Is the raised metabolic rate of the small for gestation infant due to his relatively large brain size
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1Faculty of Medicine and Health Sciences, U.A.E. University, Al Ain, U.A.E.
Insights
Small-for-gestational age (SGA) premature infants have a higher metabolic rate (MR) per kilogram of body weight compared to appropriate-for-gestational age (AGA) infants. This difference is largely explained by their proportionally larger brain size.
Area of Science:
- Neonatal physiology
- Developmental pediatrics
- Metabolic research
Background:
- Premature infants exhibit varying metabolic rates.
- Small-for-gestational age (SGA) infants present unique physiological challenges.
- Understanding metabolic differences in premature infants is crucial for optimal care.
Purpose of the Study:
- To compare oxygen consumption and metabolic rates between SGA and appropriate-for-gestational age (AGA) premature infants.
- To investigate the influence of brain size on metabolic rate calculations in these infant groups.
- To determine the most accurate reference for metabolic rate in SGA and AGA infants.
Main Methods:
- Measured oxygen consumption in SGA and AGA premature infants (ages 4-25 days).
- Calculated brain weight as a percentage of body weight using head circumference.
- Determined metabolic rate (MR) using various references: kcal/cm head circumference, kcal/g brain weight, and kcal/kg body weight.
Main Results:
- SGA infants had a significantly higher brain weight percentage compared to AGA infants.
- Metabolic rate per kilogram of body weight was significantly higher in SGA infants.
- No significant difference in metabolic rate was found when expressed per centimeter of head circumference or per gram of brain weight.
Conclusions:
- The apparently higher metabolic rate in SGA infants is largely attributable to their relatively larger brain size.
- Using head circumference as a reference minimizes the observed metabolic rate differences between SGA and AGA infants.
- Brain size is a critical factor to consider when evaluating metabolic rates in neonatal populations.
Abstract:
Oxygen consumption at different stages of vigilance, and for the whole 24 h, was measured in 13 small-for-gestational age (SGA) and 16 appropriate-for-age (AGA) premature infants at ages of 4-25 days. Brain weight was calculated from head circumference measurements and expressed as percentage of body weight and was found to be significantly higher in SGA infants than AGA ones (14% +/- 2.1 (S.D.) in the SGA and 12.3% +/- 1.5 (S.D.) in the AGA infants). Metabolic rate (MR) was calculated and expressed as kcal/centimetre head circumference, kcal/g brain wt. and kcal/kg body wt. Whereas MR expressed in kg body wt. was significantly higher in SGA infants than in AGA ones, no difference could be detected in the values when MR was expressed as kcal/cm head circumference, or MR/g brain wt. The difference that exists in the metabolic rates between SGA and AGA infants can be minimised by using head circumference as a reference. Therefore, the apparently high MR found in SGA infants in the neonatal period can be attributed, in a major way, to their relatively large brain size.