Energy expenditure and plasma catecholamines in preterm infants with mild chronic lung disease.

The present study examined the hypothesis that the energy expenditure (EE) increases during the development of chronic lung disease (CLD) together with serum catecholamines as indicator of stress. Sixteen spontaneously breathing infants with gestational age of 28-34 weeks and birth weight of 870-1920 g were studied. Eight patients were at risk for CLD, eight were healthy controls. Measurements of indirect calorimetry were done weekly at postnatal ages of 2, 3, 4 and 5 weeks. Serum concentrations of adrenaline and noradrenaline were measured by means of a high-pressure liquid chromatography (HPLC) method. The eight CLD risk infants developed mild CLD with FiO(2) of 0.27-0.31 and characteristic radiographic signs at 28 days. Compared to the healthy controls, preterm infants with mild CLD showed increases in EE from week 3 (+67%) to week 5 (+46%). Plasma noradrenaline was increased significantly in the CLD infants when compared to the controls at week 3 (0.7+/-0.3 vs. 0.5+/-0.1 ng/ml; P<0.05) and more pronounced at week 4 (1.4+/-0.2 vs. 0.6+/-0.2 ng/ml; P<0.001) and 5 (1.1+/-0.3 vs. 0.7+/-0.2 ng/ml; P<0.01). Plasma adrenaline was markedly higher in the CLD risk group (mean overall value: 0.64+/-0.1 ng/ml) than in the controls (<0.1 ng/ml in all controls) from week 2 to 5. Regression analysis for the combined values of the infants with and without CLD showed that EE was directly correlated with heart rate, noradrenaline and adrenaline concentration at each of the four study weeks and with respiratory rate at weeks 2 and 3. Increased plasma catecholamine concentrations in preterm infants with CLD suggest that these infants experienced marked stress during the early stages of the disease. Increased EE may in part be a result of this stress.