Persistence of muscle catabolism after severe burn

Predictive Value of IL-8 for Sepsis and Severe Infections After Burn Injury: A Clinical Study

The inflammatory response induced by burn injury contributes to increased incidence of infections, sepsis, organ failure, and mortality. Thus, monitoring postburn inflammation is of paramount importance but, so far, there are no reliable biomarkers available to monitor and/or predict infectious complications after burn. As interleukin 8 (IL-8) is a major mediator for inflammatory responses, the aim of our study was to determine whether IL-8 expression can be used to predict postburn sepsis, infections, and mortality. Plasma cytokines, acute-phase proteins, constitutive proteins, and hormones were analyzed during the first 60 days after injury from 468 pediatric burn patients. Demographics and clinical outcome variables (length of stay, infection, sepsis, multiorgan failure [MOF], and mortality) were recorded. A cutoff level for IL-8 was determined using receiver operating characteristic analysis. Statistical significance is set at P < 0.05. Receiver operating characteristic analysis identified a cutoff level of 234 pg/mL for IL-8 for survival. Patients were grouped according to their average IL-8 levels relative to this cutoff and stratified into high (H) (n = 133) and low (L) (n = 335) groups. In the L group, regression analysis revealed a significant predictive value of IL-8 to percent of total body surface area burned and incidence of MOF (P < 0.001). In the H group, IL-8 levels were able to predict sepsis (P < 0.002). In the H group, elevated IL-8 was associated with increased inflammatory and acute-phase responses compared with the L group (P < 0.05). High levels of IL-8 correlated with increased MOF, sepsis, and mortality. These data suggest that serum levels of IL-8 may be a valid biomarker for monitoring sepsis, infections, and mortality in burn patients.

The Systemic Effect of Burn Injury and Trauma on Muscle and Bone Mass and Composition

BACKGROUND

By understanding the global inflammatory effects on distant myopathies, surgeons can better guide the rehabilitative process for burn patients. The authors tested the systemic effect of burn injury on distant injured muscle and native bone using immunohistochemistry and validated a new morphometric analytic modality to reproducibly quantify muscle atrophy using computed tomographic imaging.

METHODS

In vivo studies were performed on C57/BL6 mice using an Achilles tenotomy with concurrent burn injury model. Total muscle and bone (tibia and fibula) volume/density were quantified near the site of Achilles tenotomy using micro-computed tomography at 5, 7, and 9 to 12 weeks after surgery. The impact of burn injury on the inflammatory cascade [nuclear factor (NF)-κB, p-NF-κB] and the interconnected protein catabolism signaling pathway (Atrogin-1) was assessed by immunohistochemistry.

RESULTS

Muscle volume and density at the site of Achilles tenotomy in burned mice were significantly diminished compared with nonburned mice at 5 weeks and 9 to 12 weeks. Similar decreases in muscle volume and density were observed when comparing tenotomy to no tenotomy. Cortical bone health remained stable in burn/tenotomy mice compared with tenotomy. Muscle atrophy was associated with up-regulation of p-NF-κB, NF-κB, and Atrogin-1 assessed by immunohistochemistry.

CONCLUSIONS

Burn injury significantly decreases muscle volume and density. Increased muscle atrophy using our computed tomographic morphometric analysis correlated with a significant increase in intramuscular inflammatory markers and proteolysis enzymes. This study demonstrates a unique characterization of how burn injuries may worsen local myopathy. Moreover, it provides a novel approach for quantifying muscle atrophy over an expanded period.

Incidence of ventilator associated pneumonia in burn patients with inhalation injury treated with high frequency percussive ventilation versus volume control ventilation: A systematic review

BACKGROUND

Pneumonia increases mortality in burn patients with inhalation injuries. We evaluated whether the use of High Frequency Percussive Ventilation (HFPV) in burn patients with inhalation injuries can decrease rates of Ventilator Associated Pneumonia (VAP) compared to Volume Control Ventilation (VCV).

METHODS

Data were gathered from PubMed, EMBASE, Web of Science, reference lists, and hand search. For unpublished data we searched ClinicalTrials.gov and RePORTER. We included observational and Randomized Controlled Trials (RCTs) that compared rates of VAP with the use of HFPV and VCV in adult burn patients with inhalation injury. Two reviewers independently extracted data from the retrieved studies and assessed them for eligibility, methodology, and quality.

RESULTS

281 abstracts were reviewed, of which 4 studies (540 patients) were included. Two were observational and two were RCTs. All studies had moderate risk of bias. One study had low external validity while others had moderate external validity. The two observational studies found non-concordant results. One study found a 24% statistically significant reduction in the rates of VAP while the other found no difference. The two RCTs had small sample sizes. There was no significant difference in VAP rates between HFPV and VCV. The VCV arms of the four studies were heterogeneous. Only one study used low tidal volumes, whereas the rest used high tidal volumes in the VCV arm.

CONCLUSION

Evidence about decreased incidence of VAP in burn patients with inhalation injuries who are on HFPV compared to those on VCV is inconclusive. Although enhanced airway clearance by HFPV was thought to play a role in decreasing VAP in this population, high tidal volume in the VCV arms could be a confounding factor that should be eliminated in future studies before a firm conclusion can be reached. More RCTs comparing HFPV to low tidal volume VCV are needed.

Severe burn increased skeletal muscle loss in mdx mutant mice

BACKGROUND

Severe burn causes muscle mass loss and atrophy. The balance between muscle cell death and growth maintains tissue homeostasis. We hypothesize that preexisting cellular structural defects will exacerbate skeletal muscle mass loss after burn. Using a Duchenne muscular dystrophy (mdx) mutant mouse, we investigated whether severe burn caused more damage in skeletal muscle with preexisting muscle disease.

METHODS

The mdx mice and wild-type (WT) mice received 25% total body surface area scald burn. Gastrocnemius (GM), tibialis anterior, and gluteus muscles were obtained at days 1 and 3 after burn. GM muscle function was measured on day 3. Animals without burn served as controls.

RESULTS

Wet tissue weight significantly decreased in tibialis anterior and gluteus in both mdx and WT mice after burn (P < 0.05). The ratio of muscle to body weight decreased in mdx mutant mice (P < 0.05) but not WT. Isometric force was significantly lower in mdx GM, and this difference persisted after burn (P < 0.05). Caspase-3 activity increased significantly after burn in both the groups, whereas HMGB1 expression was higher in burn mdx mice (P < 0.05). Proliferating cell nuclear antigen decreased significantly in mdx mice (P < 0.05). Myogenic markers pax7, myoD, and myogenin increased after burn in both the groups and were higher in mdx mice (P < 0.05).

CONCLUSIONS

More muscle loss occurred in response to severe burn in mdx mutant mice. Cell turnover in mdx mice after burn is differed from WT. Although markers of myogenic activation are elevated in mdx mutant mice, the underlying muscle pathophysiology is less tolerant of traumatic injury.

Autologous adipose-derived stem cells attenuate muscular atrophy and protect spinal cord ventral horn motor neurons in an animal model of burn injury

BACKGROUND AIMS

Burn injuries might increase muscle mass loss, but the mechanisms are still unclear. In this study, we demonstrated that burn injury induced spinal cord ventral horn motor neuron (VHMN) apoptosis and subsequently caused muscle atrophy and revealed the potential protection of autologous adipose-derived stem cells (ASCs) transplantation on spinal cord VHMNs and muscle against burn injury.

METHODS

Third-degree hind-paw burns were established by contact with a 75°C metal surface for 10 seconds. Adipose tissues were harvested from the groin fat pad, expanded in culture and labeled with chloromethyl-benzamido/1,1'-dioctadecyl-3,3,3',3'- tetramethyl indocarbocyanine perchlorate. The ASCs were transplanted into the injured hind paw at 4 weeks after burn injury. The lumbar spinal cord, sciatic nerve, gastrocnemius muscle and hind-paw skin were processed for immunofluorescent staining at 4 weeks after transplantation, including terminal deoxynucleotidyl transferase (TUNEL) assay, caspase-3, caspase-9, CD 90 and S100, and the gastrocnemius muscle was evaluated through the use of hematoxylin and eosin staining.

RESULTS

Caspase-3-positive, caspase-9-positive and TUNEL-positive cells were significantly increased in the corresponding dermatome spinal cord VHMNs after burn injury. Moreover, the decrease of Schwann cells in sciatic nerve and the increase of denervation atrophy in gastrocnemius muscle were observed. Furthermore, ASCs transplantation significantly attenuated apoptotic death of VHMNs and the area of muscle denervation atrophy in the gastrocnemius muscle fibers.

CONCLUSIONS

The animal model of third-degree burns in the hind paw showed significant apoptosis in the corresponding spinal cord VHMNs, which suggests that neuroprotection might be the potentially therapeutic target in burn-induced muscle atrophy. ASCs have potential neuroprotection against burn injuries through its anti-apoptotic effects.

Effects of whole-body vibration exercise on bone mineral content and density in thermally injured children

BACKGROUND

Loss of bone mass, muscle mass, and strength leads to significant disability in severely burned children. We assessed the effects of exercise combined with whole-body vibration (WBV) on bone mass, lean mass (LM), and muscle strength in children recovering from burns.

METHODS

Nineteen burned children (≥30% total body surface area [TBSA] burns) were randomly assigned to a 6-week exercise regimen either alone (EX; n=10) or in combination with a 6-week WBV training regimen (EX+WBV; n=9). WBV was performed concurrent to the exercise regimen for 5days/week on a vibrating platform. Dual-energy X-ray absorptiometry quantified bone mineral content (BMC), bone mineral density (BMD), and LM; knee extension strength was assessed using isokinetic dynamometry before and after training. Alpha was set at p<0.05.

RESULTS

Both groups were similar in age, height, weight, TBSA burned, and length of hospitalization. Whole-body LM increased in the EX group (p=0.041) and trended toward an increase in the EX+WBV group (p=0.055). On the other hand, there were decreases in leg BMC for both groups (EX, p=0.011; EX+WBV, p=0.047), and in leg BMD for only the EX group (EX, p<0.001; EX+WBV, p=0.26). Truncal BMC decreased in only the EX group (EX, p=0.009; EX+WBV, p=0.61), while BMD decreased in both groups (EX, p<0.001; EX+WBV group, p<0.001). Leg strength increased over time in the EX group (p<0.001) and the EX+WBV group (p<0.001; between-group p=0.31).

CONCLUSIONS

Exercise in combination with WBV may help attenuate regional bone loss in children recovering from burns. Studies are needed to determine the optimal magnitude, frequency, and duration of the vibration protocol, with attention to minimizing any potential interference with wound healing and graft closure.

Postoperative Albumin Drop Is a Marker for Surgical Stress and a Predictor for Clinical Outcome: A Pilot Study

Background. Surgical stress during major surgery may be related to adverse clinical outcomes and early quantification of stress response would be useful to allow prompt interventions. The aim of this study was to evaluate the acute phase protein albumin in the context of the postoperative stress response. Methods. This prospective pilot study included 70 patients undergoing frequent abdominal procedures of different magnitude. Albumin (Alb) and C-reactive protein (CRP) levels were measured once daily starting the day before surgery until postoperative day (POD) 5. Maximal Alb decrease (Alb Δ min) was correlated with clinical parameters of surgical stress, postoperative complications, and length of stay. Results. Albumin values dropped immediately after surgery by about 10 g/L (42.2 ± 4.5 g/L preoperatively versus 33.8 ± 5.3 g/L at day 1, P < 0.001). Alb Δ min was correlated with operation length (Pearson ρ = 0.470, P < 0.001), estimated blood loss (ρ = 0.605, P < 0.001), and maximal CRP values (ρ = 0.391, P = 0.002). Alb Δ min levels were significantly higher in patients having complications (10.0 ± 5.4 versus 6.1 ± 5.2, P = 0.005) and a longer hospital stay (ρ = 0.285, P < 0.020). Conclusion. Early postoperative albumin drop appeared to reflect the magnitude of surgical trauma and was correlated with adverse clinical outcomes. Its promising role as early marker for stress response deserves further prospective evaluation.

A Proper Enteral Nutrition Support Improves Sequential Organ Failure Score and Decreases Length of Stay in Hospital in Burned Patients

BACKGROUND

Severe burned patients developed metabolic imbalances and systemic inflammatory response syndrome (SIRS), which can lead to malnutrition, impaired immunologic response, multiple organ failure and death. Studies have shown that providing an early and adequate nutrition support can lower hypermetabolic response and improve the outcome. Unfortunately, little emphasis has been given to the role of nutritional support, especially for demonstrating the importance of a proper nutritional support in determining the outcome of critically burned patients.

OBJECTIVES

This study was designed to determine the possible protective effect of early and adequate nutrition support on sequential organ failure assessment (SOFA) score and length of stay (LOS) in hospital, in thermal burn victims.

PATIENTS AND METHODS

Thirty patients with severe thermal burn (More than 20% of total body surface area [TBSA] burn), on the first day in the intensive care unit, joined this double-blinded randomized controlled clinical trial. Patients were randomly divided into two groups: control group (group C, 15 patients) received hospital routine diet (liquid and chow diet, ad libitum) while intervention group (group I, 15 patients) received commercially prepared solution, with oral or tube feeding. The caloric requirement for these patients was calculated, according to the Harris-Benedict formula. The SOFA score was also measured on admission (SOFA0), day 2 (SOFA1), day 5 (SOFA2) and day 9 (SOFA3), consequently. The difference between the last measurement (SOFA3) and day 2 (SOFA1) was calculated.

RESULTS

The results showed that there was a significant change between SOFA3 and SOFA1, {-1[(-1) - 0], P = 0.013 vs. -1 [(-2) - 0], P = 0.109}. Mean LOS in hospital, for patients consuming commercial standard food, also proved to be shorter than those consuming hospital routine foods (17.64 ± 8.2 vs. 23.07 ± 11.89).

CONCLUSIONS

This study shows that an adequate nutritional support, in patients with severe burn injury, can improve SOFA score. It is also more cost-effective, resulting in a shorter LOS in hospital.

The effect of lower body burns on physical function

OBJECTIVE

To attenuate burn-induced catabolism, patients are often enrolled in a resistance exercise program as part of their physical rehabilitation. This study assessed how lower body burn locations affected strength and cardiopulmonary function.

METHODS

Children enrolled in an exercise study between 2003 and 2013, were 7-18 years of age, and burned ≥30% of their total body surface area were included. Analysis of variance was used to model the relationship of lower body strength (PTW) and cardiopulmonary function (VO2peak) due to burns which traverse the subject's lower body joints.

RESULTS

There was a significant relationship between PTW and burns at the hip and toe joints, showing a 26 N m/kg (p=0.010) and 33 N m/kg (p=0.013) decrease in peak torque, respectively. Burns at the hip joint corresponded to a significant decrease in VO2peak by 4.9 ml kg(-1) min(-1) (p=0.010) in peak cardiopulmonary function.

CONCLUSION

Physical function and performance are detrimentally affected by burns that traverse specific lower body joints. The most significant relationship on exercise performance was that of hip joint burns as it affected both strength and cardiopulmonary measurements. Ultimately, burns at hip and toe joints need to be considered when interpreting exercise test results involving the lower body.

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.

Differential acute and chronic effects of burn trauma on murine skeletal muscle bioenergetics

Altered skeletal muscle mitochondrial function contributes to the pathophysiological stress response to burns. However, the acute and chronic impact of burn trauma on skeletal muscle bioenergetics remains poorly understood. Here, we determined the temporal relationship between burn trauma and mitochondrial function in murine skeletal muscle local to and distal from burn wounds. Male BALB/c mice (8-10 weeks old) were burned by submersion of the dorsum in water (∼ 95 °C) to create a full thickness burn on ∼ 30% of the body. Skeletal muscle was harvested spinotrapezius underneath burn wounds (local) and the quadriceps (distal) of sham and burn treated mice at 3h, 24h, 4d and 10d post-injury. Mitochondrial respiration was determined in permeabilized myofiber bundles by high-resolution respirometry. Caspase 9 and caspase 3 protein concentration were determined by western blot. In muscle local to burn wounds, respiration coupled to ATP production was significantly diminished at 3h and 24h post-injury (P<0.001), as was mitochondrial coupling control (P<0.001). There was a 5- (P<0.05) and 8-fold (P<0.001) increase in respiration in response to cytochrome at 3h and 24h post burn, respectively, indicating damage to the outer mitochondrial membranes. Moreover, we also observed greater active caspase 9 and caspase 3 in muscle local to burn wounds, indicating the induction of apoptosis. Distal muscle mitochondrial function was unaltered by burn trauma until 10d post burn, where both respiratory capacity (P<0.05) and coupling control (P<0.05) were significantly lower than sham. These data highlight a differential response in muscle mitochondrial function to burn trauma, where the timing, degree and mode of dysfunction are dependent on whether the muscle is local or distal to the burn wound.

Skeletal Muscle Protein Breakdown Remains Elevated in Pediatric Burn Survivors up to One-Year Post-Injury

Acute alterations in skeletal muscle protein metabolism are a well-established event associated with the stress response to burns. Nevertheless, the long-lasting effects of burn injury on skeletal muscle protein turnover are incompletely understood. This study was undertaken to investigate fractional synthesis (FSR) and breakdown (FBR) rates of protein in skeletal muscle of pediatric burn patients (n  =  42, >30% total body surface area burns) for up to 1 year after injury. Skeletal muscle protein kinetics were measured in the post-prandial state following bolus injections of C6 and N phenylalanine stable isotopes. Plasma and muscle phenylalanine enrichments were quantified using gas chromatography-mass spectrometry. We found that the FSR in burn patients was 2- to 3-fold higher than values from healthy men previously reported in the literature (P ≤ 0.05). The FBR was 4- to 6-fold higher than healthy values (P  <  0.01). Therefore, net protein balance was lower in burn patients compared with healthy men from 2 weeks to 12 months post-injury (P  <  0.05). These findings show that skeletal muscle protein turnover stays elevated for up to 1 year after burn, an effect attributable to simultaneous increases in FBR and FSR. Muscle FBR exceeds FSR during this time, producing a persistent negative net protein balance, even in the post-prandial state, which likely contributes to the prolonged cachexia seen in burned victims.

Early rehabilitative exercise training in the recovery from pediatric burn

PURPOSE

The purpose of this study was to determine the effects of early outpatient exercise on muscle mass, function, and fractional synthetic rate in severely burned children.

METHODS

Forty-seven children with ≥40% total body surface area burn performed a 12-wk standard of care rehabilitation (SOC, n = 23) or rehabilitative exercise training (RET, n = 24) immediately after hospital discharge. Dual-energy x-ray absorptiometry was used to assess lean body mass (LBM) at discharge, posttreatment, and 12 months post-burn. Muscle function was evaluated with a Biodex Isokinetic Dynamometer, and peak aerobic fitness (V˙O2peak) was measured using a modified Bruce treadmill protocol posttreatment. Stable isotope infusion studies were performed in a subset of patients (SOC, n = 13; RET, n = 11) at discharge and posttreatment to determine mixed-muscle fractional synthetic rate.

RESULTS

Relative peak torque (RET, 138 ± 9 N·m·kg, vs SOC, 106 ± 9 N·m·kg) and V˙O2peak (RET, 32 ± 1 mL·kg·min, vs SOC, 28 ± 1 mL·kg·min) were greater at posttreatment with RET compared with those with SOC. In addition, RET increased whole-body (9% ± 2%) and leg (17% ± 3%) LBM compared with SOC. Furthermore, the percentage change in whole-body (18% ± 3%) and leg (31% ± 4%) LBM from discharge to 12 months post-burn was greater with RET compared to SOC. Muscle fractional synthetic rate decreased from discharge to posttreatment in both groups (6.9% ± 1.1% per day vs 3.4 ± 0.4% per day); however, no differences were observed between treatment groups at each time point.

CONCLUSIONS

Early outpatient exercise training implemented at hospital discharge represents an effective intervention to improve muscle mass and function after severe burn injury.

Recovery trajectories after burn injury in young adults: does burn size matter?

The impact of burn size on mortality is well known, but the association of burn size with the trajectories of long-term functional outcomes remains poorly studied. This prospective multi-center study included burned adults ages 19 to 30 years who completed the Young Adult Burn Outcome Questionnaire at initial baseline contact, 2 weeks, and at 6 and 12 months after initial questionnaire administration. Non-burned adults of comparable ages also completed the questionnaire as a reference group. The association between functional recovery and TBSA burned was analyzed longitudinally using generalized linear models with the generalized estimation equation technique. Functional status was characterized in 15 domains: physical function, fine motor function, pain, itch, social function limited by physical function, perceived appearance, social function limited by appearance, sexual function, emotion, family function, family concern, satisfaction with symptom relief, satisfaction with role, work reintegration, and religion. Scores were standardized to a mean of 50 and a SD of 10 based on non-burned controls. There were 153 burned and 112 non-burned subjects with a total of 620 questionnaires. TBSA burned was 11 ± 14% (mean ± SD); 31% had face involvement and 57% had hand involvement. The lag time from burn injury to questionnaire administration was on average 7 ± 7.7 months, with a maximum of 36 months. Lower recovery levels were associated with increasing burn size for physical function, pain, itch, work reintegration, emotion, satisfaction with symptom relief, satisfaction with role, family function, and family concern (P value ranged from .04-<.0001). No significant differences in recovery levels were found with increasing burn size for fine motor function, social function limited by physical function, sexual function, and religion; these areas tracked toward the age-matched non-burned group regardless of burn size. Perceived appearance and social function limited by appearance remained below the non-burn levels throughout the 3-year period regardless of burn size. Three-year recovery trajectories of survivors with larger burn size showed improvements in most areas, but these improvements lagged behind those with smaller burns. Poor perceived appearance was persistent and prevalent regardless of burn size and was found to limit social function in these young adult burn survivors. Expectations for multidimensional recovery from burns in young adults can be benchmarked based on burn size with important implications for patient monitoring and intervening in clinical care.

THE EFFECT OF GLUCOCORTICOIDS ON BONE AND MUSCLE

This article examines the current knowledge of the effects of both exogenous and endogenous glucocorticoids on bone and muscle. It demonstrates the similarity of effects of supraphysiologic loads of glucocorticoids regardless of whether they enter the body in the form of medication or are manufactured by the body in response to stimuli such as inflammation. The effects of endogenous glucocorticoids and the systemic inflammatory response resulting from pediatric burn injury are compared and the difficulty in sorting out which of the two factors is responsible for the ultimate effects on bone and muscle is pointed out. The focus then switches to the body's response to the influence of both glucocorticoids and inflammatory cytokines and evidence supporting a common pathway of response to oxidative damage caused by both is discussed. Current recommended medical management of glucocorticoid-induced bone and muscle loss is discussed and the failure to reconcile current management with known mechanisms is highlighted.

Release of insulin from PLGA-alginate dressing stimulates regenerative healing of burn wounds in rats

Burn wound healing involves a complex set of overlapping processes in an environment conducive to ischaemia, inflammation and infection costing $7.5 billion/year in the U.S.A. alone, in addition to the morbidity and mortality that occur when the burns are extensive. We previously showed that insulin, when topically applied to skin excision wounds, accelerates re-epithelialization and stimulates angiogenesis. More recently, we developed an alginate sponge dressing (ASD) containing insulin encapsulated in PLGA [poly(D,L-lactic-co-glycolic acid)] microparticles that provides a sustained release of bioactive insulin for >20 days in a moist and protective environment. We hypothesized that insulin-containing ASD accelerates burn healing and stimulates a more regenerative, less scarring healing. Using heat-induced burn injury in rats, we show that burns treated with dressings containing 0.04 mg insulin/cm(2) every 3 days for 9 days have faster closure, a higher rate of disintegration of dead tissue and decreased oxidative stress. In addition, in insulin-treated wounds, the pattern of neutrophil inflammatory response suggests faster clearing of the burned dead tissue. We also observe faster resolution of the pro-inflammatory macrophages. We also found that insulin stimulates collagen deposition and maturation with the fibres organized more like a basket weave (normal skin) than aligned and cross-linked (scar tissue). In summary, application of ASD-containing insulin-loaded PLGA particles on burns every 3 days stimulates faster and more regenerative healing. These results suggest insulin as a potential therapeutic agent in burn healing and, because of its long history of safe use in humans, insulin could become one of the treatments of choice when repair and regeneration are critical for proper tissue function.

The role of exercise in the rehabilitation of patients with severe burns

Severe burn trauma results in persistent skeletal muscle catabolism and prolonged immobilization. We hypothesize that structured rehabilitative exercise is a safe and efficacious strategy to restore lean body mass and physical function in burn victims. Here, we review the evidence for the utility of rehabilitative exercise training in restoring physiological function in burn survivors.

A conceptual framework: the early and late phases of skeletal muscle dysfunction in the acute respiratory distress syndrome

Patients with acute respiratory distress syndrome (ARDS) often develop severe diaphragmatic and limb skeletal muscle dysfunction. Impaired muscle function in ARDS is associated with increased mortality, increased duration of mechanical ventilation, and functional disability in survivors. In this review, we propose that muscle dysfunction in ARDS can be categorized into an early and a late phase. These early and late phases are based on the timing in relationship to lung injury and the underlying mechanisms. The early phase occurs temporally with the onset of lung injury, is driven by inflammation and disuse, and is marked predominantly by muscle atrophy from increased protein degradation. The ubiquitin-proteasome, autophagy, and calpain-caspase pathways have all been implicated in early-phase muscle dysfunction. Late-phase muscle weakness persists in many patients despite resolution of lung injury and cessation of ongoing acute inflammation-driven muscle atrophy. The clinical characteristics and mechanisms underlying late-phase muscle dysfunction do not involve the massive protein degradation and atrophy of the early phase and may reflect a failure of the musculoskeletal system to regain homeostatic balance. Owing to these underlying mechanistic differences, therapeutic interventions for treating muscle dysfunction in ARDS may differ during the early and late phases. Here, we review clinical and translational investigations of muscle dysfunction in ARDS, placing them in the conceptual framework of the early and late phases. We hypothesize that this conceptual model will aid in the design of future mechanistic and clinical investigations of the skeletal muscle system in ARDS and other critical illnesses.

Serum from human burn victims impairs myogenesis and protein synthesis in primary myoblasts

The pathophysiological response to a severe burn injury involves a robust increase in circulating inflammatory/endocrine factors and a hypermetabolic state, both of which contribute to prolonged skeletal muscle atrophy. In order to characterize the role of circulating factors in muscle atrophy following a burn injury, human skeletal muscle satellite cells were grown in culture and differentiated to myoblasts/myotubes in media containing serum from burn patients or healthy, age, and sex-matched controls. While incubation in burn serum did not affect NFκB signaling, cells incubated in burn serum displayed a transient increase in STAT3 phosphorlyation (Tyr705) after 48 h of treatment with burn serum (≈ + 70%; P < 0.01), with these levels returning to normal by 96 h. Muscle cells differentiated in burn serum displayed reduced myogenic fusion signaling (phospho-STAT6 (Tyr641), ≈−75%; ADAM12, ≈-20%; both P < 0.01), and reduced levels of myogenin (≈−75%; P < 0.05). Concomitantly, myotubes differentiated in burn serum demonstrated impaired myogenesis (assessed by number of nuclei/myotube). Incubation in burn serum for 96 h did not increase proteolytic signaling (assessed via caspase-3 and ubiquitin levels), but reduced anabolic signaling [p-p70S6k (Ser421/Thr424), −30%; p-rpS6 (Ser240/244), ≈-50%] and impaired protein synthesis (−24%) (P < 0.05). This resulted in a loss of total protein content (−18%) and reduced cell size (−33%) (P < 0.05). Overall, incubation of human muscle cells in serum from burn patients results in impaired myogenesis and reduced myotube size, indicating that circulating factors may play a significant role in muscle loss and impaired muscle recovery following burn injury.

Effects of exercise on soleus in severe burn and muscle disuse atrophy

BACKGROUND

Muscle loss is a sequela of severe burn and critical illness with bed rest contributing significantly to atrophy. We hypothesize that exercise will mitigate muscle loss after burn with bed rest.

MATERIALS AND METHODS

Male rats were assigned to sham ambulatory (S/A), burn ambulatory (B/A), sham hindlimb unloading (S/H), or burn hindlimb unloading (B/H). Rats received a 40% scald burn or sham and were ambulatory or placed in hindlimb unloading, a model of bed rest. Half from each group performed twice daily resistance climbing. Hindlimb isometric forces were measured on day 14.

RESULTS

Soleus mass and muscle function were not affected by burn alone. Mass was significantly lower in hindlimb unloading (79 versus 139 mg, P < 0.001) and no exercise (103 versus 115 mg, P < 0.01). Exercise significantly increased soleus mass in B/H (86 versus 77 mg, P < 0.01). Hindlimb unloading significantly decreased muscle force in the twitch (12 versus 31 g, P < 0.001), tetanic (55 versus 148 g, P < 0.001), and specific tetanic measurements (12 versus 22 N/cm(2), P < 0.001). Effects of exercise on force depended on other factors. In B/H, exercise significantly increased twitch (14 versus 8 g, P < 0.05) and specific tetanic force (14 versus 7 N/cm(2), P < 0.01). Fatigue index was lower in ambulatory (55%) and exercise (52%) versus hindlimb (69%, P = 0.03) and no exercise (73%, P = 0.002).

CONCLUSIONS

Hindlimb unloading is a significant factor in muscle atrophy. Exercise increased the soleus muscle mass, twitch, and specific force in this model. However, the fatigue index decreased with exercise in all groups. This suggests exercise contributes to functional muscle change in this model of disuse and critical illness.

Predictors of muscle protein synthesis after severe pediatric burns

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

Prognostic study, level III.

Investigation of Bone Health Subsequent to Vitamin D Supplementation in Children Following Burn Injury

BACKGROUND

The effect of supplemental vitamin D on fracture occurrence following burn injuries is unclear. The objective of this study was to evaluate postintervention incidence of fractures in children during the rehabilitative phase postburn (PB) following participation in a randomized clinical trial of vitamin D supplementation.

MATERIALS AND METHODS

Follow-up for fracture evaluation was obtained in 39 of 50 patients randomized to daily enteral vitamin D2, D3, or placebo throughout the acute burn course. Serum 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, D2, D3, calcitonin, and bone alkaline phosphatase (BAP) measurements were obtained PB day 7, midpoint, discharge, and 1-year PB. Urinary calcium was obtained PB day 7 and midpoint. Dual-energy x-ray absorptiometry (DXA) was performed at discharge and 1-year PB.

RESULTS

Fractures were reported in 6 of 39 respondents. Four fractures occurred in the placebo group, 2 in the D2 group, and none in the D3 group. Serum vitamin D, calcitonin, BAP, and urinary calcium were similar between fracture groups. The group with fracture morbidity had larger burn size (83.8% ± 4.9% vs 53.0% ± 2.9%, P < .0001), greater full-thickness burn (69.7% ± 9.4% vs 39.4% ± 4.1%, P = .02), and increased incidence of inhalation injury (33% vs 6%, P = .04). Decreased bone mineral density z score was noted at discharge in the placebo fracture compared with no-fracture group (P < .05).

CONCLUSION

This preliminary report suggests there may be benefit of vitamin D3 in reducing postdischarge fracture risk. Results reaffirm the importance of monitoring bone health in pediatric patients postburn.

Nutrition and metabolism in the rehabilitative phase of recovery in burn children: a review of clinical and research findings in a speciality pediatric burn hospital

During the rehabilitation phase of burn injury, patient care transitions from critical care medicine to restorative treatment strategies that encompass physical and occupational therapies, nutrition repletion, and psychosocial support for community reintegration. As pediatric burn patients undergo rehabilitation, nutrition assessment remains ongoing to define nutritional status and any alterations in metabolism that may take place. For some, a persistent hypermetabolic state appears evident, and weight loss may continue. The severity and duration however varies among patients. Many patients enter their rehabilitative phase with visible lean body mass depletion, and the focus of nutritional therapy for them shifts to replenishing nutritional status, while supporting rehabilitative efforts. Over the past decade, we have conducted studies on energy and protein metabolism, body composition, including bone mineralization, and general wellness in over 130 patients to better understand changes in metabolism and nutritional status during the rehabilitative phase of recovery. This abstract summarizes our findings.

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.

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.

Aerobic exercise training in modulation of aerobic physical fitness and balance of burned patients

[Purpose] This study aimed to determine the impact of aerobic exercise on aerobic capacity, balance, and treadmill time in patients with thermal burn injury. [Subjects and Methods] Burned adult patients, aged 20–40 years (n=30), from both sexes, with second degree thermal burn injuries covering 20–40% of the total body surface area (TBSA), were enrolled in this trial for 3 months. Patients were randomly divided into; group A (n=15), which performed an aerobic exercise program 3 days/week for 60 min and participated in a traditional physical therapy program, and group B (n=15), which only participated in a traditional exercise program 3 days/week. Maximal aerobic capacity, treadmill time, and Berg balance scale were measured before and after the study. [Results] In both groups, the results revealed significant improvements after treatment in all measurements; however, the improvement in group A was superior to that in group B. [Conclusion] The results provide evidence that aerobic exercises for adults with healed burn injuries improve aerobic physical fitness and balance.

Third-degree hindpaw burn injury induced apoptosis of lumbar spinal cord ventral horn motor neurons and sciatic nerve and muscle atrophy in rats

Background. Severe burns result in hypercatabolic state and concomitant muscle atrophy that persists for several months, thereby limiting patient recovery. However, the effects of burns on the corresponding spinal dermatome remain unknown. This study aimed to investigate whether burns induce apoptosis of spinal cord ventral horn motor neurons (VHMNs) and consequently cause skeletal muscle wasting. Methods. Third-degree hindpaw burn injury with 1% total body surface area (TBSA) rats were euthanized 4 and 8 weeks after burn injury. The apoptosis profiles in the ventral horns of the lumbar spinal cords, sciatic nerves, and gastrocnemius muscles were examined. The Schwann cells in the sciatic nerve were marked with S100. The gastrocnemius muscles were harvested to measure the denervation atrophy. Result. The VHMNs apoptosis in the spinal cord was observed after inducing third-degree burns in the hindpaw. The S100 and TUNEL double-positive cells in the sciatic nerve increased significantly after the burn injury. Gastrocnemius muscle apoptosis and denervation atrophy area increased significantly after the burn injury. Conclusion. Local hindpaw burn induces apoptosis in VHMNs and Schwann cells in sciatic nerve, which causes corresponding gastrocnemius muscle denervation atrophy. Our results provided an animal model to evaluate burn-induced muscle wasting, and elucidate the underlying mechanisms.

Effects of pharmacological interventions on muscle protein synthesis and breakdown in recovery from burns

OBJECTIVE

The pathophysiological response to burn injury disturbs the balance between skeletal muscle protein synthesis and breakdown, resulting in severe muscle wasting. Muscle loss after burn injury is related to increased mortality and morbidity. Consequently, mitigation of this catabolic response has become a focus in the management of these patients. The aim of this review is to discuss the literature pertaining to pharmacological interventions aimed at attenuating skeletal muscle catabolism in severely burned patients.

DATA SELECTION

Review of the literature related to skeletal muscle protein metabolism following burn injury was conducted. Emphasis was on studies utilizing stable isotope tracer kinetics to assess the impact of pharmacological interventions on muscle protein metabolism in severely burned patients.

CONCLUSION

Data support the efficacy of testosterone, oxandrolone, human recombinant growth hormone, insulin, metformin, and propranolol in improving skeletal muscle protein net balance in patients with severe burns. The mechanisms underlying the improvement of protein net balance differ between types and dosages of drugs, but their main effect is on protein synthesis. Finally, the majority of studies have been conducted during the acute hypermetabolic phase of the injury. Except for oxandrolone, the effects of drugs on muscle protein kinetics following discharge from the hospital are largely unknown.

Neuroendocrine regulation of inflammation

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

Measuring burn injury outcomes

Burn injury affects all facets of life. Burn care has improved over time. Improved survival after burn injury has resulted in a shift in outcome measurement from inpatient morbidity and mortality to long-term functional and health-related quality-of-life measures. Integration of professionals from different disciplines has enabled burn centers to develop collaborative methods of assessing the quality of care delivered to patients with burns based on their ability to reintegrate into their normal physical, social, psychological, and functional activities. Burn outcomes will continue to develop on the foundation that has been built and will generate evidence-based best practices in the future.

Uncoupled skeletal muscle mitochondria contribute to hypermetabolism in severely burned adults

Elevated metabolic rate is a hallmark of the stress response to severe burn injury. This response is mediated in part by adrenergic stress and is responsive to changes in ambient temperature. We hypothesize that uncoupling of oxidative phosphorylation in skeletal muscle mitochondria contributes to increased metabolic rate in burn survivors. Here, we determined skeletal muscle mitochondrial function in healthy and severely burned adults. Indirect calorimetry was used to estimate metabolic rate in burn patients. Quadriceps muscle biopsies were collected on two separate occasions (11 ± 5 and 21 ± 8 days postinjury) from six severely burned adults (68 ± 19% of total body surface area burned) and 12 healthy adults. Leak, coupled, and uncoupled mitochondrial respiration was determined in permeabilized myofiber bundles. Metabolic rate was significantly greater than predicted values for burn patients at both time points (P < 0.05). Skeletal muscle oxidative capacity, citrate synthase activity, a marker of mitochondrial abundance, and mitochondrial sensitivity to oligomycin were all lower in burn patients vs. controls at both time points (P < 0.05). A greater proportion of maximal mitochondrial respiration was linked to thermogenesis in burn patients compared with controls (P < 0.05). Increased metabolic rate in severely burned adults is accompanied by derangements in skeletal muscle mitochondrial function. Skeletal muscle mitochondria from burn victims are more uncoupled, indicating greater heat production within skeletal muscle. Our findings suggest that skeletal muscle mitochondrial dysfunction contributes to increased metabolic rate in burn victims.

Predictors of insulin resistance in pediatric burn injury survivors 24 to 36 months postburn

Burn injury is a dramatic event with acute and chronic consequences including insulin resistance. However, factors associated with insulin resistance have not been previously investigated. The purpose of this study was to identify factors associated with long-term insulin resistance in pediatric burn injury survivors. The study sample consisted of 61 pediatric burn injury survivors 24 to 36 months after the burn injury, who underwent an oral glucose tolerance test. To assess insulin resistance, the authors calculated the area under the curve for glucose and insulin. The diagnostic criteria of the American Diabetes Association were used to define individuals with impaired glucose metabolism. Additional data collected include body composition, anthropometric measurements, burn characteristics, and demographic information. The data were analyzed using multivariate linear regression analysis. Approximately 12% of the patients met the criteria for impaired glucose metabolism. After adjusting for possible confounders, burn size, age, and body fat percentage were associated with the area under the curve for glucose (P < .05 for all). Time postburn and lean mass were inversely associated with the area under the curve for glucose (P < .05 for both). Similarly, older age predicted higher insulin area under the curve. The results indicate that a significant proportion of pediatric injury survivors suffer from glucose abnormalities 24 to 36 months postburn. Burn size, time postburn, age, lean mass, and adiposity are significant predictors of insulin resistance in pediatric burn injury survivors. Clinical evaluation and screening for abnormal glucose metabolism should be emphasized in patients with large burns, older age, and survivors with high body fat.

Burn-associated delayed dilated cardiomyopathy evaluated by cardiac PET and SPECT: Report of a case

Dilated cardiomyopathy is a delayed-onset and rarely reported cardiac complication of burn injury although the mechanism remains unclear. We thus report a case of dilated cardiomyopathy following severe burn injury, in which technetium 99m sestamibi single-photon emission computed tomography (SPECT), iodine-123 beta-methyl-iodophenylpentadecanoic acid SPECT and ¹⁸F-fluorodeoxyglucose positron emission tomography (PET) were performed to evaluate the pathophysiologic condition in combination with cardiac catheterization and myocardial biopsy. The cardiac PET and SPECT images showed reduced myocardial blood flow, decreased fatty acid metabolism, and increased glucose utilization in the left ventricular lateral wall in spite of normal coronary angiography, no significant cardiac fibrosis, and inflammatory cell infiltration, which suggests that myocardial ischemia due to microcirculatory disturbance in hypermetabolic state associated with burn injury might be a causative mechanism of dilated cardiomyopathy in this case. A beta blocker, bisoprolol, was successfully introduced in this patient in combination with oral inotropic agents, pimobendan and digitalis after the prolonged use of intravenous dobutamine infusion, which might have been beneficial for this patient with burn-associated dilated cardiomyopathy not only to reduce regional myocardial ischemia but also to attenuate hypermetabolic state after severe burn injury. <Learning objective: Dilated cardiomyopathy complicated with burn injury has been reported to cause a sudden attack of dyspnea and death. This case report suggests that burn-associated dilated cardiomyopathy may be caused by relative myocardial ischemia due to microvascular disturbance in hypermetabolic state associated with burn injuries and can be treated effectively with beta blockers with or without oral inotropic agents.>.

Phosphodiesterase (PDE) inhibitor torbafylline (HWA 448) attenuates burn-induced rat skeletal muscle proteolysis through the PDE4/cAMP/EPAC/PI3K/Akt pathway

Treatment of rats after burn-injury with the cyclic AMP phosphodiesterase (PDE) inhibitor, torbafylline (also known as HWA 448) significantly reversed changes in rat skeletal muscle proteolysis, PDE4 activity, cAMP concentrations and mRNA expression of TNFα, IL-6, ubiquitin and E3 ligases. Torbafylline also attenuated muscle proteolysis during in vitro incubation, and this effect was blocked by the inhibitor Rp-cAMPS. Moreover, torbafylline significantly increased phospho-Akt levels, and normalized downregulated phospho-FOXO1 and phospho-4E-BP1 in muscle of burn rats. Similarly, torbafylline also normalized phosphorylation levels of Akt and its downstream elements in TNFα+IFNγ treated C2C12 myotubes. Torbafylline enhanced protein levels of exchange protein directly activated by cAMP (Epac) both in skeletal muscle of burn rats and in TNFα+IFNγ treated C2C12 myotubes. Pretreatment with a specific antagonist of PI3K or Epac significantly reversed the inhibitory effects of torbafylline on TNFα+IFNγ-induced MAFbx mRNA expression and protein breakdown in C2C12 myotubes. Torbafylline inhibits burn-induced muscle proteolysis by activating multiple pathways through PDE4/cAMP/Epac/PI3K/Akt.

Exercise training after burn injury: a survey of practice

Exercise programs capable of contributing positively to the long-term rehabilitation of burn patients should be included in outpatient rehabilitation programs. However, the extent and intensity of the resistance and cardiopulmonary exercise prescribed are unclear. This study was conducted to investigate the existence, design, content, and prescription of outpatient cardiopulmonary and resistance exercise programs within outpatient burn rehabilitation. A survey was designed to gather information on existing exercise programs for burn survivors and to assess the extent to which these programs are included in overall outpatient rehabilitation programs. Three hundred and twenty-seven surveys were distributed in the licensed physical and occupational therapists part of the American Burn Association Physical Therapy/Occupational Therapy Special Interest Group. One hundred and three surveys were completed. Eighty-two percent of respondents indicated that their institutions offered outpatient therapy after discharge. The frequency of therapists' contact with patients during this period varied greatly. Interestingly, 81% of therapists stated that no hospital-based cardiopulmonary endurance exercise programs were available. Patients' physical function was infrequently determined through the use of cardiopulmonary parameters (oxygen consumption and heart rate) or muscle strength. Instead, more subjective parameters such as range of motion (75%), manual muscle testing (61%), and quality of life (61%) were used. Prescription and follow-up assessment of cardiopulmonary endurance training are inconsistent among institutions, underscoring the need for greater awareness of the importance of exercise in any burn rehabilitation program. Identification of cardiopulmonary and progressive resistance parameters for establishing and tracking exercise training is also needed to maximize exercise-induced benefits.

Hypoglycemia is associated with increased postburn morbidity and mortality in pediatric patients

OBJECTIVE

The objective of this study was to determine the prevalence of hypoglycemia after burn injury and whether hypoglycemia is associated with increased postburn morbidity and mortality.

DESIGN

Cohort analysis.

SETTING

Academic pediatric burn hospital.

PATIENTS

This analysis included 760 pediatric burn patients, who were stratified according the number of hypoglycemic episodes (< 60 mg/dL glucose) they experienced while in the ICU. Clinical outcomes and metabolic and inflammatory biomarkers were analyzed during the first 60 days post admission. Patients with one or more hypoglycemic events were matched with patients not experiencing any event using propensity score matching, and outcomes and biomarker expression were compared between groups.

MEASUREMENTS AND MAIN RESULTS

Eighty-four patients had one episode of hypoglycemia, 108 patients had two or more episodes of hypoglycemia, and 568 patients never experienced hypoglycemia. Patients with one or more hypoglycemic episodes had longer hospitalization, as well as more frequent infections, sepsis, multiple organ failure, and death (p < 0.05). The 166 propensity score-matched patients with one or more hypoglycemic events had greater inflammatory and metabolic responses, prevalence of sepsis, multiple organ failure, and mortality than burn patients without hypoglycemic (p < 0.05).

CONCLUSIONS

Hypoglycemic episodes correlate with injury severity and inhalation injury. When adjusted for injury severity, hypoglycemia is associated with significantly higher postburn morbidity and mortality.

Influence of inhalation injury on energy expenditure in severely burned children

OBJECTIVE

Determine the effect of inhalation injury on burn-induced hypermetabolism in children.

DESIGN

Prospective study comparing hypermetabolism (i.e., resting energy expenditure and oxygen consumption) in burned children with and without inhalation injury during acute hospitalization.

SETTING

Single pediatric burn center.

PATIENTS

Eighty-six children (1-18 years) with ≥40% total body surface area burns were stratified to two groups: no inhalation injury and inhalation injury.

INTERVENTIONS

None.

MAIN MEASUREMENTS AND RESULTS

Inhalation injury was diagnosed based on bronchoscopic evaluation. At admission, PaO2:FiO2 ratios (an index of respiratory distress) were significantly higher in patients with no inhalation injury than in patients with inhalation injury. No differences were detected in resting energy expenditure or percent of the predicted basal metabolic rate between groups. Additionally, oxygen consumption did not significantly differ between groups.

CONCLUSIONS

Inhalation injury does not augment the burn-induced hypermetabolic stress response in children, as reflected by resting energy expenditure and oxygen consumption.

Survivors versus nonsurvivors postburn: differences in inflammatory and hypermetabolic trajectories

OBJECTIVE

To evaluate whether a panel of common biomedical markers can be utilized as trajectories to determine survival in pediatric burn patients.

BACKGROUND

Despite major advances in clinical care, of the more than 1 million people burned in the United States each year, more than 4500 die as a result of their burn injuries. The ability to predict patient outcome or anticipate clinical trajectories using plasma protein expression would allow personalization of clinical care to optimize the potential for patient survival.

METHODS

A total of 230 severely burned children with burns exceeding 30% of the total body surface, requiring at least 1 surgical procedure were enrolled in this prospective cohort study. Demographics, clinical outcomes, and inflammatory and acute-phase responses (serum cytokines, hormones, and proteins) were determined at admission and at 11 time points for up to 180 days postburn. Statistical analysis was performed using a 1-way analysis of variance, the Student t test, χ test, and Mann-Whitney test where appropriate.

RESULTS

Survivors and nonsurvivors exhibited profound differences in critical markers of inflammation and metabolism at each time point. Nonsurvivors had significantly higher serum levels of interleukin (IL)-6, IL-8, granulocyte colony-stimulating factor, monocyte chemoattractant protein-1, C-reactive protein, glucose, insulin, blood urea nitrogen, creatinine, and bilirubin (P < 0.05). Furthermore, nonsurvivors exhibited a vastly increased hypermetabolic response that was associated with increases in organ dysfunction and sepsis when compared with survivors (P < 0.05).

CONCLUSIONS

Nonsurvivors have different trajectories in inflammatory, metabolic, and acute phase responses allowing differentiation of nonsurvivors from survivors and now possibly allowing novel predictive models to improve and personalize burn outcomes.

Increased expression of atrogenes and TWEAK family members after severe burn injury in nonburned human skeletal muscle

Severe burn induces rapid skeletal muscle proteolysis after the injury, which persists for up to 1 year and results in skeletal muscle atrophy despite dietary and rehabilitative interventions. The purpose of this research was to determine acute changes in gene expression of skeletal muscle mass regulators postburn injury. Specimens were obtained for biopsy from the vastus lateralis of a nonburned leg of eight burned subjects (6M, 2F: 34.8 ± 2.7 years: 29.9 ± 3.1% TBSA burn) at 5.1 ± 1.1 days postburn injury and from matched controls. mRNA expression of cytokines and receptors in the tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) families, and the ubiquitin proteasome E3 ligases, atrogin-1 and MuRF-1, was determined. TNF receptor 1A was over 3.5-fold higher in burn. Expression of TNF-like weak inducer of apoptosis and its receptor were over 1.6 and 6.0-fold higher in burn. IL-6, IL-6 receptor, and glycoprotein 130 were elevated in burned subjects with IL-6 receptor over 13-fold higher. The level of suppressor of cytokine signaling-3 was also increased nearly 6-fold in burn. Atrogin-1 and MuRF-1 were more than 4- and 3-fold higher in burn. These results demonstrate for the first time that severe burn in humans has a remarkable impact on gene expression in skeletal muscle of a nonburned limb of genes that promote inflammation and proteolysis. Because these changes likely contribute to the acute skeletal muscle atrophy in areas not directly affected by the burn, in the future it will be important to determine the responsible systemic cues.

Insulin effects on glucose tolerance, hypermetabolic response, and circadian-metabolic protein expression in a rat burn and disuse model

Insulin controls hyperglycemia after severe burns, and its use opposes the hypermetabolic response. The underlying molecular mechanisms are poorly understood, and previous research in this area has been limited because of the inadequacy of animal models to mimic the physiological effects seen in humans with burns. Using a recently published rat model that combines both burn and disuse components, we compare the effects of insulin treatment vs. vehicle on glucose tolerance, hypermetabolic response, muscle loss, and circadian-metabolic protein expression after burns. Male Sprague-Dawley rats were assigned to three groups: cage controls (n = 6); vehicle-treated burn and hindlimb unloading (VBH; n = 11), and insulin-treated burn and hindlimb unloading (IBH; n = 9). With the exception of cage controls, rats underwent a 40% total body surface area burn with hindlimb unloading, then IBH rats received 12 days of subcutaneous insulin injections (5 units·kg(-1)·day(-1)), and VBH rats received an equivalent dose of vehicle. Glucose tolerance testing was performed on day 14, after which blood and tissues were collected for analysis. Body mass loss was attenuated by insulin treatment (VBH = 265 ± 17 g vs. IBH = 283 ± 14 g, P = 0.016), and glucose clearance capacity was increased. Soleus and gastrocnemius muscle loss was decreased in the IBH group. Insulin receptor substrate-1, AKT, FOXO-1, caspase-3, and PER1 phosphorylation was altered by injury and disuse, with levels restored by insulin treatment in almost all cases. Insulin treatment after burn and during disuse attenuated the hypermetabolic response, increased glucose clearance, and normalized circadian-metabolic protein expression patterns. Therapies aimed at targeting downstream effectors may provide the beneficial effects of insulin without hypoglycemic risk.

The surgically induced stress response

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

Occurrence of multiorgan dysfunction in pediatric burn patients: incidence and clinical outcome

OBJECTIVE

To examine the incidence of single or multiple organ failure postburn and its resultant clinical outcomes during acute hospitalization.

BACKGROUND

Patient outcomes are inherently dependent on intact organ function; however, burn injury affects the structure and function of almost every organ, but especially lung, liver, kidney, and heart. Therefore, single-organ failure and/or multiorgan failure (MOF) are thought to contribute significantly to postburn morbidity and mortality, but to date no large trial examining the effects of MOF on postburn outcomes exists.

METHODS

Incidence of MOF was monitored in 821 pediatric burn patients during acute hospitalization. Patients were divided into groups on the basis of the incidence of single-organ-specific failure, MOF, and non-MOF. The DENVER2 score was used to assess organ-specific scores for lung, liver, kidney, and heart. The patient's demographics, injury characteristics, and outcome parameters were recorded.

RESULTS

Respiratory failure has the highest incidence in the early phase of postburn injury and decreases starting 5 days postburn. Cardiac failure was noted to have the highest incidence throughout hospital stay. Incidence of hepatic failure increases with the hospital length of stay and is associated with a high mortality during the late phase of the acute hospital stay. Renal failure has an unexpectedly low incidence but is associated with a high mortality during the first 3 weeks postburn injury. Three or more organ failure is associated with very high mortality.

CONCLUSIONS

This is the first large study in burn patients to determine the incidence of organ-specific failure and outcome. The results of this study confirmed the expected chronologic incidence of organ-specific failure and yield the long-term mortality from liver and renal failure.

Mild obesity is protective after severe burn injury

OBJECTIVE

To assess the impact of obesity on morbidity and mortality in severely burned patients.

BACKGROUND

Despite the increasing number of people with obesity, little is known about the impact of obesity on postburn outcomes.

METHODS

A total of 405 patients were prospectively enrolled as part of the multicenter trial Inflammation and the Host Response to Injury Glue Grant with the following inclusion criteria: 0 to 89 years of age, admitted within 96 hours after injury, and more than 20% total body surface area burn requiring at least 1 surgical intervention. Body mass index was used in adult patients to stratify according to World Health Organization definitions: less than 18.5 (underweight), 18.5 to 29.9 (normal weight), 30 to 34.9 (obese I), 35 to 39.9 (obese II), and body mass index more than 40 (obese III). Pediatric patients (2 to ≤18 years of age) were stratified by using the Centers for Disease Control and Prevention and World Health Organization body mass index-for-age growth charts to obtain a percentile ranking and then grouped as underweight (<5th percentile), normal weight (5th percentile to <95th percentile), and obese (≥95th percentile). The primary outcome was mortality and secondary outcomes were clinical markers of patient recovery, for example, multiorgan function, infections, sepsis, and length of stay.

RESULTS

A total of 273 patients had normal weight, 116 were obese, and 16 were underweight; underweight patients were excluded from the analyses because of insufficient patient numbers. There were no differences in primary and secondary outcomes when normal weight patients were compared with obese patients. Further stratification in pediatric and adult patients showed similar results. However, when adult patients were stratified in obesity categories, log-rank analysis showed improved survival in the obese I group and higher mortality in the obese III group compared with obese I group (P < 0.05).

CONCLUSIONS

Overall, obesity was not associated with increased morbidity and mortality. Subgroup analysis revealed that patients with mild obesity have the best survival, whereas morbidly obese patients have the highest mortality. (NCT00257244).

The endocrine response to severe burn trauma

The endocrine system is frequently altered after a major burn trauma. Besides the endocrine response to stress characterized by hypercortisolism, several hypothalamus-hypophysis-target gland axes are rapidly perturbed within a few days. These alterations can persist in the long term and deserve an appropriate treatment. Disturbances in water clearance and glucidic metabolism are also common and need to be diagnosed and corrected to decrease morbidity in such patients. Bone and mineral metabolism is deeply compromised and requires correction of mineral abnormalities in order to improve symptoms and prevent bone loss. No large prospective and/or intervention trials are available to date to elaborate age-related, evidence-based recommendations to monitor and treat burn-related endocrine alterations.