Evaluation of predicted and measured energy requirements in burned children

A methodological and clinical approach to measured energy expenditure in the critically ill pediatric patient

The metabolic response to injury and stress is characterized initially by a decreased energy expenditure (Ebb phase) followed by an increased metabolic expenditure (Flow phase). Indirect calorimetry is a methodology utilized to measure energy expenditure and substrate utilization by measuring gas exchange in exhaled air and urinary nitrogen. The use of indirect calorimetry in critically ill patients requires precise equipment to obtain accurate measurements. The most recent guidelines suggested that measured energy expenditure by indirect calorimetry be used to determine energy requirements. This article reviews the methodological and clinical use of indirect calorimetry in critically ill pediatric patients.

Resting Energy Expenditure Prediction Equations in the Pediatric Population: A Systematic Review

Background and Aims: The determination of energy requirements is necessary to promote adequate growth and nutritional status in pediatric populations. Currently, several predictive equations have been designed and modified to estimate energy expenditure at rest. Our objectives were (1) to identify the equations designed for energy expenditure prediction and (2) to identify the anthropometric and demographic variables used in the design of the equations for pediatric patients who are healthy and have illness. Methods: A systematic search in the Medline/PubMed, EMBASE and LILACS databases for observational studies published up to January 2021 that reported the design of predictive equations to estimate basal or resting energy expenditure in pediatric populations was carried out. Studies were excluded if the study population included athletes, adult patients, or any patients taking medications that altered energy expenditure. Risk of bias was assessed using the Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. Results: Of the 769 studies identified in the search, 39 met the inclusion criteria and were analyzed. Predictive equations were established for three pediatric populations: those who were healthy (n = 8), those who had overweight or obesity (n = 17), and those with a specific clinical situation (n = 14). In the healthy pediatric population, the FAO/WHO and Schofield equations had the highest R ² values, while in the population with obesity, the Molnár and Dietz equations had the highest R ² values for both boys and girls. Conclusions: Many different predictive equations for energy expenditure in pediatric patients have been published. This review is a compendium of most of these equations; this information will enable clinicians to critically evaluate their use in clinical practice. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=226270, PROSPERO [CRD42021226270].

Pediatric enteral nutrition therapy for burn victims: when should it be initiated?

Objective

To review the scientific evidence regarding the initiation of enteral nutrition in the pediatric burn population.

Methods

This study was a systematic review and meta-analysis of randomized clinical trials comparing early enteral nutrition and late enteral nutrition in individuals aged 1 month to 18 years with burns. The MEDLINE/PubMed, Embase and Cochrane Library databases were searched using the terms "burns", "fires", "child nutrition disorders", "nutritional support" and related terms.

Results

Three articles that included a total of 781 patients were identified. There was no significant difference in the mortality rate between the early and late groups (OR = 0.72, 95%CI = 0.46 - 1.15, p = 0.17). Patients who received early enteral nutrition had a 3.69-day reduction in the length of hospital stay (mean difference = -3.69, 95%CI = -4.11 - -3.27, p < 0.00001). There was a higher incidence of diarrhea and vomiting and decreased intestinal permeability in the early group. This group also presented higher a serum insulin concentration and insulin/glucagon ratio as well as lower caloric deficit and weight loss when compared to the control group.

Conclusion

Analysis of the different intragroup variables suggests the importance of starting nutritional support early. Considering the number of pediatric burn patients, there is a need for robust studies with greater scientific impact.

Systematic review of factors associated with energy expenditure in the critically ill

BACKGROUND AND AIMS

Indirect calorimetry is the reference standard for energy expenditure measurement. Predictive formulae that replace it are inaccurate. Our aim was to review the patient and clinical factors associated with energy expenditure in critically ill patients.

METHODS

We conducted a systematic review of the literature. Eligible studies were those reporting an evaluation of factors and energy expenditure. Energy expenditure and factor associations with p-values were extracted from each study, and each factor was classified as either significantly, indeterminantly, or not associated with energy expenditure. Regression coefficients were summarized as measures of central tendency and spread. Metanalysis was performed on correlations.

RESULTS

The search strategy yielded 8521 unique articles, 307 underwent full text review, and 103 articles were included. Most studies were in adults. There were 95 factors with 352 evaluations. Minute volume, weight, age, % body surface area burn, sedation, post burn day, and caloric intake were significantly associated with energy expenditure. Heart rate, fraction of inspired oxygen, respiratory rate, respiratory disease diagnosis, positive end expiratory pressure, intensive care unit days, C- reactive protein, and size were not associated with energy expenditure. Multiple factors (n = 37) were identified with an unclear relationship with energy expenditure and require further evaluation.

CONCLUSIONS

An important interval step in the development of accurate formulae for energy expenditure estimation is a better understanding of relationships between patient and clinical factors and energy expenditure. The review highlights the limitations of currently available data, and identifies important factors that are not included in current prediction formulae of the critically ill.

Graphical Calculation of Estimated Energy Expenditure in Burn Patients

BACKGROUND

Historically, estimated energy expenditure (EEE) has been related to the percent of body surface area burned. Subsequent evaluations of these estimates have indicated that the earlier formulas may overestimate the amount of caloric support necessary for burn-injured patients. Ireton-Jones et al derived 2 equations for determining the EEE required to support burn patients, 1 for ventilator-dependent patients and 1 for spontaneously breathing patients. Evidence has proved their reliability, but they remain challenging to apply in a clinical setting given the difficult and cumbersome mathematics involved. This study aims to introduce a graphical calculation of EEE in burn patients that can be easily used in the clinical setting.

METHODS

The multivariant linear regression analysis from Ireton-Jones et al yielded equations that were rearranged into the form of a simple linear equation of the type y = mx + b. By choosing an energy expenditure and the age of the subject, the weight was calculated. The endpoints were then calculated, and a graph was mapped by means of Adobe FrameMaker.

RESULTS

A graphical representation of Ireton-Jones et al's equations was obtained by plotting the weight (kg) on the y axis, the age (years) on the x axis, and a series of parallel lines representing the EEE in burn patients. The EEE has been displayed graphically on a grid to allow rapid determination of the EEE needed for a given patient of a designated weight and age. Two graphs were plotted: 1 for ventilator-dependent patients and 1 for spontaneously breathing patients. Correction factors for sex, the presence of additional trauma, and obesity are indicated on the graphical calculators.

CONCLUSIONS

We propose a graphical tool to calculate caloric requirements in a fast, easy, and portable manner.

Current consensus and controversies in major burns management

Most doctors in Britain receive some training in the care of the burned patient, if not as an undergraduate then as part of training in accident and emergency medicine or in the Advanced Trauma Life Support (ATLS®) course. Because major burn injury presents infrequently to the average district hospital, most of this training is rusty by the time it is needed. Further, most have little opportunity to catch up with developments in this very specialized area of trauma medicine.

This paper aims to address some of these shortcomings by describing recent advances in burn care and highlighting areas of current debate. The fluids used for resuscitation, improved options for treatment, the status of ongoing discussions about treatment facilities and the state of the art in managing smoke inhalation are reviewed. Some pointers to the future and to avenues for research are suggested.

Nutritional care of the obese adult burn patient: a U.K. Survey and literature review

Obesity is an emerging healthcare problem and affects an increasing number of burn patients worldwide. An email survey questionnaire was constructed and distributed among the 16 U.K. burn services providing adult inpatient facilities to investigate nutritional practices in obese thermally injured patients. Responses received from all dieticians invited to participate in the study were analyzed, and a relevant literature review of key aspects of nutritional care is presented. The majority of services believe that obese patients warrant a different nutritional approach with specific emphasis to avoid overfeeding. The most common algebraic formulae used to calculate calorific requirements include the Schofield, Henry, and modified Penn State equations. Indirect calorimetry despite being considered the "criterion standard" tool to calculate energy requirements is not currently used by any of the U.K. burn services. Gastric/enteral nutrition is initiated within 24 hours of admission in the services surveyed, and a variety of different practices were noted in terms of fasting protocols before procedures requiring general anesthesia/sedation. Hypocaloric regimens for obese patients are not supported by the majority of U.K. facilities, given the limited evidence base supporting their use. The results of this survey outline the wide diversity of dietetic practices adopted in the care of obese burn patients and reveal the need for further study to determine optimal nutritional strategies.

Update on the critical care management of severe burns

Care of the severely injured patient with burn requires correct diagnosis, appropriately tailored resuscitation, and definitive surgical management to reduce morbidity and mortality. Currently, mortality rates related to severe burn injuries continue to steadily decline due to the standardization of a multidisciplinary approach instituted at tertiary health care centers. Prompt and accurate diagnoses of burn wounds utilizing Lund-Browder diagrams allow for appropriate operative and nonoperative management. Coupled with diagnostic improvements, advances in resuscitation strategies involving rates, volumes, and fluid types have yielded demonstrable benefits related to all aspects of burn care. More recently, identification of comorbid conditions such as inhalation injury and malnutrition have produced appropriate protocols that aid the healing process in severely injured patients with burn. As more patients survive larger burn injuries, the early diagnosis and successful treatment of secondary and tertiary complications are becoming commonplace. While advances in this area are exciting, much work to elucidate immune pathways, diagnostic tests, and effective treatment regimens still remain. This review will provide an update on the critical care management of severe burns, touching on accurate diagnosis, resuscitation, and acute management of this difficult patient population.

Nutrition in burns: Galveston contributions

Aggressive nutrition support is recommended following severe burn injury. Initially, such injury results in a prolonged and persistent hypermetabolic response mediated by a 10- to 20-fold elevation in plasma catecholamines, cortisol, and inflammatory mediators. This response leads to twice-normal metabolic rates, whole-body catabolism, muscle wasting, and severe cachexia. Thus, it is relevant to review the literature on nutrition in burns to adjust/update treatment. Failure to meet the increased substrate requirements may result in impaired wound healing, multiorgan dysfunction, increased susceptibility to infection, and death. Therefore, aggressive nutrition support is essential to ensure adequate burn care, attenuate the hypermetabolic response, optimize wound healing, minimize devastating catabolism, and reduce morbidity and mortality. Here, the authors provide nutrition recommendations gained from prospective trials, retrospective analyses, and expert opinions based on the authors' practices in Galveston, Texas, and Vienna, Austria.

Predicting energy requirements of pediatric patients with disease: which methods are appropriate?

Children with disease that are admitted to hospitals are vulnerable to an inadequate intake of energy and essential nutrients. Therefore, adequate diet is important to meet their growing energy needs and to help reduce malnutrition-related incidence of morbidity and mortality. An effective nutritional support among pediatric patients in the clinical setting depends largely on accurate estimation of energy requirements. Hence, recommendation for calorie intake based on measurements of total energy expenditure of pediatric patients is highly warranted. Currently, numerous assessment methods for determining energy expenditure are available and feasible for use among children. However, it is important for clinicians to understand the strengths and limitations of these different techniques in order to optimize the outcome during recovery of their patients. Advocating appropriate recommendation is essential for the enhancement of nutritional support management for patients in a cost-effective manner.

Nutritional therapy for burns in children and adults

Burns are a serious injury that requires optimal nutritional support. This review discusses the nutritional care for adults and children with major burns. A burned patient's metabolism is greatly accelerated with increased requirements for energy, carbohydrates, proteins, fats, vitamins, minerals, and antioxidants. Early nutrition by parenteral and enteral feedings is vital. Careful assessment of the nutritional state of the burn patient is also important to reduce infection, recovery time, and long-term sequelae.

An evaluation of the safety and efficacy of an anti-inflammatory, pulmonary enteral formula in the treatment of pediatric burn patients with respiratory failure

Respiratory failure is associated with a high mortality rate in burned children. Recently, a specialized pulmonary enteral formula (SPEF) was commercially introduced as an adjunct intervention in acute lung injury management. SPEF contains condition-specific nutrients to modulate the inflammatory response. The study examined SPEF impact in critically ill, pediatric burn patients with respiratory failure. Medical records of acute burn patients admitted December 1997 to October 2006 were reviewed for SPEF treatment. Respiratory and renal indices were compared on the first and final days of SPEF use. Nineteen patients with respiratory failure received SPEF for a mean of 10.8 +/- 0.9 days during their acute burn course. Mean age was 5.3 +/- 1.5 years. Mean total body surface area burn was 44.3 +/- 5.4% with 32.5 +/- 6.4% full thickness. Patients were admitted 2.3 +/- 0.9 days postburn. Significant improvements in peak pressure, PEEP, FiO2, P:F ratio, Pco2, Po2, and ETco2 were noted. Seventeen of the 19 patients survived despite the fact that 9 of the 19 patients developed severe barotrauma requiring multiple tube thoracotomies, and all 19 had extremely poor prognoses at SPEF initiation. Adult SPEF formula for critically ill, pediatric burn patients with respiratory failure is safe and well tolerated. SPEF seems to facilitate recovery from acute lung injury as evidenced by improvements in oxygenation and pulmonary compliance.

Energy expenditure and balance following pediatric intensive care unit admission: a longitudinal study of critically ill children

OBJECTIVE

Longitudinal comparison of prescribed energy, actually administered energy, and energy expenditure (EE) predicted by Schofield's equations to actual EE, as determined by daily indirect calorimetry measurements in critically ill children during the first 7 days following admission.

DESIGN

Observational study.

SETTING

Pediatric intensive care unit, high and medium care wards, in a university hospital.

PATIENTS

Forty-six mechanically ventilated and spontaneously breathing infants and children (0-18 yrs) who were admitted with sepsis or following major abdominal or thoracic surgery or trauma.

INTERVENTIONS

Daily indirect calorimetry measurements and assessment of energy balance.

MEASUREMENTS AND MAIN RESULTS

Energy balance studies were performed for a total of 298 admission days in 13 sepsis, 27 surgery, and 6 trauma patients. Indirect calorimetry measurements were performed on 89% of the days. Mean measured EE was 44.6 +/- 15 kcal/kg.d and equaled predicted EE (44.2 +/- 12 kcal/kg.d; p = .56). Measured EE did not change over time, neither overall nor in diagnostic subgroups. Overall, median (range) administered energy was 31.1 (0-119) kcal/kg.d, which was significantly lower than measured EE (p < .001) and predicted EE (p < .001). Patients were underfed on 60% of days and overfed on 28% of days. Administered energy rose significantly in the course of admission, independently of diagnostic category, and did not differ from prescribed energy (p = .42). Energy intake was significantly higher in sepsis patients than in surgery and trauma patients during the whole course of the study (p < .01). The cumulative energy balance was positive only in sepsis patients. The administration of parenteral feeding was the single significant factor determining energy intake in mixed-effect modeling.

CONCLUSIONS

Measured EE was stable and not significantly different from predicted values over the course of hospitalization. Underfeeding was frequently present and mainly due to prescription and administration of energy amounts inferior to measured EE values in enterally fed patients.

Comparison of Measured Resting Energy Expenditure Versus Predictive Equations in Pediatric Burn Patients

Many equations have been developed to estimate resting energy expenditure (REE) in thermally injured patients. A consensus has not been reached on the accuracy of these equations in children. The purpose of our study was to compare three predictive equations: Harris Benedict x 2 multiplier (HB x 2), Mayes (MG), and the WorId Health Organization x 2 multiplier (WHO x 2) with measured resting energy expenditure x I.3 multiplier (MREE x 1.3) in pediatric burn patients. MREE was measured by open-circuit indirect calorimetry in 10 burned children (6 boys, 4 girls) aged 2 to 10 years with TBSA burn ranges from 35% to 97%. MREE x 1.3 was compared with values obtained by HB x 2, MG, and WHO x 2 predictive equations. When comparing MREE x 1.3 with all three equations, significant differences were found when compared with HB x 2 and MG, but there were no significant difference between MREE x 1.3 vs WHO x 2. The HB x 2 and MG equations overpredicted MREE x 1.3 by 29% and 19%, respectively. Many predictive equations have been developed to predict energy expenditure in burns, but their accuracy in predicting MREE x 1.3 is variable. A larger study comparing/contrasting predictive equations and resting energy expenditure measured by indirect calorimetry is needed to improve the prediction of energy needs in burned children.

Nutritional support in 111 pediatric intensive care units: a European survey

OBJECTIVE

To study current strategies in nutritional management of pediatric intensive care units (PICUs) in Europe, focusing on energy requirements.

DESIGN AND SETTING

Survey by a 35-item questionnaire sent to representatives of 242 PICUs in 28 countries. Addresses were obtained from national PICU associations and the members' list of the European Society of Pediatric and Neonatal Intensive Care.

PARTICIPANTS

Staff members of 111 European PICUs (46%) from 24 countries.

MEASUREMENTS AND RESULTS

Predominantly physicians were reported to be responsible for nutritional support. In 73% of PICUs a multidisciplinary nutritional team was available. In most PICUs daily energy requirements were estimated using weight, age, predictive equations and correction factors. In 17% of PICUs energy expenditure was regularly measured by indirect calorimetry. Nutritional status was mostly assessed by weight, physical examination, and a wide range of biochemical blood parameters. Approximately 70% of PICUs used dedicated software for nutritional support. A similar percentage of PICUs regarded "nutrition" as a research topic and part of the residents' training program.

CONCLUSIONS

Most European PICUs regard nutritional support as an important aspect of patient care, as shown by the presence of nutritional teams, software, research, and education. However, energy requirements of pediatric intensive care patient were based predominantly on estimations rather than on measurements.

Nutritional support of the critically ill child

The pediatric metabolic response to injury and operation is proportional to the degree of stress and causes an increase in the turnover of proteins, fats, and carbohydrates. Thereby, substrates are made readily available for the immune response and wound healing. Because this process requires energy, the resting energy expenditure of ill patients increases. Whole-body protein degradation rates are elevated out of proportion to synthetic rates, and negative protein balance also ensues. Neonates and children are particularly susceptible to the loss of lean body mass and its attendant increased morbidity and mortality caused by an intrinsic lack of endogenous stores and greater baseline requirements. An appropriately designed mixed fuel system of nutritional support replete in protein does not quell this metabolic response but can result in anabolism and continued growth in ill children. In addition, the use of adequate analgesia and anesthesia is a readily available and proven means of reducing the magnitude of the catabolism associated with operation and injury. Finally, as hormonal- and cytokine-mediated metabolic alterations are better understood, therapeutic interventions may become available to directly modulate the metabolic response to illness, thus potentially further improving clinical outcome in pediatric surgical patients.

The metabolic needs of critically ill children and neonates

The pediatric metabolic response to injury and operation is proportional to the degree of stress and causes an increase in the turnover of proteins, fats, and carbohydrates. Thereby, substrates are made readily available for the immune response and wound healing. Because this process requires energy, the resting energy expenditure of ill patients increases. Whole-body protein degradation rates are elevated out of proportion to synthetic rates, and negative protein balance also ensues. Neonates and children are particularly susceptible to the loss of lean body mass and its attendant increased morbidity and mortality caused by an intrinsic lack of endogenous stores and greater baseline requirements. An appropriately designed mixed fuel system of nutritional support replete in protein does not quell this metabolic response but can result in anabolism and continued growth in ill children. In addition, the use of adequate analgesia and anesthesia is a readily available and proven means of reducing the magnitude of the catabolism associated with operation and injury. Finally, as hormonal- and cytokine-mediated metabolic alterations are better understood, therapeutic interventions may become available to directly modulate the metabolic response to illness, thus potentially further improving clinical outcome in pediatric surgical patients.

Comprehensive assessment of the components of energy expenditure in infants using a new infant respiratory chamber

BACKGROUND

Current methods for energy expenditure (EE) measurements in term infants do not include simultaneous measurements of basal and sleeping metabolic rates (BMR and SMR) or a measure of physical activity (PA). Furthermore, prediction equations for calculating EE are not appropriate for use in infants with metabolic disorders.

OBJECTIVE

To develop and utilize a new infant respiratory chamber for simultaneous measurements of EE (kJ/d), preprandial BMR (kJ/d), SMR (kJ/d) and an index of PA (oscillations/min/kg body weight) in infants with a variety of metabolic disorders, for up to four hours in a hospital setting, while allowing parental interaction in a comfortable environment.

METHODS

We obtained simultaneous measurements of EE, BMR, SMR and PA in 21 infants (66+/-73 days of age, 4.5+/-1.7 kg body weight, 55+/-8 cm in length and 16+/-7% body fat) using our new infant respiratory chamber. Six of these infants were healthy, seven had thyroid dysfunction, five were HIV-exposed, one had AIDS, one had intrauterine and postnatal growth retardation and one was a hypothermic preterm infant. Energy expenditure, BMR and SMR were extrapolated for 24 hours. Body composition was estimated by skin-fold thickness, using age-appropriate formulae. Basal metabolic rate obtained with the infant respiratory chamber was compared to BMR that was calculated using the appropriate World Health Organization (WHO) equations.

RESULTS

In all infants both extrapolated 24-hour EE and BMR correlated with fat-free mass (r = 0.89, p<0.01 and r = 0.88, p<0.01 respectively). Twenty-four hour EE also correlated with PA (r = 0.52, p<0.05). The HIV-exposed infants had higher BMR (p<0.05) than that calculated by the appropriate WHO equation. We found that the caloric requirements for the infant with growth retardation were underestimated based on the infant's weight and age.

CONCLUSIONS

The infant respiratory chamber can measure all of the main components of EE. Some of the results obtained differed significantly from those obtained by the WHO equations; therefore, the new infant respiratory chamber is necessary for estimating EE in infants with metabolic and growth disorders.

The metabolic basis of the increase of the increase in energy expenditure in severely burned patients

BACKGROUND

Severe burn trauma is characterized by an elevated rate of whole-body energy expenditure.

APPROACH

In this short review, we have attempted to assess the metabolic characteristics of and basis for the persistent increase in energy expenditure during the flow phase of the injury. We consider some aspects of normal energy metabolism, including the contribution of the major adenosine triphosphate (ATP)-consuming reactions to the standard or basal metabolic rate. Rate estimates are compiled from the literature for a number of these reactions in healthy adults and burned patients, and the values are related to the increased rates of whole-body energy expenditure with burn injury.

RESULTS

Whole-body protein synthesis, gluconeogenesis, urea production, and substrate cycles (total fatty acid and glycolytic-gluconeogenic) account for approximately 22%, 11%, 3%, 17%, and 4%, respectively, of the burn-induced increase in total energy expenditure.

CONCLUSIONS

These ATP-consuming reactions, therefore, seem to explain approximately 57% of the increase in energy expenditure. The remainder of the increase may be due, in large part, to altered Na(+)-K(+)-ATPase activity and increased proton leakage across the mitochondrial membrane.

Common nutritional issues in pediatric and adult critical care medicine

This article discusses many of the nutritional topics important to the intensivist. Nutritional assessment, substrate immunonutrition, and disease specific issues are presented. Early introduction of enteral feeds and the use of nutritional modulation are emphasized.

Urinary urea nitrogen is imprecise as a predictor of protein balance in burned children

OBJECTIVE

To compare estimates of protein balance using the urinary urea nitrogen method to predict total urinary nitrogen with isotopically derived estimates of metabolic protein balance as defined by the difference between rates of protein synthesis and breakdown.

DESIGN

Prospective, descriptive, repeated measures analysis. Urinary urea nitrogen collections were obtained for 8 to 24 hours before infusion of L-[1-13C] leucine during fed and fasted states.

SUBJECTS/SETTING

Eight acutely burned pediatric patients consecutively admitted to Shriners Burns Institute, Boston Unit, for medical and surgical care of their injuries.

MAIN OUTCOME MEASURES

The difference between isotopically measured rates of protein synthesis and breakdown was used as an index of protein balance and compared with estimates of protein balance determined using the urinary urea nitrogen method.

STATISTICAL ANALYSIS

Least squares regression analysis was used to assess the value of urinary urea nitrogen as a predictor of metabolic protein balance. Limits of agreements were used to determine bias and precision between the two methods.

RESULTS

Urinary urea nitrogen was a significant predictor of metabolic protein balance (r2 = .77, P < .001). The direction of protein balance was the same in 14 of 16 measurements; however, there was significant lack of agreement between the two methods as demonstrated by large quantitative differences in protein balance.

CONCLUSION

Although the urinary-urea-nitrogen-based estimates of protein balance correlate well with isotopically derived protein balance, they are not precise in determining protein balance in seriously burned children.

Lack of effect of sleep on energy expenditure and physiologic measures in critically ill burn patients

OBJECTIVE

Energy expenditure measurements, performed while patients are in standardized resting conditions, are often used as an indicator of care by which to evaluate the adequacy of nutrition support regimens. Little attention has been directed toward examining potential errors incurred by deriving daily energy needs based on a single 15- to 20-minute measurement. This study was designed to differentiate energy expenditure during periods of sleep (defined as time spent in any of the standard sleep stages) and wakefulness in pediatric burn patients.

DESIGN

Twenty-four-hour indirect calorimetry, polysomnography, and physiologic assessments (mean arterial pressure, heart rate, body temperature, oxygen saturation, and respiratory rate) were conducted simultaneously in 14 patients, who were thermally injured and tracheally intubated, for a total of 45 24-hour intervals.

SUBJECTS

Mean age of the patients was 10.8+/-1.2 years. Mean total body surface area of the injury was 55.7+/-4.7%, and mean full-thickness burn was 48.8+/-6.0%.

STATISTICAL ANALYSES PERFORMED

A nested general linear analysis of variance model was used to evaluate the association between sleep, wakefulness, and energy needs; adjustments were made for postburn day and multiple test runs per patient.

RESULTS

On average, subjects slept 699+/-46 minutes/day. They experienced a large number of awakenings from sleep (mean=53+/-6.3 awakenings per 24 hours). Patients had mean energy expenditure of 2,529+/-396 kcal/day while awake and 2,360+/-291 kcal/day while asleep, and these mean values did not differ significantly. No differences in physiologic measurements during the awake and sleep states were found.

APPLICATIONS

There appears to be little difference in the metabolism of seriously injured burn patients while asleep and while awake. The study deemphasizes the importance of performing indirect calorimetry at rest in critically ill pediatric burn patients, and it supports the extrapolation of daily energy expenditure from a 15- to 20-minute steady-state measurement obtained during either sleep or wakefulness.