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.

Increased Carotid Intima-Media Thickness was not Associated With Cognitive Dysfunction After Off-Pump Coronary Surgery in Older Adult Patients Without Carotid Stenosis

Increased carotid intima-media thickness (C-IMT), a marker of atherosclerosis, is known to be associated with cerebrovascular and cortical abnormalities and cognitive impairment. This prospective observational study investigated the association between increased C-IMT and postoperative cognitive dysfunction (POCD) in older adult patients undergoing off-pump coronary artery bypass surgery. A total of 201 patients (57 females, 144 males; >60 years) were classified into increased (n = 105) or normal (n = 96) C-IMT groups by a cut-off value of 0.9 mm (bilateral C-IMT mean). Cognitive function was serially assessed with the Korean Mini-Mental State Examination, and Korean Montreal Cognitive Assessment scores preoperatively and at 7 days and 3 months postoperatively. POCD was defined as the deterioration of 1 standard deviation in at least one of the postoperative tests compared with their corresponding baseline scores. Independent risk factors for POCD were evaluated using multivariable analysis. Overall, POCD occurred in 46 patients (23%) over the 3 months. The incidences of POCD at 7 days and 3 months after surgery were similar, and there was no difference in both Korean Mini-Mental State Examination and Korean Montreal Cognitive Assessment test scores before and after surgery between groups. Chronic obstructive lung disease and intraoperative hyperglycemia episodes (>180 mg/dL), but not increased C-IMT, were independent risk factors for POCD. Unlike in nonsurgical cohorts, increased C-IMT was not significantly associated with the occurrence of POCD in older adult patients undergoing off-pump coronary artery bypass surgery.

Myocardial Protection by Glucose-Insulin-Potassium in Moderate- to High-Risk Patients Undergoing Elective On-Pump Cardiac Surgery: A Randomized Controlled Trial

BACKGROUND

Low cardiac output syndrome is a main cause of death after cardiac surgery. We sought to assess the impact of glucose-insulin-potassium (GIK) to enhance myocardial protection in moderate- to high-risk patients undergoing on-pump heart surgery.

METHODS

A randomized controlled trial was performed in adult patients (Bernstein-Parsonnet score >7) scheduled for elective aortic valve replacement and/or coronary artery bypass surgery. Patients were randomized to GIK (20 IU of insulin, 10 mEq of potassium chloride in 50 mL of glucose 40%) or saline infusion given over 60 minutes on anesthetic induction. The primary end point was postcardiotomy ventricular dysfunction (PCVD), defined as new/worsening left ventricular dysfunction requiring inotropic support (≥120 minutes). Secondary end points were the intraoperative changes in left ventricular function as assessed by transoesophageal echocardiography, postoperative troponin levels, cardiovascular and respiratory complications, and intensive care unit and hospital length of stay.

RESULTS

From 224 randomized patients, 222 were analyzed (112 and 110 in the placebo and GIK groups, respectively). GIK pretreatment was associated with a reduced occurrence of PCVD (risk ratio [RR], 0.41; 95% confidence interval [CI], 0.25-0.66). In GIK-treated patients, the left systolic ventricular function was better preserved after weaning from bypass, plasma troponin levels were lower on the first postoperative day (2.9 ng·mL(-) [interquartile range {IQR}, 1.5-6.6] vs 4.3 ng·mL(-) [IQR, 2.4-8.2]), and cardiovascular (RR, 0.69; 95% CI, 0.50-0.89) and respiratory complications (RR, 0.5; 95% CI, 0.38-0.74) were reduced, along with a shorter length of stay in intensive care unit (3 days [IQR, 2-4] vs 3.5 days [IQR, 2-7]) and in hospital (14 days [IQR, 11-18.5] vs 16 days [IQR, 12.5-23.5]), compared with placebo-treated patients.

CONCLUSIONS

GIK pretreatment was shown to attenuate PCVD and to improve clinical outcome in moderate- to high-risk patients undergoing on-pump cardiac surgery.

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.

Evaluation of preoperative oral carbohydrate administration on insulin resistance in off-pump coronary artery bypass patients: A randomised trial

BACKGROUND

In fasting cardiac surgery patients, preoperative carbohydrate (CHO) drink intake attenuated insulin resistance and improved cardiac metabolism, although its beneficial effects were not evident after cardiac surgery possibly due to cardiopulmonary bypass-related extreme systemic inflammation.

OBJECTIVE

We aimed to evaluate whether preoperative CHO intake affected insulin resistance and free-fatty acid (FFA) concentrations in off-pump coronary revascularisation.

DESIGN

A randomised controlled trial.

SETTING

Primary care in a university hospital in Korea from January 2015 to July 2016.

PATIENTS

Sixty patients who underwent elective multi-vessel off-pump coronary revascularisation were randomised into two groups. Three patients were excluded from analysis and 57 patients completed study.

INTERVENTION

The CHO group received oral CHO (400 ml) the prior evening and 2 to 3 h before surgery, and the control group was fasted from food and water according to standard protocol.

MAIN OUTCOME MEASURES

Insulin resistance was assessed twice, after anaesthetic induction and after surgery via short insulin tolerance test. FFA, C-reactive protein and creatine kinase-myocardial band concentrations were determined serially for 48 h after surgery.

RESULTS

Insulin sensitivity was greater (P = 0.002) and plasma FFA concentrations were lower (P = 0.001) after anaesthetic induction in the CHO group compared with the Control group, although there were no intergroup differences after surgery. The postoperative peak creatine kinase-myocardial band concentration was significantly lower in the CHO group compared with the Control group [8.8 (5.4 to 18.2) vs. 6.4 (3.5 to 9.7) ng ml, P = 0.031].

CONCLUSION

A preoperative CHO supplement significantly reduced insulin resistance and FFA concentrations compared with fasting at the beginning of the surgery, but these benefits were lost after off-pump coronary revascularisation. Despite their transient nature, these beneficial effects resulted in less myocardial injury, mandating further studies focused on the impact of preoperative CHO on myocardial ischaemia and cardiac function after coronary revascularisation.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT 02330263.

Risk factors of postcardiotomy ventricular dysfunction in moderate-to-high risk patients undergoing open-heart surgery

Introduction:

Ventricular dysfunction requiring inotropic support frequently occurs after cardiac surgery, and the associated low cardiac output syndrome largely contributes to postoperative death. We aimed to study the incidence and potential risk factors of postcardiotomy ventricular dysfunction (PCVD) in moderate-to-high risk patients scheduled for open-heart surgery.

Methods:

Over a 5-year period, we prospectively enrolled 295 consecutive patients undergoing valve replacement for severe aortic stenosis or coronary artery bypass surgery who presented with Bernstein-Parsonnet scores >7. The primary outcome was the occurrence of PCVD as defined by the need for sustained inotropic drug support and by transesophageal echography. The secondary outcomes included in-hospital mortality and the incidence of any major adverse events as well as Intensive Care Unit (ICU) and hospital length of stay.

Results:

The incidence of PCVD was 28.4%. Patients with PCVD experienced higher in-hospital mortality (12.6% vs. 0.6% in patients without PCVD) with a higher incidence of cardiopulmonary and renal complications as well as a prolonged stay in ICU (median + 2 days). Myocardial infarct occurred more frequently in patients with PCVD than in those without PCVD (19 [30.2%] vs. 12 [7.6%]). By logistic regression analysis, we identified four independent predictors of PCVD: left ventricular ejection fraction <40% (odds ratio [OR] = 6.36; 95% confidence interval [CI], 2.59–15.60), age older than 75 years (OR = 3.35; 95% CI, 1.64–6.81), prolonged aortic clamping time (OR = 3.72; 95% CI, 1.66–8.36), and perioperative bleeding (OR = 2.33; 95% CI, 1.01–5.41). The infusion of glucose-insulin-potassium was associated with lower risk of PCVD (OR = 0.14; 95% CI, 0.06–0.33).

Conclusions:

This cohort study indicates that age, preoperative ventricular function, myocardial ischemic time, and perioperative bleeding are predictors of PCVD which is associated with poor clinical outcome.

O-GlcNAcylation and cardiovascular disease

The post-translational modification of serine and threonine residues of proteins found in numerous subcellular locations by O-linked N-acetylglucosamine (O-GlcNAc) is emerging as a key mediator of many cardiovascular pathophysiological processes. Early studies implicated increased protein O-GlcNAcylation as contributing to the cardiovascular complications associated with diabetes, whereas subsequent studies demonstrated that acute increases in O-GlcNAc levels were protective against ischemia/reperfusion injury. There is now a growing understanding that O-GlcNAc modification of proteins influences numerous cellular functions, including transcription, protein turnover, calcium handling, and bioenergetics. As a result, a more nuanced view of the role of protein O-GlcNAcylation in the cardiovascular system is emerging along with the recognition that it is required for normal cellular function and homeostasis. Consequently, the impact of changes in O-GlcNAc cycling due to stress or disease on the heart is complex and highly dependent on the specific context of these events. The goal of this review is to provide an overview of some of the more recent advances in our understanding of the role O-GlcNAcylation plays in mediating cardiovascular function and disease.

Experience using high-dose glucose-insulin-potassium (GIK) in critically ill patients

PURPOSE

To audit the use of GIK in terms of safety, haemodynamic effects, and impact on catecholamine dosage.

MATERIALS AND METHODS

A retrospective, descriptive, evaluative audit of GIK use within the adult ICU of a London teaching hospital was conducted. Rescue therapy of GIK (up to 1.0Unitsinsulin/kg/h) was administered to improve cardiac function. Outcomes were ICU survival, change in cardiac index (CI) and blood lactate levels, events of hypoglycaemia, hyperglycaemia, hypokalaemia and hyperkalaemia, and discontinuation time of catecholamine inotropes.

RESULTS

Of 85 patients treated with GIK, 13 (15.3%) survived their ICU stay and 9 (10.5%) were discharged home. In patients surviving until 72h, a trend of improved CI and lactate levels was seen, often with reductions in catecholamine dosing. Inotropes were discontinued in 35 (54%) patients. Severe hypoglycaemia (<2mmol/l), hyperglycaemia (>20mmol/l), hypokalaemia (<2.5mmol/l) and hyperkalaemia (>7mmol/l) during GIK affected 1, 6, 8 and 1 patients, respectively. These abnormalities were quickly identified. No measurable harm was noted.

CONCLUSIONS

High-dose GIK can be safely used in critically ill patients, though blood glucose and potassium levels must be monitored frequently. GIK was associated with improved CI and blood lactate levels. Impact on survival requires prospective evaluation.

Effect of glucose-insulin-potassium on hyperlactataemia in patients undergoing valvular heart surgery: A randomised controlled study

BACKGROUND

Hyperlactataemia represents oxygen imbalance in the tissues and its occurrence during cardiac surgery is associated with adverse outcomes. Glucose-insulin-potassium (GIK) infusion confers myocardial protection against ischaemia-reperfusion injury and has the potential to reduce lactate release while improving its clearance.

OBJECTIVES

The objective of this study is to compare the effect of GIK on the incidence of hyperlactataemia in patients undergoing valvular heart surgery.

DESIGN

A randomised controlled study.

SETTING

Single university teaching hospital.

PATIENTS

One hundred and six patients scheduled for elective valvular heart surgery with at least two of the known risk factors for hyperlactataemia.

INTERVENTION

Patients were randomly allocated to receive either GIK solution (insulin 0.1 IU kg(-1) h(-1) and an infusion of 30% dextrose and 80 mmol l(-1) potassium at 0.5 ml kg(-1) h(-1)) or 0.9% saline (control) throughout surgery.

MAIN OUTCOME MEASURES

The primary outcome was the incidence of hyperlactataemia (lactate ≥ 4 mmol l(-1)) during the operation and until 24 h after the operation. Secondary outcomes included haemodynamic parameters, use of vasopressor or inotropic drugs, and fluid balance until 24 h postoperatively. Postoperative morbidity endpoints were also assessed.

RESULTS

The incidences of hyperlactataemia were similar in the groups (32/53 patients in each of the control and GIK groups, P > 0.999). There were no intergroup differences in haemodynamic parameters, use of vasopressor and inotropic drugs, or fluid balance. The incidences of postoperative morbidity endpoints were similar in both groups.

CONCLUSION

Despite its theoretical advantage, GIK did not provide beneficial effects in terms of the incidence of hyperlactataemia or outcome in patients undergoing valvular heart surgery.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT01825720.

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.

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.

Anaesthetics-induced neurotoxicity in developing brain: an update on preclinical evidence

Every year millions of young people are treated with anaesthetic agents for surgery and sedation in a seemingly safe manner. However, growing and convincing preclinical evidence in rodents and nonhuman primates, together with recent epidemiological observations, suggest that exposure to anaesthetics in common clinical use can be neurotoxic to the developing brain and lead to long-term neurological sequelae. These findings have seriously questioned the safe use of general anaesthetics in obstetric and paediatric patients. The mechanisms and human applicability of anaesthetic neurotoxicity and neuroprotection have remained under intense investigation over the past decade. Ongoing pre-clinical investigation may have significant impact on clinical practice in the near future. This review represents recent developments in this rapidly emerging field. The aim is to summarise recently available laboratory data, especially those being published after 2010, in the field of anaesthetics-induced neurotoxicity and its impact on cognitive function. In addition, we will discuss recent findings in mechanisms of early-life anaesthetics-induced neurotoxicity, the role of human stem cell-derived models in detecting such toxicity, and new potential alleviating strategies.