Coronary revascularization: a procedure in transition from on-pump to off-pump? The role of glucose-insulin-potassium revisited in a randomized, placebo-controlled study

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.

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.

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.

Insulin infusion on postoperative complications of coronary artery bypass graft in patients with diabetes mellitus

Background:

Cardiovascular events are common in patients with diabetes mellitus (DM), which make coronary artery bypass graft (CABG) a highly demanded surgery in this population. Tight control of blood glucose in patients with DM is beneficial in reducing postoperative complications; however, the adequate range has not been determined yet.

Objectives:

This study aimed to investigate the effect of semi-tight (moderate) control of DM on complications and serum glucose levels during and after CABG.

Patients and Methods:

In this prospective clinical trial, 18 and 31 patients with and without DM, respectively, who were referred to Shahid Chamran Hospital, Isfahan, Iran, for elective CABG surgery, were enrolled. For DM group, patients with controlled DM (i.e. glycosylated hemoglobin levels [HgA1C] ≤ 7%) were recruited. Blood glucose level (blood sugar, BS) was measured after anesthesia, during pumping, warming, off pumping, six and 12 hours after Intensive Care Unit (ICU) admission, and at discharging from the hospital. The hemodynamic state of the patients, bleeding, need of blood transfusion, infection, and duration of hospitalization were also monitored and recorded.

Results:

None of the BS measurements (FBS, after anesthesia, on-pump, warming, off pump, six and 12 hours after ICU admission, and at discharge) were significantly different between study groups (P > 0.05). Frequency of surgery site bleeding and blood transfusion need were not significantly different between these groups (P > 0.05).

Conclusions:

Semi-tight control of DM with insulin infusion during operation did not led to any difference in the type and rate of CABG complications between patients with well-controlled and those without DM; however, BS levels in patients with well-controlled DM could be more easily controlled.

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.

Management of hyperglycemia during the perioperative period

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

Effect of perioperative glucose-insulin-potassium infusions on mortality and atrial fibrillation after coronary artery bypass grafting: a systematic review and meta-analysis

BACKGROUND

Glucose-insulin infusions (with potassium [GIK] or without [GI]) have been advocated in the setting of coronary artery bypass graft (CABG) surgery to optimize myocardial glucose use and to minimize ischemic injury.

OBJECTIVE

To conduct a meta-analysis assessing whether the use of GIKGI infusions perioperatively reduce in-hospital mortality or atrial fibrillation (AF) after CABG surgery.

METHODS

Electronic databases (Medline, EMBASE and Cochrane Central Register of Controlled Trials [CENTRAL]) and references of retrieved articles were searched for randomized controlled trials that evaluated the effects of GIK or GI infusions, before or during CABG surgery, on in-hospital mortality andor postoperative AF. Pooled ORs and 95% CIs were calculated for each outcome.

RESULTS

Twenty trials were identified and eligible for review. The summary OR for in-hospital mortality was 0.88 (95% CI 0.56 to 1.40), based on 44 deaths among 2326 patients. While postoperative AF was a more frequent outcome (occurring in 519 of 1540 patients in the 10 trials reporting this outcome), the overall pooled estimate of effect was nonsignificant (OR 0.79, 95% CI 0.54 to 1.15). This latter finding needs to be interpreted cautiously because it is accompanied by significant heterogeneity across trials.

CONCLUSIONS

Perioperative use of GIKGI does not significantly reduce mortality or atrial fibrillation in patients undergoing CABG surgery. Unless future trial data in support of GIKGI infusions become available, the routine use of these treatments in patients undergoing CABG surgery should be discouraged because the safety of these infusions has not been systematically examined.

Postoperative Functional Outcome After Off-Pump Versus On-Pump Coronary Artery Bypass Grafting Using Gated Myocardial SPECT: A Comparison by Propensity Score Analysis

PURPOSE

We evaluated the short-term and mid-term differences in perfusion and function after off-pump and on-pump coronary artery bypass grafting (CABG) using gated myocardial single photon emission computed tomography.

MATERIALS AND METHODS

A total of 70 patients with coronary artery disease who underwent CABG were included based on the propensity score matching results from 165 patients. Thirty-five patients underwent off-pump and 35 patients on-pump CABG. Rest (201)Tl/dipyridamole stress (99 m)Tc-methoxyisobutylisonitrile gated single photon emission computed tomographies were performed preoperatively and postoperatively at short-term (103 ± 23 days after surgery) and mid-term follow-up (502 ± 111 days after surgery). Changes in left ventricular ejection fraction, end systolic volume, stress and rest segmental perfusion, and segmental wall thickening were compared between the two groups. The segments with preoperative rest (201)Tl uptake under 60% of maximum uptake were included in the segmental analysis.

RESULTS

Left ventricular ejection fraction (P = 0.001) and end systolic volume (P = 0.008) showed significant improvement in both groups. There were no significant short-term and mid-term differences between the two groups in terms of left ventricular ejection fraction (P = 0.309) and end systolic volume (P = 0.938). Likewise, segmental rest (P = 0.178) and stress perfusion (P = 0.071), and systolic wall thickening (P = 0.241) showed significant improvement in both groups with similar time courses.

CONCLUSION

Off-pump CABG resulted in significant improvements in left ventricular ejection fraction, end systolic volume, and regional myocardial perfusion and function that are comparable to on-pump CABG at short-term and mid-term. Gated myocardial SPECT successfully revealed that off-pump CABG is as good as on-pump CABG from the viewpoint of myocardial perfusion and function.

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.

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.

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.

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.

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.

Effect of glucose-insulin-potassium infusion on myocardial damage due to percutaneous coronary revascularization

Percutaneous coronary intervention has been known to cause myocardial damage as a result of microvascular dysfunction due to microembolization and microinfarction. Previous studies have shown that glucose-insulin-potassium (GIK) infusion decreases mortality in patients with acute myocardial infarction. Therefore, in this study, we aimed to investigate the effect of GIK infusion on myocardial damage due to percutaneous coronary revascularization. A total of 52 consecutive nondiabetic patients diagnosed with non-ST-elevation acute coronary syndrome and designated for elective percutaneous coronary intervention were randomized in a double-blind fashion into GIK and normal saline groups. GIK infusion (30% dextrose, 300 U insulin, and 60 mEq potassium chloride) at a dose of 1.5 ml/kg/hour was initiated 24 hours before the intervention and continuing during and until 1 hour after the intervention. Troponin I levels were recorded in venous blood samples before and 12 and 24 hours after the intervention. The increase in troponin I was significantly lower at 12 and 24 hours in the GIK group compared with those of the saline controls (p=0.022 and p=0.005, respectively). GIK infusion initiated 24 hours before coronary stenting for non-ST-elevation acute coronary syndrome resulted in less myocardial damage as determined by postprocedure troponin I levels.

Glucose-Insulin-Potassium in Cardiac Surgery: A Meta-Analysis

BACKGROUND

Glucose-insulin-potassium therapy (GIK) has been suggested to reduce mortality and improve postoperative recovery after cardiac surgery. We performed a meta-analysis of all randomized studies using GIK in cardiac surgery.

METHODS

A systematic Medline search for all GIK studies in cardiac surgery was carried out. Randomized studies investigating the recovery of contractile function as a primary endpoint were included in the meta-analysis.

RESULTS

Thirty-five GIK trials were identified. Twenty-four studies were excluded because of lack of randomization, supplementary administration of other substances, or due to other primary endpoints. Eleven studies were included with a total of 468 patients who underwent either coronary artery bypass grafting or heart valve replacement. Six studies noted a significant improvement in postoperative recovery. One study demonstrated no effect. In four studies, no comparable statistical analysis was available. GIK patients required similar or lesser doses of catecholamines. From the available data we estimated a weighted mean of relative improvement in postoperative recovery of cardiac index for GIK patients versus controls of 11.4%. Five of 11 studies reported the incidence of postoperative atrial fibrillation (AF). AF occurred in 23% (20/86) in GIK versus 42% (36/86) in control patients (p = 0.009).

CONCLUSIONS

The findings indicate that GIK may considerably improve postoperative recovery of contractile function and reduce the incidence of atrial arrhythmias after cardiac surgery. However, several factors limit the power of this analysis and large, randomized multicenter trials are needed to fully assess the efficacy of GIK after cardiac surgery.

Off-pump coronary artery bypass surgery: physiology and anaesthetic management †

Increasing interest is being shown in beating heart (off-pump) coronary artery surgery (OPCAB) because, compared with operations performed with cardiopulmonary bypass, OPCAB surgery may be associated with decreased postoperative morbidity and reduced total costs. Its appears to produce better results than conventional surgery in high-risk patient populations, elderly patients, and those with compromised cardiac function or coagulation disorders. Recent improvements in the technique have resulted in the possibility of multiple-vessel grafting in all coronary territories, with a graft patency comparable with conventional surgery. During beating-heart surgery, anaesthetists face two problems: first, the maintenance of haemodynamic stability during heart enucleation necessary for accessing each coronary artery; and second, the management of intraoperative myocardial ischaemia when coronary flow must be interrupted during grafting. The anaesthetic technique is less important than adequate management of these two major constraints. However, experimental and recent clinical data suggest that volatile anaesthetics have a marked cardioprotective effect against ischaemia, and might be specifically indicated. OPCAB surgery requires team work between anaesthetists and surgeons, who must be aware of each other's constraints. Some surgical aspects of the operation are reviewed along with physiological and anaesthetic data.

Meta-analysis of short-term and mid-term outcomes following off-pump coronary artery bypass grafting

BACKGROUND

Uncertainty continues to surround the relative benefits and harms of conventional coronary artery bypass grafting (CABG) and off-pump coronary artery bypass grafting (OPCABG). Possible reasons are that high-quality studies have not comprehensively examined relevant patient outcomes and have enrolled a limited range of patients. Some studies may have been too small to detect clinically important differences in patient outcomes. The present study addresses these issues using meta-analysis.

METHODS

We comprehensively retrieved randomized and nonrandomized controlled studies according to predetermined criteria. We performed meta-analyses for each outcome and empirically determined whether potential biases that might result from differences in study design or patient characteristics actually biased a study's results. We also conducted sensitivity analyses and tested for publication bias.

RESULTS

Rates of perioperative myocardial infarction, stroke, reoperation for bleeding, renal failure, and mortality were lower after OPCABG than after CABG. Reductions in length of hospital stay, atrial fibrillation, and wound infection were also associated with OPCABG, but statistically significant differences among study results for these outcomes could not be explained by available information. Midterm (3 to 25 months) angina recurrence did not appear to differ between treatments; a trend was noticed toward lower reintervention rates with CABG, and a trend toward lower overall mortality with OPCABG, at least when performed at experienced centers. These midterm outcome results require confirmation.

CONCLUSIONS

Off-pump coronary artery bypass grafting appears to reduce length of hospital stay, operative morbidity, and operative mortality relative to on-pump CABG. More studies are required before firm conclusions can be drawn concerning the effect of OPCABG on midterm mortality, angina recurrence, and repeat intervention.

The influence of glucose-insulin-potassium (GIK) on the GH/IGF-1/IGFBP-1 axis during elective coronary artery bypass surgery

OBJECTIVES

To investigate the influence of glucose-insulin-potassium (GIK) on the growth hormone/insulin-like growth factor-1 axis.

DESIGN

Randomized clinical study.

SETTING

University hospital.

PARTICIPANTS

Twenty patients, without metabolic disorders, admitted for elective aortocoronary bypass surgery.

INTERVENTIONS

GIK therapy. Measurements and main results Blood samples were taken repeatedly during the day of surgery. Ejection fraction (EF) was determined by transesophageal echocardiography before and at the end of surgery. Blood samples were taken on the first postoperative day and at discharge (8 am and 8 pm). During coronary artery bypass graft (CABG) surgery, a rapid decrease (44%) in total IGF-1 occurred in both groups. Directly after cessation of extracorporeal circulation, there was a prompt rise in IGFBP-1. The mean peak value in the control group was more than 3 times higher than in the GIK group. GH secretion was stimulated by surgery in both groups and was enhanced by GIK. B-glucose was significantly higher in the control group during surgery. EF ( approximately 55% at baseline) was unchanged in both groups. Postoperatively, there were no differences between the groups (all parameters). At discharge, IGFBP-1 was unchanged, but insulin was elevated compared with preoperative levels. This was seen in both groups, reflecting a hepatic insulin resistance. Conclusions The authors conclude that GIK blunts the rise of IGFBP-1 and thereby increases the bioavailability of IGF-1. GIK also seems to speed up the return of IGF-1 to baseline. Both mechanisms could be of importance to catabolic high-risk patients with low IGF-1. Hence, GIK has favorable effects on the GH/IGF-1 axis during CABG surgery.