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SUMMARY Serial 24 hour balance studies of nitrogen and energy were carried out over 10 days in two groups of ventilator dependent preterm infants of comparable weight and gestational age. In one group (n= 10) a parenteral amino acid source (Vamin 9) was started within 24 hours of birth, and in the other group (n=11) it was not started until 72 hours. The feeding protocol was otherwise identical. The nitrogen intake (286 compared with 21 mg/kg/day), energy intake (188 compared with 151 kJ), and nitrogen retention (120 compared with -133 mg/kg/day), were all significantly higher during the first three days of life in the group in which the amino acid solution was started early. There were no differences by 7-10 days. The early introduction of amino acids improves the early nutritional state of sick preterm infants. Preterm infants, particularly if they are unwell, are likely to require nutrients and energy in the immediate transitional period after birth at rates at least similar to those available in the uterus. We aimed to find out if there was any increase in overall nitrogen retention and energy intake in sick infants of low birthweight who were ventilator dependent and who were given amino acids intravenously from birth. Patients and methodsVentilator dependent preterm infants of less than 30 weeks' gestation were entered sequentially on admission to the neonatal intensive care unit into one of two intravenous feeding regimen groups. Those in group E (early) were given intravenous glucose and nitrogen (as Vamin 9, KabiVitrum), within 24 hours of birth, while group L (late) initially received intravenous glucose alone, and nitrogen only after 72 hours of life. The nitrogen delivery rate in both groups was increased progressively over three days from 1 g/kg/day to a maximum of 3 g/kg/day. Intravenous fat (Intralipid, KabiVitrum) was introduced to both regimens at 7 days postnatal age. The infants continued to receive intravenous nutrition (based on standard clinical criteria) until oral feeding could safely be established.The feeding regimens of the two groups differed only in the time of introduction of amino acids. The vitamin intakes (for example, ascorbic acid) were similar in both groups. A computer based protocol was used for the prescription of parenteral solutions.The criteria for inclusion in the study were that the infants completed serial 24 hour balance studies of nitrogen and energy over the first 10 days of life, and that at least 75% of their nitrogen and energy was delivered intravenously. Thirty two infants were initially recruited: 17 in group E and 15 in group L.

Exercise tolerance of heart transplant patients is often limited. Central and peripheral factors have been proposed to explain such exercise limitation but, to date, the leading factors remain to be determined. We examined how a short-term endurance exercise training programme may improve exercise capacity after heart transplantation, and whether atrial natriuretic peptide (ANP) release may contribute to the beneficial effects of exercise training by minimizing ischaemia and/or cardiac and circulatory congestion through its vasodilatation and haemoconcentration properties. Seven heart transplant recipients performed a square-wave endurance exercise test before and after 6 weeks of supervised training, while monitoring haemodynamic parameters, ANP and catecholamine concentrations. After training, the maximal tolerated power and the total mechanical work load increased from 130.4 (SEM 6.5) to 150.0 (SEM 6.0) W (P < 0.05) and from 2.05 (SEM 0.1) to 3.58 (SEM 0.14) kJ.kg-1 (P < 0.001). Resting heart rate decreased from 100.0 (SEM 3.4) to 92.4 (SEM 3.5) beats.min-1 (P < 0.05) but resting and exercise induced increases in cardiac output, stroke volume, right atrial, pulmonary capillary wedge, systemic and pulmonary artery pressures were not significantly changed by training. Exercise-induced decrease of systemic vascular resistance was similar before and after training. After training arterio-venous differences in oxygen content were similar but maximal lactate concentrations decreased from 6.20 (SEM 0.55) to 4.88 (SEM 0.6) mmol.l-1 (P < 0.05) during exercise. Similarly, maximal exercise noradrenaline concentration tended to decrease from 2060 (SEM 327) to 1168 (SEM 227) pg.ml-1. A significant correlation was observed between lactate and catecholamines concentrations. The ANP concentration at rest and the exercise-induced ANP concentration did not change throughout the experiment [104.8 (SEM 13.1) pg.ml-1 vs 116.0 (SEM 13.5) pg.ml-1 and 200.0 (SEM 23.0) pg.ml-1 vs 206.5 (SEM 25.9) pg.ml-1, respectively]. The results of this study suggested that the significant improvement in exercise capacity observed after this short-term endurance training period may have arisen mainly through peripheral mechanisms, associated with the possible decrease in plasma catecholamine concentrations and reversal of muscle deconditioning and/or prednisone-induced myopathy.

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