Fatty infiltration of the liver in severely burned pediatric patients: autopsy findings and clinical implications

Update on Hypermetabolism in Pediatric Burn Patients

Despite advancements in pediatric burn care, the profound hypermetabolic response associated with severe burns remains a multifaceted challenge throughout the continuum of care. Understanding the various physiologic disturbances that constitute hypermetabolism is crucial for a thorough evaluation and for implementing appropriate surgical and nonsurgical interventions. In this article, we describe the pathophysiology and treatment of hypermetabolism in pediatric burn patients with a focus on reducing resting energy requirements, minimizing infection, and optimizing nutrition for patients undergoing frequent surgical intervention.

Correlation of thermal burn hepatic dysfunction with outcomes

INTRODUCTION

Organ dysfunction and failure increase the morbidity and mortality following major burn. Alteration of liver morphology and function is common following major burns; however, it has not received much attention. In this study we have assessed the impact of thermal burn on liver in relation with mortality.

MATERIAL AND METHODS

55 patients (33 female and 22 males) with TBSA 10-90% and age ranged from 18 to 75 years were included. A bed side serial ultrasonography to assess the volume of liver and liver function tests was done on the 2nd, 9th and 16th day following burn. Baseline demographic and clinical information such as age, gender, burn size and outcome of patient were also collected.

RESULTS -

8 patients died during 2nd week following burn and 47 survived. The mean TBSA for survivors was 37% and for non survivors 80%. Mean liver volume in survivors steadily decreased from 1693.70 cm3 to 1631.31 cm3 over 3 weeks. Mean liver volume in non- survivors steadily increased from 1855.88 cm3 to 2028.50 cm3 over 2 weeks. Liver function test in survivors steadily improved while in non survivors it deteriorated over 2 weeks.

CONCLUSION

There is a correlation between altered liver morphology and function with mortality among severely burnt patients however liver volume did not show statistical significance. A decreasing trend of liver dysfunction parameters and hepatomegaly following burn is associated with good prognosis.

Systemic immune response of burns from the acute to chronic phase

Immune responses that occur following burn injury comprise a series of reactions that are activated in response to damaged autologous tissues, followed by removal of damaged tissues and foreign pathogens such as invading bacteria, and tissue repair. These immune responses are considered to be programmed in living organisms. Developments of modern medicine have led to the saving of burned patients who could not be cured previously; however, the programmed response is no longer able to keep up, and various problems have arisen. This paper describes the mechanism of immune response specific to burn injury and the emerging concept of persistent inflammation, immunosuppression, and catabolism syndrome.

The use of propranolol in adult burn patients: Safety and outcome influence

OBJECTIVES

This study investigated safety and effect of propranolol on adult patients with severe burn.

METHODS

A prospective study was conducted on 124 severely adult burn patients who were randomly divided into propranolol and non-propranolol group. Propranolol was given by nasogastric tube to achieve the target of lowering 15-20% of initial heart rate.

RESULTS

Average dose of propranolol was 1.9 ± 0.5 mg/kg/day ranging from 0.9 to 3.3 mg/kg/day and was not affected by burn extent and inhalation injury. Mean heart rate reduced by 21.2% during the 28 day period. Recorded adverse events included hypotension (11.9%), bradycardia (1.6%), hypoglycemia (17.7%) and total number of held events was 8 occurring in 7 (11.3%) patients. Serum levels of glucose, total protein, albumin, cholesterol and triglyceride at different times were not significantly different between the two groups. Significantly lower resting energy expenditure on the 7^th and 14^th day were seen in propranolol group (p < 0.05). After 3 weeks, liver size in the propranolol group did not change significantly from admission, while in the non-propranolol group, liver size increased significantly (p < 0.05). The complete healing time of partial-thickness burns and donor sites were significantly shorter in propranolol group (p < 0.01). Duration of ventilation, length of stay in intensive care unit and in hospital, number of operations, rate of multiple organ failure, and death were not different between the two groups (p > 0.05).

CONCLUSION

For severely burned adults, propranolol was safe and effective on reducing energy expenditure, limited hepatomegaly, and accelerated partial burn wound and donor site closure, but does not affect length of stay in ICU, hospitalization, complication ormortality rate.

Biomedical applications of tannic acid

Tannic Acid (TA) is a naturally occurring antioxidant polyphenol that has gained popularity over the past decade in the field of biomedical research for its unique biochemical properties. Tannic acid, typically extracted from oak tree galls, has been used in many important historical applications. TA is a key component in vegetable tanning of leather, iron gall ink, red wines, and as a traditional medicine to treat a variety of maladies. The basis of TA utility is derived from its many hydroxyl groups and its affinity for forming hydrogen bonds with proteins and other biomolecules. Today, the study of TA has led to the development of many new pharmaceutical and biomedical applications. TA has been shown to reduce inflammation as an antioxidant, act as an antibiotic in common pathogenic bacterium, and induce apoptosis in several cancer types. TA has also displayed antiviral and antifungal activity. At certain concentrations, TA can be used to treat gastrointestinal disorders such as hemorrhoids and diarrhea, severe burns, and protect against neurodegenerative diseases. TA has also been utilized in biomaterials research as a natural crosslinking agent to improve mechanical properties of natural and synthetic hydrogels and polymers, while also imparting anti-inflammatory, antibacterial, and anticancer activity to the materials. TA has also been used to develop thin film coatings and nanoparticles for drug delivery. In all, TA is fascinating molecule with a wide variety of potential uses in pharmaceuticals, biomaterials applications, and drug delivery strategies.

Hepatic functional pathophysiology and morphological damage following severe burns: a systematic review and meta-analysis

INTRODUCTION

Severe burns are devastating injuries affecting multiple organ systems. Little is known about the influence on the hepatic system and its physiology. This systematic review aimed to assess the current state of research on morphologic liver damage following severe burns.

METHODS

A search was conducted in Pubmed, Web of Science and Cochrane databases using PRISMA guidelines. Outcomes included serum levels of transaminases, fatty infiltration and necrosis. Weighted individual study estimates were used to calculate pooled transaminase levels and necrosis/fatty infiltration rates using a random-effects approach. Risk ratios (RRs) or Odds ratios (ORs) and 95% confidence intervals (CIs) were used to describe pooled estimates for risk factors.

RESULTS

The literature search retrieved 2548 hits, of which 59 studies were included into qualitative synthesis, and finally ten studies were included into meta-analysis. Studies were divided into those reporting autopsies and those reporting changes of serum transaminase levels. The majority of liver autopsies showed fatty infiltration 82% (95% CI39%-97%) or necrosis of the liver 18% (95% CI13%-24%).

DISCUSSION

Heterogeneity in studies on hepatic functional damage following severe burns was high. Only few were well-designed and published in recent years. Many studies could not be included because of insufficient numerical data. There is a high number of patients deceasing from burns that present with fatty infiltration or necrosis of hepatic tissue. Transaminases were elevated during the first days after burn. Further research on how severe burns affect the hepatic function and outcome, especially long-term, is necessary.

Glucose Metabolism in Burns-What Happens?

Severe burns represent an important challenge for patients and medical teams. They lead to profound metabolic alterations, trigger a systemic inflammatory response, crush the immune defense, impair the function of the heart, lungs, kidneys, liver, etc. The metabolism is shifted towards a hypermetabolic state, and this situation might persist for years after the burn, having deleterious consequences for the patient's health. Severely burned patients lack energy substrates and react in order to produce and maintain augmented levels of glucose, which is the fuel "ready to use" by cells. In this paper, we discuss biological substances that induce a hyperglycemic response, concur to insulin resistance, and determine cell disturbance after a severe burn. We also focus on the most effective agents that provide pharmacological modulations of the changes in glucose metabolism.

Advanced age heightens hepatic damage in a murine model of scald burn injury

BACKGROUND

Elderly burn patients exhibit a lower survival rate compared with younger counterparts. The liver is susceptible to damage after burn injury, which predisposes to poor outcomes. Lipid homeostasis and the antioxidant glutathione system play fundamental roles in preserving liver integrity. Herein, we explored changes in these major pathways associated with liver damage in the aging animals after burn injury.

METHODS

We compared liver enzymes, histology, lipid-peroxidation, and glutathione-metabolism profiles from young and aged female mice after a 15% total body surface area burn. Mice were euthanized at 24 hours after injury, and livers and serum were collected.

RESULTS

Aged burn animals exhibited elevated (p < 0.05) aspartate aminotransferase and alanine aminotransferase levels and increased inflammatory cell infiltration, edema, and necrosis compared with their younger counterparts. The percentage of adipophilin-stained area in livers from young sham, young burn, aged sham, and aged burn groups was 10%, 44%, 16%, and 78% (p < 0.05), respectively. Liver malondialdehyde levels were 1.4 ± 0.5 nmol/mg, 2.06 ± 0.2 nmol/mg, 1.81 ± 0.12 nmol/mg, and 3.45 ± 0.2 nmol/mg (p < 0.05) in young sham, young burn, aged sham, and aged burn mice, respectively. Oxidized glutathione (GSSG) content increased 50% in the young burn, and 88% in aged burn animals compared with the young sham group (p < 0.05). The reduced glutathione GSH/GSSG ratio was significantly reduced by 54% in aged burn mice compared with young sham animals (p < 0.05). Furthermore, glutathione peroxidase gene expression showed a 96% decrease in the aged burn group compared with young sham mice (p < 0.05).

CONCLUSION

Aged burn animals exhibit severe liver damage from heightened lipid peroxidation and inadequate antioxidative response. The increased peroxidation is associated with abundant lipid deposits in hepatic tissue postburn and a weak antioxidative response due to hepatic glutathione peroxidase downregulation. Further studies will focus on the functional significance of these findings concerning hepatic homeostasis.

Geometric framework reveals that a moderate protein, high carbohydrate intake is optimal for severe burn injury in mice

Nutritional therapy is a cornerstone of burns management. The optimal macronutrient intake for wound healing after burn injury has not been identified, although high-energy, high-protein diets are favoured. The present study aimed to identify the optimal macronutrient intake for burn wound healing. The geometric framework (GF) was used to analyse wound healing after a 10 % total body surface area contact burn in mice ad libitum fed one of the eleven high-energy diets, varying in macronutrient composition with protein (P5-60 %), carbohydrate (C20-75 %) and fat (F20-75 %). In the GF study, the optimal ratio for wound healing was identified as a moderate-protein, high-carbohydrate diet with a protein:carbohydrate:fat (P:C:F) ratio of 1:4:2. High carbohydrate intake was associated with lower mortality, improved body weight and a beneficial pattern of body fat reserves. Protein intake was essential to prevent weight loss and mortality, but a protein intake target of about 7 kJ/d (about 15 % of energy intake) was identified, above which no further benefit was gained. High protein intake was associated with delayed wound healing and increased liver and spleen weight. As the GF study demonstrated that an initial very high protein intake prevented mortality, a very high-protein, moderate-carbohydrate diet (P40:C42:F18) was specifically designed. The dynamic diet study was also designed to combine and validate the benefits of an initial very high protein intake for mortality, and subsequent moderate protein, high carbohydrate intake for optimal wound healing. The dynamic feeding experiment showed switching from an initial very high-protein diet to the optimal moderate-protein, high-carbohydrate diet accelerated wound healing whilst preventing mortality and liver enlargement.

NAFLD Aggravates Septic Shock Due to Inadequate Adrenal Response and 11β-HSDs Dysregulation in Rats

Background: Non-alcoholic fatty liver disease (NAFLD) is linked with metabolic syndrome. Previous studies showed that obesity may disrupt adrenal function and adversely affect its counter-regulations against shock. This study hence evaluated adrenal function abnormalities in NAFLD with shock. Methods: Sprague-Dawley rats were fed with regular chow-diet (control) or high fat diet (HFD, 60% energy derived from fat). Blood tests were performed at the end of the 4th, 6th and 8th week, respectively. Experiments were performed at the end of the 8th week. Results: HFD rats developed NAFLD. HFD rats had 27% and 51% increase in plasma corticosterone at the 6th and 8th week in usual status. However, HFD rats had 5 times more reduction of mean arterial pressure in response to lipopolysaccharide-induced sepsis as compared to control rats. The corticosterone increment ratio was also lower in HFD rats, even after ACTH administration. 11β-HSD system tended to generate more corticosterone in HFD rats under hemodynamic stable status without shock and the trend was lost in HFD rats with septic shock. Conclusion: Rats with NAFLD had profound septic shock due to inadequate corticosterone response. This is, at least partly, due to 11β-HSDs dysregulation in sepsis.

Enteral vs. parenteral nutrition in septic shock: are they equivalent?

PURPOSE OF REVIEW

The current review focuses on recent clinical evidence and updated guideline recommendations on the effects of enteral vs. parenteral nutrition in adult critically ill patients with (septic) shock.

RECENT FINDIGS

The largest multicenter randomized-controlled trial showed that the route of nutrient supply was unimportant for 28-day and 90-day mortality, infectious morbidity and length of stay in mechanically ventilated patients with shock. The enteral route, however, was associated with lower macronutrient intake and significantly higher frequency of hypoglycemia and moderate-to-severe gastrointestinal complications. Integrating these findings into recent meta-analyses confirmed that the route per se has no effect on mortality and that interactions with (infectious) morbidity are inconsistent or questionable.

SUMMARY

The strong paradigm of favoring the enteral over the parenteral route in critically ill patients has been challenged. As a consequence, updated guidelines recommend withholding enteral nutrition in patients with uncontrolled shock. It is still unclear, however, whether parenteral nutrition is advantageous in patients with shock although benefits are conceivable in light of less gastrointestinal complications. Thus far, no guideline has addressed indications for parenteral nutrition in these patients. By considering recent scientific evidence, specific guideline recommendations, and expert opinions, we present a clinical algorithm that may facilitate decision-making when feeding critically ill patients with shock.

Metformin alleviates muscle wasting post-thermal injury by increasing Pax7-positive muscle progenitor cells

BACKGROUND

Profound skeletal muscle wasting and weakness is common after severe burn and persists for years after injury contributing to morbidity and mortality of burn patients. Currently, no ideal treatment exists to inhibit muscle catabolism. Metformin is an anti-diabetic agent that manages hyperglycemia but has also been shown to have a beneficial effect on stem cells after injury. We hypothesize that metformin administration will increase protein synthesis in the skeletal muscle by increasing the proliferation of muscle progenitor cells, thus mitigating muscle atrophy post-burn injury.

METHODS

To determine whether metformin can attenuate muscle catabolism following burn injury, we utilized a 30% total burn surface area (TBSA) full-thickness scald burn in mice and compared burn injuries with and without metformin treatment. We examined the gastrocnemius muscle at 7 and 14 days post-burn injury.

RESULTS

At 7 days, burn injury significantly reduced myofiber cross-sectional area (CSA) compared to sham, p < 0.05. Metformin treatment significantly attenuated muscle catabolism and preserved muscle CSA at the sham size. To investigate metformin's effect on satellite cells (muscle progenitors), we examined changes in Pax7, a transcription factor regulating the proliferation of muscle progenitors. Burned animals treated with metformin had a significant increase in Pax7 protein level and the number of Pax7-positive cells at 7 days post-burn, p < 0.05. Moreover, through BrdU proliferation assay, we show that metformin treatment increased the proliferation of satellite cells at 7 days post-burn injury, p < 0.05.

CONCLUSION

In summary, metformin's various metabolic effects and its modulation of stem cells make it an attractive alternative to mitigate burn-induced muscle wasting while also managing hyperglycemia.

Contributing factors and outcomes of burn-associated cholestasis

BACKGROUND & AIMS

Cholestasis often occurs after burn injuries. However, the prevalence of cholestasis and its effect on outcomes in patients with severe burn injuries are unknown. The aim of this study was to describe the course and the burden of cholestasis in a cohort of severely burned adult patients.

METHODS

We investigated the relationship between burn-associated cholestasis (BAC) and clinical outcomes in a retrospective cohort of patients admitted to our unit for severe burn injuries between 2012 and 2015. BAC was defined as an increased level of serum alkaline phosphatase (ALP) ≥1.5x the upper limit of normal (ULN) with an increased level of gamma-glutamyltransferase (GGT) ≥3x ULN, or as an increased level of total bilirubin ≥2x ULN.

RESULTS

A total of 214 patients were included: 111 (52%) patients developed BAC after a median (IQR) stay of 9 (5-16) days. At 90 days, the mortality rate was 20%, including 34 and 9 patients with and without BAC (p <0.001), respectively, which corresponded to a 2.5-fold higher (95% CI 1.2-5.2, p = 0.012) risk of 90-day mortality for patients with BAC. After being adjusted for severity of illness, patients with BAC, hyperbilirubinemia and without elevated ALP and GGT levels had a hazard ratio of 4.51 (95% CI 1.87-10.87) for 90-day mortality. BAC was associated with the severity of the burn injury, shock and bacteraemia. BAC was present in 38 (51%) patients at discharge, and 7 (18%) patients had secondary sclerosing cholangitis. These patients maintained elevated levels of ALP and GGT that were 5.8x (1.7-15) the ULN and 11x the ULN (4.5-22), respectively, 20 months (3.5-35) after discharge.

CONCLUSION

BAC is prevalent among patients with severe burn injuries and is associated with worse short-term outcomes, especially when total bilirubin levels were increased without elevated ALP and GGT levels. BAC survivors are at risk of developing sclerosing cholangitis.

LAY SUMMARY

Cholestasis is common after burn injuries and is associated with burn severity, sepsis, organ failure and mortality. Patients with hyperbilirubinemia without elevated alkaline phosphatase and gamma-glutamyltransferase levels after the burn injury have a poor prognosis. Patients with burn-associated cholestasis may develop sclerosing cholangitis and secondary biliary cirrhosis.

Novel pharmacotherapy for burn wounds: what are the advancements

INTRODUCTION

The prognosis for severe burns has improved significantly over the past 50 years. Meanwhile, burns have become an affliction mainly affecting the less well-developed regions of the world. Early excision and skin grafting has led to major improvements in therapeutic outcomes.

AREAS COVERED

The purpose of this article is to survey the use of pharmacotherapy to treat different pathophysiological complications of burn injury. The author, herein, discusses the use of drug treatments for a number of systemic metabolic disturbances including hyperglycemia, elevated catabolism, and gluconeogenesis.

EXPERT OPINION

Advancements in personalized and molecular medicine will make an impact on burn therapy. Similarities between severe burns and other critically ill patients will lead to cross-fertilization between different medical specialties. Furthermore, advances in stem cells and tissue regeneration will lead to improved healing and less lifelong disability. Indeed, research in new drug therapy for burns is actively progressing for many different complications.

NLRP3 Inflammasome Modulates Post-Burn Lipolysis and Hepatic Fat Infiltration via Fatty Acid Synthase

Burns result in generalized catabolism, lipolysis, and hyperinflammation. NLRP3 inflammasome, a mediator of hyperinflammation, is upregulated in burn patients' adipose tissue within 7 days post-burn. However, its role during the acute phase is unknown. Here, wild-type (WT) and NLRP3 knockout (NLRP3^-/-) mice were exposed to 25% TBSA scald burn. Flow cytometric analysis demonstrated greater liver macrophage infiltration in NLRP3^-/- yet decreased protein expression of NLRP3 components, ER stress, and apoptosis. NLRP3^-/- had increased circulating free fatty acids (FFA), fatty deposition and liver weight 1 hour post-burn. Alterations in adipose fatty acid synthase (Fasn) expression affects FFA levels post-burn; WT have an early peak in Fasn gene and protein expression that is lost in NLRP3^-/-, resulting in increased lipolysis and hepatic fatty deposition. In summary, our findings reveal that NLRP3 inflammasome activation is a double-edged sword. While prolonged inflammation and long-term effects of macrophage activation are associated with poor outcomes, acute inflammation may be beneficial. These results highlight the important metabolic role that NLRP3 inflammasome plays in the acute phase, ultimately affecting survival post-burn.

Anabolic and anticatabolic agents in critical care

PURPOSE OF REVIEW

A complex network of hormones and other effectors characterize the hypermetabolic response in critical illness; these mediators work together to induce numerous pathophysiologic alterations. Increased incidence of infection, multiorgan failure, long-term debilitation, delays in rehabilitation, and death result from an inability to meet the prohibitively elevated protein and energy requirements, which occur during illness and can persist for several years. Pharmacologic interventions have been successfully utilized to attenuate particular aspects of the hypermetabolic response; these modalities are a component of managing critically ill patients - including those patients with severe burns. Here, we review recent advances in pharmacologically attenuating the hypermetabolic and catabolic responses.

RECENT FINDINGS

Propranolol, a nonspecific β-adrenergic receptor antagonist, is one of the most widely used anticatabolic therapies. Oxandrolone, testosterone, and intensive insulin therapy represent anabolic pharmacological strategies. Promising therapies, such as metformin, glucagon-like peptide 1, peroxisome proliferator-activated receptor agonists, are currently being investigated.

SUMMARY

Profound metabolic derangements occur in critically ill patients; this hypermetabolic response is a major contributor to adverse outcomes. Despite the pharmacological therapies currently available to counteract this devastating cascade, future studies are warranted to explore new multimodality agents that will counteract these effects while maintaining glycemic control and preventing unfavorable complications.

Alcohol Modulation of the Postburn Hepatic Response

The widespread and rapidly increasing trend of binge drinking is accompanied by a concomitant rise in the prevalence of trauma patients under the influence of alcohol at the time of their injury. Epidemiological evidence suggests up to half of all adult burn patients are intoxicated at the time of admission, and the presence of alcohol is an independent risk factor for death in the early stages post burn. As the major site of alcohol metabolism and toxicity, the liver is a critical determinant of postburn outcome, and experimental evidence implies an injury threshold exists beyond which burn-induced hepatic derangement is observed. Alcohol may lower this threshold for postburn hepatic damage through a variety of mechanisms including modulation of extrahepatic events, alteration of the gut-liver axis, and changes in signaling pathways. The direct and indirect effects of alcohol may prime the liver for the second-hit of many overlapping physiologic responses to burn injury. In an effort to gain a deeper understanding of how alcohol potentiates postburn hepatic damage, the authors summarize possible mechanisms by which alcohol modulates the postburn hepatic response.

Feeding the critically ill obese patient: a systematic review protocol

REVIEW QUESTION/OBJECTIVE

The objective of this review is to identify effective enteral nutritional regimens targeting protein and calorie delivery for the critically ill obese patient on morbidity and mortality.More specifically, the review question is:In the critically ill obese patient, what is the optimal enteral protein and calorie target that improves mortality and morbidity?

BACKGROUND

The World Health Organization (WHO) defines obesity as abnormal or excessive fat accumulation that may impair health, or, empirically, as a body mass index (BMI) ≥ 30 kg/m. Twenty-eight percent of the Australian population is obese with the prevalence rising to 44% in rural areas, and there is evidence that rates of obesity are increasing. The prevalence of obese patients in intensive care largely mirrors that of the general population. There is concern, however, that this may also be rising. A recently published multi-center nutritional study of critically ill patients reported a mean BMI of 29 in their sample, suggesting that just under 50% of their intensive care population is obese. It is inevitable, therefore, that the intensivist will care for the critically ill obese patient.Managing the critically ill obese patient is challenging, not least due to the co-morbid diseases frequently associated with obesity, including diabetes mellitus, cardiovascular disease, dyslipidaemia, sleep disordered breathing and respiratory insufficiency, hepatic steatohepatitis, chronic kidney disease and hypertension. There is also evidence that metabolic processes differ in the obese patient, particularly those with underlying insulin resistance, itself a marker of the metabolic syndrome, which may predispose to futile cycling, altered fuel utilization and protein catabolism. These issues are compounded by altered drug pharmacokinetics, and the additional logistical issues associated with prophylactic, therapeutic and diagnostic interventions.It is entirely plausible that the altered metabolic processes observed in the obese intensify and compound the metabolic changes that occur during critical illness. The early phases of critical illness are characterized by an increase in energy expenditure, resulting in a catabolic state driven by the stress response. Activation of the stress response involves up-regulation of the sympathetic nervous system and the release of pituitary hormones resulting in altered cortisol metabolism and elevated levels of endogenous catecholamines. These produce a range of metabolic disturbances including stress hyperglycemia, arising from both peripheral resistance to the effects of anabolic factors (predominantly insulin) and increased hepatic gluconeogenesis. Proteolysis is accelerated, releasing amino acids that are thought to be important in supporting tissue repair, immune defense and the synthesis of acute phase reactants. There is also altered mobilization of fuel stores, futile cycling, and evidence of altered lipoprotein metabolism. In the short term this is likely to be an adaptive response, but with time and ongoing inflammation this becomes maladaptive with a concomitant risk of protein-calorie malnutrition, immunosuppression and wasting of functional muscle tissue resulting from protein catabolism, and this is further compounded by disuse atrophy. Muscle atrophy and intensive care unit (ICU) acquired weakness is complex and poorly understood, but it is postulated that the provision of calories and sufficient protein to avoid a negative nitrogen balance mitigates this process. Avoiding lean muscle mass loss in the obese intuitively has substantial implications, given the larger mass that is required to be mobilized during their rehabilitation phase.There is, in addition, evolving evidence that hormones derived from both the gut and adipose tissue are also involved in the response to stress and critical illness, and that adipose tissue in particular is not a benign tissue bed, but rather should be considered an endocrine organ. Some of these hormones are thought to be pro-inflammatory and some anti-inflammatory; however both the net result and clinical significance of these are yet to be fully elucidated.The provision of adequate nutrition has become an integral component of supportive ICU care, but is complex. There is ongoing debate within critical care literature regarding the optimal route of delivery, the target dose, and the macronutrient components (proportion of protein and non-protein calories) of nutritional support. A number of studies have associated caloric deficit with morbidity and mortality, with the resultant assumption that prescribing sufficient calories to match energy expenditure will reduce morbidity and mortality, although the evidence base underpinning this assumption is limited to observational studies and small, randomized trials.There is research available that suggests hyper-caloric feeding or hyper-alimentation, particularly of carbohydrates, may result in increased morbidity including hyperglycemia, liver steatosis, respiratory insufficiency with prolonged duration of mechanical ventilation, re-feeding syndrome and immune suppression. But the results from studies of hypo-caloric and eucaloric feeding regimens in critically ill patients are conflicting, independent of the added metabolic complexities observed in the critically ill obese patient.Notwithstanding the debate regarding the dose and components of nutritional therapy, there is consensus that nutrition should be provided, preferably via the enteral route, and preferably initiated early in the ICU admission. The enteral route is preferred for a variety of reasons, not the least of which is cost. In addition there is evidence to suggest the enteral route is associated with the maintenance of gut integrity, a reduction in bacterial translocation and infection rates, a reduction in the incidence of stress ulceration, attenuation of oxidative stress, release of incretins and other entero-hormones, and modulation of systemic immune responses. Yet there is evidence that the initiation of enteral nutritional support for the obese critically ill patient is delayed, and that when delivered is at sub-optimal levels. The reasons for this remain obscure, but may be associated with the false assumption that every obese patient has nutritional reserves due to their adipose tissues, and can therefore withstand longer periods with no, or reduced nutritional support. In fact obesity does not necessarily protect from malnutrition, particularly protein and micronutrient malnutrition. It has been suggested by some authors that the malnutrition status of critically ill patients is a stronger predictor of mortality than BMI, and that once malnutrition status is controlled for, the apparent protective effects of obesity observed in several epidemiological studies dissipate. This would be consistent with the large body of evidence that associates malnutrition (BMI < 20 kg/m) with increased mortality, and has led some authors to postulate that the weight-mortality relationship is U-shaped. This has proven difficult to demonstrate, however, due to recognized confounding influences such as chronic co-morbidities, baseline nutritional status and the nature of the presenting critical illness.This has led to interest in nutritional regimens targeting alternative calorie and protein goals to protect the obese critically ill patient from complications arising from critical illness, and particularly protein catabolism. However, of the three major nutritional organizations, the American Society of Parenteral and Enteral Nutrition (ASPEN) is the only professional organization to make specific recommendations about providing enteral nutritional support to the critically ill obese patient, recommending a regimen targeting a hypo-caloric, high-protein goal. It is thought that this regimen, in which 60-70% of caloric requirements are provided promotes steady weight loss, while providing sufficient protein to achieve a neutral, or slightly positive, nitrogen balance, mitigating lean muscle mass loss, and allowing for wound healing. Targeting weight loss is proposed to improve insulin sensitivity, improve nursing care and reduce the risk of co-morbidities, although how this occurs and whether it can occur over the relatively short time frame of an intensive care admission (days to weeks) remains unclear. Despite these recommendations observational data of international nutritional practice suggest that ICU patients are fed uniformly low levels of calories and protein across BMI groups.Supporting the critically ill obese patient will become an increasingly important skill in the intensivist's armamentarium, and enteral nutritional therapy forms a cornerstone of this support. Yet, neither the optimal total caloric goal nor the macronutrient components of a feeding regimen for the critically ill obese patient is evident. Although the suggestion that altering the macronutrient goals for this vulnerable group of patients appears to have a sound physiological basis, the level of evidence supporting this remains unclear, and there are no systematic reviews on this topic. The aim of this systematic review is to evaluate existing literature to determine the best available evidence describing a nutritional strategy that targets energy and protein delivery to reduce morbidity and mortality for the obese patient who is critically ill.

Taming the Flames: Targeting White Adipose Tissue Browning in Hypermetabolic Conditions

In this era of increased obesity and diabetes prevalence, the browning of white adipose tissue (WAT) has emerged as a promising therapeutic target to induce weight loss and improve insulin sensitivity in this population. The browning process entails a shift in the WAT from primarily storing excess energy to the dissipation of energy as heat. However, this idealistic view of WAT browning being the savior of the metabolic syndrome has been criticized by studies in burn and cancer patients that have shown browning to be detrimental rather than beneficial. In fact, in the context of hypermetabolic states, the browning of WAT has presented with substantial clinical adverse outcomes related to cachexia, hepatic steatosis, and muscle catabolism. Therefore, the previous thought construct of understanding browning as an all-beneficial physiologic event has now been met with skepticism. In this review, we focus on current knowledge of browning of WAT and its adverse metabolic alterations during hypermetabolic states. We also discuss the regulators and signaling pathways involved in the browning process and their potential for being targeted by new or existing drugs to inhibit or alleviate browning, potentially leading to decreased hypermetabolism and improved clinical outcomes. Lastly, the imminent clinical applications of pharmacological agents are explored in the perspective of attenuating WAT browning and its associated adverse side effects reported in burn patients.

Initial nutritional management during noninvasive ventilation and outcomes: a retrospective cohort study

Background

Patients starting noninvasive ventilation (NIV) to treat acute respiratory failure are often unable to eat and therefore remain in the fasting state or receive nutritional support. Maintaining a good nutritional status has been reported to improve patient outcomes. In the present study, our primary objective was to describe the nutritional management of patients starting first-line NIV, and our secondary objectives were to assess potential associations between nutritional management and outcomes.

Methods

Observational retrospective cohort study of a prospective database fed by 20 French intensive care units. Adult medical patients receiving NIV for more than 2 consecutive days were included and divided into four groups on the basis of nutritional support received during the first 2 days of NIV: no nutrition, enteral nutrition, parenteral nutrition only, and oral nutrition only.

Results

Of the 16,594 patients admitted during the study period, 1075 met the inclusion criteria; of these, 622 (57.9%) received no nutrition, 28 (2.6%) received enteral nutrition, 74 (6.9%) received parenteral nutrition only, and 351 (32.7%) received oral nutrition only. After adjustment for confounders, enteral nutrition (vs. no nutrition) was associated with higher 28-day mortality (adjusted HR, 2.3; 95% CI, 1.2–4.4) and invasive mechanical ventilation needs (adjusted HR, 2.1; 95% CI, 1.1–4.2), as well as with fewer ventilator-free days by day 28 (adjusted relative risk, 0.7; 95% CI, 0.5–0.9).

Conclusions

Nearly three-fifths of patients receiving NIV fasted for the first 2 days. Lack of feeding or underfeeding was not associated with mortality. The optimal route of nutrition for these patients needs to be investigated.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-017-1867-y) contains supplementary material, which is available to authorized users.

The P50 Research Center in Perioperative Sciences: How the investment by the National Institute of General Medical Sciences in team science has reduced postburn mortality

Since the inception of the P50 Research Center in Injury and Peri-operative Sciences (RCIPS) funding mechanism, the National Institute of General Medical Sciences has supported a team approach to science. Many advances in critical care, particularly burns, have been driven by RCIPS teams. In fact, burns that were fatal in the early 1970s, prior to the inception of the P50 RCIPS program, are now routinely survived as a result of the P50-funded research. The advances in clinical care that led to the reduction in postburn death were made by optimizing resuscitation, incorporating early excision and grafting, bolstering acute care including support for inhalation injury, modulating the hypermetabolic response, augmenting the immune response, incorporating aerobic exercise, and developing antiscarring strategies. The work of the Burn RCIPS programs advanced our understanding of the pathophysiologic response to burn injury. As a result, the effects of a large burn on all organ systems have been studied, leading to the discovery of persistent dysfunction, elucidation of the underlying molecular mechanisms, and identification of potential therapeutic targets. Survival and subsequent patient satisfaction with quality of life have increased. In this review article, we describe the contributions of the Galveston P50 RCIPS that have changed postburn care and have considerably reduced postburn mortality.

Nutrition and metabolism in burn patients

Severe burn causes significant metabolic derangements that make nutritional support uniquely important and challenging for burned patients. Burn injury causes a persistent and prolonged hypermetabolic state and increased catabolism that results in increased muscle wasting and cachexia. Metabolic rates of burn patients can surpass twice normal, and failure to fulfill these energy requirements causes impaired wound healing, organ dysfunction, and susceptibility to infection. Adequate assessment and provision of nutritional needs is imperative to care for these patients. There is no consensus regarding the optimal timing, route, amount, and composition of nutritional support for burn patients, but most clinicians advocate for early enteral nutrition with high-carbohydrate formulas.

Nutritional support must be individualized, monitored, and adjusted throughout recovery. Further investigation is needed regarding optimal nutritional support and accurate nutritional endpoints and goals.

Nutrition and metabolism in burn patients

Severe burn causes significant metabolic derangements that make nutritional support uniquely important and challenging for burned patients. Burn injury causes a persistent and prolonged hypermetabolic state and increased catabolism that results in increased muscle wasting and cachexia. Metabolic rates of burn patients can surpass twice normal, and failure to fulfill these energy requirements causes impaired wound healing, organ dysfunction, and susceptibility to infection. Adequate assessment and provision of nutritional needs is imperative to care for these patients. There is no consensus regarding the optimal timing, route, amount, and composition of nutritional support for burn patients, but most clinicians advocate for early enteral nutrition with high-carbohydrate formulas. Nutritional support must be individualized, monitored, and adjusted throughout recovery. Further investigation is needed regarding optimal nutritional support and accurate nutritional endpoints and goals.

Postburn Hypermetabolism: Past, Present, and Future

Hypermetabolism is the ubiquitous response to a severe burn injury, which was first described in the nineteenth century. Despite identification of important components of this complex response, hypermetabolism is still not well understood in its entirety. This article describes this incredibly fascinating response and the understanding we have gained over the past 100 years. Additionally, this article describes novel insights and delineates treatment options to modulate postburn hypermetabolism with the goal to improve outcomes of burn patients.

Burn injury induces histopathological changes and cell proliferation in liver of rats

AIM: To investigate effects of severe burn injury (BI) in rat liver through the histopathological and inflammatory markers analysis.

METHODS: Forty-two male Wistar rats were distributed into two groups, control (C) and subjected to scald BI (SBI). The animals were euthanized one, four and 14 d post sham or 45% of the total body surface BI. Liver fragments were submitted to histopathological, morphoquantitative (hepatocyte area and cell density), ciclooxigenase-2 (COX-2) immunoexpression, and gene expression [real-time polymerase chain reaction for tumor necrosis factor (TNF)-α, inducible nitric oxide synthase (iNOS) and caspase-3] methods.

RESULTS: Histopathological findings showed inflammatory process in all periods investigated and hepatocyte degeneration added to increased amount of connective tissue 14 d post injury. Hepatocyte area, the density of binucleated hepatocytes and density of sinusoidal cells of SBI groups were increased when compared with control. COX-2 immunoexpression was stronger in SBI groups. No differences were found in TNF-α, iNOS and caspase-3 gene expression.

CONCLUSION: BI induces histopathological changes, upregulation of COX-2 immunoexpression, and cell proliferation in liver of rats.

Nutrition and anabolic pharmacotherapies in the care of burn patients

Thermal injury is a devastating injury that results in a number of pathological alterations in almost every system in the body. Hypermetabolism, muscle wasting, depressed immunity, and impaired wound healing are all clinical features of burns. Failure to address each of these specific pathological alterations can lead to increased mortality. Nutrition supplementation has been recommended as a therapeutic tool to help attenuate the hypermetabolism and devastating catabolism evident following burn. Despite the wide consensus on the need of nutrition supplementation in burn patients, controversy exists with regard to the type and amount of nutrition recommended. Nutrition alone is also not enough in these patients to halt and reverse some of the damage done by the catabolic pathways activated following severe burn injury. This has led to the use of anabolic pharmacologic agents in conjunction with nutrition to help improve patient outcome following burn injury. In this review, we examine the relevant literature on nutrition after burn injury and its contribution to the attenuation of the postburn hypermetabolic response, impaired wound healing, and suppressed immunological responses. We also review the commonly used anabolic agents clinically in the care of burn patients. Finally, we provide nutrition and pharmacological recommendations gained from prospective trials, retrospective analyses, and expert opinions based on our practice at the Ross Tilley Burn Center in Toronto, Canada.

Metabolic and nutritional support of critically ill patients: consensus and controversies

The results of recent large-scale clinical trials have led us to review our understanding of the metabolic response to stress and the most appropriate means of managing nutrition in critically ill patients. This review presents an update in this field, identifying and discussing a number of areas for which consensus has been reached and others where controversy remains and presenting areas for future research. We discuss optimal calorie and protein intake, the incidence and management of re-feeding syndrome, the role of gastric residual volume monitoring, the place of supplemental parenteral nutrition when enteral feeding is deemed insufficient, the role of indirect calorimetry, and potential indications for several pharmaconutrients.

Endoplasmic reticulum stress in adipose tissue augments lipolysis

The endoplasmic reticulum (ER) is an organelle important for protein synthesis and folding, lipid synthesis and Ca²⁺ homoeostasis. Consequently, ER stress or dysfunction affects numerous cellular processes and has been implicated as a contributing factor in several pathophysiological conditions. Tunicamycin induces ER stress in various cell types in vitro as well as in vivo. In mice, a hallmark of tunicamycin administration is the development of fatty livers within 24–48 hrs accompanied by hepatic ER stress. We hypothesized that tunicamycin would induce ER stress in adipose tissue that would lead to increased lipolysis and subsequently to fatty infiltration of the liver and hepatomegaly. Our results show that intraperitoneal administration of tunicamycin rapidly induced an ER stress response in adipose tissue that correlated with increased circulating free fatty acids (FFAs) and glycerol along with decreased adipose tissue mass and lipid droplet size. Furthermore, we found that in addition to fatty infiltration of the liver as well as hepatomegaly, lipid accumulation was also present in the heart, skeletal muscle and kidney. To corroborate our findings to a clinical setting, we examined adipose tissue from burned patients where increases in lipolysis and the development of fatty livers have been well documented. We found that burned patients displayed significant ER stress within adipose tissue and that ER stress augments lipolysis in cultured human adipocytes. Our results indicate a possible role for ER stress induced lipolysis in adipose tissue as an underlying mechanism contributing to increases in circulating FFAs and fatty infiltration into other organs.

An alteration of the gut-liver axis drives pulmonary inflammation after intoxication and burn injury in mice

Approximately half of all adult burn patients are intoxicated at the time of their injury and have worse clinical outcomes than those without prior alcohol exposure. This study tested the hypothesis that intoxication alters the gut-liver axis, leading to increased pulmonary inflammation mediated by burn-induced IL-6 in the liver. C57BL/6 mice were given 1.2 g/kg ethanol 30 min prior to a 15% total body surface area burn. To restore gut barrier function, the specific myosin light chain kinase inhibitor membrane-permeant inhibitor of kinase (PIK), which we have demonstrated to reduce bacterial translocation from the gut, was administered 30 min after injury. Limiting bacterial translocation with PIK attenuated hepatic damage as measured by a 47% reduction in serum alanine aminotransferase (P < 0.05), as well as a 33% reduction in hepatic IL-6 mRNA expression (P < 0.05), compared with intoxicated and burn-injured mice without PIK. This mitigation of hepatic damage was associated with a 49% decline in pulmonary neutrophil infiltration (P < 0.05) and decreased alveolar wall thickening compared with matched controls. These results were reproduced by prophylactic reduction of the bacterial load in the intestines with oral antibiotics before intoxication and burn injury. Overall, these data suggest that the gut-liver axis is deranged when intoxication precedes burn injury and that limiting bacterial translocation in this setting attenuates hepatic damage and pulmonary inflammation.

Burns in children: standard and new treatments

Outcomes of patients with burns have improved substantially over the past two decades. Findings from a 2012 study in The Lancet showed that a burn size of more than 60% total body surface area burned (an increase from 40% a decade ago) is associated with risks and mortality. Similar data have been obtained in adults and elderly people who have been severely burned. We discuss recent and future developments in burn care to improve outcomes of children.

Association of postburn fatty acids and triglycerides with clinical outcome in severely burned children

CONTEXT

Free fatty acids (FFAs) and triglycerides (TGs) are altered postburn, but whether these alterations are associated with postburn outcomes is not clear.

OBJECTIVE

The aim of the present study was to analyze lipid metabolic profiles in pediatric burn patients and to correlate these profiles with patient outcomes and hospital courses.

DESIGN AND SETTING

We conducted a prospective cohort study at an academic pediatric hospital burn center.

PATIENTS

Our study included 219 pediatric burn patients.

MAIN OUTCOME MEASURES

Patients were stratified according to their plasma TG and FFA levels. Main patient outcomes, such as postburn morbidity and mortality, and clinical metabolic markers were analyzed.

RESULTS

All groups were similar in demographics and injury characteristics. Patients with elevated TGs had significantly worse clinical outcomes associated with increased acute-phase protein synthesis indicating augmented inflammation and hypermetabolism, whereas increased FFAs did not seem to profoundly alter postburn outcomes.

CONCLUSIONS

Elevated TGs, but not FFAs, postburn are associated with worsened organ function and clinical outcomes.

What, how, and how much should patients with burns be fed?

The hypermetabolic response to severe burn injury is characterized by hyperdynamic circulation and profound metabolic, physiologic, catabolic, and immune system derangements. Failure to satisfy overwhelming energy and protein requirements after, and during, severe burn injury results in multiorgan dysfunction, increased susceptibility to infection, and death. Attenuation of the hypermetabolic response by various pharmacologic modalities is emerging as an essential component of the management of patients with severe burn injury. This review focuses on the more recent advances in therapeutic strategies to attenuate the hypermetabolic response and its postburn-associated insulin resistance.

Long-term persistance of the pathophysiologic response to severe burn injury

Background

Main contributors to adverse outcomes in severely burned pediatric patients are profound and complex metabolic changes in response to the initial injury. It is currently unknown how long these conditions persist beyond the acute phase post-injury. The aim of the present study was to examine the persistence of abnormalities of various clinical parameters commonly utilized to assess the degree hypermetabolic and inflammatory alterations in severely burned children for up to three years post-burn to identify patient specific therapeutic needs and interventions.

Methodology/Principal Findings

Patients: Nine-hundred seventy-seven severely burned pediatric patients with burns over 30% of the total body surface admitted to our institution between 1998 and 2008 were enrolled in this study and compared to a cohort non-burned, non-injured children. Demographics and clinical outcomes, hypermetabolism, body composition, organ function, inflammatory and acute phase responses were determined at admission and subsequent regular intervals for up to 36 months post-burn. Statistical analysis was performed using One-way ANOVA, Student's t-test with Bonferroni correction where appropriate with significance accepted at p<0.05. Resting energy expenditure, body composition, metabolic markers, cardiac and organ function clearly demonstrated that burn caused profound alterations for up to three years post-burn demonstrating marked and prolonged hypermetabolism, p<0.05. Along with increased hypermetabolism, significant elevation of cortisol, catecholamines, cytokines, and acute phase proteins indicate that burn patients are in a hyperinflammatory state for up to three years post-burn p<0.05.

Conclusions

Severe burn injury leads to a much more profound and prolonged hypermetabolic and hyperinflammatory response than previously shown. Given the tremendous adverse events associated with the hypermetabolic and hyperinflamamtory responses, we now identified treatment needs for severely burned patients for a much more prolonged time.

Cytochrome P450-specific human PBPK/PD models for the organophosphorus pesticides: chlorpyrifos and parathion

Organophosphorus pesticides (OPs) remain a potential concern to human health because of their continuing use worldwide. Phosphororthioate OPs like chlorpyrifos and parathion are directly activated and detoxified by various cytochrome P450s (CYPs), with the primary CYPs involved being CYP2B6 and CYP2C19. The goal of the current study was to convert a previously reported human pharmacokinetic and pharmacodynamic (PBPK/PD) model for chlorpyrifos, that used chlorpyrifos metabolism parameters from rat liver, into a human CYP based/age-specific model using recombinant human CYP kinetic parameters (V(max), K(m)), hepatic CYP content and plasma binding measurements to estimate new values for acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibition and to use the model as a template for the development of a comparable parathion PBPK/PD model. The human CYP based/age-specific PBPK/PD models were used to simulate single oral exposures of adults (19 year old) and infants (1 year) to chlorpyrifos (10,000, 1000 and 100 μg/kg) or parathion (100, 25 and 5 μg/kg). Model simulations showed that there is an age dependency in the amount of blood cholinesterase inhibition observed, however additional age-dependent data are needed to further optimize age-specific human PBPK/PD modeling for these OP compounds. PBPK/PD model simulations estimated that a 4-fold increase or decrease in relative CYP2B6 and CYP2C19 content would produce a 9-22% inhibition in blood AChE activity following exposure of an adult to chlorpyrifos (1000 μg/kg). Similar model simulation produced an 18-22% inhibition in blood AChE activity following exposure of an adult to parathion (25 μg/kg). Individuals with greater CYP2B6 content and lower CYP2C19 content were predicted to be most sensitive to both OPs. Changes in hepatic CYP2B6 and CYP2C19 content had more of an influence on cholinesterase inhibition for exposures to chlorpyrifos than parathion, which agrees with previously reported literature that these CYPs are more reaction biased for desulfurization (activation) and dearylation (detoxification) of chlorpyrifos compared to parathion. The data presented here illustrate how PBPK/PD models with human enzyme-specific parameters can assist ongoing risk assessment efforts and aid in the identification of sensitive individuals and populations.

Association between dietary fat content and outcomes in pediatric burn patients

BACKGROUND

The aim of the study was to compare a low fat/high-carbohydrate diet and a high-fat diet on clinical outcomes by a retrospective cohort study.

METHODS

Nine hundred forty-four children with burns ≥ 40% of their total body surface area (TBSA) were divided into two groups: patients receiving Vivonex T.E.N. (low-fat/high-carbohydrate diet; n = 518) and patients receiving milk (high-fat diet; n = 426). Patient demographics, caloric intake, length of hospital stay, and incidence of sepsis, mortality, hepatic steatosis, and organomegaly at autopsy were determined.

RESULTS

Demographics and caloric intake were similar in both groups. Patients receiving Vivonex T.E.N. had shorter (intensive care unit) ICU stays (Vivonex T.E.N.: 31 ± 2 d; milk: 47 ± 2 d; P < 0.01), shorter ICU stay per % TBSA burn (Vivonex T.E.N.: 0.51 ± 0.02 d/%; milk: 0.77 ± 0.03 d/%; P < 0.01), lower incidence of sepsis (Vivonex T.E.N.: 11%; milk: 20%; P < 0.01), and lived significantly longer until death than those receiving milk (Vivonex T.E.N.: 20 ± 3 d; milk: 10 ± 2 d; P < 0.01). There was no difference in overall mortality between the two groups (Vivonex T.E.N.:15% versus milk: 13%; P < 0.9). Autopsies revealed decreased hepatic steatosis and decreased enlargement of kidney and spleen in patients receiving Vivonex T.E.N.

CONCLUSIONS

The period with a low-fat/high-carbohydrate diet was associated with lower LOS, decreased incidence of organomegaly, infection, and hepatic steatosis post-burn compared with the period when a high-fat diet was used. These associations indicate the benefit of high carbohydrate/low fat nutrition; however, the findings in these time periods can also be likely due to the multifactorial effects of advances in burn care. We believe that these results have some relevance because high fat is associated with poorer outcomes compared with low fat.

The hypermetabolic response to burn injury and interventions to modify this response

Severe burn injury is followed by a profound hypermetabolic response that persists up to 24 months after injury. It is mediated by up to 50-fold elevations in plasma catecholamines, cortisol, and inflammatory cells that lead to whole-body catabolism, elevated resting energy expenditures, and multiorgan dysfunction. All of these metabolic and physiologic derangements prevent full rehabilitation and acclimatization of burn survivors back into society. Modulation of the response by early excision and grafting of burn wounds, thermoregulation, early and continuous enteral feeding with high-protein high-carbohydrate feedings, and pharmacologic treatments have markedly decreased morbidity.

Ethanol potentiates the acute fatty infiltration of liver caused by burn injury: prevention by insulin treatment

Burn injury is a significant and severe representation of critical illness. Nearly, 50% of patients admitted to hospitals for burn injuries have detectable levels of ethanol in their circulations and these patients have poorer clinical outcomes than burned individuals without measurable circulating ethanol. We report here data on a clinically relevant form of hepatic injury, the development of microvesicular steatosis, in a murine model wherein animals were either given ethanol or saline, and were subjected to burn or sham injury. Because better glycemic control with insulin has been shown in clinical studies to impart major clinical benefit, an additional group of burn ethanol animals were treated with insulin. Insulin significantly reduced blood glucose in injured animals to levels no different from those seen in animals that were neither ethanol exposed nor burned. A single intraperitoneal injection of ethanol was insufficient to raise blood alanine aminotransferase (ALT), measured as an index of liver injury. However, burn injury led to significant increases in ALT at 24 and 48 hours, which had returned to preinjury levels by 7 days. This ALT rise was completely prevented with insulin treatment. A single injection of ethanol did not evoke increased microvesicular steatosis but did potentiate the ability of burn to do so at 24 hours after injury. The burn induced increase in microvesicular steatosis was also seen at 48 hours, but had subsided by 7 days. The increased microvesicular steatosis was prevented by insulin therapy. Thus, ethanol potentiates the ability of burn to cause acute liver injury, which is completely preventable by insulin therapy. These findings may have substantial clinical significance and suggest this model may be useful for the study of the mechanisms of hepatic injury as well as the mechanisms, probably multiple, of insulin action in this setting.

The hepatic response to thermal injury: is the liver important for postburn outcomes?

Thermal injury produces a profound hypermetabolic and hypercatabolic stress response characterized by increased endogenous glucose production via gluconeogenesis and glycogenolysis, lipolysis, and proteolysis. The liver is the central body organ involved in these metabolic responses. It is suggested that the liver, with its metabolic, inflammatory, immune, and acute phase functions, plays a pivotal role in patient survival and recovery by modulating multiple pathways following thermal injury. Studies have evaluated the role and function of the liver during the postburn response and showed that liver integrity and function are essential for survival, and that hepatic acute phase proteins are strong predictors for postburn survival. This review discusses these studies and delineates the pivotal role of the liver in patients following severe thermal injury.

Emergency treatment of severely burned pediatric patients: current therapeutic strategies

Burn trauma represents a devastating injury and remains as one of the leading causes of mortality and morbidity in children. Effective prevention strategies, advances in therapeutic techniques, based on an improved understanding of fluid resuscitation, appropriate infection control and improved treatment of inhalation injury, enhanced wound coverage, better nutritional regimens, advanced support of the hypermetabolic response to injury and improved glucose control, have significantly improved the clinical outcome of this unique patient population over the past years. This article aims to outline the current and emerging therapeutic strategies for the treatment of severely burned pediatric patients in the emergency department or initial phase of the intensive care unit.

Pathophysiologic response to severe burn injury

OBJECTIVE

To improve clinical outcome and to determine new treatment options, we studied the pathophysiologic response postburn in a large prospective, single center, clinical trial.

SUMMARY BACKGROUND DATA

A severe burn injury leads to marked hypermetabolism and catabolism, which are associated with morbidity and mortality. The underlying pathophysiology and the correlations between humoral changes and organ function have not been well delineated.

METHODS

Two hundred forty-two severely burned pediatric patients [>30% total body surface area (TBSA)], who received no anabolic drugs, were enrolled in this study. Demographics, clinical data, serum hormones, serum cytokine expression profile, organ function, hypermetabolism, muscle protein synthesis, incidence of wound infection sepsis, and body composition were obtained throughout acute hospital course.

RESULTS

Average age was 8 +/- 0.2 years, and average burn size was 56 +/- 1% TBSA with 43 +/- 1% third-degree TBSA. All patients were markedly hypermetabolic throughout acute hospital stay and had significant muscle protein loss as demonstrated by a negative muscle protein net balance (-0.05% +/- 0.007 nmol/100 mL leg/min) and loss of lean body mass (LBM) (-4.1% +/- 1.9%); P < 0.05. Patients lost 3% +/- 1% of their bone mineral content (BMC) and 2 +/- 1% of their bone mineral density (BMD). Serum proteome analysis demonstrated profound alterations immediately postburn, which remained abnormal throughout acute hospital stay; P < 0.05. Cardiac function was compromised immediately after burn and remained abnormal up to discharge; P < 0.05. Insulin resistance appeared during the first week postburn and persisted until discharge. Patients were hyperinflammatory with marked changes in IL-8, MCP-1, and IL-6, which were associated with 2.5 +/- 0.2 infections and 17% sepsis.

CONCLUSIONS

In this large prospective clinical trial, we delineated the complexity of the postburn pathophysiologic response and conclude that the postburn response is profound, occurring in a timely manner, with derangements that are greater and more protracted than previously thought.

Urinary cortisol and catecholamine excretion after burn injury in children

INTRODUCTION

A severe burn causes increased levels of urine cortisol and catecholamines. However, little is known about the magnitude of this increase or how and when the levels return to normal. The purpose of this study was to determine in a large clinical prospective trial the acute and long-term pattern of urine cortisol and catecholamine expression in severely burned children.

METHODS

Pediatric patients with burns greater than 40% total body surface area (TBSA), admitted to our unit over a 6-yr period, were included into the study. Clinical data including length of stay, number of operations, and duration and number of infections were determined. Patients had regular 24-h urine collections during their acute admission and reconstructive periods. Urine collections were analyzed for cortisol, epinephrine, and norepinephrine. Each urine cortisol was compared with age-adjusted reference ranges. Ninety-five percent confidence intervals and ANOVA analysis were used where appropriate.

RESULTS

Two hundred twelve patients were included in the study (75 females and 137 males), with a mean +/- sem TBSA of 58 +/- 1% (third-degree 45 +/- 2%) and mean age of 9 +/- 0.4 yr. Urinary cortisol levels were significantly increased (3- to 5-fold) up to 100 d after the burn and then approached normal levels (P < 0.05). The rise in urine cortisol was significantly higher in male than female patients (P < 0.05). Early hypercortisolemia was associated with increased duration of severe infection (P < 0.05). Persistent hypercortisolemia was associated with increases in both infection rates and duration of severe infection (P < 0.05). Urinary catecholamines showed a significant increase at 11-20 d after the burn (P < 0.05). Urinary norepinephrine levels were significantly increased up to 20 d and then returned to normal (P < 0.05).

CONCLUSIONS

Urinary levels of cortisol, epinephrine, and norepinephrine are significantly increased after a major burn. Early hypercortisolemia is associated with increased duration of severe infection. Persistent hypercortisolemia is associated with increases in both infection rates and duration of severe infection.

Combination of recombinant human growth hormone and propranolol decreases hypermetabolism and inflammation in severely burned children

OBJECTIVE

Recombinant human growth hormone (rhGH) is a salutary modulator of posttraumatic metabolic responses. However, rhGH administration is associated with deleterious side effects, such as hyperglycemia, increased free fatty acids, and triglycerides, which limit its use. Administration of beta-blocker attenuates cardiac work and resting energy expenditure after severe thermal injury and improves fat metabolism and insulin sensitivity. Therefore, the combination of rhGH plus propranolol appears ideal. The aim of the present study was to determine whether rhGH plus propranolol improves hypermetabolism and the inflammatory and acute phase response after severe burn without causing adverse side effects.

DESIGN

Prospective randomized control trial.

SETTING

Shriners Hospitals for Children.

PATIENTS

Fifteen pediatric patients with burns > 40% total body surface area, 0.1-16 yrs of age, admitted within 7 days after burn. Fifteen children were matched for burn size, age, gender, inhalation injury, and infection and served as controls.

INTERVENTIONS

Patients in the experimental group received rhGH (0.2 mg/kg/day) and propranolol (to decrease heart rate by 15%) for > or = 15 days.

MEASUREMENTS AND MAIN RESULTS

Outcome measurements included resting energy expenditure, body composition, acute phase proteins, and cytokines. Both cohorts were similar in age, burn size, gender, and accompanying injuries. Percent predicted resting energy expenditure significantly decreased in patients receiving rhGH/propranolol (Delta -5% +/- 8%) compared with controls (Delta +35% +/- 20%) (p < .05). rhGH/propranolol administration significantly decreased serum C-reactive protein, cortisone, aspartate aminotransferase, alanine aminotransferase, free fatty acids, interleukin-6, interleukin-8, and macrophage inflammatory protein-1beta when compared with controls, while growth hormone/propranolol increased serum insulin-like growth factor-I, insulin-like growth factor binding protein-3, growth hormone, prealbumin, and interleukin-7 when compared with placebo (p < .05).

CONCLUSIONS

rhGH in combination with propranolol attenuates hypermetabolism and inflammation without the adverse side effects found with rhGH therapy alone.

Postburn trauma insulin resistance and fat metabolism

Hyperglycemia and insulin resistance have long been recognized in severe burn patients. More recently, it has been observed that controlling hyperglycemia, or alleviating insulin resistance, is associated with improved outcomes. This has led to a renewed interest in the etiology of insulin resistance in this population. The postinjury hyperglycemic response appears to be associated with multiple metabolic abnormalities, such as elevated basal energy expenditure, increased protein catabolism, and, notably, significant alterations in fat metabolism. The synergy of all of the responses is not understood, although many studies have been conducted. In this article we will review the present understanding of the relationship between fat metabolism and insulin resistance posttrauma, and discuss some of the recent discoveries and potential therapeutic measures. We propose that the insulin resistance is likely related to the development of "ectopic" fat stores, i.e., triglyceride (TG) storage in sites such as the liver and muscle cells. Deposition of TG in ectopic sites is due to an increase in free fatty acid delivery secondary to catecholamine-induced lipolysis, in conjunction with decreased beta-oxidation within muscle and decreased hepatic secretion of fats. The resultant increases in intracellular TG or related lipid products may in turn contribute to alterations in insulin signaling.