Extent and magnitude of catecholamine surge in pediatric burned patients

FIVE-YEAR OUTCOMES AFTER LONG-TERM OXANDROLONE ADMINISTRATION IN SEVERELY BURNED CHILDREN: A RANDOMIZED CLINICAL TRIAL

Administration of oxandrolone, a nonaromatizable testosterone analog, to children for 12 months following severe burn injury has been shown to improve height, increase bone mineral content (BMC), reduce cardiac work, and augment muscle strength. Surprisingly, the increase in BMC persists well beyond the period of oxandrolone administration. This study was undertaken to determine if administration of oxandrolone for 2 years yields greater effects on long-term BMC and bone mineral density (BMD). Patients between 0 and 18 years of age with ≥30% of total body surface area burned were consented to an IRB-approved protocol and randomized to receive either placebo (n = 84) or 0.1 mg/kg oxandrolone orally twice daily for 24 months (n = 35). Patients were followed prospectively from the time of admission until 5 years postburn in a single-center, intent-to-treat setting. Height, weight, BMC, and BMD were recorded annually through 5 years postinjury. The long-term administration of oxandrolone for 16 ± 1 months postburn (range, 12.1-25.2 months) significantly increased whole-body (WB) BMC (p < 0.02) and lumbar spine (LS) BMC (p < 0.05); these effects were significantly pronounced for a longer time in patients who were in growth spurt years (7-18 years). When adjusted for height, sex, and age, LS BMD was found to significantly increase with long-term oxandrolone administration (p < 0.0009). Fewer patients receiving oxandrolone exhibited LS BMD z scores below -2.0 as compared with controls, indicating a significantly reduced risk for future fracture with oxandrolone administration. Long-term oxandrolone patients had significantly greater height velocity than controls throughout the first 2-year postburn (p < 0.05). No adverse side effects were attributed to the long-term administration of oxandrolone. A comparison of the current patients receiving long-term oxandrolone to previously described patients receiving 12 months of oxandrolone revealed that long-term oxandrolone administration imparted significantly greater increases in WB-BMC, WB-BMD, and LS-BMD (p < 0.05). In conclusion, the administration of oxandrolone for up to 24 months to severely burned pediatric patients significantly improves WB BMC, LS BMC, LS BMD, and height velocity. The administration of long-term oxandrolone was more efficacious than administration for 12 months. Additionally, fewer patients in the oxandrolone cohort met the diagnostic criteria for pediatric osteoporosis, pointing to a reduced risk for future bone fracture. This study demonstrates that administering oxandrolone for up to 2 years following severe burn injury results in greater improvements in BMC, BMD, and height velocity.

White Adipose Tissue Browning: A Double-edged Sword

The study of white adipose tissue (WAT) 'browning' has become a 'hot topic' in various acute and chronic metabolic conditions, based on the idea that WAT browning might be able to facilitate weight loss and improve metabolic health. However, this view cannot be translated into all areas of medicine. Recent studies identified effects of browning associated with adverse outcomes, and as more studies are being conducted, a very different picture has emerged about WAT browning and its detrimental effect in acute and chronic hypermetabolic conditions. Therefore, the notion that browning is supposedly beneficial may be inadequate. In this review we analyze how and why browning in chronic hypermetabolic associated diseases can be detrimental and lead to adverse outcomes.

Evaluation of circulating haematopoietic progenitor cells in patients with Trauma Haemorrhagic shock and its correlation with outcomes

Background:

Haemorrhagic shock accounts up to 50% of early trauma deaths. Hematopoietic failure has been observed in experimental animals and human following shock and injury. One of the facets of bone marrow failure is multiple organ dysfunction syndrome and is commonly seen in patients recovering from severe trauma and hemorrhagic shock. Bone Marrow (BM) dysfunction is associated with mobilization of hematopoietic progenitor cells (HPCs) into peripheral blood. Present study explored the association of peripheral blood hematopoietic progenitor cells (HPCs) with mortality in trauma haemorrhagic shock patients (T/HS).

Materials and Methods:

Prospective cohort studies of patients presenting within 8 hrs of injury with T/HS to the Department of Emergency Medicine, Jai Prakash Narayan Apex Trauma Center, All India Institute of Medical Sciences were recruited. Peripheral blood samples were collected in each patient for measurement of peripheral blood HPCs. Peripheral blood progenitor cell (PBPC) quantification was performed by measuring HPCs counts using the haematology analyzer (Sysmex XE-2100). Clinical and laboratory data were prospectively collected after consent. Ethical approval was taken and data was analysed by Stata 11.2.

Results:

39 patients with trauma hemorrhagic shock and 30 normal healthy controls were recruited. HPCs were significantly higher (P < 0.001) in the T/HS as compared to control. Among study group, 14 patients died within 24 h. at the hospital admission, and found HPCs concentrations were highly significant (<0.001) in non-survivors (n = 14) when compared with survivors (n = 25) among T/HS patients.

Conclusions:

Our studies suggest the peripheral blood HPCs may be early prognostic marker for mortality among patients who presented with trauma hemorrhagic shock on admission. But the exact molecular mechanism and signalling pathway involved in the change of the behaviour of bone marrow microenvironment is still unclear.

Severe Burn Injury Induces Thermogenically Functional Mitochondria in Murine White Adipose Tissue

Chronic cold exposure induces functionally thermogenic mitochondria in the inguinal white adipose tissue (iWAT) of mice. Whether this response occurs in pathophysiological states remains unclear. The purpose of this study was to determine the impact of severe burn trauma on iWAT mitochondrial function in mice. Male BALB/c mice (10-12 weeks) received full-thickness scald burns to ∼30% of the body surface area. Inguinal white adipose tissue was harvested from mice at 1, 4, 10, 20, and 40 days postinjury. Total and uncoupling protein 1 (UCP1)-dependent mitochondrial thermogenesis were determined in iWAT. Citrate synthase activity was determined as a proxy of mitochondrial abundance. Immunohistochemistry was performed to assess iWAT morphology and UCP1 expression. Uncoupling protein 1-dependent respiration was significantly greater at 4 and 10 days after burn compared with sham, peaking at 20 days after burn (P < 0.001). Citrate synthase activity was threefold greater at 4, 10, 20, and 40 days after burn versus sham (P < 0.05). Per mitochondrion, UCP1 function increased after burn trauma (P < 0.05). After burn trauma, iWAT exhibited numerous multilocular lipid droplets that stained positive for UCP1. The current findings demonstrate the induction of thermogenically competent mitochondria within rodent iWAT in a model of severe burn trauma. These data identify a specific pathology that induces the browning of white adipose tissue in vivo and may offer a mechanistic explanation for the chronic hypermetabolism observed in burn victims.

Effectiveness of medical hypnosis for pain reduction and faster wound healing in pediatric acute burn injury: study protocol for a randomized controlled trial

BACKGROUND

Burns and the associated wound care procedures can be extremely painful and anxiety-provoking for children. Burn injured children and adolescents are therefore at greater risk of experiencing a range of psychological reactions, in particular posttraumatic stress disorder, which can persist for months to years after the injury. Non-pharmacological intervention is critical for comprehensive pain and anxiety management and is used alongside pharmacological analgesia and anxiolysis. However, effective non-pharmacological pain and anxiety management during pediatric burn procedures is an area still needing improvement. Medical hypnosis has received support as a technique for effectively decreasing pain and anxiety levels in adults undergoing burn wound care and in children during a variety of painful medical procedures (e.g., bone marrow aspirations, lumbar punctures, voiding cystourethrograms, and post-surgical pain). Pain reduction during burn wound care procedures is linked with improved wound healing rates. To date, no randomized controlled trials have investigated the use of medical hypnosis in pediatric burn populations. Therefore this study aims to determine if medical hypnosis decreases pain, anxiety, and biological stress markers during wound care procedures; improves wound healing times; and decreases rates of traumatic stress reactions in pediatric burn patients.

METHODS/DESIGN

This is a single-center, superiority, parallel-group, prospective randomized controlled trial. Children (4 to 16 years, inclusive) with acute burn injuries presenting for their first dressing application or change are randomly assigned to either the (1) intervention group (medical hypnosis) or (2) control group (standard care). A minimum of 33 participants are recruited for each treatment group. Repeated measures of pain, anxiety, stress, and wound healing are taken at every dressing change until ≥95 % wound re-epithelialization. Further data collection assesses impact on posttraumatic stress symptomatology, speed of wound healing, and parent perception of how easy the dressing change is for their child.

DISCUSSION

Study results will elucidate whether the disease process can be changed by using medical hypnosis with children to decrease pain, anxiety, and stress in the context of acute burn wounds.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry ACTRN12615000419561.

The efficacy and safety of adrenergic blockade after burn injury: A systematic review and meta-analysis

BACKGROUND

The hypermetabolic state after severe burns is a major problem that can lead to several pathophysiologic changes and produce multiple sequelae. Adrenergic blockade has been widely used to reverse these changes and improve outcomes in burned patients but has not been rigorously evaluated. The aim of this systematic review was to investigate the efficacy and safety of the use of adrenergic blockade after burn injury.

METHODS

The databases MEDLINE via OVID, PubMed, EMBASE, CINAHL, Cochrane Library, and Web of Science were searched from inception to December 2014 with search terms including burns and beta-blockers with appropriate synonyms. Articles were restricted to those published in English, French, or Spanish. Randomized controlled trials, nonrandomized controlled trials, and systematic reviews were screened. After an independent screening and full-text review, 10 articles were selected, and an appraisal of risk of bias was performed.

RESULTS

From 182 articles screened, 9 randomized controlled trials and 1 nonrandomized controlled trial met the inclusion criteria. Pooled analyses were performed to calculate effect sizes and 95% confidence intervals (CIs). There was a positive effect favoring propranolol use that significantly decreased resting energy expenditure (g = -0.64; 95% CI, -0.8 to -0.5; p < 0.001) and trunk fat (g = -0.3; 95% CI, -0.4 to -0.1; p < 0.001) as well as improved peripheral lean mass (g = 0.45; 95% CI, 0.3-0.6; p < 0.001) and insulin resistance (g = -1.35; 95% CI, -2.0 to -0.6; p < 0.001). Occurrence of adverse events was not significantly different between the treated patients the and controls.

CONCLUSION

Limited evidence suggests beneficial effects of propranolol after burn injury, and its use seems safe. However, further trials on adult population with a broader range of outcome measures are warranted.

LEVEL OF EVIDENCE

Systematic review and meta-analysis, level III.

Cardiovascular Dysfunction Following Burn Injury: What We Have Learned from Rat and Mouse Models

Severe burn profoundly affects organs both proximal and distal to the actual burn site. Cardiovascular dysfunction is a well-documented phenomenon that increases morbidity and mortality following a massive thermal trauma. Beginning immediately post-burn, during the ebb phase, cardiac function is severely depressed. By 48 h post-injury, cardiac function rebounds and the post-burn myocardium becomes tachycardic and hyperinflammatory. While current clinical trials are investigating a variety of drugs targeted at reducing aspects of the post-burn hypermetabolic response such as heart rate and cardiac work, there is still a paucity of knowledge regarding the underlying mechanisms that induce cardiac dysfunction in the severely burned. There are many animal models of burn injury, from rodents, to sheep or swine, but the majority of burn related cardiovascular investigations have occurred in rat and mouse models. This literature review consolidates the data supporting the prevalent role that β-adrenergic receptors play in mediating post-burn cardiac dysfunction and the idea that pharmacological modulation of this receptor family is a viable therapeutic target for resolving burn-induced cardiac deficits.

Predictors of muscle protein synthesis after severe pediatric burns

BACKGROUND

Following a major burn, skeletal muscle protein synthesis rate increases but is often insufficient to compensate for massively elevated muscle protein breakdown rates. Given the long-term nature of the pathophysiologic response to burn injury, we hypothesized that muscle protein synthesis rate would be chronically elevated in severely burned children. The objectives of this study were to characterize muscle protein synthesis rate of burned children over a period of 24 months after injury and to identify predictors that influence this response.

METHODS

A total of 87 children with 40% or greater total body surface area (TBSA) burned were included. Patients participated in stable isotope infusion studies at 1, 2, and approximately 4 weeks after burn and at 6, 12, and 24 months after injury to determine skeletal muscle protein fractional synthesis rate. Generalized estimating equations with log link normal distribution were applied to account for clustering of patients and control for patient characteristics.

RESULTS

Patients (8 ± 6 years) had large (62, 51-72% TBSA) and deep (47% ± 21% TBSA third degree) burns. Muscle protein fractional synthesis rate was elevated throughout the first 12 months after burn compared with established values from healthy young adults. Muscle protein fractional synthesis rate was lower in boys, in children older than 3 years, and when burns were greater than 80% TBSA.

CONCLUSION

Muscle protein synthesis is elevated for at least 1 year after injury, suggesting that greater muscle protein turnover is a component of the long-term pathophysiologic response to burn trauma. Muscle protein synthesis is highly affected by sex, age, and burn size in severely burned children. These findings may explain the divergence in net protein balance and lean body mass in different populations of burn patients.

LEVEL OF EVIDENCE

Prognostic study, level III.

Neuroendocrine regulation of inflammation

The interaction between the sympathetic nervous system and the immune system has been documented over the last several decades. In this review, the neuroanatomical, cellular, and molecular evidence for neuroimmune regulation in the maintenance of immune homeostasis will be discussed, as well as the potential impact of neuroimmune dysregulation in health and disease.

Mild cold-stress depresses immune responses: Implications for cancer models involving laboratory mice

Physiologically accurate mouse models of cancer are critical in the pre-clinical development of novel cancer therapies. However, current standardized animal-housing temperatures elicit chronic cold-associated stress in mice, which is further increased in the presence of tumor. This cold-stress significantly impacts experimental outcomes. Data from our lab and others suggest standard housing fundamentally alters murine physiology, and this can produce altered immune baselines in tumor and other disease models. Researchers may thus underestimate the efficacy of therapies that are benefitted by immune responses. A potential mediator, norepinephrine, also underlies stress pathways common in mice and humans. Therefore, research into mechanisms connecting cold-stress and norepinephrine signaling with immune depression in mice could highlight new combination therapies for humans to simultaneously target stress while stimulating anti-tumor immunity.

The surgically induced stress response

The stress response to surgery, critical illness, trauma, and burns encompasses derangements of metabolic and physiological processes that induce perturbations in the inflammatory, acute phase, hormonal, and genomic responses. Hypermetabolism and hypercatabolism result, leading to muscle wasting, impaired immune function and wound healing, organ failure, and death. The surgery-induced stress response is largely similar to that triggered by traumatic injuries; the duration of the stress response, however, varies according to the severity of injury (surgical or traumatic). This spectrum of injuries and insults ranges from small lacerations to severe insults such as large poly-traumatic and burn injuries. Burn injuries provide an extreme model of trauma induced stress responses that can be used to study the long-term effects of a prolonged stress response. Although the stress response to acute trauma evolved to confer improved chances of survival following injury, in modern surgical practice the stress response can be detrimental.

Tight glucose control in critically ill children--a systematic review and meta-analysis

BACKGROUND

It is unclear if tight glucose control (TGC) with intensive insulin therapy (IIT) can improve outcomes in critically ill children admitted to the intensive care unit (ICU). The objective of this systematic review and meta-analysis is to describe the benefits and risks of TGC with IIT in critically ill children and explore differences between published studies.

METHODS

Prospective randomized controlled trials (RCTs) of TGC with IIT in critically ill children admitted to the ICU were identified through a search of MEDLINE, PubMed, EMBASE, Scopus, ISI Web of Science and Cochrane Database of Systematic Reviews as well as detailed citation review of relevant primary and review articles. RCTs of TGC with IIT in critically ill adults and preterm neonates were excluded. Data on study design and setting, sample size, incidence of hypoglycemia, incidence of acquired infection, and 30-day mortality were abstracted. Meta-analytic techniques were used for analysis of outcomes including 30-day mortality, acquired infection, and incidence of hypoglycemia.

RESULTS

We identified four RCTs of TGC with IIT in critically ill children that included 3288 subjects. Overall, TGC with IIT did not result in a decrease in 30-day mortality [odds ratio (OR): 0.79; 95% confidence interval (CI): 0.55-1.15, p = 0.22]. TGC with IIT was associated with decrease in acquired infection (OR: 0.76; 95% CI: 0.59-0.99, p = 0.04). TGC with IIT was also associated with significant increase in hypoglycemia (OR: 6.14; 95% CI: 2.74-13.78, p < 0.001).

CONCLUSIONS

TGC with IIT does not result in decrease in 30-day mortality, but appears to reduce acquired infection in critically ill children. However, TGC with IIT is associated with higher incidence of hypoglycemia. Large multi-center studies of TGC with IIT using continuous glucose monitoring in critically ill children are needed to determine if this strategy can definitively improve clinical outcomes in this population without increasing hypoglycemia.

Hemodynamic responses to dexmedetomidine in critically injured intubated pediatric burned patients: a preliminary study

Because of ineffectiveness and tolerance to benzodiazepines and opioids developing with time, drugs acting via other receptor systems (eg, α-2 agonists) have been advocated in burn patients to improve sedation and analgesia. This study in severely burned pediatric subjects examined the hemodynamic consequences of dexmedetomidine (Dex) administration. Eight intubated patients with ≥20 to 79% TBSA burns were studied between 7 and 35 days after injury. After baseline measurements of mean arterial blood pressure and heart rhythm were taken, each patient received a 1.0 µg/kg bolus of Dex followed by an ascending dose infusion protocol (0.7-2.5 µg/kg/hr), with each dose administered for 15 minutes. There was significant hypotension (27±7.5%, average drop in mean arterial pressure [MAP] ± SD), and a decrease in heart rate (HR; 19% ± 7, average drop in HR ± SD). The average HR decreased from 146 beats per minute to 120. No bradycardia (HR < 60) or heart blocks were observed. In three patients, the MAP decreased to <50mm Hg with the bolus dose of Dex. Of the remaining five patients, three patients completed the study receiving the highest infusion dose of Dex (2.5 µg/kg/hr), whereas in 2 patients the infusion part of the study was begun, but the study was stopped due to persistent hypotension (MAP < 50mm Hg). These observations indicate that a bolus dose of Dex (1.0 µg/kg for 10 minutes) and high infusion rates may require fluid resuscitation or vasopressor support to maintain normotension in critically injured pediatric burn patients.

Norepinephrine inhibits macrophage migration by decreasing CCR2 expression

Increased incidences of infectious and septic complications during post-burn courses represent the main contributor to burn injury mortality. Sustained increases in catecholamine levels, especially norepinephrine (NE), contribute to immune disturbances in severely burned patients. The precise mechanisms underlying NE-mediated immunoregulation are not fully understood. Here we hypothesize that persistently elevated NE levels are associated with immunodysfunctions. We examined the effects of NE on the phenotype and functions of bone marrow-derived macrophages (BMMs). Whole mouse bone marrow cells were treated in vitro with 40 ng/mL of M-CSF and with 1 x 10^-6 M or 1 x 10^-8 M of NE or without NE for 7 days; cells were collected and stained with antibodies for CD11b, F4/80, MHC II and the inflammatory CC chemokine receptor 2 (CCR2). We found 1 x 10^-6 M of NE inhibited MHC II and CCR2 expression on CD11b⁺/F4/80⁺ BMM cells. It also inhibited BMM proliferation by inhibiting CSF-1R expression. On the contrary, 1 x 10^-8 M of NE slightly increased both MHC II and CCR2 expression on CD11b⁺/F4/80⁺ BMM cells but inhibited CD11b⁺/F4/80⁺ BMM proliferation. MCP-1 based migration assay showed that the migration of 1 x 10^-6 M of NE-treated BMM toward MCP-1 was significantly decreased compared to BMM without NE treatment. Both 1 x 10^-8 M and 1 x 10^-6 M of NE enhanced TNF-α production and phagocytosis of FITC-Dextran. Intracellular staining of transcriptional factor MafB showed that 1 x 10^-6 M of NE treatment enhanced its expression, whereas 1 x 10^-8 M of NE decreased expression. Stimulation with LPS in the last 24-hours of BMM culture further decreased CCR2 and MHC II expression of these BMM, suggesting the synergistic effect of LPS and NE on macrophage. Our results demonstrate that NE regulates macrophage differentiation, proliferation and function, and may play a critical role in the dysfunctional immune response post-burn.

The impact of severe burns on skeletal muscle mitochondrial function

Severe burns induce a pathophysiological response that affects almost every physiological system within the body. Inflammation, hypermetabolism, muscle wasting, and insulin resistance are all hallmarks of the pathophysiological response to severe burns, with perturbations in metabolism known to persist for several years post injury. Skeletal muscle is the principal depot of lean tissue within the body and as the primary site of peripheral glucose disposal, plays an important role in metabolic regulation. Following a large burn, skeletal muscle functions as and endogenous amino acid store, providing substrates for more pressing functions, such as the synthesis of acute phase proteins and the deposition of new skin. Subsequently, burn patients become cachectic, which is associated with poor outcomes in terms of metabolic health and functional capacity. While a loss of skeletal muscle contractile proteins per se will no doubt negatively impact functional capacity, detriments in skeletal muscle quality, i.e. a loss in mitochondrial number and/or function may be quantitatively just as important. The goal of this review article is to summarise the current understanding of the impact of thermal trauma on skeletal muscle mitochondrial content and function, to offer direction for future research concerning skeletal muscle mitochondrial function in patients with severe burns, and to renew interest in the role of these organelles in metabolic dysfunction following severe burns.

Effects of propranolol and exercise training in children with severe burns

OBJECTIVES

To investigate whether propranolol administration blocks the benefits induced by exercise training in severely burned children.

STUDY DESIGN

Children aged 7-18 years (n = 58) with burns covering ≥30% of the total body surface area were enrolled in this randomized trial during their acute hospital admission. Twenty-seven patients were randomized to receive propranolol, whereas 31 served as untreated controls. Both groups participated in 12 weeks of in-hospital resistance and aerobic exercise training. Muscle strength, lean body mass, and peak oxygen consumption (VO2 peak) were measured before and after exercise training. Paired and unpaired Student t tests were used for within and between group comparisons, and χ(2) tests for nominal data.

RESULTS

Age, length of hospitalization, and total body surface area burned were similar between groups. In both groups, muscle strength, lean body mass, and VO2 peak were significantly greater after exercise training than at baseline. The percent change in VO2 peak was significantly greater in the propranolol group than in the control group (P < .05).

CONCLUSIONS

Exercise-induced enhancements in muscle mass, strength, and VO2 peak are not impaired by propranolol. Moreover, propranolol improves the aerobic response to exercise in massively burned children.

Whole body and skeletal muscle protein turnover in recovery from burns

Trauma and critical illness are associated with a stress response that results in increased skeletal muscle protein catabolism, which is thought to facilitate the synthesis of acute phase proteins in the liver as well as proteins involved in immune function. What makes burn injury a unique form of trauma is the existence of vast skin lesions, where the majority of afflicted tissue is often surgically excised post injury. Thereafter, recovery is dependent on the formation of a significant quantity of new skin, meaning that the burned patient requires a large and sustained supply of amino acids to facilitate wound healing. Skeletal muscle has the capacity to store surplus glucose and fatty acids within glycogen and triacylglycerol depots respectively, where glycogen and fatty acids can be mobilized during prolonged periods of caloric restriction or heightened metabolic demand (e.g., exercise), to be catabolized in order to maintain cellular ATP availability. Amino acids, on the other hand, are not generally considered to be stored in such a manner within skeletal muscle, i.e., in a temporary pool independent of structural proteins and cellular organelles etc. Subsequently, in response to severe thermal trauma, skeletal muscle assumes the role of an amino acid reserve where muscle protein breakdown and amino acid release from skeletal muscle serves to buffer plasma amino acid concentrations. Interestingly, it seems like aggressive feeding of the severely burned patient may not necessarily supply amino acids in sufficient abundance to normalize skeletal muscle protein metabolism, suggesting that skeletal muscle becomes an essential store of protein in patients suffering from severe burn trauma. In this article, the effects of burn injury on whole body and skeletal muscle protein metabolism will be discussed in an attempt to distill the current understanding of the impact of this debilitating injury on the redistribution of skeletal muscle protein stores.

Burns: an update on current pharmacotherapy

INTRODUCTION

The worldwide occurrence of burn injuries remains high despite efforts to reduce injury incidence through public awareness campaigns and improvements in living conditions. In 2004, almost 11 million people experienced burns severe enough to warrant medical treatment. Advances over the past several decades in aggressive resuscitation, nutrition, excision and grafting have reduced morbidity and mortality. Incorporation of pharmacotherapeutics into treatment regimens may further reduce complications of severe burn injuries.

AREAS COVERED

Severe burn injuries, as well as other forms of stress and trauma, trigger a hypermetabolic response that, if left untreated, impedes recovery. In the past two decades, use of anabolic agents, β-adrenergic receptor antagonists and anti-hyperglycemic agents has successfully counteracted post-burn morbidities including catabolism, the catecholamine-mediated response and insulin resistance. Here, the authors review the most up-to-date information on currently used pharmacotherapies in the treatment of these sequelae of severe burns and the insights that have expanded the understanding of the pathophysiology of severe burns.

EXPERT OPINION

Existing drugs offer promising advances in the care of burn injuries. Continued gains in the understanding of the molecular mechanisms driving the hypermetabolic response will enable the application of additional existing drugs to be broadened to further attenuate the hypermetabolic response.

Hyperglycemia exacerbates burn-induced liver inflammation via noncanonical nuclear factor-κB pathway activation

Hyperglycemia and inflammation are hallmarks of burn injury. In this study, we used a rat model of hyperglycemia and burn injury to investigate the effects of hyperglycemia on inflammatory responses in the liver. Hyperglycemia was induced in male Sprague-Dawley rats with streptozotocin (STZ) (35-40 mg/kg), followed by a 60% third-degree scald burn injury. Cytokine levels (by multiplex, in cytosolic liver extracts), hormones (by enzyme-linked immunosorbent assay [ELISA], in serum), nuclear factor (NF)-κB protein deoxyribonucleic acid (DNA) binding (by ELISA, in nuclear liver extracts) and liver functional panel (using VetScan, in serum) were measured at different time points up to 7 d after burn injury. Blood glucose significantly increased after burn injury in both groups with different temporal patterns. Hyperglycemic rats were capable of endogenous insulin secretion, which was enhanced significantly versus controls 12 h after burn injury. DNA binding data of liver nuclear extracts showed a robust and significant activation of the noncanonical NF-κB pathway in the hyperglycemic versus control burn animals, including increased NF-κB-inducing kinase expression (p < 0.05). Liver acute-phase proteins and cytokine expression were increased, whereas secretion of constitutive proteins was decreased after burn injury in hyperglycemic versus control animals (p < 0.05). These results indicate that burn injury to the skin rapidly activated canonical and noncanonical NF-κB pathways in the liver. Robust activation of the NF-κB noncanonical pathway was associated with increased expression of inflammatory markers and acute-phase proteins, and impaired glucose metabolism. Hyperglycemia is detrimental to burn outcome by augmenting inflammation mediated by hepatic noncanonical NF-κB pathway activation.

17β-Estradiol reappropriates mass lost to the hypermetabolic state in thermally injured rats

BACKGROUND

The hypermetabolic response to severe thermal injury is unlike any physiologic response seen in medicine. While some parallels can be drawn to shock and sepsis states, this response is typified by its intensity and duration. Our group has been interested in the myriad effects of estrogens after injury, specifically the ability of estrogens to reduce inflammatory responses. Given this, and the known link between severe inflammation and the hypermetabolic response, we examined the effects of a single dose of 17β estradiol administered after a severe thermal injury in rats.

METHODS

Twelve male Sprague-Dawley rats were subject to either a sham burn or a 40% total body surface area burn, followed by fluid resuscitation. Burned animals were divided into a vehicle and treatment group, with injections given 15 min after the injury. Animals were monitored for a period of 45 d, with markers of hypermetabolism (weight, fecal output, food intake, and serum insulin and glucose) measured daily.

RESULTS

We identified a significant difference in daily measured weights between the burned groups. We observed a sparing of body mass during the acute phase lasting 2 wk after the injury and an improved recovery phase during the remainder of the study. Glucose and insulin levels during the first week of the study did not differ between the treatment groups.

CONCLUSION

Estrogen may have a role in preserving body mass after severe thermal injury. Further studies are required to determine if this spared body mass composition.

Propranolol improves impaired hepatic phosphatidylinositol 3-kinase/akt signaling after burn injury

Severe burn injury is associated with induction of the hepatic endoplasmic reticulum (ER) stress response. ER stress leads to activation of c-Jun N-terminal kinase (JNK), suppression of insulin receptor signaling via phosphorylation of insulin receptor substrate 1 and subsequent insulin resistance. Marked and sustained increases in catecholamines are prominent after a burn. Here, we show that administration of propranolol, a nonselective β1/2 adrenergic receptor antagonist, attenuates ER stress and JNK activation. Attenuation of ER stress by propranolol results in increased insulin sensitivity, as determined by activation of hepatic phosphatidylinositol 3-kinase and Akt. We conclude that catecholamine release is responsible for the ER stress response and impaired insulin receptor signaling after burn injury.

Role of the PPAR-α agonist fenofibrate in severe pediatric burn

Fenofibrate is a peroxisome proliferator activated receptor alpha agonist that contains both pro and anti-inflammatory properties, and has been used in the treatment of dyslipidemia and diabetes for decades. Its receptors are expressed in the liver, skeletal muscle, cardiac, enteric, and renal cells, which allow it to provide systemic regulation of lipoprotein metabolism, fatty acid oxidation, and fatty acid transport. Hyperglycemia is a common complication found in the burn population because hepatic glucose production and catecholamine-mediated hepatic glycogenolysis are augmented. Insulin resistance occurs often in these patients and is associated with poor outcomes. In the pediatric burn population, fenofibrate has been found to ameliorate or decrease the number of hypoglycemic episodes when compared to management with insulin alone. Its mechanism of action is thought to involve an improvement in insulin signaling in skeletal muscle, as well as improvements in mitochondrial function, glucose oxidation, and insulin sensitivity. The long term use of fenofibrate in severely burned patients may improve hyperglycemia and insulin resistance, as well as improve wound healing, and reduce apoptosis, and oxidative stress.

Stress hyperglycemia in pediatric critical illness: the intensive care unit adds to the stress!

Stress hyperglycemia (SH) commonly occurs during critical illness in children. The historical view that SH is beneficial has been questioned in light of evidence that demonstrates the association of SH with worse outcomes. In addition to intrinsic changes in glucose metabolism and development of insulin resistance, specific intensive care unit (ICU) practices may influence the development of SH during critical illness. Mechanical ventilation, vasoactive infusions, renal replacement therapies, cardiopulmonary bypass and extracorporeal life support, therapeutic hypothermia, prolonged immobility, nutrition support practices, and the use of medications are all known to mediate development of SH in critical illness. Tight glucose control (TGC) to manage SH has emerged as a promising therapy to improve outcomes in critically ill adults, but results have been inconclusive. Large variations in ICU practices across studies likely resulted in inconsistent results. Future studies of TGC need to take into account the impact of commonly used ICU practices and, ideally, standardize protocols in an attempt to improve the accuracy of conclusions from such studies.

Changes in cardiac physiology after severe burn injury

Cardiac stress, mediated by increased catecholamines, is the hallmark of severe burn injury typified by marked tachycardia, increased myocardial oxygen consumption, and increased cardiac output (CO). It remains one of the main determinants of survival in large burns. Currently, it is unknown for how long cardiac stress persists after a severe injury. Therefore, the aim of this study was to determine the extent and duration of cardiac stress after a severe burn. To determine persistence of cardiac alteration, the authors determined cardiac parameters of all surviving patients with burns ≥ 40% TBSA from 1998 to 2008. One hundred ninety-four patients were included in this study. Heart rate, mean arterial pressure, CO, stroke volume, cardiac index, and ejection fractions were measured at regular intervals from admission up to 2 years after injury. Rate pressure product was calculated as a correlate of myocardial oxygen consumption. All values were compared with normal nonburned children to validate the findings. Statistical analysis was performed using log transformed analysis of variance with Bonferroni correction and Student's t-test, where applicable. Heart rate, CO, cardiac index, and rate pressure product remained significantly increased in burned children for up to 2 years when compared with normal ranges (P < .05), indicating vastly increased cardiac stress. Ejection fraction was within normal limits for 2 years. Cardiac stress persists for at least 2 years postburn, and the authors suggest that attenuation of these detrimental responses may improve long-term morbidity.