Energy metabolism of premature infants

Energy metabolism studies have been made in 82 periods of observation upon 21 prematurely born infants including those previously reported. 1 Both the oxygen and carbon dioxide, and thus the R. Q., were detemined for each separate period and heat calculated from the oxygen consumption. Temperature within chamber was usually kept between 24° C. and 28° C. Infant was fed (amount of feeding determined by weighing before and after), placed in the chamber and a preliminary period run to allow a lapse of 30 minutes between time of feeding and the beginning of the first period. An average minimal heat production per sq. m. per hour (Lissauer formula) of 25.0 calories on infants over 24 hours of age was obtained as compared with 26.75 calories obtained by Benedict and Talbot 1 for normals from 2 to 8 days of age. These observers found a rather constant heat production from second to seventh day, the average of all basal periods being 27.87 cal. per sq. m. per hr. as compared with 25.72 calories for our prematures.

In comparing maximum with minimum heat values for each infant an average of 44.5 per cent. increase was obtained. Percentages varied from 5.7 with slight restlessness to 88.77 with hard crying 36 minutes (3/4 the period). Comparing the increases obtained in succeeding periods of the same observation in which all the factors, except the activity, were the same, an average of 16.5 per cent. was obtained. Increases varied from 2.5 per cent. with very slight restlessness to 40.5 per cent. with crying 16 minutes of a 33-minute period. Minimal metabolism in children of comparable ages averages 31 cal. per sq. m. per hr. after feedings of from 60 to 84 grams breast milk and 24 cal. after feedings of from 25 to 35 grams.