Intraoperative insulin therapy does not reduce the need for inotropic or antiarrhythmic therapy after cardiopulmonary bypass

Perioperative Glycemic Management in Cardiac Surgery: A Narrative Review

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

Calcium administration In patients undergoing CardiAc suRgery under cardiopulmonary bypasS (ICARUS trial): Rationale and design of a randomized controlled trial

Introduction

Weaning from cardiopulmonary bypass (CPB) is a critical step of any cardiac surgical procedure and often requires pharmacologic intervention. Calcium ions are pivotal elements for the excitation-contraction coupling process of cardiac myocytes. Thus, calcium administration might be helpful during weaning from CPB.

Methods

We describe a multicenter, placebo-controlled, double blind randomized clinical trial to assess the effect of calcium chloride on the need for inotropic support among adult patients during weaning from CPB. The experimental group (409 patients) will receive 15 mg/kg of calcium chloride. The control group (409 patients) will receive an equivalent volume of 0.9% sodium chloride. Both drugs will be administered intravenously as a bolus at the beginning of weaning from CPB.

Results

The primary outcome will be the need for inotropic support between termination of CPB and completion of surgery. Secondary outcomes will be: duration of inotropic support, vasoactive-inotropic score 30 min after transfer to intensive care unit and on postoperative day 1, plasma alpha-amylase on postoperative day 1, plasma Ca²⁺ concentration immediately before and 10–15 min after calcium chloride administration, non-fatal myocardial infarction, blood loss on postoperative day 1, need for transfusion of red blood cells, signs of myocardial ischemia on electrocardiogram after arrival to intensive care unit, all-cause mortality at 30 days or during hospital stay if this is longer than 30 days.

Discussion

This trial is designed to assess whether intravenous calcium chloride administration could reduce the need for inotropic support after cardiopulmonary bypass weaning among adults undergoing cardiac surgery.

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.

Effects of intensive glycemic control on outcomes of cardiac surgery

OBJECTIVES

To investigate the effects of postoperative intensive glycemic control on patient outcomes.

BACKGROUND

Ineffective perioperative glycemic control has been associated with high mortality and morbidity rates among cardiac surgery patients.

METHODS

212 cardiac surgery patients were allocated by a quasi-experimental design to: a) a control group (n = 107) with targeted blood glucose levels 161-200 mg/dl or b) a therapy group (n = 105) with blood glucose target 120-160 mg/dl. We compared the two groups on their mortality, length of stay, duration of intubation, incidence of severe hypoglycemia and frequency of postoperative infections.

RESULTS

The mean postoperative blood glucose levels were significantly lower for the therapy group compared with the control group (153.9 mg/dl vs. 173.9 md/dl, p < 0.001). The intensive glycemic control was strongly associated with decreased in-hospital mortality (7 deaths/105 patients for the control group vs. 1 death/105 patients for the therapy group; p = 0.033). We did not identify any statistically significant associations regarding the other patient outcomes.

CONCLUSIONS

This randomized quasi-experimental trial found lower in-hospital mortality with more intense blood glucose control. Effective postoperative glycemic control did not affect the other studied patient outcomes.

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.

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

BACKGROUND

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSION

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

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

BACKGROUND

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

METHOD

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

RESULTS

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

CONCLUSION

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Intraoperative Hemodynamic Instability During and After Separation From Cardiopulmonary Bypass

Every year, more than 1 million patients worldwide undergo cardiac surgery. Because of the aging of the population, cardiac surgery will increasingly be offered to patients at a higher risk of complications. The consequence is a reduced physiological reserve and hence an increased risk of mortality. These issues will have a significant impact on future health care costs because the population undergoing cardiac surgery will be older and more likely to develop postoperative complications. One of the most dreaded complications in cardiac surgery is difficult separation from cardiopulmonary bypass (CPB). When separation from CPB is associated with right-ventricular failure, the mortality rate will range from 44% to 86%. Therefore, the diagnosis and the preoperative prediction of difficult separation from CPB will be crucial to improve the selection and care of patients and to prevent complications for this high-risk patient population.

[Repercussions and management of perioperative hyperglycemia in cardiac surgery]

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

Intraoperative Management of Hyperglycemia in the Cardiac Surgical Patient

The stress response of cardiac surgery leads to hyperglycemia, and undergoing cardiopulmonary bypass magnifies this response greatly. Counter-regulatory hormones, the cytokine response, and the automatic nervous system are all part of the coordinated host response that can lead to hyperglycemia. Postoperative hyperglycemia is associated with worsened perioperative outcomes, and there are data demonstrating this to also be true for the intraoperative period. Many factors affect intraoperative glucose control, including cardiopulmonary pump (CPB) prime fluid composition, temperature while on CPB, and medications such as catecholamines and glucocorticoids. Intraoperative glucose control has a significant impact on postoperative outcomes. No optimal intraoperative insulin regimen has been identified, but continuous intravenous infusions appear to be superior to intermittent sliding scale dosing. In addition, the technique of hyperinsulinemic glucose clamp shows the greatest promise of achieving normoglycemia while on CPB.

Towards a feasible algorithm for tight glycaemic control in critically ill patients: a systematic review of the literature

Introduction

Tight glycaemic control is an important issue in the management of intensive care unit (ICU) patients. The glycaemic goals described by Van Den Berghe and colleagues in their landmark study of intensive insulin therapy appear difficult to achieve in a real life ICU setting. Most clinicians and nurses are concerned about a potentially increased frequency of severe hypoglycaemic episodes with more stringent glycaemic control. One of the steps we took before we implemented a glucose regulation protocol was to review published trials employing insulin/glucose algorithms in critically ill patients.

Methods

We conducted a search of the PubMed, Embase and Cochrane databases using the following terms: 'glucose', 'insulin', 'protocol', 'algorithm', 'nomogram', 'scheme', 'critically ill' and 'intensive care'. Our search was limited to clinical trials conducted in humans. The aim of the papers selected was required to be glycaemic control in critically ill patients; the blood glucose target was required to be 10 mmol/l or under (or use of a protocol that resulted in a mean blood glucose = 10 mmol/l). The studies were categorized according to patient type, desired range of blood glucose values, method of insulin administration, frequency of blood glucose control, time taken to achieve the desired range for glucose, proportion of patients with glucose in the desired range, mean blood glucose and frequency of hypoglycaemic episodes.

Results

A total of twenty-four reports satisfied our inclusion criteria. Most recent studies (nine) were conducted in an ICU; nine others were conducted in a perioperative setting and six were conducted in patients with acute myocardial infarction or stroke. Studies conducted before 2001 did not include normoglycaemia among their aims, which changed after publication of the study by Van Den Berghe and coworkers in 2001; glycaemic goals became tighter, with a target range between 4 and 8 mmol/l in most studies.

Conclusion

Studies using a dynamic scale protocol combining a tight glucose target and the last two blood glucose values to determine the insulin infusion rate yielded the best results in terms of glycaemic control and reported low frequencies of hypoglycaemic episodes.

Hyperglycemia is a marker for poor outcome in the postoperative pediatric cardiac patient

OBJECTIVE

Hyperglycemia in critical care populations has been shown to be a risk factor for increased morbidity and mortality. Minimal data exist in postoperative pediatric cardiac patients. The goal of this study was to determine whether hyperglycemia in the postoperative period was associated with increased morbidity or mortality.

DESIGN

Retrospective chart review.

SETTING

Tertiary care, free-standing pediatric medical center with a dedicated cardiac intensive care unit.

PATIENTS

We included 184 patients <1 yr of age who underwent cardiac surgery requiring cardiopulmonary bypass from October 2002 to August 2004. Patients with a weight <2 kg, a preoperative diagnosis of diabetes, preoperative extracorporeal membrane oxygenation support, solid organ transplant recipients, and preoperative renal or liver insufficiency were excluded.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Age was 4.3 +/- 3.2 months and weight was 4.9 +/- 1.7 kg at surgery. Duration of hyperglycemia was significantly longer in patients with renal insufficiency (p = .029), liver insufficiency (p = .006), infection (p < .002), central nervous system event (p = .038), extracorporeal membrane oxygenation use (p < .001), and death (p < .002). Duration of hyperglycemia was also significantly associated with increased intensive care (p < .001) and hospital (p < .001) stay and longer ventilator use (p < .001). Peak glucose levels were significantly different in patients with renal insufficiency (p < .001), infection (p = .002), central nervous system event (p = .01), and mortality (p < .001).

CONCLUSIONS

Hyperglycemia in the postoperative period was associated with increased morbidity and mortality in postoperative pediatric cardiac patient. Strict glycemic control may improve outcomes in this patient population.

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

OBJECTIVE

Hyperglycemia worsens outcomes in critical illness. This randomized, double-blind, placebo-controlled clinical trial tested whether insulin treatment of hyperglycemia during cardiopulmonary bypass would reduce neurologic, neuro-ophthalmologic, and neurobehavioral outcomes after coronary artery bypass grafting.

METHODS

Three hundred eighty-one nondiabetic patients undergoing isolated coronary artery bypass grafting were given infusions of insulin or placebo when their blood glucose concentration exceeded 100 mg/dL during cardiopulmonary bypass. The primary outcome measure was the combined incidence of new neurologic, neuro-ophthalmologic, or neurobehavioral deficits or neurologic death observed at 4 to 8 days postoperatively. This same measure was assessed secondarily at 6 weeks and 6 months. Length of hospital stay was also compared as a secondary assessment.

RESULTS

The 2 groups were well matched at baseline. The insulin-treated group had significantly lower blood glucose concentrations during bypass. Sixty-six percent of subjects in the insulin-treated group and 67% of subjects in the control group demonstrated a new or worsening neurologic, neuro-ophthalmologic, or neurobehavioral deficit or neurologic death at the 4- to 8-day assessment. Outcomes were also similar in the 2 groups at 6 weeks (37% and 39% incidence, respectively) and 6 months (30% and 25%, respectively). Median lengths of stay were 7 and 6 days, respectively, in the treatment and control groups. None of these outcome differences was statistically significant.

CONCLUSION

Attempted control of hyperglycemia during cardiopulmonary bypass had no significant effect on the combined incidence of neurologic, neuro-ophthalmologic, or neurobehavioral deficits or neurologic death and failed to shorten the length of hospital stay. These results do not contradict those of other studies showing that aggressive control of hyperglycemia in the postoperative period will improve outcome.

Intraoperative glucose control in diabetic and nondiabetic patients during cardiac surgery

OBJECTIVE

The purpose of this study was to evaluate intraoperative glucose control.

DESIGN

Prospective unblinded study.

SETTING

Tertiary care center.

PARTICIPANTS

Diabetic (n = 17) and nondiabetic (n = 23) patients undergoing elective cardiac surgery.

INTERVENTIONS

Diabetics received a modified insulin regimen consisting of a fixed rate infusion of regular insulin, 10 U/m2/h, and a variable infusion of D10W, adjusted to maintain glucose between 101 to 140 mg/dL.

MEASUREMENTS AND MAIN RESULTS

Baseline glucose was higher in diabetics versus nondiabetics (mean +/- standard error of the mean: 203 +/- 27 v 117 +/- 3 mg/dL, p < 0.005). After baseline, insulin levels were increased in diabetics to 410 to 568 microU/mL. Corresponding insulin levels in nondiabetics were 12 to 40 microU/mL. Compared with baseline, glucose was decreased by 10% +/- 29% in diabetics during hypothermic cardiopulmonary bypass and increased by 21% +/- 30% in nondiabetics (p < 0.005). After discontinuation of bypass, glucose was lower in diabetics (137 +/- 12 mg/dL) versus nondiabetics (162 +/- 8 mg/dL, p < 0.005). Nine diabetics had adequate intraoperative glycemic control during hypothermic bypass (glucose 123 +/- 8 mg/dL, insulin 550 +/- 68 microU/mL, glucose infusion rate 1.87 +/- 0.29 mg/kg/min), 6 approached adequate control near the end of surgery (glucose 147 +/- 8 mg/dL, insulin 483 +/- 86 microU/mL, glucose infusion rate 0.35 +/- 0.05 mg/kg/min), and 2 never achieved control. Diabetics with elevated initial glucose >300 mg/dL did not achieve adequate glycemic control. Four diabetics (3 with renal failure) required injection of 50% dextrose after bypass for hypoglycemia.

CONCLUSION

Adequate glycemic control can be achieved in most diabetics during cardiac surgery using a modified insulin clamp technique provided initial glucose is <300 mg/dL.

Maintenance of Normoglycemia During Cardiac Surgery

We used the hyperinsulinemic normoglycemic clamp technique, i.e., infusion of insulin at a constant rate combined with dextrose titrated to clamp blood glucose at a specific level, to preserve normoglycemia during elective cardiac surgery. Ten nondiabetic and seven diabetic patients entered the clamp protocols. Perioperative glucose control was also assessed in 19 nondiabetic and 11 diabetic patients (control group) receiving a conventional insulin infusion sliding scale. In patients of the clamp group, a priming bolus of insulin (2 U) was started before the induction of anesthesia followed by infusions of insulin at 5 mU. kg(-1). min(-1) and of variable amounts of dextrose. Arterial blood glucose was measured every 5 min in the clamp group and every 20 min in the control group. Control of normoglycemia was defined as > or =95% of the glucose levels within 4.0-6.0 mmol/L. Glucose concentration was recorded before surgery, 15 min before cardiopulmonary bypass (CPB), during early and late CPB, and at sternal closure. Patients of the control group became progressively hyperglycemic during surgery (late CPB; nondiabetics, 9.0 +/- 3.2 mmol/L; diabetics, 10.1 +/- 3.6 mmol/L), whereas normoglycemia was achieved in the study group (late CPB; nondiabetics, 5.5 +/- 0.7 mmol/L; diabetics, 4.9 +/- 0.6 mmol/L; P < 0.05 versus control group). In conclusion, it seems that normal blood glucose concentration during open heart surgery can be reliably maintained in nondiabetic and diabetic patients by using the hyperinsulinemic normoglycemic clamp technique.