Glucose-insulin-potassium solutions improve outcomes in diabetics who have coronary artery operations

Cardioprotective Effects of Glucose-Insulin-Potassium Infusion in Patients Undergoing Cardiac Surgery: A Systematic Review and Meta-Analysis

The infusion of glucose-insulin-potassium (GIK) has yielded conflicting results in terms of cardioprotective effects. We conducted a meta-analysis to examine the impact of perioperative GIK infusion in early outcome after cardiac surgery. Randomized controlled trials (RCTs) were eligible if they examined the efficacy of GIK infusion in adults undergoing cardiac surgery. The main study endpoint was postoperative myocardial infarction (MI) and secondary outcomes were hemodynamics, any complications and hospital resources utilization. Subgroup analyses explored the impact of the type of surgery, GIK composition and timing of administration. Odds ratio (OR) or mean difference (MD) with 95% confidence interval (CI) were calculated with a random-effects model. Fifty-three studies (n=6129) met the inclusion criteria. Perioperative GIK infusion was effective in reducing MI (k=32 OR 0.66[0.48, 0.89] P=0.0069), acute kidney injury (k=7 OR 0.57[0.4, 0.82] P=0.0023) and hospital length of stay (k=19 MD -0.89[-1.63, -0.16] days P=0.0175). Postoperatively, the GIK-treated group presented higher cardiac index (k=14 MD 0.43[0.29, 0.57] L/min P<0.0001) and lesser hyperglycemia (k=20 MD -30[-47, -13] mg/dL P=0.0005) than in the usual care group. The GIK-associated protection for MI was effective when insulin infusion rate exceeded 2 mUI/kg/min and after coronary artery bypass surgery. Certainty of evidence was low given imprecision of the effect estimate, heterogeneity in outcome definition and risk of bias. Perioperative GIK infusion is associated with improved early outcome and reduced hospital resource utilization after cardiac surgery. Supporting evidence is heterogenous and further research is needed to standardize the optimal timing and composition of GIK solutions.

Myocardium Metabolism in Physiological and Pathophysiological States: Implications of Epicardial Adipose Tissue and Potential Therapeutic Targets

The main energy substrate of adult cardiomyocytes for their contractility are the fatty acids. Its metabolism generates high ATP levels at the expense of high oxygen consumption in the mitochondria. Under low oxygen supply, they can get energy from other substrates, mainly glucose, lactate, ketone bodies, etc., but the mitochondrial dysfunction, in pathological conditions, reduces the oxidative metabolism. In consequence, fatty acids are stored into epicardial fat and its accumulation provokes inflammation, insulin resistance, and oxidative stress, which enhance the myocardium dysfunction. Some therapies focused on improvement the fatty acids entry into mitochondria have failed to demonstrate benefits on cardiovascular disorders. Oppositely, those therapies with effects on epicardial fat volume and inflammation might improve the oxidative metabolism of myocardium and might reduce the cardiovascular disease progression. This review aims at explain (a) the energy substrate adaptation of myocardium in physiological conditions, (b) the reduction of oxidative metabolism in pathological conditions and consequences on epicardial fat accumulation and insulin resistance, and (c) the reduction of cardiovascular outcomes after regulation by some therapies.

Insulin-Based Infusion System: Preliminary Study

BACKGROUND

Optimal glucose control has been shown to be useful in critical care as well as in other settings. Glucose concentrations in patients admitted to critical care are characterized by marked variability and hypoglycemia due to inadequate sensing and treatment technologies.

METHODS

The insulin balanced infusion system (IBIS) is a closed-loop system that uses a system controller, two syringe pumps, and capillary glucose sensor intravenously infusing regular insulin and/or dextrose. The IBIS performance was evaluated in terms of glucose stability in response to various conditions in subjects with type 1 and insulin requiring type 2 diabetes mellitus (n = 15) with frequent intermittent capillary measurements, entered into the system and an adaptive algorithm adjusting the treatment modalities without other nursing intervention.

RESULTS

Target glucose concentrations (80-125 mg/dl) were achieved from hyperglycemic levels in 2.49 hours in the first study with mean and standard deviation of 105.2 mg/dl and 11.5 mg/dl, respectively.

CONCLUSION

Preliminary studies using a prototype closed-loop glucose control system for critical care produced noticeable results. Improvements were initiated within the system and further studies performed.

Comparison of intensive insulin therapy and conventional glucose management in patients undergoing coronary artery bypass grafting

Background and Aims

Hyperglycemia during cardiac surgery is a risk factor for postoperative outcomes. Because incidence of diabetes mellitus is increasing in Indian population, we tried to evaluate the western protocol for strict control of blood sugar perioperatively. The main aim of the study was to evaluate glycemic control during coronary artery bypass grafting and to determine whether intensive insulin therapy (IIT) is better than the conventional one.

Material and Methods

A prospective randomized comparative study was conducted to evaluate IIT and conventional management of glucose in 40 patients undergoing on-pump coronary artery bypass grafting. Outcomes measured were incidence of hyperglycemia or hypoglycemia, incidence of hypokalemia, prolonged intubation, wound infections, strokes, acute renal failure, new onset arrhythmias, length of stay in ICU and hospital, cardiac arrest and mortality. The statistical analysis was done by using Chi-square test, and paired and unpaired t test.

Results

The diabetic patients had significantly higher mean blood sugar and insulin requirement. The incidence of hyperglycemia was significantly higher in conventional management of blood sugar (P = 0.001), whereas hypoglycemia (P = 0.047) and hypokalemia (P = 0.020) were significantly higher in IIT. There were no significant difference in the incidence of prolonged intubation, wound infection, length of ICU and hospital stay, strokes, acute renal failure, new onset arrhythmias, cardiac arrest, and mortality.

Conclusion

The IIT did not improve the morbidity and mortality in our patients undergoing coronary artery bypass grafting.

Effect of glycaemic control on complications following cardiac surgery: literature review

Introduction

No uniform consensus in the UK or Europe exists, for glycaemic management of patients with Diabetes or pre-diabetes undergoing cardiac surgery.

Objective

[i] Determine the relationship between glycaemic control and cardiac surgical outcomes; [ii] Compare current vs gold standard management of patients with Diabetes or pre-diabetes undergoing cardiac surgery.

Methods

Searches of MEDLINE, NHS Evidence and Web of Science databases were completed. Articles were limited to those in English, German and French. No date limit was enforced.13,232 articles were identified on initial literature review, and 50 relevant papers included in this review.

Results

No national standards for glycaemic control prior to cardiac surgery were identified. Upto 30% of cardiac surgical patients have undiagnosed Diabetes. Cardiac surgical patients without Diabetes with pre-operative hyperglycaemia have a 1 year mortality double that of patients with normoglyacemia, and equivalent to patients already diagnosed with Diabetes. Pre- and peri-operative hyperglycaemia is associated with worse outcomes. Evidence regarding tight glycaemic control vs moderate glycaemic control is conflicting. Tight control may be more effective in patients without Diabetes with pre−/peri-operative hyperglycaemia, and moderate control appears more effective in patients with pre-existing Diabetes. Patients with well controlled Diabetes may achieve comparable outcomes to patients without Diabetes with similar glycaemic control.

Conclusions

Pre / peri-operative hyperglycaemia is associated with worse outcomes in both patients with, and without Diabetes undergoing CABG. This review supports the pre-operative screening, and optimisation of glycaemic control in patients undergoing cardiac surgery. Optimal glycaemic management remains unclear and clear guidelines are needed.

Impact of elevated glycosylated hemoglobin on hospital outcome and 1 year survival of primary isolated coronary artery bypass grafting patients

Objective

It is unknown whether adequacy of diabetic control, measured by hemoglobin A1c, is a predictor of adverse outcomes after coronary artery bypass grafting.

Methods

From December 2013 to November 2015, 80 consecutive patients underwent primary isolated CABG surgery at national heart institute, their data were prospectively collected and they were classified according to their HbA1c level into two groups, Group (A): Forty patients with fair glycemic control (HbA1c below or equal to 7%), Group (B): Forty patients with poor glycemic control (HbA1c above 7%). Hospital morbidity, mortality and one year survival were examined in both groups. Telephone conversation was used to call patients or their relatives to determine the one year survival and it was 100% complete. This study had gained the ethical approval from national heart institute ethical committee.

Results

In-hospital mortality for group A was 2.5% (one patient) and 7.5% (3 patients) for group B with no statistical significance. One year mortality was (5.13%) (2 patients for group A) and (8.11%) (3 patients) for group B with no statistical significance. As regard the morbidity there was no statistical significance between the two groups in the incidence of neurological complications whether stroke or coma, atrial fibrillation, postoperative myocardial infarction, low cardiac output syndrome, heart failure, renal failure, need for dialysis, deep sternal wound infection, and readmission. However, group B had lengthy hospital stay, lengthy ventilation hours, more respiratory complications, and more superficial wound infection with a statistical significance when compared to group A, P values were 0.003, 0.003, 0.038, 0.044 respectively.

Conclusions

This study showed that HbA1c is a good predictor of in-hospital morbidity. It worth devoting time and effort to decrease HbA1c level below 7% to decrease possible postoperative complications.

Myocardial protection with Glucose-Insulin-Potassium infusion during adult cardiac surgery

Background & Objective:

Recent meta-analysis reports have called for more randomized trials to evaluate the effectiveness of GIK solution in patients of cardiac surgery. So this study was conducted to evaluate the effectiveness of Glucose-insulin-potassium (GIK) solutions in non-diabetic patients undergoing coronary artery bypass grafting.

Methods:

A total number of one hundred and sixty (160) patients were randomized into two equal groups; GIK Group and non-GIK group. In GIK group, 5% dextrose containing 70 IU/L regular insulin and 70 meq/L of potassium was administered. The infusion was started at a rate of 30 ml/hour after induction of anesthesia and before the start of cardiopulmonary bypass. The infusion was started again after removal of aortic cross clamp and was continued for six hours after the operation.

Results:

In early post-operative period, peak CKMB levels were high in non-GIK group 48.50±19.79 IU/L versus 33.40±14.69 IU/L in GIK group (p-value <0.001). There was no statistically significant difference in requirements of inotropic support between the groups. The mean duration of inotropic support in GIK group was only 5.50±6.88 hours in GIK group and 8.64±7.74 hours in non-GIK group (p-value 0.008). Mean ventilation time in GIK group was 5.06±2.39 hours versus 6.55±3.58 hours in non-GIK group (p-value 0.002). Similarly, ICU stay period was also shorter in GIK group (p-value 0.01). We did not found any detrimental effect of GIK infusion on non-cardiac complications e.g. renal, pulmonary and neurologic complications.

Conclusion:

Glucose-insulin-potassium (GIK) infusion has a beneficial role in myocardial protection and is associated with better post-operative outcomes without increasing the risk of non-cardiac complications.

Insulin Therapy and In-Hospital Mortality in Critically Ill Patients: Systematic Review and Meta-analysis of Randomized Controlled Trials

BACKGROUND

Hyperglycemia is common in critically ill hospitalized patients and has been associated with adverse outcomes, including increased mortality. In this review, we examine the effect of insulin therapy on mortality in critically ill patients.

METHODS

We updated our previous systematic review and meta-analysis to include recently published trials that report data on the effect of insulin therapy initiated during hospitalization on mortality in adult patients with a critical illness. We also include a short primer on the methods of systematic reviews and meta-analyses, outlining the specific steps and challenges of this methodology. We performed an electronic search in the English language of MEDLINE and the Cochrane Controlled Clinical Trials Register and a hand search of key journals and relevant review articles for randomized controlled trials that reported mortality data on critically ill hospitalized adult patients treated with insulin (regardless of method of administration).

RESULTS

We identified 38 relevant studies that entered the analysis. We found that therapy with insulin in adult patients hospitalized for a critical illness, other than hyperglycemic crises, may decrease mortality in certain groups of patients. The beneficial effect of insulin was evident in the surgical intensive care unit (relative risk [RR], 0.58; confidence interval [CI], 0.22-0.62) and in patients with diabetes (RR, 0.76; CI, 0.62-0.92). There was a trend toward benefit in patients with acute myocardial infarction (RR, 0.89; CI, 0.76-1.03). Targeting euglycemia appears to be the main determinant of the benefit of insulin therapy (RR, 0.73; CI, 0.57-0.94).

CONCLUSIONS

Insulin therapy in adult patients hospitalized for a critical illness, other than hyperglycemic crises, may decrease mortality in certain groups of patients.

The effect of perioperative insulin treatment on cardiodepression in mild adiposity in mice

Background

While most studies focus on cardiovascular morbidity following anesthesia and surgery in excessive obesity, it is unknown whether these intraoperative cardiovascular alterations also occur in milder forms of adiposity without type 2 diabetes and if insulin is a possible treatment to improve intraoperative myocardial performance. In this experimental study we investigated whether mild adiposity without metabolic alterations is already associated with cardiometabolic dysfunction during anesthesia, mechanical ventilation and surgery and whether these myocardial alterations can be neutralized by intraoperative insulin treatment.

Methods

Mice were fed a western (WD) or control diet (CD) for 4 weeks. After metabolic profiling, mice underwent general anesthesia, mechanical ventilation and surgery. Cardiac function was determined with echocardiography and left-ventricular pressure–volume analysis. Myocardial perfusion was determined with contrast-enhanced echocardiography. WD-fed mice were subsequently treated with insulin by hyperinsulinemic euglycemic clamping followed by the same measurements of cardiac function and perfusion.

Results

Western-type diet feeding led to a 13 % increase in bodyweight, (p < 0.0001) and increased adipose tissue mass, without metabolic alterations. Despite this mild phenotype, WD-fed mice had decreased systolic and diastolic function (end-systolic elastance was 2.0 ± 0.5 versus 4.1 ± 2.4 mmHg/μL, p = 0.01 and diastolic beta was 0.07 ± 0.03 versus 0.04 ± 0.01 mmHg/μL, p = 0.02) compared to CD-fed mice. Ventriculo-arterial coupling and myocardial perfusion were decreased by 48 % (p = 0.003) and 43 % (p = 0.03) respectively. Insulin treatment in WD-fed mice improved echo-derived systolic function (fractional shortening 42 ± 5 % to 46 ± 3, p = 0.05), likely due to decreased afterload, but there was no effect on load-independent measures of systolic function or myocardial perfusion. However, there was a trend towards improved diastolic function after insulin treatment (43 % improvement, p = 0.05) in WD-fed mice.

Conclusions

Mild adiposity without metabolic alterations already affected cardiac function and perfusion during anesthesia, mechanical ventilation and surgery in mice. Intraoperative insulin may be beneficial to reduce afterload and enhance intraoperative ventricular relaxation, but not to improve ventricular contractility or myocardial perfusion.

Glucose-Insulin-Potassium Techniques in Cardiac Surgery: Historical Overview and Future Perspectives

Since the days of the first cardiac surgical operations in the previous century, myocardial preservation has been an essential component of the successful outcome of these procedures. Although many different techniques to achieve myocardial preservation and modulation have been described in the past 50 years, this review focuses on the use of glucose, insulin, and potassium (GIK) and its effect on ischemic and postischemic myocardium.

Hyperinsulinemic Normoglycemia Does Not Meaningfully Improve Myocardial Performance during Cardiac Surgery: A Randomized Trial

BACKGROUND

Glucose-insulin-potassium (GIK) administration during cardiac surgery inconsistently improves myocardial function, perhaps because hyperglycemia negates the beneficial effects of GIK. The hyperinsulinemic normoglycemic clamp (HNC) technique may better enhance the myocardial benefits of GIK. The authors extended previous GIK investigations by (1) targeting normoglycemia while administering a GIK infusion (HNC); (2) using improved echocardiographic measures of myocardial deformation, specifically myocardial longitudinal strain and strain rate; and (3) assessing the activation of glucose metabolic pathways.

METHODS

A total of 100 patients having aortic valve replacement for aortic stenosis were randomly assigned to HNC (high-dose insulin with concomitant glucose infusion titrated to normoglycemia) versus standard therapy (insulin treatment if glucose >150 mg/dl). The primary outcomes were left ventricular longitudinal strain and strain rate, assessed using speckle-tracking echocardiography. Right atrial tissue was analyzed for activation of glycolysis/pyruvate oxidation and alternative metabolic pathways.

RESULTS

Time-weighted mean glucose concentrations were lower with HNC (127 ± 19 mg/dl) than standard care (177 ± 41 mg/dl; P < 0.001). Echocardiographic data were adequate in 72 patients for strain analysis and 67 patients for strain rate analysis. HNC did not improve myocardial strain, with an HNC minus standard therapy difference of -1.2% (97.5% CI, -2.9 to 0.5%; P = 0.11). Strain rate was significantly better, but by a clinically unimportant amount: -0.16 s (-0.30 to -0.03 s; P = 0.007). There was no evidence of increased glycolytic, pyruvate oxidation, or hexosamine biosynthetic pathway activation in right atrial samples (HNC, n = 20; standard therapy, 22).

CONCLUSION

Administration of glucose and insulin while targeting normoglycemia during aortic valve replacement did not meaningfully improve myocardial function.

Remote conditioning the heart overview: translatability and mechanism

Conditioning the heart to resist predictable and unpredictable ischaemia-reperfusion (IR) injury is one of the fastest growing areas of bench to bedside research within cardiology. Basic science has provided important insights into signalling pathways and protective mechanisms in the heart, and a growing number of clinical studies have, with important exceptions, shown the potential applicability and beneficial effect of various mechanical conditioning strategies achieved by intermittent short-lasting-induced ischaemia of the heart itself or a remote tissue. Remote ischaemic conditioning (RIC) in particular has been utilized in a number of clinical settings with promising results. However, while many novel 'downstream' mechanisms of RIC have been discovered, translation to pharmacological conditioning has not yet been convincingly demonstrated in clinical studies. One explanation for this apparent failure may be that most pharmacological approaches mimic a single instrument in a complex orchestra activated by mechanical conditioning. Recent studies, however, provide important insights into upstream events occurring in RIC, which may allow for development of drugs activating more complex systems of biological organ protection. With this review, we will systematically examine the first generation of pharmacological cardioprotection studies and then provide a summary of the recent discoveries in basic science that could illuminate the path towards more advanced approaches in the next generation of pharmacological agents that may work by reproducing the diverse effects of RIC, thereby providing protection against IR injury.

Diabetic control and coronary artery bypass: effect on short-term outcomes

AIM

To evaluate the effect of preoperative glycemic control on hospital morbidity and mortality in diabetic patients undergoing primary coronary artery bypass grafting.

METHODS

Data of 3857 patients undergoing primary coronary artery bypass grafting was prospectively collected and retrospectively analyzed. There were 1109 (29%) diabetic patients, of whom 712 (64%) had hemoglobin A1c levels recorded. They were categorized by diabetic treatment: diet (179), oral hypoglycemic agent, (718) or insulin (212); and by diabetic control: hemoglobin A1c < 7 (265) or ≥7 (447). Nondiabetic patients (2,748) were used as controls.

RESULTS

The preoperative risk factors of hypertension (p < 0.001), hyperlipidemia (p < 0.001), renal failure (p < 0.04), peripheral vascular disease (p < 0.001), and chronic obstructive pulmonary disease (p < 0.04) were significantly more prevalent in diabetic patients. Major complications were not significantly different between the diabetic and control groups (p = 0.33), but minor complications were less frequent in diabetic patients (p = 0.03). Major and minor complications were not significantly different among the treatment subgroups of diabetic patients (p = 0.74 and p = 0.48) or in those with hemoglobin A1c < 7 and ≥7 (p = 0.23, p = 0.41).

CONCLUSIONS

Short-term outcomes were not affected by the degree of preoperative glycemic control or type of treatment used in diabetic patients undergoing primary coronary artery bypass grafting. A plausible explanation is strict protocol-driven glycemic control in the perioperative period.

Change in the perioperative blood glucose and blood lactate levels of non-diabetic patients undergoing coronary bypass surgery

In the present study, a retrospective analysis of the trends and factors affecting blood glucose and blood lactate levels was carried out for non-diabetic adult patients who had undergone coronary artery bypass graft (CABG) surgery. Between October 2009 and October 2011, 200 non-diabetic adult patients undergoing CABG surgery were examined. Glucose and lactic acid levels were observed successively during surgery [following the induction of anesthesia, cardio-pulmonary bypass (CPB), aortic cross-clamping and aortic stop flow infusion], at the end of surgery and after surgery [1, 6, 12, 24 and 48 h after admission to the intensive care unit (ICU)]. The results of blood gas analyses and other related indicators for trend analysis were investigated. The peak blood glucose and blood lactate levels during CPB, as well as other CPB factors, were also analyzed. Following aortic cross-clamping, intraoperative blood glucose and blood lactate levels increased gradually with increasing operative time. Postoperatively, blood glucose and blood lactate levels continued to rise. Blood glucose and blood lactic acid levels during CPB were positively correlated. The blood glucose and blood lactate levels of non-diabetic adult patients undergoing CABG increased gradually with operative time following aortic cross-clamping. Moreover, blood glucose and blood lactate levels were positively correlated with the duration of CPB and duration of aortic cross-clamping.

Perioperative glycemic control

Perioperative hyperglycemia has potential significant adverse consequences of increased mortality and morbidity including surgical site infection, renal insufficiency and anemia requiring transfusion. Both diabetic and non-diabetic patients are affected adversely by perioperative hyperglycemia. However, these two subgroups do not necessarily benefit equally from perioperative glycemic control. Moreover, ideal target glucose range as well as the appropriate patient population(s) for whom glycemic control offers the most benefit have yet to be fully elucidated. However, there are clear potential adverse consequences of tight control such as hypoglycemia.

Perioperative glycaemic control for diabetic patients undergoing surgery

BACKGROUND

Patients with diabetes mellitus are at increased risk of postoperative complications. Data from randomised clinical trials and meta-analyses point to a potential benefit of intensive glycaemic control, targeting near-normal blood glucose, in patients with hyperglycaemia (with and without diabetes mellitus) being submitted to surgical procedures. However, there is limited evidence concerning this question in patients with diabetes mellitus undergoing surgery.

OBJECTIVES

To assess the effects of perioperative glycaemic control for diabetic patients undergoing surgery.

SEARCH METHODS

Trials were obtained from searches of The Cochrane Library, MEDLINE, EMBASE, LILACS, CINAHL and ISIS (all up to February 2012).

SELECTION CRITERIA

We included randomised controlled clinical trials that prespecified different targets of perioperative glycaemic control (intensive versus conventional or standard care)

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data and assessed risk of bias. We summarised studies using meta-analysis or descriptive methods.

MAIN RESULTS

Twelve trials randomised 694 diabetic participants to intensive control and 709 diabetic participants to conventional glycaemic control. The duration of the intervention ranged from just the duration of the surgical procedure up to 90 days. The number of participants ranged from 13 to 421, and the mean age was 64 years. Comparison of intensive with conventional glycaemic control demonstrated the following results for our predefined primary outcomes: analysis restricted to studies with low or unclear detection or attrition bias for infectious complications showed a risk ratio (RR) of 0.46 (95% confidence interval (CI) 0.18 to 1.18), P = 0.11, 627 participants, eight trials, moderate quality of the evidence (grading of recommendations assessment, development and evaluation - (GRADE)). Evaluation of death from any cause revealed a RR of 1.19 (95% CI 0.89 to 1.59), P = 0.24, 1365 participants, 11 trials, high quality of the evidence (GRADE).On the basis of a posthoc analysis, there is the hypothesis that intensive glycaemic control may increase the risk of hypoglycaemic episodes if longer-term outcome measures are analysed (RR 6.92, 95% CI 2.04 to 23.41), P = 0.002, 724 patients, three trials, low quality of the evidence (GRADE). Analysis of our predefined secondary outcomes revealed the following findings: cardiovascular events had a RR of 1.03 (95% CI 0.21 to 5.13), P = 0.97, 682 participants, six trials, moderate quality of the evidence (GRADE) when comparing the two treatment modalities; and renal failure also did not show significant differences between intensive and regular glucose control (RR 0.61, 95% CI 0.34 to 1.08), P = 0.09, 434 participants, two trials, moderate quality of the evidence (GRADE). We did not meta-analyse length of hospital stay and intensive care unit (ICU) stay due to substantial unexplained heterogeneity. Mean differences between intensive and regular glucose control groups ranged from -1.7 days to 2.1 days for ICU stay and between -8 days to 3.7 days for hospital stay (moderate quality of the evidence (GRADE)). One trial assessed health-related quality of life in 12/37 (32.4%) of participants in the intervention group and 13/44 (29.5%) of participants in the control group, and did not show an important difference (low quality of the evidence (GRADE)) in the measured physical health composite score of the short-form 12-item health survey (SF-12). None of the trials examined the effects of the interventions in terms of costs.

AUTHORS' CONCLUSIONS

The included trials did not demonstrate significant differences for most of the outcomes when targeting intensive perioperative glycaemic control compared with conventional glycaemic control in patients with diabetes mellitus. However, posthoc analysis indicated that intensive glycaemic control was associated with an increased number of patients experiencing hypoglycaemic episodes. Intensive glycaemic control protocols with near-normal blood glucose targets for patients with diabetes mellitus undergoing surgical procedures are currently not supported by an adequate scientific basis. We suggest that insulin treatment regimens, patient- and health-system relevant outcomes, and time points for outcome measures should be defined in a thorough and uniform way in future studies.

Preoperative hemoglobin A1c predicts atrial fibrillation after off-pump coronary bypass surgery

OBJECTIVE

Diabetes mellitus has been recognized as a risk factor for mortality and morbidity after coronary bypass grafting, but a significant association between diabetes mellitus and postoperative atrial fibrillation (AF) has not been found. Although a recent study demonstrated a potential link between preoperative hemoglobin A1c level and risk of postoperative AF, there has not been sufficient examination of this relationship. We aimed to investigate the association between preoperative hemoglobin A1c and AF after isolated off-pump coronary bypass grafting.

METHODS

Of 912 consecutive patients undergoing isolated coronary bypass surgery, 805 were retrospectively analyzed for AF after excluding the following 107 cases: emergency (n=81), chronic AF (n=18), and pacemaker rhythm (n=8). We performed a group analysis with hemoglobin A1c levels categorized into tertiles of the baseline distribution and a continuous analysis based on 1% increments in hemoglobin A1c levels. The cutoff points for the tertiles were as follows: lower, 3.8-5.6% (n=283); middle, 5.7-6.7% (n=282); upper, 6.8-11.4% (n=240).

RESULTS

AF occurred in 159 patients (19.8%) after surgery. The median value (25th-75th percentile) of preoperative hemoglobin A1c was significantly lower in patients who developed AF than in those who did not (5.8 (5.4-6.3) vs 6.1 (5.5-7.2), p=0.01). The incidence of postoperative AF was 28.3% (80/283) in the lower tertile, 17.4% (49/282) in the middle tertile, and 12.5% (30/240) in the upper tertile (p for trend=0.01). The unadjusted odds ratio (95% confidence interval) for the association between hemoglobin A1c and postoperative AF was 0.70 (0.61-0.83) per 1% increase and 0.42 (0.29-0.70) for the upper versus the lower tertile. This association persisted after adjustment for the univariate predictors (0.74 (0.60-0.92) per 1% increase; 0.54 (0.31-0.90) for upper vs lower tertile) and the known risk factors (0.78 (0.63-0.95) per 1% increase; 0.55 (0.35-0.88) for upper vs lower tertile). The area under the receiver operator characteristic curve (95% confidence interval) for preoperative hemoglobin A1c as a predictor of postoperative AF was 0.70 (0.65-0.75) (p=0.01).

CONCLUSIONS

Preoperative hemoglobin A1c independently predicts the occurrence of AF after isolated off-pump coronary bypass grafting.

Continuous glucose monitoring in patients undergoing cardiac surgery

OBJECTIVES

Hyperglycemia is a prominent feature among patients exposed to major stress such as in cardiac surgery. The implementation of a continuous glucose monitoring system (CGMS) for glucose monitoring during cardiac surgery was assessed.

SUBJECTS AND METHODS

Fifty-nine consecutive patients who underwent cardiac surgery were monitored by CGMS. Patients' fluid glucose content, drug requirements, and hemodynamic and physiologic parameters were evaluated.

RESULTS

Of the 59 patients, 32 completed the monitoring with CGMS. Patients were divided into three groups: diabetes patients, patients without diabetes history who developed significant hyperglycemia perioperatively, and patients who did not develop hyperglycemia. Hyperglycemia was most frequently observed postoperatively. Hyperglycemic patients required significantly more insulin (81±40 vs. 34±37 units, P=0.005) and experienced an increased early complication rate, although this difference was not significant. CGMS erroneously detected late-phase operative and immediate postoperative hypoglycemia in approximately one-third of patients as reflected from venous blood sample measurements.

CONCLUSIONS

CGMS enables close monitoring and optimal control of blood glucose among patients undergoing major cardiac surgery, although its reliability is limited during the cardiac surgery phase and in the early postoperative period, because of incorrect hypoglycemic readings.

High-dose insulin administration is associated with hypoaminoacidemia during cardiac surgery

Although the effects of insulin on glucose homeostasis are well recognized in surgical patients, its effect on perioperative protein metabolism has received little attention. The purpose of this study was to examine the effect of high-dose insulin therapy on the plasma concentrations of amino acids (AAs) in patients undergoing coronary artery bypass grafting surgery. We studied 20 nondiabetic patients scheduled for elective coronary artery bypass grafting surgery. Patients were randomly allocated to receive either standard metabolic care (target glycemia 6.0-10.0 mmol/L, control group, n = 10) or high-dose insulin therapy (insulin group, n = 10). Insulin was administered at 5 mU·kg(-1)·min(-1) beginning at skin incision. Simultaneously, 20% dextrose was infused at a variable rate adjusted to maintain glycemia between 4.0 and 6.0 mmol/L. Plasma AAs, glucose, cortisol, and insulin were measured immediately before surgery and at sternal closure. Differences in mean values were assessed by Student t test. Plasma concentrations of all AAs decreased in the insulin group, with 15 of 22 AAs, including all branched-chain AAs, being significantly lower at sternal closure when compared with the control group. At the end of surgery, plasma glucose concentration was significantly lower in the insulin group (4.2 ± 0.6 vs 7.3 ± 1.0 mmol/L, P = .0001), whereas plasma cortisol levels did not show any difference between groups. High-dose insulin therapy resulted in a significant reduction in plasma AAs, particularly branched-chain AAs, during cardiac surgery.

The effect of insulin on the heart : Part 1: Effects on metabolism and function

Positive inotropic effects of insulin were described early after the isolation of insulin from the pancreas but data on the effect of insulin on the heart are conflicting. Systemic insulin administration results in a reduction in circulating free fatty acids and an improvement in myocardial glucose uptake, which causes an efficiency improvement in the myocardial cell. There is strong evidence that insulin administration results in functional improvement in dysfunctional myocardium. (Neth Heart J 2010;18:197-201.).

Effect of glucose-insulin-potassium infusion on mortality in critical care settings: a systematic review and meta-analysis

This study seeks to measure the treatment effect of glucose-insulin-potassium (GIK) infusion on mortality in critically ill patients. A systematic review of randomized controlled trials is conducted, comparing GIK treatment with standard care or placebo in critically ill adult patients. The primary outcome variable is mortality. Two authors independently extract data and assess study quality. The primary analysis is based on the random effects model to produce pooled odds ratios (ORs) with 95% confidence intervals (CIs). The search yields 1720 potential publications; 23 studies are included in the final analysis, providing a sample of 22,525 patients. The combined results demonstrate no heterogeneity (P=.57, I2=0%) and no effect on mortality (OR=1.02; 95% CI, 0.93-1.11) with GIK treatment. No experimental studies of shock or sepsis populations are identified. This meta-analysis finds that there is no mortality benefit to GIK infusion in critically ill patients; however, study populations are limited to acute myocardial infarction and cardiovascular surgery patients. No studies are identified using GIK in patients with septic shock or other forms of circulatory shock, providing an absence of evidence regarding the effect of GIK as a therapy in patients with shock.

Elevated preoperative hemoglobin A1c level is predictive of adverse events after coronary artery bypass surgery

OBJECTIVE

Diabetes mellitus has been associated with an increased risk of adverse outcomes after coronary artery bypass grafting. Hemoglobin A1c is a reliable measure of long-term glucose control. It is unknown whether adequacy of diabetic control, measured by hemoglobin A1c, is a predictor of adverse outcomes after coronary artery bypass grafting.

METHODS

Of 3555 consecutive patients who underwent primary, elective coronary artery bypass grafting at a single academic center from April 1, 2002, to June 30, 2006, 3089 (86.9%) had preoperative hemoglobin A1c levels obtained and entered prospectively into a computerized database. All patients were treated with a perioperative intravenous insulin protocol. A multivariable logistic regression model was used to determine whether hemoglobin A1c, as a continuous variable, was associated with in-hospital mortality, renal failure, cerebrovascular accident, myocardial infarction, and deep sternal wound infection after coronary artery bypass grafting. Receiver operating characteristic curve analysis identified the hemoglobin A1c value that maximally discriminated outcome dichotomies.

RESULTS

In-hospital mortality for all patients was 1.0% (31/3089). An elevated hemoglobin A1c level predicted in-hospital mortality after coronary artery bypass grafting (odds ratio 1.40 per unit increase, P = .019). Receiver operating characteristic curve analysis revealed that hemoglobin A1c greater than 8.6% was associated with a 4-fold increase in mortality. For each unit increase in hemoglobin A1c, there was a significantly increased risk of myocardial infarction and deep sternal wound infection. By using receiver operating characteristic value thresholds, renal failure (threshold 6.7, odds ratio 2.1), cerebrovascular accident (threshold 7.6, odds ratio 2.24), and deep sternal wound infection (threshold 7.8, odds ratio 5.29) occurred more commonly in patients with elevated hemoglobin A1c.

CONCLUSION

Elevated hemoglobin A1c level was strongly associated with adverse events after coronary artery bypass grafting. Preoperative hemoglobin A1c testing may allow for more accurate risk stratification in patients undergoing coronary artery bypass grafting.

Designing and implementing insulin infusion protocols and order sets

Influential trials and guidelines supporting the value of glucose control in hospital settings, particularly in the intensive care and postoperative settings, has led to the widespread adoption of intravenous infusions of human regular insulin. As groups have attempted to study the outcomes or to explore improved methods for improved glucose control, a number of insulin infusion protocols (IIPs) have been reported and validated. Now, many institutions are attempting to translate this experience into clinical practice in a systematic manner. The intent of this discussion is to highlight the authors' practical view of best practices in development and use of IIPs. As the implementation of IIPs has progressed, it has become apparent that this is not a simple process. It requires a carefully planned, inclusive, and continuous effort striving to attain effective glucose control while avoiding severe hypoglycemia. Whereas there are limitations in the literature comparing the IIPs, we identify design elements and implementation methods that increase the chances for staff acceptance and safe attainment of glycemic goals. Most importantly, this must be a team effort with attention to the numerous potential pitfalls that can disrupt the process and place patients at risk. In many cases, it is best to start more conservatively and methodically intensify the protocol. Continuous assessment of protocol errors, adverse events, staff satisfaction, and outcomes is vital to overall success.

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.

Angiotensin-converting enzyme inhibition after experimental myocardial infarct: role of the kinin B1 and B2 receptors

We sought to define the contribution of each of the 2 kinin receptors (bradykinin 1 receptor [B(1)R] and bradykinin 2 receptor [B(2)R]) to the cardioprotection of angiotensin-converting enzyme (ACE) inhibition after acute myocardial infarct. Wild-type mice and gene knockout mice missing either B(1)R or B(2)R were submitted to coronary ligation with or without concurrent ACE inhibition and had evaluation of left ventricular systolic capacity by assessment of fractional shortening (FS). Baseline FS was similar in all of the animals and remained unchanged in sham-operated ones. At 3 weeks after myocardial infarct, in the wild-type group there was a 27% reduction of FS (P<0.5) without ACE inhibition and 8% with ACE inhibition; in the B(1)R(-/-) groups the FS was reduced by 24% and was no different (at 28%) with ACE inhibition; in the B(2)R(-/-) groups, however, the FS was decreased by 39% and with ACE inhibition was decreased further by 52%. Analysis of bradykinin receptor gene expression in hearts showed that when one receptor was missing, the other became significantly upregulated; but the B(1)R remained highly overexpressed in the B(2)R(-/-) mice throughout, whereas the overexpressed B(2)R became significantly suppressed in the B(1)R(-/-) mice in a manner quantitatively and directionally similar to that of wild-type mice. We conclude that both bradykinin receptors contribute to the cardioprotective bradykinin-mediated effect of ACE inhibition, not only the B(2)R as believed previously; but, whereas with potentiated bradykinin in the absence of B(1)R, the upregulation of B(2)R is simply insufficient to provide full cardioprotection, in the absence of B(2)R, the upregulated B(1)R actually seems to inflict further tissue damage.

Real-time monitoring of cardiac metabolism using biosensors shows myocardial protection during ischemia-reperfusion injury with glucose-insulin-potassium administration

BACKGROUND

Systemic infusion of glucose-insulin-potassium (GIK) is thought to confer myocardial protection during ischemia-reperfusion injury. Our laboratory has experience with real-time monitoring of glucose and pH levels using needle-mounted biosensors. We tested the hypothesis that GIK enhances myocardial metabolism as displayed by real-time myocardial metabolic monitoring.

METHODS

A total of 40 kg male swine were randomized to receive GIK (n = 7) or lactated Ringer's (n = 7) solution intravenously at 1.5 mL/kg/hour. Ischemia was induced in the left anterior distribution (LAD) by 20 minutes LAD occlusion, followed by 20 minutes reperfusion. Hearts were instrumented anteriorly and posteriorly with continuously recording myocardial pH and glucose biosensors. Biopsies from the LAD distribution were taken at baseline, maximum ischemia, and after reperfusion to assess cardiac adenosine triphosphate (ATP) levels.

RESULTS

GIK animals had less myocardial pH decrease than controls during both ischemia (pH decrease -0.03 vs -0.37, P = .04) and reperfusion (pH decrease -0.10 vs -0.44, P = .05). Neither ATP (74% vs 73% decrease from baseline) nor glucose (27% vs 33% decrease from baseline) varied significantly between groups during ischemia. GIK animals had faster normalization of ATP (100% vs 79% increase from ischemia) and glucose (69% vs 28% increase from ischemia) during reperfusion.

CONCLUSIONS

Real-time myocardial metabolic monitoring shows that cardiac pH is improved by GIK during ischemia-reperfusion injury; however, ATP and glucose levels were not significantly enhanced. GIK animals trended toward earlier recovery during reperfusion. Mediators of this metabolic enhancement need to be explored.

Glucose and insulin improve cardiac efficiency and postischemic functional recovery in perfused hearts from type 2 diabetic (db/db) mice

Hearts from type 2 diabetic (db/db) mice demonstrate altered substrate utilization with high rates of fatty acid oxidation, decreased functional recovery following ischemia, and reduced cardiac efficiency. Although db/db mice show overall insulin resistance in vivo, we recently reported that insulin induces a marked shift toward glucose oxidation in isolated perfused db/db hearts. We hypothesize that such a shift in metabolism should improve cardiac efficiency and consequently increase functional recovery following low-flow ischemia. Hearts from db/db and nondiabetic (db/+) mice were perfused with 0.7 mM palmitate plus either 5 mM glucose (G), 5 mM glucose and 300 microU/ml insulin (GI), or 33 mM glucose and 900 microU/ml insulin (HGHI). Substrate oxidation and postischemic recovery were only moderately affected by GI and HGHI in db/+ hearts. In contrast, GI and particularly HGHI markedly increased glucose oxidation and improved postischemic functional recovery in db/db hearts. Cardiac efficiency was significantly improved in db/db, but not in db/+ hearts, in the presence of HGHI. In conclusion, insulin and glucose normalize cardiac metabolism, restore efficiency, and improve postischemic recovery in type 2 diabetic mouse hearts. These findings may in part explain the beneficial effect of glucose-insulin-potassium therapy in diabetic patients with cardiac complications.

Diastolic Dysfunction After Coronary Artery Bypass Grafting?The Effect of Glucose-Insulin-Potassium Infusion

BACKGROUND

Glucose-insulin-potassium (GIK) infusion improves clinical outcome after coronary artery bypass surgery (CABG). The mechanism of benefit is unclear, but GIK limits ischemia and reperfusion injury. This study was designed to assess whether the clinical benefit of perioperative GIK infusion is mediated through reduction in the severity of diastolic dysfunction that occurs after CABG.

METHODS AND RESULTS

Thirty-one patients undergoing CABG were randomized to GIK infusion (n = 14) or no-GIK (n = 17). Left ventricular compliance, using pressure-area relationships, was assessed by simultaneous transesophageal echocardiographic measurement of LV end-diastolic area (LVEDA) and pulmonary capillary wedge pressure (PCWP) at baseline prior to CABG, early post cardiopulmonary bypass (CPB), after sternal closure, and 3 hours postoperatively. Measures of LVEDA were made at a constant PCWP and a decrease in LVEDA reflects a leftward shift in the pressure-area relationship consistent with decreased compliance. Both study groups demonstrated progressive and consistent worsening of LV compliance, as evidenced by a reduction of LVEDA from 17.0 +/- 3.9 cm(2) at baseline to 15.3 +/- 3.6 cm(2) after CPB, 14.6 +/- 2.9 cm(2) after sternal closure, and 14.1 +/- 3.2 cm(2) (p < 0.0001) at three hours postoperatively. LVEDA decreased from a baseline of 16.3 +/- 2.8 to 13.8 +/- 2.9 cm(2) in the GIK group, while the non-GIK group demonstrated a reduction of LVEDA from 17.5 +/- 4.6 to 14.3 +/- 3.5 cm(2). Doppler transmitral E wave deceleration time shortened as well, which is consistent with more restrictive LV filling due to rapid equilibration of LA and LV pressures. GIK infusion did not alter either measure of diastolic function significantly.

CONCLUSION

Diastolic dysfunction occurs nearly universally after CABG, worsens with chest closure, persists for up to 3 hours postoperatively, and is unaffected by GIK. Despite theoretical reasons why GIK might limit ischemia and reperfusion injury, the clinical benefits do not appear to be related to amelioration of diastolic dysfunction.

SUPPORT

The study was partially supported by Agilent Technologies/Philips Imaging.

Practical aspects of intensive insulinization in the intensive care unit

PURPOSE OF REVIEW

Strategies used for intensive insulin therapy of critically ill patients and differences of approach according to medical condition are reviewed.

RECENT FINDINGS

Acceptance of proposed glycemic targets for critically ill patients has been tempered by uncertainties about benefit of strict glycemic control for specific target subpopulations, differences between treatment centers, optimal timing and duration of intervention, and safety. Present-day intravenous insulin infusion protocols may perform well only for restricted populations. Assessment of protocol performance requires knowledge of algorithm behavior on or near the narrow target range and, using the patient as unit of observation, examination of glycemic variability. Systems of the future will permit adjustment of algorithm parameters to meet individual- or population-specific targets and match carbohydrate exposure.

SUMMARY

Attainment and preservation of glycemic control among critically ill patients are best attempted with intravenous insulin infusion. Advances in the design of decision support and insulin delivery systems, and progress in the technology of continuous blood glucose monitoring, are likely to reduce the risk of hypoglycemia, without compromise of target range control, such that the patient outcomes enjoyed by experienced centers in the future will prove generalizable to others through the extension of new technologies.

Insulin-based regimens decrease mortality rates in critically ill patients: a systematic review

OBJECTIVES

To determine whether treatment with glucose-insulin-potassium (GIK), insulin and glucose, or insulin by itself is beneficial in limiting organ damage after acute myocardial infarction (AMI) and reducing mortality and morbidity among critically ill hyperglycaemic patients.

METHODS

Systematic review of randomized controlled trials.

MAIN OUTCOME MEASURE

To assess whether tight glycaemic control reduces morbidity and mortality.

STUDIES REVIEWED

Randomized controlled trials of insulin-based regimens in the treatment of critically ill patients.

RESULTS

Nine hundred and twenty-four potentially relevant studies were identified and screened for retrieval. Of these, 16 randomized controlled trials met the inclusion criteria (Table 1). Ten studies examined the effects of GIK, and six of these studies reported a mortality reduction with GIK treatment in addition to enhanced myocardial performance. Five studies examined the administration of insulin. Among these studies, tight glycaemic control of blood glucose in one study was shown to reduce morbidity and mortality of patients in intensive care. Only one study examined insulin/glucose therapy, and it showed a post-myocardial infarction mortality reduction of one year.

CONCLUSIONS

There is increasing evidence that maintaining normoglycaemia and treatment with insulin-based regimens is beneficial in limiting organ damage and significantly reduces both morbidity and mortality in critically ill patients who require intensive care therapy.

Glycaemic control in critically ill patients with cardiovascular disease

PURPOSE OF REVIEW

The role of hyperglycaemia in the pathogenesis of myocardial damage during cardiac surgery or patients with acute coronary syndromes has been the subject of increasing interest over the past few years. Several further trials and meta-analyses investigating the role of insulin treatment, either aimed at tight control of blood glucose concentration or as part of a regimen including glucose and potassium, have been reported recently and are the subject of this review.

RECENT FINDINGS

Good control of blood glucose has been demonstrated to improve outcomes for diabetic patients undergoing cardiac surgery and following acute myocardial infarction. In surgical intensive care patients, tight glucose control improved mortality--a finding that is awaiting confirmation in multicentre studies. The use of glucose-insulin-potassium regimens does not improve outcomes in patients with acute myocardial infarction who have undergone reperfusion therapy, but may be beneficial during cardiac surgery.

SUMMARY

Tight control of blood glucose has been shown to be beneficial in several patient groups. The optimal target glucose concentration and glucose and insulin regimens remain to be confirmed or determined in each clinical situation.

Considerations in prevention of surgical site infections following cardiac surgery: when your patient is diabetic

The incidence of surgical site infections among patients with diabetes continues to occur at a greater rate when compared with their nondiabetic counterparts. Preexisting vascular changes, delayed wound healing, and impaired immune factors contribute. Adult patients with diabetes likely possess comorbid coronary artery disease, thus increasing the need for cardiac surgery. The resultant potential for infection can be combated with supplementary interventions above those universally taken. Modifiable risk factors of hyperglycemia and obesity are targeted preoperatively. Glycemic control, adequate tissue perfusion, and adjunct use of nasal mupirocin are addressed intraoperatively. Lastly, focus is placed on nutrition, exercise, and continued glucose control postoperatively and beyond discharge.

Intravenous glucose-insulin-potassium during off-pump coronary artery bypass surgery does not reduce myocardial injury

BACKGROUND

This randomized, double-blind, placebo-controlled study was designed to determine whether an intra-operative, intravenous infusion of glucose-insulin-potassium (GIK) could be helpful in the prevention of myocardial ischemia and in the maintenance of intra-operative cardiac performance in patients undergoing off-pump coronary artery bypass (OP-CAB) surgery.

METHODS

Eighty two adults undergoing elective OP-CAB surgery were randomly divided into two groups that received intravenously either 5% dextrose in water or GIK (50% dextrose in 500 ml of water; regular insulin, 125 IU; potassium, 80 mmol) at 0.75 ml/kg/h immediately before the induction of anesthesia to the end of surgery. To evaluate myocardial damage, creatine kinase MB and troponin T were measured before surgery, immediately after arrival in the intensive care unit and on the first post-operative day. To assess cardiac performance, hemodynamic data were obtained before and after the induction of anesthesia, before and after the bypass graft and after sternal closure. Blood glucose was measured at the same time.

RESULTS

There was no significant difference in cardiac enzymes, hemodynamic parameters and blood glucose between the two groups. The use of vasoactive, inotropic and/or anti-arrhythmic agents, insulin and supplemental glucose was not significantly different between the groups.

CONCLUSION

The results suggest that the intravenous administration of GIK during OP-CAB surgery neither reduces myocardial damage nor improves intra-operative cardiac performance in patients without contractile dysfunction.

How does glucose insulin potassium improve hemodynamic performance? Evidence for altered expression of beta-adrenoreceptor and calcium handling genes

BACKGROUND

Glucose insulin potassium (GIK) improves hemodynamic performance after coronary artery surgery (CABG). We investigated whether this is associated with changes in gene expression of beta1-adrenergic receptor (ADRB1) or other calcium handling proteins.

METHODS AND RESULTS

During a randomized double-blind placebo-controlled trial, 48 patients undergoing on-pump CABG, allocated to receive pre-ischemic placebo (5% dextrose) or GIK (40% dextrose, K+ 100 mmol.L(-1), insulin 70 u.L(-1); 0.75 mL.kg(-1).h(-1)) continued for 6 hours after the removal of the aortic cross-clamp (AXC), underwent left ventricular biopsy for analysis of specific mRNAs immediately before AXC, before release of AXC, and 10 minutes after reperfusion (placebo n=24, GIK n=24). GIK or placebo was infused for a mean of 79+/-21 minutes or 79+/-18 minutes pre-ischemia respectively. Serial hemodynamic measurements were performed. Biopsy samples were snap-frozen and stored at -80 degrees C, mRNA was extracted and TaqMan real-time polymerase chain reaction was performed to investigate expression of ADRB1, sarcoplasmic reticulum Ca-ATPase (SERCA2a), and phospholamban (PLB). GIK significantly increased cardiac index versus placebo (P=0.037). TaqMan reverse-transcriptase polymerase chain reaction showed significantly greater ADRB1 mRNA expression at all time points (4.9-fold, 7.4-fold, and 15.6-fold increase, respectively; P<0.001), significantly greater SERCA2a mRNA expression after reperfusion (13.2-fold; P<0.001), and increased PLB mRNA expression at pre-ischemia and reperfusion (P<0.001 for both time-points) in GIK groups versus placebo.

CONCLUSIONS

The beneficial hemodynamic effects of GIK therapy are associated with increased ADRB1 and SERCA2a mRNA expression. Further work is therefore warranted to investigate these mRNA effects at the protein level.

Glucose-insulin-potassium and tri-iodothyronine individually improve hemodynamic performance and are associated with reduced troponin I release after on-pump coronary artery bypass grafting

BACKGROUND

Both glucose-insulin-potassium (GIK) and tri-iodothyronine (T3) may improve cardiovascular performance after coronary artery surgery (CABG) but their effects have not been directly compared and the effects of combined treatment are unknown.

METHODS AND RESULTS

In 2 consecutive randomized double-blind placebo-controlled trials, in patients undergoing first time isolated on-pump CABG between January 2000 and September 2004, 440 patients were recruited and randomized to either placebo (5% dextrose) (n=160), GIK (40% dextrose, K+ 100 mmol.L(-1), insulin 70 u.L(-1)) (0.75 mL.kg(-1) h(-1)) (n=157), T3 (0.8 microg.kg(-1) followed by 0.113 microg.kg(-1) h(-1)) (n=63) or GIK+T3 (n=60). GIK/placebo therapy was administered from start of operation until 6 hours after removal of aortic cross-clamp (AXC) and T3/placebo was administered for a 6-hour period from removal of AXC. Serial hemodynamic measurements were taken up to 12 hours after removal of AXC and troponin I (cTnI) levels were assayed to 72 hours. Cardiac index (CI) was significantly increased in both the GIK and GIK/T3 group in the first 6 hours compared with placebo (P<0.001 for both) and T3 therapy (P=0.009 and 0.029, respectively). T3 therapy increased CI versus placebo between 6 and 12 hours after AXC removal (P=0.01) but combination therapy did not. Release of cTnI was lower in all treatment groups at 6 and 12 hours after removal of AXC.

CONCLUSIONS

Treatment with GIK, T3, and GIK/T3 improves hemodynamic performance and results in reduced cTnI release in patients undergoing on-pump CABG surgery. Combination therapy does not provide added hemodynamic effect.

Glucose-insulin-potassium echocardiography detects improved segmental myocardial function and viable tissue shortly after acute myocardial infarction

Previous studies showed that glucose-insulin-potassium (GIK) increases cardiac output in patients after cardiac surgery and improves segmental myocardial wall motion. We hypothesized that GIK improves regional wall motion, detects contractile reserve, and predicts functional recovery at follow-up to a similar extent as low-dose dobutamine (LDD) in patients with recent myocardial infarction. Forty-one patients underwent LDD and GIK echocardiography. Data were analyzed according to a 13-segment model. Segments were scored from 0 (normokinesia) to 2 (a-/dyskinesia). Wall motion score index was calculated for baseline and intervention. During GIK, wall motion score index improved from 0.60 +/- 0.25 to 0.39 +/- 0.20 (P < .0001) and from 0.58 +/- 0.25 to 0.39 +/- 0.21 (P < .0001) during LDD. Overall agreement between GIK and LDD echocardiography to detect contractile reserve (improvement of segmental function by >or= 1 point) was 93% with a kappa value of 0.88. Sensitivity, specificity, and positive and negative predictive values of GIK echocardiography to predict functional recovery at follow-up (mean time to follow-up, 13 months) were 74%, 84%, 85%, and 72% respectively, and values were similar to LDD echocardiography. Thus, GIK infusion improves regional left ventricular function and allows the detection of myocardial viability to a similar extent as LDD in patients shortly after infarction.

Hyperglycaemia in critically ill patients: marker or mediator of mortality?

Acute hyperglycaemia has been associated with complications, prolonged intensive care unit and hospital stay, and increased mortality. We made an inventory of the prevalence and prognostic value of hyperglycaemia, and of the effects of glucose control in different groups of critically ill patients. The prevalence of hyperglycaemia in critically ill patients, using stringent criteria, approaches 100%. An unambiguous negative correlation between hyperglycaemia and mortality has been described in various groups of critically ill patients. Although the available evidence remains inconsistent, there appears to be a favourable effect of glucose regulation. This effect on morbidity and mortality depends on patient characteristics. To be able to compare results of future studies involving glucose regulation, better definitions of hyperglycaemia (and consequently of normoglycaemia) and patient populations are needed.