated hemoglobin (HbA1c) level.

MATERIALS AND METHODS

We performed a cohort analysis of prospectively collected data from a register of cardiac surgery department of a university hospital. Delirium assessment was performed twice a day during the first 5 days after the operation based on Diagnostic Statistical Manual of Mental Disorders, fifth edition criteria.

RESULTS

We analyzed a cohort of 3,178 consecutive patients, out of which 1,010 (31.8%) were diabetic and 502 (15.8%) were diagnosed with POD. Patients with delirium were more often diabetic (42.03% vs 29.86%, P<0.001) and on oral diabetic medications (34.66% vs 24.07%, P<0.001), no difference was found in patients with insulin treatment. Preoperative HbA1c was elevated above normal (≥6%) in more delirious than nondelirious patients (44.54% vs 33.04%, P<0.001), but significance was reached only in nondiabetic patients (20.44% vs 14.86%, P=0.018). In univariate analysis, the diagnosis of diabetes was associated with an increased risk of developing POD (OR: 1.703, 95% CI: 1.401-2.071, P<0.001), but only for patients on oral diabetic medications (OR: 1.617, 95% CI: 1.319-1.983, P<0.001) and an association was noted between HbA1c and POD (OR: 1.269, 95% CI: 1.161-1.387, P<0.001). Multivariate analysis controlled for diabetes showed that POD was associated with age, heart failure, preoperative creatinine, extracardiac arteriopathy, and preoperative HbA1c level.

CONCLUSION

More diabetic patients develop POD after cardiac surgery than nondiabetic patients. Elevated preoperative HbA1c level is a risk factor for postcardiac surgery delirium regardless of the diagnosis of diabetes.

Perioperative insulin therapy

Surgical patients commonly develop hyperglycemia secondary to the neuroendocrine stress response. Insulin treatment of hyperglycemia is required to overcome the perioperative catabolic state and acute insulin resistance. Besides its metabolic actions on glucose metabolism, insulin also displays nonmetabolic physiological effects. Preoperative glycemic assessment, maintenance of normoglycemia, and avoidance of glucose variability are paramount to optimize surgical outcomes. This review discusses the basic physiology and effects of insulin as well as practical issues pertaining to its management during the perioperative period.

Perioperative Management of Hyperglycemia and Diabetes in Cardiac Surgery Patients

Perioperative hyperglycemia is common after cardiac surgery, reported in 60% to 90% of patients with diabetes and in approximately 60% of patients without history of diabetes. Many observational and prospective randomized trials in critically-ill cardiac surgery patients support a strong association between hyperglycemia and poor clinical outcome. Despite ongoing debate about the optimal glucose target, there is strong agreement that improved glycemic control reduces perioperative complications.

Importance of Perioperative Blood Glucose Management in Cardiac Surgical Patients

Tight blood glucose control has become a therapeutic goal for anesthetic management of patients undergoing cardiovascular surgery. We discuss the evidence for a link between blood glucose levels and rates of morbidity and mortality in cardiac surgical patients in the intensive care unit. Hyperglycemia per se has been associated with higher rates of deep wound infection, neurologic, renal, and cardiac complications following surgery, as well as longer intensive care unit stay. We review the specifics of glucose management in patients undergoing cardiac surgery and hypothermic cardiopulmonary bypass, including the role that insulin may play in regulating blood glucose levels intraoperatively and the relationship between insulin and outcome.

Perioperative glycemic control with a computerized algorithm versus conventional glycemic control in cardiac surgical patients undergoing cardiopulmonary bypass with blood cardioplegia

OBJECTIVE

In critical illness, hypoglycemia and hyperglycemia seem to influence outcome. While hypoglycemia can lead to organ dysfunction, hyperglycemia can lead to surgical site infections (SSI). In cardiac surgery, the use of blood cardioplegia is associated with high blood glucose levels. A computer-based algorithm (CBA) for guiding insulin towards normoglycemia might be beneficial. The authors' primary study end-point was the duration in a predefined blood glucose target range of 80 mg/dL to 150 mg/dL. Patients with conventional therapy served as controls.

DESIGN

Prospective, randomized trial.

SETTING

University hospital.

PARTICIPANTS

Seventy-five patients.

INTERVENTIONS

The start of therapy was the beginning of cardiopulmonary bypass. Group A: Therapy with CBA and measurement of blood glucose every 30 minutes. Group B: Measurement of blood glucose every 15 minutes using the identical CBA. Group C: Conventional therapy using a fixed insulin dosing scheme. End of therapy was defined as discharge from ICU.

MEASUREMENT AND MAIN RESULTS

Glucose administration during cardioplegia did not differ between groups (A: 33 ± 12 g; B: 32 ± 12 g; C: 38 ± 20 g). Glucose levels in groups A and B stayed significantly longer in the target interval compared with group C (A: 75 ± 20%; B: 72 ± 19%; C: 50 ± 34%, p < 0.01 n = 25, respectively). There were no significant differences regarding ICU stay and SSI rates.

CONCLUSIONS

Early computer-based insulin therapy allows practitioners to better achieve normoglycemia in patients undergoing major cardiac surgery with the use of blood cardioplegia.

Intraoperative tight glucose control using hyperinsulinemic normoglycemia increases delirium after cardiac surgery

BACKGROUND

Postoperative delirium is common in patients recovering from cardiac surgery. Tight glucose control has been shown to reduce mortality and morbidity. Therefore, the authors sought to determine the effect of tight intraoperative glucose control using a hyperinsulinemic-normoglycemic clamp approach on postoperative delirium in patients undergoing cardiac surgery.

METHODS

The authors enrolled 198 adult patients having cardiac surgery in this randomized, double-blind, single-center trial. Patients were randomly assigned to either tight intraoperative glucose control with a hyperinsulinemic-normoglycemic clamp (target blood glucose, 80 to 110 mg/dl) or standard therapy (conventional insulin administration with blood glucose target, <150 mg/dl). Delirium was assessed using a comprehensive delirium battery. The authors considered patients to have experienced postoperative delirium when Confusion Assessment Method testing was positive at any assessment. A positive Confusion Assessment Method was defined by the presence of features 1 (acute onset and fluctuating course) and 2 (inattention) and either 3 (disorganized thinking) or 4 (altered consciousness).

RESULTS

Patients randomized to tight glucose control were more likely to be diagnosed as being delirious than those assigned to routine glucose control (26 of 93 vs. 15 of 105; relative risk, 1.89; 95% CI, 1.06 to 3.37; P = 0.03), after adjusting for preoperative usage of calcium channel blocker and American Society of Anesthesiologist physical status. Delirium severity, among patients with delirium, was comparable with each glucose management strategy.

CONCLUSION

Intraoperative hyperinsulinemic-normoglycemia augments the risk of delirium after cardiac surgery, but not its severity.

Pharmacological and nonpharmacological treatment after cardiac surgery

Open-heart surgery has become a common procedure. Postcardiac surgery management is a critical issue and represents a crucial period in terms of physical recovery. Cardiac rehabilitation is increasingly considered as an integral component of the continuum of care for patients with cardiovascular disease. Its usefulness is now widely accepted, and therefore, it is recommended in most contemporary cardiovascular clinical practice guidelines. Similarly, early pharmacological management can modulate the pathophysiological alterations after cardiac surgery, leading to an improvement in the early and long-term outcome. In this review, we will present recent advances in postcardiac surgery management, focusing on the pathophysiology of the perioperative period and on recent evidences in pharmacological and rehabilitative strategies.

Perioperative catabolism

PURPOSE

This article reviews the pathophysiology, clinical relevance, and therapy of the catabolic response to surgical stress.

PRINCIPLE FINDINGS

The key clinical features of perioperative catabolism are hyperglycemia and loss of body protein, both metabolic consequences of impaired insulin function. Muscle weakness and (even moderate) increases in perioperative blood glucose are associated with morbidity after major surgery. Although the optimal glucose concentration for improving clinical outcomes is unknown, most medical associations recommend treatment of random blood glucose > 10 mmol·L(-1). Neuraxial anesthesia blunts the neuroendocrine stress response and enhances the anabolic effects of nutrition. There is evidence to suggest that the avoidance of preoperative fasting prevents insulin resistance and accelerates recovery after major abdominal surgery.

CONCLUSIONS

Current anticatabolic therapeutic strategies include glycemic control and perioperative nutrition in combination with optimal pain control and the avoidance of preoperative starvation. All these elements are part of Enhanced Recovery After Surgery (ERAS) programs.

Intraoperative maintenance of normoglycemia with insulin and glucose preserves verbal learning after cardiac surgery

Objective

The hyperglycemic response to surgery may be a risk factor for cognitive dysfunction. We hypothesize that strict maintenance of normoglycemia during cardiac surgery preserves postoperative cognitive function.

Methods

As part of a larger randomized, single-blind, interventional efficacy study on the effects of hyperinsulinemic glucose control in cardiac surgery (NCT00524472), consenting patients were randomly assigned to receive combined administration of insulin and glucose, titrated to preserve normoglycemia (3.5–6.1 mmol L⁻¹; experimental group), or standard metabolic care (blood glucose 3.5–10 mmol L⁻¹; control group), during open heart surgery. The patients’ cognitive function was assessed during three home visits, approximately two weeks before the operation, and two months and seven months after surgery. The following tests were performed: Rey Auditory Verbal Learning Task (RAVLT for verbal learning and memory), Digit Span Task (working memory), Trail Making A & B (visuomotor tracking and attention), and the Word Pair Task (implicit memory). Questionnaires measuring specific traits known to affect cognitive performance, such as self-esteem, depression, chronic stress and social support, were also administered. The primary outcome was to assess the effect of hyperinsulinemic-normoglycemic clamp therapy versus standard therapy on specific cognitive parameters in patients receiving normoglycemic clamp, or standard metabolic care.

Results

Twenty-six patients completed the study with 14 patients in the normoglycemia and 12 patients in the control group. Multiple analysis of covariance (MANCOVA) for the RAVLT showed a significant effect for the interaction of group by visit (F = 4.07, p = 0.035), and group by visit by recall (F = 2.21, p = 0.04). The differences occurred at the second and third visit. MANCOVA for the digit span task, trail making and word pair association test showed no significant effect.

Conclusions

Preserving intraoperative normoglycemia by intravenous insulin and glucose may prevent the impairment of memory function, both short and long-term, after cardiac surgery.

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.

Diabetes, perioperative ischaemia and volatile anaesthetics: consequences of derangements in myocardial substrate metabolism

Volatile anaesthetics exert protective effects on the heart against perioperative ischaemic injury. However, there is growing evidence that these cardioprotective properties are reduced in case of type 2 diabetes mellitus. A strong predictor of postoperative cardiac function is myocardial substrate metabolism. In the type 2 diabetic heart, substrate metabolism is shifted from glucose utilisation to fatty acid oxidation, resulting in metabolic inflexibility and cardiac dysfunction. The ischaemic heart also loses its metabolic flexibility and can switch to glucose or fatty acid oxidation as its preferential state, which may deteriorate cardiac function even further in case of type 2 diabetes mellitus.Recent experimental studies suggest that the cardioprotective properties of volatile anaesthetics partly rely on changing myocardial substrate metabolism. Interventions that target at restoration of metabolic derangements, like lifestyle and pharmacological interventions, may therefore be an interesting candidate to reduce perioperative complications. This review will focus on the current knowledge regarding myocardial substrate metabolism during volatile anaesthesia in the obese and type 2 diabetic heart during perioperative ischaemia.

The correlation between peri-operative hyperglycemia and mortality in cardiac surgery patients: a systematic review

BACKGROUND

Hyperglycemia occurs frequently in patients undergoing cardiac surgery. It has been identified as a risk factor for increased peri-operative morbidity and mortality.

AIM

To review the evidence of the correlation of peri-operative hyperglycemia with mortality in cardiac surgery patients and to discuss the main results in order to provide evidence-based knowledge for the appropriate glycemic control.

METHODS

We searched the electronic databases MEDLINE, CINAHL and EMBASE in June 2010. The material of our study was articles published between 1 January 1990 and 31 May 2010, which investigated the correlation between peri-operative hyperglycemia and in-hospital and/or 30-day cardiac surgery mortality.

RESULTS

Out of the 16 reviewed articles in our study, 12 (75%) significantly associated hyperglycemia and inadequate blood glucose control with increased mortality. In addition, four of the reviewed articles were controlled randomized trials and among them only one demonstrated strong correlation between poor glycemic control and mortality. No study was multi-centre and the reviewed articles were characterized by different definitions of peri-operative hyperglycemia, different intensity and duration of the applied therapy and heterogeneity of the population.

CONCLUSION

It is clear that peri-operative hyperglycemia is harmful for cardiac surgery patients. The significant shortage of randomized controlled trials, the absence of multicentre studies, the different definitions of peri-operative hyperglycemia, the different intensity and duration of the applied insulin therapy protocol and the heterogeneity of the studied population (diabetics and non-diabetics) are significant limitations, which could explain the inconsistent findings of the literature. These limitations indicate the need for further research.

Do nondiabetic patients undergoing coronary artery bypass grafting surgery require intraoperative management of hyperglycemia?

OBJECTIVE

To study the effect of blood glucose (BG) control with insulin in preventing hyperglycemia during and after coronary artery bypass grafting (CABG) surgery in nondiabetic patients.

METHODS

In a randomized clinical trial, 120 nondiabetic patients who underwent elective CABG surgery were enrolled for study of whether the control of hyperglycemia was a need in such a surgery in a teaching heart hospital. The patients were randomly divided into study (n=60) and control (n=60) groups. In the study group, insulin was infused to maintain BG level between 110 mg/dL and 126 mg/dL (a modified insulin therapy protocol, and in the control group, the patients were excepted). Insulin therapy was limited to intraoperative period. BG levels during surgery and up to 48 hours after surgery and early postoperative complications were compared between the study and control groups.

RESULTS

One hundred seventeen patients completed the study (59 patients in study group and 58 in control group). Peak intraoperative BG level in the study group was 126.4±17.9 mg/dL and in the control group was 137.3±17.6 mg/dL (p=0.024). The frequencies of severe hyperglycemia (BG≥180 mg/dL) were 6 of 59 (10.1%) in the study group and 19 of 58 (32.7%) in the control group during operation (p=0.002). Peak postoperative BG level in the study group was 194.8±41.2 mg/dL and was 199.8±43.2 mg/dL in the control group (p=0.571). There was no hypoglycemic event in either group. The frequencies of early postoperative complications were 10 of 59 (16.9%) in the study group and 19 of 58 (32.7%) in the control group (p=0.047).

CONCLUSIONS

Hyperglycemia (BG≥126 mg/dL) is common in nondiabetic patients undergoing CABG surgery. A modified insulin therapy to maintain BG level between 110 mg/dL and 126 mg/dL may be acceptable for avoiding hypoglycemia and keeping intraoperative BG levels in acceptable range in nondiabetics.

Perioperative glucose control: living in uncertain times--Continuing Professional Development

PURPOSE

Hyperglycemia occurs frequently in surgical patients. The objective of this Continuing Professional Development (CPD) module is to review glucose physiology and pathophysiology and provide an update on the practical management of perioperative glucose based on recently published randomized controlled trials (RCTs).

PRINCIPAL FINDINGS

In the mid 2000s, several professional medical organizations recommended the implementation of strict glucose control (glucose concentrations 4.4 to 6.1 mmol·L(-1)). However, the publication of new randomized controlled trials has dampened the initial enthusiasm. While the optimal glucose target range remains a matter of debate, hyperglycemia has been associated with increased morbidity and mortality in a variety of clinical settings. However, strict glucose control is associated with a sixfold increase in episodes of severe hypoglycemia (glucose levels < 2.2 mmol·L(-1)), which has also been linked with increased mortality. For critically ill patients, the American Diabetes Association and the American Association of Clinical Endocrinologists recommend aiming for a blood glucose level from 7.8 to 10.0 mmol·L(-1). While no specific target range can be recommended as yet during major surgery, glucose levels should be kept < 10.0 mmol·L(-1). In critically ill patients, glucose measured from capillary blood may give a falsely elevated value, so arterial blood sampling is preferred when measuring glucose. Frequent arterial blood glucose determination using an arterial blood gas analyzer or an International Organization for Standardization (ISO) 15197-compliant glucometer is crucial to avoid and detect deleterious hypoglycemic episodes.

CONCLUSIONS

Although there is agreement that both hyperglycemia and hypoglycemia are deleterious, there is no consensus on the target glucose values to enhance clinical outcomes.

The effect of tight glycaemic control, during and after cardiac surgery, on patient mortality and morbidity: A systematic review and meta-analysis

BACKGROUND

Hyperglycaemia is a common occurrence during cardiac surgery, however, there remains some uncertainty surrounding the role of tight glycaemic control (blood glucose <180 mg/dL) during and/or after surgery. The aim of this study was to systematically review the literature to determine the effects of tight versus normal glycaemic control, during and after cardiac surgery, on measures of morbidity and mortality.

METHOD

The literature was systematically reviewed, based on pre-determined search criteria, for clinical trials evaluating the effect of tight versus normal glycaemic control during and/or after cardiac surgery. Each paper was reviewed by two, independent reviewers and data extracted for statistical analysis. Data from identified studies was combined using meta-analysis (RevMan5®). The results are presented either as odds ratios (OR) or mean differences (MD) with 95% confidence intervals (CIs).

RESULTS

A total of seven randomised controlled trials (RCTs) were identified in the literature, although not all trials could be used in each analysis. Tight glycaemic control reduced the incidence of early mortality (death in ICU) (OR 0.52 [95% CI 0.30, 0.91]); of post-surgical atrial fibrillation (odds ratio (OR 0.76 [95%CI 0.58, 0.99]); the use of epicardial pacing (OR 0.28 [95%CI 0.15, 0.54]); the duration of mechanical ventilation (mean difference (MD) -3.69 [95% CI -3.85, -3.54]) and length of stay in the intensive care unit (ICU) (MD -0.57 [95%CI -0.60, -0.55]) days. Measures of the time spent on mechanical ventilation (I2 94%) and time spent in ICU (I2 99%) both had high degrees of heterogeneity in the data.

CONCLUSION

The results from this study suggest that there may be some benefit to tight glycaemic control during and after cardiac surgery. However, due to the limited number of studies available and the significant variability in glucose levels; period of control; and the reporting of outcome measures, further research needs to be done to provide a definitive answer on the benefits of tight glycaemic control for cardiac surgery patients.

Use of a continuous glucose sensor in an extracorporeal life support circuit

BACKGROUND

Standard care for infants on extracorporeal life support (ECLS) relies on intermittent measurement of blood glucose (BG); however, this can lead to significant changes in BG that go unrecognized for several hours. The present study was designed to assess performance and clinical applicability of a subcutaneous glucose sensor technology modified for use as a blood-contacting sensor within the ECLS circuit.

METHODS

Twelve children, aged 3 years or less, requiring ECLS support were studied. Three continuous glucose sensors (Medtronic MiniMed) were inserted into hubs placed in line with the ECLS circuit. Blood glucose was assessed with a laboratory analyzer (BG(LAB); Bayer Rapidlab 860) approximately every 5 h (mean 4.9 ± 3.3 h) with more frequent samples obtained with a bedside monitor (HemoCue) as needed. Sensor current (I(SIG)) was transmitted to a laptop computer and retrospectively calibrated using BGLAB. Sensor performance was assessed by mean absolute relative difference (MARD), linear regression slope and intercept, and correlation, all with BGLAB as reference.

RESULTS

The BGLAB averaged 107.6 ± 36.4 mg/dl (mean ± standard deviation) ranging from 58 to 366 mg/dl. The MARD was 11.4%, with linear regression slope (0.86 ± 0.030) and intercept (9.0 ± 3.2 mg/dl) different from 1 and 0, respectively (p < .05), and correlation (r² = 0.76; p < .001). The system was not associated with any adverse events, and placement and removal into the hubs was easily accomplished. Instances in which more frequent BG values were obtained using a bedside HemoCue (BGHEMO) monitor showed the sensor to respond rapidly to changes.

CONCLUSIONS

We conclude that continuous sensors can be adapted for use in an ECLS circuit with accuracy similar to or better than that achieved with the subcutaneous site. Continuous glucose monitoring in this population can rapidly detect changes in BG that would not otherwise be observed. Further studies will be needed to assess the benefit of continuous glucose monitoring in this population.

Glucose and insulin administration while maintaining normoglycemia during cardiac surgery using a computer-assisted algorithm

BACKGROUND

applying the principles of the hyperinsulinemic-normoglycemic clamp technique we have introduced glucose and insulin administration while maintaining normoglycemia (GIN therapy) to surgical patients. The objective of this study was to evaluate a novel computer software (GIN Computer Software [GINCS]) program using an algorithm based on the original clamp equation and modified for its use during cardiac surgery.

METHODS

thirty-six patients without diabetes undergoing elective cardiac surgery were randomly assigned to manually controlled or computer-guided GIN therapy. In both groups insulin was administered at 5 mU/kg/min during surgery. Simultaneously, 20% dextrose was infused at a rate adjusted to maintain blood glucose (BG) between 4.0 and 6.0 mmol/L. The adjustments were made either following an algorithm based on our previous GIN experience or suggestions made by the software program. The primary outcome was the achievement of target glycemia.

RESULTS

normoglycemia was achieved in both groups as reflected by mean BG concentrations of 5.0 ± 0.5 mmol/L and 5.1 ± 0.2 mmol/L. Mean sampling intervals were longer in the GINCS group than in the manual group (21.5  ± 1.9 vs. 14.2 ± 2.2 min, P < 0.001). The GINCS therapy was associated with a greater percentage of BG measurements within target (manual group, before cardiopulmonary bypass [CPB] 79.7%, during CPB 68.1%, and after CPB 69.1%; GINCS group, before CPB 94.1%, during CPB 92.4%, and after CPB 97.7%; P < 0.001). No hypoglycemia was observed.

CONCLUSIONS

the use of a computer-guided GIN protocol in patients without diabetes undergoing open heart surgery provided excellent and safe glycemic control.

Perioperative glucose and insulin administration while maintaining normoglycemia (GIN therapy) in patients undergoing major liver resection

BACKGROUND

Although hyperglycemia is a well-recognized risk factor in the context of cardiac surgery, the relevance of perioperative glycemic control for patients undergoing major noncardiac operations has received little attention. We designed this study to assess the hyperglycemic response to liver resection, and to test the hypothesis that perioperative glucose and insulin administration while maintaining normoglycemia (GIN therapy) provides glycemic control superior to that achieved by the conventional use of insulin.

METHODS

Patients were randomly assigned to GIN therapy or standard therapy (control group). In the GIN therapy group, insulin was administered at 2 mU . kg(-1) . min(-1) during surgery. At the end of surgery, the insulin infusion was decreased to 1 mU . kg(-1) . min(-1) and continued for 24 hours. Dextrose 20% was infused at a rate adjusted to maintain blood glucose within the target range of 3.5 to 6.1 mmol . L(-1) (63-110 mg . dL(-1)). Patients in the standard therapy group received a conventional insulin sliding scale during and after surgery. The mean and SD of blood glucose as well as the percentage of blood glucose values within the target range were calculated. To evaluate intrasubject variability, the coefficient of variability (CV) of blood glucose was calculated for each patient. Episodes of severe hypoglycemia, i.e., blood glucose <2.2 mmol . L(-1) (40 mg . dL(-1)), were recorded. The primary outcome was the proportion of normoglycemic measurements.

RESULTS

We studied 52 patients. The mean blood glucose value in patients receiving GIN therapy always remained within the target range. The blood glucose levels were lower in the GIN therapy group than in the standard therapy group (during surgery, P < 0.01; after surgery, P < 0.001). In nondiabetic patients receiving GIN therapy (n = 19), target glycemia was achieved in 90.1% of the blood glucose measurements during surgery and in 77.8% of the measurements after surgery. In diabetic patients receiving GIN therapy (n = 7), target glycemia was achieved in 81.2% of the blood glucose measurements during surgery and in 70.5% of the measurements after surgery. In nondiabetic patients receiving standard therapy (n = 19), target glycemia was achieved in 37.4% of the blood glucose measurements during surgery and in 18.3% of the measurements after surgery. In diabetic patients receiving standard therapy (n = 7), target glycemia was achieved in 4.3% of the blood glucose measurements during surgery and in 2.9% of the measurements after surgery. The SD and CV of blood glucose were smaller in the GIN therapy group than in the standard therapy group, especially in nondiabetic patients after surgery (SD, P < 0.001; CV, P = 0.027). No patients receiving GIN therapy experienced severe hypoglycemia during surgery. One patient receiving GIN therapy experienced hypoglycemia in the intensive care unit after surgery without neurological sequelae.

CONCLUSIONS

GIN therapy effectively provides normoglycemia in patients undergoing liver resection (clinicaltrials.gov, NCT00774098).

Monitoring endocrine function

This article reviews current knowledge concerning the monitoring of endocrine function in patients in the clinical setting. Monitoring techniques are discussed and literature is reviewed regarding diabetes mellitus, thyroid, and parathyroid disorders, pheochromocytoma, adrenal insufficiency, and carcinoid tumors.

Intraoperative glycemic control procedures and the use of an artificial pancreas

Strict intraoperative glycemic control can significantly decrease the incidence of postoperative infection; however, anesthesiologists must carefully control blood glucose levels as well as properly manage the respiratory and cardiovascular systems. However, standard blood glucose measurement systems and insulin dosing algorithms, which are necessary for achieving strict glycemic control, have not yet been developed. An artificial pancreas (STG-22^TM; Nikkiso Co., Tokyo, Japan) is considered a highly accurate blood glucose monitoring system capable of closed-loop control of blood glucose. The device has, however, many problems to be addressed since it is a large and expensive system with little versatility, and it requires a large amount of blood to be collected. Therefore, the development of less invasive and inexpensive systems with future technological progress is greatly anticipated.

[Repercussions and management of perioperative hyperglycemia in cardiac surgery]

Surgery produces a neuroendocrine stress response that affects resistance to insulin, reduces insulin secretion, and increases the release of glucose from the liver. This situation can trigger hyperglycemia in both diabetics and nondiabetics. Hyperglycemia has been linked to an increase in the morbidity and mortality among patients who undergo cardiac surgery, and the benefits of correcting hyperglycemia in this setting by means of intensive insulin therapy are well documented. This review discusses various aspects of hyperglycemia, particularly the evidence supporting stricter control of this condition in patients undergoing cardiac surgery. Furthermore, based on the available data and recommendations, and our clinical experience, we suggest therapeutic strategies to improve the control of hyperglycemia in these patients.

Glucose monitoring in acute care: technologies on the horizon

Current glucose monitoring technology appears inadequate for the management of diabetic surgical and in critically ill patients requiring intensive insulin therapy. Subcutaneous sensors measure interstitial fluid glucose, and this technology has not yet been shown to provide the timely and accurate measurements necessary for intravenous insulin administration in surgical and critical care patients on intensive insulin therapy. Technologies under development that may be more suitable for surgical and intensive care unit patients are the automated intermittent type glucose monitors and central catheter glucose monitors. Improved accuracy, patient safety, incorporation of control algorithms, and alleviation of added nursing labor are important factors for consideration with future acute care glucose monitors. Hospital costs for these monitors are difficult to estimate but may be relatively low if their use can be related to better patient outcome, reduced labor costs, and increased job satisfaction for the nursing staff.

Perioperative hyperinsulinaemic normoglycaemic clamp causes hypolipidaemia after coronary artery surgery

BACKGROUND

Glucose-insulin-potassium (GIK) administration is advocated on the premise of preventing hyperglycaemia and hyperlipidaemia during reperfusion after cardiac interventions. Current research has focused on hyperglycaemia, largely ignoring lipids, or other substrates. The present study examines lipids and other substrates during and after on-pump coronary artery bypass grafting and how they are affected by a hyperinsulinaemic normoglycaemic clamp.

METHODS

Forty-four patients were randomized to a control group (n=21) or to a GIK group (n=23) receiving a hyperinsulinaemic normoglycaemic clamp during 26 h. Plasma levels of free fatty acid (FFA), total and lipoprotein (VLDL, HDL, and LDL)-triglycerides (TG), ketone bodies, and lactate were determined.

RESULTS

In the control group, mean FFA peaked at 0.76 (sem 0.05) mmol litre(-1) at early reperfusion and decreased to 0.3-0.5 mmol litre(-1) during the remaining part of the study. GIK decreased FFA levels to 0.38 (0.05) mmol litre(-1) at early reperfusion, and to low concentrations of 0.10 (0.01) mmol litre(-1) during the hyperinsulinaemic clamp. GIK reduced the area under the curve (AUC) for FFA by 75% and for TG by 53%. The reduction in total TG was reflected by a reduction in the VLDL (-54% AUC) and HDL (-42% AUC) fraction, but not in the LDL fraction. GIK prevented the increase in ketone bodies after reperfusion (-44 to -47% AUC), but was without effect on lactate levels.

CONCLUSIONS

Mild hyperlipidaemia was only observed during early reperfusion (before heparin reversal) and the hyperinsulinaemic normoglycaemic clamp actually resulted in hypolipidaemia during the largest part of reperfusion after cardiac surgery.

Strict glycemic control reduces EuroSCORE expected mortality in diabetic patients undergoing myocardial revascularization

OBJECTIVE

We sought to evaluate the effect of a strict glycemic control protocol on a series of diabetic patients undergoing surgical myocardial revascularization.

METHODS

Between January 2003 and June 2004, 300 diabetic patients undergoing myocardial revascularization received a local protocol of insulin administration (protocol, group P). Patients were divided into 2 risk classes, according to their additive EuroSCORE value: low-moderate risk (0-4) and moderate-high risk (>4). The logistic EuroSCORE algorithm was used to calculate the expected probability of death. A control group was selected, including a series of 300 consecutive diabetic patients (no protocol group, group NP) who underwent coronary artery bypass grafting between March 2001 and September 2002, just before the introduction of the protocol. A propensity analysis was performed to control for selection bias.

RESULTS

Both groups showed similar EuroSCORE risk profiles: mean additive and logistic EuroSCORE values were 4.16 and 4.29 in group P versus 3.93 and 3.91 in group NP. Observed and expected mortalities of group P were 0.6% versus 1.8% (low-moderate risk), 2.5% versus 8.0% (moderate-high risk, P = .03), and 1.3% versus 4.3% (entire group, P = .01). Observed and expected mortalities of group NP were 1.6% versus 1.9% (low-moderate risk), 8.3% versus 7.5% (moderate-high risk), and 4.0% versus 3.9% (entire group). Logistic regression confirmed observed mortality in group P to be significantly lower than the expected logistic EuroSCORE mortality. After risk adjustment, the protocol allowed us to reduce the mortality odds by 72% (odds ratio, 0.282; 95% confidence interval, 0.092-0.859; P < .03). Subgroup analysis for moderate- to high-risk patients showed the protocol to improve mortality (odds ratio, 0.24; P < .05), whereas no significant improvement was found in low- to moderate-risk patients. Addition of the propensity score to the multivariable analysis did not significantly displace P values and odds ratios. Sensitivity analysis of patients who underwent coronary artery bypass grafting without additional procedures showed the protocol to maintain its protective effect (odds ratio, 0.15; P < .05).

CONCLUSION

Optimal glucose control highly reduces EuroSCORE expected mortality in diabetic patients undergoing myocardial revascularization, especially in moderate- to high-risk patients.

Diabetes Care for Patients with Peripheral Arterial Disease

The number of diabetics will increase almost 70% in developed countries during the next 20 years: peripheral arterial disease is a common and costly complication. The incidence of cardiovascular disease (mortality and morbidity) due to atherosclerosis, is higher among patients with diabetes than in those without diabetes. Intensive management of diabetes, including glycaemic control, treatment of hypertension and dyslipidemia, as well as nonpharmacological interventions, decreases both micro- and macrovascular complications. Aspirin and clopidogrel have less antiplatelet effect in patients with diabetes. Metformin therapy is considered a risk factor for lactic acidosis if not withdrawn 2 days before angiography, but this risk is extremely low in patients with normal renal function. Peri-operative hyperglycaemia and large fluctuations in plasma glucose increase postoperative mortality and morbidity and careful measures are required to minimise these effects.