How does blood glucose control with insulin save lives in intensive care?

Early endocrine alterations reflect prolonged stress and relate to 1-year functional outcome in patients with severe brain injury

OBJECTIVE

Severe brain injury may increase the risk of developing acute and chronic hypopituitarism. Pituitary hormone alterations developed in the early recovery phase after brain injury may have implications for long-term functional recovery. The objective of the present study was to assess the pattern and prevalence of pituitary hormone alterations 3 months after a severe brain injury with relation to functional outcome at a 1-year follow-up.

DESIGN

Prospective study at a tertiary university referral centre.

METHODS

A total of 163 patients admitted to neurorehabilitation after severe traumatic brain injury (TBI, n=111) or non-TBI (n=52) were included. The main outcome measures were endocrine alterations 3.3 months (median) after the brain injury and their relationship to the functioning and ability of the patients at a 1-year follow-up, as measured by the Functional Independence Measure and the Glasgow Outcome Scale-Extended.

RESULTS

Three months after the injury, elevated stress hormones (i.e. 30 min stimulated cortisol, prolactin and/or IGF1) and/or suppressed gonadal or thyroid hormones were recorded in 68 and 32% of the patients respectively. At 1 year after the injury, lower functioning level (Functional Independence Measure) and lower capability of performing normal life activities (Glasgow Outcome Scale-Extended) were related to both the elevated stress hormones (P≤0.01) and the reduced gonadal and/or thyroid hormones (P≤0.01) measured at 3 months.

CONCLUSION

The present study suggests that brain injury-related endocrine alterations that mimic secondary hypogonadism and hypothyroidism and that occur with elevated stress hormones most probably reflect a prolonged stress response 2-5 months after severe brain injury, rather than pituitary insufficiency per se. These endocrine alterations thus seem to reflect a more severe disease state and relate to 1-year functional outcome.

Perioperative glucose control in neurosurgical patients

Many neurosurgery patients may have unrecognized diabetes or may develop stress-related hyperglycemia in the perioperative period. Diabetes patients have a higher perioperative risk of complications and have longer hospital stays than individuals without diabetes. Maintenance of euglycemia using intensive insulin therapy (IIT) continues to be investigated as a therapeutic tool to decrease morbidity and mortality associated with derangements in glucose metabolism due to surgery. Suboptimal perioperative glucose control may contribute to increased morbidity, mortality, and aggravate concomitant illnesses. The challenge is to minimize the effects of metabolic derangements on surgical outcomes, reduce blood glucose excursions, and prevent hypoglycemia. Differences in cerebral versus systemic glucose metabolism, time course of cerebral response to injury, and heterogeneity of pathophysiology in the neurosurgical patient populations are important to consider in evaluating the risks and benefits of IIT. While extremes of glucose levels are to be avoided, there are little data to support an optimal blood glucose level or recommend a specific use of IIT for euglycemia maintenance in the perioperative management of neurosurgical patients. Individualized treatment should be based on the local level of blood glucose control, outpatient treatment regimen, presence of complications, nature of the surgical procedure, and type of anesthesia administered.

Glycemic control in critically ill patients

Hyperglycemia is common in critically ill patients and can be caused by various mechanisms, including nutrition, medications, and insufficient insulin. In the past, hyperglycemia was thought to be an adaptive response to stress, but hyperglycemia is no longer considered a benign condition in patients with critical illnesses. Indeed, hyperglycemia can increase morbidity and mortality in critically ill patients. Correction of hyperglycemia may improve clinical outcomes. To date, a definite answer with regard to glucose management in general intensive care unit patients, including treatment thresholds and glucose target is undetermined. Meta-analyses of randomized controlled trials suggested no survival benefit of tight glycemic control and a significantly increased incidence of hypoglycemia. Studies have shown a J- or U-shaped relationship between average glucose values and mortality; maintaining glucose levels between 100 and 150 mg/dL was likely to be associated with the lowest mortality rates. Recent studies have shown glycemic control < 180 mg/dL is not inferior to near-normal glycemia in critically ill patients and is clearly safer. Glycemic variability is also an important aspect of glucose management in the critically ill patients. Higher glycemic variability may increase the mortality rate, even in patients with the same mean glucose level. Decreasing glucose variability is an important issue for glycemic control in critically ill patients. Continuous measurements with automatic closed-loop systems could be considered to ensure that blood glucose levels are controlled within a specific range and with minimal variability.

Insulin-dependent phosphatidylinositol 3-kinase/Akt and ERK signaling pathways inhibit TLR3-mediated human bronchial epithelial cell apoptosis

TLR3, one of the TLRs involved in the recognition of infectious pathogens for innate and adaptive immunity, primarily recognizes viral-associated dsRNA. Recognition of dsRNA byproducts released from apoptotic and necrotic cells is a recently proposed mechanism for the amplification of toxicity, suggesting a pivotal participation of TLR3 in viral infection, as well as in lung diseases where apoptosis plays a critical role, such as asthma and chronic obstructive pulmonary disease. In addition to metabolic control, insulin signaling was postulated to be protective by inhibiting apoptosis. Therefore, we explored the role of insulin signaling in protecting against TLR3-mediated apoptosis of human bronchial epithelial cells. Significant TLR3-mediated apoptosis was induced by polyinosinic-polycytidylic acid, a dsRNA analog, via caspase-8-dependent mechanisms. However, insulin efficiently inhibited TLR3/polyinosinic-polycytidylic acid-induced human bronchial epithelial cell apoptosis via PI3K/Akt and ERK pathways, at least in part, via upregulation of cellular FLIPs and through protein synthesis-independent mechanisms. These results indicate the significance of TLR3-mediated dsRNA-induced apoptosis in the pathogenesis of apoptosis-driven lung disease and provide evidence for a novel protective role of insulin.

Antidiabetic Potentiality of the Aqueous-Methanolic Extract of Seed of Swietenia mahagoni (L.) Jacq. in Streptozotocin-Induced Diabetic Male Albino Rat: A Correlative and Evidence-Based Approach with Antioxidative and Antihyperlipidemic Activities

Antidiabetic, antioxidative, and antihyperlipidemic activities of aqueous-methanolic (2 : 3) extract of Swietenia mahagoni (L.) Jacq. (family Meliaceae) seed studied in streptozotocin-induced diabetic rats. Feeding with seed extract (25 mg 0.25 mL distilled water(-1)100 gm b.w.(-1)rat(-1) day(-1)) for 21 days to diabetic rat lowered the blood glucose level as well as the glycogen level in liver. Moreover, activities of antioxidant enzymes like catalase, peroxidase, and levels of the products of free radicals like conjugated diene and thiobarbituric acid reactive substances in liver, kidney, and skeletal muscles were corrected towards the control after this extract treatment in this model. Furthermore, the seed extract corrected the levels of serum urea, uric acid, creatinine, cholesterol, triglyceride, and lipoproteins towards the control level in this experimental diabetic model. The results indicated the potentiality of the extract of S. mahagoni seed for the correction of diabetes and its related complications like oxidative stress and hyperlipidemia. The extract may be a good candidate for developing a safety, tolerable, and promising neutraceutical treatment for the management of diabetes.

Glycaemic control in acute coronary syndromes: prognostic value and therapeutic options

Type 2 diabetes and acute coronary syndromes (ACS) are widely interconnected. Individuals with type 2 diabetes are more likely than non-diabetic subjects to experience silent or manifest episodes of myocardial ischaemia as the first presentation of coronary artery disease. Insulin resistance, inflammation, microvascular disease, and a tendency to thrombosis are common in these patients. Intensive blood glucose control with intravenous insulin infusion has been demonstrated to significantly reduce morbidity and mortality in critically ill hyperglycaemic patients admitted to an intensive care unit (ICU). Direct glucose toxicity likely plays a crucial role in explaining the clinical benefits of intensive insulin therapy in such critical patients. However, the difficult implementation of nurse-driven protocols for insulin infusion able to lead to rapid and effective blood glucose control without significant episodes of hypoglycaemia has led to poor implementations of insulin infusion protocols in coronary care units, and cardiologists now to consider alternative drugs for this purpose. New intravenous or oral agents include the incretin glucagon-like peptide 1 (GLP1), its analogues, and dipeptidyl peptidase-4 inhibitors, which potentiate the activity of GLP1 and thus enhance glucose-dependent insulin secretion. Improved glycaemic control with protective effects on myocardial and vascular tissues, with lesser side effects and a better therapeutic compliance, may represent an important therapeutic potential for this class of drugs in acutely ill patients in general and patients with ACS in particular. Such drugs should be known by practicing cardiologists for their possible use in ICUs in the years to come.

Insulin activation of the phosphatidylinositol 3-kinase/protein kinase B (Akt) pathway reduces lipopolysaccharide-induced inflammation in mice

Insulin is used to control pro-inflammatory hyperglycemia in critically ill patients. However, recent studies suggest that insulin-induced hypoglycemia may negate its beneficial effects in these patients. It is noteworthy that recent evidence indicates that insulin has anti-inflammatory effects that are independent of controlling hyperglycemia. To date, the mechanism by which insulin directly reduces inflammation has not been elucidated. It is well established that insulin activates phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) signaling in many cell types. We and others have shown that this pathway negatively regulates LPS-induced signaling and pro-inflammatory cytokine production in monocytic cells. We hypothesized that insulin inhibits inflammation during endotoxemia by activation of the PI3K/Akt pathway. We used a nonhyperglycemic mouse model of endotoxemia to determine the effect of continuous administration of a low dose of human insulin on inflammation and survival. It is noteworthy that insulin treatment induced phosphorylation of Akt in muscle and adipose tissues but did not exacerbate lipopolysaccharide (LPS)-induced hypoglycemia. Insulin decreased plasma levels of interleukin-6, tumor necrosis factor-alpha, monocyte chemotactic protein 1 (MCP1)/JE, and keratinocyte chemoattractant, and decreased mortality. The PI3K inhibitor wortmannin abolished the insulin-mediated activation of Akt and the reduction of chemokine and interleukin-6 levels. We conclude that insulin reduces LPS-induced inflammation in mice in a PI3K/Akt-dependent manner without affecting blood glucose levels.

Blood glucose control in critical care patients - a review of the literature

The role of hyperglycaemia in critical illness, and its corresponding treatment, has been an area of controversy, fuelled by conflicting research findings. The aims of this study were to critically evaluate the literature and present an historical review of the sequence of published papers relating to blood glucose control in critical care. Their subsequent impact together with the implications for patient care is discussed. This article is based on a systematic review of papers relating to glycaemic control in critical care patients. The review was conducted using the MedLine, CINAHL and EMBASE databases using key search terms (details of the search terms can be found after the conclusion of the paper) for the period 1950-2006. The searches resulted in 4863 papers being screened for relevance to the historic progression of glycaemic management in critical care patients, by title and then abstract. Of these, 209 were accessed, and their reference lists were snowballed for further papers. Papers that were repeatedly quoted throughout the literature and were therefore considered important in the historical development of accepted critical care practice were finally subjected to rigorous appraisal. These totalled 91 papers and included 18 randomized controlled trials, an additional 28 research papers, 25 editorials and 20 reviews. This critical evaluation of published work indicates that the evidence for the benefit of this therapy may not be as compelling as previously indicated, and its widespread use may have been premature. From a nursing perspective, this demonstrates the importance of maintaining a questioning attitude to new therapies and reviewing best practice in the light of evolving evidence.

Transforming the surgical "time-out" into a comprehensive "preparatory pause"

We propose expansion of the standard "time-out" into a comprehensive "preparatory pause" encompassing five well-documented perioperative risk avoidance strategies: beta-adrenergic blockade, DVT prophylaxis, preoperative antibiotics, normothermia, and euglycemia. Although all members of the surgical team acknowledge the clear benefit of these five prophylactic strategies, published national compliance even in the target patient population is a disappointingly consistent 50%. We have developed and field-tested a "preparatory pause" form that we appended to our "surgical time-out." By politely challenging our surgical team as to the inclusion of these five risk avoidance strategies in 167 consecutive patients, we increased our compliance to more than 90% for each preventive measure. We have not attempted to quantify the physical and psychological benefit of complication avoidance due to the enhanced activation of these five prophylactic strategies. Using published surgical complication prevalence data, with and without these accepted risk avoidance measures, we estimate the number of complications per 100 patients avoided. Utilizing the Medicare payment schedule for each complication, we approximate the purely financial benefit of the "preparatory pause" to be $88,640 per 100 patients, or almost $900 per patient. The now standard surgical "time-out" is designed to avoid the gratifyingly uncommon problem of "wrong patient,""wrong procedure," and "wrong site." Many surgeons negotiate an entire career without stumbling over these disastrous problems. We propose expansion of the "time-out" to include five well-documented perioperative risk avoidance strategies that many of us overlook all too often.

Glycemic control and critical illness: is the kidney involved?

The pathophysiology, consequences, and management of hyperglycemia during critical illness is an important clinical issue. Uncontrolled hyperglycemia in this setting is associated with a variety of adverse events, including mortality. The kidneys have a major role in glucose and insulin metabolism, and emerging evidence suggests that they both are actively involved in the development, maintenance, and resolution of hyperglycemia. The development of acute kidney injury is also a risk in this setting. This article discusses potential approaches for efficient and effective management of hyperglycemia.

Women with polycystic ovary syndrome are sensitive to the TNF-alpha-lowering effect of glucose-induced hyperinsulinaemia

BACKGROUND

Restoration of near-euglycaemia by intensive insulin therapy results in decreased serum levels of inflammatory mediators. The authors investigated whether the anti-inflammatory effect of insulin was independent of its glucose-lowering action and if this effect was intact in insulin-resistant women with the polycystic ovary syndrome (PCOS) characterized by low-grade chronic inflammation.

MATERIALS AND METHODS

Blood was drawn on the third and sixth days after progestin-induced withdrawal bleeding in 20 young non-diabetic women with PCOS and once between the third and sixth days of the menstrual cycle in 21 age-matched lean healthy control women during a 75-g oral glucose tolerance test (oGTT). Serum insulin, glucose and tumour necrosis factor alpha (TNF-alpha) concentrations were measured after 0, 30, 60, 90 and 120 min.

RESULTS

The increase in insulin and glucose concentrations during the oGTT was significantly more pronounced in patients with PCOS (one patient with impaired fasting glucose, one patient with impaired glucose tolerance, three patients with both) compared with healthy controls. The TNF-alpha serum concentrations decreased in patients with PCOS (mean of both days, P = 0.004). In patients and in controls, there was an inverse correlation between the serum concentrations of insulin and of TNF-alpha during oGTT (for patients, a mean of both days, P = 0.009; for controls, P = 0.047), but not between the serum concentrations of glucose and TNF-alpha.

CONCLUSIONS

The decrease in TNF-alpha concentrations during oGTT and the inverse correlation between endogenous hyperinsulinaemia and serum TNF-alpha concentrations suggested an anti-inflammatory effect of moderately-high insulin concentrations. This occurred despite the presence of moderate hyperglycaemia. These findings also demonstrated a preserved responsiveness of inflammatory mediators to insulin in PCOS.

Impact of intensive insulin therapy on neuromuscular complications and ventilator dependency in the medical intensive care unit

RATIONALE

Critical illness polyneuropathy/myopathy causes limb and respiratory muscle weakness, prolongs mechanical ventilation, and extends hospitalization of intensive care patients. Besides controlling risk factors, no specific prevention or treatment exists. Recently, intensive insulin therapy prevented critical illness polyneuropathy in a surgical intensive care unit.

OBJECTIVES

To investigate the impact of intensive insulin therapy on polyneuropathy/myopathy and treatment with prolonged mechanical ventilation in medical patients in the intensive care unit for at least 7 days.

METHODS

This was a prospectively planned subanalysis of a randomized controlled trial evaluating the effect of intensive insulin versus conventional therapy on morbidity and mortality in critically ill medical patients. All patients who were still in intensive care on Day 7 were screened weekly by electroneuromyography. The effect of intensive insulin therapy on critical illness polyneuropathy/myopathy and the relationship with duration of mechanical ventilation were assessed.

MEASUREMENTS AND MAIN RESULTS

Independent of risk factors, intensive insulin therapy reduced incidence of critical illness polyneuropathy/myopathy (107/212 [50.5%] to 81/208 [38.9%], p = 0.02). Treatment with prolonged (> or = 14 d) mechanical ventilation was reduced from 99 of 212 (46.7%) to 72 of 208 (34.6%) (p = 0.01). This was statistically only partially explained by prevention of critical illness polyneuropathy/myopathy.

CONCLUSION

In a subset of medical patients in the intensive care unit for at least 7 days, enrolled in a randomized controlled trial of intensive insulin therapy, those assigned to intensive insulin therapy had a reduced incidence of critical illness polyneuropathy/myopathy and were treated with prolonged mechanical ventilation less frequently.

Risks and benefits of nutritional support during critical illness

Critically ill patients who depend on intensive care for more than a few days reveal profound erosion of lean body mass, which is thought to contribute to high morbidity and mortality. Despite a shortfall of evidence that supplemental feeding actually alters clinical outcome of these life-threatening disease states, this observation evoked an almost universal, albeit often inappropriate, use of nutritional support (NS) in the critically ill, administered via the parenteral or the enteral route. Lack of knowledge and overenthusiasm subsequently resulted in complications associated with both parenteral nutrition (PN) and enteral nutrition (EN), which led to the standing controversy over which should be preferred. With time, however, it became clear that EN and PN are not mutually exclusive and that critically ill patients requiring NS should be fed according to the functional status of the gastrointestinal tract. In addition, tight blood glucose control with insulin is advised in fed critically ill patients because overall metabolic control appears to surpass any outcome benefit attributed to the route of feeding. Recently, various special nutritional formulas have been suggested to prevent or treat multiorgan failure in the critically ill, among other pathways via modulation of immune function. Although special nutritional formulas may be promising in a variety of clinical settings, based on currently available data, these cannot be recommended for routine use in critically ill patients.

Intravenous glucose intake independently related to intensive care unit and hospital mortality: an argument for glucose toxicity in critically ill patients

OBJECTIVE

It is assumed that the toxic effects of glucose play a role in the outcome of critically ill patients. We studied the impact of the amount of infused glucose as a determinant of mortality.

DESIGN

A retrospective cohort study design was used as blood glucose levels in critically ill patients are nowadays tightly controlled.

PATIENTS

Long-stay critically ill patients (7-30 days).

MEASUREMENTS

The association between the mean amount of glucose infusion and both intensive care unit (ICU) and hospital mortality was determined. We corrected for the mean glucose serum concentration, the mean dosage of insulin and for severity of illness, using the acute physiology and chronic health evaluation (APACHE II) score.

RESULTS

Of the 2,042 admitted patients, 273 met the inclusion criteria. The mean length of stay was 14.4 days [interquartile range (IQR) 9-18]. Hospital mortality was significantly lower for patients with a mean glucose level below 8 mmol/l (30/79; 38%) compared to patients with a level above 8 mmol/l (104/194; 54%, P=0.023). Logistic stepwise multivariate regression analysis for both ICU and hospital mortality as dependent variables showed that APACHE II score and the mean daily amount of infused glucose were associated with mortality.

CONCLUSION

In long-stay ICU patients without blood glucose level control, the ICU and hospital mortality was independently related to the mean amount of infused glucose. In addition, mortality in patients with a mean glucose level above 8.0 mmol/l was higher. Both these determinants of mortality can exert their effects by insulin-independent uptake of glucose with subsequent toxic intracellular effects.

How obesity causes diabetes: not a tall tale

The epidemic of obesity-associated diabetes is a major crisis in modern societies, in which food is plentiful and exercise is optional. The biological basis of this problem has been explored from evolutionary and mechanistic perspectives. Evolutionary theories, focusing on the potential survival advantages of "thrifty" genes that are now maladaptive, are of great interest but are inherently speculative and difficult to prove. Mechanistic studies have revealed numerous fat-derived molecules and a link to inflammation that, together, are hypothesized to underlie the obesity-diabetes connection and thereby represent prospective targets for therapeutic intervention.