Tissue carnitine reserves of newborn infants.

This study assessed the tissue reserves of carnitine at birth in a group of neonates (n = 22) of varying gestational age dying within 24 h of birth, prior to possible changes in carnitine status induced by postnatal intervention. Tissue carnitine concentration was highest in the muscle in each infant. The mean (+/- SD) muscle carnitine concentration of 8.4 +/- 3.6 nmol/mg noncollagen protein (NCP) in very immature infants (less than or equal to 1000 g birth weight) was significantly lower than the corresponding mean (+/- SD) values of 14.0 +/- 3.2 nmol/mg NCP in larger preterm infants (1001-2500 g; P less than 0.01) and 19.4 +/- 2.6 nmol/mg NCP in term infants (greater than or equal to 2501 g; P less than 0.001). Muscle carnitine concentration correlated positively with gestational age (r = 0.832; P less than 0.001) and with body dimensions. Liver and heart carnitine concentrations did not correlate significantly with gestation or body dimensions. The mean (+/- SD) liver carnitine concentration for all the neonates as a group was 4.1 +/- 1.5 nmol/mg NCP. The mean (+/- SD) heart carnitine concentration was 4.7 +/- 1.3 nmol/mg NCP. In comparison to adult controls, tissue carnitine concentrations were markedly lower in neonates, particularly in immature newborns. These data suggest that newborn infants, especially premature babies, are born with limited tissue reserves of carnitine and are therefore at an increased risk for developing carnitine deficiency and its adverse effects in the postnatal period, particularly if maintained on carnitine-free intravenous nutrition for prolonged periods of time.