Association of hypoglycemia and cardiac ischemia: a study based on continuous monitoring

Minimization and withdrawal of steroids in pancreas and islet transplantation

For reducing the corticosteroid (CS)-related side-effects, especially cardiovascular events, CS-sparing protocols have become increasingly common in pancreas transplantation (PT). Lympho-depleting induction antibodies, such as rabbit anti-thymocyte globulin (rATG) or alemtuzumab, have been widely used in successful trials. The results of various CS-sparing protocols combining calcineurin inhibitors (CNI) and mycophenolate or sirolimus, have been mixed for rejection and survival rates. Most of the studies were uncontrolled trials of low-risk patients, therefore the grade of evidence is limited. Large-scale prospective studies with long-term follow up are necessary to assess risks and benefits of CS-sparing regimens in PT before recommending such strategies as standard practice. Islet allo-transplantation for patients with brittle type 1 diabetes mellitus, less invasive and safer procedure than PT, has been attempted since late 1980s, but diabetogenic immunosuppressants at maintenance, mainly CS and high-dose CNI, prevented satisfactory results (10% insulin-independence at 1-year post-transplant). Since 2000, CS-free and CNI-reducing protocols, including more potent induction [daclizumab, OKT3gamma1(ala-ala) anti-CD3 antibody, rATG] and maintenance (sirolimus, mycophenolate) agents, have significantly improved short-term outcomes whereas long-term are still inadequate (from 80% to 20% insulin-independence from 1- to 5-year post-transplant). Main limitations are allo- and autoimmunity, immunosuppression-related islet and systemic toxicity and transplant site unsuitability, which tolerogenic protocols and biotechnological solutions may solve.

Is the combination of sulfonylureas and metformin associated with an increased risk of cardiovascular disease or all-cause mortality?: a meta-analysis of observational studies

OBJECTIVE

Observational studies assessing the association of combination therapy of metformin and sulfonylurea on all-cause and/or cardiovascular mortality in type 2 diabetes have shown conflicting results. We therefore evaluated the effects of combination therapy of sulfonylureas and metformin on the risk of all-cause mortality and cardiovascular disease (CVD) among people with type 2 diabetes.

RESEARCH DESIGN AND METHODS

A MEDLINE search (January 1966-July 2007) was conducted to identify observational studies that examined the association between combination therapy of sulfonylureas and metformin on risk of CVD or all-cause mortality. From 299 relevant reports, 9 were included in the meta-analysis. In these studies, combination therapy of metformin and sulfonylurea was assessed, the risk of CVD and/or mortality was reported, and adjusted relative risk (RR) or equivalent (hazard ratio and odds ratio) and corresponding variance or equivalent was reported.

RESULTS

The pooled RRs (95% CIs) of outcomes for individuals with type 2 diabetes prescribed combination therapy of sulfonylureas and metformin were 1.19 (0.88-1.62) for all-cause mortality, 1.29 (0.73-2.27) for CVD mortality, and 1.43 (1.10-1.85) for a composite end point of CVD hospitalizations or mortality (fatal or nonfatal events).

CONCLUSIONS

The combination therapy of metformin and sulfonylurea significantly increased the RR of the composite end point of cardiovascular hospitalization or mortality (fatal and nonfatal events) irrespective of the reference group (diet therapy, metformin monotherapy, or sulfonylurea monotherapy); however, there were no significant effects of this combination therapy on either CVD mortality or all-cause mortality alone.

Electrocardiographic alterations during hyperinsulinemic hypoglycemia in healthy subjects

BACKGROUND

We evaluated the arrhythmogenic potential of hypoglycemia by studying electrocardiographic (ECG) changes in response to hyperinsulinemic hypoglycemia and associated sympathoadrenal counterregulatory responses in healthy subjects.

METHODS

The study population consisted of 18 subjects, aged 30-40 years. Five-minute ECG recordings and blood samplings were performed at baseline and during the euglycemic and hypoglycemic hyperinsulinemic clamp studies. PR, QT, and QTc intervals of electrocardiogram and ECG morphology were assessed from signal-averaged ECG.

RESULTS

Although cardiac beat interval remained unchanged, PR interval decreased (P < 0.01) and QTc interval (P < 0.001) increased in response to hyperinsulinemic hypoglycemia. Concomitant morphological alterations consisted of slight increases in R-wave amplitude and area (P < 0.01 for both), significant decreases in T-wave amplitude and area (P < 0.001 for both), and moderate ST depression (P < 0.001). Counterregulatory norepinephrine response correlated with amplification of the R wave (r =-0.620, P < 0.05) and epinephrine response correlated with flattening of the T wave (r =-0.508, P < 0.05).

CONCLUSIONS

Hyperinsulinemic hypoglycemia with consequent sympathetic humoral activation is associated with several ECG alterations in atrioventricular conduction, ventricular depolarization, and ventricular repolarization. Such alterations in cardiac electrical function may be of importance in provoking severe arrhythmias and "dead-in-bed" syndrome in diabetic patients with unrecognized hypoglycemic episodes.

Vascular disease and diabetes: is hypoglycaemia an aggravating factor?

Acute hypoglycaemia provokes profound physiological changes affecting the cardiovascular system and several haematological parameters, principally as a consequence of sympatho-adrenal activation and counter-regulatory hormonal secretion. Many of these responses have an important role in protecting the brain from neuroglycopenia, through altering regional blood flow and promoting metabolic changes that will restore blood glucose to normal. In healthy young adults the cardiovascular effects are transient and have no obvious detrimental consequences. However, some of the effected changes are potentially pathophysiological and in people with diabetes who have developed endothelial dysfunction, they may have an adverse impact on a vasculature that is already damaged. The acute haemodynamic and haematological changes may increase the risk of localized tissue ischaemia, and major vascular events can certainly be precipitated by acute hypoglycaemia. These include myocardial and cerebral ischaemia and occasionally infarction. Established diabetic retinopathy often deteriorates after strict glycaemic control is instituted, the latter being associated with a threefold increase in frequency of severe hypoglycaemia, and enhanced exposure to mild hypoglycaemia. The possible mechanisms underlying these hypoglycaemia-induced effects include haemorrheological changes, white cell activation, vasoconstriction, and the release of inflammatory mediators and cytokines. The concept that acute hypoglycaemia could aggravate vascular complications associated with diabetes is discussed in relation to evolving comprehension of the pathogenesis of atherosclerosis and blood vessel disease.

Type 2 diabetes among women: clinical considerations for pharmacological management to achieve glycemic control and reduce cardiovascular risk

The purpose of this paper is to highlight specific considerations in the medical management of women with type 2 diabetes mellitus (T2DM). T2DM, a significant source of morbidity and mortality, has become an ever growing epidemic within the United States. Although it is well understood that diabetes can significantly increase the risk for microvascular and macrovascular complications, there has been limited research examining the differential impact of these complications on men and women. Women, in particular, are subject to especially high risk for the development of myocardial infarction (MI), claudication, and stroke and are disproportionately afflicted by cardiovascular, cerebrovascular, and peripheral vascular disease. There is new evidence that tight glycemic control and earlier initiation of insulin therapy can improve outcomes and thereby reduce the risk for development of both macrovascular and microvascular complications of the disease. Although there are many commonalities in the treatment of men and women, women with diabetes have several unique issues, including the possible effects of therapy on reproductive health, fetal health, breastfeeding, potential interactions with hormonal contraceptives, and effects on bone health, that should be considered when determining a therapeutic approach. This paper presents evidence-based treatment strategies for reducing the risk of diabetes-associated complications overall and cardiovascular disease in particular through glycemic control. Special attention is paid to the selection of antidiabetic agents that are best suited to the unique needs of women.

Why insulin sensitizers but not secretagogues should be retained when initiating insulin in type 2 diabetes

The stringent targets set for HbA(1c) levels in type 2 diabetes are currently achieved by fewer than half the patients in the United States. Failure to manage hyperglycaemia in the early stages of disease results in progressive loss of beta-cell function, which ultimately necessitates the initiation of insulin therapy. At this point, choices have to be made on whether to continue oral anti-diabetic drug therapy and, if so, with which agent(s). Historically, sulfonylureas have been the mainstay of oral anti-diabetic drug therapy; however, their long-term efficacy in patients with depleted beta-cell capacity is doubtful, and other classes of oral anti-diabetic drugs, notably the insulin sensitizers, may prove more reliable. These agents (metformin and thiazolidinediones) appear to provide various benefits over and above sustained glycaemic control, which may variably include reduced loss of beta-cell function as well as improvements to cardiovascular risk factors, morbidity, and mortality. Metformin also limits weight gain associated with insulin therapy. This manuscript presents the case that when insulin therapy is initiated it should be tailored to individual needs through combination with one or more insulin sensitizers rather than a secretagogue.

Plasma endothelin response to acute hypoglycaemia in adults with Type 1 diabetes

AIMS

To determine whether acute insulin-induced hypoglycaemia provokes a detectable alteration in peripheral plasma endothelin (ET) concentrations in humans with Type 1 diabetes.

METHODS

Serial plasma concentrations of ET were measured in 20 patients with Type 1 diabetes during controlled hypoglycaemia induced by intravenous infusion of soluble insulin.

RESULTS

A significant increase was observed in plasma ET concentrations, from 3.80 +/- 0.31 pg/ml at baseline to 6.72 +/- 1.47 pg/ml at 60 min after the onset of the hypoglycaemic reaction (P < 0.05).

CONCLUSIONS

Acute insulin-induced hypoglycaemia induces a rise in plasma endothelin concentrations in people with Type 1 diabetes. This finding is consistent with a putative role for ET in the mediation of hypoglycaemia-induced vasoconstriction, and the possible precipitation of macrovascular or microvascular events.

Current perioperative treatment of patients with type 1 and type 2 diabetes

Diabetes mellitus is rapidly increasing, diabetic patients are likely to undergo surgical procedures more than non-diabetic patients, the hospital stay of diabetic patients is longer, and diabetic patients have increased mortality and morbidity. The correct treatment of diabetic patients in the perioperative period is crucial to improve clinical outcomes. Diabetic patients must be carefully evaluated for cardiovascular risk, keeping in mind micro- and macroangiopathic diabetic complications. Metabolic control deserves great attention because hyperglycemia is related to increased complications and worse outcomes. Insulin infusion regimens to achieve near normoglycemia must be implemented in surgical and critically ill patients.

Comparative study on the effect of enteral feeding on blood glucose

Stress hyperglycaemia is common in intensive care patients. There is recent evidence to suggest that maintaining the blood glucose of a patient in intensive care between 4 mmol/litre and 6.1 mmol/litre reduces morbidity and mortality. The aim of this comparative study was to determine if blood glucose control improves with abolishing feeding breaks and introducing continuous enteral feeding. Twenty ventilated patients admitted to a combined medical and surgical intensive care unit were sampled. Ten patients received standard care (enteral feeding for 18 hours with an 8-hour break). The interventional group received continuous enteral feeding over the 24 hours. Analysis of the data revealed that continuous enteral feeding reduced blood glucose levels significantly, improved blood glucose control and reduced insulin requirements. Research should continue to determine if the results of this study could be replicated within a larger group of intensive care patients.

Efficacy of continuous glucose monitoring system (CGMS) to detect postprandial hyperglycemia and unrecognized hypoglycemia in type 1 diabetic patients

BACKGROUND

To evaluate the efficacy of continuous glucose monitoring system (CGMS) to detect postprandial hyperglycemia and unrecognized hypoglycemia in type 1 diabetes mellitus (DM1) patients.

METHODS

We studied 46 patients (43.4%M/56.6%F), average age of 25.9+/-12.8 years, submitted to 72 h CGMS. It were analyzed: capillary glycemia (CG) and CGMS sensor's value, glycemic excursions, postprandial hyperglycemia, asymptomatic hypoglycemia and therapeutic management after CGMS. Correlation coefficient during hypo and hyperglycemia and sensitivity/specificity were determined.

RESULTS

The mean capillary glucose values were 191.8+/-46.2mg/dl versus 190.9+/-42.1mg/dl by CGMS sensor, with no statistical difference by T-test (T=-0.6; p=0.79). The CGMS was significantly more efficient in detection of glycemic excursion than CG (p=0.001). The postprandial hyperglycemia was identified in 76.9% of diabetic patients and asymptomatic hypoglycemia was detected in 58.2% of these patients. The correlation coefficient presented no significance (p=0.16) during hypoglycemia versus during hyperglycemia (p=0.002). The CGMS sensor presented low sensitivity (79.1%) to detect hypoglycemia versus hyperglycemia (96.8%).

CONCLUSIONS

The CGMS showed to be a good method to identify postprandial hyperglycemia, to improve therapeutics management and confirmed the low sensitivity of CGMS to detect unrecognized hypoglycemia in DM1 patients.

Cyclic guanosine monophosphate phosphodiesterase-5 inhibitor promotes an endothelium NO-dependent-like vasodilation in patients with refractory hypertension

The nitric oxide/cyclic-guanosine 3',5'-monophosphate signaling cascade plays an essential role in cardiovascular homeostasis but its involvement in the pathophysiology of refractory hypertension is unclear. The acute vasodilatory effect of a single oral dose of a phosphodiesterase-5 inhibitor (sildenafil citrate) on the brachial artery dilatation was evaluated in 25 normal healthy volunteers (NL) and in 25 refractory hypertensive patients (RH). Endothelial and vascular smooth muscle functions were assessed two times. First, the brachial artery response to endothelium-dependent (flow-mediated dilatation [FMD]) and independent (glyceryl trinitrate [GTN]) stimuli was examined. The FMD in NL was 14.2+/-3.2% compared to 10.3+/-3.5% in RH (P<0.001) and the GTN-induced responses were 23.5+/-6.3 in NL compared to 18.4+/-5.7% in RH (P<0.001). Two weeks later, the brachial artery responses to FMD were determined before and after the administration of sildenafil citrate. Sildenafil caused a significant, slow and progressive dilatation of the brachial artery until 45 min after administration (4.7+/-3.0%, 6.7+/-3.0% and 9.4+/-3.9% after 15', 30' and 45', respectively, in RH and 3.7+/-1.9%, 7.4+/-2.7% and 10.1+/-3.0%, respectively, in NL). A second FMD stimulus, applied 45 min after ingesting 50mg of sildenafil resulted in an additional significant increase in the vasodilatory response (from 9.4+/-3.9% to 13.0+/-4.0% in RH; P<0.001 and from 10.1+/-3.0 to 14.6+/-4.1 in NL; P<0.001), but this was still significantly less than the response to GTN. Sildenafil citrate caused brachial artery vasodilatation similar to that caused by NO released during FMD in patients with refractory hypertension.

Perioperative glucose control in the diabetic or nondiabetic patient

Patients with diabetes are more likely to undergo surgery than nondiabetics, and maintaining glycemic control in subjects with diabetes can be challenging during the perioperative period. Surgery in diabetic patients is associated with longer hospital stay, higher health care resource utilization, and greater perioperative mortality. In addition, several observational and interventional studies have indicated that hyperglycemia is associated with adverse clinical outcomes in surgical and critically ill patients. This paper reviews the pathophysiology of hyperglycemia during trauma and surgical stress and will provide practical recommendations for the preoperative, intraoperative, and postoperative care of diabetic patients.

Newly Diagnosed Diabetes/Hyperglycemia in Hospitals: What Should We Do?

OBJECTIVE

To examine the clinical problem of newly diagnosed diabetes/hyperglycemia in hospitals, and to develop a management strategy.

METHODS

A review of the literature on outcomes and management of such patients.

RESULTS

There are very few published papers on this subject, the majority being in patients with cardiovascular disease. However, there is recognition that the problem is common. No randomized clinic trials have been carried out on therapeutic strategies in such patients. The limited data available suggest that patients with newly diagnosed diabetes and hyperglycemia tend to have a poor prognosis.

CONCLUSION

Newly diagnosed diabetes/hyperglycemia in hospital is a common problem and is associated with a poor prognosis. Therefore, it seems appropriate that such patients be managed the same way as patients with established diabetes. Following discharge, appropriate diagnostic testing is needed to establish the presence or absence of diabetes so that long-term treatment plans can be initiated.

Association between hyper- and hypoglycaemia and 2 year all-cause mortality risk in diabetic patients with acute coronary events

AIMS

The study evaluated the associations between glycometabolic parameters at admission and during hospitalization and 2 year all-cause mortality risk in an unselected cohort of consecutive patients with diabetes admitted for unstable angina or non-Q-wave myocardial infarction to a university hospital during 1988-98.

METHODS AND RESULTS

A total of 713 consecutive patients with diabetes were included. During 2 years of follow-up, 242 (34%) patients died. All analyses were retrospective using prospectively collected clinical data. The primary study endpoint was 2 year all-cause mortality collected from the Swedish cause-specific mortality register. In unadjusted analyses, high admission blood glucose (highest vs. lowest quartile: hazard ratio (HR) 2.66; 95% confidence interval (CI) 1.83, 3.86) and hypoglycaemia recorded during hospitalization (hypoglycaemia vs. normal: HR 1.77; 95% CI 1.09, 2.86) were both significantly associated with increased 2 year all-cause mortality risk. These associations remained significant after multivariable adjustment.

CONCLUSION

In the setting of acute coronary syndromes (ACS) among patients with diabetes, hyperglycaemia on arrival and hypoglycaemia during hospitalization are both independently associated with worse adjusted all-cause 2 year mortality risk. These observations suggest that the avoidance of both hyper- and hypoglycaemia during ACS events may be of similar importance, and glucose modulation remains an important objective to address in future randomized trials.

Role of insulin secretagogues and insulin sensitizing agents in the prevention of cardiovascular disease in patients who have diabetes

In the absence of clinical trial evidence to compare the secretagogues with sensitizers, it is difficult to make recommendations about which class of drug is more important to prescribe for the prevention of cardiovascular disease in diabetes mellitus. Epidemiologic data supports insulin resistance as a major factor in cardiovascular disease through a variety of mechanisms. Because sensitizers improve insulin sensitivity and correct many of the vascular abnormalities that are associated with insulin resistance, it is tempting to suggest that they may be superior for this purpose. Conversely, meeting the goals that are recommended for glycemia also are important and achieving them may not be always possible with sensitizers, particularly in the later stages of the disease when insulin levels are not high,despite insulin resistance. In such situations,combination therapy may be needed with both types of drugs. No data are available on the cardiovascular effects of such combinations;some retrospective data suggest a possibility of increased events with the combination of sulfonylureas and metformin. Thus, further prospective studies in this area are necessary.

The impact of antidiabetic therapies on cardiovascular disease

Cardiovascular disease disproportionately affects people with diabetes and is a leading cause of death. Glycemic control has so far not been conclusively shown to decrease cardiovascular events. The therapeutic agents used in treating glycemia have different effects on cardiovascular risks and, therefore, may have different effects on outcome. Insulin sensitizers impact cardiovascular risk factors, including dyslipidemia and fibrinolysis. Metformin is the only oral antidiabetic medication shown to decrease cardiovascular events independent of glycemic control. Thiazolidinediones improve insulin resistance and lower insulin concentrations, which is beneficial because hyperinsulinemia is an independent predictor of cardiovascular disease. Insulin therapy acutely reduces cardiovascular mortality and morbidity in patients with diabetes and known coronary artery disease and also in patients with hyperglycemia when critically ill, but the long-term effects are unclear. In contrast, insulin secretagogues have very little effect on both cardiovascular risk factors and outcomes.

Asymptomatic hypoglycaemia: identification and impact

The Diabetes Control and Complications Trial (DCCT) demonstrated that intensive management in people with type 1 diabetes delays the onset and the progression of microvascular complications associated with the disease. However, it is also known that intensive regimens can increase the number of hypoglycaemias and that the perception of symptoms decreases in relation to the statutes of metabolic control 1. Impairment of hypoglycaemic awareness is reported by up to 50% of patients with type 1 diabetes and it is associated with an increase of severe episodes of hypoglycaemia 2. Self-monitoring of blood glucose (SMBG) has become a major tool in the management of diabetes. Current recommendations suggest frequent SMBG. The major inconvenience of SMBG is due to the limitations of the glycaemic profile obtained from intermittent finger-sticks. This is an incomplete picture of blood glucose excursions; moreover, the frequent SMBG is not readily accepted by patients suffering from diabetes because it is invasive and painful.

A Comparison of Bedtime Insulin Glargine with Bedtime Neutral Protamine Hagedorn Insulin in Patients with Type 2 Diabetes: Subgroup Analysis of Patients Taking Once-Daily Insulin in a Multicenter, Randomized, Parallel Group Study

BACKGROUND

Basal insulin is frequently administered once daily. This subgroup analysis of a multicenter, randomized, parallel study compared insulin glargine (Lantus Aventis Pharmaceuticals, Bridgewater, NJ) with neutral protamine Hagedorn (NPH) insulin in patients with type 2 diabetes, evaluating only patients treated previously with once-daily NPH insulin.

METHODS

Patients received bedtime insulin glargine or NPH insulin, with preprandial regular insulin. One hundred patients (mean age, 57.9 years; mean glycohemoglobin, 8.4%; mean fasting blood glucose, 167 mg/dL) were treated for up to 28 weeks.

RESULTS

Patients treated with insulin glargine (n = 52) and NPH insulin (n = 48) achieved similar reductions from baseline in glycohemoglobin (-0.41% versus -0.46%) and fasting blood glucose (-22 mg/dL versus -22 mg/dL) at week 28. The proportion of patients reaching target fasting blood glucose (<120 mg/dL) at 28 weeks was 34.2% with insulin glargine and 24.4% with NPH insulin. Similar proportions of patients achieved glycohemoglobin less than 7% and less than 8% in both groups. Baseline and week-28 mean daily doses of insulin glargine (27.3 IU versus 36.4 IU) were similar to NPH insulin doses (25.5 IU versus 30.2 IU). However, significantly fewer patients reported one or more episodes of hypoglycemia with insulin glargine (46.2%) versus NPH insulin (60.4%; P < 0.05). Significantly fewer patients also reported one or more symptomatic episodes confirmed by blood glucose less than 50 mg/dL with insulin glargine (17.3%) versus NPH insulin (31.3%; P < 0.005).

CONCLUSION

Bedtime insulin glargine is as effective as bedtime NPH insulin in improving glycemic control, with significantly less hypoglycemia.

The role of sulphonylureas in the management of type 2 diabetes mellitus

The sulphonylureas act by triggering insulin release from the pancreatic beta cell. A specific site on the adenosine triphosphate (ATP)-sensitive potassium channels is occupied by sulphonylureas leading to closure of the potassium channels and subsequent opening of calcium channels. This results in exocytosis of insulin. The meglitinides are not sulphonylureas but also occupy the sulphonylurea receptor unit coupled to the ATP-sensitive potassium channel. Glibenclamide (glyburide), gliclazide, glipizide and glimepiride are the primary sulphonylureas in current clinical use for type 2 diabetes mellitus. Glibenclamide has a higher frequency of hypoglycaemia than the other agents. With long-term use, there is a progressive decrease in the effectiveness of sulphonylureas. This loss of effect is the result of a reduction in insulin-producing capacity by the pancreatic beta cell and is also seen with other antihyperglycaemic agents. The major adverse effect of sulphonylureas is hypoglycaemia. There is a theoretical concern that sulphonylureas may affect cardiac potassium channels resulting in a diminished response to ischaemia. There are now many choices for initial therapy of type 2 diabetes in addition to sulphonylureas. Metformin and thiazolidinediones affect insulin sensitivity by independent mechanisms. Disaccharidase inhibitors reduce rapid carbohydrate absorption. No single agent appears capable of achieving target glucose levels in the majority of patients with type 2 diabetes. Combinations of agents are successful in lowering glycosylated haemoglobin levels more than with a single agent. Sulphonylureas are particularly beneficial when combined with agents such as metformin that decrease insulin resistance. Sulphonylureas can also be given with a basal insulin injection to provide enhanced endogenous insulin secretion after meals. Sulphonylureas will continue to be used both primarily and as part of combined therapy for most patients with type 2 diabetes.