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

Proteasome Inhibition After Burn Injury

The objective of this study was to assess the effects of proteasome inhibition on the development of burn-induced hypermetabolism. Rats underwent 30-40% total BSA scald burn or sham injury. The proteasome inhibitor bortezomib (0.1 mg/kg) or vehicle (n = 10) was administered i.p. 3× weekly starting at 2 hours (early bortezomib, n = 20) or 48 hours (late-bortezomib, n = 13) postburn. Body weights were determined weekly. Resting energy expenditures (REE) were measured at days 0 (baseline), 7, 14, 21, and 42 postburn. At day 42, blood and pectoral muscle were harvested. Routine blood chemistry parameters were analyzed. Proteasome content, proteasome peptidase activities, and ubiquitin-protein conjugates were measured in muscle extracts. As compared with sham-vehicle-treated animals, specific proteasome activities were increased after burn and vehicle treatment. Bortezomib treatment inhibited proteasome activities and increased ubiquitin-protein conjugates after sham and burn injury. Bortezomib treatment did not affect REE after sham procedure. REE significantly increased by 47% within 7 days and remained elevated until day 42 after burn and vehicle treatment. After early-bortezomib treatment, burn-induced increases in REE were delayed and significantly reduced by 42% at day 42, as compared with vehicle treatment. With late-bortezomib treatment, burn-induced increases in REE were also delayed but not attenuated at day 42. Mortality was 20% with vehicle, 65% (median survival time: 1.875 days) with early-bortezomib and 25% with late-bortezomib treatment after burns (P < .05 early-bortezomib vs vehicle and late-bortezomib). Proteasome inhibition delays development of burn-induced hypermetabolism. Although proteasome inhibition early after burn injury reduces the hypermetabolic response, it significantly increases early burn-associated mortality.

Burns: Pathophysiology of Systemic Complications and Current Management

As a result of many years of research, the intricate cellular mechanisms of burn injury are slowly becoming clear. Yet, knowledge of these cellular mechanisms and a multitude of resulting studies have often failed to translate into improved clinical treatment for burn injuries. Perhaps the most valuable information to date is the years of clinical experience and observations in the management and treatment of patients, which has contributed to a gradual improvement in reported outcomes of mortality. This review provides a discussion of the cellular mechanisms and pathways involved in burn injury, resultant systemic effects on organ systems, current management and treatment, and potential therapies that we may see implemented in the future.

Brown and beige adipose tissues: phenotype and metabolic potential in mice and men

With the recent rediscovery of brown fat in adult humans, our outlook on adipose tissue biology has undergone a paradigm shift. While we attempt to identify, recruit, and activate classic brown fat stores in humans, identification of beige fat has also raised the possibility of browning our white fat stores. Whether such transformation of human white fat depots can be achieved to enhance the whole body oxidative potential remains to be seen. Evidence to date, however, largely points toward a major oxidative role only for classic brown fat depots, at least in rodents. White fat stores seem to provide the main fuel for sustaining thermogenesis via lipolysis. Interestingly, molecular markers consistent with both classic brown and beige fat identity can be observed in human supraclavicular depot, thereby complicating the discussion on beige fat in humans. Here, we review the recent advances made in our understanding of brown and beige fat in humans and mice. We further provide an overview of their plausible physiological relevance to whole body energy metabolism.

Status and Challenges of Predicting and Diagnosing Sepsis in Burn Patients

Burns are a common form of trauma that account for more than 300,000 deaths each year worldwide. Survival rates have improved over the past decades because of improvements in nutritional and fluid support, burn wound care, and infection control practices. Death, however, remains unacceptably high. The primary cause of death has changed over the last decades from anoxic causes to now predominantly infections and sepsis. Sepsis and septic complications are not only major contributors to poor outcomes, but they further result in longer hospital stay and higher healthcare costs. Despite the importance of infections and sepsis, the diagnosis and prediction remain a major challenge. To date, no clear diagnostic criteria or predictive formula exist that can predict reliably the occurrence of sepsis and infections. This review will highlight and discuss current definitions and criteria for diagnosis as well as predictive biomarkers of sepsis in patients with burns. It will also present the diagnostic tools employed, such as procalcitonin, C-reactive protein, and cytokines. We will discuss the benefits and shortcomings of different treatment modalities in the context of sepsis prevention. Last, we identify new therapeutic strategies for sepsis prediction and present future considerations to prevent sepsis in patients with burns. Minimizing and preventing septic complications through early detection would significantly benefit patients and necessitate continued research to unravel new biomarkers and mechanisms. Subsequent studies need to take a fresh perspective and consider the implementation of patient-centered therapeutic strategies.

The impact of operative time and hypothermia in acute burn surgery

BACKGROUND

Prolonged operative time and intraoperative hypothermia are known to have deleterious effects on surgical outcomes. Although millions of burn injuries undergo operative treatment globally every year, there remains a paucity of evidence to guide perioperative practice in burn surgery. This study evaluated associations between hypothermia and operative time on post-operative complications in acute burn surgery.

METHOD

A historical cohort study from January 1, 2006 to October 31, 2015 was completed at an American Burn Association verified burn centre. 1111 consecutive patients undergoing acute burn surgery were included, and 2171 surgeries were analyzed. Primary outcomes included post-operative complications, defined a priori as either infectious or noninfectious. Statistical analysis was undertaken using a modified Poisson model for relative risk, adjusted for total body surface area, inhalation injury, co-morbidities, substance abuse, and age.

RESULTS

The mean operative time was 4.4h (SD 3.7-4.7h; range 0.58-11h), and 18.6% of patients became hypothermic intra-operatively. Operative time was independently associated with the incidence of hypothermia (p<0.05), and both infectious (RR1.5; 1.2-1.9, p<0.0004) and non-infectious complications (RR2.3; 1.3-4.1, p<0.0066). In patients with major burns (TBSA≥20%), hypothermia predisposed to infectious (RR1.3; 1.1-1.5, p<0.0017) and non-infectious complications (RR1.7; 1.2-2.5; p<0.0049). Risk stratification revealed that hypothermic patients with major burns undergoing prolonged surgery had an increased risk of both infectious (RR1.4; 1.1-1.7, p<0.0068) and non-infectious complications (RR1.8; 1.1-3.0, p<0.0132) when compared with those without these risk factors.

CONCLUSIONS

Patients who undergo prolonged surgeries and become hypothermic are more likely to develop complications. We therefore advocate for diligent adherence to strategies to prevent hypothermia and recommend limiting operative time in clinical circumstances where intraoperative measures are unlikely to adequately prevent hypothermia.

Toll-Like Receptor Signaling in Burn Wound Healing and Scarring

Significance: Damage-associated molecular patterns (DAMPs) and pathogen-associated molecular patterns (PAMPs) emanate from burn-injured tissue and enter systemic circulation. Locally and systemically, they activate pattern-recognition receptors, including toll-like receptors (TLRs), to stimulate cytokine secretion, which in the severest burns typically results in extreme systemic cytokine levels, a dysfunctioning immune system, infection, impaired healing, and excessive scarring. This system-wide disruption of homeostasis can advance to life-threatening, multiorgan dysfunction syndrome. Knowledge of DAMP- and PAMP-TLR signaling may lead to treatments that ameliorate local and systemic inflammation and reduce scarring and other burn injury sequela. Recent Advances: Many PAMPs and DAMPs, the TLRs they activate, and their downstream signaling molecules have been shown to contribute to local and systemic inflammation and tissue damage following burn injury. Critical Issues: Whether TLR-pathway-targeting treatments applied at different times postburn injury might improve scarring remains an open question. The evaluation of this question requires the use of appropriate preclinical and clinical burn models carried out until after mature scar has formed. Future Directions: After TLR-pathway-targeting treatments are evaluated in porcine burn wound models and their safety is demonstrated, they can be tested in proof-of-concept clinical burn wound models.

The biochemical alterations underlying post-burn hypermetabolism

A severe burn can trigger a hypermetabolic state which lasts for years following the injury, to the detriment of the patient. The drastic increase in metabolic demands during this phase renders it difficult to meet the body's nutritional requirements, thus increasing muscle, bone and adipose catabolism and predisposing the patient to a host of disorders such as multi-organ dysfunction and sepsis, or even death. Despite advances in burn care over the last 50 years, due to the multifactorial nature of the hypermetabolic phenomenon it is difficult if not impossible to precisely identify and pharmacologically modulate the biological mediators contributing to this substantial metabolic derangement. Here, we discuss biomarkers and molecules which play a role in the induction and mediation of the hypercatabolic condition post-thermal injury. Furthermore, this thorough review covers the development of the factors released after burns, how they induce cellular and metabolic dysfunction, and how these factors can be targeted for therapeutic interventions to restore a more physiological metabolic phenotype after severe thermal injuries. This article is part of a Special Issue entitled: Immune and Metabolic Alterations in Trauma and Sepsis edited by Dr. Raghavan Raju.

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.

Safety and effectiveness of propranolol in severely burned patients: systematic review and meta-analysis

BACKGROUND

The objective of this systematic review was to determine the effectiveness and safety of propranolol compared to placebo or usual care for improving clinical relevant outcomes in severely burned patients (TBSA >20%).

METHODS

Relevant articles from randomized controlled trials were identified by a literature search in MEDLINE, EMBASE, and CENTRAL. We included trials involving patients with a severe burn (>20% of total body surface area affected). Trials were eligible if they evaluated propranolol and compared to usual care or placebo. Two investigators independently assessed articles for inclusion and exclusion criteria and selected studies for the final analysis. We conducted a meta-analysis using a random-effects model.

RESULTS

We included ten studies in our systematic review. These studies randomized a total of 1236 participants. There were no significant differences between propranolol and placebo with respect to mortality (RD -0.02 [95% CI -0.06 to 0.02]), sepsis (RD -0.03 [95% CI -0.09 to 0.04]), and the overall hospital stay (MD -0.37 [-4.52 to 3.78]). Propranolol-treated adults had a decrease in requirements of blood transfusions (MD -185.64 [95% CI -331.06 to -40.43]) and a decreased heart rate (MD -26.85 [95% CI -39.95 to -13.75]).

CONCLUSIONS

Our analysis indicates that there were no differences in mortality or sepsis in severely burned patients treated with propranolol compared with those who had usual care or placebo. However, the use of propranolol in these patients resulted in lower requirements of blood transfusion and lower values of heart rate. The evidence synthesized in this systematic review is limited to conclude that propranolol reduces the length of hospital stay among severely burned patients. Future trials should assess the impact of propranolol on clinically relevant outcomes such as mortality and adverse events.

Thyroid Crisis in a Patient With Burn Injury

Thyroid crisis is an exacerbation of hyperthyroidism that results in severe systemic disturbances and could be fatal. Similarly, severe burn injury also has a hypermetabolic response as part of its presentation. When these two conditions are present concurrently, one must be cognizant that the patient requires urgent optimization of their hyperthyroid status before surgery, and continuous monitoring in an intensive care unit setting. We offer a systematic approach to managing these patients.

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.

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.

Hypermetabolism and hypercatabolism of skeletal muscle accompany mitochondrial stress following severe burn trauma

Burn trauma results in prolonged hypermetabolism and skeletal muscle wasting. How hypermetabolism contributes to muscle wasting in burn patients remains unknown. We hypothesized that oxidative stress, cytosolic protein degradation, and mitochondrial stress as a result of hypermetabolism contribute to muscle cachexia postburn. Patients (n = 14) with burns covering >30% of their total body surface area were studied. Controls (n = 13) were young healthy adults. We found that burn patients were profoundly hypermetabolic at both the skeletal muscle and systemic levels, indicating increased oxygen consumption by mitochondria. In skeletal muscle of burn patients, concurrent activation of mTORC1 signaling and elevation in the fractional synthetic rate paralleled increased levels of proteasomes and elevated fractional breakdown rate. Burn patients had greater levels of oxidative stress markers as well as higher expression of mtUPR-related genes and proteins, suggesting that burns increased mitochondrial stress and protein damage. Indeed, upregulation of cytoprotective genes suggests hypermetabolism-induced oxidative stress postburn. In parallel to mtUPR activation postburn, mitochondrial-specific proteases (LONP1 and CLPP) and mitochondrial translocases (TIM23, TIM17B, and TOM40) were upregulated, suggesting increased mitochondrial protein degradation and transport of preprotein, respectively. Our data demonstrate that proteolysis occurs in both the cytosolic and mitochondrial compartments of skeletal muscle in severely burned patients. Increased mitochondrial protein turnover may be associated with increased protein damage due to hypermetabolism-induced oxidative stress and activation of mtUPR. Our results suggest a novel role for the mitochondria in burn-induced cachexia.

Burn trauma disrupts circadian rhythms in rat liver

Circadian rhythms play an important role in maintaining homeostasis and solid organ function. The purpose of this study is to assess the implications of burn injury in rats on the underlying circadian patterns of gene expression in liver. Circadian-regulated genes and burn-induced genes were identified by applying consensus clustering methodology to temporally differentially expressed probe sets obtained from burn and sham-burn data sets. Of the liver specific genes which we hypothesize that exhibit circadian rhythmicity, 88% are not differentially expressed following the burn injury. Specifically, the vast majority of the circadian regulated-genes representing central carbon and nitrogen metabolism are "up-regulated" after the burn injury, indicating the onset of hypermetabolism. In addition, cell-cell junction and membrane structure related genes showing rhythmic behavior in the control group were not differentially expressed across time in the burn group, which could be an indication of hepatic damage due to the burn. Finally, the suppression of the immune function related genes is observed in the postburn phase, implying the severe "immunosuppression". Our results demonstrated that the short term response (24-h post injury) manifests a loss of circadian variability possibly compromising the host in terms of subsequent challenges.

A randomized controlled trial to compare the effects of liquid versus powdered recombinant human growth hormone in treating patients with severe burns

Recombinant human growth hormone (rhGH) promotes protein utilization and synthesis, and is widely used as a therapy to treat severe burns. The present randomized controlled trial evaluated the effects of different forms of rhGH on patients with severe burns. A total of 29 adult severe burns patients were enrolled between February 2009 and November 2011, and randomly assigned to either treatment group (T, liquid rhGH) or control group (C, powder rhGH). From days 5 to 7 following the infliction of burns, both patient groups received rhGH at 0.067 mg/kg/d, once for 10 days. Median serum pre-albumin levels increased in both groups following treatment, the elevation from baseline was significantly higher in the T group on day 10 compared to the C group (88 mg/l vs. 65 mg/l, P=0.046). C-reactive protein, fasting plasma glucose and body weight decreased in both groups. Body weight was significantly lower in the T compared to the C group at baseline, Day 5 and Day 10 (P=0.046, P=0.018 and P=0.006, respectively), however the decrease from baseline levels were not significantly different. Wound healing time was similar between groups (P=0.270). In conclusion the early use of liquid rather than powder rhGH may be more beneficial for treating adult patients with severe burns.

Seawater Immersion Aggravates Burn Injury Causing Severe Blood Coagulation Dysfunction

This study aimed to investigate the endothelial function in a canine model of burn injury combined with seawater immersion. The model of burn injury was established. The dogs were randomly divided into four groups including dogs with burn injury (B group), or burn injury combined with seawater immersion (BI group), or only immersion in seawater (I group), or control animals with no injury or immersion (C group). The circulating endothelial cell (CEC) count and coagulation-fibrinolysis parameters were measured. The CEC count in B group increased at 4 h, 7 h, and 10 h after injury and then reduced, whereas it continuously increased to a greater extent in BI group (P < 0.05). The von Willebrand factor (vWF) activity, plasminogen activator inhibitor (PAI-1), and the ratio of thromboxane B2 (TXB₂) to 6-keto-prostaglandin F1α (6-K-PGF_1α) in BI group had a marked increase after injury, and the tissue-type plasminogen activator (tPA) in the BI group decreased. Microscope observations revealed thrombus formation in lungs of the animals in BI group, but not in C, I, or B groups. Burn injury causes endothelial dysfunction, and seawater immersion lastingly aggravates this injury, leading to a higher risk of developing thrombosis.

Long term mortality in a population-based cohort of adolescents, and young and middle-aged adults with burn injury in Western Australia: A 33-year study

BACKGROUND

Advances in the treatment and management of burn patients over the past decades have resulted in a decline of in-hospital mortality rates. Current estimates of burn-related mortality are usually in the context of deaths occurring during the admission or within a short time period after the incident burn. Limited data are available that examine long term mortality after burn injury. This study aimed to assess the impact of burn injury on long-term mortality and quantify any increased risk of death attributable to burn injury.

METHODS

A population-based cohort study of persons 15-44 years of age hospitalised for burn injury (n=14,559) in Western Australia (1980-2012) and a matched non-injured comparison group (n=56,822) using linked health administrative data was used. Hospital morbidity and death data were obtained from the Western Australian Hospital Morbidity Data System and Death Register. De-identified extraction of all linked hospital morbidity and death records for the period 1980-2012 were provided by the Western Australian Data Linkage System. Survival analysis was conducted using the Kaplan-Meier method and Cox proportional hazards modelling.

RESULTS

The adjusted all-cause Mortality Rate Ratio (MRR) for burn injury was 1.8 (95%CI: 1.7-2.0); those with burn injury had a 1.8 times greater rate of mortality than those with no injury. The index burn injury was estimated to account for 44% of all recorded deaths in the burn injury cohort during the study period after discharge. Increased risk of mortality was observed for both severe (MRR, 95%CI: 1.9, 1.3-2.9) and minor (MRR, 95%CI: 2.5, 2.2-3.0) burns.

CONCLUSIONS

An increased risk of long-term all-cause mortality is associated with both minor and severe burn injury. Estimates of total mortality burden based on the early in-patient period alone, significantly underestimates the true burden of burn injury in adolescents, and young and middle aged adults. These results have significant implications for burn injury prevention.

Palmitate differentially regulates the polarization of differentiating and differentiated macrophages

The tissue accumulation of M1 macrophages in patients with metabolic diseases such as obesity and type 2 diabetes mellitus has been well-documented. Interestingly, it is an accumulation of M2 macrophages that is observed in the adipose, liver and lung tissues, as well as in the circulation, of patients who have had major traumas such as a burn injury or sepsis; however, the trigger for the M2 polarization observed in these patients has not yet been identified. In the current study, we explored the effects of chronic palmitate and high glucose treatment on macrophage differentiation and function in murine bone-marrow-derived macrophages. We found that chronic treatment with palmitate decreased phagocytosis and HLA-DR expression in addition to inhibiting the production of pro-inflammatory cytokines. Chronic palmitate treatment of bone marrows also led to M2 polarization, which correlated with the activation of the peroxisome proliferator-activated receptor-γ signalling pathway. Furthermore, we found that chronic palmitate treatment increased the expression of multiple endoplasmic reticulum (ER) stress markers, including binding immunoglobulin protein. Preconditioning with the universal ER stress inhibitor 4-phenylbutyrate attenuated ER stress signalling and neutralized the effect of palmitate, inducing a pro-inflammatory phenotype. We confirmed these results in differentiating human macrophages, showing an anti-inflammatory response to chronic palmitate exposure. Though alone it did not promote M2 polarization, hyperglycaemia exacerbated the effects of palmitate. These findings suggest that the dominant accumulation of M2 in adipose tissue and liver in patients with critical illness may be a result of hyperlipidaemia and hyperglycaemia, both components of the hypermetabolism observed in critically ill patients.

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.

Burn wound healing and treatment: review and advancements

Burns are a prevalent and burdensome critical care problem. The priorities of specialized facilities focus on stabilizing the patient, preventing infection, and optimizing functional recovery. Research on burns has generated sustained interest over the past few decades, and several important advancements have resulted in more effective patient stabilization and decreased mortality, especially among young patients and those with burns of intermediate extent. However, for the intensivist, challenges often exist that complicate patient support and stabilization. Furthermore, burn wounds are complex and can present unique difficulties that require late intervention or life-long rehabilitation. In addition to improvements in patient stabilization and care, research in burn wound care has yielded advancements that will continue to improve functional recovery. This article reviews recent advancements in the care of burn patients with a focus on the pathophysiology and treatment of burn wounds.

Long-term mortality among older adults with burn injury: a population-based study in Australia

OBJECTIVE

To assess if burn injury in older adults is associated with changes in long-term all-cause mortality and to estimate the increased risk of death attributable to burn injury.

METHODS

We conducted a population-based matched longitudinal study - based on administrative data from Western Australia's hospital morbidity data system and death register. A cohort of 6014 individuals who were aged at least 45 years when hospitalized for a first burn injury in 1980-2012 was identified. A non-injury comparison cohort, randomly selected from Western Australia's electoral roll (n = 25 759), was matched to the patients. We used Kaplan-Meier plots and Cox proportional hazards regression to analyse the data and generated mortality rate ratios and attributable risk percentages.

FINDINGS

For those hospitalized with burns, 180 (3%) died in hospital and 2498 (42%) died after discharge. Individuals with burn injury had a 1.4-fold greater mortality rate than those with no injury (95% confidence interval, CI: 1.3-1.5). In this cohort, the long-term mortality attributable to burn injury was 29%. Mortality risk was increased by both severe and minor burns, with adjusted mortality rate ratios of 1.3 (95% CI: 1.1-1.9) and 2.1 (95% CI: 1.9-2.3), respectively.

CONCLUSION

Burn injury is associated with increased long-term mortality. In our study population, sole reliance on data on in-hospital deaths would lead to an underestimate of the true mortality burden associated with burn injury.

Activities of nonlysosomal proteolytic systems in skeletal and cardiac muscle during burn-induced hypermetabolism

The aim of this study was to assess the activity of nonlysosomal proteolytic systems in skeletal and cardiac muscle during burn-induced hypermetabolism (BHM) in rats. Rats underwent 30% TBSA scald burn or sham injury and were observed for up to 42 days. Body weights and resting energy expenditures were determined weekly. Skeletal (soleus/pectoral) muscle and hearts were harvested on days 0 (=control), 7, 14, 21, and 42 after burn. Calpain, caspase-1, caspase-3/7, caspase-6, caspase-8, caspase-9, and proteasome peptidase activities were measured in tissue extracts. Hypermetabolism developed within 3 weeks after burns, as documented by increased resting energy expenditures and decreased body weights on postburn days 21 to 42 (P < 0.05 vs control). Calpain activities did not show significant alterations. Pan caspase activities increased by time and were significantly increased in skeletal and cardiac muscle extracts during hypermetabolism. Although increases in caspase-1, caspase-8, and caspase-9 activities were predominantly responsible for elevated pan caspase activities in skeletal muscle, increases in caspase-6 activities dominated in the heart. Proteasome peptidase activities in skeletal muscle extracts were not significantly altered. Proteasome peptidase activities in heart extracts increased time dependently and were significantly increased during BHM. Activation of caspase cascades during BHM constitutes a uniform response in skeletal and cardiac muscle and may contribute to enhanced metabolic protein turnover. Activation of myocardial proteasome activities may reflect persistent cardiac stress. Further exploration of caspase cascades and the proteasome as therapeutic targets to influence long-term consequences of BHM appears justified.

Mortality after burn injury in children: a 33-year population-based study

OBJECTIVE

To assess the impact of burn injury sustained during childhood on long-term mortality and to quantify any increased risk of death attributable to burn injury.

METHODS

A population-based cohort study of children younger than 15 years hospitalized for burn injury in Western Australia (1980-2012) and a matched noninjured comparison group. Deidentified extraction of linked hospital morbidity and death records for the period 1980-2012 were provided by the Western Australian Data Linkage System. An inception cohort (1980-2012) of burn cases younger than 15 years of age when hospitalized for a first burn injury (n = 10,426) and a frequency matched noninjured comparison cohort (n = 40,818) were identified. Survival analysis was conducted by using the Kaplan-Meier method and Cox proportional hazards regression. Mortality rate ratios and attributable risk percent adjusted for sociodemographic and preexisting heath factors were generated.

RESULTS

The median follow-up time for the pediatric burn cohort was 18.1 years after discharge. The adjusted all-cause mortality rate ratios for burn injury was 1.6 (95% confidence interval: 1.3-2.0); children with burn injury had a 1.6 times greater rate of mortality than those with no injury. The index burn injury was estimated to account for 38% (attributable risk percent) of all recorded deaths in the burn injury cohort during the study period.

CONCLUSIONS

Burn injury sustained by children is associated with an increased risk of long-term all-cause mortality. Estimates of the total mortality burden based on in-hospital deaths alone underestimates the true burden from burn injury.

Alcohol's Burden on Immunity Following Burn, Hemorrhagic Shock, or Traumatic Brain Injury

Alcohol consumption contributes to increased incidence and severity of traumatic injury. Compared with patients who do not consume alcohol, alcohol-consuming patients have higher rates of long-term morbidity and mortality during recovery from injury. This can be attributed in part to an impaired immune response in individuals who consume alcohol. Acute and chronic alcohol use can affect both the innate and adaptive immune defense responses within multiple organ systems; the combination of alcohol use and injury results in increased susceptibility to bacterial and viral pathogens. This review examines the major deleterious effects of alcohol on immunity following tissue damage or traumatic injury, with a focus on alcohol's influence on the ability of the immune and major organ systems to fight disease and to repair damaged tissues following injury.

Energy expenditure: how much does it matter in infant and pediatric chronic disorders?

A sound understanding of energy needs during chronic illness is necessary to avoid imbalances in energy intake and requirements. Failure to accurately estimate energy needs results in both underfeeding and overfeeding in chronically ill children. Suboptimal energy and protein intake may lead to deterioration in body composition, particularly lean body mass loss, which eventually impacts functional outcomes in these vulnerable groups. Furthermore, infants and children with chronic illnesses have a high prevalence of malnutrition and can ill afford further nutritional deterioration from suboptimal nutrient delivery. On the other hand, unintended delivery of excessive energy in patients with chronic respiratory insufficiency results in increased respiratory burden and poor outcomes. Hence, awareness of the energy requirements and attention to energy and protein balance are important when caring for children with chronic illnesses. The basic concepts of the metabolic stress response, measurement of energy expenditure, and the impact of energy imbalance on clinical outcomes in children with chronic illness are reviewed.

The effect of dietary intake of antioxidant micronutrients on burn wound healing: a study in a tertiary health institution in a developing country

Background

Burn injury results in emotional stress affecting dietary intake and antioxidant micronutrient intake, which is known to have effects on recovery outcomes. The study aimed to assess dietary intake of antioxidant micronutrients and recovery outcomes of burn patients.

Methods

Questionnaires were administered to 40 burn patients at Komfo Anokye Teaching Hospital (Ghana) from January 1, 2014 to May 30, 2014. The data taken include anthropometric measurements and dietary assessment. Their nutrient intakes were assessed with the Nutrient Analysis Template. The average intakes were compared to the recommended daily allowance. Assessment of recovery was based on records of wound healing assessments and infection rates from the health practitioners.

Results

A cross-sectional study of 40 patients revealed an average total burn surface area (TBSA) of 31.4 %, where 70.0, 35.0, 75.0, 52.5, 12.5 and 32.5 % patients were deficient in vitamins A, C and E, zinc, copper and selenium, respectively and adequate amounts of vitamin C intake were related with significantly better wound healing progress. Positive wound healing outcomes were observed for patients with adequate vitamins A and E and zinc intake. Less infection presented among patients with adequate amount of vitamins A and C and zinc, but this was not observed for patients with adequate vitamin E, copper and selenium.

Conclusions

Most burn patients did not meet their dietary requirements for antioxidant micronutrients and this was due to meals not tailored to suit individual requirements. Adequacy of the antioxidants especially vitamin C resulted in positive wound healing outcomes. Hence, there is need for planned well-balanced meals of high vitamin C.

A comparison of Biobrane™ and cadaveric allograft for temporizing the acute burn wound: Cost and procedural time

INTRODUCTION

In many circumstances early burn excision and autografting is unsafe or even impossible. In these situations, skin substitute dressings can be utilized for temporary wound coverage. Two commonly used dressings for this purpose are cadaveric allograft and Biobrane™.

MATERIALS AND METHODS

Five year retrospective cohort study evaluating upper extremity burns treated with temporary wound coverage (Biobrane™ or allograft). The primary outcome was to determine the impact choice of wound coverage had on operative time and cost. The secondary outcome was the need for revision of upper extremity debridement prior to definitive autografting.

RESULTS

45 patients were included in this study: 15 treated with cadaveric allograft and 30 treated with Biobrane™ skin substitute. Biobrane™ had a significantly lower procedure time (21.12 vs. 54.78 min per %TBSA excised, p=0.02) and cost (1.30 vs. 2.35 dollars per minute per %TBSA excised, p=0.002). Both techniques resulted in 2 revisions due to complications.

CONCLUSION

Biobrane™ is superior to cadaveric allograft as a temporizing skin substitute in the acute burn wound, both in terms of procedure time and associated cost. We believe that this is largely due to the relative ease of application of Biobrane™. Furthermore, given its unique characteristics, Biobrane™ may serve as a triage and transport option for severe burns in the military and mass casualty settings.

Establishment and assessment of new formulas for energy consumption estimation in adult burn patients

OBJECTIVE

An accurate knowledge of energy consumption in burn patients is a prerequisite for rational nutrition therapy. This study sought to create a formula that accounts for the metabolic characteristics of adult burn patients to accurately estimate energy consumption of patients with different areas and extents of burn and at different times after injury.

METHODS

Resting energy expenditure (REE) data on 66 burn patients, with total body surface area (TBSA) of burns ranging from 4% to 96%, were evaluated at different times after injury. REE values were determined in patients using indirect calorimetry at days 1, 2, 3, 7, 14, 21, and 28 after injury. We then constructed a mathematical model of REE changes post-burn. Next, established two new formulas (one non-linear and the other linear) for energy consumption estimation using model-based analytical solution and regression analysis. The new formulas were compared with measured REE and commonly used formulas including those of Carlson, Xie, Curreri, and Milner to determine accuracy and reliability.

RESULTS

Comparative analysis showed that the new formulas offered significantly higher accuracy and reliability than the Milner formula, which is considered the most accurate of commonly used burn energy consumption estimate formulas. The accuracy of the new nonlinear formula (94.29%) and that of the linear formula (91.43%) were significantly higher than that of Milner formula (72.86%) when compared to measured REE (χ2  =  11.706, P  =  0.001; χ2  =  8.230, P  =  0.004, respectively). The reliabilities of the new estimation formulas were both 100% and that of Milner formula was 74.24% (χ2  =  19.513, P  =  0.000).

CONCLUSION

The new formulas constructed in this study provide reliable simulation of the impact of the degree of burn and post-burn days on energy consumption and offer notably higher accuracy and reliability than other formulas. These formulas will help determine nutritional needs of burn patients.

TRIAL REGISTRATION

The study was registered on Chinese Clinical Trial Registry as ChiCTR-TRC-13003806.

Use of 1H-nuclear magnetic resonance to screen a set of biomarkers for monitoring metabolic disturbances in severe burn patients

Introduction

To establish a plasma metabolomics fingerprint spectrum for severe burn patients and to use it to identify a set of biomarkers that could be used for clinical monitoring.

Methods

Twenty-one severe burn patients and three healthy control individuals were enrolled in this study, and the plasma samples from patients and healthy individuals were collected for nuclear magnetic resonance (NMR) measurements. The NMR spectra were analyzed using principal component analysis (PCA) and partial least squares (PLS) in order to establish the metabolomics fingerprint representing the changes in metabolism and to select the major biomarkers.

Results

NMR spectra of the plasma samples showed significant differences between burn patients and healthy individuals. Using metabolomics techniques, we found an Eigen-metabolome that consists of 12 metabolites, which are regulated by 103 enzymes in a global metabolic network. Among these metabolites, α-ketoisovaleric acid, 3-methylhistidine, and β-hydroxybutyric acid were the most important biomarkers that were significantly increased during the early stage of burn injury. These results suggest that the mitochondrial damage and carbohydrate, protein and fatty acid metabolism disturbances occur after burn injury. Our analysis also show that histone deacetylases, which are protein transcription suppressors, were remarkably increased and indicate that protein transcription was inhibited and anabolism was restrained during the early stage of burn injury.

Conclusions

Metabolomics techniques based on NMR can be used to monitor metabolism in severe burn patients. Our study demonstrates that integrated ¹H-NMR metabolome and global metabolic network analysis is useful for visualizing complex metabolic disturbances after severe burn injury and may provide a new quantitative injury severity evaluation for future clinical use.

Trial registration

Chinese Clinical Trial Registry ChiCTR-OCC-12002145. Registered 25 April 2012.

Leukocyte infiltration and activation of the NLRP3 inflammasome in white adipose tissue following thermal injury

OBJECTIVES

Severe thermal injury is associated with extreme and prolonged inflammatory and hypermetabolic responses, resulting in significant catabolism that delays recovery or even leads to multiple organ failure and death. Burned patients exhibit many symptoms of stress-induced diabetes, including hyperglycemia, hyperinsulinemia, and hyperlipidemia. Recently, the nucleotide-binding domain, leucine-rich family (NLR), pyrin-containing 3 (NLRP3) inflammasome has received much attention as the sensor of endogenous "danger signals" and mediator of "sterile inflammation" in type II diabetes. Therefore, we investigated whether the NLRP3 inflammasome is activated in the adipose tissue of burned patients, as we hypothesize that, similar to the scenario observed in chronic diabetes, the cytokines produced by the inflammasome mediate insulin resistance and metabolic dysfunction.

DESIGN

Prospective cohort study.

SETTING

Ross Tilley Burn Centre & Sunnybrook Research Institute.

PATIENTS

We enrolled 76 patients with burn sizes ranging from 1% to 70% total body surface area. All severely burned patients exhibited burn-induced insulin resistance and hyperglycemia.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We examined the adipose tissue of control and burned patients and found, via flow cytometry and gene expression studies, increased infiltration of leukocytes-especially macrophages-and evidence of inflammasome priming and activation. Furthermore, we observed increased levels of interleukin-1β in the plasma of burned patients when compared to controls.

CONCLUSIONS

In summary, our study is the first to show activation of the inflammasome in burned humans, and our results provide impetus for further investigation of the role of the inflammasome in burn-induced hypermetabolism and, potentially, developing novel therapies targeting this protein complex for the treatment of stress-induced diabetes.

Animal models in burn research

Burn injury is a severe form of trauma affecting more than 2 million people in North America each year. Burn trauma is not a single pathophysiological event but a devastating injury that causes structural and functional deficits in numerous organ systems. Due to its complexity and the involvement of multiple organs, in vitro experiments cannot capture this complexity nor address the pathophysiology. In the past two decades, a number of burn animal models have been developed to replicate the various aspects of burn injury, to elucidate the pathophysiology, and to explore potential treatment interventions. Understanding the advantages and limitations of these animal models is essential for the design and development of treatments that are clinically relevant to humans. This review aims to highlight the common animal models of burn injury in order to provide investigators with a better understanding of the benefits and limitations of these models for translational applications. While many animal models of burn exist, we limit our discussion to the skin healing of mouse, rat, and pig. Additionally, we briefly explain hypermetabolic characteristics of burn injury and the animal model utilized to study this phenomena. Finally, we discuss the economic costs associated with each of these models in order to guide decisions of choosing the appropriate animal model for burn research.

Burn injury, gender and cancer risk: population-based cohort study using data from Scotland and Western Australia

OBJECTIVE

To investigate the risk of cancer and potential gender effects in persons hospitalised with burn injury.

DESIGN

Population-based retrospective cohort study using record-linkage systems in Scotland and Western Australia.

PARTICIPANTS

Records of 37 890 and 23 450 persons admitted with a burn injury in Scotland and Western Australia, respectively, from 1983 to 2008. Deidentified extraction of all linked hospital morbidity records, mortality and cancer records were provided by the Information Service Division Scotland and the Western Australian Data Linkage Service.

MAIN OUTCOME MEASURES

Total and gender-specific number of observed and expected cases of total ('all sites') and site-specific cancers and standardised incidence ratios (SIRs).

RESULTS

From 1983 to 2008, for female burn survivors, there was a greater number of observed versus expected notifications of total cancer with 1011 (SIR, 95% CI 1.3, 1.2 to 1.4) and 244 (SIR, 95% CI 1.12, 1.05 to 1.30), respectively, for Scotland and Western Australia. No statistically significant difference in total cancer risk was found for males. Significant excesses in observed cancers among burn survivors (combined gender) in Scotland and Western Australian were found for buccal cavity, liver, larynx and respiratory tract and for cancers of the female genital tract.

CONCLUSIONS

Results from the Scotland data confirmed the increased risk of total ('all sites') cancer previously observed among female burn survivors in Western Australia. The gender dimorphism observed in this study may be related to the role of gender in the immune response to burn injury. More research is required to understand the underlying mechanism(s) that may link burn injury with an increased risk of some cancers.

Medical management of paediatric burn injuries: best practice part 2

Burns remain a leading cause of injury in the paediatric population in Australia despite efforts in prevention. Advances in surgical management include novel debridement methods and blood conserving techniques. Patients with severe burns (>20%) remain significantly more complex to manage as a result of extensive alterations in metabolic processes. There appears increasing evidence to support the use of pharmacological modulators of the hyper-metabolic state in these patients. The management of a child with burns involves acute, subacute and long-term planning. This holistic approach seems optimally co-ordinated by a Burns Unit in which each discipline required to provide care to these children in order to achieve optimal outcomes is represented.

XBP-1s is linked to suppressed gluconeogenesis in the Ebb phase of burn injury

The first 24 h following burn injury is known as the ebb phase and is characterized by a depressed metabolic rate. While the postburn ebb phase has been well described, the molecular mechanisms underlying this response are poorly understood. The endoplasmic reticulum (ER) regulates metabolic rate by maintaining glucose homeostasis through the hepatic ER stress response. We have shown that burn injury leads to ER stress in the liver during the first 24 h following thermal injury. However, whether ER stress is linked to the metabolic responses during the ebb phase of burn injury is poorly understood. Here, we show in an animal model that burn induces activation of activating transcription factor 6 (ATF6) and inositol requiring enzyme-1 (IRE-1) and this leads to increased expression of spliced X-box binding protein-1 (XBP-1s) messenger ribonucleic acid (mRNA) during the ebb phase. This is associated with increased expression of XBP-1 target genes and downregulation of the key gluconeogenic enzyme glucose-6-phosphatase (G6Pase). We conclude that upregulation of the ER stress response after burn injury is linked to attenuated gluconeogenesis and sustained glucose tolerance in the postburn ebb phase.

Skeletal muscle satellite cell activation following cutaneous burn in rats

BACKGROUND

Cutaneous burn distant from skeletal muscles induces atrophy; however, its effect on muscle stem cells resident in skeletal muscle (satellite cells) distal to burn is not known.

METHODS

Satellite cell activation was measured in predominantly fast-twitch [tibialis anterior, extensor digitorum longus (EDL), plantaris, and gastrocnemius] and slow-twitch (soleus) muscles of rats that received either 40% total body surface area full-thickness scald burn or sham burn to the trunk area by determining bromodeoxyuridine incorporation, MyoD, and Pax7 immunohistochemistry in vivo ≤48 h after burn. To determine the effects of circulating factors on satellite cell activation, satellite cell cultures were treated with serum from sham or burn rats.

RESULTS

In vivo activation of satellite cells was increased in fast muscles isolated from burn as compared to sham animals, whereas a significant response was not seen in slow muscles. Serum taken from animals in the burn group increased the activation of satellite cells isolated from both sham and burn animals in vitro, suggesting that circulating factors have the potential to increase satellite cell activation following burn.

CONCLUSIONS

Increases in satellite cell activation in muscles distal to burn are fiber-type-dependent, and circulating factors may play a role in the activation of satellite cells following burn. A better understanding of the impact of burn on satellite cell functionality will allow us to identify the cellular mechanisms of long-term muscle atrophy.

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.

Burns: where are we standing with propranolol, oxandrolone, recombinant human growth hormone, and the new incretin analogs?

PURPOSE OF REVIEW

The hypermetabolic response in critically ill patients is characterized by hyperdynamic circulatory, physiologic, catabolic and immune system responses. Failure to satisfy overwhelming energy and protein requirements after, and during critical illness, 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 severe burn patients. This review focuses on the more recent advances in therapeutic strategies to attenuate the hypermetabolic response and its associated insulin resistance postburn.

RECENT FINDINGS

At present, beta-adrenergic blockade with propranolol represents probably the most efficacious anticatabolic therapy in the treatment of burns. Other pharmacological strategies include growth hormone, insulin-like growth factor, oxandrolone and intensive insulin therapy.

SUMMARY

Novel approaches to the management of critical illness by judicious glucose control and the use of pharmacologic modulators to the hypercatabolic response to critical illness have emerged. Investigation of alternative strategies, including the use of metformin, glucagon-like-peptide-1 and the PPAR-γ agonists are under current investigation.

Burns: learning from the past in order to be fit for the future

Many advances have been made in the understanding and treatment of burns. Advances in burn surgery and critical care have decreased mortality and morbidity. Survival from severe burns is no longer the exception, but unfortunately death still occurs. Williams and colleagues have determined in their recent paper the predominant causes of death in order to develop new treatment avenues and future trajectories suitable to increase survival and overall outcome. A lot of burn deaths may be preventable with better airway management and a more precise and adequate volume management, but the leading cause of death in patients suffering from severe burns, which has to be faced, is sepsis. Sepsis due to multidrug-resistant organisms will continue to impede efforts to increase survival, and new strategies that go beyond the surgical and clinical techniques, which are already implemented, have to be developed in order to fight these organisms and their related complications.