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Energy expenditure in patients with chronic renal failure.

Although nondialyzed, chronically uremic patients and patients undergoing maintenance hemodialysis often show evidence for wasting and calorie malnutrition and have low dietary energy intakes, their energy expenditure has never been systematically evaluated. It is possible that low energy intakes are an adaptive response to reduced energy needs; alternatively, energy expenditure could be normal or high and the low energy intakes would be inappropriate. Energy expenditure was therefore measured by indirect calorimetry in 12 normal individuals, 10 nondialyzed patients with chronic renal failure, and 16 patients undergoing maintenance hemodialysis. Energy expenditure was measured in the resting state, during quiet sitting, during controlled exercise on an exercise bicycle, and for four hours after ingestion of a test meal. Resting energy expenditure (kcal/min/1.73 m2) in the normal subjects, chronically uremic patients and hemodialysis patients was, respectively, 0.94 +/- 0.24 (SD), 0.91 +/- 0.20, and 0.97 +/- 0.10. There was also no difference among the three groups in energy expenditure during sitting, exercise, or the postprandial state. Within each group, energy expenditure during resting and sitting was directly correlated. During bicycling, energy expenditure was directly correlated with work performed, and the regression equation for this relationship was similar in each of the three groups. These findings suggest that for a given physical activity, energy expenditure in nondialyzed, chronically uremic patients and maintenance hemodialysis patients is not different from normal. The low energy intakes of many of these patients may be inadequate for their needs.

Adult↗

Total energy expenditure in stable patients with cystic fibrosis.

BACKGROUND AND AIMS: Undernutrition is a common problem in patients with cystic fibrosis and is associated with a poor prognosis. The two aims of this study were to assess and compare the two main field techniques in the measurement of total energy expenditure and, secondly, to assess total energy expenditure in stable patients and compare with healthy controls. METHODS: Resting energy expenditure was measured using indirect calorimetry and total energy expenditure was measured using 24-h heart rate (HR) methodology and doubly isotopically labelled water. RESULTS: Seventeen patients, mean age 23 years and FEV(1)52% predicted and thirteen controls were recruited. Resting energy expenditure was higher in patients 0.24 (0.03) MJ/kg Fat-Free Mass (FFM) compared to controls 0.22 (0.02) MJ/kg FFM, P=0.02. Twenty-four hour heart rate underestimated total energy expenditure, 9.49 (1.85) MJ/day in patients compared to 11.69 (2.79) MJ/day using doubly labelled water. There was no difference in total energy expenditure in patients and controls using both methods, 11.69 (2.79) MJ/day compared to 11.38 (2.71) MJ/day using doubly isotopically labelled water. CONCLUSIONS: In clinically stable young adult patients with moderately severe respiratory disease total energy expenditure is comparable to that an a control population despite in increase in resting energy expenditure and both 24-h HR and doubly isotopically labelled water are suitable for use in patients with cystic fibrosis.

Adult↗

Energy expenditure and wasting in human immunodeficiency virus infection.

BACKGROUND: Increased expenditure of energy at rest has been considered a contributing factor to the negative energy balance and weight loss that occur in patients with human immunodeficiency virus (HIV) infection. However, the true determinant of energy balance is not resting but total energy expenditure. We sought to determine the contribution of total energy expenditure to weight changes in patients with HIV-associated wasting. METHODS: We performed 51 assessments of energy metabolism in 27 men with HIV infection at different stages of disease, including periods of both rapid and slow weight loss. Resting energy expenditure was measured by indirect calorimetry, total energy expenditure by the doubly-labeled-water technique, and energy intake by recording the weight of food consumed. The results were compared with the rate of weight loss or gain. RESULTS: The mean (+/- SD) total energy expended by the HIV-infected men was 2750 +/- 670 kcal per day, no more than that expended by normal men. There was a significant positive relation between total energy expenditure and the rate of weight change (r = 0.61, P < 0.001); thus, during rapid weight loss, total energy expenditure was reduced to 2180 +/- 580 kcal per day (P = 0.009), primarily because of reduced physical activity. During rapid weight loss, the negative energy balance (-850 +/- 580 kcal per day) was primarily the result of the reduction in energy intake, to 1330 +/- 610 kcal per day; intake correlated strongly with the rate of weight change (r = 0.84, P < 0.001). CONCLUSIONS: In patients with HIV infection, total energy expenditure is reduced during episodes of weight loss. Reduced energy intake, not elevated energy expenditure, is the prime determinant of weight loss in HIV-associated wasting.

Adult↗

Prediction of energy expenditure from heart rate monitoring during submaximal exercise.

The aims of this study were to quantify the effects of factors such as mode of exercise, body composition and training on the relationship between heart rate and physical activity energy expenditure (measured in kJ x min(-1)) and to develop prediction equations for energy expenditure from heart rate. Regularly exercising individuals (n = 115; age 18-45 years, body mass 47-120 kg) underwent a test for maximal oxygen uptake (VO2max test), using incremental protocols on either a cycle ergometer or treadmill; VO2max ranged from 27 to 81 ml x kg(-1) x min(-1). The participants then completed three steady-state exercise stages on either the treadmill (10 min) or the cycle ergometer (15 min) at 35%, 62% and 80% of VO2max, corresponding to 57%, 77% and 90% of maximal heart rate. Heart rate and respiratory exchange ratio data were collected during each stage. A mixed-model analysis identified gender, heart rate, weight, V2max and age as factors that best predicted the relationship between heart rate and energy expenditure. The model (with the highest likelihood ratio) was used to estimate energy expenditure. The correlation coefficient (r) between the measured and estimated energy expenditure was 0.913. The model therefore accounted for 83.3% (R2) of the variance in energy expenditure in this sample. Because a measure of fitness, such as VO2max, is not always available, a model without VO2max included was also fitted. The correlation coefficient between the measured energy expenditure and estimates from the mixed model without VO2max was 0.857. It follows that the model without a fitness measure accounted for 73.4% of the variance in energy expenditure in this sample. Based on these results, we conclude that it is possible to estimate physical activity energy expenditure from heart rate in a group of individuals with a great deal of accuracy, after adjusting for age, gender, body mass and fitness.

Adult↗

Accuracy of heart-rate monitoring and activity diaries for estimating energy expenditure.

The accuracy of heart-rate monitoring and activity diaries for measuring energy expenditure in free-living individuals was studied in 12 women. Estimates of energy expenditure were calculated from heart-rate monitoring by use of four different prediction equations to describe the relationship between heart rate and energy expenditure. Estimates of energy expenditure from activity diaries were calculated using both individually measured and published values for the energy cost of activities. Energy intake adjusted for changes in body-energy stores was used as a reference. Heart-rate monitoring overestimated group energy expenditure from 2 to 9% and the errors in estimating individual energy expenditure ranged from -53 to 67%. Activity diaries underestimated group energy expenditure by 2-6% and the errors in estimating individual energy expenditure ranged from -39 to 56%. Heart-rate monitoring and activity diaries may prove useful for estimating the energy expenditure of groups but not individuals.

Activities of Daily Living↗

Age and sex effects on energy expenditure.

The aims of the present study were to examine possible effects of age and sex on energy expenditure independent of differences in body composition, and to develop prediction equations for individual estimation of energy expenditure. The study is based on 235 female and 78 male subjects ranging in age from 15 to 64 y and with body mass indexes (in kg/m2) ranging from 16.9 to 50.5. Basal metabolic rate (BMR), sleeping energy expenditure, and 24-h energy expenditure were measured with standardized protocols by indirect calorimetry in respiratory chambers. Anthropometric data were also recorded. Spontaneous physical activity (SPA) was estimated by a radar system during the chamber stay. About 90% of the variation in 24-b energy expenditure could be explained by differences in fat-free mass, fat mass, SPA, and duration of exercise (SEM: 526 kJ/d), whereas age and sex did not contribute significantly. When comparing energy expenditure adjusted for body composition and activity between two age groups (20-30 y, n = 98 and 50-65 y, n = 39), BMR was 4.6% lower in the older group (P = 0.04) and there was a tendency toward a lower sleeping energy expenditure in the older group (P = 0.06). No sex difference in any energy expenditure measurement could be found after differences in body composition and activity were taken into account. In conclusion, no sex effect and no linear decrease in energy expenditure was found with increased age and the middle-aged subjects had lower BMR than younger subjects independent of body size, body composition and activity.

Adolescent↗

Projecting future drug expenditures--2003.

Drug expenditure projections for 2003 and factors likely to influence drug costs are discussed. The United States continues to face the challenge of increased growth in health expenditures, and drug expenditures are continuing to increase faster than the growth in total health care expenditures. These increases can be largely attributed to an increase in the average age of the U.S. population and technological advancement. On the basis of price inflation and non-price inflationary factors, including increases in volume, shifts in patient and therapeutic intensity, and expected approval of new drugs, a 10-12% increase in drug expenditures in 2003 for the inpatient setting and a 13.5-15.5% increase for ambulatory care settings are forecasted. While few new drugs are expected to greatly influence expenditures in 2003, the continued diffusion of recently approved drugs such as drotrecogin alfa and nesiritide will have a dramatic impact on total drug expenditures and must be carefully considered in the budgeting process. An agent likely to have a significant impact on HIV treatment is enfuvirtide, the first in a new class of antiretrovirals (fusion inhibitors), but its high cost ($10,000-$15,000 per year) may limit patients' access to this medication. An expanded user's guide is provided to assist the reader in appropriate application of this information in the drug budgeting process. Technological, demographic, and market-based changes and changes in public policy will continue to influence pharmaceutical expenditures in the coming year. An understanding of the overall drivers of medication expenditures and vigilance in monitoring pharmaceutical innovation are critical in the effective management of these resources.

Drug Approval↗

Projecting future drug expenditures--2004.

PURPOSE: Drug expenditure trends since 2002 and projected drug expenditures for 2004 are discussed. SUMMARY: In 2002 there was a moderation in the trend of increasing drug expenditures. Drug expenditures increased by 12.3% between 2001 and 2002. This trend continued in the first half of 2003, with expenditures increasing by only 10% compared with 2002. This moderation in the drug expenditures trend can be attributed to many factors, especially patent expirations and decreases in new drug approvals. Higher cost sharing for consumers and a general economic slowdown in the United States affecting employment and insurance coverage have resulted in a smaller increase in drug utilization. In 2004, there should be a 10-12% increase in drug expenditures for outpatient settings, a 19-21% increase for clinics, and a 6-8% increase for hospitals. CONCLUSION: Drug expenditure growth should continue to outpace the growth in overall health care expenditures and the growth in the U.S. economy.

Ambulatory Care Facilities↗

Quantifying the association between habitual energy expenditure and blood pressure.

BACKGROUND: Previous studies have demonstrated an association between physical inactivity and hypertension, but the methods used to assess activity have been subjective and imprecise. Recently methods have become available allowing measurement of energy expenditure in free-living populations. Our aim was to employ these methods to assess the independent association between energy expenditure, cardio-respiratory fitness and blood pressure. METHODS: In a cross-sectional study of 775 people (45-70 years) participating in a continuing population-based cohort study, energy expenditure was assessed by 4 days of heart rate monitoring with individual calibration of the relationship between heart rate and energy expenditure, a method validated against doubly-labelled water and whole body calorimetry. Cardio-respiratory fitness was assessed in a sub-maximal test. To adjust for measurement error in the assessment of usual energy expenditure and fitness, 190 subjects repeated both tests on three further occasions at 4-monthly intervals. RESULTS: A highly significant linear trend in blood pressure was found across quintiles of the physical activity level, the ratio of total energy expenditure to basal metabolic rate. The differences in the mean systolic/diastolic blood pressure between the top and bottom quintile was 6.3/4.4 mmHg in men and 10.7/5.9 mmHg in women. These effects were independent of obesity and cardio-respiratory fitness. Correction for measurement error suggests that the true underlying relationship between usual energy expenditure and blood pressure is stronger still. CONCLUSIONS: These findings are compatible with a strong association between usual energy expenditure and blood pressure and support public health strategies aimed at increasing overall energy expenditure.

Aged↗

Energy expenditure in critically ill children.

OBJECTIVES: To measure energy expenditure in critically ill children and compare it with the energy expenditure predicted by recommended formulas, and relate the measured energy expenditure to nutritional and clinical indices. DESIGN: A prospective, clinical study. SETTING: Tertiary care pediatric intensive care unit in a university children's hospital. PATIENTS: A total of 37 patients with critical illness who were mechanically ventilated for > or =24 hrs were studied. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Chronic protein-energy malnutrition (CPEM) and acute protein-energy malnutrition were defined by the Waterlow's stages and fat and protein stores were classified as defined by Frisancho, Ryan, and Martinez. Severity of illness was assessed by the Pediatric Risk of Mortality Score, the Therapeutic Intervention Scoring System, and indices of organ failure. Oxygen consumption, carbon dioxide production, and the respiratory quotient were measured by indirect calorimetry, and energy expenditure (MEE) was calculated using the modified Weir formula. Resting energy expenditure (PBMR), predicted energy expenditure, and caloric intake were calculated using recommended formulas. A total of 77 measurements were made in 37 children. MEE was significantly lower than PBMR as estimated by all equations except the Talbot equations. MEE was significantly lower than predicted energy expenditure and the recommended daily allowances. On the first day, the MEE/PBMR ratio was <0.9 in 56.8%, 0.9-1.1 in 21.6%, and >1.1 in 21.6% of patients. MEE did not differ significantly among disease groups or between medical and surgical patients. There was no difference in MEE with or without neuromuscular blockade. MEE was lower in the presence of multiple organ system failure (MOSF) (1019 + 166 kcal/m2 without MOSF vs. 862 + 241 with MOSF; p = .025). A total of 21% had CPEM and 8.1% had acute protein-energy malnutrition. Multivariate stepwise regression analysis showed that the protein intake, midarm muscle area, midarm fat area, the use of vasoactive agents, and sedation correlated with MEE (p < .05). With CPEM, MEE was correlated to the severity of illness (p < .05). Patients at risk for protein stores depletion (midarm muscle areas 1 and 2) had a higher incidence of MOSF compared with nutritionally normal children (p < .05), whereas patients with fat stores depletion (midarm fat area 2) had a higher probability of death (50% vs. 6%, respectively). CONCLUSIONS: Recommended daily allowances and energy expenditure predicted by using a stress-related correction to the resting energy expenditure grossly overestimate MEE. MEE is close to PBMR and in many patients, it is lower than PBMR. MEE that is lower than PBMR is associated with a higher morbidity. Nutritional repletion should thus be based on MEE to avoid the problems of over- or underfeeding.

Acute Disease↗

Energy expenditure and body composition in growth hormone deficient adults on exogenous growth hormone.

OBJECTIVES: We assessed whether the obesity observed in growth hormone deficient adults is maintained by a reduction in energy expenditure. We studied the effects of exogenous growth hormone on energy expenditure and body composition. DESIGN: We performed an open study with growth hormone administered at 0.5 units per kilogram ideal body weight per week for 3 months. PATIENTS: Seven growth hormone deficient adults were studied. Thirty-eight healthy volunteers had their resting metabolic rate measured, with seven of them proceeding to have their total energy expenditure assessed. MEASUREMENTS: Total energy expenditure was measured by the doubly labelled water method (D2O18), resting metabolic rate by ventilated hood indirect calorimetry, and fat free mass from the dilution volume of oxygen-18. Body composition and components of energy expenditure were assessed before, at 2 weeks and at the end of the 3-month treatment period on exogenous growth hormone. RESULTS: Growth hormone deficient adults did not have a low total energy expenditure compared to healthy controls (13.12 vs 12.75 MJ/24 h) with only one patient expending less than 10 MJ/24 h. None had a resting metabolic rate lower than the 95% confidence limits of normality. The amount of energy expended on physical activity and thermogenesis was significant (6.54 MJ/24 h) and was similar to healthy controls (6.47 MJ/24 h). Resting metabolic rate increased by 15.9% after 14 days on exogenous growth hormone and was elevated 12.1% after 3 months treatment but the ratio to fat-free mass remained unaltered. Total energy expenditure increased by 13.4% after 14 days therapy. Fat-free mass increased significantly after 3 months treatment by (mean) 4.5 kg with no change in fat mass and no loss in body weight. CONCLUSIONS: Obesity maintenance in growth hormone deficient adults is not a consequence of reduced total energy expenditure or a reduced exercise energy output. There was also no evidence for an energy sparing mechanism. Energy expenditure was increased by exogenous growth hormone but was not associated with a loss in fat mass or body weight suggesting the need for dietetic advice for those already obese at the outset of therapy.

Adult↗

Prescription drug expenditures and population demographics.

OBJECTIVE: To provide detailed demographic profiles of prescription drug utilization and expenditures in order to isolate the impact of demographic change from other factors that affect drug expenditure trends. DATA SOURCES/STUDY SETTING: Demographic information and drug utilization data were extracted for virtually the entire British Columbia (BC) population of 1996 and 2002. All residents had public medical and hospital insurance; however their drug coverage resembled the mix of private and public insurance in the United States. STUDY DESIGN: A series of research variables were constructed to illustrate profiles of drug expenditures and drug utilization across 96 age/sex strata. DATA COLLECTION/EXTRACTION METHODS: Drug use and expenditure information was extracted from the BC PharmaNet, a computer network connecting all pharmacies in the province. PRINCIPAL FINDINGS: Per capita drug expenditures increased at an average annual rate of 10.8 percent between 1996 and 2002. Population aging explained 1.0 points of this annual rate of expenditure growth; the balance was attributable to rising age/sex-specific drug expenditures. CONCLUSIONS: Relatively little of the observed increase in drug expenditures in BC could be attributed to demographic change. Most of the expenditure increase stemmed from the age/sex-specific quantity and type of drugs purchased. The sustainability of drug spending therefore depends not on outside forces but on decisions made by policy makers, prescribers, and patients.

Adolescent↗

Daily energy expenditure in free-living heart failure patients.

We examined the hypothesis that weight loss in heart failure patients is associated with elevated daily energy expenditure. Twelve cachectic patients [age = 73 +/- 6 yr; weight loss = 15 +/- 6 kg; body mass index (BMI) = 21 +/- 5 kg/m2], 13 noncachectic patients (age = 67 +/- 5 yr; BMI = 27 +/- 5 kg/m2), and 50 healthy elderly controls (age = 69 +/- 6 yr; BMI = 26 +/- 4 kg/m2) were studied. Daily energy expenditure and it components were measured using doubly labeled water and indirect calorimetry and body composition by dual-energy X-ray absorptiometry. Fat mass and fat-free mass were lower (P < 0.05) in cachectic patients compared with noncachectic patients and healthy controls. Daily energy expenditure was lower (P < 0.05) in cachectic patients (1,870 +/- 347 kcal/day) compared with noncachectic patients (2,349 +/- 545 kcal/day) and healthy controls (2,543 +/- 449 kcal/day). Differences in daily energy expenditure were primarily due to lower (P < 0.05) physical activity energy expenditure in cachectic (269 +/- 307 kcal/day) and noncachectic patients (416 +/- 361 kcal/day) compared with healthy controls (728 +/- 374 kcal/day). A lower (P < 0.05) resting energy expenditure was also noted in cachectic patients (1,414 +/- 210 kcal/day) compared with noncachectic patients (1,698 +/- 252 kcal/day) and healthy controls (1,561 +/- 223 kcal/day). These findings show that daily energy expenditure is not higher, but significantly lower, in cachectic heart failure patients due to lower physical activity and resting energy expenditure. These results argue against the hypothesis that an abnormally elevated daily energy expenditure is associated with weight loss in heart failure.

Age Factors↗

Adjusted body weight, con: why adjust body weight in energy-expenditure calculations?

Evaluation of energy requirements of normal individuals and hospitalized patients is most often accomplished using an energy equation. Energy equations attempt to measure resting metabolic rate (RMR), the largest factor in total daily energy expenditure. Components of most energy equations include height, weight, age, and gender. These factors are related to energy expenditure; however, each factor has individual characteristics that affect energy expenditure. Body weight is a major factor in RMR and total daily energy expenditure. For obese individuals, estimation of energy expenditure may be a challenge due to the increased body weight. Therefore, some equations attempt to minimize the effect of body weight on energy expenditure assessment by adjusting the obese individual's body weight. Data do not support adjustment of body weight in normal individuals. In hospitalized patients, there are several equations that are used to estimate energy expenditure of obese patients, which include adjusting the body weight and modifying the overall energy requirements. Measurement of RMR can obviate the need for estimating energy expenditure. It is important to evaluate any energy-expenditure equation that is used to estimate energy needs in normal people and hospitalized patients before applying it to patient care.

Basal Metabolism↗

Resting energy expenditure in patients with alcoholic hepatitis.

Patients with alcoholic hepatitis are typically malnourished. A hypermetabolic state would explain, at least in part, the muscle wasting observed in these patients. However, data on hypermetabolism in liver disease are limited and conflicting. In this study, we evaluated measured energy expenditure (MEE) vs predicted energy expenditure (PEE), and MEE in relation to urinary creatinine excretion in 20 patients with moderate and severe alcoholic hepatitis, and 20 controls. Patients with alcoholic hepatitis had depressed creatinine height index (moderate 66%, severe 78%) demonstrating muscle depletion. Patients with alcoholic hepatitis also had depressed mean serum albumin concentrations, the moderate group 2.6 g/dl and the severe group 2.0 g/dl. The mean values for measured energy expenditure in moderate alcoholic hepatitis patients, severe alcoholic hepatitis patients, and the control group were: 1556 kcal, 1878 kcal, and 1943 kcal, respectively. The mean measured energy expenditures per g of creatinine for the same groups were: 1520 kcal, 1813 kcal, and 1043 kcal, respectively. The mean measured energy expenditure/predicted energy expenditure ratio was not increased in alcoholic hepatitis patients compared to controls. However, when related to urinary creatinine excretion, the alcoholic hepatitis patients had a mean measured energy expenditure that was 55% higher than controls. In conclusion, whereas the measured energy expenditure to predicted energy expenditure ratio was not elevated in alcoholic hepatitis patients compared to controls, the measured energy expenditure per gram of creatinine was significantly increased in alcoholic hepatitis patients, supporting the concept of alcoholic hepatitis as a hypermetabolic state.

Creatinine↗

Free does not mean affordable: maternity patient expenditures in a public hospital in Bangladesh.

OBJECTIVE: This study investigated a) the amount and types of out-of-pocket expenditures by patients for nominally free services in a large public hospital in Bangladesh, b) the factors influencing these expenses, and c) the impact of these expenses on household income. METHODS: Eighty-one maternity patients were interviewed during their hospitalization in the Dhaka Medical College Hospital. Patients were selected by quota sample to match the distribution of maternity patient categories in the hospital. Patients were interviewed with a semi-structured, in-depth questionnaire. RESULTS: All interviewees incurred substantial out-of-pocket expenditures for travel, hospital admission fees, medicine, tests, food, and tips. Only two of the expenditures, travel expenses and admission fees, were not supposed to be provided free of charge by the hospital. The median total per-patient expenditure was $65 (range $2-$350), equivalent to 7% (range 0.04%-225%) of annual household income. Half of all patients reported that their families had to borrow to pay for care at interest rates of 5%-30% per month. A third of these families reported selling jewelry, land or household items to moneylenders. The rural patients reported more difficulty in paying for care than the urban patients. Factors increasing the expenditures were duration of hospitalization, rural residence, and necessary (e.g. C-section, hysterectomy) and unnecessary (e.g. episiotomy) medical procedures. CONCLUSION: Free maternity services in Bangladesh impose large out-of-pocket expenditures on patients. Authorities could reduce the burden by reducing the duration of hospital stays, limiting use of medical procedures, eliminating tips, and moving routine services closer to potential users. Fee for service could reduce unofficial expenditures if the fee were lower than and replaced typical unofficial expenditures, otherwise adding service fees without reform of current hospital practices would lead to even more burdensome expenditures and inequities.

Journal Article↗

Energy expenditure and genotype of children with cystic fibrosis.

Increased energy expenditure, poor dietary intake, and fat malabsorption in patients with cystic fibrosis (CF) frequently lead to growth failure and malnutrition, which are associated with pulmonary failure and decreased survival. The study purpose was to understand better the energy expenditure and requirements in the mild pulmonary disease state in children. Resting and total energy expenditure were measured in 6- to 9-yr-old, pancreatic-insufficient children with CF (n = 25) and control children (n = 25) of similar age, gender, and weight. The effect of the most common genotype, homozygous delta F508, on energy expenditure was also investigated. Dietary intake, degree of fat malabsorption, body composition, physical activity, and clinical status were determined. The CF group had a 9% increase in resting energy expenditure, which was not related to genotype or severity of lung disease. Both CF genotype subgroups (delta F508 homozygous and all others) had a similar, modest resting energy expenditure increase. Total energy expenditure was increased by 12% in the entire CF group and by 23% in the delta F508 homozygous CF subgroup compared with controls. The total energy expenditure increase in delta F508 homozygous children may be related to increased voluntary physical activity, reflecting no activity reduction associated with lung disease, or to an unidentified genotype-related mechanism. The clinical implication is that a detailed physical activity assessment should be evaluated along with resting energy expenditure, either measured or estimated by equations, when daily energy needs are being determined for children with CF.

Anthropometry↗

Validation of a [13C]bicarbonate tracer technique to measure neonatal energy expenditure.

The use of a stable isotope-labeled [13C]bicarbonate infusion to measure energy expenditure is advantageous, as a complete collection of expired air is not required. This technique allows for facile measurements of energy expenditure in intubated neonates. The aim of the present study was to determine the accuracy of energy expenditure estimates in postsurgical neonates by using the [13C]bicarbonate method compared with the current standard, indirect calorimetry. Eight neonates who were receiving total parenteral nutrition [98 +/- 21 (SD) kcal x kg(-1) x d(-1); 3.1 +/- 0.7 (SD) protein g x kg(-1) x d(-1)] were studied on postoperative d 15.5 +/- 11.9. A primed continuous 3-h intravenous infusion of NaH13CO3 and indirect calorimetry were performed simultaneously. Energy expenditure was calculated separately from the Weir equation and from the dilution of 13CO2 in the breath in combination with the individual energy equivalents of CO2 from the diet. The rate of CO2 appearance and energy expenditure calculated from the bicarbonate method (0.725 +/- 0.021 mol x kg(-1) x d(-1); 89.5 +/- 2.5 kcal x kg(-1) x d(-1)) highly correlated (r = 0.94 and 0.98, respectively) with the CO2 excretion and energy expenditure determined by indirect calorimetry (0.489 +/- 0.016 mol x kg(-1) x d(-1); 60.2 +/- 2.0 kcal x kg(-1) x d(-1)) when analyzed nonproportionately to weight. Bland-Altman analysis demonstrated the 95% confidence interval to be +/- 8.2 kcal x kg(-1) x d(-1). Linear regression analysis revealed a highly statistically significant equation relating the two energy expenditures: Indircal (kcal/d) = -9.341 + [0.705 x Bicarb (dcal/d)]; p < 0.001, r2 = 96.4%. We conclude that energy expenditure in neonates can be accurately determined using the [13C]bicarbonate method and a regression equation. Therefore, the bicarbonate method may be useful for determining energy expenditure in neonates not readily accessible to indirect calorimetry, such as those being mechanically ventilated or on extracorporeal life support.

Bicarbonates↗