Beth A. Shields

Determination of resting energy expenditure after severe burn

The purpose of this study was to evaluate the accuracy of nine predictive equations for calculating energy expenditure in severely burned adult subjects. The selected equations have been reported as commonly used or determined to be the most accurate. This prospective, observational study was conducted on adult subjects admitted between October 2007 and July 2010 with ≥20% TBSA full-thickness burns (excluding electrical burns or severe head injury). Indirect calorimetry measurements were conducted as a convenience sample during the first 30 days after injury. Demographic data were collected, and resting energy expenditure was calculated using the nine selected predictive equations and compared to measured energy expenditure (MEE) using descriptive and comparative statistics. Data were collected on 31 subjects with an average age of 46 ± 19 years and %TBSA burn of 48 ± 21%. For all equations, slopes and intercepts were significantly different from the line of identity when compared with MEE. A calorie-dependent bias was present for all equations, in that lower calorie range was overestimated and the higher calorie range was underestimated. Only the Carlson and Milner equations had results that were not significantly different from the MEE and mean differences that were not significant in all burn size ranges. None of the equations had a strong correlation with MEE. Of the equations available, the Milner and Carlson equations are the most satisfactory in predicting resting energy expenditure in severely burned adults when indirect calorimetry is unavailable.

Signals from Fat after Injury: Plasma Adipokines and Ghrelin Concentrations in the Severely Burned

INTRODUCTION Hypermetabolism is universal in the severely burned and is characterized by catabolism of lean mass and body fat with associated insulin resistance. Adipokines are likely to play a role in these changes but have not been identified to date in burn patients. METHODS From a single burn ICU, 17 burn patients with an expected stay>14 days were studied. Study period began within 14 days of admission. Over 7 days, plasma samples were collected for measurement of leptin, adiponectin, resistin, ghrelin, insulin, and cortisol by ELISA. For comparison, samples from 15 healthy controls of similar age, BMI, and blood glucose were obtained. RESULTS Mean age was 33±17 years and BMI 26±3.4. Average burn size was 45±20% TBSA and ISS 32±10 with 72% having inhalation injury; in-hospital mortality was 29%. Estimated energy needs were 3626±710 kcal, of which 84±21% were met by enteral feeding with intensive insulin treatment (glucose 80-110 mg/ml). Using the homeostasis model assessment of insulin resistance, burned subjects were more resistant than controls (17±11.3 and 8±10.0). Insulin levels were elevated (57±35.6 μU/ml in burned subject vs. 26±31.1 μU/ml in controls), and cortisol concentrations increased (50±41.2 μg/dl vs. 12±3.9 μg/dl). These traditional hormone changes were associated with increased resistin (16.6±5.5 ng/ml vs. 3.8±0.9 ng/ml) and decreased leptin (8.8±8.9 ng/ml vs. 19.4±23.5 ng/ml), adiponectin (9±3.5 ng/ml vs. 17±10.2 ng/ml), and ghrelin (0.37±0.14 ng/ml vs.0.56±0.26 ng/ml). CONCLUSION Patients with burns, who are characteristically hypermetabolic with hypercortisolism and insulin resistant, have significant changes in adipokine levels that appear independent of the magnitude of initial injury or metabolic derangement. In addition, suppression of ghrelin in the presence of decreased leptin and adiponectin levels in combination with increased insulin and resistin levels represent unexpected changes in the metabolic milieu of the injured patient possibly due to dramatic activation of inflammatory pathways, indicating strategies for treatment.

Prevalence and Impact of Late Defecation in the Critically Ill, Thermally Injured Adult Patient

The aim of this study was to determine the prevalence of late defecation (absence of laxation for more than 6 days after admission) as an indicator of lower-gastrointestinal (GI) tract dysfunction in burn patients. In addition, the authors wanted to determine whether the addition of polyethylene glycol 3350 to the standard bowel regimen led to improvement in markers of lower-GI function and outcomes. The authors conducted a retrospective chart review of patients admitted to the burn intensive care unit during a 26-month period. Inclusion criteria were 20% or more TBSA burn, requirement for mechanical ventilation, and age over 18 years. Of 83 patients included, the prevalence of late defecation was 36.1% (n = 30). There was no association between late defecation and mortality. Patients with late defecation had more frequent episodes of constipation after first defecation (P =.03), of feeding intolerance (P =.007), and received total parenteral nutrition more frequently (P =.005). The addition of polyethylene glycol to the standard bowel regimen did not affect markers of lower-GI function. Late defecation occurs in more than one third of critically ill burn patients. Late defecation was associated with ongoing lower-GI dysfunction, feeding intolerance, and the use of total parenteral nutrition. The causal relationship between these problems has not been determined. A prospective study at the authors’ institution is currently planned to attempt to validate late defecation as a marker of lower-GI tract dysfunction, determine its relationship to various outcomes, and determine risk factors for its development.

Are Visceral Proteins Valid Markers for Nutritional Status in the Burn Intensive Care Unit

The aim of this study was to determine whether visceral protein levels increase under positive nitrogen balance during times of decrease in acute-phase reactant levels in patients with burn injury. This was a post hoc analysis of a prospective, interventional study approved by the local institutional review board. A total of 10 subjects between the ages of 18 and 72 with ≥20% total body surface area burn were enrolled over a 14-month period. Data were collected for five subjects (average age of 28 ± 8 years and total body surface area burn of 69 ± 15%) who met the inclusion criteria. Changes in visceral protein levels were examined along with nitrogen balance and acute-phase reactants when the subjects were on enteral nutrition, and the proteins were not examined during times of acute kidney injury. Descriptive statistics were performed, and linear regression was used to analyze the association of visceral proteins and nitrogen balance during times that acute-phase reactant levels were decreasing. The subjects received an average of 3044 ± 1613 kcal/day (39 ± 20 kcal/kg), meeting 72% of caloric goals and achieving positive nitrogen balance during 68% of the 40 weekly measurements, with 174 ± 85 g of protein intake per day (2.2 ± 1.1 g/kg). There was a weak relationship between nitrogen balance and changes in visceral protein levels during times that the acute-phase reactant levels were decreasing (P > .05). Visceral proteins were found to be poor markers of nutritional status. This study is unique because the subjects were able to achieve positive nitrogen balance despite severe burns.

Predicting the Ability of Wounds to Heal Given Any Burn Size and Fluid Volume: An Analytical Approach

The intrinsic relationship between fluid volume and open wound size (%) has not been previously examined. Therefore, we conducted this study to investigate whether open wound size can be predicted from fluid volume plus other significant factors over time and to evaluate how machine learning may perform in predicting open wound size. This retrospective study involved patients with at least 20% TBSA burned. Various predictive models were developed and compared using goodness-of-fit statistics (R2, error [mean absolute error (MAE), root mean squared error (RMSE)]). Bland-Altman analysis was also performed to determine bias. A total of 121 patients were included in the analysis. Median TBSA burned was 31% (interquartile range: 26-46%). Average crystalloid volumes were 4.0 ± 2.7 ml/kg/TBSA in the first 24 hours. There were 24 (20%) patients who died. Importantly, multivariate analysis identified seven independent predictors of open wound size. Also, machine learning analysis was able to stratify patients based on the 20th day after admission, ~40% TBSA burned, and fluid volumes. Models for predicting open wound size varied in performance (R2 = .79-.90, MAE = 3.97-7.52, RMSE = 7.11-10.69). Notably, a combined machine learning model using only four features (fluid volume, days since admission, TBSA burned, age) performed the best and was sufficient to predict open wound size, with >90% goodness of fit and <4% absolute error. Bland-Altman analysis showed that there were no biases in the models. Open wound size can be predicted reliably using machine learning and fluid volume, days since admission, TBSA burned, and age. Future work will be needed to validate the utility of this studys models in a clinical environment.

Cutting-Edge Forward Burn Nutrition: from the Battlefield to the Burn Center

The US Army Institute of Surgical Research (USAISR) Burn Center is among the first and largest burn centers in the world and is the only US military burn center. This American Burn Association-verified facility is located on the Fort Sam Houston military base, in San Antonio, TX. It has provided comprehensive burn care to both military personnel and civilians in the South Texas area since the end of World War II. The global mission of the USAISR is to optimize combat casualty care, including care for major thermal injuries. This optimization of combat casualty care is executed clinically in the USAISR Burn Center through interdisciplinary teamwork and by advancing the care provided based on leading edge research. This article focuses on clinical lessons learned in the area of burn nutrition over the last decade at this facility during the support of the combat casualties from Operation Iraqi Freedom and Operation Enduring Freedom; it also provides a review of current evidence-based nutritional medicine practices for treating patients with thermal injuries. The extreme nutritional demand and metabolic changes associated with severe burns have been well described. This hypermetabolic, hypercatabolic response can lead to lean body mass and strength loss, resulting in the lack of ability to perform activities of daily living, as well as infection, wound healing failure, and death. Nutrition is an essential tool to avoid these catastrophic results, but monitoring the nutrition status is complicated by the whole body volume overload, resulting from the initial massive fluid resuscitation, which is required to prevent cardiovascular collapse. Techniques such as estimating weight loss from the caloric deficit must be utilized in place of actual weight loss until the interstitial fluid is reclaimed and a dry weight is achieved. Replenishing the extreme caloric expenditure and nitrogen loss is challenging; hence, careful monitoring of the nutrition intake is an essential component of burn treatment. In addition, there are a number of potential adverse effects of nutritional therapy that must also be factored into the complex decision-making regarding the initiation and delivery of nutrition in the critically ill burn population.