Acute alterations in energy metabolism and body composition post trauma have been well documented. However, information on these alterations during the rehabilitation (or long term) phase does not exist. This lack of important information within the literature becomes apparent when working clinically with these patients. It is for this reason that several investigations were performed on children with an acquired brain injury whilst attending a rehabilitation program.
This paper is divided into four separate studies:
Hypothesis - Alterations in body composition exist in children with acquired brain injury attending a rehabilitation program.
Methods - Anthropometric measurements and assessment of body composition (total body potassium [TBK]- a measure of body cell
mass) was obtained from nineteen children with acquired brain injury (9 males, 10 females, mean age 9.1 ±4.3 years (mean ±SD, range 1.2-15.1 years) on referral to rehabilitation after the acute stage of injury (mean 38.1 days post injury).
Results - In 19 children with acquired brain injury, the mean percentage of expected TBK for height was 84.4± 15%, significantly below the clinically acceptable level for body cell mass (90% of expected). Using the anthropometric definition (measures of weight below the fifth percentile and/or weight two standard deviations below the mean), only 1/19 was undernourished, whereas 12/19 had poor nutritional status using body composition (TBK for height <90% of expected for age and gender), (χ2=7.58, p=0.006).
Hypothesis - Alterations exist in energy
expenditure of children with acquired brain injury.
Methods - Measurement of resting energy expenditure by indirect calorimetry was performed on 21 different children with acquired brain injury of mean age 10.2±3.8 years (mean ± SD). Measurement of total body potassium was also performed on these subjects.
Results - Measured resting energy expenditure values for the 21 subjects were widely distributed, ranging from 52.3% to 156.4% of predicted values using Schofield weight, Schofield weight and height and World Health Organization equations, yet the mean percentage of predicted using Schofield weight, Schofield weight and height and World Health Organisation predictive equations were 97.5%, 97.4% and 98.6% respectively. Mean ± SD percentage of expected total body potassium for weight, height and age for children with acquired brain injury were 85.1±15.5%,
89.1±14.1% and 86.9±15.9%, thus, all showed significant depletion.
Hypothesis - Cosmed K4b2 is a valid tool for measuring energy expenditure at rest.
Method - Measurements of resting energy expenditure were taken on nine adult subjects (4 male, 5 female) in consecutive sessions using both Cosmed K4b2 and Deltatrac II™ in an attempt to validate the use of the Cosmed K4b2 in measuring restmg energy expenditure. Resting energy expenditure data from both devices were then compared with values obtained ftom predictive equations.
Results - Bland and Altman analysis reported a mean bias ± SD for the four variables, resting energy expenditure, respiratory quotient, volume of carbon dioxide and volume of oxygen between data obtained fi-om
Cosmed K4 b2 and Deltatrac IITM metabolic cart of 268±702kcal/day, -0.0±0.2, 26.4±118.2ml/min and 51.6±126.5ml/min respectively. Corresponding limits of agreement for the same four variables were all large. Also, Bland and Altman analysis revealed a larger mean bias ± SD between predicted resting energy expenditure and measured resting energy expenditure using Cosmed K4 b2 data (- 194±603kcal/day) than using Deltatrac™ metabolic cart data (73±197kcal/day).
Hypothesis - Children with acquired brain injury have altered energy metabolism causing altered energy cost during activity when compared with control children.
Methods - Measurement of resting energy expenditure and physical activity cost during a 3 minute walk and 3 minute
run (via Cosmed K4b2) and measurement of body composition (using bioelectrical impedance analysis) was also performed on 15 children with an acquired brain injury of mean ± SD age 12.13 + 3.82 years and 67 control children of mean ± SD age 9.15 ± 1.63 years recruited from local schools.
Results - In comparison with 15 children with acquired brain injury and normal controls, subjects with acquired brain injury were shorter (mean height z-score ± SD was -0.03 ± 1.1) and heavier (mean weight z-score ± SD was 0.75 ±1.1) than normal controls (mean height z-score ± SD being 0.3 ± 0.9, mean weight z-score ± SD being 0.3 ± 1.1). Mean energy cost and physical activity ratios during walk and run for both groups were determined. Walking cost was not significantly different between both groups. However, a
significant difference was found between the two groups for the number of steps taken during the run (p<0.05) with mean number of steps for children with acquired brain injury and normal controls during a 3 minute run being 299 and 477 respectively. Mean percentage body fat ± SD for children with acquired brain injury and normal controls was 47.3 ± 7.8 % and 39.5 ± 6.1 % respectively.
The data revealed a significant depletion in the metabolically active body cell mass in the presence of normal anthropometry, suggestive of significant muscle wasting. During rehabilitation, using predictive equations to estimate resting energy expenditure in this group revealed a small bias on average but very large bias at the individual level. Children with acquired brain injury had altered resting energy expenditure and body composition.
Compared to normal controls,
physical activity cost in children with acquired brain injury is slightly less than for normal controls. Body fat was higher in children with acquired brain injury than for normal controls. However, it is important to note that 'a comfortable pace' for children with acquired brain injury was significantly slower than normal controls (revealed by total number of steps taken). Hence, this study revealed that children following acquired brain injury expend less energy to walk and run at their own desirable, comfortable pace than normal controls reported in the literature, however, when controlled for velocity or distance, children with acquired brain injury exert much greater energy per activity.
Lastly, variability between the two devices was very high and a degree of measurement error was detected. Data from the Cosmed K4 b2 provided variable results on comparison with predicted values, thus, would seem an invalid device for measuring
Implications for Nutritional Practice
Children with acquired brain injury during rehabilitation have reduced body cell mass, increased body fat and decreased energy expenditure both at rest and during activity (due to compensatory techniques). Therefore, in the absence of body composition and energy expenditure measurement tools, predictive equations will significantly overestimate energy requirements. Thus, potentially further increasing body fat/body cell mass ratio. This in turn may negatively effect major factors such as mobility, self esteem and increase rehabilitation time and impact the shared financial burden for both the patient/families and medical institution.
Therefore, these studies have important pathophysiological and clinical implications in the rehabilitation of children following major head trauma.