MICROCALORIMETRIC DETERMINATION OF BLOOD HEAT OUTPUT IN HUMAN NEONATES

Based on earlier results on a body size relationship of blood heat out put in different mammalian species, an intra-specific comparison of bl ood heat output in human neonates and adults was made. To avoid taking additional blood samples from neonates, a resuspension technique was developed, allowing the use of material left over from clinical routin e sampling. In 13 adult volunteers, microcalorimetric heat output ((x) over bar +/- SEM) was 48.1 +/- 0.8 mu W (ml(blood))(-1) or 105.6 +/- 2.2 mu W (ml(cells))(-1) in the whole blood and 47.3 +/- 1.6 mu W (ml( susp).)(-1) or 104.0 +/- 3.3 mu W (ml(cells))(-1) in the resuspended s amples, respectively, proving that the resuspension procedure did not alter the thermal power values. Using this technique on blood samples from 38 neonates in their first week of life, a heat output of 77.2 +/ - 3.1 mu W (ml(susp.))(-1) or 151.8 +/- 5.9 mu W (ml(cells))(-1) was f ound. This is significantly higher than in adults, and fits the body s ize relationship of blood heat output previously described for differe nt mammalian species.